Northstar1989

FreeThinker, Also, I know I've been throwing out a lot of information at once, but we still need to implement the code I presented in this post and the one above it to fix the ISRU refinery tanks so they are insulated and customizable with RealFuels, and so the harvestable (trace) Oxygen resource in Duna's atmosphere becomes LOX instead of "Oxidizer"... Here's the code that needs to be added to the RealFuelsFix file again, for your convenience. Note that the Duna atmospheric resource definition MM patch needs to be buried at the same layer as the other atmospheric resource definition patches, or needs its own header (which is NOT included here) or else it won't work... //Make ISRU refinery tanks insulated and modular @PART[FNRefinery]:FOR[RealFuels] { MODULE { name = ModuleFuelTanks volume = 1750 type = Cryogenic } } @PART[FNInlineRefinery]:FOR[RealFuels] { MODULE { name = ModuleFuelTanks volume = 1750 type = Cryogenic } } @PART[FNInlineRefineryLarge]:FOR[RealFuels] { MODULE { name = ModuleFuelTanks volume = 11000 type = Cryogenic } } See my earlier post for where in the file this second piece of code goes... @ATMOSPHERIC_RESOURCE_DEFINITION[DunaOxygen] { resourceName = LqdOxygen } Also, I mentioned a couple ISRU processes to turn CO2 into O2 and produce either CO or solid Carbon as a waste-product... We eventually want to get those implemented, as well as the ability to use the CO2 resource for the Sabatier Process (if that was implemented, it doesn't show up in the Changelog, at least) and some of the other ISRU processes (like Hydrogen Peroxide production from Hydrogen and Oxygen instead of Oxygen and Water) that I mentioned before... Regards, Northstar

Also, EMPeror raised an interesting point: 3000 Celsisus is 3273.15 Kelvin, which is about the temperature our Molten Salt Reactors operate at (3200 K). With 50% splitting of water into 1.5 particles each (2 H2O --> 2 H2 + O2) you get a 25% increase in Exhaust Pressure- and thus, Thrust. However the MSR's are a *but* colder than that, so only a 20-24% increase in Thrust when using Water is probably in order... This does get to the heart of a major issue, though- several fuels we currently use break down into multiple particles when heated to the temperatures of a Thermal Rocket. Ammonia will do it for pretty much any of our Thermal Rockets (Microwave Thermal, Nuclear Fission Thermal, Fusion Thermal, etc.), and will double your Thrust when it does... (as you double the moles of gas and thus Exhaust Pressure) But Water requires such a high enough temperature that you need something at least 3200 K (the temperature of our Molten Salt Reactors, but not the optimal temp. of our Pebble Bed Reactors- which operate optimally at 3000 K) to do it to just 50% of the Water- which means it won't affect our Microwave Thermal Rockets at all (too cold), and won't affect our Pebble Bed Reactors unless they're running at sub-optimal temperature with the Mk2 version (since you implemented a Mk1 "experimental" version that operates at the same temperatures as Fractal_UK's original part...) And, when Water is breaking down 100% instead of only half (such as at the temperatures of a Fusion or Antimatter Reactor) Thrust will increase 50% instead of 25%... A side note: LOX-augmentation normally occurs in the NOZZLE of a nuclear thermal rocket, after the gasses have already greatly cooled off due to their expansion in the nozzle (exhaust gasses lose pressure and temperature, but gain velocity, in a rocket nozzle). So, you can still have LOX-augmentation in the nozzle even if the reactor is hot enough to break water into LH2 + LOX... Oh and Methane? It will start to gook up the reactor with graphite-formation through pyrolysis (CH4 --> C (solid) + 2 H2) if it gets hot enough (I have NO IDEA what temperatures would have to be reached for this to happen- although the fusion and antimatter reactors would certainly get hot enough...), although the increase in Exhaust Pressure from the doubling of moles of gas will also *temporarily* double your thrust until the reactor-gooking catches up with you... I have *no idea* how to implement a temperature-dependent Thrust increase like this- although I might try looking at the Particle Bed Reactor code for some clues, since it already allows players to increase its temperature by decreasing WasteHeat removal, and has to change its Thrust/MW and ISP as a result of its variable exhaust temperature... Regards, Northstar

Actually, yes. Considering our Molten Salt Reactors operate at about that temperature (and Particle Bed Reactors when at sub-optimal temperature), and a 50% dissociation rate would improve Thrust by approximately 25% due to the dissociation of each water molecule into 1.5 Hydrogen/Oxygen molecules (2 H2O --> 2 H2 + O2)... I would say, it's worth implementing for the Molten Salt Reactors (which operate at this temperature) but not the Particle Bed Reactors- the MSR's could already use a bit of a buff compared to the PBR's anyways! Regards, Northstar

Thanks for catching that- otherwise it would have created some headaches for me, wondering what happened to the name-fix I wrote up before (and had already been implemented...) Affirmative. All these effects are both desired and realistic. The fuel-consumption would be increased 5-fold as well. It seems nothing in this world is without a cost or drawback... I don't think the Fusion reactors *should* be buffed, as they were currently producing far too much surplus ThermalPower beyond what is needed to maintain the magnetic confinement fields compared to what we can expect form Fusion any time in the next 200 years in real life... In fact, I'm not sure you really will like what I think should be done to the Fusion reactors, but I'll tell you anyways... Technically I *do* think they should have their ThermalPower increased- their ThermalPower production should be increased, and the electrical power required to maintain the magnetic confinement should be increased by almost the same amount- which would effectively *nerf* the Fusion reactors, as they would produce the less surplus ThermalPower than before (because there is inefficiency in converting ThermalPower into electrical power), but now require even more radiator mass to deal with all the WasteHeat produced... This would make for a *more realistic* implementation of Fusion Reactors- and would make having an upgraded electrical generator a practical necessity in order to get any useful amount of surplus power out of them (due to the need to convert very large amounts of ThermalPower into electrical power just to maintain the magnetic confinement field- which is what would limit their utility in real life more than anything else... All that electrical power production, and very high total ThermalPower production that mostly needs to be cycled back into electrical power, results in the need for *VERY* large radiators to get much use out of a Fusion reactor in space...) Fusion reactors *do* need a large nerf if you're aiming for realism. If you ask me, we should apply the same 5-6x increase in ThermalPower production, but increase their magnetic confinement electrical power requirements roughly 50-fold from what they are now (a measly 5 MW for a small reactor). THEN you would start to see a more realistic implementation of fusion power... Well, we already have good data on what the ISPmultiplier should be from that Atomic Rockets chart. It just seems Fractal_UK already had the correct #'s for this in the first place... What did you mean about removing the Thrustmultiplier, though? I hope you didn't remove the Thrustmultiplier from the Thermal Rockets entirely- the *original* performance way back when (in Fractal_UK's original version) was something like 0.1 kN/MW, whereas we want 0.2 kN/MW based on the Atomic Rockets figures... Ultimately, we had the right numbers for Thrust and ISP (for Hydrogen)- we just need to adjust the Thrust/MW, reactor mass (still too heavy, but we already knew that...) and ThermalPower production to match... As for Ammonia, Water, etc. and the other fuel-modes, once we have the correct Thrust/MW implemented for Hydrogen and the correct ISPmultiplier for all the other fuels, Fractal_UK's coding for determining Thrust should be more than capable of figuring out the correct Thrust/MW for all the other fuels. The only thing we will need to adjust is for fuels that undergo a chemical reaction in addition to the heating- such as LOX-augmentation of Hydrogen or Methane (which, for Hydrogen LOX-augmentation, approximately triples the Thrust *relative to Hydrogen alone*) or the breakdown of Ammonia into N2 and H2 (2 NH3 --> N2 + 3 H3) which according to the Ideal Gas LAW (PV = nRT) should approximately double the Exhaust Pressure (and thus the Thrust/MW) of Ammonia for its Exhaust Velocity... Be careful that the last one (Ammonia) is implemented properly- because what it should look like is doubling both the Thrust and fuel-consumption from the coding side of things... (i.e. the ISP remains unchanged) I never object to asking for help, though. Feel free to go and do that if you want! Regards, Northstar P.S. I'm aware that increase the reactor's ThermalPower production would, indirectly, also improve the viability of Nuclear-Electric propulsion (using a nuclear reactor to power plasma thrusters). This is both realistic and desired- nothing about our Plasma Thrust ISP or Thrust/MW was based on the Thermal Rockets. In fact, the only changes we've made to them so far was to actualize a realistic relationship between Vacuum ISP and Sea-Level ISP for them, and to implement new fuel-modes for them such as CO2 and N2...

The calculation was a quick-and-dirty derivation (using some of the equations I've already discussed) from the known figure of 0.3 kN/MW at 850 seconds ISP for the NERVA reactor, as found on the Wikipedia page on NTR's: http://en.wikipedia.org/wiki/Nuclear_thermal_rocket Atomic Rockets gives us something to work off of, and check our assumptions against. And since they are close enough for reason to the real figures, if you want to balance against the lower TWR listed on Atomic Rockets, that's OK with me... It would actually still require a slight buff of our Thrust/ton to match the figure from Atomic Rockets- I don't think we should shrug off the difference, since the figures on Atomic Rockets are already quite conservative here- but seek to match those numbers as closely as possible... It seems the figures on Atomic Rockets are decent. They may not precisely match up with any figures I know of (for instance, the Thrust figure they give for a Particle Bed Reactor is somewhat less even than the Timberwind 45, and their TWR is closer to 20 rather than the known figure of 30 for a Timberwind Particle Bed Reactor... A Timberwind 75 produced 294.2 kN/ton, at a mass of 2.5 tons according to Wikipedia and Encyclopedia Astronautica...) So far, our TWR has been lower because we did not reduce mass to 1/4th the Timberwind 75 we were balancing against. We got a bit closer with the new version you created for TweakScale, but the accurate mass for a reactor of that size would be only 0.625 tons... You justified the mass-difference with shielding requirements, etc., even though I am fairly sure Timberwind 75 already included these in its original mass figure... The Particle Bed Reactor listed on Atomic Rockets produces (333.617 / 1590) = 0.2098 kN/MW, which is *almost exactly* the figure I got from my quick-and-dirty calculation of what your Thrust/MW *should* be before... Of course, their figure is assuming an ISP of 966.5 seconds, whereas mine assumes an ISP of 1000 seconds... (this is before the 15% increase to Thrust/MW and Vacuum ISP we assume from having a very large nozzle...) As I understand it, the centrifugal action is actually driven by the LH2 flow through the reactor. There's no mention of an external power source or electric generator/motor combination *anywhere* in any of the articles of particle bed reactors I could find, and there are some statements in the design documents of Timberwind that led me to believe something along those lines might be occurring (I didn't mention it before because it should have no bearing on Thrust/Mw or ISP performance...) There is motion that occurs, but an object in motion remains in motion unless acted on by an outside force- which would only be friction in this case (which would just convert that kinetic energy back into Thermal Energy- precisely the thing we want out of the reactor in the first place!) OK, so anyways, this gives us some good figures on the Thrust/MW to use for Hydrogen (their figures are conservative enough I believe we should stick to an Exhaust velocity of 1000 seconds, and their figure for Exhaust Velocity seems to assume a rather smaller nozzle- so I think we should stick with the extra 15% Vacuum ISP and Thrust/MW on top of that for the large nozzles we've been using...) Based on the figures from Atomic Rockets, I would suggest an even more conservative 6x increase in ThermalPower and 1/6th decrease in Thrust/MW. The Thrust of our NTR's shouldn't change, just the amounts of ThermalPower (and thus uranium-consumption and WasteHeat generation) that go into generating that performance... I am *still* a fan of reducing the reactor mass to get a more realistic Thrust/ton (unless you want to increase the Thrust production without increasing reactor mass, and stick with the current figure). Our current figures is, as I've repeatedly stated, too low- and leads to an even lower TWR than the one stated on Atomic Rockets, which is itself a very conservative number... Also, the Thrust/MW of our Thermal Turbojets needs to be decreased by the same factor (5-6x) as that of our Thermal Rockets. Note, though, that this is *AFTER* the 1.109-fold increase in Thrust/MW, for a *net* decrease to only .2218 - .185 times the original Thrust/MW as implemented by Fractal_UK (which, with a 5-6x increase in our current ThermalPower from reactors, which is built on an already-significant increase to reach the 187.5 MW number for a Sethlans we moved to before, *still* equates to a significantly higher overall Thrust for a Thermal Turbojet attached to the same reactor than in the original release... So, a *nerf* to the Thrust/MW of the original TTJ is necessary to still obtain realistic performance with a much higher ThermalPower production by all reactors...) Regards, Northstar

Indeed the turbopump WILL have to be huge. So, we finally agree on something? I never said Thermal Turbojets require a fuel pump, though- because they don't. However I did imply that they save significantly on mass by not having one. I'd like to see your data on just how "light" a high-thrust jet engine fuel-pump is, though... Between not having a fuel pump, not having a combustion chamber, having a much lighter compressor for the same Thrust, and not having any fan blades, you end up with a much better TWR at high-speed/high-altitude flight. Thermal Turbojets are turbojets, not turbofans- they work best at high speeds an altitudes. Compared to a chemical turbofan, they are (at least slightly) lighter, they can operate faster/higher (the reduced compression-ratio means cooler airflow inside the engine for a given speed, and turbojets work better at high speeds and altitudes than turbofans anyways...) and they require absolutely no fuel... The last of which is a very big deal- because the SR-71 had 5.4 tons of weight in engines, but many times that weight in fuel it had to carry onboard. Not needing to carry any fuel means you get a lighter wingload (the higher ISP of the rocket mode means you get a lighter wingload still compared to a chemical spaceplane). The lighter wing-load can be either kept, or exchanged for smaller (and more highly-swept, lower-drag) wings. Either one will benefit your ascent to orbit. As for the low density of Hydrogen, I don't think you get, *it really doesn't matter*. Even if you can only achieve a 1:10 mass ratio for Hydrogen fuel-tanks, you can only achieve a 1:50 ratio for Oxygen or Kerosene fuel-tanks (your figure of 1:100 mass-ratio was *highly* unrealistic). The vast majority of your plane's mass will be in fuel, wings, engines, and payload either way- not in the fuel tanks. Even if you need 5x more fuel-tank mass, that doesn't significantly cut into the total mass-savings you get from using Hydrogen instead of Hydro/LOX or Kero/LOX... And, as I stated repeatedly, you don't want Hydrogen the whole way up- you want, at the very least, a Methane "kicker" to decrease the total size of your spaceplane. Methane is actually denser that Hydro/LOX (due to the very low density of the LH2-component of the mix). Methane also works as a potential coolant for pre-coolers (it is still cold enough to make a useful heat-sink), but it is denser than Hydrogen, and has a greater temperature-difference between its melting point and boiling point, meaning you can store it *just above* its melting-point, and heat it all the way until it starts to vaporize, for a potential reduction in the total propellant-mass consumed by the pre-coolers (you can also still use the Methane in ramjets, just like Hydrogen...) We're not still talking about microwave thrust-augmentation of a SABRE-like stage, so please let go of that. If we *WERE*, though, you've got it wrong way around- you don't combust the Hydrogen and *then* heat the exhaust gasses, you pre-heat air (with Microwaves) and *then* combust it with Hydroge- to achieve even more thrust production than with either a SABRE or a Microwave Thermal Turbojet alone. I'm still not sure it would make sense from a mass-standpoint though, as you would essentially be building the entire mass of a SABRE engine onto the rear of a Thermal Turbojet for a relatively minor increase in Thrust- which is why I said it was ultimately probably a silly idea... With an plane, the SRB isn't going to get you any higher/faster than a Microwave Thermal Turbojet if you take off horizontally, and is going to create HUGE safety-issues. If you're talking about a rocket on top of an SRB, then you're talking about an entirely different beast altogether- and *not* one that is superior to a plane (because, Lift/Drag works *greatly* to your advantage, even when under rocket-propulsion...) No, you don't. You're actually starting to sound a bit like one of those KSP players who launches "straight up then over"... An *efficient* ascent focuses on horizontal velocity first and foremost- vertical ascent is only a secondary-priority to make sure you're staying in thin enough atmosphere that you don't end up traveling faster than your terminal velocity for a given speed/altitude (which is, in theory, the optimal speed to ascend at), or reach a dynamic pressure that becomes unmanageable... An *efficient* spaceplane ascent spends as much time inside the upper atmosphere as possible, relying on wings to hold it up while its entire engine power goes into building horizontal velocity. This holds true in Kerbal Space Program (with FAR installed), and it holds true in real life. You will get to orbit *faster* this way than if you push yourself into a suborbital trajectory, and end up having to use *Thrust* to hold your spaceplane up... Nope. The fuel-requirement is *less* this way. I can't be bothered to try further proving that to you- if you don't understand that, you don't understand how spaceplanes work at all in the first place... You *are* correct in that the atmospheric heating is a significant problem. But not *nearly* so much as you think. Because lift is proportional to velocity^2, you can fly at extremely high altitudes where atmospheric heating poses a *much* smaller issue than during re-entry (the only parts of your vessel that will have a really hard time with it at this altitudes are the leading-edges of your wings and the nose- both of which require some sort of active-cooling or use of thermal tiles for a spaceplane ascent that spends an extended period of time in-atmosphere under rocket propulsion...) I think you have some mis-conceptions about how supersonic/hypersonic flight really works. The wave drag of the wing is much, much, much more important than induced drag at supersonic (and even more so, hypersonic) speeds. Therefore, you want wings with a very high sweep, even if this comes at the expense of aspect ratio, in order to decrease the length of the shock wave at supersonic speeds... How many supersonic aircraft design have you EVER seen with high aspect-ratio wings? The Concorde is an example of a good wing shape for supersonic flight. The ASH 31 is an example of a *terrible* wing-shape for supersonic flight... When you're optimizing for low wave-drag, having a *long* fuselage with a low density is ideal, because it allows you to build in short, highly-swept wings. This is *precisely* what using Hydrogen as your rocket propellant provides. It also so happens that use of Thermal Turbojets and Hydrogen-propelled Thermal Rockets will bring down your wing-loading, because the *only* fuel you have to carry is Hydrogen for the rocket portion of your ascent. And if your spaceplane is 80% fuel by mass, then the Specific Impulse of that fuel is *much* more important than the density of that fuel to reducing total fuel-weight... Of course, you probably still want some Methane onboard- which will increase your wing-loading a bit, but is still efficient enough to be useful for its superior thrust and fuel-density... I never said that the turbopump was light. In fact, I *explicitly states* that it was heavy, when I said it was "by far the heaviest part of the Thermal Rocket". It's a cost in mass you have to bear for the higher ISP of Hydrogen... Because an Ariane 5, or an SS-SRB, or any of the other boosters you're talking about, they *AREN'T* cheap. They're quite expensive. If they were in fact cheap, there would be no reason to discuss needing to use Microwave Thermal Rocketry in the first place, because we would just load our 5000 Mars colonists up on our colossal expendable boosters and send them off, no problem. But the fact that in reality it costs $10,000/kg to get anything to orbit bears witness to the fact that a better way is needed. A plane is useful because of Lift/Drag. Because of a spaceplane ascent's advantages- spend a long period of time building up horizontal velocity at high altitude before finally going ballistic and kicking your apoapsis outside the atmosphere. It's better to use Lift than to use Thrust to hold yourself up- especially when you have to pay dearly for every kN of Thrust with a Microwave Thermal Spaceplane/Rocket (the advantage is very high ISP, and thus the ability to construct spaceplanes or very high payload-fraction rockets- *not* a low cost/kN of Microwave Thermal propulsion...) That was why I said you were wrong. All you proved is that you finally learned the proper math to calculate things. That doesn't mean any of the numbers you gave before were correct... You haven't even repeated the calculations for your old #'s, nevertheless addressed the fact that your starting-point was wrong... You are indeed correct, my figure for the Thrust/MW of the Timberwind was incorrect. I assumed that the "75" in "Timberwind 75" (which would have produced 735.5 kN of Thrust at 1000 seconds) was 750 MW. Going back, it looks like the actual ThermalPower was closer to 3750 MW (a bit less)- corrected, and using the NERVA numbers as a reference (0.3 kN/MW at 2600 K), the Thrust/MW only comes out to around 0.2 kN/MW at 3000K. Or about 0.5 kN/MW at a little over 2000 K... So, your power-estimates had a 2x factor too high built into them, by your own admission. Mine has a 0.5x factor built into them- and were just as far off, but in the wrong direction... Using the new #'s, the cost of a Microwave Thermal Rocket that uses LH2 the whole way up and achievers 0.5 kN/MW is over $3 billion- which is more than the lifetime cost of the DeltaIV program. I'll admit when I'm wrong- a pure Hydrogen Microwave Thermal Rocket doesn't make economic sense *yet* (the cost of Microwave Transmitters continues to come down). However, if you use heavier fuels like Methane and Hydro/LOX (in a LOX-augmented Thermal Rocket) in the lower stages, you can still get a rocket that is close to cost-competitive for the same payload-capacity... All this assumes that it is optimal to try and match the payload-capacity of a DeltaIV rocket, however. The numbers say otherwise. It would be *MUCH* better to launch a larger # of smaller payloads. For instance, if you need a satellite in Geosynchronous orbit, to launch the satellite in one launch and a disposable transfer-vehicle in another (which is inferior to a reusable infrastructure of tugs and fuel-depots, but doesn't have the same engineering challenges...) And, because the same Microwave Beamed Power can be used *beyond* Low Earth Orbit as to get there (but NOW for plasma-thrusters: don't make me get started on what a 50 MW plasma-thruster powered by Microwave Beamed-Power is capable of...), you should actually be able to get by with launching less fuel-mass to orbit in the first place... That's nonsense. That's Wikipedia users being stupid. We've already seen that NERVA accomplished better than that- 0.3 kN/Mw at 850 seconds. Those numbers have been *proven*- so anything Wikipedia users say about the maximum theoretical performance being lower than something that was actually tested and demonstrated to work better than that is just pure nonsense... And with a lower exhaust-temperature, you would get better Thrust/MW (the 850-1000 seconds of ISP with a Microwave Thermal Rocket that all the sources quote apparently comes from a larger expansion-ratio or a more efficient nozzle-design... Or perhaps "hotter than 2000 K" really meant closer to 2600 K- in which case you're right back to the *proven* 0.3 kN/MW of the NERVA) Nope. It's 0.30 kN/MW with NERVA at 850 seconds. That numbers is a hard *fact*. So the worst it could possibly be at 414 seconds is around 0.6 kN/MW... The 334 kN was indeed at vacuum ISP. The engine didn't even have the CAPACITY to reduce its ISP to improve its Thrust- so what you're saying is just pure nonsense... No offense. Look, 0.3 kN/MW (the *proven* figure of NERVA at 850 seconds ISP) isn't all that bad. Even if it's not possible to exceed that at an ISP of 850 seconds, you haven't made any kind of a point that a Microwave Thermal Spaceplane is unfeasible. The *whole point* of using a spaceplane is to get by with less beamed-power. And wings allow you to do that quite well. And, you've said nothing that defeats the proven ISP performance of a Thermal Rocket either- so when it comes down to it, in the end Microwave Thermal Spaceplanes *do* make sense... Because you don't *need* the payload-capacity of a Delta IV when you can bring down the cost/kg to half as much by launching half-size payloads (halving the payload/launch doubles the # of launches, and cuts down to half as much the amortized cost/launch of the Microwave Transmitters which ultimately drive up the cost...) And you don't *need* a TWR of 1.28 on the launchpad when you can get by with a TWR of 0.5 on the runway. And you don't need a complex plan to separately recover upper and lower-stages like Space-X has in mind (although so far, they're only close to recovering the launch-stages) when you can just fly the whole spaceplane back to the runway after every flight... And, if all this STILL isn't convincing that you can build an SSTO Microwave Thermal Spaceplane, you can always build a suborbital spaceplane that releases a Microwave Thermal Rocket above the atmosphere. Because if you *really did* want to get "the hell to orbit" and out of the atmosphere as quickly as possible after switching to rocket-propulsion (although as I've already pointed out, that's *not* how a spaceplane would reach orbit, and that's *not* the most efficient ascent. You *want* to stay in the atmosphere as long as possible- or at least until Lift/Drag = 1...) then there's no point in having wings once you're above the atmosphere- and deploying an upper-stage rockets gives you all the mass-fraction benefits of staging... No. I turns out we were bother off by a factor of 2- which is equally wrong... I've extensively researched real-world examples. But I made some mistakes in my research, and you now corrected them. You can rest assured that the KSP-Interstellar Extension Config I've been helping to develop will now have a realistic Thurst/MW of around 0.2-0.3 kN/MW, like the real-world NERVA... I never said anything to the contrary. To get 9.24 tons to LEO, it turns out you need around 1.6 GW of beamed-power. I wouldn't call that small. But, at least half the mass of a satellite in LEO destined for GEO is fuel and engines- so if you simply launch a transfer-stage and the satellite in two separate launches, you only need 800 MW... The *minimum* mass to LEO to get a small 1-man capsule up there is around 1 ton (the weight of a Mercury capsule without a Launch Escape System...) So if you built a spaceplane that could carry 1 ton to LEO per launch, you could even launch manned missions with only about 100 MW of beamed-power (that's using your own figure of a TWR of 0.5 on the runway being all you need to get to orbit...) Which only amounts to $200 million in Microwave Transmitters, and maybe $400 million in R&D costs... Amortize that over, say, 20 launches a year to the ISS (most of those crew-rotations and consumables, with 1 man riding up on each manned launch...) over 10 years, and you get a cost of *only* $3,000/kg to LEO, with a marginal cost of virtually nothing if you want to launch more to orbit each year than just ISS consumables and crew (because you've *already paid for* the Microwave Transmitters and R&D, additional launches each year cost virtually nothing but fuel and power...) There's nothing dubious about an air-breathing phase. The only thing we should be debating is *just how good* it would be, not whether it would work in the first place. We worked on Nuclear Thermal Turbojets back in the 1960's, and concluded there were no major obstacles to their use, although John F Kennedy shut the program down for political reasons and because he was afraid it might lead to a nuclear war... http://en.wikipedia.org/wiki/Aircraft_Nuclear_Propulsion See my numbers above. 200 launches over 10 years with a 1 metric ton to LEO spaceplane equates to a cost/kg to LEO of maybe only $3000/kg (assuming $400 million in Research and Development costs- which is quite extravagant considering how close the technology already is to realization...) You're right. 1 kN/MW was inaccurate with Hydrogen propulsion, as the figure for NERVA was only 0.3 kN/MW at 850 seconds (I should point out now that it's *ENTIRELY* realistic with a denser fuel like Ammonia, which would get more than 5x the Thrust/MW, at 63% the Specific Impulse, thanks to its breakdown into Nitrogen and Hydrogen at high temperatures *greatly* aiding Thrust production...) That doesn't mean the concept is unfeasible- only that it's even more important to amortize the cost of the Microwave Transmitters (as more than 3x the transmission-capacity will be required of what I originally expected) over as many launches as possible. Which is why companies like Escape Dynamics are looking at building a low payload-capacity vehicle that launches larger payloads (like a large GEO satellite, or a 3-man crew for the ISS) over multiple smaller launches... (such as by a separate launch for the satellite and a transfer-stage, or 1 crew member at a time...) No. Multi-GW is only necessary for large payloads. And if you are using a spaceplane, you only need about half the Thrust on the ground (and can use Thermal Turbojets to get up above the thickest part of the atmosphere- Mach 2 and 24 km is perfectly reasonable for them...) Build a spaceplane that launches 1-2 tons to LEO per mission, and you can amortize the cost of the Microwave Transmitters over many, many launches- and get a *very* low cost/kg to LEO... So, 0.3 kN/Mw in vacuum, 0.2 kN/MW at sea-level, when using Hydrogen. But you don't use Hydrogen at sea-level, that would be silly. (because Hydrogen is highly vulnerably to ISP-losses from atmospheric-compression at sea-level) You either use Thermal Turbojets or a heavier fuel such as Ammonia (which *does* get you 1 kN/MW at sea-level, at around 500 seconds ISP, and is *much* less vulnerable to atmospheric-compression due to the higher Exhaust Pressure you get this way- don't try to run this number through E = 1/2 m * v^2, because it doesn't compute. You're getting additional energy from the breakdown of Ammonia into Hydrogen and Nitrogen...) With one of those, you save the Hydrogen for high speed+altitude, where it's most effective... (theoretically, you get the best energy-efficiency from matching exhaust-velocity to vehicle velocity: so it makes more sense to use Hydrogen when you're already traveling fast...) Building an air-breathing stage isn't an impossibility. Will you stop talking about one like it is? If jet engines were impossible, we wouldn't fly passenger airlines around the world *all the time*. The fact is, jet engines are perfectly doable, and Thermal Turbojets are just an extension of the same concept that is actually *easier* to design and build due to the lack of having to maintain a fragile combustion reaction. Since you still don't believe me when I tell you *combustion is sensitive in a jet engine*, please see the following figure: This graph effectively summarizes the main reason why designing a Thermal Turbojet is so much easier than designing a normal jet engine (which is done all the time)- we don't have to deal with any of those combustion-limits... (and can operate at a much higher airflow- notice how the combustion reaction becomes more fragile at higher airflows? *That* is why we have to limit airflow at high speed on our chemical jet engines...) A 1:100 mass-ration for LOX or RP-1 seems *highly* unrealistic to me. Try 1:50 for a more realistic number. Whereas a 1:10 mass-ratio is the actual mass-ratio of the Centaur upper stage- which utilized Hydro/LOX propulsion... (and, due to the low density of Hydrogen, the vast majority of that tankage was for LH2...) Regards, Northstar

OK, so another screw-up on my part It appears I under-estimated the Thermal Power of the Tibmerwind 75- it had about 3750 MW of Thermal Power, not 750 MW... I actually had to back-derive this from known ThermalPower figures for the NERVA, and some conservative approximations of the efficiency of heat-transfer and such... The current performance (Thrust, ISP, etc.) for all our Nuclear Thermal Rockets is still correct- we just need to up-rate ThermalPower by a factor of 5, and decrease Thrust/MW by a factor of 5 as well. Obviously, this hurts the utility of solar-powered Microwave Thermal Rockets. Otherwise, it's not the hugest issue- just one of realism, rather than balance (which remains *mostly* unchanged- it DOES mean our reactors will consume uranium 5x as fast, and require 5x the radiator-mass, though...) Regards, Northstar - - - Updated - - - Well, I *DID* mess up the Thrust/MW and total ThermalPower of the nuclear reactors. The Thrust, mass, and ISP remain the same- but the reactors *should* require 5x the current radiator-mass, and consume uranium 5x as quickly... (Although, as I pointed out to Fractal_UK, the upgraded radiators are current under-powered: with nano-engineered graphene it's now possible to build radiators with an emissivity factor GREATER THAN 1- a feat previously thought impossible... Basically, some nano-materials can be blacker than pure black... This means, once you upgrade your radiators, they *should* radiate more power for the same temperature than they currently do...) But, yes, it's mostly being afraid of the capital N... Fortunately, Kerbals don't seem to mind nuclear rockets... Regards, Northstar

I was thinking of the SM-65 Atlas ICBM rocket, not the Atlas V or earlier Atlas launch-family rockets. Sorry for any confusion this caused... It turns out the Centaur balloon tanks were quite a bit less impressive that I remembered, though- Centaur only managed 90% ratios (therein lies the 1:10 mass ratio Iskierka mentioned before), although it must be pointed out this was the mass-ratio of the *entire* upper stage... I do have to apologize though. My Thrust/MW figures were *VERY* off for Thermal Turbojets. Not because I didn't know how to calculate Thrust/MW correctly (it's, in fact, something I've become very skilled at lately) but because of a stupid math error- I accidentally forgot to divide standard gravity ("g", 9.80665 m/s^2) out at one point in my equations. The result was a Thrust/MW value that was 9.80665 times too high... The *CORRECT* Thrust/MW for a Thermal Turbojet: Sea-Level: 0.738 kN/MW Ideal Speed/Altitude: 2.306 kN/MW Now THAT seems a lot more reasonable, doesn't it? Regards, Northstar

Freethinker, A question about an entry in the Changelog. Version 0.7.6 says: "Fixed Hydrolox and LiquidCO2 Propellant" I get that the changes to Hydrolox were to adjust the fuel-ratio to 1:4, like I posted about before- but what changes did you make to the LiquidCO2 propellant? Also, forget what I said about reducing the Thrust for Water and Ammonia, like I posted about before. I gave you some numbers to use for those before, but the numbers from Atomic Rockets may be more accurate, as I may be mis-understanding the exact effects of Hydrogen-bonding on the Thrust and ISP of Ammonia and Water... Let's apply an equation we already know to their data on Exhaust Velocity: Thrust = Exhaust Velocity * Mass Flow Rate So, if we use the values for Exhaust Velocity from Atomic Rockets (I have no idea where the #'s come from, or how accurate they are, but...) and assume that Mass Flow Rate increases proportional to the Molecular Mass of each propellant (that is, the liters/minute flow-rate remains unchanged) then you get... Ammonia Thrust = 5101 * (17.03/2.02) = 43005 Water Thrust = 4042 * (18.02/2.02) = 36058 Note that these are arbitrary numbers with no physical significance, but they indicate Thrust relative to LH2 (which using this equation has a Thrust value of 8093). But we already know Hydrogen gets about 1 kN/MW, so if we convert using that we get... (note that I kept more decimal places in the calculator than I show above) Ammonia Thrust/MW: 5.31 kN/MW Relative ISP: 5101/8093 = 63.03% of Hydrogen Water Thrust/MW: 36058/8093 = 4.46 kN/MW Relative ISP: 4042/8093 = 49.94% of Hydrogen This actually leads to a SIGNIFICANTLY higher Thrust/MW than currently (only around 2 kN/MW with Water using the currently-assigned ISP). But MAYBE, because due to Hydrogen Bonding the specific heat capacity is higher, these numbers assume you simply reduce the propellant flow-rate in liters/minute to compensate for this... In which case. I'm inclined to go with the latter, because it doesn't require us to do anything more than adjust the Specific Impulse for Ammonia and Water... Anyways, the CURRENT ISPmultipliers of Water and Ammonia are VERY close to these numbers (0.4714 vs. 0.4994 for Water, identical for Ammonia) so I'm inclined to let the numbers be... Apparently Fractal_UK *gasp* went out and did research on the effects of Hydrogen-Bonding on these propellant behaviors, and in this case was much more correct than what I came up with before... ALSO, a HUGE error in my part before. When I was calculating the expected Thrust/MW of the Thermal Turbojets, I accidentally multiplied in "g" (standard gravity) an extra time, by forgetting to divide it out of BOTH sides of an equation. The resulting Thrust/MW was 9.80665 times higher than it should be. The Thrust/MW should only have been increased 1.109 times, rather than 10.8774 times. Apparently Fractal_UK's original Thermal Turbojet performance we rather close to reality (only slightly worse) and OVERPOWERED compared to the originally (unrealistically weak) performance of the Thermal Rockets... Summary/Conclusions: - Leave the ISPmultipliers, Thrust, etc. of Water and Ammonia alone - Revert the 10.8774 times increase in Thrust/MW for the Thermal Turbojets, and only increase it by 1.109 times instead! Regards, Northstar

Nope. Look at the Exhaust Velocity of Ammonia in that table. It's much lower than Methane, despite having a nearly-identical Molecular MAss More thoughts to come later. Regards, Northstar

OK, first of all, I do honestly believe you're just trying to be a troll. If not by ignoring my arguments and wildly-misrepresenting the actual facts, then by posting long walls of text that say nothing and *intentionally* trying to get my pulse up. As such, I'm going to answer your post, but I would ask that you refrain from posting anything further longer than about two paragraphs at a time on this thread (I will try to keep my response length the same), so that our discussion does not hijack this thread. IF you can't abide by that, I would respectfully ask that you leave my thread (I started this thread) and never come back. Then go with Hydro/LOX, and have a LOX afterburner LANTR-style. Your numbers for LH2 fuel tank mass fractions are wildly inaccurate, though. Consider the Atlas rockets or Centaur upper stage (can't provide a link tight now, as my internet is being wacky). They had total mass fractions in excess of 95%, with LH2/LOX propulsion the whole way. How would that be possible if the vast majority of their fuel tanks had a mass-fraction of 10%? The need for a lighter compressor. The lack of a need for a fuel-pump? The replacement of a combustion chamber with (relatively much lighter) Microwave Thermal Receivers- even if the combustion chamber is only a small proportion of mass to begin with? I've already listed several ways you save on mass, and you've ignored every one of them- which reaffirms my suspicion you're not looking to have a reasonable discussion. No, Power is the most important thing, period. You know that. The more power you can get for a given mass, the higher your TWR and the less engine mass you need in the first place. There are two ways to get very high TWR- one is to have very low mass, and the other is to have very high Thrust. The Thermal Turbojet takes mainly the latter approach, even if it is also*slightly* lighter due to the lack of need for a fuel pump or combustion chamber. When you're traveling at Mach 3, that's a HUGE slow-down. The data says differently- most jets combust at around Mach 0.4-0.5, which is *not* "above Mach 0.5". A Thermal Turbojet operates well as supersonic flow conditions internally, by contrast. Note I said "turbojet"- you keep equating it with a Turbofan, which it is not. There are no fan blades involved in the design. Countless engineering studies say differently. The combustion process is sensitive to temperature. It is sensitive to very low pressures. And, it is sensitive to the mixing-ratio between air and fuel, which is the primary reason you have to limit airflow at high speeds. It's not that you CAN'T fit the entire airflow through at high speed/altitude flight (the Venturi Effect guarantees that you can- the airspeed inside the engine can always increase to increase mass flow rate), it's that doing so would move the internal conditions outside the range where combustion can efficiently occur (in particular, the fuel-pump doesn't magically become capable of pumping more fuel just because you have a higher airflow, and you need a certain fuel:air ratio for the combustion process to be stable. Thermal Turbojets avoid this issue by not needing a fuel-pump!) Not, it's just *less* of a concern- because a Thermal Turbojet can operate at much higher internal pressures and speeds. Half our problem is that you're comparing Turbojet performance (which works better at high speeds and altitudes) to Turbofan performance (which works poorly at high speeds and altitudes). They are *not* the same thing. This statement is completely unclear as to what it is referring to. It doesn't need to be effective- it just needs to work. Because Thermal Turbojets are *turbojets* and not *turbofans* they work better at higher speeds and pressures. You only need enough Thrust to get off the runway... It's not an issue, so stop making it out to be one. Your understanding of fluid dynamics is, at best, drastically messed up. The airflow can do any of several things as it compresses- it can move faster, it can get hotter, or it can increase in pressure. Normally, it does a combination of all 3 of these things. The increase in temperature, in particular, is a major concern, and the usual limiting-factor on airflow to a chemical jet is the temperature reached by the final blade of the compressor (where it gets hottest). There is absolutely no concern about being able to fit the full airflow of the intake through the engine- there is a concern about being able to do it without the compressor blades melting. By relying more on ram-compression effects, and having a less powerful compressor to begin with, it's possible to get MUCH higher airflows at high speed/altitude, at the expense of sea-level performance... (which I've already admitted, is comparably low for a Thermal Turbojet compared to its performance at speed/altitude- but still not a significant problem for getting off the runway. Because TWR improves as you ascend, and you're optimizing for minimal power-usage instead of fuel-consumption, you don't need a liftoff TWR of 0.5 on the runway for an optimal ascent- a liftoff TWR of 0.2 is fine if the TWR climbs as your plane does...) Once again, the airflow *does* fit into the engine. It's just a matter of doing it without melting the engine. For which, pre-coolers help (and you can dump the vaporized Hydrogen overboard via a small ramjet like with SABRE). It's better to have a larger intake at high altitude if you can effectively utilize all that airflow- which a cehmical jet can't do, but a TTJ can do. Your understanding of fluid dynamics, and the reason for having to limit airflow at high speeds is faulty. I won't discuss this more, because you won't listen to me when I tell you why and how you're wrong, and your arguments are scientifically inaccurate. But that wasn't a part of the discussion, or what I said you were mis-construing, was it? Because they're made of lightweight semiconductors, rather than metal. This is also the reason they only operate at 2000 Kelivin when the beamed-pwoer could easily heat them hotter than this... You did. Do I have to go back and quote you? The difference is how much airflow you are heating at that temperature. Jet engines are limited in the airflow they can process, if nothing else, by the size of their fuel-pump (as you've already acknowledged, the J58 fuel-pump was HUGE). A 2000 K thermal receiver could have 10x the airflow or more of a combustion chamber without issue. You don't have the same mass-flow limits, as I've repeatedly stated. The limiting considerations are *not* the same, and I have to get going irl. Other parts of your post will be competently addressed later. I don't have time to do them justice right now. Regards, Northstar

ABSOLUTELY NOT. You couldn't POSSIBLY be more wrong. A spaceplane, just like a rocket, is designed for VERY HIGH fuel-fraction. The VAST majority of the weight is in fuel. And fuel tanks are much lighter than the fuel they hold inside them. If you used LH2, you would end up with a MUCH lighter spaceplane... If you don't understand that, you don't understand the Rocket Equation, and there's little point in us even talking further... No, it *IS* much less. Because you get a *VASTLY* superior Thrust for the same engine-size, require no fuel for the atmospheric portion of the flight, and thus can get away with a significantly smaller engine. See my current attempts to implement realistic total Thrust values for the KSP-Interstellar Thermal Turbojets, where, by applying realistic equations about the relationship between thermal energy and exhaust velocity, I find that at an Exhaust Velocity of about 1333.78 m/s (which is INCREDIBLY slow for any type of Thermal Rocket, but very fast for a jet engine) the Thrust/MW reaches over 22 kN/MW at ideal operating conditions, and 7.24 kn/MW at sea-level. I don't know how this compares in terms of kN/MW to a chemical jet engine, but I *DO* know this: it is perfectly reasonable for a Thermal Rocket at that Exhaust Velocity, and it matches well to predictions for Thermal Turbojets. Considering a 1/4 scale version of the Timberwind 75 Nuclear Thermal Rocket could achieve 187.5 MW of ThermalPower (and the Timberwind 75, with 163.7376% more cross-sectional area and 4x the total size, could produce a solid 750 MW), you can easily end up with OVER 1200 kN of Thrust at sea-level with just 187.5 MW of ThermalPower using a 3000 K heat-source. However, although Microwave Thermal Turbojets would likely operate at SIGNIFICANTLY lower power-levels on take-off, their heat-source would also be much cooler- around 2000 K instead of 3000 K. Why does this matter? It means you get EVEN HIGHER Thrust/MW, at the expense of Exhaust Velocity. A 2000K heat-source could easily mean only 2/3rd the Exhaust Velocity (I'd have to run some calculations to determine the actual number), and thus more than 1/3rd better Thrust/MW. Which means that sea-level Thrust/MW of more than 9.6 kN/MW, and optimal Thrust/MW of more than 28 kN/MW could *EASILY* be achievable. Why all this talk of Thrust/MW? Because, with a tiny, lightweight Microwave Receiver (an appropriate-sized receiver would not weigh more than 200 kg AT MOST) that is having only a paltry 18 MW of Microwave Power beamed at it (EASILY achievable, considering a Microwave-Powered launch vehicle would operate in the range of AT LEAST 100 MW for the main transmitter array), you could achieve a Thrust of over 172 kN at sea-level, which is better than the 151 kN maximum Thrust of the J58 engines that powered the SR-71 Blackbird. And while an SR-71 carried 38.9 metric tons of fuel just for its relatively short bouts of hypersonic flight, a pair of 18 MW Thermal Turbojets could achieve better Thrust than this at SEA-LEVEL (and more than 3 times this Thrust at optimal flight-conditions) for no more than the weight of the engines (which would be LIGHTER than the J58 engines- which weighed 2700 kg each) and intake system (compressor weight is part of the 2700 kg figure for the J58 engines). NOW are you starting to get the picture of why the performance allowed by Microwave Thermal Turbojets is so great? I'd call that a HUGE difference. That's a more than 20% difference in TWR! One of the things you have to realize about Thermal Turbojets is that they don't suffer the same trade-offs as chemical jet engines. A chemical jet engine, for instance, has to slow its exhaust down to certain speed and pressure conditions in order to effect combustion. Not so with a Thermal Turbojet. Because there is no combustion reaction that occurs, the engine design is MUCH more tolerant of higher speeds and lower pressures after the compressor. Which means one of THE MOST DIFFICULT aspects of engineering a high-performance jet engine (the Compressor) becomes a FRACTION of the difficulty when engineering a Thermal Turbojet... The other extremely difficult thing to engineer about a chemical jet engines is having a stable mixture-ratio of fuel to air. Too much of either, and the combustion reaction dies out. Not so with a Thermal Turbojet. Because there is NO combustion reaction, there is ABSOLUTELY NO CONCERN about staying within this envelope. Which means,, once again, that a Thermal Turbojet can be designed within a MUCH wider range of tolerances as to internal operating conditions... How many times do I have to say this. A Microwave Thermal Spaceplane does NOT have a difficult time getting airborne. Not only are its Thermal Turbojet engines MUCH better-performing than chemical jet engines- both in terms of TWR and maximum Thrust (with nuclear-reactor like power-levels, it's possible to get THOUSANDS of kN of Thrust with sufficient available airflow), which means if ANYTHING should be able to get airborne, it's the Microwave Thermal Spaceplane; the aircraft also requires MUCH less fuel-mass than any existing chemical spaceplane design (such as Skylon), which means a lower wing-loading, which means an easier take-off... No, you *DO* need large intakes with a Thermal Turbojet. Because the Thrust potential is so enormous (we're talking THOUSANDS of kN of Thrust once you turn on the high-powered transmitter array down-range and have a couple hundred MW of ThermalPower available...) you need an enormous airflow in order to produce it. And, with an ideal theoretical spaceplane design, you want as high a ratio on Intake Area to total drag as possible- the only reason chemical spaceplane designs shrug off so much potential airflow is because they aren't able to USE all that extra airflow, unlike a Thermal Turbojet (with a chemical jet engine, adding too much air will kill the combustion reaction- NOT an issue AT ALL with a Thermal Turbojet...) These jet designs had to close off some of their intake area because: (1) Their compressors weren't capable of handling such a large airflow (NOT an issue with a Microwave Thermal Turbojet aircraft, where a *FAR* lower compression-ratio is necessary, and you have a lot more mass to devote to bigger compressors thanks to your massive fuel-savings). (2) Too much airflow would have snuffled out their combustion reactions. Once again, NOT an issue with Thermal Turbojets. The optimal design criteria change *GREATLY* with a Thermal Turbojet vs. a chemical jet engine. Instead of trying to keep internal conditions within a narrow range of airflows, pressures, and speeds so as to create a sustained combustion reaction, with a Thermal Turbojet you're simply trying to shove as much airflow through as quickly as possible, so as to give the Heat Exchanges the chance to dissipate very high power-levels. And remember what I said before about possibly having a SABRE-like fuel mode with a Thermal Turbojet aircraft at high speed/altitude? Forget it. It was a stupid idea- the more I learn about the greatest difficulties of high-performance jet engine design, the more I realize that the advantages of not having to worry about a combustion reaction GREATLY outweigh any extra Thermal Power you might be able to squeeze out of the engine this way... You're right about not being able to re-use the LH2, and why the SABRE uses it in a series of surrounding Ramjets. I forgot about that before (yes, I DID previously know about that). But, there is absolutely no reason that a Microwave Thermal Spaceplane can't do the same exact thing- using LH2 as coolant, and then burn it in a series of surrounding ramjets entirely separate from the main (Thermal Turbojet) engine assembly. Thanks for reminding me of the SABRE ramjets, because otherwise I wouldn't have considered that very simply solution to a very obnoxious problem (pre-cooling the air intakes at hypersonic speeds). Don't mis-construe my ideas. You know, it's getting rather obnoxious that you keep doing that? I don't like it, and would ask that you stop- I'm not doing it to you. The point of my statement was VERY clear- you said Microwave Thermal Receivers are HEAVY, and I said they're not- in fact, they're lighter than combustion chambers. Just because I said they're lighter than combustion chambers doesn't mean I think combustion chambers are heavy- only that Microwave Thermal Receivers AREN'T- and that they're lighter than the comparable component they replace. As for the superior TWR, I didn't explain the math/reasoning behind that very well. I've done a MUCH better job of explaining it here. It's NOT that Thermal Turbojets are necessarily LIGHTER than chemical jet engines for their size/volume (they are also quite heavy), it's that they produce MUCH MORE THRUST for their size/volume- which means you get a higher TWR, and are COMPARATIVELY very light for their performance. Did I do a better job of explaining it here? Do you get it now? Because a Thermal Turbojet is capable of INCREDIBLE Thrust performance (not having to worry about maintaining a combustion reaction, it can work with VERY high airflows, and thus attains the advantages of getting an ENORMOUS working-mass to accelerate) it doesn't have to be as large as a chemical jet to provide the same Thrust. Which means it won't be as heavy- simply because it's smaller. A 1 meter jet engine is going to weigh a LOT less, generally speaking, and a 2 meter jet engine (just to use some made-up diameters...) This is why the fact that a Thermal Turbojet doesn't require high compression-factors (or in fact much compression-factor at all) works GREATLY to its advantage... Less load on the compressor means less heating, which means more favorable stagnation temperatures up into very high speeds... As I said before, though, the point of a Thermal Turbojet is *NOT* to gain a significant fraction of orbital velocity with air-breathing engines. It *MIGHT* make it up to Mach 4 or 5 in air-breathing mode, depending on exactly how much work you want to put into making the design work well at higher speeds. After that, you're going to want to switch over to Thermal Rocket propulsion. The beauty of the wide range of Thermal Turbojet internal operating conditions that you can design to is that it should be comparably EASY to switch into a rocket-mode using the same engine, unlike the difficulty of engineering something like SABRE. However even if you CAN'T do that, a new Thermal Receiver and rocket-nozzle doesn't weigh that much anyways (maybe a few hundred kg at most)- the VAST majority of the weight in a Microwave Thermal Rocket is in the turbopump- which is an extremely heavy component you're NOT going to need on the Thermal Turbojet anyways... (and one of the reasons a Thermal Turbojet *IS* somewhat lighter than a chemical jet engine of the same size, even if I agree, you ARE going to need a lot of the other heavy components like compressors...) Which is therefore a heat-sink. You're talking yourself in circles again. You're joking right? No seriously, tell me you're joking. A Microwave Thermal Receiver heats up to 2000 Kelvin or more. Liquid Hydrogen used as coolant is NOT going to get *NEARLY* that hot before you eject it through a Thermal Rocket (if at the point in your flight where you're running rockets and jets side-by-side), or earlier in the flight through a secondary ramjet (like with SABRE). No, it's NOT. Microwaves don't just power Thermal Turbojets- they power ROCKETS too- as I've REPEATEDLY made a point of saying. Now if you're talking about the Thermal Turbojets, it's true that they won't operate into very high speeds- they're going to start losing Thrust fast after Mach 3 (although their Thrust before this point will be SO HIGH that they can lose quite a LOT of Thrust before it starts to become a problem), and are going to probably require concurrent use of rockets after about Mach 4. By Mach 5, the air-breathing components are nothing more than deadweight- but by this point you could have climbed to a VERY HIGH altitude thanks to the low wing-loading, and extreme endurance of the craft when under Thermal Turbojet power, and will be able to acquire a MUCH higher Thrust/MW and ISP from the Thermal Rockets than if you had fired them off at sea-level... You talk about how much deadweight a Thermal Turbojet is going to pose (2-4 metric tons per turbojet if their weight is even remotely similar to that of the J58- which weighed 2700 kg- and in fact due to the lack of a turbopump and the need for a less powerful compressor for their airflow rate, they could be a good bit lighter...) and then you propose a SOLID ROCKET BOOSTER? I just don't know what to do with you... The point of a spaceplane isn't just the airbreathing engines. In fact, with a Microwave Thermal Spaceplane, that's not even the primary concern. Whereas with a chemical spaceplane, the jets are the primary advantage, and the wings are just a secondary benefit; with a Microwave Thermal Spaceplane, the WINGS are the primary advantage, and the Thermal Turbojets are just a secondary benefit... Why? Because Lift/Drag. Anything, and I mean *ANYTHING* you can do to reduce the amount of Microwave Beamed Power your launch vehicle is going to need to stay in the air, and ultimately climb, is going to pay off MASSIVELY in the long run. This is because the BIGGEST, BADDEST, MOST EXPENSIVE component of a Microwave Thermal Spaceplane isn't in the plane at all- it is in the Microwave Transmitters on the ground. The simple fact that you can not only continue climbing, but actually handily GAIN speed and altitude with a TWR of say, 0.8 or 0.9 on a Microwave Thermal Spaceplane under rocket-propulsion is a *HUGE* advantage. This works at high speeds/altitudes too: even if your Lift/Drag is only 1.5 or 1.2 due to very high speed, it's still saving you an *ENORMOUS* cost in Microwave Transmitters in the long run... In fact, the optimal wing-loading on a Microwave Thermal Spaceplane probably is much less than on a chemical spaceplane from a cost-perspective, because you're not trying to minimize fuel-consumption or reduce the size or cost of the plane itself- you're trying to get as heavy a payload to orbit as possible for as little Microwave Beamed Power as possible. Almost NOTHING, and I repeat NOTHING else really matters in the final cost-analysis of a Microwave Thermal Spaceplane other than the number of ground-based Microwave Transmitters you need to build to make it fly and allow it to reach orbit... A Microwave Thermal Spaceplane doesn't have to worry about Delta-V to *NEARLY* the same degree as a chemical spaceplane does. If you look at the Rocket Equation, a mass-ratio of just 3.4 will give you MORE than 10 km/s of Delta-V with a Hydrogen-propelled Microwave Thermal Spaceplane. And, as I pointed out before, you can use "stages" of heavier to lighter fuel-modes to help bring down the total vessel-size if you want, although that will lead to a significantly higher required mass-fraction (but a net DECREASE in the size and dry-mass of the spaceplane...) Either you're blissfully unaware of the subject you're talking about, or you're just *trying* to be a troll at this point. How many times have I stated the EXCEPTIONAL performance of a Microwave Thermal ROCKET. The Thermal Turbojet-propelled stage may exist only to get the rocket-propelled stage up in the air (although a similar thing could be said in all honesty of ANY spaceplane design), but the rocket-propelled stage DRASTICALLY out-performs *ANY* known chemical rocket, both in terms of Thrust-Weight Ratio and Specific Impulse. There can be no if's, and's, or but's about that if you've any sense on how to read numbers whatsoever... Such as? I once spent WEEKS trying to find a cheap booster that could kick a spaceplane designed for actual horizontal flight (rather than something like a Shuttle) to gain speed and altitude under rocket-propulsion to high-altitude, where the spaceplane could then safely detach without plummeting to its doom due to its lack of significant horizontal velocity to not quickly stall out. There is NOT SUCH THING as a cheap booster that could get the spaceplane up to high altitude. The BEST, and most cost-effective solution BY FAR is just to fly the spaceplane up there with Thermal Turbojets before switching over to rockets (which is where the game's really at when it comes to Microwave Thermal Spaceplanes. STOP. FOCUSING. ON THE THERMAL TURBOJETS!) No, it wouldn't. A Thermal Turbojet requires no fuel. It can operate up to AT LEAST Mach 3 and 24,000 meters altitude with the kind of wing-loads of a hydrogen-propelled Microwave Thermal Spaceplane without problem. And it *ONLY* weighs a few tons for several THOUSAND kN of Thrust at a couple hundred Megawatts of beamed-power. That is going to be MUCH more cost-effective than any fly-back booster I know of... Don't insult me. Especially when you're clearly wrong. I'm struggling not to call you all sorts of foul names, but your behavior is INCREDIBLE arrogant. ThermalPower does *NOT* always equal Exhaust Velocity * Thrust. It should be *painfully* obvious to anyone with the most BASIC understanding of physics that as E = 1/2 * m * v^2 if you increase your Exhaust Velocity by a factor of 2, and keep Mass Flow Rate constant, you will increase your Thermal Power Requirements by 4, for instance. The RELEVANT equations are: Energy = 1/2 mass * velocity^2 and Thrust = Mass Flow Rate * Exhaust Velocity From these two simple equations, you can calculate 90% of what you need to know when it comes to Microwave Thermal Rocketry. There are other equations too, but I'm going to leave those aside for now, because you clearly don't wish to try and understand the actual numbers or math behind any of this, and I've gone on for quite long enough to make my eyes burn just staring at this computer screen... Your numbers are wrong. The $1.58 billion figure (approximately 790 MW in Microwave Beamed Power) stands. That figure comes from nowhere. As I *REPEATEDLY* pointed out, the Timberwind Nuclear Thermal Rocket designs were supposed to be able to achieve just short of 1 kN/MW of ThermalPower at a Specific Impulse of 1000 seconds and a core temperature of 3000 Kelvin. At a heat exchanger temperature of a bit over 2000 Kelvin and a Specific Impulse of 850 seconds, a Microwave Thermal Rocket gets *MUCH* higher Thrust/MW than that... But I assume the rest of the improvement over 1 kn/MW is lost to transmission inefficiency and such- is where the approximation of 1 kN.MW comes from... Your numbers are just ridiculous. They are COMPLETELY out of line with known real-world designs. They are out of line with the mathematical equations. There are even out of line with common sense. And you do *NOTHING* to back them- you just state them as a matter of fact. I have math to back me. I have real designs to back me. What do you have? The MATH backs $1.58 billion. The numbers are $2 million/ MW, and 1 kN/ MW. That comes out to 790 MW of power, which means $1.58 billion in transmitters. How much simpler can I make this for you? You question the figure of 1 kN/MW, but you provide absolutely no reasoning to back the assertion that it is wrong, whereas I have MANY real-world examples of Nuclear Thermal Rocket designs that back my figure (including NERVA, the Russian analog, Timberwind, the US Air Force SNTP Program, and the joint US/Russian Bimodal Nuclear Thermal Propulsion Program- ALL of which can be used to support a figure of approximately 1 kN/MW at 1000 seconds of Specific Impulse using Hydrogen...) For instance, Project Timberwind designs, with a much higher exhaust temperature of 3000 Kelvin, and an ISP of 1000 seconds (both these numbers are important, because they help provide an idea how much Thrust is coming from the nozzle's Expansion Ratio- which was not very much in the case of Timberwind, thus leaving SIGNIFICANT room for improvement with a Microwave Thermal Rocket using a larger nozzle, if you lifted it up above the thickest part of the atmosphere with a Thermal Turbojet...) were expected to achieve a Thrust/MW of approximately 1 kN/MW. If you can't accept the hard physical facts of reality, there's no point in talking further. Support your assertions with math, and *ACTUALLY KNOW* your equations. Multi-GW? Since *WHEN* did 790 MW for a Thermal Rocket (which only gets 1 kN/MW) to get a TWR of 1.28 turn into multiple GIGAWATTS for a Thermal Turbojet (which gets a Thrust/MW of *at least* 7.2 kN/MW, and likely about 9.6 kN/MW of the runway) for a spaceplane (of undetermined mass) to get a TWR of 0.5 on the runway? Oh, that's right. You inflated your figure for the rocket to 3 GW (which is COMPLETELY inaccurate). That's STILL not even a single GW on the runway- if you divide 3 GW by 7.2, and then again by 2.56 (1.28/0.5) you are only going to require about 163 MW- and once again that figure of 3 GW is *WILDLY* inaccurate, and the CORRECT figure is only 790 MW for the rocket (and only 43 MW for a 62.8 ton spaceplane to get off the runway- although at THAT power-level, it won't be reaching orbit with a considerable-sized cargo anytime soon...) Regards, Northstar

You know how to post IMGUR images to the forums so they're visible without needing to click on the link, right? For an album, you use the tag for the album and "Imgur" between two brackets, with a / symbol before the second "Imgur". For an individual image, it's the link and "img" instead. So, replace the * symbols with brackets and.. *Imgur* tag */Imgur* *img* link */img* So, THIS is what you get for your links: Also, NOTHING is visible in your last image- you're either zoomed too far out, or it's simply too dark... Regards, Northstar

OK, so took a look at the performance of the Thermal Turbojets, now that we're more or less done with the Thermal Rockets. Here's what I got for a basic Runway test: So, we get 124.8 kN of Thrust for 187.5 MW of ThermalPower at an ISP of 136.1 seconds... That equates to 0.6656 kN/MW, which is *FAR* too low... OK, so now let's plug this into the equations we already know to get the CORRECT Thrust/MW so we can adjust it... First of all, we need a standard to adjust to. Luckily, we already have this: the expected vacuum behavior of the Timberwind Nuclear Thermal Rockets in vacuum. These produce a bit under 1 kN/MW (our version produces a bit more Thrust/MW in vacuum, due to having nozzles that are optimized for Vacuum usage when the same diameter as the reactor...) Thermal Tubojets, however, unlike Thermal Rockets, get their best Thrust/MW performance at an atmospheric pressure of about 0.3 atm in KSP. Their ISP is 2500 at this altitude according to the currently-used Thermal Turbojet atmosphere-curve: atmosphereCurve { key = 0 1200 key = 0.3 2500 key = 1 800 } However at pressures of 1 atm or above, they get only 800 seconds ISP (our ISP is even lower because KSP-I then adjusts this # for reactor temperature- I have NO IDEA what reactor temperature the curve was first generated for, and I don't care enough to run the calculations necessary to find out...) So, our Thrust/MW and ISP should theoretically be (2500/800) = 3.125 times higher at optimal atmospheric pressure, which is what we should adjust our calculations to, or else we'll end up making our TTJ's *MUCH* too powerful when attempting to buff them to realistic values to match the Thermal Rockets... (currently, they are far too weak compared to the Thermal Rockets) That means, our OPTIMAL Thrust/MW is *CURRENTLY* 2.08 kn/MW (which is still too low for the ISP of 425.3125 seconds under optimal conditions with this reactor...) However it's worth noting the Thermal Turbojet will NEVER perform at this level because it will also lose Thrust to its VelocityCurve as it flies faster... velocityCurve { key = 0 1 0 0 key = 400 0.8 0 0 key = 800 0.9 0 0 key = 1700 0 0 0 } In fact, as you can see, when traveling at 1700 m/s (just under Mach 5) with our current VelocityCurve, our Thermal Turbojet will produce NO THRUST WHATSOEVER. Which is actually perfectly realistic- in fact this about the maximum possible speed an advanced air-breathing engine like SABRE can operate at... Anyways, so now that I've explained the caveats and limitations of why it will be impossible to see performance this good in practice, let's see what we can't do to bring the *theoretical* optimal performance for our Thermal Turbojet (at an ambient pressure of 30.3975 kPa and an airspeed of ZERO) up to where it should be... OK, so the first equations we need here are the following: Thurst = Mass Flow Rate * Specific Impulse * g E = 1/2 * m * v2 and, derived from these equations: Isp1/Isp2 = SqRt (m2/m1) That is, the total mass of atmosphere our Thermal Turbojet is acting on, compared to a Thermal Rocket (or Thermal Turbojet) at higher Specific Impulse will be the square-root of the ratio of the TTJ's ISP to the higher-ISP Thermal Rocket/Turbojet's ISP... It's worth noting that unlike with a Thermal Rocket, where the Mass Flow Rate is typically increased by using a denser propellant, a Thermal Turbojet simply grabs more atmosphere with its intakes to provide additional Thrust, provided more atmosphere is available through the intakes... In this aspect, hotter nuclear reactors will allow higher-altitude flight because they can achieve the same Thrust with significantly less airflow... Anyways, first of all, using our OPTIMAL ISP of 425.3125 seconds... 1000/425.3125 = SqRt (m2/m1) --> m2/m1 = 5.529 So, our Thermal Turbojet will have 5.529 times the Mass Flow Rate of a Timberwind NTR in vacuum. Or, approximately, a 1.25 meter Sethlans using Hydrogen in Vacuum at an ISP of 1150 seconds (since we set the extra ISP to come from higher Thrust at the same Mass Flow Rate, in keeping with the higher Vacuum ISP coming from the nozzle...) That could be useful to note for later- since it might help us confirm the Thermal Turbojet is working correctly with the new performance values we give it... OK, now what about Thrust? We need an equation for Thrust that compares it to a NTR at 1000 seconds ISP as well... Thrust = Mass Flow Rate * ISP * g ThrustTTJ/ThrustNTR = 5.529 * (425.3125 seconds/1000 seconds) * 9.80665 = 23.0575 Note that "g" is "standard gravity"- the nominal gravitational acceleration of an object in vacuum near the surface of the Earth, and is inherently tied up in our calculation due to the convention of expressing Specific Impulse in seconds instead of as Effective Exhaust Velocity (in m/s)... OK, so anyways, we know that our Thermal Turbojet should produce 23.0575 times the Thrust of a theoretical 187.5 MW NTR with an ISP of 1000 seconds... Which is just a 1/4th scale version of the "Timberwind 75" Nuclear Thermal Rocket (and this is why I choose to standardize performance against the "Timberwind 75" design specs as much as possible earlier in development- so we could refer back to this real/known number as much as possible for later development...) We know the expected Vacuum Thrust for our theoretical reference Nuclear Thermal Rocket, then- 1/4th the Vacuum Thrust of the Timberwind 75, or (735.5 / 4) = 183.875 kN So, we can calculate the expected *OPTIMAL* Thrust of our Thermal Turbojet: 23.0575 * (735.5 / 4) = 4239.70 kN Seems rather high, doesn't it? But remember, we only get this performance under OPTIMAL conditions. How do we do at sea-level at a standstill? (4239.7) * (800/2500) = 1356.7 kN That's a little more reasonable (a bit over 6 times the Thrust of a comparable NTR in vacuum- which is expected, as Thermal Turbojets get *MUCH* better Thrust/MW than Thermal Rockets due to their higher Mass Flow Rate...) Note that when in flight, we'll *quickly* start to lose even more Thrust at high altitude due to the Velocity Curve, and we'll still produce ZERO Thrust at an airspeed of 1700 m/s... Anyways, how are we doing for Thrust/MW now? Sea-Level Performance: 7.24 kN/MW OPTIMAL Performance: 22.61 kN/MW Seems about right given that Thermal Turbojets are *SUPPOSED TO* get much higher Thrust/MW than Thermal Rockets... The Thrust *is* rather high, but keep in mind that our reactor is HUGE and *EXTREMELY* POWERFUL for a Thermal Turbojet- the one designed for the Aircraft Nuclear Propulsion Project was a 2.5 MW reactor that operated at 1133.15 degrees Kelvin. IF it had actually been used in-flight instead of just carried up as a dummy, it could have produced 56.53 kN of Thrust at optimal conditions at the same Exhaust Velocity as our reactor here (or, more likely given the lower operating temperature, even MORE Thrust at a *lower* Exhaust Velocity) for a reactor that would have weighed less than 100 kg if it were built to the same Power/mass ratios as the Timberwind 75... Also, remember, it's going to take some *INSANE* air-hogging to get enough Intake Area to run a Thermal Turbojet that powerful at full-thrust, even at sea-level. Forget about running in at full-thrust at high-altitude... Back to the main topic, and sorry for the tangents... Here is a comparison between our CURRENT sea-level performance (standstill, on the runway) and the CORRECT sea-level performance: CURRENT Sea-Level Performance: 0.6656 kN/MW CORRECT Sea-Level Performance: 7.24 kN/MW Which means, we need to multiply the Thrust/MW of the Thermal Turbojet parts by (7.24/0.6656) = 10.8774 Also, I saw that "MaxThrust" is currently only set too 300 kN for both the 1.25 meter and 2.5 meter Thermal Turbojets in their part confisg (although that value *MIGHT* be overwritten by KSP-Interstellar, because I'm fairly sure I've seen much higher Thrust values coming from Thermal Turbojets already...) Still, it might be necessary to up-rate the part's MaxThrust value by 10.8874 times its current value as well (to 3263 kN), if that has any actual significance, to maintain the original balance... Summary/Conclusions: - Thermal Turbojets currently have *MUCH* too low a Thrust/MW rating compared to realistic values, and are not as competitive with current Thermal Rockets in-game as a result (their Thrust/MW is actually currently *inferior* to a Thermal Rocket- when it should be MUCH higher due to their low Exhaust Velocity). - Thermal Turbojets were PREVIOUSLY competitive with Thermal Rockets, but the buffs of Thermal Rockets to match real-world performance specs have made them inferior. A buff is required to match real-world performance specs and make them competitive again. - Thermal Turbojet Thrust/MW should be multiplied by 10.8774 in order to match real-world values and return competitiveness. - Thermal Turbojet Maximum Thrust values should probably also be up-rated by a comparable amount to retain original balance. - Thermal Turbojets have low ISP (and thus require large amounts of Intake Air for their Thrust), operate poorly at high altitudes, and can only operate up to a MAXIMUM speed of around Mach 5- so this will *NOT* make for free ascents to orbit, *ESPECIALLY* when playing with RealSolarSystem Regards, Northstar

FreeThinker, Also, I decided to go and write up some specific fixes for the ISRU refineries so that they will now have RealFuels modular fuel-tanks, which will be insulated (and solve the current boil-off issue with the tanks *not* being insulated). This will allow players to select BEFORE launching a rocket what types of resources they want to give their ISRU refinery storage for- which is a complaint Dreadicon and some other players made to me in the past (that they couldn't customize their refinery for the usages they had planned for it). Going to Dres, for instance? No need for a Water tank- but adding lots of UF4 storage would be nice! The following code should also be added to the "RealFuelsFix" file: @PART[FNRefinery]:FOR[RealFuels] { MODULE { name = ModuleFuelTanks volume = 1750 type = Cryogenic } } @PART[FNInlineRefinery]:FOR[RealFuels] { MODULE { name = ModuleFuelTanks volume = 1750 type = Cryogenic } } @PART[FNInlineRefineryLarge]:FOR[RealFuels] { MODULE { name = ModuleFuelTanks volume = 11000 type = Cryogenic } } The volumes for each have been *PRECISELY* determined to match the RealFuels convention of multiplying existing stock tank capacity by 5 (as the RealFuels resources are MUCH less dense, and stock parts typically only have about 1/5th the capacity they should have in liters...) Regards, Northstar

FreeThinker, So, a minor issue I stumbled across recently- Duna has *very* small amounts of Oxygen it its atmosphere (0.13% abundance). ATMOSPHERIC_RESOURCE_DEFINITION { name = DunaOxygen guiName = Oxygen celestialBodyName = Duna resourceName = Oxidizer abundance = 0.0013 } Yet it's not currently possible to scoop it with a Propulsive Fluid Accumulator (while simultaneously scooping Carbon Dioxide) in RealFuels, as there is no config change of Oxidizer --> LqdOxygen. Since there currently no way to obtain Oxygen directly from the CO2 resource, the ability to scoop this residual Oxygen could prove *very* important... I suggest adding the following code to the RealFuelsFix file: @ATMOSPHERIC_RESOURCE_DEFINITION[DunaOxygen] { resourceName = LqdOxygen } Ideally this should go at the end of the current list of Atmosphere Resource Pack changes, like so: @ATMOSPHERIC_RESOURCE_PACK_DEFINITION[InterstellarAtmosphericPack]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @ATMOSPHERIC_RESOURCE_DEFINITION[KerbinOxygen] { resourceName = LqdOxygen } @ATMOSPHERIC_RESOURCE_DEFINITION[KerbinHydrogen] { resourceName = LqdHydrogen } @ATMOSPHERIC_RESOURCE_DEFINITION[JoolHydrogen] { resourceName = LqdHydrogen } @ATMOSPHERIC_RESOURCE_DEFINITION[LaytheOxygen] { resourceName = LqdOxygen } @ATMOSPHERIC_RESOURCE_DEFINITION[DunaOxygen] { resourceName = LqdOxygen } } Also, we need to get ISRU reactions to convert CO2 --> O2 eventually. The *BEST* reactions for this are: CO2 Electrolysis: CO2 --> C (solid) + O2 Reverse Water Gas Shift Reaction + Water Electrolysis: 2 CO2 + 2 H2 --> 2 CO + 2 H2O --> 2 CO + 2 H2 + O2 In both cases, you would have a waste-product you simply dump overboard: Graphite with the CO2 Electrolysis reaction, and Carbon Monoxide with the Reverse Water Gas Shift Reaction... ALTHOUGH, it should be mentioned that Carbon Monoxide is itself a potentially useful gas- it can be used to manufacture Kerosene via the Fischer-Tropsch Process in combination with Hydrogen, and can be combusted with Oxygen for a VERY low-ISP chemical rocket (around 180-200 seconds ISP, if my memory serves correctly) for suborbital hops around Mars/Duna... Both ISRU reactions can *EASILY* be selectively carried out in Mars-like conditions with relatively light/compact (space-grade) refineries, and are in fact currently being developed/researched (the primary engineering challenge is in gathering CO2 from the Martian atmosphere in the first place, as it is so thin- luckily Duna's atmosphere is MUCH thicker...) for fuel-production and life-support reasons on future Mars missions... Regards, Northstar

I was a little put-off by the fact that it's been over a month since FreeThinker's pull-request, and it still hasn't been accepted (whereas many other *more recent* pull-requests have been). As I said, not all KSP-Interstellar users play with the Extension Config (in fact, most don't). So the *best* solution would just be to update the config here from time-to-time, as we continue to develop it there... Regards, Northstar

Drakoflame, I think the problem you're struggling with is that Boris changed the solar panel code back on Christmas of last year to be *more realistic* in that solar panels now generate heat more slowly (because their backsides also act as large heat-radiators). While his implementation wasn't *perfect* (the WasteHeat production picks up sharply about the point where you get to Eve), the change was a *marked improvement* over the pre-existing situation... Solar panels *do* still generate WasteHeat even around Kerbin- I think what you're missing is that the body of your spacecraft also acts a large (and inefficient) heat-radiator. Currently, any spacecraft it KSP-Interstellar will radiate WasteHeat back into space at a rate directly-proportional to its total mass. This was a clumsy attempt to model a spacecraft's surface-area, much like the stock drag-model originally (currently) modeled/models drag as increasing proportional to spacecraft mass (fortunately, this is finally being replaced with a more realistic/intuitive drag-model in KSP version 1.0) The fact is, heat doesn't just radiate out of heat radiators- it also radiates off the entire skin of a spacecraft (although the sun-facing side of the spacecraft also absorbs some sunlight, the net balance of absorption vs. radiation favors a relatively cool resting-temperature for most spacecraft- around -40 Celsius for a passive body in Low Earth Orbit, where it's being bombarded with Infrared radiating off the Earth...) So, if you have only a couple small solar panels on a relatively large spacecraft, you wouldn't EXPECT it to overheat quickly. Even on a relatively small satellite in Low Earth Orbit, with comparatively large deployable solar panels, the solar panels themselves act as heat radiators (out their backside), so you usually don't have a *drastic* problem with heat management (a *very* small active radiator will do) unless the solar panels become VERY large relative to the spacecraft... Look at it this way- most spacecraft are designed to maximize passive heat-radiation, and absorb as little sunlight as possible. That's why the surfaces of many spacecraft are painted white, and have intentionally high albedos... Most solar panels absorb only a few Watts of sunlight per square-meter. How hot do you *think* the spacecraft would have to get before the rate of heat-radiation out the backside equaled a few Watts from a small set of solar panels? Now if you attach something the size of a Gigantor to a tiny probe, you'll still get overheating, even near Kerbin. THAT is realistic... Are you *SURE* you still want to change the system back to how it was before, even if it's unrealistically-harsh? Regards, Northstar - - - Updated - - - Drakoflame, I think the problem you're struggling with is that Boris changed the solar panel code back on Christmas of last year to be *more realistic* in that solar panels now generate heat more slowly (because their backsides also act as large heat-radiators). While his implementation wasn't *perfect* (the WasteHeat production picks up sharply about the point where you get to Eve), the change was a *marked improvement* over the pre-existing situation... Solar panels *do* still generate WasteHeat even around Kerbin- I think what you're missing is that the body of your spacecraft also acts a large (and inefficient) heat-radiator. Currently, any spacecraft it KSP-Interstellar will radiate WasteHeat back into space at a rate directly-proportional to its total mass. This was a clumsy attempt to model a spacecraft's surface-area, much like the stock drag-model originally (currently) modeled/models drag as increasing proportional to spacecraft mass (fortunately, this is finally being replaced with a more realistic/intuitive drag-model in KSP version 1.0) The fact is, heat doesn't just radiate out of heat radiators- it also radiates off the entire skin of a spacecraft (although the sun-facing side of the spacecraft also absorbs some sunlight, the net balance of absorption vs. radiation favors a relatively cool resting-temperature for most spacecraft- around -40 Celsius for a passive body in Low Earth Orbit, where it's being bombarded with Infrared radiating off the Earth...) So, if you have only a couple small solar panels on a relatively large spacecraft, you wouldn't EXPECT it to overheat quickly. Even on a relatively small satellite in Low Earth Orbit, with comparatively large deployable solar panels, the solar panels themselves act as heat radiators (out their backside), so you usually don't have a drastic problem with heat management unless the solar panels become VERY large relative to the spacecraft... Look at it this way- most spacecraft are designed to maximize passive heat-radiation, and absorb as little sunlight as possible. That's why the surfaces of many spacecraft are painted white, and have intentionally high albedos... Most solar panels absorb only a few Watts of sunlight per square-meter. How hot do you *think* the spacecraft would have to get before the rate of heat-radiation out the backside equaled a few Watts from a small set of solar panels? Now if you attach something the size of a Gigantor to a tiny probe, you'll still get overheating, even near Kerbin. THAT is realistic... Are you *SURE* you still want to change the system back to how it was before, even if it's unrealistically-harsh? Regards, Northstar

This is a re-post from the KSP-Interstellar 0.90 port maintenance thread, to help us start migrating the conversation here from there: Water (H2O) has 9 times the Molecular Weight of Hydrogen: so it's ISP should be approximately 1/3rd that of Liquid Hydrogen- corresponding to an ISP multiplier of 0.33 based purely on Molecular Weight. HOWEVER, water also engages in Hydrogen Bonding- which reduces its ISP relative to Molecular Weight even further (because a given amount of heat-injection won't raise its temperature as high, leading to lower Exhaust Velocity), so a more accurate value would be around 0.25-0.28 However, it is CURRENTLY set at 0.4714 instead. I'm not sure why this is- most of Fractal_UK's other ISP multiplier selections are accurate to the molecular weight and physical/chemical properties... The same effect is observed for Ammonia, which also engages in Hydrogen Bonding, and has an ISP multiplier of 0.6503 instead of the expected value of 0.342 based on molecular weight, or 0.30-0.32 after accounting for Hydrogen Bonding. My guess is Fractal_UK used a higher ISP multiplier to account for the reduced thrust observed with Water and Ammonia relative to the expected Thrust/MW based on their molecular weight (in fact, he gives this explanation on the KSP-I wiki). HOWEVER, what Fractal_UK did NOT seem to grasp is that the lost Thrust *DOES NOT* show up as a higher ISP/Exhaust Velocity. Water and Ammonia are just poor NTR fuels to use, period. The only advantages of Water/Ammonia is that, due to their Hydrogen Bonding, they are HIGHLY storable. As in, at the ambient temperatures of space both will *FREEZE* into a SOLID rather than attempt to boil-off into a vapor like LH2 or LOX... However, boil-off is not currently modeled in KSP-Interstellar (it *IS* in RealFuels, however, and indeed neither fuel experiences boil-off with that mod installed, unlike Hydro/LOX...) Thanks for catching that EMPeror? I assume that's why you asked me to calculate the proper ISP for Water... @FreeThinker The ISP multipliers of Water and Ammonia need to be reduced to the following values: Water: 0.33 Ammonia: 0.342 Also, there needs to be a *NEGATIVE* (less than 1) Thrust-modifier on both Water and Ammonia that *REDUCES* their EFFECTIVE ISP to 0.28 and 0.30, respectively. Here are the appropriate Thrust modifiers to attain that: Water: 0.900 Ammonia: 0.875 So, Water should produce only 90% of the expected Thrust for its Molecular Weight and ISP, and Ammonia only 87.5%. Regards, Northstar Also, Freethinker, you asked about LF/O mix before. I want to make sure you correctly understand, the Thrust-increase of 200% is *RELATIVE TO HYDROGEN ALONE*. Here are appropriate Thrust/ISP values for a LANTR fuel-mode, drawn DIRECTLY from the table on page 7 of the report you linked to: LH2/LOX ISP multiplier: 0.6289 (so, an ISP 62.89% of Hydrogen with a given reactor temperature and nozzle-size) LH2/LOX Thrust Multiplier: 3.1444 (314.44% Thrust relative to Hydrogen) # EDIT: Initial calculations for the ISP multiplier were too low, because I divided 566/1000 instead of 566/900 to determine the relative-ISP of LANTR fuel-mode. *PLEASE* use the new value of 0.6289 above. So, if a NTR in LH2-mode produces a Vacuum Thrust of 1.15 kN/MW at a Vauum ISP of 1150 seconds... (this is *approximately* the correct value at a reactor temperature of 3000 K, with a Vacuum-nozzle attached, and what we have been balancing the Sethlans family of reactors to with equal-diameter Thermal Rocket Nozzles) Then it should produce 3.62 kN/MW of Vacuum Thrust at a Vacuum ISP of 732.22 seconds when using LH2/LOX. Another issues to be aware of- LANTR DOES *NOT* OPERATE AT STOICHIOMETRIC RATIOS FOR LH2/LOX COMBUSTION! According to the first report on LANTR you linked, the fuel mass-ratio at the *HIGHEST* LOX-injection ratio (where you get a full 314.4% increase in Thrust relative to LH2 alone) is only 1:4, *not* the 1:8 stoichiometric ratio, or the 1:6 fuel-ratio you would see with a typical Hydrolox chemical rocket engine. Seeing this, the fuel-ratio RealFuels/KSP-I needs to be changed *SIGNIFICANTLY*. The fuel/ox ratio is stock KSP-I is currently 10:11, clearly to match the existing rocket-fuel mix, and I wouldn't recommend changing this as it will make things too difficult on new players. HOWEVER, RealFuels seeks to match real-world fuel mixtures and performance whenever possible (this is basically the entire purpose of that mod), so the current RealFuels Hydro/LOX fuel-mode ModuleManager patch needs to be changed as follows... Here is the current code, found in the "RealFuelsFix" config now included with KSP-Interstellar Extension Config: @BASIC_NTR_PROPELLANT[Hydrolox]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @guiName = Hydrolox @PROPELLANT[LiquidFuel] { @name = LqdHydrogen @ratio = 0.73 } @PROPELLANT[Oxidizer] { @name = LqdOxygen @ratio = 0.27 @DrawGauge = False } } Now *HERE* is what the code NEEDS to be changed to: @BASIC_NTR_PROPELLANT[Hydrolox]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @guiName = Hydrolox @PROPELLANT[LiquidFuel] { @name = LqdHydrogen @ratio = 0.80 } @PROPELLANT[Oxidizer] { @name = LqdOxygen @ratio = 0.20 @DrawGauge = False } } You'll notice that the LANTR fuel-mode causes thermal rockets to now burn significantly more Hydrogen-rich. Which is GREAT for Propulsive Fluid Accumulators around Jool, but bad for the size of your spacecraft in RealFuels... (due to Hydrogen's *VERY* low fuel-density) I'll also try and re-post this on the new thread for the KSP-Interstellar Extension Config, as we start to migrate more discussion to over there... Regards, Northstar

I'm aware of the desire to get ScanSat working with KSP-Interstellar, although some players (like myself) can't play with it due to its extensive RAM and CPU requirements... However, Regolith is simply not up to the task of some things accomplished by ORS in KSP-Interstellar... What I mean is, if you change the "resource" density of a resource in the configs (like we *currently* do with the KSP-Interstellar/RealFuels integration config- there is literally no other way to do it, since KSP-Interstellar's default resource-densities bear no relation whatsoever to reality in many cases...) then parts that extract that resource from the ground/air/etc. (like the KSP-Interstellar ISRU Refinery) will automatically adjust the units/minute they extract of that resource to harvest the resource at the same mass-extraction rate... I've played with Karbonite before, so I know what those terms mean. The resource abundance is essentially equivalent to the resource concentration *in the ground* in ORS/KSP-Interstellar. The "efficiency" parameter relates to how quickly that resource is extracted relative to the concentration/abundance, and as I understand it, is capped at 100%. BOTH these parameters need to continue to exist in some form in KSP-Interstellar, regardless of whether it uses Regolith or ORS for the majority of its In-Situ-Resource-Utilization needs. HOWEVER, an *ADDITIONAL* calculation needs to be performed that corrects extraction-rates based on config changes to the resource-density. KSP-Interstellar automatically does this with ORS (so if I change "LiquidFuel" into "LqdHydrogen", for instance, the extraction-rate remains the same on a kg/minute basis, even though I have decreased the resource-density more than 500-fold!) Don't get me wrong, it is POSSIBLE to separately calculate a new base extraction-rate for the resource, or simply multiply the abundance 500x fold or what-not using Regolith, but doing so would be much more complex and much trickier (with a lot more potential to screw up) than the system that currently exists with ORS. Given these difficulties, it seems it would be *MUCH* easier to try and figure out how to get ORS to work with ScanSat, than to try and code around Regolith's clumsy responses to changes in resource-density... That's the thing. We would have to change conversion-ratios and/or consult with Roverdude for *EVERY SINGLE CHANGE* we make to replace a resource-density if we switched over to Regolith. With ORS, it's much simpler, you just give it a mass:ratio (say, electrolysis of Water produces 88.88% Oxygen and 11.11% Hydrogen by mass) and it automatically adjusts resource-consumption based on *any possible change* you could ever make to resource-densities at a later point. *WITHOUT* a ModuleManager patch. ORS makes it MUCH simpler to tweak densities, create cross-mod compatibility, or even just re-name a resource (it keeps a catalog of the "name" for each resource type, i.e. there is a "Water resource name" which could be "Water" or "LqdWater" or "Liquid Water" and they would all be functionally-identical with a simple MM patch to change the name in that catalog...) than does Reglolith. Don't get me wrong, I love Regolith- it has its place/purpose, and some things it does better than ORS- and that's why we use it for the Propulsive Fluid Accumulators, for instance- because it already had some very nice code fro scooping resources from the edge of an atmosphere while in time-warp. But it simply is *NOT* up to meeting the bulk of the needs of KSP-Interstellar, which is the mod Fractal_UK coded ORS around in the first place... It was meant to be humorous. Sorry if it came across a little dickish... Trust me- it's all in good fun, I value your input Tellion. Regards, Northstar

@NathanKell Since responses have been *extremely slow*, and change *NOT* forthcoming for fixing the RealFuels/KSP-Interstellar integration-config (FreeThinker submitted a pull-request *over a month ago* to fix some aspects of that config- whatever happened to that?) a copy of it has been included natively in KSP-Interstellar Extension Config, which builds on the 0.90 port of KSP-Interstellar made by Boris-Barboris, and continues to be actively-developed there. I say this not to criticize, but to remind you that change is continuing onwards to improve cross-mode compatibility and realism, and RealFuels needs to keep up. I hope you won't let any personal grudges you may hold (which I really haven't done anything to deserve, to be honest) get in the way of long-term progress here... Of course, not all players who utilize KSP-Interstellar also utilize the Extension Config (*yet*- I'm hoping to eventually get it integrated back into the original KSP-Interstellar mod when Fractal_UK returns to full activity status), so it would *still* be preferable to see the integration-config updated here from time-to-time. Here is the complete and most current revision of the integration-config, with all sorts of good changes made since branching off what can currently be found in RealFuels. I would appreciate it if you could get around to replacing the current (outdated) config with it eventually (or an even newer version that may develop in the coming days/weeks if you don't pick this up soon...) //Interstellar-RealFuels configs @WARP_PLUGIN_SETTINGS[*]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @HydrogenResourceName = LqdHydrogen //LiquidFuel @HydrogenPeroxideResourceName = HTP //H2Peroxide @AmmoniaResourceName = LqdAmmonia //Ammonia @OxygenResourceName = LqdOxygen //Oxidizer } //Add water tank using KSPI water. (TO-DO: integration with TACLS water without trampling KSPI or TACLS) @TANK_DEFINITION[*]:FINAL:HAS[@TANK[Kerosene],!TANK[LqdWater]]:NEEDS[RealFuels]:FOR[WarpPlugin] { +TANK[Kerosene] { @name = Water } } //Add Argon to all tanks that have XenonGas, as they function and store similarly. @TANK_DEFINITION[*]:FINAL:HAS[@TANK[XenonGas],!TANK[Argon]]:NEEDS[RealFuels]:FOR[WarpPlugin] { +TANK[XenonGas] { @name = ArgonGas } } //Add CO2 tank using KSPI gaseous CO2 to all tanks that have Nitrogen. @TANK_DEFINITION[*]:FINAL:HAS[@TANK[Nitrogen],!TANK[CarbonDioxide]]:NEEDS[RealFuels]:FOR[WarpPlugin] { +TANK[Nitrogen] { @name = CarbonDioxide } } //Add LiquidCO2 to all tanks that have LqdMethane, as they store similarly. @TANK_DEFINITION[*]:FINAL:HAS[@TANK[LqdMethane],!TANK[LiquidCO2]]:NEEDS[RealFuels]:FOR[WarpPlugin] { +TANK[LqdMethane] { @name = LiquidCO2 } } //Add LiquidNitrogen to all tanks that have LqdOxygen, as they store similarly. @TANK_DEFINITION[*]:FINAL:HAS[@TANK[LqdOxygen],!TANK[LiquidNitrogen]]:NEEDS[RealFuels]:FOR[WarpPlugin] { +TANK[LqdOxygen] { @name = LiquidNitrogen } } //Part catch-all updates @PART[*]:HAS[@RESOURCE[Ammonia]]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @RESOURCE[Ammonia] { @name = LqdAmmonia } } @PART[*]:HAS[@RESOURCE[H2Peroxide]]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @RESOURCE[H2Peroxide] { @name = HTP } } //Resource Definition updates @OCEANIC_RESOURCE_DEFINITION[*]:FINAL:HAS[#resourceName[Ammonia]]:NEEDS[RealFuels]:FOR[WarpPlugin] { @resourceName = LqdAmmonia } @ATMOSPHERIC_RESOURCE_DEFINITION[*]:FINAL:HAS[#resourceName[Ammonia]]:NEEDS[RealFuels]:FOR[WarpPlugin] { @resourceName = LqdAmmonia } @OCEANIC_RESOURCE_DEFINITION[*]:FINAL:HAS[#resourceName[H2Peroxide]]:NEEDS[RealFuels]:FOR[WarpPlugin] { @resourceName = HTP } @ATMOSPHERIC_RESOURCE_DEFINITION[*]:FINAL:HAS[#resourceName[H2Peroxide]]:NEEDS[RealFuels]:FOR[WarpPlugin] { @resourceName = HTP } @ATMOSPHERIC_RESOURCE_PACK_DEFINITION[InterstellarAtmosphericPack]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @ATMOSPHERIC_RESOURCE_DEFINITION[KerbinOxygen] { resourceName = LqdOxygen } @ATMOSPHERIC_RESOURCE_DEFINITION[KerbinHydrogen] { resourceName = LqdHydrogen } @ATMOSPHERIC_RESOURCE_DEFINITION[JoolHydrogen] { resourceName = LqdHydrogen } @ATMOSPHERIC_RESOURCE_DEFINITION[LaytheOxygen] { resourceName = LqdOxygen } } //NTR Propellant updates @BASIC_NTR_PROPELLANT[Ammonia]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @guiName = Ammonia @PROPELLANT[Ammonia] { @name = LqdAmmonia } } @BASIC_NTR_PROPELLANT[Hydrolox]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @guiName = Hydrolox @PROPELLANT[LiquidFuel] { @name = LqdHydrogen @ratio = 0.80 } @PROPELLANT[Oxidizer] { @name = LqdOxygen @ratio = 0.20 @DrawGauge = False } } @BASIC_NTR_PROPELLANT[Methalox]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @PROPELLANT[Oxidizier] { @name = LqdOxygen @ratio = 0.557 } @PROPELLANT[LqdMethane] { @ratio = 0.443 } } @BASIC_NTR_PROPELLANT[Hydrogen]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @guiName = LqdHydrogen @PROPELLANT[LiquidFuel] { @name = LqdHydrogen } } //Electric Propellants update @ELECTRIC_PROPELLANT[Ammonia]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @PROPELLANT[Ammonia] { @name = LqdAmmonia } } @ELECTRIC_PROPELLANT[Hydrogen]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @guiName = LqdHydrogen @PROPELLANT[LiquidFuel] { @name = LqdHydrogen } } @ELECTRIC_PROPELLANT[MonoPropellant]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @guiName = Hydrazine @PROPELLANT[MonoPropellant] { @name = Hydrazine } } //Remove duplicate entry for LqdMethane !RESOURCE_DEFINITION[LqdMethane]:FINAL:HAS[#density[0.00186456]]:NEEDS[RealFuels]:FOR[WarpPlugin] { @density = 0.00042262 } //Specific part fixes @PART[FNMethaneTank*]:FINAL:HAS[@RESOURCE[LqdMethane],@RESOURCE[Oxidizer],!MODULE[ModuleFuelTanks]]:NEEDS[RealFuels]:FOR[WarpPlugin] { MODULE { name = ModuleFuelTanks temp = 0 volume = 0 type = Cryogenic @temp = #$../RESOURCE[LqdMethane]/maxAmount$ @temp *= 4.412 @volume = #$temp$ @temp = #$../RESOURCE[Oxidizer]/maxAmount$ @temp *= 5 @volume += #$temp$ !temp = 0 } !RESOURCE[LqdMethane] {} !RESOURCE[Oxidizer] {} } @PART[*]:FINAL:HAS[@MODULE[FNModuleResourceExtraction]]:NEEDS[RealFuels]:FOR[WarpPlugin] { @MODULE[FNModuleResourceExtraction]:HAS[#resourceName[Ammonia]] { @resourceName = LqdAmmonia } } //NOTE: the ratio might be kinda screwy; this should really go in an engines config. @PART[AluminiumHybrid1]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @MODULE[ModuleEngines] { @PROPELLANT[Oxidizer] { @name = LqdOxygen @ratio *= 5 } } @RESOURCE[Oxidizer] { @name = LqdOxygen @amount *= 5 @maxAmount *= 5 } } @PART[vista]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @MODULE[ModuleEngines] { @PROPELLANT[LiquidFuel] { @name = LqdHydrogen @ratio *= 14.114 } } } Regards, Northstar

Hi Raptor, Great to see you're trying to figure out the KSP-Interstellar Magnetic Nozzle fuel-overwrite issue. I've been working on improving Nuclear Thermal Rocket realism over in KSP-Interstellar (surprisingly, the TWR and ISP were *TOO LOW* for more recent/modern real-world performance specs, as found with projects such as the Strategic Defense Initiative's Project Timberwind and the US Air Force Space Nuclear Thermal Propulsion Program...) Anyways, one issue I came across is that the LOX-Augmented Nuclear Thermal Rocket (LANTR) fuel-ratios were messed up when using the KSP-I/Realfuels integration config for Hydro/LOX fuel-mode with NTR's... That inspired me to take a look at the fuel-ratios for the RealFuels-Stockalike LANTR LV-N's as well, and it turns out their fuel-mixture is also messed up. HERE is the CURRENT fuel-mixture: CONFIG { name = LqdHydrogen+LqdOxygen thrustVectorTransformName = thrustTransform exhaustDamage = True ignitionThreshold = 0.1 minThrust = 0 maxThrust = 303.9466 heatProduction = 325 fxOffset = 0, 0, 1.0 // Assuming LOX / H2 ratio of 3-1 (mass) // 0.6941 Isp // volume ratio conversion // 1.141 kg LOX (1L) x3 // // 1.141 kg LH2 (16.10444601270289L) // mixture ratio by mass: // = 0.003423 kg O2 // = 0.001141 H2 PROPELLANT { name = LqdHydrogen ratio = 16.10444601270289 DrawGauge = True } PROPELLANT { name = LqdOxygen ratio = 3.0 DrawGauge = False } PROPELLANT { name = U235Rods ratio = 0.00000000001 } atmosphereCurve { key = 0 642 key = 1 386 } IspSL = 0.6941 IspV = 0.6941 } However, as can be found in THIS document on LANTR, the CORRECT fuel mass-ratio in a LANTR is *NOT* 3:1 for a roughly 200% thrust-increase, as the config assumes... The correct fuel mass-ratio is 4:1 for a 214.44% thrust-increase (so Thrust should be 349.6573 kN instead of 303.9466 kN). CURRENT Vacuum Thrust: 303.9466 kN CORRECT Vacuum Thrust: 349.6573 kN This means that the LANTR fuel-mode should burn significantly more LOX-rich (which reduces problems with the boil-off and fuel-density of having large amounts of LH2). But it's not ALL sunshine and rainbows- the current Specific Impulse is also too high... According to the document, the Specific Impulse should only be 62.88% of LH2 alone, not the 69.41% currently used in the config. This means that the Vacuum ISP needs fixing... Here are the values at Tech-Level 5: CURRENT Vacuum ISP: 642 CORRECT Vacuum ISP: 581.7 The Sea-level ISP is too low, though... This is because the way atmospheric-compression works (which can be *APPROXIMATELY* modeled by the formula Atmospheric Thrust = Vacuum Thrust - Exit Area * Ambient Pressure) you see a more or less constant decrease in Thrust for a given nozzle size/shape and exhaust gas composition (the specific heat capacity of the exhaust gasses affects the result) regardless of the Thrust or Mass Flow Rate (however the higher the Vacuum Thrust and Mass Flow Rate is for a given nozzle, the relatively smaller this compression-effect is compared to total Thrust, due to higher Exhaust Pressure...) So, you see a thrust-loss to atmospheric compression of 44.58 kN for Hydrogen-only fuel-mode at Tech Level 5 at sea-level. You see a thrust-loss to atmospheric compression of 121.20 kN for LH2/LOX at Tech Level 5 at sea-level, although I AM *EXTREMELY* SURE THIS NUMBER IS INCORRECT, as *at most* you should see a maybe 50-60 kN of Thrust when running the LV-N in LANTR mode at sea-level (the Thrust-loss is greater due to lower exhaust gas specific heat capacity...) So, there are two methods to determine the CORRECT sea-leve ISP. One is to assume the current atmospheric-compression loss for LH2/LOX is correct, but the Vacuum Thrust level was wrong. This leads to an only *slight* DECREASE in calculated sea-level ISP, as the Vacuum ISP was too high previously... The other, better-supported (by real world equations) method is to assume an only slightly-increased atmospheric-compression loss for LH2/LOX compared to LH2 alone, AS THEY HAVE THE EXACT SAME ROCKET NOZZLE- in which case you see a *large* increase in sea-level ISP... Once again, at Tech-Level 5 (the values given in the config, with rules given on how tech-level increases it...) CURRENT Sea-Level ISP: 386 seconds CORRECTED Sea-Level ISP by method #1: 380.07 seconds CORRECTED Sea-Level ISP by method #2: 481.88 seconds (assumes a 60 kN thrust-loss due to atmospheric-compression) Of course, all these values are working within the bounds of Tech-Level 5 LV-N Trimodal engines. Which is great for NERVA-era performance (where a TWR of between 1 and 2 was the best that could be expected), but *PATHETIC* compared to modern-era NTR performance (where Project Timberwind designs looked set to achieve a Vacuum TWR of 30 with just pure Hydrogen, and at a Vacuum ISP of 1000 seconds!) This goes more into the issue of Thrust increasing *MUCH* too gradually with increases in LV-N tech-level than it does with any fundamental flaw with the part/system... The fact is, Nuclear Thermal Rockets have seen *MUCH* more drastic improvements in design performance with improvements in technology than chemical engines over the past 50 years... This REALLY ought to be modeled in the Stockalike config (i.e. the final tech-level should yield a TWR of around 25-30, even if the initial tech-level TWR is only 1-2...) Regards, Northstar - - - Updated - - - But why even *BOTHER* adding the nightmare-fuels to RealFuels if there are no engines that actually use them in-game? In that case, it just clutters the interface, and is a waste of programming effort. What's the point??? Regards, Northstar - - - Updated - - - You couldn't work at least a *few* of the new fuel-modes in? In THAT case, I would really prefer if you just found some way to remove them with Stockalike... Anyways, regarding engine re-scales/balances, what about NovaPunch2? People always seem to talk about KW Rocketry and FASA here like they're the ONLY game in town, but NovaPunch has been around a *LOT* longer than either of these up-starts, is *still* quite popular and under active development (thanks to Tiberion), and actually has analogs for a *lot* of the same real-life engines and engine-roles as KW Rocketry (in some cases, KW Rocketry may have even blatantly ripped-off engine ideas from NovaPunch...) Personally, I don't use KW Rocketry or FASA. I'm a NovaPunch man... Regards, Northstar

Also, Freethinker, you asked about LF/O mix before. I want to make sure you correctly understand, the Thrust-increase of 200% is *RELATIVE TO HYDROGEN ALONE*. Here are appropriate Thrust/ISP values for a LANTR fuel-mode, drawn DIRECTLY from the table on page 7 of the report you linked to: LH2/LOX ISP multiplier: 0.6289 (so, an ISP 62.89% of Hydrogen with a given reactor temperature and nozzle-size) LH2/LOX Thrust Multiplier: 3.1444 (314.44% Thrust relative to Hydrogen) # EDIT: Initial calculations for the ISP multiplier were too low, because I divided 566/1000 instead of 566/900 to determine the relative-ISP of LANTR fuel-mode. *PLEASE* use the new value of 0.6289 above. So, if a NTR in LH2-mode produces a Vacuum Thrust of 1.15 kN/MW at a Vauum ISP of 1150 seconds... (this is *approximately* the correct value at a reactor temperature of 3000 K, with a Vacuum-nozzle attached, and what we have been balancing the Sethlans family of reactors to with equal-diameter Thermal Rocket Nozzles) Then it should produce 3.62 kN/MW of Vacuum Thrust at a Vacuum ISP of 732.22 seconds when using LH2/LOX. Another issues to be aware of- LANTR DOES *NOT* OPERATE AT STOICHIOMETRIC RATIOS FOR LH2/LOX COMBUSTION! According to the first report on LANTR you linked, the fuel mass-ratio at the *HIGHEST* LOX-injection ratio (where you get a full 314.4% increase in Thrust relative to LH2 alone) is only 1:4, *not* the 1:8 stoichiometric ratio, or the 1:6 fuel-ratio you would see with a typical Hydrolox chemical rocket engine. Seeing this, the fuel-ratio RealFuels/KSP-I needs to be changed *SIGNIFICANTLY*. The fuel/ox ratio is stock KSP-I is currently 10:11, clearly to match the existing rocket-fuel mix, and I wouldn't recommend changing this as it will make things too difficult on new players. HOWEVER, RealFuels seeks to match real-world fuel mixtures and performance whenever possible (this is basically the entire purpose of that mod), so the current RealFuels Hydro/LOX fuel-mode ModuleManager patch needs to be changed as follows... Here is the current code, found in the "RealFuelsFix" config now included with KSP-Interstellar Extension Config: @BASIC_NTR_PROPELLANT[Hydrolox]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @guiName = Hydrolox @PROPELLANT[LiquidFuel] { @name = LqdHydrogen @ratio = 0.73 } @PROPELLANT[Oxidizer] { @name = LqdOxygen @ratio = 0.27 @DrawGauge = False } } Now *HERE* is what the code NEEDS to be changed to: @BASIC_NTR_PROPELLANT[Hydrolox]:FINAL:NEEDS[RealFuels]:FOR[WarpPlugin] { @guiName = Hydrolox @PROPELLANT[LiquidFuel] { @name = LqdHydrogen @ratio = 0.80 } @PROPELLANT[Oxidizer] { @name = LqdOxygen @ratio = 0.20 @DrawGauge = False } } You'll notice that the LANTR fuel-mode causes thermal rockets to now burn significantly more Hydrogen-rich. Which is GREAT for Propulsive Fluid Accumulators around Jool, but bad for the size of your spacecraft in RealFuels... (due to Hydrogen's *VERY* low fuel-density) I'll also try and re-post this on the new thread for the KSP-Interstellar Extension Config, as we start to migrate more discussion to over there... Regards, Northstar

Water (H2O) has 9 times the Molecular Weight of Hydrogen: so it's ISP should be approximately 1/3rd that of Liquid Hydrogen- corresponding to an ISP multiplier of 0.33 based purely on Molecular Weight. HOWEVER, water also engages in Hydrogen Bonding- which reduces its ISP relative to Molecular Weight even further (because a given amount of heat-injection won't raise its temperature as high, leading to lower Exhaust Velocity), so a more accurate value would be around 0.25-0.28 However, it is CURRENTLY set at 0.4714 instead. I'm not sure why this is- most of Fractal_UK's other ISP multiplier selections are accurate to the molecular weight and physical/chemical properties... The same effect is observed for Ammonia, which also engages in Hydrogen Bonding, and has an ISP multiplier of 0.6503 instead of the expected value of 0.342 based on molecular weight, or 0.30-0.32 after accounting for Hydrogen Bonding. My guess is Fractal_UK used a higher ISP multiplier to account for the reduced thrust observed with Water and Ammonia relative to the expected Thrust/MW based on their molecular weight (in fact, he gives this explanation on the KSP-I wiki). HOWEVER, what Fractal_UK did NOT seem to grasp is that the lost Thrust *DOES NOT* show up as a higher ISP/Exhaust Velocity. Water and Ammonia are just poor NTR fuels to use, period. The only advantages of Water/Ammonia is that, due to their Hydrogen Bonding, they are HIGHLY storable. As in, at the ambient temperatures of space both will *FREEZE* into a SOLID rather than attempt to boil-off into a vapor like LH2 or LOX... However, boil-off is not currently modeled in KSP-Interstellar (it *IS* in RealFuels, however, and indeed neither fuel experiences boil-off with that mod installed, unlike Hydro/LOX...) Thanks for catching that EMPeror? I assume that's why you asked me to calculate the proper ISP for Water... @FreeThinker The ISP multipliers of Water and Ammonia need to be reduced to the following values: Water: 0.33 Ammonia: 0.342 Also, there needs to be a *NEGATIVE* (less than 1) Thrust-modifier on both Water and Ammonia that *REDUCES* their EFFECTIVE ISP to 0.28 and 0.30, respectively. Here are the appropriate Thrust modifiers to attain that: Water: 0.900 Ammonia: 0.875 So, Water should produce only 90% of the expected Thrust for its Molecular Weight and ISP, and Ammonia only 87.5%. Regards, Northstar

Why do people keep asking about using Regolith? Let's be clear- the Karbonite/Regolith system is NOT well-adapted to some of the things KSP-Interstellar does. It has many important/useful features Regolith doesn't, like auto-adjusting the resource extraction rate based on resource-density (important for RealFuels compatibility). Under-the-hood ORS/CRP is a better, if more complex and harder to program with, system- it just needs a better interface for players to locate resource-deposits than it currently has. It's good for SOME things- that's why the Extension Config currently uses BOTH ORS *AND* Regolith, one for normal resources and the other for Propulsive Fluid Accumulators. But Regloith does simply NOT do some things as well as ORS/CRP. So, -1000 for Regolith since I've been helping to develop the Extension Config, and there are a lot of things we still have yet to do with it that wouldn't work properly with the Regolith system... Regards, Northstar