Northstar1989

OK, this is confusing. Tweakscale (which only goes up to 1.5.0) or Freescale (which doesn't have a numbering system at all)? Which works? Which is recommended? This is one reason I've never used TweakScale/FreeScale before- there are all sorts of issues even figuring out what VERSION works... Regards, Northstar

Ya' know, there actually *IS* a use for having that many Kerbals in orbit. Have you ever heard of Extraplanetary Launchpads? If you filled that station with Kerbals, it would actually have quite an impressive construction capability (in EPL, rockets take TIME and PARTS to manufacture off-world: and the more Kerbals you have at the spacedock/launchpad, the faster it build things). It wouldn't be too late to retrofit that station with a spacedock part via the docking port, so that you could use your existing station for orbital construction... Normally I consider EPL a little cheaty, as it doesn't seem realistic for a tiny 3-man station to build a giant rocket in orbit, even if it takes them 5 years. But if you went through all the effort of building a 96-man Stanford Torus (that's what that type of station-design is actually called), you should go right ahead- you deserve to be able to build rockets in orbit (our of parts hauled from the ground), and it wouldn't be unrealistic! One of the *MAJOR* advantages of building things in orbit is that you can build spacecraft that are so fragile/large they could NEVER survive the g's and aerodynamic forces of a launch from the KSC... Like, a long stack of Mass Drivers (see my signature for a working Mass Driver mod I maintain), or an even larger Stanford Torus! Regards, Northstar - - - Updated - - - That's pretty cool - - - Updated - - - Also, here are some pictures from development of a line of HIGHLY SUCCESSFUL Ares-style (SRB first-stage, heavy HydroLox upper-stage) launch vehicles I was developing in RealSolarSystem 64K... (a 6.4x scale-up of Kerbin and the Kerbol system) There were nonetheless a few reverts, as I like to tweak my Launch Vehicles until they have PRECISELY enough fuel and performance to meet the mission objectives, no more, no less, at the minimal possible Funds cost... (money rules the universe!) Oh, and, I got a launcher this heavy off the level-2 pad by a clever workaround for SQUAD's 140-ton mass limit (which, for SILLY REASONS they hardcoded, so we're not allowed to mod or change it)- I have RealFuels installed, and the LaunchClamps are set to fill the tanks with fuel *AFTER* the rocket is already on the pad (kind of like real life, actually- we don't roll giant rockets out to the pad on a crawler while full of highly-explosive rocket fuel!) The night-launch was of a stock Mobile Research Lab and a Mk1-2 cockpit (which detached and returned to Kerbin) for a Station contract and some experience getting into orbit for my Kerbals (this was EARLY in a new 0.90 Career game, after a previously save-breaking bug from accidentally deleting ModuleManager when trying to update it... I started with a LOT of starting Science and Funds as a result, as I didn't want to have to repeat the whole early-game grind for too long...) The day-launch was of an orbital fuel depot. I am using RealFuels, so the things on the outside are radiators to help keep the fuel (Liquid Hydrogen and Oxygen) nice and cool... There are solar panels as well, but during launch they're shielded inside the Procedural Fairings interstage-fairing... Regards, Northstar

Yeah, it's because sea-level ISP now varies with Mass Flow Rate- and thus, Exhaust Pressure (like in real life!) There's no way for the game to predict your sea-level ISP until it knows how many MW of ThermalPower you will have available... So it's not a bug, but a "feature". Maybe it's possible to create some sort of interface where you could input a given # for ThermalPower, and see what your sea-level ISP would be- but it seems a little beyond our scope/capabilities for the moment... (FreeThinker, feel free to correct me if I'm wrong, of course!) Are they now? I'm guessing FreeThinker left them in there so as to not break save-compatibility, which isn't a bad idea considering the change is new. They should probably go in a "Legacy Parts" folder, though, and be HIDDEN from the parts catalog so they can't be added to new rockets when TweakScale is installed- which I think should be re-distributed with the Extension Config... (I haven't had time to update yet today, as the update was only a # of hours ago- but I could be wrong, maybe they're already in a legacy folder!) Regards, Northstar

You are correct. I look forward to the fix! So... TweakScale is not re-distributable? I assume that if we replaced the reactors with just two sizes, we really should be including a re-distributed copy of it with the KSP-I Extension Config, if that's allowable... Great! It looks like this is all wrapped up quite nicely! Next, we just need to get to some of the other issues on that list I posted earlier (which I collated for your convenience and my organization- since it was getting a little hard to keep track of which issues had and had not yet been fixed...) A lot of them require coding expertise beyond my meager abilities (but certainly not beyond yours!), but I'll see what I can't contribute in code and in research whenever possible! The list stated on THIS post, by the way, and continued on in the next few posts: http://forum.kerbalspaceprogram.com/threads/104943-0-90-KSP-Interstellar-port-maintance-thread?p=1744095&viewfull=1#post1744095 Regards, Northstar - - - Updated - - - Also, set "MAXIMUM" core temperature to 3000 CELSIUS? I hope you mean set MINIMUM core temperature to 3000 KELVIN! The particle bed reactors produce ZERO THERMALPOWER at their *MAXIMUM* temperature. The Timberwind reactors produced their full rated thrust at 3000 K- they would have operated even hotter than that when producing sub-optimal thrust. Also, there is a *BIG* difference between 3000 Celsius and 3000 Kelvin, although I assume (hope) that was just a typo... All temperatures given in KSP-Interstellar are normally in degrees Kelvin (what the "K" on the context menu stands for), not Celsius. Regards, Northstar

That's AWESOME Freethinker! I had no idea you were working on that! I don't use TweakScale, though Maybe I'll have to give it a try now... One concern though- I see the Vacuum Thrust decreases with smaller nozzle sizes (like it should) but the Vacuum ISP doesn't yet decrease with smaller nozzle sizes- AND NEEDS TO. Right now, you're magically reducing your fuel-flow in Vacuum with smaller nozzles when what it SHOULD do is decrease your Vacuum Thrust for the same fuel flow with smaller nozzles (and decrease Vacuum ISP as a result). The inverse also applies- increasing nozzle radius should increase Vacuum Thrust and Vacuum ISP, at the expense of having a higher ExitArea (and thus reduced sea-level performance). Regards, Northstar - - - Updated - - - So, does this require a separate TweakScale installation to work? What will happen if I don't have it separately installed? Does the tweakable-sized reactor get better ThermalPower/kg and per cubic-meter of volume like the earlier reactors did? If not, it needs to have its scaling adjusted so that, for instance, a 2.5 meter reactor will produce MORE than 8 times the ThermalPower of a 1.25 meter reactor (it is radius * radius * height = 2*2*2 = 8 times larger- so 8x the ThermalPower would only be a direct scaling...) Also, I see no mention of LiquidCO2 as a new resource anywhere in the complete changelog, even though you added it in a while ago, and the KSP-I/RealFuels integration config with the changes I added that comes with KSP-I Extension Config allows players to store it with an RealFuels tank (although we're still all waiting on that universal tank you talked about so players can store LiquidCO2 *without* RealFuels installed...) Regards, Northstar

Pages 41-42 of the PDF (Pages 39-40 of the report, due to the title pages not being counted). "Because the temperature of the hydrogen is 3000 K versus 2400 K for the NERVA reactor, the propellant efficiency is much higher." OK, technically that's the EXHAUST temperature- which means the reactor *CORE* temperature has to be significantly higher (because you can't assume perfect thermodynamic efficiency, there must be a temperature difference between the exhaust and the heat exchanger, and the reactor core and the heat exchanger...) But I couldn't find data on the reactor CORE temperature anywhere in the report... Does a 3200 K core temperature sound reasonable? In which case, we need to reduce the ISP multiplier EVEN FURTHER to still get the correct Vacuum ISP of 1100-1150 seconds with the larger exhaust nozzle. Also, I would suggest creating "legacy" versions of the part instead if you're worried about breaking saves. That way, it will be easier to phase them out in the long run, when most players are now using the new version of the part. It's a shame the technology didn't survive in real life. As the report/audit reveals, Strategic Defense Initiative was supposed to transfer the technology to the US Air Force, where it would have been used alongside the Space Nuclear Thermal Propulsion program- but *somehow* many of the documents never made it to the Air Force (politics are complex and treacherous- most likely somebody interfered because they considered nuclear thermal propulsion a waste of money and wanted to kill the program...) Regards, Northstar - - - Updated - - - Your data seems about right- a LH2/LOX multiplier (and METH/LOX multiplier) of about 1.8 seems correct based on the data. Go for it! I love the idea of requiring usage of RealFuels Liquid Hydrogen (which is much less dense than LiquidFuel), however this would create a requirement of installing RealFuels for players to use this mod. I think Community Resource Pack (which comes with KSP-Interstellar) has a version of LH2, though- I know that when I actually select propellant modes for my Thermal Rocket Nozzles there are currently two differently-named versions of Hydrogen that show up, in addition to LiquidFuels (which reminds me, we *REALLY* need to implement code to phase out the LiquidFuel mode showing up when RealFuels is installed... Kethane should also only show up if Kethane is installed. It makes it harder to switch fuel-modes in-flight when all these useless fuel-modes from stock or other mods show up on the Thermal Rocket Nozzle...) Regards, Northstar - - - Updated - - - That's with the FIXED Thrust, which you've been testing but not yet released. With the version currently in the release, the Vacuum Thrust is only about 105 kN, and the sea-level Thrust is only about 40 kN (due to a proper relationship between Atmospheric Thrust and Ambient Pressure not yet being implemented for Thermal Rocket Nozzle like with the Plasma Thrusters- it defaults to Atmospheric ISP and Thrust being 40% of Vacuum ISP and Thrust, REGARDLESS OF THRUST LEVELS). With 40kN of Thrust, the TWR is even lower- only about 2. If the Thrust/Pressure code were implemented for Thermal Rocket Nozzles, and we got the proper sea-level Thrust of around 890 seconds, then we would get 89 kN of Thrust without fixing the Thrust/MW- which is only a TWR of about 4, and still USELESS for a launch vehicle (typical launch engine TWR's in real life exceed 80- even the REAL Timberwind was anemic by comparison). Only if we fixed the Thrust/MW *and* reduced the reactor+nozzle mass to the realistic value for its size of 625 kg (Timberwind 75 was 4x larger and weighed 2500 kg) would we get the realistic TWR of 30. I think we should leave the cost alone. It is already *DRASTICALLY* out-performed by chemical engines (a LV-30 costs 314 Funds in RealFuels+Stockalike, and 850 funds in stock, but produces over 200 kN of Thrust, for instance). The costs were originally too high for the performance- buffing the performance w/o increasing the costs brings them more in line with realistic values (a Timberwind reactor would NOT have cost almost 20x a chemical rocket engine + turbopump with the same Thrust). Regards, Northstar - - - Updated - - - Also, once we're done with the Thermal Rockets, we *REALLY* need to take a look at buffing the Thermal Turbojets. Currently, like the Thermal Rocket Nozzles, the Thermal Turbojets produce only a *FRACTION* of the Thrust/MW they SHOULD be producing in real-life. We don't have any great #'s on the Thrust/MW of a TTJ in real life (as no Thermal Turbojet has ever actually flown- only been designed/tested on the ground), but we *DO* know the approximate Exhaust Velocity based on the ISP of the part. If we know the Exhaust Velocity (which is directly proportional to ISP), we can calculate the correct Thrust at any given ThermalPower level. From that, we can calculate what the Thrust/MW *should* be based on a known Thrust/MW of slightly less than 1 kN/MW for a Timberwind NTR at 1000 seconds ISP... (so, if the ISP is 200 seconds for a Thermal Turbojet, the Thrust/MW should be approximately 5 kN/MW based on the mathematical relationships we already know, for instance...) Regards, Northstar P.S. I just wanted to remind you of something. The performances of some of the KSP-Interstellar parts *ARE* going to seem a bit unbalanced/broken with realistic values when you compare them to some of the stock parts. That is NOT because there is any problem with the real values (they are *INHERENTLY* balanced, because that's how it really DOES work). It's because you're basing your *assumptions* on what constitutes a "balanced" part on the ABSURDITY of a planet 1/11th the radius of Earth but with an atmosphere and the same surface-gravity. OF COURSE that's not going to work out to real-life performance seeming balanced: it only takes 4.5 km/s to make orbit in stock KSP and 3.5 km/s with FAR, whereas in real life it takes 9 km/s JUST TO MAKE ORBIT, and even more to get anywhere else in the solar system (as the interplanetary distances in KSP are also scaled-down...) However KSP-Interstellar already has a number of parts balanced against real life (including the Alcubierre Drive, *FOR WHICH THE MOD WAS FIRST CREATED*). I *strongly* believe Fractal_UK instituted the values he did for some of the fission reactors and such simply because he didn't have access to any reliable data on how the technology had *GREATLY ADVANCED* since the days of NERVA (they are very much in line with NERVA performance). It doesn't make sense to stop using realistic values now- rather, if players want "balanced" gameplay, they should go and also install a version of Real Solar System (personally, I play with the 6.4x scale-up, as it's the best balanced against stock part sizes- which are only 40-50% the diameter of their real-life cousins in most cases...) I don't have any problem with players having an "easier" time of the game with the stock solar system, though. If they want to play with a tiny-scale model solar system using little green men, then that's their prerogative. *LET THEM* have their dramatically easier gameplay than real-life, if that's what they really want... Personally, I prefer something a *little* more realistic.

Awesome. But, upon careful review of your solution, I realized (or rather, was reminded of in the case of one) TWO major problems that I didn't mention before... Reducing the reactor temperature makes it much harder to dissipate the WasteHeat produced by the reactor. Because radiators in KSP-Interstellar (and real life) radiate heat based on the FOURTH POWER of their temperature (temperature^4), and the maximum temperature they can reach is that of the vessel's reactor core (interestingly enough, I've never tried seeing what would happen to the radiators if I placed two different reactors with different core temperatures on the same vessel...) having a slightly more than 10% lower core-temperature like that DRASTICALLY increases the minimum radiator-mass necessary to keep the reactor from overheating... Thus, I *strongly* suggest you keep the current (realistic) core temperatures and ThermalPower values, and decrease the ISP multiplier and increase the Thrust/MW instead (until a Thermal Rocket Nozzle produces approximately 1 kN/MW with a 3000 K heat-source) like I originally suggested. There is a second, even larger problem with not fixing the Thrust/MW properly and reducing the reactor core temperatures instead (and using an excessively high ISP-multiplier to still get the correct ISP for the reactor-type it is simulating...) NOT FIXING THE THRUST AND ISP MULTIPLIERS PROPERLY WILL *BADLY* MESS UP MICROWAVE THERMAL ROCKETS You see, if you keep the ISP multiplier too high and the Thrust multiplier too low, like in that solution, you will end up with Microwave Thermal Rockets producing *MUCH* less Thrust/MW at a significantly higher Vacuum ISP (but significantly LOWER Atmospheric ISP- due to the reduced Vacuum Thrust ratings that will result) than they should be doing... This is a *HUGE* problem for Microwave Thermal Rockets because their main use (in fact their ONLY proposed use in real-life) is as launch-vehicles, as you lose almost all of the beamed-power due to beam-diffraction when trying to beam the power over, say, interplanetary distances... (or even to a rocket in orbit that is not DIRECTLY overhead, due to the atmosphere accelerating beam-diffraction) If you hurt both the Thrust (both Vacuum and Atmospheric) and Atmospheric ISP of Microwave Thermal Rockets, they will become nearly worthless for their intended purpose- as launch vehicles. Their Thrust/MW will be far too low (thus requiring much more beamed-power to get usable levels of Thrust), and their maximum Thrust rating will also suffer as well (as their maximum Thrust is limited by the number of MW of beamed-power a given Thermal Receiver can absorb, not in terms of kN of Thrust). Their Atmospheric ISP will also consistently be too low, as their Vacuum Thrust ratings will be much lower as well. BOTH the high ISP multiplier and the low Thrust multiplier will hurt the Thrust-performance of Microwave Thermal Rockets. Due to the way Thrust is calculated in KSP-Interstellar (ThermalPower is divided by ISP, and then multiplied by the Thrust multiplier), BOTH terms will diminish the Thrust/MW of the Microwave Thermal Rockets- and their overall performance as launch-vehicles will be abysmal compared to what it *SHOULD* be... Once more, here are the necessary changes to the Thrust Multiplier and ISP Multiplier: Thrust Multiplier: Increase 2x from current value ISP Multiplier: Decrease from current value (over 22) to 21. Sorry I didn't realize the effects of not keeping the correct reactor core temperatures and fixing the Thrust/ISP multipliers on Microwave Thermal Rockets and radiator-efficiency earlier... Regards, Northstar - - - Updated - - - Also, one more possible way to improve the Extension Config to add to the list: (5) Fix the ISP-cap (as implemented by Fractal_UK) to be more realistic. ISP should cap at 7000 seconds instead of 3000 seconds when using Hydrogen in second-generation fission reactors such as Gas Core Reactors (based on literature on the maximum exhaust temperatures that can safely be achieved with Nuclear Thermal Rockets, as briefly paraphrased in THIS Wikipedia article), and the ISP cap should be proportionally lower for heavier fuels as outlined HERE. As I stated, you DO NOT need a property inside KSP-Interstellar for the molecular mass of the different propellants- that is already intrinsically reflected in the Thrust and ISP-multipliers relative to Hydrogen of each of the propellants. Similarly, the ISP cap will be a constant value for any given propellant, as Molecular Mass is a constant, unchanging value for any given propellant... Regards, Northstar

Also, here's a list of possibilities for future growth of the Extension Config: (1) The ability to manufacture N2O4, Nitrous Oxide, and Hydrogen Peroxide from the Nitrogen, Oxygen, and Hydrogen gasses. You already mentioned wanting to do this HERE and I got back to you about it HERE. In stock KSP-I you simply use LiquidFuel to represent Hydrogen and Monopropellant to represent Hydrazine, in keeping with existing conventions. Hydrogen Peroxide can already be manufactured in KSP-I, but not directly from Hydrogen and Oxygen as is BY FAR the most common cycle in real life (in KSP-Interstellar it instead requires Oxygen/Oxidizer and Water). Hydrazine/Monopropellant can be manufactured from Ammonia and Hydrogen Peroxide in KSP-Interstellar, like in real life, but IIRC there is still no way to manufacture the requisite Ammonia from Nitrogen and Hydrogen in KSP-Interstellar (like in the Haber process) (2) Various additional RealFuels-related fixes. Specifically, the ISRU Refinery needs to have CRYOGENIC rather than Default built-in fuel tanks for its resources (to reduce boil-off to reasonable levels), the ISRU Refinery needs to produce "Hydrazine" instead of "Monopropellant" with the RealFuels module ModuleRCSFX installed (it comes in a separate folder from the main install, and is an optional addition that replaces Monoprop with realistic RCS fuels the same way the base mod replaces LF/O with realistic rocket fuels...), and the dedicated Ammonia tank needs to have its resource-capacity increased approximately 5-fold when RealFuels is installed (generally speaking, most fuel tanks require a 5-fold increase in capacity when RealFuels is installed, as stock resource-capacities are approximately 18% of the volume of their tanks in liters due to the VERY high density of stock resources) when holding RealFuels "LqdAmmonia" instead of KSP-I "Ammonia"... Finally, last but not least, some code is needed to stop RealFuels "Stockalike" engine config from replacing ChardedParticles with KEROSENE for the Magnetic Nozzles, as shown HERE. (3) Introduction of the Haber Process, and allowing the Sabatier Reaction to be carried out using the new CO2 resource in combination with Hydrogen/LiquidFuel (I provided the mass-fractions you requested for this HERE) (4) Fixing the display of the ISP multiplier in the VAB/SPH so that players see the CORRECT isp multiplier instead of the archaic (and inaccurate) value of 17... Fiing the display of Thrust/MW so it is also accurate to the currently-set Thrust multiplier value from the config (or at least to the default value, which was already up-rated from the original KSP-I). Also, keep in mind that to achieve the *CORRECT* sea-level performance for a Timberwind-style Nuclear Thermal Rocket of around kN/MW when using Liquid Hydrogen, we still need to uprate the Thrust/MW for the Thermal Rocket Nozzles approximately 2-fold. The Sethlans-family reactors are currently *COMPLETELY USELESS* as launch-engines due to their low Thrust-Weight Ratio (currently only about 4 for the "Sethlans" in the release), and as I explained HERE even with the CORRECT Thrust/MW for the Thermal Rocket Nozzles of about 1 kN/MW at 3000K, you would still only get a TWR of about 8 (compared to 30 for the Timberwind NTR's) due to the reactors weight 4x what they should for their size (volume) and power-production... Achieving the correct Thrust/MW for the Thermal Rocket Nozzles is *ESSENTIAL* to proper simulation of Microwave Thermal Rockets, which also rely on the Thermal Rocket nozzles. How else am I supposed to demonstrate to naysayers that Microwave Thermal Rocketry is indeed possible in real life by showing them an accurate simulation of it in KSP-Interstellar if the Microwave Thermal Rockets require 2x the Microwave Power in order to produce the same Thrust as in real life? (I've been in some extensive discussions about the viability of Microwave Thermal Spaceplanes in THIS thread, for instance...) ALSO, a BUG. EEK! The current density of the LiquidCO2 resource is off by a factor of 1000x (YIKES!) It is currently: 0.000001200 It *SHOULD* be: 0.001200 The current density of the LiquidCO2 resource is THREE orders of magnitude off! For reference, the current density of LiquidNitrogen is 0.000824907 (which is accurate), and LiquidCO2 is supposed to be around 50% denser than LiquidNitrogen! (just think about the relative Molecular Masses: 44 vs. 28) I originally provided the correct density figure HERE (note that in KSP, resource-density is in mT/liter, i.e. a resource of density "2" would weigh two tons for ever unit of the resource... 1000 liters of Liquid CO2 *should* weigh 1.2 tons, not 1.2 kilograms as you currently have it configured) Regards, Northstar

@FreeThinker What does this entry in the Changelog mean? "Reactor displays required upgradeTech" Also, when are you planning on adding in the Thrust/MW fixes to the Thermal Rocket Nozzles you presented before? The Thrust still needs to be about 2x what it is in the current release, and the ISP multiplier is a bit high. Earlier you presented a fix that reduced reactor-temperature (to lower ISP) as well as increased the Thrust multiplier, but I haven't seen it make it into the releases yet... Here's the post where you presented the needed re-balance that still hasn't made it into the releases: http://forum.kerbalspaceprogram.com/threads/104943-0-90-KSP-Interstellar-port-maintance-thread?p=1728813&viewfull=1#post1728813 Regards, Northstar

Some additional advantages to a Methane-kicker: (3) Methane has much higher boiling-point (-161.5 Celsius) than H2 (-252.9 Celsius), making it much easier to store long-term. You can get away with less insulation on the fuel tanks of a launch vehicle containing Methane (reducing mass), and it becomes more feasible to store reserve fuel from the uppermost stage of the rocket or from a spaceplane in orbital fuel depots long-term for use beyond LEO (to boost satellites to Geostationary orbits, for instance). (4) Because Methane Thermal Rockets have a higher Exhaust Pressure than Hydrogen you can utilize a larger engine nozzle in-atmosphere. The ideal rocket nozzle size expands the exhaust stream until it equals ambient pressure, and with a higher pressure to work with before the nozzle, the ideal nozzle size becomes larger. The larger your rocket nozzle becomes, the more you increase your Exhaust Velocity with the nozzle, and the higher your Specific Impulse and Thrust both become. Thus, while a Thermal Rocket using Methane as propellant might produce 3 times the Thrust at sea-level as a Thermal Rocket using Hydrogen as propellant with the same size nozzle, a Thermal Rocket using Methane at optimal expansion-ratio will generate significantly MORE Thrust at a higher Specific Impulse for the same Mass Flow Rate due to the higher Expansion-Ratio of the optimal nozzle... Of course, since a Thermal Rocket is fuel-agnostic, there is nothing stopping you from using MORE than two types of propellant for even BETTER performance. For instance, you could do something like this: CO2 --> N2 --> CH4 --> H2 As you'll notice, each progressive change in fuel-mode has a lower Molecular Mass that the one before it. This is actually a very clever way of effectively staging the rocket's propulsion (even though there's nothing stopping you from switching fuels like this is a spaceplane or SSTO, and no actual separation of stages may be involved), as each fuel-component will be heavier than the one after it... Here are the Thrust values of each propellant (note that the Vacuum ISP is in all cases the inverse of the relative Thrust, i.e. Methane has SqRt(8) time the Thrust and 1/SqRt(8) times the ISP compared to H2...) starting with the values for Hydrogen as a benchmark: H2 Thrust: approx. 1 kN/MW Vacuum ISP: 850 - 1000 seconds CH4 Thrust: approx. 2.82 kN/MW Vacuum ISP: 300 - 354 seconds (*before* accounting for larger nozzle compared to Hydrogen- actual performances of 320-360 seconds are expected) N2 Thrust: approx. 3.74 kN/MW Vacuum ISP: 227 - 267 seconds (larger values expected after accounting for larger nozzle) CO2 Thrust: approx 4.69 kN/MW Vacuum ISP: 181 - 213 seconds (larger values expected after accounting for larger nozzle) EDIT: EEK! I made a major calculation-error and forgot to divide the Molecular Mass by 2 (the Molecular Mass of diatomic Hydrogen) before calculating the Thrust and ISP of N2 and CO2- resulting in excessively high #'s for Thrust and low #'s for ISP for these two propellants. Now fixed. Note that although the optimal nozzle size increases with increasing Molecular Mass of the propellant, the optimal nozzle size *also* increases with ALTITUDE- meaning that if you start off with heavier propellants at lower altitude, and work your way to lighter propellants as you ascend, you can keep the same nozzle the whole way through the ascent- as the decreasing ambient pressure will make up for the decreasing Exhaust Pressure... In every case, replacing a lighter fuel with a heavier fuel makes sense approximately UP UNTIL THE POINT where you end up with the same TWR for the heavier propellant as if you had just stuck with the lighter propellant. Thus, replacing H2 with CH4 makes sense up until your rocket has 2.82 times the mass as if you had stuck with just Hydrogen, replacing CH4 with N2 makes sense up until you would have 1.87 (5.29/2.82) times the total rocket mass as if you had stuck with just Methane, etc. At the point where your initial TWR for the denser propellant is equal to your TWR for the lighter propellant, your Ballistic Coefficient will be higher (and thus atmospheric-drag losses lower), your rocket will require less insulation (although ideally you would include the reduced insulation requirements in calculating the new TWR and deciding how much lighter propellant to replace with the heavier one), and your time-to-orbit (and thus gravity-losses) will be shorter (as your TWR will increase more rapidly due to your lower Specific Impulse and thus proportionally higher Mass Flow Rate with the heavier fuel, and less of your velocity will be eaten up by atmospheric-drag due to your higher Ballistic Coefficient). Thus, when using heavier propellants for the initial stages of your ascent, your Delta-V requirements to orbit will be reduced, and you will have more Delta-V available with the same sized rocket (allowing your overall rocket to be smaller) despite the lower Specific Impulse (your payload-fraction will decline, but your payload-capacity will increase...) There are a few drawbacks that need to be taken into account, though: With a spaceplane, your wing-load will increase when swapping in heavier fuels (and you will need larger wings to bring it back down- this must also be taken into account when calculating the new TWR using the heavier propellant). However this has the side-benefit that you will have a lower wing-load when you get to the next (lighter) fuel-mode in line, which will make it EASIER to continue to gain altitude/speed... With a rocket, your structural mass will increase due to the higher weight of the heavier propellants, as each stage must support the mass of the stages above it (and once again, this must be taken into account when calculating how much lighter propellant is ideal to replace with a denser propellant...) However, this has the side-benefit of making stages safer/easier to recover after jettisoning them- as you will no longer have to contend with the weight of the full fuel tanks or the stages above, and your structure will be stronger relative to the outside forces exerted upon it... (a lower stage that was designed to support 400 tons of rocket above it will be much stronger than one that was only designed to support 100 tons of rocket in stages higher up...) Regards, Northstar

I wanted to explain the Methane-Kicker thing a little better, so here goes my best shot... Methane gets 2.82 times the Thrust/MW in vacuum due to the following equations: E = 1/2 m v2 Thrust = Mass Flow Rate * Exhaust Velocity - Exit Area * Background Pressure The first of these equations describes the relationship between energy and mass/velocity, and can be used to *approximate* the relationship between the Molecular Mass of a propellant and the Exhaust Velocity (there are also components for the specific heat capacity of the propellant and the expansion-ratio of the engine nozzle in the equation for Exhaust Velocity, with the heavier fuels having lower specific heat capacity but a larger optimal expansion-ratio at any given ambient pressure, so let's just ignore those for now and say this equation is all we need...) The second equation describes the relationship between Mass Flow Rate, Vacuum Specific Impulse (which is equal to the Exhaust Velocity divided by "g", i.e. 9.8 m/s^2), ambient atmospheric pressure, and the size of the rocket nozzle (the "Exit Area"). You'll notice that for a given-sized rocket nozzle, the losses to atmospheric-compression are constant for a given ambient pressure- so the difference between Vacuum ISP and Sea-Level ISP are based on the relationship between Vacuum Thrust (MAss Flow Rate * Exhaust Velocity) and nozzle size (Exit Area). Anyways, if you assume that you heat two different propellants to the same temperature, then you can set the Energy/molecule of propellant equal for two different propellants, and you get the following: m1 * v12 = m2 * v22 If you do out the math, then the ratio of Exhaust Velocities becomes approximately the following for two propellants at the same temperature: v1/v2 = SqRt (m2/m1) and the ratio of Vacuum Thrust: Thrust2/Thrust1 = m2v2/m1v1 = SqRt (m2/m1) *THIS* is where the number than Methane produce 2.82 (the square-root of 8) times the Thrust/MW of H2 comes from (where molecular masses are valued at 16 and 2, respectively), as well as that Methane only has (1/2.82) times the Vacuum ISP. Now, back to the question-at-hand: how does any of this apply to using a "Methane Kicker" in Thermal Rocketry? Well, let's say you have enough Thrust to keep a 20 ton rocket or spaceplane ascending at the desired rate with LH2 as the propellant in the atmosphere. Now, what happens if you replace the FIRST 5 TONS of LH2 with an equivalent volume of Liquid Methane? (which is approximately 8 times denser/liter) You now have a rocket that weighs 55 tons, however the Thrust-Weight Ratio is actually GREATER thanks to getting 2.82 times the Thrust from Methane (the rocket fuel only weighs 2.75 times as much, and the dry mass is the same). Of this mass, 40 tons is Liquid Methane, and 15 tons in LH2. What's more, this same rocket actually has slightly more Delta-V for the same sized rocket as well: because 40 tons of Methane produces more Delta-V than 5 tons on LH2 (the TWR starts off just as high as with the 5 tons of LH2, and you have the same burn-time, but you lose mass much more rapidly, leading to a higher TWR later in the Methane-powered portion of the flight: as much as 2.82 times as high *just before* you run out of Methane). Now whoa, whoa Northstar, you might say: "why not replace the entire 20 tons of LH2 with Liquid Methane then?" Well, you *COULD*, but then you'd get the following... Rocket Mass: 160 tons Relative Thrust: 2.82 Relative TWR: 0.3525 So, if your rocket would have the a much lower TWR, and most likely would not have enough Thrust to make it off the launchpad or continue to hold altitude as a plane... Your time-to-orbit would dramatically increase at the very least (ALTHOUGH your Ballistic Coefficient would DRAMATICALLY improve- and you would lose much less Delta-V to atmospheric drag with your rocket), and most likely you would end up needing a lot more Delta-V (and a bigger rocket) to get there as a result... There are a couple more considerations that favor Methane, however: (1) Methane produces *MORE* than 2.82 times the Thrust of Hydrogen in-atmosphere. This is because, due to the much higher Vacuum Thrust of Methane (2.82 times as high, remember) but having the same (or a similar) sized rocket-nozzle (the optimal nozzle-size *optimizes* to a larger size, but you get 2.82 times the Vacuum Thrust with the same nozzle- I can explain that later if you guys want) you end up with a much better ratio of Vacuum Thrust to Exit Area * Ambient Pressure, and a smaller difference between Vacuum and Sea-Level ISP as a result... (another way to explain this is that the much higher Mass Flow Rate leads to a higher Exhaust Pressure...) In other words, the Hydrogen-propelled rocket/plane loses relatively more of its Thrust to atmospheric-compression, and the ratio of Thrust with Methane vs. Hydrogen grows as a result. (2) A rocket with Methane replacing some (or all) of its LH2 will have a higher Ballistic Coefficient than a rocket with just LH2, and will lose LESS Delta-V to atmospheric drag during its ascent as a result (however a spaceplane with Methane will have a higher wing-loading unless you increase the size of the wings...) Anyways, using a Methane-kicker allows you to get more Delta-V for the same fuel volume, and (with a rocket) decreases your Delta-V lost to atmospheric-drag (better Ballistic Coefficient) and gravity (shorter time-to-orbit due to slightly higher TWR and better Ballistic Coefficient). The result is a better-performing rocket (or spaceplane) with the same amount of Microwave Beamed-Power. Regards, Northstar

The sketches are just artist-renditions, and are indeed wildly-inaccurate (not surprising, really- most artists who draw about space don't even have the faintest clue about rocket-science...) And, you are also correct in that the fuel-density would be abysmal. But you are missing two thing here: (1) Unlike with Skylon, you don't have to carry any fuel for the initial ascent. You can achieve this purely with Thermal Turbojets.... (which use the atmosphere for 100% of their reaction-mass) (2) The vehicles is much lighter, so requires much less propellant to reach orbit to begin with, and less Thrust to stay airborne. A Microwave Thermal Thruster weighs much less than a SABRE engine, and your fuel to reach orbit weighs much less as well... (3) You're not limited purely to Liquid Hydrogen. You can use Liquid Methane for an initial "kicker" of higher Thrust, and save the higher-ISP Liquid Hydrogen for later in the flight. (4) Both Hydrogen and Methane will combust with atmospheric Oxygen. So it's possible to have an intermediate propulsion-mode between a purely-atmospheric Thermal Turbojet, and a Thermal Rocket driven purely by internal propellant, where you essentially have a thermally-augmented SABRE engine (that is, you pump additional heat into the exhaust stream to increase Thrust and Exhaust Velocity- allowing operation either with a greater bypass-ratio than a SABRE for the same Exhaust Velocity and thus high-speed performance...) The added complexity and mass may not be worth it for the very limited window of time where it outperforms both a Thermal Turbojet and a Thermal Rocket, however... I've considered it. No need to attack me, but go on... Correction. Takeoff is the most THRUST-demanding phase of flight. At the altitude of the runway, there is a LOT of airflow available to potentially increase your working-mass. If your air intakes are large enough compared to your engines, you can easily achieve very high ratios of working mass to input-power. Which means very high Thrust relative to your input-power at low speeds. You will need lots of Intake Area at high-altitudes anyways in order to keep enough airflow to your Thermal Turbojets (although you will also need advanced precoolers for the very high compression-ratios, which is why SABRE's new precooler designs could be IMMENSELY helpful for a Hydrogen-powered Microwave Thermal Spaceplane...) Your takeoff velocity will also be VERY low due to the incredibly low wing-loading involved in a Hydrogen Thermal Spaceplane (due to the low propellant density) with any kind of decent ratio of wing area to fuselage size. A simple rocket-sled or electromagnetic "kicker" will be enough to give your plane a burst of speed on the runway if all that still doesn't cut it. Are you talking high-bypass or low-bypass turbofans? Because there's a BIG difference... Also, I said that a Microwave Thermal Rocket is lighter than a chemical rocket, not that a Microwave Thermal Turbojet is lighter than a conventional jet-engine. See below... The lack of *WHAT* thermodynamic features? I assume you're referring to having large stores of onboard Liquid Hydrogen enabling SABRE to use that as a heat-sink for the precoolers. But as we've already discussed, a Microwave Thermal Spaceplane would ALSO have that same available heat-sink, in the form of large supplies of onboard Liquid Hydrogen (in fact, as you already pointed out, it would have MORE Liquid Hydrogen onboard, as 100% of its rocket-propellant mass would be LH2, whereas a Hydrolox Rocket carries more than 8/9ths of its propellant mass as Liquid Oxygen...) The Microwave Thermal Receivers aren't particularly heavy either- in fact, compared to a combustion chamber they're quite light. So, I would expect a Microwave Thermal Turbojet to be able to achieve a TWR of *AT LEAST* 15-20. Which isn't particularly impressive compared to a Microwave Thermal Rocket, which can achieve a TWR of over 200, but a Microwave Thermal Turbojet can produce *MUCH* more Thrust/MW than a Microwave Thermal Rocket... First of all, I think you're mixing up hypersonic and supersonic propulsion- at supersonic velocities compression-heating of the intake air is not NEARLY as large of an issue as you think, and it's still possible to pump significant amounts of heat into the working-mass (the Heat Exchanger operates at a temperature of over 2000 K- I'd like to see an intake airstream that heats *NEARLY* that hot below Mach 3). As for hypersonic propulsion (let's define this as starting at about Mach 4) you have a HUGE heat-sink in the form of Liquid Hydrogen available, and a gigantic surface-area you can pump coolant from the precooler to in order to allow it to give back its heat to the atmosphere thanks to the very low fuel-density (not all of the airframe heats up- there are parts of a hypersonic plane that are shielded from the compression-shockwave and actually remain quite cool at hypersonic velocities...) Of course, the LH2 can still only absorb so much heat before boiling off, so here is where you might want to start thinking about switching over to a fuel-consuming mode: possibly initially to a sort of microwave-augmented SABRE design (where the Microwave Thermal Receivers do their best to add heat to the exhaust gasses from a LH2/Atmosphere combustion reaction, allowing for use of a much higher bypass-ratio at the same Exhaust Velocity if enough intake air is available...), although the numbers for engine-mass and the requisite amount of airflow necessary to operate something like this might not be favorable, and then to Microwave Thermal Rocket mode. With a "hybrid" Thermal Turbojet design you would shut down airflow to some off the turbojets, and instead switch them over to passing internal fuel (Liquid Hydrogen) over the same Microwave Thermal Receiver. You would want multiple Hybrid Turbojets at this point, though, as the rockets would allow you to continue operating some of them in airbreathing-mode to higher altitude-speed by creating a ram-effect driving more airflow into the intakes... Here is the crux of the matter. I think you misunderstand the purpose of the Thermal Turbojets and the wings. They exist *NOT* to provide a significant portion of orbital velocity (indeed, you could probably only make it up to about Mach 4-5 at best using Thermal Turbojets and SABRE-style precoolers), BUT TO LIFT THE ROCKETS UP ABOVE THE THICKEST PART OF THE ATMOSPHERE TO REDUCE ATMOSPHERIC-COMPRESSION OF THE EXHAUST-STREAM. Due to the *VERY* low wing-loading of a Hydrogen-fueled design (due to the incredibly low fuel-density), you would expect to be able to reach significant altitudes even at only Mach 4-5 (or Mach 2-3 for that matter) using Thermal Turbojets alone. At that point, you would switch over to rocket-propulsion at a MUCH lower ambient pressure than if you tried to operate a Microwave Thermal Rocket right off the launchpad. Which means higher Specific Impulse for the same Exhaust Velocity and Mass Flow Rate, which means more Thrust, and more Thrust/MW. And, as the cost-limiting factor on a Microwave Thermal Spaceplane or Rocket is the cost of the Microwave Transmitters, ANYTHING you can do to improve the Thrust/MW is going to be useful. Let's say your sea-level ISP is only 360 seconds using a Microwave Thermal Rocket. But you vacuum ISP is 850 seconds! If you fly up above the thickest part of the atmosphere using Thermal Turbojets, you can more than DOUBLE your Thrust/MW! Additionally, even as a rocket-propelled plane the whole way up (which is what Escape Dynamics is actually working on- not a design using Thermal Turbojets), the Microwave Thermal Spaceplane will still have superior cost-effectiveness to a conventional rocket propelled by Microwave Thermal Thrusters. This is as the wings allow you to ascend with a TWR much less than 1. By the time you go ballistic, and actually *NEED* a higher TWR, you should be at such a low atmospheric pressure and have consumed so much of your original fuel-mass that you should EASILY be able to achieve the necessary TWR with the same amount of beamed-power that only gave you a TWR of maybe 0.2 or 0.3 when you first activated the Microwave Thermal Rockets... There is no basis for that conclusion in your arguments, and I've poked your arguments full of holes anyways... How many MW of mcirowaves do you need? Now THAT'S an interesting question... At sea-level you can get more than 1 kN of Thrust per MW using Microwave Thermal Rockets with Liquid Hydrogen (the Timberwind Nuclear Thermal Rocket designs got about this at *MUCH* higher Exhaust Velocities and Temperatures, and thus inferior Thrust/MW). Using pure Liquid Methane, you can get more than 2.8 kN of Thrust per MW- but at much lower Specific Impulse (around 300-360 seconds, so in the same range as Kero/LOX rockets, but at lower fuel-density). And, of course, your Thrust/MW is *much* better at lower atmospheric pressures... Using LOX-injection for an afterburning-effect, you can get higher Thrust than the Molecular Mass of the exhaust gasses would otherwise dictate for a purely Thermal design (Water will only net a bit over 3 kN/MW at an ISP of about 270-290 seconds, for instance- but LH2/LOX will produce significantly more Thrust for the same Mass Flow Rate and MW of Thermal Power, thus improving both Thrust/MW *AND* Specific Impulse...) The beauty of a Microwave Thermal Rocket is that it's fuel-agnostic, meaning you can easily switch from N2 (an even denser propellant with an even higher Thrust/MW but lower ISP) to Methane to LH2 fuel-modes in-flight if you want with no additional equipment. This allows you to start off with denser, lower-ISP propellants, and switch to less dense but higher-ISP propellants as your velocity increases... (thus more closely matching Exhaust Velocity to your plane/rocket's velocity for maximum energy-efficiency...) Your math is off. Do you even understand the Rocket Equation? Decreasing your Specific Impulse EXPONENTIALLY increases your total fuel-requirements, and thus your required Thrust at every point in your flight. A Delta IV (in its standard configuration) has 3,140 kN RS-68A engine for its launch stage, and weighs over 250 metric tons on the launchpad, for a liftoff TWR of roughly 1.28 with a payload-capacity of 9.42 metric tons to LEO. A comparable Microwave Thermal Rocket, on the other hand, would only require a roughly 62.8 ton rocket (official estimates of payload-fraction with one are about 15% using LH2 the whole way, due to the MUCH higher ISP) and thus only about 790 kN of Thrust on the launchpad for a slightly greater liftoff TWR. That means about $1.58 billion in Microwave Transmitters at current costs- which means it would only take about 17 launches to amortize the cost of the transmitter-array down to a cost of about $94.2 million/launch (this is actually a bit lower than the cost of a Delta IV launch). Of course, there are also R&D costs, the cost of the Microwave Thermal Rocket (the actual rocket itself is exceedingly cheap compared to a chemical rocket- as Microwave Thermal Thrusters are VERY cheap to manufacture), and the costs of propellant and electricity to worry about. So, not cheap by any means. There have only been about 28 Delta IV launches in the 12 years since it was developed, which is about the length of time the Microwave Transmitters would last before some of the units in the array started needing replacement... But it *IS* cheaper than chemical rocketry, even if only by a hair. Of course, none of this accounts for the following: (1) Microwave Transmitter costs have declined DRAMATICALLY over the past 50 years, *ESPECIALLY* the last 20. If they continue to come down (something Escape Dynamics is working very hard on, and has already had some success with in its experimental units) then the economics should only become MORE favorable. (2) Spaceplanes DON'T NEED as high a TWR as rockets to get to orbit. A 62.8 ton spaceplane doesn't need 790 kN of thrust on the runway- it can EASILY get off the ground with just 200 kN of Thrust. That means a third the cost in Microwave Transmitters just on that basis alone- and that's BEFORE you account of the fact that a Thermal Turbojet could probably achieve Thrust/MW ratings many-fold higher than Microwave Thermal Rockets... (if you can merely get *twice* the Thrust/MW with TTJ's, and climb to an altitude where your Microwave Thermal Rocket ISP using LH2 is 720 seconds instead of the 360 or seconds you get at sea-level, then you can reach orbit with less than half the power-requirements again, for only 1/6th the Microwave Transmitter costs of a rocket with the same mass on the launchpad) (3) If you include a Methane or LH2/LOX "kicker" when you first activate your rockets (REMEMBER, Microwave Thermal Rockets are fuel-agnostic, you only need additional equipment if you decide to use LOX afterburners), you can get by with EVEN LESS beamed-power, whether using a rocket or spaceplane. Your vessel mass (and Thrust requirements) will go up, but you get 2.82 (to be precise, the square-root of the ratio of the Molecular Mass of CH4 to H2) times the Thrust/MW. As your vessel mass decreases due to fuel-consumption, and your Thrust requirements go down, you then switch over to LH2 propulsion- allowing you to get by with slightly less beamed power and a significantly more compact plane/rocket (due to the higher fuel-density of Liquid Methane or LH2/LOX than pure LH2...) No, and no again. The numbers say otherwise. The pace of human progress (and future progress that is expected in Microwave Thermal Rockets to improve the performance and costs even further) say otherwise as well. Regards, Northstar

The results HAVE been replicated in vacuum. Initially they weren't, but they went back and recently (as in within the past 4 weeks) went back and replicated them in vacuum. Haven't you been following the progress/news on the subject? Regards, Northstar

Such as? That's a hand-wave in itself. Provide an example or admit you cannot and are wrong. No, it's not. We know how a car works. We DO NOT know how a Cannae/EmDrive works. You have suggested NOTHING more interesting than the results merely being wrong. It would be like a flat-earther saying "we know the world is flat, so Magellan couldn't have possibly sailed around it" and therefore rejecting his achievement EVEN AS MAGELLAN WAS SITTING RIGHT THERE IN FRONT OF HIM WITH ARTIFACTS AND FOSSILS FROM HIS VOYAGE. The Cannae/EmDrive appears to work, and no amount of your saying it "shouldn't" work will change that. So, propose an actual alternative explanation that doesn't violate known principles of physics. But I'm sure you can't do that- otherwise you already would have, and would be published and probably quite famous by now... I'm not self-appointed. I've been IQ-tested (IQ over 160- which my mother likes to lord over me as hers is over 180). And if you don't believe the test, I *have* accomplished things IN MY FIELD (which is biology). Not to mention, intelligence =/= results. I've struggled against poor success due to poor parental support (my father was abusive, and used to constantly try to make me think I would amount to nothing, for instance) and people often not liking me, for instance, which has nothing to do with my book-smarts and everything to do with my personality and luck/chance of who my parents were... I have other things I'd rather study. Like medical science- since my long-term plan is to become a surgeon. No. I will *NOT* try to have less self-confidence. Self-confidence is a good thing, and all I've EVER had to deal with my whole life is people putting me down and devaluing my accomplishments/achievements- even when (especially when) they greatly exceeded those of the people putting me down. Once again, intelligence does not equate to success. It helps, but there's also a strong element of chance and opportunity involved. Some of the smartest people ever born were born in rural India and undeveloped parts of Africa, and didn't accomplish anything until a colonialist Englishman came into their country, recognized their potential, and gave them opportunities. Obviously, my situation isn't quite as bad as their own- but it makes a point that you CANNOT judge a person's intellect purely by what they've accomplished in their life... We actually DID cover some quantum physics- it was more than just a basic physics course. That being said, much of my understanding comes from discussion/arguments (where I realize when I'm wrong, and go study the subject in more detail if so), independently teaching myself material, etc. I probably would go back and major in physics (or aerospace engineering) if I had a time-machine, since biology has not worked out well for me due to the incredibly desperate funding-situation most labs find themselves in... I still remember one lab I was in that I was doing very well in, but had not yet reached the point where I had enough experience that I could start my own projects and in any way ensure the lab's success (although the PI in Biology is the only one responsible for/ allowed to write grant-applications most of the time anyways), that ended up running out of funding and had to shut down- leaving me with nothing but a single publication from my effort there. I also haven't done very well in the game of who gets credit for the results- there have been many times where I contributed significantly to another's success, or even did a large part of the work behind their project, but got *absolutely no* credit for it: not even my name in the Acknowledgements sections of the eventual publication... That comes down to social skills- which is a different kind of intelligence. Why don't you suggest an actual theory that works, instead of simply insisting that the results MUST be wrong? One of the marks of a truly intelligent person is the ability to simultaneously entertain multiple possible explanations for a phenomenon- for instance I *do* entertain several theories where the results might simply be wrong, but also entertain this theory involving virtual-particles which is (thus far) the ONLY real explanation that has been made for how the device might actually work, even if I will concur there are some aspects of it that sound rather silly... Regards, Northstar

How? Can you name one way we would have noticed an error in our theory of how virtual particles work (and whether it is possible to push off them without expending more energy than the actual change in momentum you impart to them) prior to this? Remember, modern physics has only been around for a few hundred years. It's quite likely that there's a LOT we still don't know, and that many of our assumptions are still wrong. May I point you towards the link Rakaydos posted on materials with a negative index of refraction (I've heard of those before too, so it's not exactly new to me...) Regards, Northstar - - - Updated - - - That's just insulting. And you know NOTHING about our relative understanding of physics. I don't pretend to be a physicist, for instance, but I *am* a genius, and have taught myself a lot of physics for fun. I also have taken multiple courses in physics, and was talented enough it the subject that I was the *ONLY* student outside of physics that was recruited into a normally physics majors-only course my freshman year of college... The professor was rather hoping I would switch majors into physics, I think. Regards, Northstar

Well said. You summed this all up quite well. +1 REP for you! Regards, Northstar - - - Updated - - - I don't think a Cannae/EmDrive is going to place a significant enough strain on space-time either. Which is why I expect that the system will actually start to lose efficiency as you scale it to higher power-levels: because the appearance of new virtual particles will not keep apace with the increases of power-level, and thus you'll end up giving a relatively larger amount of energy to the same working-mass (see my discussion of Exhaust Velocity vs. Thrust) eventually approaching (from higher efficiencies) the efficiency of a photon-drive, which has the absolute worst Thrust/MW theoretically possible... Never said the acceleration was via a nozzle. This matches up with how I thought/said the acceleration occurs. The Cannae/EmDrive never actually comes in contact with most virtual particles (if it did, it would have a problem, since the entire process occurs in a closed space), rather it imparts force to them and then they disappear back out of existence before they can hit one of the walls of the resonator cavity and negate the net reaction-force placed on the Cannae/EmDrive entirely... Yeah, solar sails are a tricky subject because not all of their acceleration actually comes from bouncing photons. Some of it actually comes from interacting with the *particles* (ionized, high-temperature Hydrogen atoms which have mass) of the solar wind... I didn't realize that a solar sail harvested such a small percentage of the energy of the photons it bounces. Thanks for the information! Regards, Northstar

I *HAVE* thought that through. I was *VERY CLEAR*, you do NOT *CREATE* the mass with a Cannae/EmDrive. You may increase the appearance of virtual particles simply by virtue of having a lot of energy passing through a small space, but that energy is not EXPENDED to create the virtual particles in any way, shape, or form... No, you don't expend *ANY* energy to create the virtual particles. They appear due to energy being present, but energy is not consumed in their creation. As I've pointed out quite clearly, the more mass you divide up your energy over, the more Thrust/MW you will achieve. When you don't have to create the mass, it's like the difference between a Thermal Turbojet and an Electric Propeller (both accelerate air to generate thrust, but the propeller has much lower Exhaust Velocity, and thus generates much more Thrust/MW at low speeds...) That's accurate- you have to invest energy into virtual particles to get them to do anything useful- but once again, the Canna/EmDrive or a black hole DOES NOT INVEST ENERGY TO *CREATE* THE VIRTUAL PARTICLES. And, you're comparing apples and oranges here- the Cannae/EmDrive also loses energy, just like if you had used a photon-drive instead, but what we're measuring is not the AMOUNT of energy lost, it's how much useful work (Thrust) we derive from those particles before sending them off. Because the Exhaust Velocity is lower, you get more useful work out of accelerating virtual particles to speeds less than the speed of light than out of creating photons. You could still design a photon-drive that would consume Energy at the exact same rate as the Cannae/EmDrive, but it would produce less USEFUL work. In essence, the Cannae/EmDrive is more efficient than a photon-drive. I NEVER SAID you don't have to "pay your bill" in the end, in the form of investing energy. What I said is, the Cannae/EmDrive is more EFFICIENT than a photon-drive. It is a known fact that the most energy-efficient propulsion method (from a given frame of reference) is one that has an Exhaust velocity equal to your vehicle velocity. However, in your frame of reference, the spacecraft using the Cannae/EmDrive would not be moving at NEARLY the speed of light. So, it's more energy-efficient to create an exhaust-stream of slower-moving particles. The mass of a photon is non-existant outside of the mass imparted by its energy, and thus the photon-drive expends negligible energy creating the actual photon outside of the energy required for the photon's energy (this is why it costs less energy to create infrared light than X-rays: the entire energy-cost is invested in the energy/velocity of the photon, and none of it in the mass...) In the same way, a Cannae/EmDrive does NOT consume any energy creating the actual virtual particles, only in giving them momentum (which causes the particles to become longer-lived). Producing/exciting a stream of slower-moving particles with negligible energy-requirements to create the mass of (neither the photon-drive nor the Cannae/EmDrive expends significant energy creating particle mass- only in giving the particles energy, which in turn gives the particles some amount of mass) will be more EFFICIENT at speeds greatly less than the speed of light, as your Exhaust Velocity is closer to your spacecraft velocity. It should follow, however, that once your spacecraft accelerates a certain amount past the Exhaust Velocity of a Cannae/EmDrive, a photon-drive would become the more energy-efficient of the two (we're talking at relativistic speeds here...) No. You don't expend any energy to give the Virtual Particles rest-mass. They already had that when they appeared. Perhaps that statement is true from the standpoint of the ENTIRE UNIVERSE (if the energy to create the Virtual Particles in the first place came from somewhere else), but the spacecraft expends no actual energy creating the virtual particles, and thus is not penalized for the rest-mass of the virtual particles in any way... I think the closest analogy to what we're talking about here is ACTUALLY an electric propeller vs. a photon-drive. IF the electric-propeller had to invest the energy to create its working mass, it would be the less efficient of the two propulsion methods due to the rest-mass of its exhaust. However the electric propeller does NOT expend energy to create the rest-mass of its exhaust, and thus is far more energy-efficient at low speeds... I've said this once, I'm going to say it again. And again if necessary until you actually listen. The Cannae/EmDrive *DOES NOT, AND CANNOT* pay the bill of creating the rest-mass of the virtual particles. The Vritual Particles had rest-mass BEFORE the Cannae/EmDrive ever started acting on them, and would exist even if the Cannae/EmDrive were not there. That is why Virtual Particles are so weird- they come into existence with mass and energy WITHOUT you having to invest any energy to create them. However they then normally spontaneously pop back out of existence. The very existence of virtual particles technically, for an infinitesimally small amount of time, may violate Conservation of Energy. What a Cannae/EmDrive does is take advantage of these particles that ALREADY EXIST, and gives them momentum. Even if the particles then pop back out of existence, the reaction force has already been exerted on the Cannae/EmDrive. Who knows? Maybe the Virtual Particles pop into existence SOMEWHERE ELSE in the universe with the momentum that the Cannae/EmDrive gave them (thus preventing the Cannae/EmDrive from actually violating Conservation of Momentum). But, what a Cannae/EmDrive *REALLY* does is take advantage of the fact that VACUUM IS NOT TRULY EMPTY, not create particles to act as its propellant. Thus, it is more similar to a propeller (which acts on working mass which already exists around it) than a photon-drive (which creates the working mass it needs for its propellent). I don't argue that point. However a nuclear reactor coupled with a photon-drive... (or better yet, a Cannae/EmDrive...) Yeah, I don't disagree. A nuclear reactor is, from a certain perspective, just like a battery with incredibly high energy-density. And, if you're using an internal power-source like that, you're going to want to get the most Thrust/MW, which means YOU'RE GOING TO WANT YOUR EXHAUST VELOCITY TO MATCH YOUR SPACECRAFT VELOCITY. A photon-drive creates an exhaust-stream moving at the speed of light (with no rest-mass), and thus is much less efficient at non-relativistic speeds than a Cannae/EmDrive which acts of particles that have rest-mass but the Cannae/EmDrive imparted no energy to in order to give rest-mass to in the first place (much like a propeller does NOT expend energy to give air its rest-mass), and accelerates those particles to speeds only a fraction a speed of light. Bottom Line: ANY propulsion-system invests energy in order to achieve usable work (Thrust). The more energy is imparted to each particle of the exhaust-stream, the less of that energy is converted into usable work and the more of it remains in the exhaust. Photon-drives achieve the WORST possible ratio of usable work to energy-consumption (at non-relativistic speeds), due to their VERY high Exhaust Velocity. A Cannae/EmDrive, on the other hand, produces an exhaust stream of lower velocity, and thus harvests more usable work from it. It does NOT invest any energy to create the propellant, just like a photon-drive doesn't (the energy it invests actually all goes into the energy of the photons, NOT into creating any rest-mass) and a rocket engine doesn't. A Cannae/EmDrive actually produces LESS Thrust/MW than any chemical or thermal propulsion system, due to its much higher Exhaust Velocity- but unlike these systems it does not have to carry its propellant-mass with it, but rather utilizes Virtual Particles, that already appeared and disappeared before the Cannae/EmDrive entered that space, and will continue to appear and disappear there after the Cannae/EmDrive leaves that space... Regards, Northstar

The Mk1 cockpit is lighter and has a smaller cross-sectional area (important for drag in FAR) anyways, so I don't see why you wouldn't use it for a low-altitude plane. If you want to attach two stack-mounted intakes to the front using a Mk2 bicoupler (like I often do for my spaceplanes, as it means the nose of the plane becomes intake area- ideally/theoretically a spaceplane wants as much of its drag to be intake-drag as possible, as this will lead to the highest cruising-altitude under jet power...), or want two pilots for some reason, then just mount TWO Mk1 cockpits side-by-side, and give them both decouplers for this challenge... Yes. No vernors or internal-propellant RCS, as both can be used outside the atmosphere and are inefficient inside it (although using B9 Aerospace' compressed-air RCS is acceptable...) I see. You know you don't have to use a docking-port for the refueling criteria, right? A radial KAS winch port (the female end- which accepts winch connections) is the smallest/lightest/least draggy way to enable you to refuel your aircraft... Just make sure it's possible for Kerbals to access the port from the ground- so place it on the underside or provide a ladder to reach it... (or demonstrate a rover with a deployable ladder that can reach it) Awesome! I look forward to your entry! Regards, Northstar

Pics of that text (to show what it looks like with the fix) would still be helpful- and improve community trust in the plugin. Regards, Northstar

No pics no clicks man! Why don't you post some screenshots of the new contract-descriptions? Regards, Northstar

I don't see how that's possible, considering the rules clearly state the vessel needs to be kept up with aerodynamic lift or buoyancy... - - - Updated - - - That's a VERY cool aircraft, but sorry, it doesn't qualify for "Watch Out For the Canopy Goose!" unless the cockpit (or better yet, an External Command Seat the Kerbal has been riding in the whole time) EJECTS from the aircraft. Didn't you get the reference to the ejection-seat fiasco in TopGun? The "Atmospheric Specialty" distinction was meant to be reserved for aircraft that have no onboard rockets whatseoever (obviously meaning you need to choose between this a vying for the spaceplane-distinction). May I suggest removing the rockets if your plane doesn't need them to fly? You also need to complete "Every Nook & Cranny" with a SINGLE design- meaning if you have to retrofit the aircraft for a water-landing it doesn't count. May I suggest trying to build a VTOL (or helicopter) that can safely land on both land AND water? Regards, Northstar

The most sensible plan (to me) seems to be to have 2 transmitter arrays. A very SMALL one North-Northeast or South-Southeast of the runway. This would provide the Thrust needed for takeoff. You actually don't need a lot of beamed-power for takeoff, in fact it's the point in your ascent where you need the LEAST beamed-power. This is because you don't have to be traveling as fast to generate enough Lift to get airborne (ESPECIALLY with the Ground-Effect) as you do to stay aloft at higher altitude... The most energy-efficient Exhaust Velocity in-atmosphere is always the one where your Exhaust Velocity equals your plane's velocity, and you can achieve this at a lower Exhaust Velocity near the ground than at higher altitude. The lower your Exhaust Velocity, the more Thrust/MW you will generate, as: Thrust = Mass Flow Rate * Exhaust Velocity Energy = Mass * Velocity^2 Thus, for a fixed Mass Flow Rate (where Mass = Mass Flow Rate) and where your Exhaust Velocity = Spacecraft Velocity, you get... Thrust = (Energy/ Velocity^2) * Velocity --> Thrust = Energy/Velocity Which proves, when you are traveling lower in the atmosphere, you can get more Thrust/MW... What this actually looks like from a engine-design standpoint is that you concentrate the same amount of beamed-power into an increasingly small Working Mass by doing things like switching from high-bypass to low-bypass turbofans to turbojets to rockets, shutting down engines (and concentrating the available beamed-power into a smaller number of engines operating at higher temperature), and possibly even using Electric Propellers (operating off Microwave Beamed-Power via rectennas) to get off the runway in the first place... Given the different optimal engine designs for different speeds/altitude, an argument could be made for a multiple-stage spaceplane design (such as a Microwave Thermal Tubojet lower-stage that releases an orbiter at max cruising altitude which operates entirely off Microwave Thermal Rockets), although for the smaller-scale payloads that will probably compose most of the launch-diet with this technology early on (until people trust it enough to use it to launch astronauts!) it probably just makes more sense to design for high altitudes and speeds, as you only *just barely* need to be able to make it off the Runway with your Thermal Turbojets... Anyways, so you use a small transmitter-array near the runway due to the MUCH higher Thrust/MW you get from Thermal Turbojets than Thermal Rockets, and the complete lack of any need for internal reaction-mass when using them. You ascend in slow, lazy circles to stay in range of the transmitter, and then only head East when you're near maximum cruising altitude/speed using Thermal Turbojets... You then switch over to Thermal Rockets as you come in range of the second transmitter array, which should be located a good deal East of the runway... This ascent-profile is actually the Escape Dynamics plan- although they just rely on a single transmitter-array instead of two! Regards, Northstar - - - Updated - - - Simple answer: The cost/kg of Microwave Thermal Rocketry has come down *DRAMATICALLY* over the 50+ years since the discovery of Microwave-Beamed Power as a means of wireless power-transmission (in the 1960's with the invention/refinement of the rectenna). It would now cost only around $6000/kg to LEO using a purely ROCKET driven approach with expendable launch-vehicles, but with 1970's technology it could have EASILY cost $60,000/kg or more (for comparison, chemical rockets are about $10,000-$8,000/kg to LEO). Microwave Thermal Spaceplanes are MUCH cheaper per kg of payload-capacity than Microwave Thermal Rockets, however, due to being reusable AND being able to carry *MUCH, MUCH* more payload to orbit per MW of beamed-power... The same relationship actually exists between MW of Thermal Energy and payload-capacity with chemical spaceplanes vs. rockets, at least in theory- but it's not really limits on the available MW of Thermal Energy that drives up the costs of chemical rockets... Long Answer: The technology behind Microwave Transmitters, in the form of gyrotrons, has only reached the appropriate stage of maturity (and cost-effectiveness) in the past 10 years or so to make it worthwhile (THIS is the main reason a Microwave Thermal Rocket would be $6,000/kg now, and perhaps $4,000/kg in 2030, but $60,000/kg in 1970). If the space program had started in 2010, it very well *MIGHT* have used Microwave Thermal Rocketry from the start. But the gyrotron technology simply wasn't mature enough back in 1960 to make it worthwhile to use Microwave Beamed-Power for things like the Apollo Program... Perhaps not surprisingly, maturing gyrotron technology further is one of the TOP priorities for Escape Dynamics, as Microwave Transmitters represent something like 95% of the cost of a Microwave Thermal Rocket (this is also why a Microwave Thermal Spaceplane is worthwhile- even if it costs 10x as much as a Microwave Thermal Rocket per mission for the vehicle itself, it it gets to orbit on half the beamed-power it will actually by CHEAPER than a Microwave Thermal Rocket...) This has reached the point where Escape Dynamics (which wants to build a SSTO Microwave Thermal Spaceplane!) has hardly even bothered messing around with Microwave Thermal Thrusters yet (which are, by comparison to Microwave Transmitters, relatively cheap and easy), and has instead focused on developing better gyrotrons and Microwave Transmitters- because this will save them more money in the long run... Their most recent breakthrough, a 200 kW Microwave Transmitter with Side Lobe Suppression and a lower cost/kW than existing transmitters, is actually one of their most important- because it means that they will be able to execute their entire launch-architecture *MUCH* more inexpensively than if they had focused on developing better Microwave Thermal Thrusters right off the bat... There *ARE* labs focusing on Microwave Thermal Thrusters, at *several* universities across the country, though (for instance, check out the webpage of this PhD project at Stanford). So it's not a topic that is being ignored by ANY means... Regards, Northstar

Glad to see you're thinking about this carefully N_las, but a photon drive is NOT the ultimate in efficiency for creating your own reaction mass (out of energy). Thrust = Mass Flow Rate * Exhaust Velocity *AND* E = 1/2 * m * v^2 Take a moment to think about these two equations. You'll *QUICKLY* realize that the higher your Exhaust Velocity, the lower your Thrust for the same Energy requirement. Since a photon has the HIGHEST POSSIBLE EXHAUST VELOCITY, it also has the LOWEST possible Thrust/MW. A Cannae/EmDrive is not postulated to actually CREATE the virtual particles (they normally exist as part of the ebb and flow of the universe), but to give energy (momentum) to them. Even if they promptly disappeared again, if they existed long enough to exert a reaction force back on the drive, then it's essentially the same as having infinite reaction mass, and imparting energy to it to generate Thrust. An interesting caveat follows- if the amount of power you pump into the Cannae/EmDrive did not lead to more virtual particles appearing (in actuality, it's theorized to do precisely* that), then you would get exponentially declining Thrust/MW due to the equations above. Luckily, pumping more energy into a space *IS* theorized to increase the generation of virtual particles- though once again unless using twice as much power led to twice as many virtual particles, I would expect Thrust/MW to decline (reaching an ultimate limit at the efficiency of a photon-drive) the higher the power-level you put into the system... The efficiency of a Cannae/EmDrive should indeed reach a limit of that of a photon-drive, as some people have stated: but they are incorrect about the relationship- a Cannae/EmDrive should reach a MINIMUM efficiency equivalent to that of a photon-drive when it is accelerating the virtual particles to the speed of light. Any slower Exhaust Velocity than the speed of light, and you will get a higher Thrust/MW... Indeed. E = m * c^2. Ultimately, with unlimited energy you have unlimited Thrust no matter how you look at it. Of course, you DON'T have unlimited energy... You see, though, you can generate changes in momentum with mirrors in space. There are these things called Solar Sails- have you ever heard of them? Essentially, they work off changing the direction/energy of the Sun's light int order to change the direction/energy of the spacecraft. The momentum-change they impart is VERY slow, though... A solar panel/ photon-drive combo may work better than a Solar Sail, though, because ultimately it's easier to control the direction you change your momentum in... You can point a photon-drive any direction you'd like, but a Solar Sail can only accelerate you in a combination of six directions: prograde, retrograde, normal, anti-normal, or radially outwards from the Sun (but NOT radially inwards)- all assuming a circular orbit around the Sun... A photon-drive, on the other hand, could angle the solar panels such as to produce a prograde thrust from the radiation pressure of the Sun (by pointing the solar panels at a 45-degree angle to the Sun), then use energy collected and stored from the panels to exert a Thrust in the radially-inward direction. So, you have a bit more control over your trajectory-changes with a solar panel/ photon-drive combination than just using Solar Sails... You could always use a nuclear reactor with a photon-drive (or better yet- a Cannae/EmDrive!), though, to operate without reflecting large amounts of light. Regards, Northstar

That's the plan Excape Dynamics is going with, actually- turning the entire belly of the spaceplane into a Microwave Thermal Receiver... *Cough* it takes 10 km/s for a ROCKET to get to orbit (that includes atmospheric drag and gravity-losses). Orbital velocity is NOT 17.2 km/s. Orbital velocity is about 7.8 km/s. As I've pointed out repeatedly, Microwave Thermal Thrusters get more than twice the Specific Impulse (ISP) of Hydro/LOX. And, they're much lighter than chemical engines (for 2-3x the TWR, due mostly to lower mass rather than higher Thrust). So it's more like you can't afford *NOT* to carry a Microwave Thermal Thruster- in that it will MASSIVELY reduce your mass-requirements (pun intended). The heat you pour into the Microwave Thermal Receiver doesn't remain in the ship. It is used to heat Liquid Hydrogen (which is colder than cold), which then exits the ship. It actually acts to COOL the ship, because the exhaust gasses STILL don't get heated as hot as the frictional heating could potentially get- and will pick up more heat on the way out. Which brings up an interesting point- you could actually use the frictional heating of the spaceplane's skin (especially the belly) to help heat the propellant (at high enough Thrust levels, you would still need more heat-energy than the skin of the spaceplane could provide...), using the Liquid Hydrogen as a coolant. This would help solve two problems (frictional heating, and the need to heat the propellant) with one system! The Microwave Thermal Thrusters have already been proven to work (on the ground). Gyrotrons, the main component of a Microwave Transmitter, are already routinely used in metallurgy. The necessary targeting technologies are already well-developed from warfare. What's NOT to work about it? Regards, Northstar

I relate to most people. They just judge me to be inadequate to their unrealistic standards (where every man must be muscular, smooth, and cool). There's a difference. Regards, Northstar