Northstar1989

Yeah, I'm not sure what you mean by "MegaWatt players" and "KiloWatt players" in this context, or what that has to do with NearFuture propulsion. The only context this makes sense in is with the Alcubierre Drive variants you were discussing before.. And even while it is possible to (very slowly) generate ExoticMatter with a MW-scale reactor using the original version of the warp drive, and run the Alcubierre Drive off that (which is realistic- even if containment fields are needed, which they may not be if ABZB and my original thoughts were correct), the rate of ExoticMatter generation with such a weak reactor is prohibitively slow. For a manned mission, players need to utilize a GW-scale reactor to generate the ExoticMatter either way. Gigawatts of electrical power should never be required to actually run an Alcubierre Drive though- the magnetic containment fields for ExoticMatter would not require any more power than those for Antimatter, even if they were necessary... (the high energy-cost of running an Alcubierre Drive you've heard about before is the power-requirement to generate the Exotic Matter in the first place- the actual process of generating a warp bubble once you have plenty of Exotic Matter shouldn't be so energy-intensive that you need GW of power...) Regards, Northstar

OtherBarry, I'm referring specifically to the RealFuels Procedural Tanks. The normal (no RealFuels) Procedural Parts were re-balanced a while back to be less restrictive, but the RealFuels versions haven't been updated for some time... Also, 0.90 did come with a stock tech tree rearrangement. But that shouldn't affect the tech-limits file, as the node names haven't changed, and the file refers to specific tech nodes. Here's one of the tech limits for isntance: TECHLIMIT { // X200-16 - 2.5 x 1.875 m = 9.204 kL name = heavyRocketry diameterMax = 3.0 volumeMax = 10.0 } As you'll notice, this code limits diameter to 3 meters after you unlock heavyRocketry (the limit is even more restrictive beforehand). This limit is never relaxed until the player unlocks MetaMaterials- even veryHeavyRocketry doesn't allow players to build fuel tanks wider than 3 meters (even though at this point players would have max-size 3.75 meter tanks with stock and 5 meter tanks with mods!) Regards, Northstar

@FreeThinker The following code comes from the config file of the 3.75 meter Thermal Rocket Nozzle (the pre-sized part, not the one relying on TweakScale) // --- node definitions --- node_stack_top = 0.0, 0.055308 , 0.0, 0.0, -1.0, 0.0, 2 node_stack_bottom = 0.0, -1.196 , 0.0, 0.0, -1.0, 0.0, 2 Did you notice something odd about it? The config file uses node "size 2" instead of "size 3". This significantly weakens the part's connection to other parts. The code should look like this instead: // --- node definitions --- node_stack_top = 0.0, 0.055308 , 0.0, 0.0, -1.0, 0.0, 3 node_stack_bottom = 0.0, -1.196 , 0.0, 0.0, -1.0, 0.0, 3 This isn't the only place where a bigger node-size should be used though. Files like this are sprinkled through the KSP-Interstellar Extended (and the base 0.90 port maintenance thread) parts folder... EDIT: The 3.75 meter Microwave Beamed Power Receiver (which needs a TweakScale version, by the way), Large Inline ISRU Refinery, 3.75 meter Fission, Fusion, and Antimatter Reactors, and 3.75 meter Electric Generators are also all using "size 2" nodes instead of "size 3" nodes, which would be the appropriate node-size. The Thermal Turbojets and Atmospheric Intakes are also missing a node-size definition altogether (which causes them to default to node "size 1", which is inappropriate for the 2.5 meter versions). Regards, Northstar

OK, so does TweakScale 1.52 adjust node-sizes in accordance to re-scaling? I.e. if I increase the size of a 2.5 meter diameter part to 3.75 meters diameter, the node size should increase from size 2 to size 3. Or if I decrease it to 1.25 or 0.625 meters, it should decrease to size 1 or 0, respectively... Node sizes have serious consequences for rocket construction in KSP because they affect the strength of attachment between two parts, and how wobbly/strong a connection between those parts is... Regards, Northstar

OK, so quick question then- does the USI WarpDrive folder come as a standard part of the KSP-I Extended download, or is it an optional addition? Speaking of dependencies, the KerbalStuff installation instructions could use some clarification that installing TweakScale is still only optional (as the non-tweakable reactors still exist as legacy parts). Also, why do the old/legacy reactors use the original performance parameters from Fractal_UK's last release of KSP-Interstellar? (i.e. just 85 MW for a 1.25 meter Particle Bed Reactor) Shouldn't they at least use the last/most updated MW production etc. that I came up with for the different size-classes here? Regards, Northstar

OK, so according to this website's thermodynamic calculator, which I actually also used to help figure out the density for the Liquid Nitrogen resource before (which should be 824.907 kg/m3, not 810.6 kg/m3 as is used in the working document posted by Nertea earlier), the density of Liquid CO2 at 5.6 barr and -54.8 C should be 1173.25 kg/m3. 1173.25 kg/m3 isn't all that far from the figure of 1200 kg/m3 I had been using as a placeholder in KSPI- and means that 1256 kg/m3 is actually too dense (it's the density at 20 barr of pressure, which would be much less mass-efficient in space due to the nearly 4 times higher tank-mass...) http://www.peacesoftware.de/einigewerte/co2_e.html Also, to go back to LqdNitrogen for a moment, it's not a resource currently used in RealFuels, only in KSP-Interstellar Extended. RealFuels uses compressed Nitrogen gas instead. So there should be no input required other than that of FreeThinker to adjust it back to a density of 824.907 kg/m3 from its current density of 810.6 kg/m3 in the working document. The higher density is more accurate to real life (it's at a slightly lower temperature than the density currently used in the CRP working document- but still quite a bit warmer than LH2 and thus perfectly reasonable for rocketry applications...) as rocket designers will typically choose the temperature for their fuels that gives the best mass-fraction, and thus we get the density currently used in KSP-Interstellar Extended... Regards, Northstar - - - Updated - - - According to the same thermodynamics calculator as before, the density of N2 at 1 barr and -200 C is: -824.9 kg/m3 Which is the same as the slightly more precise figure of -824.907 kg/m3 we've been getting from other sources (at slightly lower temperatures still) and using for KSP-Interstellar Extended. Once again, Liquid Nitrogen's density is 824.907 kg/m3 in KSP-Interstellar Extended, and it is not a resource used in any other mods. Out of respect for backwards-compatibility of existing designs (and the mod devs, of which I am one- even if FreeThinker is the primary author) I think we should stick with 824.907 kg/m3 as the density for Lqd Nitrogen... This way, any spacecraft players designed around the previous density of "LiquidNitrogen" will still work with "LqdNitrogen" as the density will remain the same... Regards, Northstar - - - Updated - - - Finally, other issues: - Water is used for KSP-Interstellar, not just TAC Life Support. This needs to be updated on the working document - LqdCO2 is a KSP-Interstellar resource as well as a BioMass resource (by the way, I found where the density-figure BioMass was previously using came from- it was the density of CO2 at room-temperature and over 300 barr of pressure. No wonder their density was so low!) - High-Test Peroxide (HTP) is a KSP-Interstellar resource as well as a RealFuels resource. In RealFuels it is used for RCS. In KSP-Interstellar, it is used as an intermediate in manufacturing Monopropellant (soon to be replaced by Hydrazine- which is what KSPI assumes Monoprop actually represents, and is the basis of the ISRU chemistry to manufacture it...) Regards, Northstar

Oh wait, just came across this on Wikipedia: "Carbon dioxide has no liquid state at pressures below 5.1 standard atmospheres (520 kPa)." I'm, uhhh, not 100% sure this is accurate (it is Wikipedia after all), as there is a 21-degree difference between the listed melting-point (-78 C) and boiling-point (-58 C) of CO2 at 1 atm of pressure according to some other sources (that is, there seems to be some disagreement about where the triple-point lies), but if it *is* true it means that we either need to store CO2 as a solid (which is trivial- just cool it to -78 C and you get dry ice at a density of just over 1562 kg/m3) or as a gas (which is probably a bad idea due to the very low density- less than 3 kg/m3 at its boiling point). If you stored it as a solid, you'd have to heat it up in a slow+controlled manner before using it in a Thermal or Electric rocket... Alternatively, if Wikipedia is correct, you could still pressurize to 5.1 atm and store it as a cryogenic liquid. This would still give better mass-fractions than storing the gas at 1 atmosphere of pressure, as 1 L of tank volume would require 5.1 times more tank-mass but store more than 400 times as much propellant mass... (density less than 3 kg/m3 vs. more than 1200 kg/m3) Regards, Northstar - - - Updated - - - That's only if the triple-point is really at 5.11 atm. There seem to be a handful of conflicting sources on this- although the overwhelming majority do concur with that number... EDIT: Looks like the other figures on the triple-point all date back much further, and were probably inaccurate. So, it looks like Wikipedia was correct. The question then is whether it's wiser to store the CO2 as a solid or as a pressurized liquid... The former has much better mass-fractions, but could cause the tank to rupture if temperature is not kept below the sublimation-point... (-78 C at 1 atm, which is still over 100 degrees Celsius warmer than your average LOX tank...) The latter is much easier to store, but requires enough tank-mass to maintain at least 5.1 atm of pressure with a reasonable safety-margin... Regards, Northstar - - - Updated - - - @NathanKell OK, a quick question whenever you come across this post... How much pressure are the standard (non-Service Module) fuel tanks supposed to be able to hold in RealFuels? As I understand it, they are capable of holding "moderately pressurized" cryogenic liquids, just not highly-pressurized gasses such as pressurized Nitrogen for RCS... Is 5.1 atmospheres of pressure within the range that a standard tank should be able to hold, or should KSP-Interstellar Extension Config only add Liquid CO2 (or rather LqdCO2 or whatever name we settle on here...) to Service Module tanks to reflect the need to keep it pressurized at 5.1 atmospheres of pressure? (maybe 5.4 atm for a bit of a safety-margin) Also, could I convince you to add liquid/cryogenic CO2 as a standard resource to RealFuels when this is all over and we've settled on an official CRP density for the resource? It could be used with the LV-N rockets in the engine configs (such as Stockalike) as an alternate (high-thrust, low-ISP) propellant with higher fuel-density than Methane or Ammonia and very few issues with boil-off... (as it is a liquid at -56 C at the triple-point) Regards, Northstar

Sounds like a good idea to me. On an entirely different note, has anyone managed to dig up any data for the density of liquid CO2 at 1 atm of pressure and -70 Celsius? We know it's higher than 1256.74 kg/m3 (since that's the density at -20 Celsius and 20 atm pressure), but the question is how much higher... Regards, Northstar

Welcome aboard TheXRuler! If you feel you're up to the challenge, KSP-Interstellar Extension Config is looking implementing some new ISRU reactions, and one idea is to use the Regolith converter-code to do this. If you're interested, swing by the development thread for KSP-I Extended (link's in my signature) and familiarize yourself a little with what the mod is about and the ISRU reactions I'm interested in adding (I mention some of them in the thread- and would be more than happy to give you a re-cap there). Then get a hold of RoverDude and see if you can't get his help in learning how to use Regolith to create converter-reactions for the new ISRU reactions (which are conversion rather than extraction reactions- we're currently using ORS for all our extraction reactions for, reasons...) If he's able to help you figure out a way to use the Regolith converter-code with the existing KSP-I ISRU refinery parts, we'd be more than happy to take a look at adding in what you come up with (note that the current densities for some of the resources that will be used in the ISRU reactions are slightly inaccurate- Liquid CO2 is getting a new name and a higher density in the next CRP revision, for instance... So you have a bit of time to figure out the Regolith converter code before we settle on more accurate resource-densities...) Regards, Northstar

On the physics? I was going off your demonstration video of the drive- which appeared to show conservation of angular rather than linear momentum. The problem with that (besides that some models of how the drive works- which I find more believable- support that the drive would conserve linear rather than momentum) is that it isn't implemented correctly in your mod. If you were still subject to gravity, it would continue to curve your path, even while in warp. Thus, a warp-drive would become something more analogous to time-warp in KSP, where your path continues along the same orbit, just at a faster pace... (which isn't really that useful in KSP unless you're using a life-support mod) If there's a switch to use conservation of linear momentum instead that can be used in the VAB, then I guess it's actually no less accurate that KSP-I's original version, which works on conservation of linear momentum... Except the whole bit about changing the physical laws of the universe with the flick of a switch. I don't have anything against you RoverDude. I was under the impression that you had something against me. The post you linked to describes the fundamental physics issue fairly well. I'm of the school of thought that an Alcubierre Drive would conserve linear rather than angular momentum, and find the physics behind it more convincing... Haelaeon at least made a convincing case for why the Alcubierre Drive might conserve angular momentum instead, even if his arguments haven't won me over... However if you want to base the Alcubierre Drive off the hypothesis that you don't separate from normal space-time when you activate the drive, and thus angular momentum (rather than linear momentum) is conserved, then gravity needs to continue to curve your path as normal- in which case the Alcubierre Drive doesn't allow you to leave a planetary system without first reaching escape-velocity, and acts as little more than deadweight on a spacecraft without life-support requirements... Regards, Northstar

Fun, yes. But not realistic. The way RoverDude's version operates is less realistic from a physics perspective... You know, I've never actually played with either version- I've only seen videos of each. So, while I can say that Fractal_UK's version is more realistic from a physics perspective, I can't say which is really more fun/exciting/interesting to use... Yes, the power requirement would be extreme- but to generate the Exotic Matter, not to contain it. The magnetic fields to contain it (if magnetic containment is indeed necessary) shouldn't be any more power-hungry than those to contain antimatter... Where did you get these quotes? If they're accurate, then it sounds like an interesting interaction you would want to avert... Also, the creation of "positive" energy would imply that you actually get some energy back when generating the Exotic Matter- in fact that with a 100% efficient system to generate the Exotic Matter that you could actually produce useful energy while creating it. Of course, the only ways we can dream up to create it right now involve extremely powerful particle-colliders, and as such are going to cost a lot more energy to inefficiency than you get back from the "quantum interest"... Regards, Northstar - - - Updated - - - These were *exactly* my thoughts about Exotic Matter. But FreeThinker is quoting a source that disagrees with our assumptions. So, if that source checks out, then it appears we were both wrong... Regards, Northstar - - - Updated - - - How does KSP-I ignore those inconsistencies? We're in agreement about 95% of this- which is of course why I decided to work with you to help create KSP-I Extended. The one place I'm in disagreement is that I have a slightly different vision of the aim of the mod... I think the aim of KSP-I is and should be to try and realistically or semi-realistically implement technologies that really are possible, even if they haven't been done yet ("hard" science fiction, if you will), which will enable new interplanetary (and eventually interstellar) travel possibilities. In doing so, they provide players with enhanced capabilities, culminating with the Alcubierre Warp Drive. But nowhere along the line should KSP-I intentionally try to make things any harder than real life. If real life is or could be imbalanced (if reactionless thrusters like the EmDrive pan out for instance- which is already reflected as a "what if" with he KSP-I "quantum vacuum thruster" parts that you can eventually unlock...) then so should KSP-Interstellar be. In the mod as it is (or could be) in real life, no matter how unbelievable or "OP'd" reality might be... Regards, Northstar P.S. You might be interested to learn that humanity is already in possession of one propulsion system with inter-stellar capabilities. The Orion Nuclear Pulse propulsion system has a high enough ISP that it can be adapted for inter-stellar travel, and in fact several designs for doing this already exist...

Thanks for the quick reply. I think you're under some misconceptions of the inherent stability of Exotic Matter. Exotic Matter is not the "opposite of black hole matter" as you say. It's matter with negative mass, but the magnitude of that negative mass isn't necessarily any greater than that of a comparable amount of normal matter... We're dealing with a few kg of negative mass here, not the kinds of magnitudes of gravitational forces of a black hole. Does a few kg of normal mass exert a large (or even noticeable) gravitational influence? It does not. Neither does a few kg of negative mass. Exotic Matter might push objects away from it, rather than pull them closer- but just a few kg or tons of it is going to do so at a magnitude of force that is basically insignificant. So, you could still contain it inside an ordinary tank- in fact it would naturally separate itself from the walls of the container in zero gravity without requiring any outside powerful (and energy-hungry) magnetic field to contain it. And even if Exotic Matter *did* come in contact with normal matter directly, it's not going to interact with it explosively like antimatter. In fact, Exotic Matter, while quite strange and unusual, in small quantities (the kind we're talking about here for an Alcubierre Drive- it's not like we're building a star or planet out of it) is perfectly harmless... By the way, regarding black holes: Even if you could collapse just a few metric tons of normal matter to infinite density (creating a sort of miniature black hole) the magnitude of gravitational attraction exerted by that mass on other objects would remain unchanged at the same distance from the center of mass (i.e. its gravity would be insignificant). What makes a black hole truly dangerous isn't the magnitude of its gravitational force (which is the same as the mass that collapsed when creating it), it is how close you can get to that center of mass. You can head directly into the center of a black hole- something you can't do with a comparably massive star or nebula without starting to pass through its boundaries well before you reach the light-capturing gravitational forces present near the center of a black hole... I.e. it's the density of a black hole that is dangerous, not the total magnitude of mass (although the infinite density does lead to it eventually acquiring a very large mass, leading to the supermassive black holes that are truly scary...) Regards, Northstar - - - Updated - - - I think I can sum it up this way: (1) Exotic Matter doesn't require large amounts of energy to maintain- this isn't realistic (to theory). In fact, an unpowered storage container should be able to store it just as effectively as one with magnetic containment (and there's no reason to keep it separate from normal matter...) (2) Different physicists have different opinions about an Alcubierre Drive. Many think it's impossible. Of those who think it is possible, some think the warp bubble wouldn't require additional Exotic Matter to maintain, some think it would. Given that no Alcubierre Drive has ever been built, either implementation in KSP is equally valid... (3) If there is no requirement for additional Exotic Matter during flight, there is no reason to think you couldn't generate more while in warp-flight... (4) Even if you lose all power, Exotic Matter can, in fact, be stored forever- or at least equally long with or without power (subject to inherent nuclear instability that we don't yet know about- in which case storing it inside a magnetic field isn't going to do anything to stop it from decaying either...) Since these were basically your reasons for abandoning the warp drive part KSP-Interstellar has been using since the beginning, I hope you realize there's no reason to switch to RoverDude's version (which is actually less realistic), and will switch the part back to the original promptly. Changing too many aspects of the base mod is going to make the Extension Config unpalatable to many player- especially if one of the changes runs contrary to both fun and realism, by making doing something (like warp-travel) even harder than it realistically should be (if an Alcubierre Drive can even be built in the first place). Regards, Northstar

Wait, what have you done here? You replaced the KSP-Interstellar Alcubierre Drive with a part from a different mod (that presumably works differently...) That's kind of a big deal. What's the reasoning behind that? The Alcubierre Drive is kind of the part the entire KSP-Interstellar mod was originally built around, and replacing it with a different version from a different mod (that doesn't work the same way as the original???) isn't exactly something that should be done lightly... EDIT: Also, the XenonGas isn't used as a coolant in RoverDude's version of the Alcubierre Drive. It's used for "maneuvering thrusters"- which kind of doesn't make sense as an Alcubierre Drive wouldn't require built-in maneuvering thrusters to operate... I've been examining the video he posted of his warp drive in action- and it also seems to only generating a warp bubble of a very limited diameter around the part itself- which may actually be more realistic (energy requirements increase with larger warp bubbles) but greatly limits the size of ships you can move with a warp drive part... EDIT #2: There may also be issues with the degree of realism in how the Alcubierre Drive implemented by RoverDude is affected by physical laws, in that the version found in prior versions of KSP-Interstellar is more realistic. For instance, you would expect the Alcubierre Drive to translate your ship relative to the Solar System without need for maneuvering thrusters. I don't know how to describe the differences better than this: with a KSP-I Alcubiere Drive (prior to this version of KSP-I Extended) activating the drive while pointing prograde in close circular orbit of the Sun would quickly fling you out to the edge of the solar system (moving you in a straight line). In RoverDude's version, nothing would happen if you didn't have the maneuvering thrusters accelerating you in the direction your ship is pointing- the ship would remain in a circular orbit despite the contraction of space-time ahead of it which should (in theory) translate you in a straight line without any source of acceleration being necessary... OK, so the observed result of the two is exactly the same, so long as you have functional maneuvering thrusters (and a source of XenonGas with RoverDude's version, or Helium with the way you adapted it). But the difference is there is no requirement for the maneuvering thrusters in real life, or in the version previously found in KSP-Interstellar... Nor is there need for the Liquid Helium- unless you're using it to dissipate WasteHeat, which radiators should be perfectly capable of doing without requiring an expensive resource that quickly boils off... (thus limiting the longevity/endurance of warp-ships unrealistically) Regards, Northstar

Northstar Kerman tossed and turned before the night of his second big speech. And he dreamed... At first, he dreamt of the the Munar-1 mission going smoothly. But then came the landing... "We're coming down too fast!" shouted one Kerbal, "Activate the abort sequence" shouted another. "It's too late- we're going to die!" shouted a third still... Northstar Kerman, understandably, slept uneasily: Then Northstar woke up, pinched his pale green cheeks a little to bring back some color to them, and remembered that the Command/Service Module still hadn't even yet made it to Low Kerbin Orbit... As Northstar and the rest of Kerbal-kind watched the launch of the Command/Service Module that day they were giddy with excitement... Sure, the CSM made it off the launchpad a little late due to some last-minute adjustments (engineers muttered something about wanting to optimize the shape of the nose...) and had to follow a mission-trajectory that wasted excessive amounts of fuel orbiting within the upper atmosphere for a period of time in order to keep up with the mission-timetable as a result, but the end was still undeniably exciting- the 4 Kerbal crew of the Munar-1 mission was now in space between the LEM and Command/Service Module, and all critical mission-equipment for the Munar landing was in place as well! A few hours after the launch, the Command/Service Module and LEM had rendezvoused+docked in Low Kerbin Orbit, and soon began the first half of their trans-Munar injection burn... In order to save fuel, and reduce the needed engine-mass in orbit, the mission plan called for a "periapsis kick" maneuver during the trans-Munar injection: the docked pair of vehicles would first perform a burn to enter an elliptical orbit, and then follow that orbit back around to the next periapsis such as to perform more of the ejection-burn close to Kerbin and take greater advantage of the Oberth Effect... (named after one strangely-named Kerbal: Hermann Oberth) Then came the launch of one more previously-unannounced vehicle that Northstar suspected was the real cause of the earlier delay: the launch of the Munar-1 fuel tanker, a vehicle designed to rendezvous with and refuel the Command/Service Module (which would burn more of its fuel getting the Lander to the Mun than in previous mission plans, so the Lander had to burn less) in Munar orbit to provide it with the fuel to get the Kerbals home... Like with all the other Munar-1 launches, the sustainer stage was recovered and refurbished, for use in future high-payload launches such as additional Mun landings, and mission Northstar could only dream of... But dream he would- and Northstar did not forget about his speech on the future of manned Kerbal space exploration later that day... Ladies, Gentlemen. I have heard some Kerbals criticize and complain about my earlier comments about our great, great grandchildren living on Duna some day. Allow me to explain. The study of life sciences and evolution teaches one this above all. Life grows, life adapts. When it stops growing and giving birth to children, it decays and dies. But in order to meet the challenges in the meantime, life must adapt. I do not fall prey to the fallacy that we will someday kerra-form Duna to be like Kerbin, as some critics have supposed. Rather, I believe that future generations will learn to adapt to the harsh climate of Duna. They will learn to dig their shelters underground to seek protection from the harsh, high-radiation environment and insulation from the cold. They will learn to rely on local energy-sources such as solar and nuclear power, grow crops in greenhouses to extract precious food and oxygen from the atmosphere, mine sub-surface water, and perhaps utilize the energy-sources that give rise to trace amounts of methane found in the Dunan atmosphere- should they be geological. They will learn to live in pressurized underground habitats and make them pleasant places to live instead of seeking to turn the surface into a Kerbin-like paradise... And, most of all, they will learn to make use of local sources of rocket propellant- because without it communications satellites, solar power-collectors, and occasional passenger-trips to the Kerbin-system will simply not be possible in a sustainable manner. They will learn to do these things and more- not to save money- as motivates us today, but to survive, and someday expand their colonies to provide living-space for their children... (OOC: The failed landing wasn't a dream, of course- I started the final landing-burn far too late and immediately after a quicksave- and as a result I had to revert all the way to a backup save right before the launch of the CSM in order to avert the disaster...) Regards, Northstar

By the way, FreeThinker, let me know when you're ready to start tackling more of the ISRU reactions and fixes (making the Sabatier Reaction produce Methane and Water instead of Methane and Oxygen, and allowing it to operate outside the atmosphere- for instance) I'm REALLY excited to get to some of the In Situ Resource Utilization stuff. Maybe it's just because my dad trained as a Chemical Engineer, and I currently have a buddy who works in chemical reactors, but personally I consider the ISRU reactions in KSP-Interstellar to be some of the MOST IMPORTANT things for it to develop as it goes forward! And, just because it's inspirational, like all the things we can do with ISRU are, here's the good ole' "Build, Fly, Dream" trailer, which I deeply love... Regards, Northstar

OK, so a couple bugs I've been sitting on for a while, and wanted to get out there... First of all, the Plasma Thruster still is showing "0 seconds" ISP for all its fuel-mods in the VAB/SPH. This is an issue for mission-planning and rocket-design, even if it doesn't affect the actual performance... Second, and more serious, the tweakable-size Thermal Rocket Nozzle that replaced the pre-sized ones is stuck with a minimum diameter of 2.5 meters... This, of course, makes it impossible to build efficient 1.25 meter Thermal Rockets... These screenshots were from KSP-I Extended 0.7.14, but there isn't any mention of fixing these bugs in the 0.7.15 changelog (I'll be DL'ing 0.7.15 shortly for the TTJ changes though- and to see if the ISRU refinery fixes for RealFuels I posted made it into 0.7.15) Regards, Northstar

I'm going to have to actually disagree on this one- it wouldn't be too hard to use 1 unit = 1 liter (with Antihydrogen there are what, about 95 grams/liter?) and we need to compromise on this in order to get some other fixes made... Speaking of which, on FreeThinker's request I took a look at the working document. I don't have time to go through all the documents right now, but here are some things I spotted in the first document. IS this the right document to look at, btw? https://docs.google.com/a/cornell.edu/spreadsheets/d/1F2NYLj47O6VdThCXqBcI_hB-bDIMh4ZWB2FFyrjMLkg/edit#gid=650840806 ArgonGas is also a KSP-Interstellar resource (currently called "Argon" in KSP-I). It is used for Plasma/ATTILA Thrusters, alongside XenonGas, Lithium, and several other resources... LiquidCO2/LqdCO2 is a KSP-I resource as well, as we've been discussing Water is a KSP-I resource (used in Thermal Rockets) LiquidHydrogen is a KSP-I resource (although KSP-I currently uses LiquidFuel as a Hydrogen placeholder) I'll have to look for other documents later- something tells me this was not the document I should have been looking at... Regards, Northstar

Based on the implementation of the RAPIER engine in RealFuels (Kerosene-airbreathing and Kero/LOX rocket) I'm not sure it is actually meant to be a SABRE analog... And since many players using AJE are probably also using RealFuels... Now, B9 Aerospace has an engine which is actually called SABRE, and even looks like the real SABRE. It even uses Hydrogen and HydroLOX in RealFuels. What about balancing this to be the SABRE engine, and leaving the RAPIER as a lower-ISP Kerosene-burning alternative? (which couldn't possibly make orbit on a HTHL SSTO in RSS, of course- due to the much lower ISP of Kero/LOX than HydroLOX, and is mostly limited to stock-sized systems for spaceplane use) Also, regardless of what RAPIER is meant to represent, it really should have higher thrust in rocket-mode than in air-breathing mode. Anything else just seems silly to me from a realism-perspective: though of course it's not my mod (in fact, I don't even use AJE in my saves), and you're free to do whatever you want with it. Your users will love you either way. Regards, Northstar

I concur with FreeThinker. You're not going to have an easy time building a HTHL (Horizontal Takeoff, Horizontal Landing- i.e. a spaceplane) SSTO in RSS 64K with conventional technology. In fact, without at least using RealFuels, FAR, and SABRE (not RAPIER- which runs on Kerosene instead of Hydrogen) engines you don't stand a chance. With them, you could build something like Skylon- but you should still only expect a 2-3% mass-fraction... (so a spaceplane massing at least 500 tons or so on the Runway just to get a 2-ton Mk2 cockpit into orbit...) Without Realism Overhaul scaling-up, you can pretty much forget about something that big actually getting off the runway though... Even with KSP-Interstellar, if you stick to near-future tech (Molten Salt and Particle Bed Reactors, and Microwave Beamed Power) you're going to have an extremely hard time. Your best bet is probably to build something that relies on Microwave Thermal Turbojets to get to about 27 km and Mach 3-4 (similar to Skylon but a bit higher relative to atmospheric height) and then switches over to Microwave Thermal Rockets to make it the rest of the way to orbit... Even so, while you may double your maximum ISP and eliminate the need for fuel until you switch to rocekts- and thus more than double your mass-fraction, expect a spaceplane of at least 200 tons with LH2 alone (which with the low fuel-density of Hydrogen means an enormous spaceplane- even larger in volume than the 500-ton behemoth discussed earlier) and easily 400 tons (but with higher fuel-density) for a combination of LH2, HydroLOX, MethLOX, and pure Methane... (manageable with RealFuels as it's really only 3 resources you need to manage here- Hydrogen, Oxygen, and Methane...) Regards, Northstar

Well, as I understand it, RealFuels needs to keep a version of Nitrogen as a pressurized gas for RCS (specifically, for Module RCSFX), where it can be used as one type of cold-gas RCS thruster... For this reason, there needs to be a separate NitrogenGas and Liquid Nitrogen resource (each with different density and cost), or something along these lines... We already made KSP-Interstellar Extended to utilize both variants in the Thermal and Electric thrusters- remember working with me on that? Regards, Northstar

Oops, didn't see this earlier. Yeah, that's actually not a good number to use then- the density should be higher. That website was actually one of the sources I came across in my initial search and discarded for the reasons stated below... That's the density at -20 Celsius (the boiling-point is -57 Celsius at 1 atm of pressure) kept in liquid phase by pressurizing it to nearly 20 (19.7 to be precise) atmospheres of pressure. Here's the exact wording from the website: Liquid density (at -20 °C (or -4 °F) and 19.7 bar) : 1256.74 kg/m3 So yeah, it kind of needs to have a higher density than that- considering that density increases quite substantially with lower temperatures, and pressurizing cryogenic liquids to keep them in liquid phase isn't a particularly mass-efficient option (pressure vessel mass increases proportionally to the pressure difference from the environment- a 20 barr pressure vessel in space weighs 20 times what a 1 barr pressure vessel weighs...) Pressurizing a cryogenic liquid doesn't increase its density by a particularly notable amount either- you can ask NathanKell: I actually embarrassed myself by arguing this point over on the RealFuels thread a while back (at the time I thought you could substantially increase cryogenics density by pressurization, mainly due to what turned out to be a decimal-error in my calculations that led to a result 2-3 orders of magnitude off...)- it turns out that LH2 only increases in density by about 1-2% at 120 barr of pressure... (and Hydrogen is one of the most compressible of all cryogenic liquids) Once again, the 1200 figure was a low-ball estimate I went with to make absolutely sure the number we used for KSP-Interstellar Extended wasn't OP'd (since I was the one who did the research of this). But the actual density should be for 1 barr at -70 to -60 degrees Celsius (CO2 freezes at -78), which means it will be substantially denser than 1256.74 kg/m3, which is for 20 barr and -20 Celsius. Regards, Northstar

Wait, you replaced hydrogen peroxide with CO2??? Clearly there's something I'm missing here... Well, Antimatter should be expensive. Incredibly, crazy, mind-staggeringly expensive. If players manage to harvest large amounts of it near Jool (which is realistic, by the way- Jupiter actually has large amounts of antimatter particles trapped in its magnetic field as well...) and ship it back to Kerbin, they *should* be able to make an enormous profit off it- considering just how valuable and rare it would be as a research and (eventually) energy resource in real life. Regarding Helium-3, Wikipedia and their source-material both concur that the price of it is sharply on the rise. Prices have recently reaches as high as $2,000/kg, are are likely to rise further. Thus, it would make sense to give it *at least* equal to $2,000/kg (in 2010 dollars- the year prices are cited as reaching that high), and likely higher as it is an extremely scarce resource that is only going to become more rare in the future (and KSP-Interstellar is well into the realm of futuristic technology by the time players unlock He-3 utilizing fusion reactors...) KSP-Interstellar has a UF4 and a ThF4p/sub] resource- the latter being Thorium TetraFluoride. Which is a real material, by the way, and far from "crazy". ThF4 is regularly used in optical coating, and was supposedly once used in carbon arc lamps according to Wikipedia- Thorium is much, much, much more stable than its scary cousin Uranium, and is only "mildly" radioactive... Thorium is an important resource that KSP-Interstellar needs to keep. It allows superior performance in Molten Salt Reactors, but at the expense of higher Actinide production. Not that the latter should actually be a problem- Molten Salt Reactors are currently being studied for use as "garbage disposal reactors" much like the current CANDU heavy-water reactors, and should be able to burn Actinides for ThermalPower as long as new Uranium/Thorium continues to get mixed in (the Actinides have to form part of a fuel-mix with Uranum or Thorium, they won't burn on their own...) Theoretically, a Molten Salt Reactor would never have to actually remove any Actinides- it could just keep adding fresh Uranium/Thorium in and burning up the existing Actinide wastes for additional efficiency. Thermal Power production would be reduced as a result however... Which reminds me, does anybody have some good data on the relative Thermal Power and reactor temperatures that would theoretically be achieved by running a Molten Salt Reactor actinide-rich (such as to consume the Actinides as reactor fuel) as opposed to filtering out the actinides? I believe ThermalPower declines substantially, but reactor temperature increases somewhat- and my initial instincts are to estimate the decreases in ThermalPower and increase in reactor temperature at around 20-30% (vs. Uranium at the very high levels of enrichment that would be utilized for rocketry applications) and 5-10%, respectively. However I could be way off, and I would really appreciate some reliable numbers on the subject... Regards, Northstar

Yeah, that's a better (more precise) number than 1200 kg/m3, and should definitely replace the 1200 number I used as an initial approximation (as I was unable to find sources that agreed on the precise density- all sources gave a slightly different #, so I went conservative and low-balled it...) Good work on finding that! Where did you find that data, though? Regards, Northstar

I'm not so sure about that. The heat radiators still have to have structural integrity. The further it extends out from the main fuselage the more support you're going to need closer to it in order to keep the radiator structurally stable during low-g engine burns (ones that aren't powerful enough to break the radiators) etc. Interestingly, this is one of the few trends that works against the "bigger is better" pattern that normally otherwise holds true in real-life rocketry (bigger fuel tanks require proportionally less insulation and cooling to hold cryogenic fuels, for instance, due to the Square Cube Law- a fact that is currently reflected in the relative power requirements vs. volume of the 1.25 meter and 2.5 meter Nitrogen Cyrostats...) Regards, Northstar

Yes, they could. The module posted by RoverDude simply produces IntakeAir in oxygen-less atmospheres (as indicated by "resourceName = IntakeAir") rather than producing a separate resource in oxygen-less atmospheres (which is IntakeAtm). It wouldn't even necessarily be intentional for many players- they might not know that there isn't supposed to be Oxygen on Eve, for instance... (it isn't exactly a perfect analog of Venus to say the least- it's got OCEANS ) And if they're using RAPIER engines in auto-switch mode, they might swap to airbreathing mode if they detect IntakeAir even though there shouldn't be any Oxygen available... How do you get around this RoverDude? Because the module you posted doesn't avert this issue on its own. Do you have some sort of direct link between the intakes and the engines? Not that it really solves the issue for engines in KSP-Interstellar, etc. which rely on the standard intake system to generate intake for their oxygenless atmospheric-propulsion systems... In short, the IntakeAtm resource needs to stay- unless you can show some better solution than the module you posted... (which simply disables the check for Oxygen in the atmosphere when producing IntakeAir) Regards, Northstar