KerikBalm

Well open cycle is generally only bad if it results in fission products in the exhaust. You should be able to minimize that with the centrifugation, but yea, I don't know if it can have "clean" exhaust. There's the closed cycle gas core as an alternative as well

@KSK Well, you can eliminate the need for Cesium by using Red-Mercury to make super conducting magnetic coils so that even paramagnetism is enough, and most heat that gets to the coils will be stored as chemical energy, which you can then use in a pinch to trigger fusion for a temporary boost in power. Look, it has its own wikipedia page and everything, its not proven beyond any doubt that it doesn't exist: https://en.wikipedia.org/wiki/Red_mercury On another note, I have been in a discussion through PMs with someone opposed to unicorn farts, and in favor of metastable metallic hydrogen. They continually declined to offer any argument as to why mmH is on better footing than unicorn farts... and then started to ask me to help make the argument for them. When I said no, and that they made the claim, the burden was on them to back it up, they said: "I'm doing you a favour, the least you can do is help." I kid you not...

Well they have shown 2 types of PSM engine in the game. One is PSM mixed with water, and the other is PSM confined by adifferent shade of PSM, whith some cesium decoration. Stats for PSM (ie, stats for what you'd get if metallic hydrogrn were substantially metastable): PSM+ water: 538 Isp; PSM + lH2: 1090; PSM^2: 1700 The PSM+water engine could be replaced by a solid-corr NTR with LOx augmentation: http://www.projectrho.com/public_html/rocket/enginelist2.php#lantr Isp: 647 -> Better than the PSM+water engine The PSM^2 engine could be replaced by a liquid core NTR, or a closed cycle gas core (A "nuclear lightbulb": Gas core, closed cycle: http://www.projectrho.com/public_html/rocket/enginelist2.php#basicgcr 1,100 to 3,200, relatively conservative predictions are more around 2,000. This exceeds the PSM^s 1,700s Liquid core ( http://www.projectrho.com/public_html/rocket/enginelist2.php#ntrliquid ): Probably around 1,630 s -> very close to the PSM^2 engine, but possibly as high as 2600. Consider that uranium/plutonium has a different melting point than other materials. You could use another material with a higher melting point to contain it: https://www.asminternational.org/web/cmdnetwork/home/-/journal_content/56/10180/25655039/NEWS since you can apparently get material that wont melt at over 4400 K Certainly 4150K : https://en.wikipedia.org/wiki/Tantalum_hafnium_carbide The simplest way would be to melt your fission fuel in a container of this material, and inject hydrogen into the molten mixture. The fission fuel is melted, the engine container is not. A more advanced engine will use active cooling, and another molten fluid. Example: a Hf-Ta-C container, with molten tungsten, and molten uranium. Now, due to fissioning in the center, and cooling of the exterior, the highest temperature will be at the center, and temperature will decrease as one moves away from the center. So now you can have the fluid at a higher temperature than your container... and you can heat the fluid to the point that it is nearly boiling. You centrifuge the whole thing to keep the fluid pressed against the walls. Of course, this is fine for a cylinder, but you need to have a nozzle at one end. So you could again rely on active cooling (as we already do with rocket engines), and if neccessary, use of a buffer gas (like injecting cold lH2 just along the edges), that cools the exhaust in contact with the nozzle, while leaving the core/center of the exhaust still very hot. Closed cyle gas core (nuclear lightbulbs) also would rely on the use of a bufer gas vortex inside actively cooled quartz glass to keep the uranium gas from contacting the quartz glass and melting/vaporizing it. This lets the interior get much hotter than the glass wall, and rely on emission of radiation which quartz is transparent to (but so is hydrogen). That radiation escapes the glass, which has hydrogen floying past it, and a dopant is injected into the hydrogen that absorbs the UV radiation coming from the quarty "lightbulbs", and heats and expands the hydrogen. I think you'd have to design your dopant injection well so that the hydrogen directly in contact with the quartz glass is not mixed with dopant (otherwise it would heat up and melt the glass too). These engines rely on temperature differentials, with difficult engineering problems to keep the solid parts from melting, but they certainly are possible. I really don't understand why I need to keep making this point over and over again. Which part is not clear? There is precisely 0 evidence for metallic hydrogen being metastable. No theory predicts it will be, no experimental evidence using pure hydrogen, isotopes, or alloys shows any metastability. The source of the idea that it might be metastable comes from one paper, from 48 years ago, using disproven models. At this point there is equal evidence for metastable metallic hydrogen, as there is for pixie dust and unicorn farts. Unless you can provide some evidence to argue that this is not the case, please have the intellectual honesty to admit that including metastable metallic hydrogen is the scientific equivalent of including pixie dust and unicorn fart engines, and you want to include those anyway.

No, it doesn't, and this is going off topic [snip] And the whole point is that it is something for which there is no evidence for its existence, and ample evidence against its existence, but not beyond any doubt And I realized that I can edit the poll without voiding the results. It now says Unobtanium

[snip] I'm trying to avoid bias by not using a hot button example. I would hope categories are voted for on their description, not any particular example, so that there is a more objective assessment of the general idea of what belongs. What category any particular engine belongs to is for another thread

@Bej Kerman The distinction would be that the engineering challenges don't require a material that may not even exist/ be possible. If an engine will only work if pixe dust exists, and pixie dust doesn't exist, then its not an engineering challenge, now is it?

Well, its a rocket using "a material with certain properties exists, which almost definitely does not exist ". The performance specs are intentionally vague. Maybe I should have called it "unobtanium" instead of "pixie dust", but its essentially the same thing, a rose by another other name... you know FWIW, the warp drive example doesn't neccessarily imply FTL warp drive, because in theory, warp drives could also result in slower than light speeds.

Well, to me, my standards depend on the context. If something tries to give the impression that its realistic, I will expect a certain level of realism. If its something that is clearly not intended to be realistic (the Witcher, for instance), then I give it a pass as long as its fun and not too ridiculous. I would argue that many of the developer's statements amount to an implicit claim of realism for various elements of KSP2 (propulsion technology more so than life support and colony mechanics), this also combines with the history of overall realism of its predecessor, to create a context where I expect a much higher realism standard for this game compared to say... Halo. Of course, I normally give passes to things that are abstracted/simplified because of limitations of the game engine/computational power (patched conics vs N-body physics, small planet size so that terrain can still be reasonably detailed when viewed from the surface), and situationally for gameplay (deep engine throttling, infinite restarts), or some combination of gameplay and engine limitations (no thrust on rails of KSP = I excuse the much too high ion engine thrust; No persistent vessel rotation when on rails = I excuse the lack of reaction wheel saturation mechanics) My bad, I just assumed it was you, because when I checked, there was only 1 reply (yours), and only 1 other person had voted, so I assumed the vote came from you.

@Master39 Whether they play it to learn or not is, I think, beside the point. Many people will learn as a byproduct of playing, but not the goal. The question is whether people believe that what they see in the game corresponds to reality. While this is a rather esoteric subject, in general I think spreading misinformation is very harmful. On another note, I should have changed hte order of the 4th and 5th options. I also wonder if @Master39 could explain his reasoning why he voted in favor of: "Tech that is only possible if a material with certain properties exists, which almost definitely does not exist", but not "Tech that is only possible if a material with certain properties exists, which may not exist" Were you just voting based on the examples given, and not the more generalized category? If I were to further specify that "pixie dust rockets" allow FTL, would you vote the same way?

Dealing with the temperature on Moho would be trivial by using radiators edge on to the sun - at least trivial compared to the challenges of interstellar travel, gas giant mining, and setting up self-susitaining off-world colonies in the first place. Energy storage for the long nights would be a bit of a problem, but nuclear power could supply that. Or you could set up a colony at one of the poles, with a solar/radiator tower to always have an energy supply and heat control. KSP 2 supposedly introduces axial til, and Moho's orbit is already inclined, so I'm not sure how well a polar colony would work with just solar power. Anyway, I see no reason why a moho colony can't work... but I also see no reason to make a moho colony: its unlikely to have much in the way or material suitable for propellent. Maybe, as in some sci-fi, you can make antimatter at Moho, using massive solar collectors to supply the massive amounts of energy needed? Eve colonies would be much more difficult, given the thick atmosphere would make using radiators quite difficult. You could run a refrigeration unit, and expell even higher temperature atmosphere outside your colony, but the power requirements would be quite high, and the solar power available is fairly low... the conditions are much better than IRL venus though.

I'm just curious where people think the line should be drawn for KSP 2. If some choice is unclear, or you think there is a category of tech that should be included that I have left off, please mention it.

If nearby star systems are 0.4 to 1 light year away (1/10th scale, so like proxima centauri - Epsilon Eridiani in real life), and you can get to 10%c, then it takes 10 Earth-years of game time to get to nearby stars. This is about 10x as long as it takes to get to Eeloo by hohman transfer, but still quite reasonable. Time dialation at these speeds would be insignificant. Its only 1% difference at 14% c, and still less than 10% at 40%c. As long as they don't make these engines powerful enough to go beyond about 0.5c, the time dialation effect can be ignored. I think we don't need to worry. Also, if we did have separate time warp rates, your time to reach the nearest system would be the same. You see, if you were going at near light speed to a star 10 light years away, it wouldn't take 10 years of ship time, it would be nearly instant in terms of ship time, because lenght contraction would make it seem like the ship wasn't 10 light years from the star. So if its a 10 light year journey, and there's one time flow rate for players, the playing time to reach that other star will be the same with and without relativity, even at 0.99c. Sure at 0.99c your time warp rate will have to be much lower than the time warp rate for a player doing an inter system-hohman transfer to Eeloo, to stay in sync... but your ship will not be making a 10 light year journey from its perspective, but a journey much much shorter. So we're just limited by syncing times for players, which yields the same problem as if relativity is ignored, and you want to go interstellar, while someone else wants to go to Mun from Kerbin. At least... that's my understanding of it...

As already mentioned, if you are firing a particle beam at near light speed, making the particles antimatter would have a negligible effect. Why do you insist on using antimatter where it doesn't make sense?

Its pseudo-science at this point. There was one paper from 48 years ago, using a now thoroughly disproven model, that predicted the possibility of metastability. In the 48 years since then, no model predicts metastability, and no experimental evidence shows any hint of meta-stability - the experimental evidence includes alloys and isotopes, in addition to pure protium mH. The only response possible is that our knowledge of the universe is not perfect, which applies to literally anything, unicorn farts included. [snip]

I was thinking it might be an animation from some sort of ore processing/refinery module. It clearly doesn't look like its going to be picking up stuff from the ground, given its design and how far above the ground those colony modules are. Given that they abstract supply routes, after you've done a flight between places (or something like that, Nate Simpson merely commented on someone's guess, saying that the guess was pretty close), maybe there will be similar abstraction for mining, and you need to deploy some sort of mining trucks/rovers for a colony to start the mining process? Perhaps you can have a rover garage, and the better your rover has been shown (by you) to perform, the higher the resource flow? We can engage in all sorts of speculation about mining with colonies, but I'm fairly certain that the OP's speculation is not backed up by any evidence in that video clip

That sounds like a much better thread. I wonder if there will be anything preventing Kerbin from being developed with colonies, if not, I will be making colonies on Kerbin, should be pretty easy. They've said that they don't have a funding system, but they've also shown a resource system, so mining will relate to manufacturing ability. They've also shown that colonies can have their own runways, so I look forward to developing alternate sites to recover 1st stage spaceplanes and such. Since I surely plan on rescaling the bodies and their orbits by 3-4x ASAP, it would be nice to have a facility east of KSC to recover 1st stages at

I often refer to a lot of Science fiction as Fictional science. Only "hard" Sci-Fi is actually scientific fiction, by my definition. I also like to call it: Fantasy, in spaaaaccceeee!!! which would includethings like star wars. #1) Energy weapons will be able to focus out to a diffraction limited distance. If you had a 30 meter mirro/lens, you can focus it doesn to a point at a certain distance, and between that point and the lens/mirror, it gets stronger with distance (like when you use a magnifying glass to burn something, holding the glass to close to the target doesn't work). As I mentioned, large focusing arrays and short wavelengths can get this ranges very high, to the point where the lag from the speed of light is problematic. #2) A missile using the same type of propulsion as a warship, will have more dV or the same, not less, as it will all be about mass fractions. If you armor your warship to withstand high speed shrapnel, it will certainly have less dV than the missile. Shoot down the missile far enough away, and it only takes a small maneuver to avoid the shrapnel. #3) It all comes down to the propulsion systems. If we were to engage in space warfare with current/near future tech, or lasers would not be good enough for anything other than point defense. Missiles would be used at long range, possible some kind of railgun firing a guided projectile (a gun-missile hybrid, which we already use very often in conventional warfare). Increase tech a bit more, where you have bulky nuclear (fusion?) drives that don't scale down well (and thus aren't suited for use on missiles), and high frequency lasers, and then it looks like lasers may dominate. Increase tech even more so that missiles can start achieving substantial fractions of c, then they can jink any laser shots at longer ranges (even 1 AU away allows them ot juse make a small maneuver every 16 minutes to avoid being hit), and start jinking faster as they come within about half an AU. With a good propulsion system and high speed, the transit time over half an AU is small, and they have the dV to jink until the very end (where light speed lag becomes insignificant, and jinking is useless) - giving laser PDWs a very limited amount of time to engage incoming missiles (whose shrapnel clouds will still be very deadly). So I'd say depending on tech level: Gun-launched missiles > lasers > relativistic missiles.

Care to explain why? Because its ridiculous to claim that "we've checked if there's no unicorn farts that can be used as rocket fuel" [snip] What a ridiculous and obviously false statement. Please cite our data regarding unicorn farts, and their properties that make them unsuitable for use as rocket fuel. Please tell me how you think the above quoted statement can be logically valid, but this one isn't: "We've got enough data to tell that there's no fuelling unicorn farts metallic hydrogen that is metastable at low pressure." Note: mere assertions neither constitute evidence nor a logical argument. "We haven't got enough data to determine if MH can be MS at LP unicorn farts can be used as rocket fuel." "We've got enough data to tell that there's no fuelling unicorn farts metallic hydrogen that is metastable at low pressure." These last two statements of mine are actually MORE valid than your statements, because we do have data on the properties of metallic hydrogen (suggesting it won't be metastable at any relevant pressure), and we have absolutely no data on unicorn farts.

I think that fusion drives could start getting you closer to 5% c, particularly staged fusion drives (but with 10% c dV, unless you are just doing fly-bys, you only head to the other star at 5% c). The end game "torch ship" drive, that has been speculated to use antimatter (pure matter-antimatter? or antimatter activated fusion, who knows?), would likely have fractions much higher. Even with these higher numbers, I think its not a problem (except maybe the torch ship) - I wouldn't scale C down to 1/10th our light speed - and the 1/10th scale means that even higher fractions of c aren't needed for interstellar travel, so you can stay at low c%s, and still get to other stars in reasonable time frames. http://www.projectrho.com/public_html/rocket/slowerlight3.php#gamma Note that you can get to 40% the speed of light before the time dialation factor (and lenght ocntraction, nad other weirdness) is 10%... which is enough for me to ignore, and enough that I wouldn't criticize KSP 2 for ignoring it. The atomic rockets guy sets his threshold at a gamma of 1.01 (not 1.10), which corresponds to 14% c http://www.projectrho.com/public_html/rocket/slowerlight.php Which is still faster than we are likely to see in KSP 2 with fusion engines (really not sure about the "torchship engine"), so I don't think its a problem (and yet I think other engines are a problem, so hopefully this also shows I'm not just complaining about any "future tech").

What a ridiculous and obviously false statement How did you determine this? How can you argue in favor of this statement in a way that wouldn't be equally valid by just replacing "unicorn farts that we can use as rocket fuel" with "metallic hydrogen that is metastable at low pressure"?

I'm guessing your point is essentially that, as Asimov put it, "Any sufficiently advanced technology is indistinguishable from magic" Any you can't be certain that unicorn farts can't be used as an even better rocket fuel. You can't be certain that magic doesn't exist/isn't real. Since the criteria you are advocating for is the lack of absolute certainty, and one can't be absolutely certain of anything (hard solopsim), it logically follows from your position that literally anything should be acceptable in KSP2, and there is no possible argument to be made against anything they put in, regardless of how ridiculous it is. [sarcasm]I will look forward to purple space magic engines, unicorn fart engines, GMO popcorn engines, and miracle drives alongside metastable metallic hydrogen engines in KSP.[/sarcasm] All of them are equally scientific!

"Metallic Hydrogen" is not magic - metastable Metallic hydrogen is. Stop conflating this. Furthermore, centuries ago, people were building internal combustion engines. An ICE engine was patented in 1794, 226 years ago, which is centuries ago. *edit- read explosions propelling cylinders and thought ice: rocket engines aren't explosions, but rockets have been in use since the 13th century. It would hardly seem like magic to them - while it would be very impressive, they would recgonize what the machine was doing You are again (and again and again) basically arguing "you can't prove its impossible beyond any doubt", which is true of literally anything, so a Unicorn fart engine is also equally magic with a metallic hydrogen engine, using your criteria.

Before the whiners come: Note that I am merely responding to a post directed at me, made 10 days after my last post on the subject of mH. It seems other people don't want to drop the subject either. Also, recently I was criticized for a lack of citations (even though I've cited all this stuff before), but I again find myself replying to a post by someone who seems not to have seen the citations, and isn't aware of the actual state of the science. Indeed, and we can't disprove the existence of unicorn farts as a viable form of propulsion, nor pixie dust. So would you would be ok if KSP 2 added unicorn fart engines, pixie dust, and purple space magic engines, alongside engines based in actual science? No one has been arguing otherwise. There's not much of a debate, fact is that a study came out in 2019, which apparently made metallic hydrogen, and measured its properties, and determined that it was not metastable. https://arxiv.org/ftp/arxiv/papers/1906/1906.05634.pdf *edit* I was getting citations from my old posts, but the paper is out of pre-print and past peer review now: https://www.nature.com/articles/s41586-019-1927-3 Biut we've already looked at alloys of it, because those are much easier to make, and they still need will 100-165 GPa of pressure: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2764941/ Even with lithium, you have over 1 kg of lithium for 1 kg of hydrogen% - pebble bed NTR outperforms it. We've also tried deutrerium- doubles the MW of the exhaust, and pebble bed NTR outperforms it. The Lithium alloying example linked above only allows the compound to be stable in the range over >100 GPa, so compared to a shuttle tank at about 250 kPa. 100,000,000 kPa vs 250 kPa... you need a tank holding 400,000x more pressure, if that is related proportionately to mass, then the engine is non-viable But that cited paper was a prediction, and like the predictions about mH itself, it underestimated the pressures (the ealier predictions had numbers much lower than 415 GPa): https://pubmed.ncbi.nlm.nih.gov/26056306/ where we see thos allows predicted to be metallic at around 100-165 GPa, remained non-metallic up ot at least 215 GPa), and further modelling predicted even higher pressures: https://pubmed.ncbi.nlm.nih.gov/28318270/ And another study of different alloys, but this time looking for superconductors at high temperature (and still hundreds of GPa): https://pubmed.ncbi.nlm.nih.gov/28630301/ https://physicstoday.scitation.org/do/10.1063/PT.6.1.20180823b/full/ (note that its not a prediction, but measured properties) We do have ways of saying, a "way of saying" is a prediction, we can turn to physics, and make predictions, which all say: No In summary: We've measured mH's properties, its not metastable. We've looked into alloys, they decrease the required pressure to form it, but fail to bring metastability, and still require pressures of over 100 GPa to stabilize it. These alloys would increase the propellent MW by enough to make it inferior to solid core NTRs, while requiring a tank over 400,000x stronger than what we make now (and not even carbon nanotubes would be strong enough to contain the pressure, as their tensile strength would be a maximum of about 63 GPa. https://en.wikipedia.org/wiki/Mechanical_properties_of_carbon_nanotubes So, lets say carbon nanotubes have about half the strenght required to contain a metallic hydrogen alloy (which will already suck because you have more lithium than hyrogen in it), 63GPa for the tubes, 126 for the alloy, or 50 for hte tubes, and 100 for the alloy (depending on how optimistic you want to be for each figure). Now, between 55-115 GPa, you also have carbon starting to transform into Diamond. (the general pressure being different than the tension that the tubes would experience) To contain such a pressure with a tank, using carbon nanotubes, you'd need the nanotubes enclosing the tank to be sqrt(2) the radius of the tank, so that the pressure is spread out over a surface 2x larger. Now, between the tubes and the surface of the tank, you'd probably have diamond, because that's what we currently use to contain high pressure metals made out of elements that are normally non-metallic (FYI, there's also metallic oxygen, metallic Nitrogen, etc, that can be made at high pressures, and these have been studied as well - they don't need as high of a pressure as hydrogen does... and none of them are metastable either). This means that for a tank of metallic hydrogen 10 meters wide, you'd need at least 4 meter thick wall of diamond, and then you'd have to wrap that in carbon nanotubes. Then as soon as you release even a little pressure, you get a BLEVE, just like tryingto use supercritical water as an energy storage. https://en.wikipedia.org/wiki/Boiling_liquid_expanding_vapor_explosion Which is not suitable for a continuous thrust rocket. if you want to say that we may be wrong, well, maybe magic exists, we may be wrong. Maybe pixie dust exists, you can't prove it doesn't! "You can't prove it doesn't is a horrible standard for including something in science fiction, you might as well, just have the "miracle" drive or the "god does it" drive. but ... yea... sure, just say I'm ignorant, because, despite all the evidence and science saying that its not possible... I can't disprove it in the same way that I can't disprove the existence of magic... ok then.

I think that you are engaging in wild speculation

Source for this/link with the specific time?