architeuthis

Apologies if this has been asked before, I couldn't find anything after a cursory search: is there a way to turn off clouds just for Duna? I tried commenting out the section in the config file but it turned off all of the clouds (e.g. for Eve, Kerbin, Laythe and Jool as well).

Right P=F*Ve/2. Solar isolation works differently enough that solar panels can collect hundreds of times more power than on Earth or the PB-Ion is a perpetual motion machine of the first kind... I actually don't really mind that, the thing that bothers me is that we use ions for Hohmann transfers in KSP, but that is fundamentally different from how they are used in real life (not just balanced differently). I get it; gameplay, but low thrust is kind of the point of ion engines. The PB-Ion shouldn't be NERVA-lite, why not just ditch it and put in a 'Ant Jr." or some such?

If the NTR isn't ever fired then there is nothing particularly dangerous inside the reactor. In that case it is just another piece of space debris.

I remember a few years ago a friend of mine asserted that there would never be a space game with Newtonian physics that would gain any form of mass popularity. People wouldn't like that they couldn't swoop around in their spaceships as if they were WW2 fighter planes, and would therefore grow bored. I'm pleased that KSP seems to disprove the notion that space-based realism cannot also be fun. So you can probably tell that I don't care much for the "who cares if it's crazy unrealistic, it's just a game" argument. Nobody here is saying KSP should completely mirror reality, also nobody is saying we should ditch everything that makes KSP realistic. I think most everybody would like some combination of realitic-ish, and fun to play, so the discussion is about what that means to the game. It is fine to discuss that. It is also fair to discuss balance for single player games. The main thing I dislike about ion engines in KSP is that we get bored so easily we have to fundamentally alter them to basically be just another high-isp rocket engine, and force them to be something they are not. All ion engines are used for long duration burns, this is what defines them. KSP ions can only ever be aesthetically like RL ions. Interesting video. Thanks for linking that.

Felsmak, which mods are you using for that shot?

What would the point be? I assumed you had meant a reactor reentering after a very long stay in orbit. Are assuming that the NTR was powering the stage in question? Because otherwise the environmental and public health impact of lowly radioactive (e.g. Uranium 235) debris crashing to Earth may be less than the potential impact of a upper stage failure of a common rocket such as the Briz-M upper stage for the Proton-K which uses toxic hypergolics dimethyl hydrazine (UDMH) and nitrogen tetroxide as fuel and oxidizer respectively. Should we put parachutes on those?

The tyranny of the rocket equation means it may simply be too expensive in terms of launch mass to bring all that stuff along. This is why we use graveyard orbits (not just for nuclear reactors even, but also for geosynchronous satellites). For less than 100 m/s of dV you can throw space junk into an orbit that will be stable for over a 1000 years. Sure it's not exactly a "permanent solution", but its not terribly short term either. You could also dump stuff into a heliocentric orbit for just a bit more dV and then you don't even have to worry about tracking radioactive debris, and worrying about it interfering with future missions (same goes for ditching it in the Lagrangian points, except in that case you will know where stuff is without having to actively track it). Ideally we could launch the stuff into a solar system escape trajectory, but that is too expensive in terms of dV.

It also means that they don't need carry infeasibly massive batteries to maintain constant operation. The RORSAT orbit was so low they were occulted by the Earth for half of each orbit, and those big radar arrays were power hungry beasts. I read an interesting article recently. Orbit characterization done by amateur astronomers in the U.K. back in the 80's suggests that RORSATS maintained their orbits with ion engines. The RORSAT program is still classified by the Russians, but if true then this development scooped the design used by ESA's GOCE 'Ferrari of space' by several decades.

That first link touches on it. Drag coefficients are complicated functions of geometry, Reynolds numbers, Mach numbers, Froude numbers (for partially submerged ship hulls) and relative surface roughness effects, therefore determining them analytically is often only done as an exercise for simple shapes. More often they are determined numerically, or empirically. Typically for aircraft and rockets Cd is not highly dependent on Re because all else being equal Cd approaches a constant value for high Re.

As several people have mentioned above, nuclear reactors are relatively safe on the launch pad. Uranium 235, which is the fissile material most often used, has an extremely long half-life (over 0.7 billion years). This means that it is not very radioactive. If the NTR you're thinking of is anything like the old NASA NERVA, then it will have nuclear poison wires inserted in the reactor upon launch. Nuclear poisons absorb neutrons and impede fission reactions. Since there is no fission there will be no neutron radiation, or nasty fission products (short half-lives, highly radioactive) in the core which emit gamma radiation. Once the NTR is in orbit, you send up a space shuttle to pluck out the wires, and boot up the reactor. Only fallout worries in this scenario is if an old reactor has some kind of uncontrolled reentry. That would be messy.

The way I see it Apollo AS-201 through Apollo 10 were only engineering test flights. In a sense so was Apollo 11 and 12, though in hindsight it was obviously also a major PR coup, and as far as some U.S. politicians were concerned the whole point of the program (e.g. beating the Russians). Nixon actually considered cancelling Apollo after 11. Basically his thinking was declare mission:accomplished, and not risk a lost mission that could tarnish the record of achievement. This would have lunacy () in budgetary terms as the hardware for the later missions had already been built. Apollo 13 was supposed to be the first pure science mission, but we all know how that went. Apollo 14 through 17 were all science (especially the last 3), as was the truncated Apollo applications program (in the end, just Skylab). I actually tend to think that China's lunar ambitions (and manned spaceflight projects in general) are more of the nationalistic prestige variety, then of the ivory tower. The N1 wasn't the Soviet's only problem. IRC more than half of the Zond circumlunar missions were failures.

Power to 'em I say. It would please me to see any members of our species voyage beyond LEO. That said the the Chinese space program appears to be proceeding cautiously, and methodically by small increments. I think this is a smart, sustainable approach, but I don't expect they will have the technology or infrastructure to return to the moon before the US does. I'm sure they'll beat the Russians though...

Since the J2X got canned by congress's budget the SLS is largely an LEO rocket as well. The current block SLS will use a centaur upper stage with a single RL-10 motor. In terms of payload delivered to destinations in the outer solar system it is not radically better than a Delta IV-Heavy.

Sarge Rho, have you read Karl Schroeder's Permanance? You might find it interesting. He describes a slower than light interstellar culture based on brown dwarf way stations and relativistic mag-sail interstellar cyclers. It's pretty awesome. Here is a little essay he wrote about it.

Some things we can adjust to, other things perhaps not. Without actual long term study it is difficult to know. Sure that would be fine, but building 1.5km-radius torus stations doesn't seem to be in humanity's near term forecast. Unfortunately:( IRC 2 RPM is optimal for human comfort and 6 RPM is the lower limit of what most people can tolerate. For 1G of acceleration and optimal comfort you would need to have a radius of 245 m. If you settled for the lower limit you would need about a 27 m radius. Since even 27 meters is pretty damn big as far as any human space structures go, I call anything smaller than than this "a small centrifuge".

Practically speaking most hypothetical space station artificial gravity systems are effectively small centrifuges. Unless the angular velocity is low or the radius is very large Coriolis acceleration will make balance feel odd, especially for rapid movements that aren't parallel to the spin axis. The otoliths and semicircular canals in our ears basically measure linear and angular acceleration, our eyes give us a measure of attitude and orientation. If our brain get conflicting information from these different sensors it can be extremely disorienting. For instance moving your head around in a centrifuge can make your eyes hunt or spin (like after spinning yourself as a kid). It can also cause stationary objects to appear to be in motion. Also unless floors are machined to be curved to the radius of rotation then there will be an optical illusion of the floors appearing to be slanted or inclined haunted house style. We don't really know about long term psychological effects of these kinds of things, so artificial g systems will have to be carefully designed to mitigate this stuff.

I don't think fuel transfer via claw requires any more elaborate handwaving than KSP's laughably unrealistic fuel transfer system does already. Even if a satellite (or some other spacecraft) wasn't originally designed to be serviced, it will still have a fill/drain valve somewhere on its propellant tank. We can just assume that the claw refueling tool is able to autonomously locate the valve, and bypass its seals, and has a universal adapter to interface with it. There is a RL precedent for this technology.

I agree, but artificial gravity is not the same as real gravity. There are some pretty substantial physical differences that play directly into the psychological heath of astronauts who might use such a system.

OP: Great ideas! I would love to see more depth to this game mechanic! I was just thinking about this. It's possible that KSP solar panels generate colossally more power than any comparable human technology. The PB-ion info notes that it is not powered by witchcraft, however assuming it is %100 percent efficient it produces 20.6 MW of thrust power (P=T*Ve)! It draws 14.6 E/s which means the conversion factor is 1.4 [MW] per [E/s]. This means that a single humble OX-Stat panel produces 1.1 MW of power at Kerbin's orbital distance. This is over one hundred time the combined power of the ISS solar arrays! Any tiny power draws are a drop in the bucket compared to this. If Kerbol's solar insolation works anything like our own sun's, this is probably impossible (or PB-ions are perpetual motion machines of the first kind)... anyway I digress I guessing that the average power drawn by the communications isn't to far below the peak load. I read somewhere that the power breakdown for the ISS is something roughly like: ECLSS ...40% IS ...20% G&C ...5% Experiments, lighting, misc ...35% Where ECLSS is the Environmental Control and Life Support System, IS is the Information System (communications, tracking, computers and data management etc.), and G&C is Guidance and Control (navigation, IMUs, control moment gyros etc.).

+1 for space nuclear reactors, though to make them interesting I'd think there would need to be more power hungry components, and a waste heat dynamic. Regarding fuel for the LV-N, I don't think it's really very necessary. The NERVA 2 was expected to be good for close to a hundred restarts before neutron poisons accumulated to the point that the reactor would need to be replaced. In KSP terms that is dozens of missions for a single vehicle. Practically speaking a lot of other parts on your atomic rocket will need to be replaced before then. Ditto for RTGs. Plutonium 238 has a ninety year half life, solar panels degrade much faster than that. A typical solar panel may loose half of its power generation capacity in 15 years.

Since the delta-v to make a plane change is approximately dV=2*v*sin(theta/2), you want to do the burn when you are going as slow as possible. The best place to do that is at apoapse after being captured by the mun. This is generally what I do when I want to rendezvous with my Munar polar orbit space station. Here is a handy guide from a 1970's era NASA technical document about reusable nuclear shuttles for lunar missions:

With constant use neutron poisons would gradually build up inside a LV-N reactor core until they reached a concentration which snuffs out fission reactions. If they are anything like NASA's NERVA2 then this would have happened after around 80 engine restarts, which for me corresponds with about 10 Duna missions. It's a waste of delta-v to bother landing a derelict atomic rocket on a planetary surface, so I use a space tug to offload any remaining surplus propellants, and then shoot it into a heliocentric orbit. From an early 1970's NASA technical report on Reusable Nuclear Shuttle disposal modes:

The KSP LV-N is infinitely throttleable without any effect on isp. IRL reactors take a bit of time to 'warm up' and the NERVA2's isp would suffer initially because the hydrogen would still be cold. After you withdraw the control rods and turn on the LH2 turbopumps you burn as normal, then stick the rods back. Since the the reactor stays hot for a while after you put the rods back in, you don't want the fuel elements to melt and the LH2 propellant is effectively acting as reactor coolant you would have to keep running the turbopumps (effectively continuing the burn, but at very low isp) until it was safe to turn them off. If the reactor is bimodal (unlike NERVA), then it is essentially always on and you don't have to go though all this rigmarole. This is what Red Iron Crown describes.

Great post rdfox! Was the Apollo program a f**k up? Actually on a marginal costs per ton to LEO basis the SLS will be a whole lot cheaper than either the Space Shuttle or the Saturn V. I just hope NASA has enough money left in their budget to fly some interesting payloads on it. But that's not a NASA problem, that's a congress problem. Have a little faith.

Beautiful model, it is very homeworld-esqe.