NERVAfan

Oh, it could happen. But a failure during launch from Cape Canaveral or the ESA site in French Guiana (though not Baikonur) would drop it in the ocean, which isn't a big deal for human health (probably not entirely environmentally ideal... OTOH radiation isn't so much of an ecological problem, it's more of a human health/quality/length of life thing; Chernobyl is pretty ecologically OK. You aren't going to cause enough cancer to make animal populations non-viable short of something like a nuclear war.) And there's not much point in using nuclear propulsion if you're not going beyond the Moon, so such a spacecraft shouldn't be very likely to crash on Earth (EDIT: after launch). It's a risk/reward thing. The risk isn't zero, but it's small enough that the benefits for spaceflight are worth it, IMO. Also, the chances that even potentially-lethal radioactive fragments (like the Kosmos 954 thing you link to) would actually harm someone are probably not that high. Most of the Earth is ocean, where they would sink and be lost; much of the rest is unpopulated or nearly so, desert, tundra, icecap etc. The Kosmos 954 bits fell in Northern Canada; what are the chances someone would actually have encountered the potentially-lethal bits if they hadn't been actively searched for? EDIT: So the risk of it actually failing in a way that would drop dangerous debris onto Earth, combined with the risk that that debris would fall in an area where they would actually harm people, is not very high.

^ This. I wish they'd remove the radioactive exhaust bit from the engine's description. It is misleading, and nuclear propulsion technology already gets too much bad press.

I tried to install this in 23.5 and it doesn't seem to work... I still get "cannot warp faster than 1x when the ship is throttled up" when I try to use ion engines, and I don't see any other sign the mod is installed. Exactly where in the KSP folder is the "NBody" folder supposed to go to make it work correctly?

Right. The LV-N is a solid core NTR (you can tell because a gas core NTR would have much higher specific impulse), it is only releasing radioactive material if something has gone wrong and the reactor elements are being eroded away. If it is working as intended the uranium (or whatever) is staying in the reactor. They would be fine to use in real life except that people are irrationally paranoid about radiation. I think the comment about radioactive exhaust in the part description is a joke... unless the designers got it confused with some other engine, not sure.

Awesome!!!

These would be very cool.

I would like timewarp and outside-range to preserve rotation too... the current version leads to weird conservation-of-angular-momentum violations.

Eh, the smaller KSP asteroids are not that big, and the Hoba meteorite (over 60 tons and 2.7x2.7.x0.9 meters according to Wikipedia) landed intact without artificial aid. So with a heatshield and parachutes, landing an A class asteroid doesn't seem that implausible... it's just "extreme sample return". I think the problem doing it in RL is more "you want to hit Earth with an asteroid??" (plus, we already have lots of meteorites that fell naturally). Also, detecting an asteroid that small is not at all easy.

It's only 35,000; the game's thrust units are kilonewtons. EDIT: so 35 MN is 23 1/3 Mainsails. Or 10.93 of the new KS-25x4 engine clusters.

Right, I get that, but the planet still has a significant atmosphere. It's not a wisp like Mars.

Yeah, but that hasn't happened yet. I was talking about ISS up to now, not future plans. The Russians have already done space flights longer than one year. Also, the ISS radiation environment is not the same as deep space or Mars, so no matter what you do at ISS, people will still be able to say "it's too dangerous/untested". I don't think the background radiation (galactic cosmic rays; solar flares are a real problem but can be shielded against much more easily) is nearly as bad as some suggest; the idea that it's especially dangerous relies on the (very debatable) linear-no-threshold model. Even if you accept that model, the risk is not out of line for an early-exploration mission, comparing favorably IMO with (say) early 20th century Antarctic exploration. Also, radiation-induced cancer takes decades to develop, so for a Mars mission in 20 years people will be dealing with it with 2060s medical technology... by which point I'll be very disappointed if cancer is still highly dangerous.

Yeah, but it's still based on mass. The trojan asteroids don't disqualify Jupiter (or Mars, which has several also, or Earth, which has one known so far), nor do orbit-crossing asteroids, because the mass is tiny compared to the planet. Pluto's orbit is really eccentric, but it definitely doesn't constitute most of the mass in the 30 to 50 AU range (which is about its periapsis and apoapsis). For one thing, its periapsis is actually inside Neptune's orbit; plus, there's all the rest of the Kuiper belt out there.

I'm more than a bit skeptical of the "no magnetosphere = solar wind rips off the atmosphere" bit; as |Velocity| said above, Venus has no magnetic field and way more atmosphere than Earth. I have no problem with the solar wind removing Mars' atmosphere; but if that is what happened to Mars, that doesn't necessarily mean it would do it to an Earth/Venus sized planet with much stronger gravity.

Yeah, that's what I've heard, too. Though I've also seen it said that Venus's temperature with an Earth-level greenhouse effect would be hot but livable, so... I've heard that Earth had a much more greenhouse-y atmosphere, with much higher pressure (maybe not as much as Venus today though) early on since it had non-frozen oceans quite early when the Sun was much dimmer (the "faint young Sun paradox"). But Earth's oceans and plate tectonics etc. locked up the CO2 in carbonate rocks. I've also seen odd things like high methane levels mentioned (a book called "How to Build a Habitable Planet"). EDIT: apparently there's debate about how MUCH more CO2 though... apparently one study said <0.7 bar, when other people talk about 10+ bar...

Unmanned spaceflight has done tons since the Space Race ended, yes, especially in the last 15 years or so. But manned spaceflight hasn't really "gone anywhere" since Apollo. ISS is impressive in terms of orbital assembly, and size, but I'm not sure it's really gotten us any closer to going to Mars or whatever, despite claims. As for WW3... wars aren't going away as long as flawed human nature remains as it is. But I really don't think we'll see another "World War" in terms of a near-global conflict, or even an outright open conflict between major powers. The weapons available are too destructive, and economies are differently based than they were in the past so controlling this or that patch of resource-rich land is comparatively less important to national power, and national economies are too intertwined -- you'd be fighting your own trade partner so crippling your own economy if you destroyed their infrastructure. So wars will probably be limited to those in which at least one party is a minor "third world" power, at least until/unless we have colonies on other planets big enough to fight Earth or we meet hostile aliens, or technological civilization falls far enough that nuclear weapons and cheap, easy global trade go away. The one real risk would be a war based on lingering "Cold War" hostilities (eg US/Russia or US/China sparked over some territory like Ukraine or Taiwan) and if we get through the next 20-40 years without one (as I think we will) that risk will likely disappear as people who remember the Cold War age and retire, and the movers and shakers become people brought up in the post-Cold War world (if we assume people under 10 aren't really aware of politics, and the Cold War ended in 1991, then people under 33 now won't really remember the Cold War. In 30 years that 'critical' age will be 63, and a majority of Congress won't personally remember the Cold War.

I don't like the ocean being "commons" either; it leads to environmental problems with overfishing IIRC. As long as humanity is divided into nations at all, everything that humans can access should belong to one nation or another, so that someone is ultimately responsible for it. IMO. EDIT: And I don't consider the UN as really being a viable option for that "someone". It's not really equivalent to a national government. The Antarctic Treaty in a general sense isn't necessarily a bad idea, but the involvement of the UN is (Although, I think the 'ice' parts of Antarctica should have less regulation. The pretty localized/fragile coastal, etc. ecosystems definitely need protection, but lifeless ice, not so much.) EDIT x2: not that environmental problems are relevant to the Moon or asteroids. But there are other reasons for responsibility: unambiguous ownership of resources, protection of Moon historic sites (Apollo hardware/footprints), responsibility for potential destruction of other people's space facilities, application of labor laws to future space industries/bases/colonies... I don't see why a nuclear weapon would be more dangerous in orbit than on Earth. ICBMs can already hit anyplace.

I don't actually think it is a spacecraft. Just think it's an interesting SF concept.

I think nations would still try to claim bodies in space if they could, legally. Practicality is often irrelevant -- look at how much money and blood Britain invested into the Falklands War, completely disproportionate to any actual economic or strategic importance of the islands. And that would have gone even more so, IMO, for the US and Soviet Union at the height of the Cold War and Space Race. The cost would be vastly less than, say, what the US spends on its military.

Saturn's moon, Methone, is very round and smooth (egg-shaped) despite being only 3km, when most bodies of that size (or even much larger) are very lumpy. It also lacks craters. Apparently the explanation for this is that it's made of "ice fluff". But that's boring. So, is there anything we actually know about this moon that would prohibit it being a big, abandoned egg-shaped alien spaceship with a little bit of ice on top that has accumulated from the rings? (Yes, I know this is quite unlikely...) http://en.wikipedia.org/wiki/Methone_%28moon%29

I think nations should totally be allowed to claim areas of the Moon or asteroids or whatever, if only so that it's easier for private companies to get investment to do stuff there (less legal risk). I think it would make it easier for companies like Planetary Resources to get investment. Plus, I don't see any advantage in it... at all (it's not like we're actually going to see wars over the Moon or asteroids). So even a slight advantage would justify repealing it. --- And I do think Apollo might well have gone farther if we could actually claim (areas of) the Moon, and if the Soviet Union could have too. Without that, there was no political reason to keep going after we'd landed there.

I don't necessarily see a problem with some engines becoming obsolete, but... I really think the Mainsail and Skipper need a boost, even if the SLS ones do get nerfed. IMO the Mainsail should be 300 SL, 350 Vac and the Skipper should be 320 SL, 370 Vac like the LV-T30/45. Bigger engines shouldn't be less Isp than smaller ones IMO, clustering means more part count and worse game performance, so shouldn't be more efficient; and I don't think engines should lose performance, making existing designs useless, if it can be reasonably done without that.

Sure we do. Bury them in a desolate place far from any groundwater used by humans (say, Yucca Mountain). Volumes of high-level waste are IIUC small, and there are huge desolate deserts. Nuclear stuff is not actually that bad for the ecosystem except in very high intensities; what you'd get on top of a buried site isn't even close to that. (Even Chernobyl is mostly OK ecologically... yes, there are some differences in the soil fungi and so on, but mostly OK... the thing is, human health limits are set based on individual health, in ecosystem/conservation terms we are talking about the health of the population which is much more forgiving especially as e.g. cancer tends to hit individuals of post-reproductive age).

Nope. Global warming is a very real problem, but it isn't a "kill the species" problem. We will not end up in a Venus type environment; I severely doubt there's even enough fossil fuels on Earth for that. We might well end up in a setup like the Eocene or parts of the Mesozoic with no permanent ice cover anywhere and tropical-type species up through most of the temperate zones (several thousand years down the road, melting East Antarctica would take a lot of time, and those periods had really high CO2 levels, like 1000-2000 ppm range)... but while changing to that setup so quickly (in geological terms) would kill off a lot of species and cause massive disruptions, it's not a biosphere killer. Even with our other environmental problems... even if we end up in a severely impoverished biosphere dominated by opportunistic species and lose most of the unique and beautiful, irreplaceable biodiversity of Earth .... it's not going to kill off the human species. Plants will still make food and make O2/remove CO2, animals will still be around, soil biota will still recycle nutrients... humanity will survive. We're not talking something on the scale of the K-T mass extinction (and honestly I'd give humans decent odds of surviving even that... we're a lot smarter than dinosaurs and have very adaptable food requirements).

Multiple star systems with lots of stars are totally possible (Castor has six) but they don't look like the Firefly map. In reality, you don't get (or at least we've never seen, AFAIK) several little stars orbiting a big star like a planetary system. In any system that's stable enough to have evolved complex life (as Kerbin has), heck probably even to have gotten planets past the initial formation phase (don't know the exact timelines), it breaks down into binaries or single stars, and the different binaries are far enough apart to treat each other as single objects. Alpha Centauri, triple star system, is a binary (A and + a distant companion (Proxima) orbiting the binary as if it was one object. Castor, a six-star system, is a binary of close binaries, itself orbited by a distant binary. Of course, in KSP, we don't have N-body physics; the system treats the Sun/Kerbol as a fixed central point. So probably the option for minimum physics breakage is to give Kerbol a fairly close companion much smaller in mass (a red-dwarf scaled to KSP-scales) with its own very close-in planetary system; the smaller the companion is, the less its orbiting Kerbol rather than both orbiting a mutual barycenter will diverge from reality. If we want a third star, it should be significantly farther away (don't know what's good for stability; maybe at least an order of magnitude? I'm not an astrophysicist....) Of course, it would actually orbit Kerbol rather than the Kerbol-companion barycenter, but what can you do... So maybe you could have something like... Existing system from Kerbol out to Jool... (~68 million km per the Wiki) "Gas Planet 2" (with Eeloo as a moon), in a circular orbit a bit beyond Eeloo's current semi-major axis (~90 million km), say at 108 million km, RL Venus's semi-major axis --big gap-- New system, centered on a 'red-dwarf' maybe 70,000km radius (if we scale down from Kerbol) or significantly smaller (if we scale up from Jool) say 1 billion km from Kerbol (between Jupiter and Saturn in RL) Innermost planet, super-close, with lava oceans that destroy ships and continents of higher-melting-point rocks Tidally locked planet with an Earthlike star-facing hemisphere Super huge rocky planet (1000km+ radius) with 10 atm surface pressure and 2.5 or 3 g at surface Ice-giant (Kerbal-scaled, maybe 2400km radius) And then, if a third system is added, put it at more like 10 billion km... about where Eris is in RL...

Aw, I want to see the dioxygen difluoride engine! That's because at standard pressure CO2 goes straight from gas to solid or solid to gas; the liquid phase only exists at higher pressures (Wikipedia says only at 5.1 atmospheres and up).