NERVAfan

IIRC quite a few deserts and evaporating environments have perchlorates in soil on Earth e.g. in New Mexico. I don't think they're a game-changing problem for Mars. Something that needs to be considered and mitigated for safety, certainly, but nothing really crazy. (From what I find, the toxicity of perchlorates is not that high. Potassium perchlorate at least was used as a drug to treat thyroid issues, and apparently still is in some countries. It is still toxic, of course, but as usual 'the dose makes the poison'.)

http://www.jpl.nasa.gov/news/news.php?feature=4549 Curiosity didn't find brine, just measured conditions that would be favorable for brines to form. For solar power, definitely; but if you have nuclear power, it may not be so bad. Mars is cold, but its air is very thin, which should reduce rates of heat loss.

CubeSats have a set of standard dimensions/specs. 1U = 10x10x10 cm, <1.33 kg. And then the larger ones are built up from that (2U is 20x10x10cm, 2 1U cubes stuck together; 3U is 30x10x10 cm).

Ions are just niche anyway -- KSP-system delta-V requirements are very low and nuclear engines are available.

Mars-in-Venus's-orbit wouldn't be habitable due to its low gravity & lack of magnetic field - it would lose air and water (likely faster than in reality due to being closer to the Sun). Venus in Mars's orbit... I don't think anyone really knows. Its higher gravity might mitigate the loss...

Some people, maybe even most, sure. But there are people who would be just fine (especially given modern entertainment). Human psychology is pretty variable, and hermits exist. It's not analogous. The Sahara is extremely politically difficult, and there isn't a "dream" attached like Mars. (And no Elon Musk type figure pushing it.) If Mars is colonized, it won't be for resources - shipping resources across space doesn't work anyway. But a Mars colony would attach the kind of people that would make it an innovation hotbed, IMO. And information is cheap to send between planets

I think doing it with 1 person would be better. Less mass, but more importantly, you're IMO more likely to have violence with 2 people cooped up together than 1 person is to have deadly health problems (no one to catch an infection from, etc.) I don't see why not, actually. If it was 1 person... 500 days at 5kg of supplies/day... that's only 2500kg. And water is dense. You could probably fit it all in. And there are *some* people who would be fine cooped up in a tiny space for 500 days.

On Earth, yeah, but Kerbin orbital velocity is only like Mach 7-8.

I think some solar sail proposals could get to the outer-outer solar system within a few decades too.

WISE ruled out a large gas giant such as Tyche, which was supposed to be in the inner Oort Cloud. A Super-Earth (smaller than Uranus/Neptune) there would probably not have been seen. Nemesis (a red or brown dwarf) would have been even more visible in that kind of survey, since it would put out much more heat.

Sure, it's quite dangerous, but the level of regulation applied to it is way out of scope for its actual danger. Even counting in the radioactivity, there are much-less-regulated chemical compounds which are far more dangerous (in terms of smaller LD50) like Botox. Also, there's the matter of ease of exposure - an alpha emitter has to get inside your skin to be dangerous, while there are plenty of highly toxic chemicals that can slip right through skin (and some even through gloves like dimethylmercury). Benzene, a common industrial chemical, is a carcinogenic highly-flammable (flash point well below room temperature) which can affect people through skin exposure. Really strong oxidizers will react violently with pretty much anything, including common fire-extinguishing agents and even rocks. Etc.

Sure, but the biomass is tiny compared to the mass of oxygen in the atmosphere. The CO2 levels might become problematically high, though. There may well be a huge amount of very deep endolithic bacteria, but I'm not sure whether their metabolic products actually enter the atmosphere or ocean, and anyway their metabolism is glacially slow (1 cell division per century kind of thing). I don't think the ones interacting with the ocean in black smokers/cold seeps are that abundant since their habitats are small & localized.

OK fine but what does that mean in practice, IE with the classic go back in time and prevent yourself from being born type examples? I thought field theory was a quantum thing not a macro scale thing. What does the macro scale reality look like?

Yeah, that sounds very hopeful in terms of more realistic aerodynamics.

Yeah, exactly. - - - Updated - - - In some things, I can see that, but I don't see why more realistic physics would make it less fun.

For me, though, it tends to lead to the kerbals getting lost in space since it's hard to control...

So how are the paradoxes resolved?

Oh, certainly, but the protection needed is a lot less extreme. IMO both 'space capsule' command pods should have heat shields built in, but not lander cans - as implied by the "won't survive atmospheric entry" text on one of the lander can descriptions. The spaceplane parts, IMO, should be able to survive hypersonic flight, but would have trouble with a steep reentry.

Sure, but that's not going to be affected by digging up of fossils over 1 million years old. Whether you think ergaster, erectus etc. are all one species or not, it's still a separate 'out of Africa' migration event from the sapiens one.

When did 6U cubesats become a thing anyway? I saw them mentioned as secondaries on some other mission... I thought there were only 1U, 2U, 3U.

Lead is a toxic heavy metal too, but I've never heard of attacks using lead as a weapon... There are 40 jillion toxic things in the world. EDIT: well, yeah, bullets are lead... but not because of its toxicity...

Well, most of the oxygen removed now is due to animals & decomposing fungi/bacteria/etc, and these would die off quickly (many within weeks, scavengers/decomposers/detritivores would live significantly longer) due to starvation. From a search, the mass of oxygen in the atmosphere is vastly greater than the biomass, so the rotting away of most life wouldn't reduce it much. After that, it would be geological processes, which are slow (most rocks are oxidized already). A search gives me about 4 million years, but that's to remove all of it, and I don't know whether it's a linear decrease or what. But, very roughly, it would probably take hundreds of thousands of years for the oxygen to drop to unbreathable levels. Maybe longer depending on who you are -- if you live in the Andes or Tibet with low oxygen partial pressure, you might be able to live at sea level with a significantly lower oxygen concentration.

It should be pretty forgiving anyway, given that orbital velocities are at least 3x lower which means 1/9 the kinetic energy.

I just updated to 0.90 and now the TWR of rockets seems too low. I have a 12.7 ton rocket on the launchpad and a LV-T45 isn't lifting it (I even right clicked on the engine and saw that the displayed thrust was definitely high enough, so it's not a throttle setting problem). Is this a bug or did they change Kerbin's gravity or something?

Ok, but even then, I still don't understand why methane is so good. I don't see what it can decompose to except elemental carbon and hydrogen gas... but elemental carbon shouldn't be a gas at 3200 K (which is what those numbers are for). Looking for phase diagrams it seems to be at least 4000 K for gaseous carbon even at zero pressure. So shouldn't the carbon be falling out of the exhaust as a solid and actually making your specific impulse worse by effectively losing 3/4 of the mass you put in (or ejecting it at very low velocity)? Whereas ammonia should decompose to two gases.