NERVAfan

I'm sure that was the purpose. But it's unnecessary from a modern perspective, IMO; only high tech, wealthy nations can exploit space, and those nations don't go to war with each other (not overtly anyway) anymore. It would be too destructive, and not worth it anyway.

Oh, certainly; I don't think the Outer Space Treaty is a particularly good idea. If nations were allowed to claim land on celestial bodies, we might well have a base on the Moon now, and economic exploitation of space resources would be much farther advanced. Without that, there was really nowhere to go after Apollo. "Common property of mankind" sounds high-minded, but it leads to either abuse of resources (as in the oceans) or lack of ability to use them in the first place (as in Antarctica or space) in practice.

Of course there is; nothing made of complex molecules will survive at arbitrarily high temperatures. But we don't know what that limit is. I'm pretty sure it's no higher than the critical point of water since supercritical water is, from what I've read, really good at destroying organic molecules; but that leaves quite a big range. What holes? Desulforudis audaxviator, a sulfate-reducing bacterium, has been discovered 2.8 km underground in the Mponeng mine, one of the deepest mines in the world. There just aren't that many holes that deep. Did any of the super-deep drilling projects (Mohole/Kola Superdeep Borehole) look to see at what depth they stopped finding microbes? I never heard of anything like that, and chemosynthesis wasn't discovered at the time of Mohole. Compared to Earth, yeah, but the individual photochemistry reactions can be quite energetic (due to high-energy UV photons). But this still provides a way to store energy (solar energy -> chemical energy by photochemistry in the upper atmosphere). These chemicals could then fall down to the surface and feed living things. It'd be a very energy-starved, limited ecosystem compared to what we have on Earth's surface, but compared to low-energy endolithic biomes where a microbe might divide once every century? I don't think it's unworkably low-energy. Well, low compared to what? IIRC Titan's sand dunes are supposed to be organic stuff, so the amount of complex compounds isn't that low. Plus whatever higher hydrocarbons might exist mixed in the methane/ethane seas (and the atmosphere has several % methane vapor). There are plenty of organics around, not just nitrogen. Well, sure, but you've got that photochemistry feeding more energetic/reactive substances into the mix, so it's not really analogous to your classic lab organic chemistry. (Plus the possibility of weird catalysts/enzymes. Life absolutely depends on enzymes as catalysts. Nitrogen-fixing bacteria can do nitrogen fixation at room temperature and pressure; the industrial process is done at something like 400 C and 200 bar). I'm not saying Titan does have life, but I think the possibility is definitely there, and would be worth looking for if we could find a way to identify it (its processes would necessarily be very different from ours; even the basic chemistry would be different since there is a serious lack of available O atoms - at Titan temperatures water is a pretty inert rock - so you wouldn't find stuff like carboxylic acids [as in amino acids] and sugars playing a major role.) Apparently it does, thus the plumes on Europa too. But if a meteorite landed in the throat of a plume-geyser, or landed on a part of the surface that then cracked open to become "chaos terrain"... and there are those salts on the surface... there does seem to be surface-ocean interaction. I think it's very unlikely that it would happen (I'm pretty skeptical of even Earth-Mars transfer of life by meteorites, and that doesn't have the intense radiation environment, ice shell, and lack of a braking atmosphere) but maybe not impossible.

Essentially, though I don't think they think it's a quantum effect - it's supposed to have something to do with the nature of inertia/inertial mass.

That's not the physically questionable part of it; that's just straightforward mass-energy equivalence. A charged battery or capacitor should by mass-energy equivalence have more mass than a discharged one. (Very slightly more mass - one kilowatt-hour = 3.6 megajoules = 4 x 10^-11 kg = 40 nanograms). Unless I am missing something... But that doesn't help. If you are charging and discharging the capacitor in a closed system, the mass-energy of the system isn't changing (because it's a closed system and energy is conserved). As I said, the Mach Effect/Woodward Effect idea (as I understand it, anyway) is that the charge/discharge is just a "spark" or "on switch" and the real energy comes from outside (from the entire universe, in fact). I think it's unlikely to be correct, but I'm not sure it actually violates conservation of energy or momentum because (in the idea) the 'Mach drive' spacecraft isn't really a closed system and is exchanging energy and momentum with the universe at large. (I don't see how they get around FTL communication problems with exchanging energy/momentum with distant parts of the universe, though.)

You can't really do "several orders of magnitude" better than that, as that's an exhaust velocity of a bit over 1.5% of the speed of light! If you can manage a mass ratio of 10, you could get a cruise speed of almost 5500 km/s (about 1.8% of lightspeed) which would get you to Proxima Centauri in 236 years, Barnard's Star in 327 years, or Epsilon Eridani in 582 years. That's quite workable for a generation ship IMO.

I dunno - there have really not been that many orbital launch vehicles, and most of those come from really just 2-3 "traditions". There's plenty of room for cultural biases and historical contingencies to exclude plenty of viable options in a world that small (e.g. the SLS is being built the way it is to use Shuttle heritage, despite the fact that the reasons the Shuttle was designed the way it was don't apply to SLS at all). New LV makers like SpaceX and India may be starting to change this, but the barrier to entry is so high that we're very far from exploring all viable options. (And I think there is a strong cultural bias that space stuff is necessarily super-high-standards, super-expensive. Cubesats and SpaceX's vertical integration may be beginning to change this, too, but that will be a long process if it ever happens.)

Yes, there will be a depth limit defined by temperature, but I think the extremophiles there are very poorly known since there are very few holes that deep. We don't know what microbes, if any, are 2 miles below most of the land; only when there's already a way to get there, like the super-deep mine in South Africa, do we get a chance to see what's there. Also, we don't know what the temperature limit (and thus depth limit) for life is. Clearly there is one -- enough heat will destroy any molecule -- but these environments are not well sampled and the current record holders (Methanopyrus reproducing at 122 C and "Strain 121" reproducing at 121 C/surviving at 130 C) are recent (2000s) discoveries. So there may be more discoveries to come. Also, these are hydrothermal vent organisms; the deep endoliths are AFAIK even less known. Titan might be workable. Not for Earth-type life, but it does appear to have complex chemistry. I agree it is highly unlikely, but there does seem to be some surface/ocean interaction on Europa (plumes, and salts found on the crust) so it wouldn't be entirely impossible for a life-bearing meteorite to enter Europa's oceans if it hit in just the right place and time. And being inside a meteorite would provide some shielding, at least. I'm not sure if anything would survive the actual collision, though, with no atmosphere to brake it.

In general, yes, Earth life would have trouble on extraplanetary environments. Europan hydrothermal vent environments might actually be very similar to Earth hydrothermal vent environments, though. (OTOH I don't think you are going to find hydrothermal vent bacteria on humans working on spacecraft assembly, so it is probably fine). Some Earth endoliths might be able to survive in the Mars subsurface, if there is ever any trace of liquid water at all, but again these are not human-commensal bacteria. There are "polyextremophiles" though... but I would expect Mars or Europa bacteria to be better adapted to a Mars or Europa environment than terrestrial generalists. Add a metagenomics experiment (analyzing environmental DNA samples). If it falls anywhere on Earth's tree of life, it's contamination; if it doesn't, or if there is no DNA at all, it's native.

I have a feeling that this is something that might make a lot of sense for a regular Earth-Mars service, but not early on. IMO early expeditions will accept a quite high radiation risk (less shielding mass) and go with very small habitation volumes (so it probably won't be NASA, but somebody less risk-averse, like a private group or China or maybe somebody else like India).

I think their concept is that that is just an "on switch" and the vast majority of the effect comes from energy ambient in the universe - "gravinertial flux" IIRC. It has something to do with the Mach's principle concept that inertia comes from the sum of mass-energy in the universe, or something like that.

I think some of the Woodward effect people suggest exactly that. Although maybe not just extraterrestrial but also from our future... or something.

I think the initial life detection mission to Europa should fly through (a very thin part of) a plume, collect water and look for microorganisms, DNA/RNA, proteins and other complex organic molecules in it. This is way easier than getting through the thick ice and has vastly less contamination concern... and if you find life or biomolecules you might actually be able to get the funding for an ice drilling/Europa submarine mission.

I decided to make a Mercury Redstone and fly an Alan Shepard-style suborbital mission. The stock launch escape tower is horribly oversized for a Mk1 pod, so I tried to imitate it with 2 sepratrons on a stack of Cubic Octagonal Struts (with a tiny-size decoupler to jettison it). However, when I tested this, the capsule blocked the thrust. So I attached the sepratrons to the capsule itself and kept the strut tower just for looks. The rocket itself is made of 1 FL-T800, 1 FL-T400, and 1 FL-T200 with an LV-T30. The stock fins are way too big, proportionally, so I used Small Hardpoints to imitate the Redstone fins. Miteny Kerman was assigned to fly this mission. Here it is launching: And the capsule reentering in flames after a brief trip to space: And a safe recovery:

There's a whole book (out of print for a long time but now available on Kindle) called "The Green Flame" about the US boron fuels project in the 50s. I haven't read it yet though so I don't know how good it is.

As for the original question, I'd say mid-to-late 2020s (12-15 years from now) if SpaceX does it (or is the leading partner/technology developer & sells services to someone else); 2030s or 2040s if China does it and if their demographic problems don't ruin their economy and thus technology before then, which is very possible; late 2030s to never if NASA does it.

Steam engines can burn wood; you could go from wood-burning steam engines to ethanol as liquid fuel to solar/wind/nuclear. Without fossil fuels, you wouldn't be able to industrialize on a large scale until later in the development, but it wouldn't be impossible to get there. (And once you did, you wouldn't have to replace a pre-built fossil fuel infrastructure, which is a big part of what's slowing us down going to renewables - the fossil fuel infrastructure is already paid for.)

That makes a lot of sense; but the title of that article is a bit misleading. It's mostly talking about using existing microorganisms.

Sure, but I was taking the "really wanted to" assumption of this thread as "willing to accept a very large risk". OTOH I actually do think colonization will require accepting a huge amount of risk anyway and this isn't necessarily out of line. From what exactly? There aren't many other lifeforms on the planet... You would have some margin for this reason (and would bring stuff like Spirulina that is incredibly calorie dense per cubic meter of growing volume, so you'd have room for margin). You'd have margin and time to fix things. If it's plant-based, your recycling should be pretty well closed by default, so you won't need input that often. That's why you have redundancy. (And I think that is a bit overstated; "minutes" is I think much faster than CO2 would build up to lethal levels with no scrubbing or temperatures would drop to lethal levels with no heating). And if you use your food plants for CO2 scrubbing/O2 production that would be hard to fail completely (barring the thermal control going way wrong - that will be very critical so need a lot of redundancy). Sure, some resupply is required (early on anyway). Well, Mars One got a lot of volunteers, and that's without much chance of getting the money necessary. So quite a few I think. (And from what I've heard, a lot of people really fall in love with Antarctica, and did even back in the days when it was incredibly bad conditions - that's why people like Shackleton and Wild went back over and over again).

True, but that was due to conflicts with the inhabitants, not a problem on Mars. But my point was that they were intending to colonize from the very beginning.

Sure you could. Doesn't need any super-special life support systems; the ISS or Mir lasted way longer than a Mars mission. Sure, they're resupplied, but that's purely a matter of bringing enough supplies (IE enough launch mass), which can be handled by launching enough rockets. Absolutely no reason to use either. Dragonv2/Falcon Heavy architecture; they'll be ready sooner, for one thing, and will be vastly cheaper. You don't. You make minor modifications to hardware for other purposes - Bigelow module for transit habitat, Dragonv2 for lander. This only works for a one-way/Mars to Stay mission though, but that's fine... It makes a lot of sense though. It doesn't necessarily mean you have to commit to staying forever; a return vehicle could always be sent later. And if your plan is to colonize from the start (which makes sense, IMO - the trip times are long enough that you might as well) you don't have to have the ability to return at the start of the manned activities - it can come later. Heck, Columbus' first expedition dropped off a colony, so colonizing from the very start isn't particularly weird.

Right, but if SpaceX succeeds, it may be quite soon. And given the time lag to develop rockets, starting developing a fully expendable rocket, even now much less after they demonstrate recovery & reuse, is betting that they will fail. And through vertical integration/bypassing traditional aerospace suppliers with higher costs, IIRC. Well, they are definitely following the reusable path. And I don't see why it requires a huge launch market expansion immediately; the expendable -> reusable transition will be a gradual thing. (The current plan is that only the 1st stage will be reusable on the Falcons; full reusability will wait for the next rocket). SpaceX's long term plans do indeed require a gigantic expansion of the launch market, but that's actually pretty plausible at the prices they seem to be expecting for later vehicles. No, it wouldn't, but I think they are projecting much much bigger price decreases than that. Probably not immediately, but as reusability develops. Sure. I'm not disputing that. What I am talking about is the potential system where you can launch a 10kg or 20kg (or, in the long run, 50kg or 100kg) smallsat for the current price of a 2U cubesat. In the very short term, that is probably true. 15 or 20 (or even 10) years down the road... there will probably be more. (Planetary Resources, Bigelow, etc. - plus stuff that hasn't even started yet.)

I think what will really be the game changer is if/when they succeed at reusing the first stage. Not just for what it does to their own prices, but what will others try to do to compete? That's when I can really see something like Skylon development getting funded; in a world with a half-reusable F9 and FH, there's not much point in developing a plain old expendable rocket. That's kind of my point. Cubesats are incredibly limited, yet there have been a huge number of them in a comparatively short time. If larger satellites could be launched for cubesat-like prices... EDIT: I don't expect any of this to happen quickly. Creating new markets will take time, as will developing 2nd generation (post-Falcon) reusable LVs. But 15 or 20 years down the line, unless SpaceX fails completely at reusability, the picture will be very dramatically different IMO.

If we found aliens on Mars or something, and were willing to accept a lot of risk... yeah, a one-way mission could probably be done in ~4-5 years. Pitch a bunch of Dragonv2's to Mars with Falcon Heavies, stick a small Bigelow module to the one carrying the people (the rest are cargo), land them close together. The mass you could land would be very limited, so if the resupply mission didn't launch in the next launch window, you'd be dead. But it could probably be done. EDIT: And with infinite money it might be sooner than that. I was thinking 4-5 years because the commercial crew stuff is supposed to be 2017 (3 years away), but that could probably be accelerated somewhat. Dragonv2 would probably be the last thing ready, BEAM and Falcon Heavy are supposed to fly next year.

(my bold) How do we know that? IIRC there never has really been a dramatic drop in launch prices. I agree that current industries (eg comsats) aren't going to buy 10x more launches if launches are 10x cheaper. What I'm arguing is that totally new things will quite likely appear. EDIT: Look how many cubesats have been launched in the ~10 years since cubesats were invented. There is quite a bit of interest in space; the prices just make it out of reach for most purposes.