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NASA won't be cancelled, and their budget will remain as it is. It has been very consistent in the long term in constant dollars since Apollo. NASA, like military bases, national labs, etc, is not going anywhere since it was intentionally spread among as many districts as possible (including 3 high electoral vote states). This has been true since the Washington Administration's frigate building program. Constellation wasn't going to work. People need to give up on the "apollo" model, it's not a thing any more unless we have a new "Cold War," to generate a new Space Race. If the chinese start claiming they own real estate on the Moon, perhaps, and claim large chunks as sovereign territory. Short of that, NASA will plug along, forced to buy what Congress wants (because the right people make hay from the pork). Never forget that Apollo was the biggest porkbarrel ever.

The thread title says NOW. Elon Musk? Where do you calculate 6 or 7 years? Be specific why you chose that number, and not 5 years, or 8, please. They actually claim that the reactors don't exist, themselves, and would require substantial increases in reactor research. Perhaps "aggressive" doesn't click with you as a use of language? Aggressive means a very serious commitment, very aggressive means maybe Manhattan Project or Apollo. Neither will happen for reactors, period. They are being very careful about that, why aren't YOU? Meh. They are selling something. Really. Radiation has been well characterized in terms of what crews will be exposed to, it's a risk, but a known risk, they are hyping it to sell their product. They should think about designing their own reactor, as they seem to require one for their drive. Their drive would be like me designing a NTR, but not providing the reactor. I have a pump, and a nozzle, give me a XXXX MW reactor that masses Y, and we have a great rocket. Except the reactor doesn't exist. Will of governments, lol. All government money is spent via politics by definition. Do tell how NASA ends up blowing a huge chunk of budget on a novel reactor design. We'll wait. NASA is forced to buy stuff they don't even want, like SLS. The other parts for a manned Mars mission--which is exactly what we are discussing---are pretty much fixed. The mass can drop here or there by small amounts, that's it. They have said what they require, and that reactor by their own admission DOES NOT EXIST. Period. If you say that this is easy in 6-7 years, show us an actual reactor they can use, or just admit you are making stuff up. Actual, meaning it is built and tested, or will be quite soon. NASA will not again see that level of largesse heaped upon it. Not ever. Try to be realistic.

Go into the game folder, and find "saves" and copy those folders someplace (like your desktop). You can then drag the saves back to the new version. Dunno where steam puts stuff, I have KSP installed a few places on my mac (one in "Applications" for the kids, and I have one in my user folder (modded) as well.

LOL, that's a surefire way to get robotic greenhouses!

This is nonsense, though. Nothing "drifts towards a target," it must be accelerated to intercept the target. That initial acceleration means a burn, which is detected, as soon as the light arrives. That also presumes that the attacker actually knows where the target will be months/years in the future. If the target is a planet, just throw rocks, obviously. As ship to ship, it is simply not a thing. What you are positing is a form of mine-warfare basically, which is fine to a point. Space warfare = seeding possible target areas with mines. Gotcha. Except that to really be mine warfare, you'd need to seed them into an orbit around a target planet, if they are just passing through, they are not a meaningful threat. As cold as possible is still hot, and clearly visible compared to the background. Any ship that does anything proactive at all is detected. Again, drifting mines might be quiet, particularly if they are impact fused. If they have to have sensors, and a way to attack at range... then not so much. If they are accelerated to an intercept, they will drift through the presumably target-rich area very quickly, too. Imagine there is a non-zero chance of you having a warship in orbit around Pluto. The "mine" is New Horizons. What are the chances you are hit, or even within range given it was set on the path many years before? Effectively zero.

Both are still not happening any time soon. If the power system is not already rated for use, it's a solid 10 years away at the soonest---and that's for stuff already designed. You cannot meaningfully reduce the payload for a manned Mars mission. NASA reference architecture in that regard is basically minimal for the required safety/redundancy. No one is arguing that chemical is the ONLY way to explore the solar system, here, either. The question at hand is VASIMR alone, and how reality compares to the claims they are making. For VASIMR, they not only need nuclear power systems, they need them to be arbitrarily low mass. THAT is the question, really. It presents a design target for the nuke-Es, but that doesn't mean that they can hit that target, there could very well be fundamental limitations that make creating hardware to this arbitrary standard quite difficult. It's also important to remember that this is an engineering question. In the real world, engineering is not just making stuff, it's making stuff that meets the appropriate standards AND is cost-effective. It might turn out that a 1kg/kW reactor is so expensive that it would be prohibitive. Cost matters. What I want is irrelevant. I might want to cut "programmatic" spending by the US government by 50%, and give all that money to NASA, instead, but that won't happen. NASA exists in the real world, and they must prioritize what they pay for. It is frequently true in the real world that achieving 75% of a high-standard goal might cost X, and getting to 90% of the goal specs costs 10X, and getting to 99% costs 100X (made up numbers, but you get the idea). Making a space reactor would be expensive. Making a super light space reactor might well be possible, but prohibitively expensive to develop. - - - Updated - - - I saw the Topaz delivered (the russians brought it in an Antonov, that plane was huge), then out at the lab (Sandia). The trick has always been conversion, which is why something like NERVA makes so much sense relatively speaking---it is far less challenging.

You would not dodge in reaction to the target looking like it was going to fire, you'd simply dodge constantly. If you can move 1 ship radius (cross-section, as viewed from the threat) in an unexpected way during the flight time of the weapon you almost certainly dodge the shot. So think of it as randomly translating using RCS. Your flight path is pretty much unchanged, but looking at you, you'd be wobbly. As the range decreases, this becomes impossible, and every laser fired always hits. Note that for missiles, which necessarily are on collision courses, the fire control solution is even more trivial, and so any anti-missile system using directed energy becomes limited only by how many missiles it can kill per unit time. And the stealth issue always ends up argues because people want it to be true, even though it's just not. Space is big, and cold, and space warships are hot. The only SF solution is to posit great directional radiators, which presumes that you know where the enemy is in the first place. BTW, the enemy knows where his own forces are, and can communicate via lasers, which is more directional than radiators would ever be.

Everyone is detected, all the time. (assuming they are close enough to be a threat in any meaningful timescale) Far enough to be out of sight means "not a threat for many weeks, months, or years."

BTW, on topic, no one is arguing that we could not make possibly arbitrarily large fission reactors for space use given time and money, but the OP states that VASIMR is ready for the 39 day journey NOW, and the document written by its own engineers says exactly the opposite (that even the slightly longer trip would take aggressive R&D for a nuclear power source, and that it would need to be very aggressive for the 200 MW version). Unless someone imagines a political change that allows NASA to blow a substantial % of their budget on a Manhattan Project push for a huge space reactor, the current development of such reactors will be no where near even the lower tier of "aggressive."

Given how poorly science pays, being below that pay grade makes someone a McDonalds worker We are not talking about reactor cores, we are talking about systems that create electricity. VASIMR wants electricity, not heat (a reactor core is just a heat source). Scaling up, as Rune points out is non-trivial. Also, you'll note that I provided an example, the HOMER-15, which is in miniature, very similar to SAFE-400. 70kg/kW. On top of that, SAFE-400 does't actually exist, it's a design. I actually used to host visiting students for the guy who is one of the primaries for SAFE-400 for his Space Nuclear Power meeting (ISNPS) (which resulted in some serious fun with Soviet nuke-E students), he's been working on that design for a LONG time in one form or another (possibly as long as you've been alive, depending on your age), and it is still just on paper.

You can detect at extreme ranges if the enemy is maneuvering at all. Dead quiet, you can detect them at merely large ranges. All weapons have effectively quite short ranges. Decently long range might be x-ray lasers.

You presume to know where the enemy detectors are by saying "behind a moon." In a SF universe where people/beings are fighting with each other, they'd then put sensor satellites all over the place. You're behind a moon? So is their sensor.

Tiny, quiet/dim probes are be definition not maneuvering enough to matter (if at long ranges). Again, you need to nail down the universe. What kind of total dv do ships typically have? Is a quiet probe a threat if it takes 10+ years to reach the target area?

Your Everest analogy is wrong. The effort required (which requires a constant influx of supplies) to mine both at ~8000m and the moon might exceed the benefit. In your example, the sherpa miners would require enough O2, and other deliveries to work, that while the effort to move it to camp 3/L2 (the route would drop below camp3 to the other side of the mtn, then climb above camp 3) would be less than from basecamp/earth to the destination for a single trip, the net gain would be near zero, actually zero, or possibly worse than bringing straight up. You need to land supplies to the mine, and you need to lift the tanker. If you have cryo fuels, then you have to do all this an exceed boiloff losses into the bargain. Obviously it depends on the material being mined. For most of the moon it's just plentiful O2. In polar areas, water is possible. Regardless, it might turn out to make more sense to drag an asteroid or comet to the Lagrange point, and just process it there. - - - Updated - - - To everyone else reading this thread, this describes you. You're out of your pay grade. Name some space reactors that have actually flown, or have been built and tested full-sized and quote their power densities, please. We'll wait. The 2 best designs (unflown, unbuilt) are SP-100 and SAFE-400 at ~50kg/kW and the SAFE-400 (also 100 kWe) is tricky to get the total mass of as the core is 512kg and each heat exchanger is 72kg---the design has 127 heat pipe modules hooked to exchangers, so either they share a few 72kg changers, or there are 127 of them (9144kg). I've seen a couple references to the actual total mass of the SAFE-400 being 1200kg. Regardless, it's not actually a reactor, it's just a design for a reactor. The actually tested HOMER-15 (similar to SAFE-400) is 214kg total for 3 kWe (71kg/kW).

Any sufficiently interesting (or effective) propulsion system is also a weapon.

I wasn't saying depots were a good idea at all, actually. I was saying that anyone who thinks that lunar mining makes sense should be willing to look at places easier (in dv terms) to get to/from. It's dubious that lunar mining would get you more than an offset in landing costs. All the propellant still needs to get to the spacecraft. That it is already high up the gravity well is great, but it had to get there, and the propellant has to get there as well. It's like having O2 at Camp 3 on Everest. Yippee, but a bunch of Sherpas had to bring it there.

Why a lunar source of propellant? Phobos and Deimos are actually closer in dv terms including bringing it back to an earth moon Lagrange point.

Back in the early 90s, we were writing rules for semi-realistic space combat for traveller (rpg) and of the 2 astronomers among the "gear heads," one was an IR astronomer who worked on the IR telescope at Mauna Kea. He said that equipment he had (diameter of telescopes, and required integration times (assuming it was in orbit instead of on a mtn) he could scan the entire volume of sky in several hours able to detect a crew cabin at 293K out pretty far (many light minutes as I recall). Not a SF warship radiating gigawatts, a player ship being dead quiet except that they are in shirtsleeves. Obviously a small region around the sun would be excluded. As a reality check, from the Earth the sun is about 30 seconds of arc wide. The excluded solid angle is pretty tiny, so to be useful you need to have a precise sort of warp/jump drive that drops you within that solid angle of all detectors, then you need to accelerate radially. Virtually any "stealth" case anyone can come up with is a special case. Remember, if you posit a universe where directional radiators are perfect, etc, such that stealth is a thing... then those societies will have many more sensors spread everywhere to compensate. In a realistic universe where stealth just isn't a thing, then they might only have a few sensors, making special cases sometimes possible. This is why I said that questions like this cannot be generalized, you need to state your SF universe. If you are claiming the real world, then no stealth.

If you redid all the current contracts with the sole caveat that they be "Not 100% idiotic," there would be about 10-20 contracts in the entire game.

I'm with Nibb31. Anything remotely realistic would not use manned craft. Assuming a sufficiently advanced society that actually uses manned craft which might become targets, then I'd likely put countermeasures on those and have drones for active combat.

This is a question that requires a full statement of the assumed tech available, and what laws of physics are or are not broken by any SF tech. You also need a context (what would they actually be fighting about, etc).

Funny, the people actually making vasimr say outright that it would take aggressive pursuit of nuclear to get 4kg/kW, and very aggressive to get below that, yet angellestat seems to think 2 is "easy." I'm sort of curious where he does nuclear engineering, since he otherwise sounds entirely against that technology.

I like the non-inflatable current nature simply because there are other options if you want inflatables right now (and Porkjet has said he'd update his at some point). I'm fine with inflatables, they are good, too. For this mod, I could see an inflatable hallway connector as pretty useful. Really, though, any longer term hab would be covered in regolith. I think it would be neat to have a state-change for them maybe if a drill is attached. After operating for some time, the models change to a buried version. Dunno if that would ever be possible.

I honestly have no idea for ISS, but as it is low-temp, it's likely pretty large (thanks, Stefan-Boltzman and those pesky black-bodies!).

Not in her district is no defense. My kids would not suggest that, and they are still in grade school (admittedly, pretty nice schools---but Lee must be really smart to get into Yale, right? (lol).).