NERVAfan

Can that be right? Molecular weight CH4 = 16, NH3 = 17, H2O = 18. Why is the difference between them so big?

Not really. It modifies the "out of Africa" migration for early hominids esp. Homo erectus, but I don't see how this affects it for Homo sapiens, ~1.3 million years later. There are several different migration events involved but only one really involves 'modern' humans. There were already people who thought a lot of the other stuff should be lumped into Homo erectus so I don't think this is game changing. (Generally early hominid related discoveries get announced as "this changes everything!!!!!" but that doesn't necessarily mean much.) IMO early hominids are massively over-split anyway because everyone wants to discover a new one (At least the genera are.)

Not surprising; it was in a metal casing. Isn't that an alpha emitter eg extremely non penetrating? Plutonium is not the ultra death stuff many people think. It's really nasty inhaled but that's about it (toxicity by other routes isn't that high although eating it is still a very bad idea); there are plenty of purely chemical substances that are far, far more dangerous (at least for a sub-critical mass of plutonium) because lethal exposures happen much more easily (e.g. dimethylmercury slipping through gloves and skin like happened to Dr. Karen Wetterhahn). (And heck, the lethal dose of botulinum toxin is far smaller than plutonium - smallest of any known substance in fact - and it's used for cosmetic purposes...)

Yeah... IIRC SpaceX plans for their methane/LOX Mars engine (Raptor) to have 380 specific impulse in vacuum, which is good, but still a lot less than 450-460 for LH2/LOX.

It has been; that's how we know Pluto has an atmosphere in the first place. It's probably somewhere in the general order of magnitude of 0.1-1 Pa, yeah, maybe a bit more at certain times... but it actually seems to be thickening now as Pluto moves out of its summer. http://www.planetary.org/blogs/emily-lakdawalla/2013/09051420-plutos-atmosphere-does-not-collapse.html I don't think that's true. That's about what you'd get at 80-90 km altitude on Earth, at or just above the mesopause, and IIRC you can't even get close to completing one orbit at that altitude. And a faster object has more drag.

The only dinosaurs that are described as venomous are the Procompsognathus and Dilophosaurus. EDIT: I think those people at the tropical disease lab say something about reptile saliva being allergenic or something early on, but they don't even know that they're dealing with dinosaurs.

I wonder if you could use aerobraking (once we know how high the mountains, if any, on Pluto are). Pluto's atmosphere is really thin, but if you came barreling in at that speed, it might slow you enough...

Sulfuric acid contains hydrogen, so you could get it from the clouds. EDIT: I'd imagine you'd want to use a rocket fuel you could make on-site, to minimize the mass, likely some kind of hydrocarbon that could be made biologically from Venus's clouds/atmosphere.

I set up the Gemini / Titan GLV stack on the launch pad as shown in the post above... then went back to the VAB to remove the 3rd Kerbal who had somehow stowed away on-board After that issue was resolved, I launched the rocket. The two Titan stages provide plenty of fuel to put the capsule into a fairly high LKO, with lots of margin left over. (The Gemini here also has much more delta-v capacity with its O-10 Monopropellant Engines than the real one would have... but using any of the other monopropellant tanks would have messed up the vehicle's appearance, so I had to use the largest one.) I placed the capsule into a moderately high LKO with the GLV, circularizing at about 160km. Our brave Kerbonaut replicates Edward White's pioneering EVA. After successfully completing the "tethered" EVA, the capsule returned safely to Kerbin.

Not just on paper - an actual ground test got 542 seconds Isp. The HF in the exhaust is indeed an issue on the ground, but wouldn't matter much for use in space. The whole molten lithium/cryogenic fluorine thing is probably the deal killer.

I think the 48-7S should keep the same specific impulse but lose a lot of thrust... maybe down to 15 or even 10.

Yeah. I would prefer to see the Mk2 Lander can and Mk1-2 Commmand Pod mass decreased rather than the Mk2/3 Cockpit mass increased. You can just put a Mk1 command pod on top of a mk1 lander can and it's way less mass than a mk2 lander can.

A follow on to Project Mercury: http://forum.kerbalspaceprogram.com/threads/102300-Project-Mercury Here is the Gemini capsule (using a Mk1-2 Command Pod as the base as there is no stock 2-kerbal command pod and the Mk2 Cockpit isn't really the same thing at all) on a Titan II GLV (Gemini Launch Vehicle). I used a LFB as the first stage since the Titan II GLV has a 2-engine cluster on the first stage. (The 2nd stage uses a Skipper.)

I agree you shouldn't "lose" explore contracts by getting somewhere too early.

I think both the Mk1-2 command pod and the Mk2 lander can should be slightly lighter, compared to their 1-kerbal versions. (Unless life support gets added and the 2.5m parts have longer endurances.) EDIT: also, if heat shields/reentry damage are added to the stock game and the command pods don't have built in heat shields, they should also be lighter, as that seems to be the justification for the Mk1 command pod being heavier than the Mk1 lander can. (Also, if they're not assumed to have heat shields, they are way too heavy relative to real-world capsules, given their much smaller size. Mercury capsule was more like 1.8m, Apollo 3.9m, Orion is going to be 5m.)

Not really. At the altitudes we are talking about, the pressure, density, and temperature are extremely Earthlike. The chemical composition is different, but it's pretty well understood. Everything involved can be tested just fine on Earth; it wouldn't be hard to expose the envelope, etc. materials to a replicated Venus atmosphere. I don't think planet-to-planet transport of physical resources makes sense. The availability of resources is important to support a base/colony locally, not to export to Earth. The export of such a colony (whether Moon, Mars, Venus atmosphere, asteroids etc.) would be information - it would probably create a highly-innovative culture producing all kinds of advancements.

How is that required/enforced across multiple countries?

IIRC NERVA style NTRs have problematically low TWR since reactors are heavy. I think chemical lower stage/NTR upper stage is better. Using NTR as upper stage also makes launch pad disasters much less problematic. An unactivated reactor is probably realistically less nasty than hypergolic propellants (U-235 is radioactive, but not THAT radioactive with a half life over 700 million years, and subcritical amounts are only a problem if they get inside the body - especially lungs - anyway as it's an alpha emitter skin blocks alpha particles quite well.) But an activated-then-destroyed reactor is very radioactive since it has fission products with short half life/high radioactivity (and non alpha emissions I think). NTRs might be much less likely to have destructive launchpad accidents than chemical rockets, since they aren't inherently explosive like fuel/oxidizer combinations, but I think getting permission for nuclear upper stage is going to be very hard already... nuclear launch stage will be worse. Yeah, it seems awesome, if only it could get full funding... (maybe after SpaceX develops 1st stage reusability, other people will be looking at reusability more...) IIRC jet engine TWRs are very bad. Potentially very awesome - there doesn't seem to be much effort/money being put into it though.

Even on purely technical (not political) grounds, I'm not sure it would be all that awesome given the reactor dry mass and shielding mass, etc. (It might be, but it's not necessarily an automatic win - you'd have to do a trade study vs. chemical options.) Even if SSTO was a requirement, chemical SSTO is entirely possible with off-the-shelf technology IIRC, just not especially practical in terms of payload fraction. And if Skylon gets developed.... EDIT: Well, I guess on purely technical grounds you could do an unmanned launcher with much less shielding, as jfull says. Still, many payloads probably won't like massive radiation doses. EDIT x2: Don't get me wrong, I'm a huge fan of nuclear propulsion (hence my username) but I don't think solid-core ones are really worth it for ground launch -- they make awesome upper stages where specific impulse is most important. If you had a "Nuclear Lightbulb" (closed-cycle gas-core) that might change, and Orion (external nuclear-pulse) is awesome for ground launch... assuming you ignore those political/environmental concerns

We'd definitely need an unmanned precursor airship mission, possibly more than one, and we'd need to test the deployment of the airship and the launch-from-airship techniques in Earth's atmosphere, but I don't think it requires any fundamentally new tech. Launch of small rockets from balloons has been practiced for 60+ years, and launch of orbital rockets from airplanes is known technology (Pegasus). I don't see why launching from a blimp is so fundamentally different. (And I doubt the airship would deploy at high speed - I'd imagine it would be packed into a much smaller entry capsule, use heat shield and then parachutes to decelerate to a safe speed, then deploy/inflate the airship.) I think we will almost certainly go to Mars first, since there is much more interest in Mars both inside and outside NASA* - but Mars isn't on the "critical path" to Venus - if someone funded the Venus program and no one funded a Mars one, then it would be possible. *In my opinion, NASA is too bound to the short term election cycle and too risk averse to do a manned Mars mission themselves. If humans get to Mars, it will most likely be either a largely private mission probably with some NASA and/or ESA participation (the most likely, IMO) or a Chinese (or another non-US/Russia space agency like India or something) mission.

Go ahead, that would be great to see!

Also, oxygen has higher molar mass so hurts your specific impulse. Oh, definitely, but it would be nice to see in the final version.

I'd like the Stayputnik to get SAS functionality back and stay where it is in the tree, and add a 1.25m, Command Pod Mk1 shaped "Sounding rocket nosecone" part at Start or Basic Rocketry that has no SAS and is heavier.

I can see that, but I think having 1 kind of LiquidFuel represent UDMH/kerosene/hydrogen fits the level of abstraction KSP mostly uses, while the oxidizer thing is just an unnecessary inaccuracy. So I'd still like them to burn just LF. And technically you can use other things (ammonia/methane) in nuclear engines... but you wouldn't get KSP's 800 seconds specific impulse. EDIT: And actually the specific impulse of the LV-T30/45, LV-909, Skipper, Poodle are closer to methane performance than kerosene or hydrogen.

Well, what I was saying is that since KSP uses an "abstract" single type of LiquidFuel, the heavier airplane tanks could represent both structurally-reinforced kerosene tanks and less-volume-efficient hydrogen tanks.