Kryten

I can quite confidently say that nobody has been killed, injured, or in any way inconvenienced by use of nuclear bombs for space propulsion.

You realise this will just convert your household detritus into slime mould crap, right?

Use of engines manufactured or designed in the Russian Federation is currently banned for national security launches, so Antares is a no-go. The Minotaur series already gets most of it's workload from the DoD; there's just not much demand in that class from them.

UDMH, as used most notably in all stages of Proton, has similar effects to hydrazine but with about twice the toxicity for acute exposure.

You don't need AI for uncrewed spacecraft maintenance, remote control from a ground station should work just fine. DEXTRE on the ISS has been operating this way for years.

I'm betting one, same as the Ansari X prize. It wouldn't get too far in lunar gravity, and would have a high chance of getting stuck. Given they need to move at least 500m to get the prize, too high-risk.

As far as I can tell nobody has done a successful re-entry with an inflatable at any scale, so quite possibly not; and certainly not without an awful lot of development funding.

It's an accounting thing; NASA mission cost caps don't include the LV but do include instruments, so they get the high-energy vehicle with minimum instrumentation, whereas ESA cost caps don't include instruments (which are supplied separately by member states) so they get the heavily-instrumented orbiter.

There will always be payloads that are simply too big for small vehicles; for example, current NASA notional Mars landing plans need SLS to get a 10m fairing to fit the heat shield. Good look fitting one of those on Atlas, or even Vulcan.

Which is better for what?

Irrelevant. There is no way we can move billions of people off-planet, and even if we could there's plenty of uninhabited 'space' right here where they'd be better off.

Still no sign of SLV stacking in sat images, so probably no launch on the 10th. They could theoretically be working at night to avoid observation, but it's pretty unlikely.

By grabbing a bunch of gold and a bunch of slaves, making the people behind the expeditions very rich. When they ran out of gold and slaves, they imported slaves from elsewhere and started growing stuff like sugar and tobacco that couldn't grow in Europe, again making certain people very rich. You might notice there are no slaves, easily accessible gold, tobacco, or sugar on Mars. In fact, you might notice there are no resources of any kind on Mars that we can't just get easier here.

Because real space programs have had need of rockets capably of putting payloads reliably into orbit at relatively low frequency, they tend to use designs that focus on lowering infrastructure costs at the expense of per-unit costs; for example, a higher-impulse first stage engine may be more expensive, but results in a smaller first stage that is easier to test and ship. BDB designs go the other way, optimising per-unit costs at the expense of either needing infrastructure that can handle very large rockets or very high flight rates; the result looks good on paper, but depends on higher demand than we have now. Sea Dragon was designed for the 60s-70s manufacturing in space boom that never happened, Delta IV in it's original form and Aqarius were for a 90s GTO comsat boom that never happened, et.c. et.c.

How does sending some chump to die on Mars benefit all of us? Or any of us?

But you still have the same assumptions... without an actual prototype, and without looking at the economic assumptions in the plan, there's no reason to believe Sea Dragon achieves the same results at any scale. After all, Delta IV was designed to be the cheapest booster ever built, by people with a lot more experience than the ones behind Sea Dragon and working within the scales they knew: they just designed with the assumption that the boom in GTO comsat sales would allow 40 cores launched/year. Given the masses it is supposed to be built for, Sea Dragon is similarly built for a market that never happened, so we can't use those numbers without major casveats even if the engineering all somehow turns out to completely sound. Oh, and in case you were wondering, the problem with the Delta IV wasn't just the flight rate; the main engine failed to hit their design targets, despite those being set after the kind of sub-scale component testing Sea Dragon never got. This is rocket science, as the saying goes, and in rocket science you can't assume something will just work.

If we're just naming radioisotopes, surely Cf-252 would be much worse than any of those.

DMSO+cyanide solution, used to very quickly stop respiration in certain biology experiments, as DMSO helps cyanide ions to cross various biological membranes very quickly without damaging them. Problem is, that includes human skin...

Therefore Delta IV is the cheapest launcher on the planet, just like it was supposed to be at this stage of it's development. It uses a cheap, simple engine based on extensive hydrolox experience from shuttle, the performance figures show it can do the missions it's likely to do most (deliver GPS sats) without solid augmentation, it can corner the commercial market with augmentation to keep the flight rate up and thus the price down, it uses cheap aluminium isogrid to deliver better economics on the upper stage then centaur's balloon tanks; what could possibly go wrong?

Sorry, but Sea Dragon never even reached the component testing phase, and all the design details are notional. You can't give figures from something like that as infallible, especially when so much of it had never been done. For a start, we know from work done since then that scaling up single-chamber kerolox engines is much harder than they assumed.

Again, why are assuming a study from 1962 involving single-chamber engines that are still orders of magnitude beyond anything ever actually fired is producing credible figures? Am I right to assume this is 1962 dollars? If it is, even the studies own result is a figure worse than the cheapest modern rockets, like Zenit. In 1962. They'd just tested the F-1, and assumed scaling it up would work out just fine. Here in 2015, we know from component tests that it would not, and F-1 remains the largest engine ever fired.

You can't prove anything with numbers you've just pulled out of your arse, especially for something like sea dragon; it's full of 60s-era assumptions about big hydrolox engines that we know don't true today. You might remember people actually tried making a rocket with a relatively cheap hydrolox engine and poor mass fraction; it's called Delta IV. You might also remember it's one of the most expensive rockets available, because they fudged both the infrastructure and handling costs as well as demand, exactly like you're doing.

But you're not talking about a 100kg satellite and transfer stage, you're talking upwards of 25 tons satellite and transfer stage. You can only get good figures for loss mass fraction boosters for that if you ignore infrastructure and handling costs, which you are doing. EDIT: You're also ignoring that the largest portion of the cost of a booster is the engines. If you want to combine low-ISP engines with low mass-fraction everything else, the rocket equation is going to mess you up badly.

Almost all customers want a large payload placed in geostationary transfer orbit with a high level of reliability; how much you can place into LEO with your fictional low mass-fraction booster is irrelevant in this case, because trying to boost further to relatively high-energy orbits like GTO with a low mass-fraction stage is a fool's errand.

Kg are mass by definition. Weight is newtons