MinimumSky5

I think this is why RP-1 was developed, they needed primarily to get rid of the turpentines and aromatics in the fuel. I do know that petrol (gasoline) was dropped as a fuel early on, because it was much more difficult to get a nice, soot free burn than with kerosene. This may not be a factor anymore, though, as I'm talking about the era of Goddard here! The safety factors of petrol are very significant, as well. Spill kerosene on the ground, and even an ox-acetylene torch won't ignite it, as it needs to be aerosolised before ignition can occur.

There probably isn't enough downmass for NASA to justify using Dragon 2 for that, just yet.

Life is already present, in a highly diverse community, below floating ice shelves. This will cause a local mass extinction, not a sudden flowering of life.

Huh. I didn't realise that anyone had video capable surveillance satellites, I always thought that that was a Hollywood myth.

It's probably an inherited trait. We've been using fire for millions of years and evolved in an area known for major wildfires, so it would seem logical that we would associate burning people with bad things. The fact that we can differentiate between cooked antelope and cooked people is likely a unique trait to humans.

True, but you wouldn't build up in orbit until it becomes cheaper to build new land in the habitats, than simply building down here on earth.

Is that an unpressurized cargo bay on the side of HTV-7? If it is, what is it?

There will also be atmospheric drag, but unless you fly far too fast on ascent or have a very non-aerodynamic ticket design, this should be fairly small.

Short answer: Quantum Superposition Long answer: the photon is neither a wave or a particle, but exists as both at the same time until it is observed, at which point it collapses into one or the other, depending on the design of the experiment.

Also, while sterling engines are very efficient in terms of converting solar energy into electrical energy, solar panels are better in terms of power per kilogram

So, I've just read back along the thread, and I've somehow ended up arguing against my original point! I'm sorry for the frustration I caused, ill leave you all to continue discussing.

True, leave the car too long and it will have issues, same as anything, the point that I'm trying to make is the the systems in the Orion will not be taxed any more during a voyage to Mars than they would be during a voyage to low orbit. Maybe the car was a bad analogy, though in fairness my dad's work often left out of the country for weeks or months at a time, and we only ever had to turn the engine over a few times while he was away to keep the battery charged, tyres and oil were never a problem.

Vacuum conditions aren't that difficult to deal with, it just requires a good pressure vessel, and submarines have to deal with higher pressure differences routinely. The temperature would never change during the cruise phase of the mission, you only get those changes in low orbit as objects pass behind and in front of the earth. Radiation probably is the biggest issue, but we've characterized the radiation of interplanetary space quite well with so many probes being sent to other planets, and the electronics are the only vulnerable part of the spaceship. There is no natural place in the solar system that has radiation so high that you have to be worried about it causing structural damage. All of these problems have been solved in low orbit, so they shouldn't be a major concern when going to mars.

But the ship won't just fall apart after a few years of flight, because most of the systems will be offline to preserve them, in case the crew need a backup. If the ship was so poorly built that failure over that time line was likely, then NASA would never launch it even to low earth orbit. Cars are designed to be used almost daily, for commuting to work and back, but leave it sitting in your driveway for a month, and it will run just as well as if you'd used it the day before when you start it up. Space is basically the same, in low orbit, interplanetary space, or Martian orbit, so sending the ship out on a solo mission to Mars won't teach us anything, aside from a spectacular way to waste a billion dollars.

Oh, you mean the Copernicus mission concept? Yes, they considered using Orion for that, but while docked to a much larger mothership that could support the Orions for that long. They never intended for the astronauts to be in just an Orion capsule for the entire journey back.

I thought that the first BFR crew varients to Mars were going to be unmanned, and used as permanent habitats?

You'd be surprised how heavy hydroponics systems are, and remember the weight of the power generating equipment to light and run the farm. (even at earth's distance to the sun, in space you need some supplemental lighting, because the colours in the light aren't the same as at the earth's surface.)

If I remember right, this has been done several times before, and it's always worked for them. I don't know how you could test a system to repair these holes on the ground, partly because creating a vacuum chamber big enough to test the modules would be very difficult, and partly because microgravity would greatly alter how you would conduct the repair.

If NASA used the propellant in the service module, then yes, it could probably reach a martian flyby safely, but the real question is why would they do this? Orion was never designed to do this, and can't comfortably take astronauts that far for that long. SpaceX sent the car there as a pure PR stunt, because they got a heck of a lot more coverage than if they'd just used a big block of concrete as a mass simulator.

Because, even with advanced fusion drives, that is horribly energy wasteful. Also, what happens when one of those drives fails? Even if you've mastered fusion, a simple structural beam of any material will be a heck of a lot more reliable than any drive system.

Most English speakers will say "calories" when the mean "kilocalories", mostly because food packaging uses the term incorrectly.

You only need about a ton of food per person per year, so you need large crews or very long duration missions to warrant growing your own food.

Yeah, except that I just realised something rather important. The pressure vessel approach only works with a true ringworld, as it relies on the gravity of the central star to generate the pressure holding the counterweight against the habitat, which a banks orbital (basically what was suggested) by definition would not have. There is a reason that earthlike banks orbitals are 3 million miles across!

It would defiantly need the extra mass, the widest that a rotating cylinder habitat, at 1g, could be is roughly 1,800Km wide, and it would need to use graphene as its structural material (even carbon nanotubes can't cut it at this size).

Its a debate in astronomy, as to whether the north pole is the pole that points to the northern celestial hemisphere (relative to Earth) or if it's the pole that rotates anti-clockwise when viewed from above.