- Joined
- Feb 1, 2009
- Messages
- 43,015
- Reaction score
- 10,523
The stoichiometric ratio of CH4 to O2 is 1 to 2 as far as mole ratio goes. That translates into a 3.6 to one mass ratio. If they can keep it shaded the oxygen would be fairly cold. The shaded side of the space station is around -250 F which is close to the -300F needed for liquid oxygen. Having it under pressure could keep it liquid. The liquid oxygen vacuum insulated cylinders used for flame cutting steel hold up to 350 psi and they can keep oxygen liquid for a couple of weeks. Turning a Starship into a thermos bottle with an inner layer of a tank so they could have a vacuum between the outer hull and the inner tank would add a lot of weight.yes i watched Scott Manleys video as well about yesterday lunchtime. Good vid, and he did a fast edit!
Yeah you can see at one point in the footage that the base of Starship was absolutely taking the brunt of the red plasma. And not designed for that. So they lost attitude control. I am pretty confident they knew by then WHY it lost attitude control -- the Reaction Control Thrusters weren't doing well enough to hold the ship in a heat-shield-to-windward attitude. So all was more or less doomed at that point.
you're right Starship needs to be refueled in Earth orbit before heading off to the moon. So several OTHER Starships ( "tankers") will need to be already in orbit and then they meet up and do a propellant transfer. Methane and Oxygen but mostly Oxygen, as i understand it. Not quite sure how they avoid massive amounts of lost liquid oxygen through boil-off. I guess by orienting the Starship tanker in orbit so it always has the TPS (tiles) facing the sun, and having massive insulation inside the tanker (bit like an RTIC drinking mug - a vacuum between 2 layers of Stainless steel maybe). It's a big issue -- if the LOX boils off..... no use to anyone. Liquid oxygen has to be kept super-cold to be usable as a liquid oxidizer. So many different engineering problems to solve. Solving all these problems will take YEARS to achieve. Artemis III could easily be 5 to 10years away, or even more.
The fuel transfer they were trying yesterday was to move propellant from one on-board tank to another on-board tank. I think they did this by deliberately rotating Starship end over end to settle the liquids towards the ENDS of the ship and then it could be pumped. Cannot pump liquids if they're freely floating around in their tanks, mixed with some gas bubbles (probably nitrogen). They SAID that worked, but they need to review the data.
it was good progress from SpaceX but this whole in-orbit refuelling has never been done between TWO separate craft, and it's very ambitious. But it needs to work as all their lunar and Mars trips need the Starship craft to get to Earth orbit and then be refuelled in orbit (most of the volume will be O2, not so much CH4).
Yes, they would have to have some type of inertia to be able to pump liquid in zero gravity. Technically there would still be gravity in orbit but the spacecraft is also falling toward the Earth, negating that. The could spin the ship to create artificial gravity but that would require a rotary connection unless they spin both vessels at the same rate. Would the liquid oxygen spin with the ship or would inertia leave the ship spinning around the liquid oxygen inside it?