8 thoughts on “Densifying Hydrogen”

  1. They mention densified O2 without explicitly mentioning SpaceX. Is anybody else doing that? For H, how do they remove heat in the vacuum of space? SpaceX says the pad explosion was because the O2 became solid, but I suppose H wouldn’t have that same problem?

    1. Well if you had in space propellant depots you have several ways of keeping the cryogenic propellant cooled down. You can vent off some propellant, which can be quite expensive, you can insulate the tanks, you can have radiators, and I’ve also read about heat pumps, namely Stirling engines, to keep liquids near zero temperatures in vacuum. I suppose they use some cooling fluid and a radiator. You should be able to read about that more in depth in the ULA ACES propellant depot proposal ULA did some years back, before the Senate decided on the SLS architecture. It’s not like the ULA partners weren’t interested in alternatives to SLS but the politicians never even gave it a chance.

      1. ‘zilla, designing radiators that provide enough performance without any consumables may be quite a challenge. Of course, just keeping it shaded may keep it cold. I think you wouldn’t need insulation because vacuum is an insulator. Space doesn’t seem to like the middle ground. Heat pumps just draw the heat to your radiator. You probably would not need those if the radiator were part of the holding tank.

        Bottom line, we shouldn’t need to guess. This should have been implemented a long time ago for a lot less cost than the stupidity of the SLS.

    2. Solid oxygen by itself wouldn’t have been much of a problem. From what they’ve said, the problem was that it solidified inside the composite wrapping of the helium tanks, and cut through the fibres, leading to a helium tank explosion. If they hadn’t been inside the oxygen tanks, that wouldn’t have been an issue.

      It does seem they’ve been seduced a little too much by the quest for efficiency, and ended up with a less reliable design as a result.

  2. The Slush LH2 could also be useful for a SSTO if anyone ever wants to try building one again. It was proposed to be used in SSTOs since at least the 1960s.
    I know the Russians, actually the Soviets, used chilled Kerosene in one of the versions of the Soyuz, I think it was in the Soyuz-U, together with Sintin. I wonder if SpaceX, or NASA for that matter, would be in having US Sintin production. AFAIK even Russia can’t produce the stuff anymore but its probably a matter of adjusting a refinery to produce the stuff with the proper fraction. I don’t remember if they also used chilled LOX in the Soyuz but I wouldn’t be surprised at all if they did.

    1. No need to reach back to old Soviet practice: SpaceX now uses densified lox and RP-1.

      Syntin is a complex molecule. It’s not something that’s just going to pop out of a refinery if you crack crude just right. It’s expensive to produce, and that’s why the Russians stopped using it. With SpaceX hoping to get costs down to the point where the cost of fuel matters and also hoping to produce fuel on Mars, I don’t see SpaceX being interested in syntin.

    2. The Soviets supposedly used slush Hydrogen in the Enegria/Buran launcher.

      I supposed they had plenty O’ helium due to the lack of all non-party party balloons.

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