back to article Musk: I want to retrieve rockets with big Falcon party balloons

While waiting for TESS to get off the launchpad on Monday, chief exec Elon Musk joked on Twitter about how SpaceX might set about recovering the second stage of the booster. SpaceX will try to bring rocket upper stage back from orbital velocity using a giant party balloon — Elon Musk (@elonmusk) April 15, 2018 The idea is …

  1. Charlie Clark Silver badge
    Coat

    bouncy castle

    Isn't the Bouncy Castle by Trump™ the new name for the Whitehouse? To be inauguarated by Silvio Berlusconi…

    1. The Man Who Fell To Earth Silver badge
      FAIL

      Bouncy House

      Actually, NASA did land on Mars using a bouncy house with the landing of Mars Pathfinder. I worked at JPL at the time. Mars Pathfinder carried the bouncy house with it.

      Mars Pathfinder Bouncy House

      1. Cheesemouse

        Re: Bouncy House

        Would the astronauts have to take their shoes of before using it though? You have to think this stuff through.

        1. Charlie Clark Silver badge

          Re: Bouncy House

          Would the astronauts have to take their shoes of before using it though?

          hm, good question. I wonder if someone has told Stormy Daniels or Ruby?

  2. Anonymous Coward
    Anonymous Coward

    Explains why LOHAN has never happened ... you're doing the rocket/baloon thing the wrong way round!

    1. hplasm Silver badge
      Happy

      "Explains why LOHAN has never happened ... "

      "...you're doing the rocket/baloon thing the wrong way round!"

      Ballockets! I say!

      1. maffski

        Re: "Ballockets! I say!"

        I prefer a Rocloon myself, but they do keep going through the garbage.

  3. Voland's right hand Silver badge

    Errr.. Why?

    If it is any form of baloooooony tech it will most likely float just fine. So no need to do bouncy castles or other "on-land" attractions. Just do some splashing along the water a few times.

    It is also a second stage so it can actually be made to deorbit nearly anywhere around the world. In fact, it may be better to make it deorbit somewhere away from civilization. Just in case.

    1. Duncan Macdonald Silver badge
      Mushroom

      Re: Errr.. Why?

      In which case the White House is the perfect landing zone (especially if there is still a few tons of propellant left)!!

      1. Mark 85 Silver badge

        Re: Errr.. Why?

        In which case the White House is the perfect landing zone (especially if there is still a few tons of propellant left)!!

        The White House? Excellent choice as there's been no intelligent life there for several decades.

    2. Alistair Silver badge
      Windows

      Re: Errr.. Why?

      @ Voland:

      To get rid of snarky comments from commentards at The Register about littering up outer space.

      I'll happily deorbit the second stage anywhere around the world, so long as I can choose the targets randomly, in anger, about 30 seconds before I execute the deorbit command.

      /wow -- apparently channelling a political entity today.

  4. Anonymous Coward
    Anonymous Coward

    Anchor an elastic band in space, attach to rocket and start descent then once speed has been sufficiently reduced release the band and land gracefully. I see no problem with this and you can already get the bands from ACME.

    1. psychonaut

      this is genius.

      the best bit about it, is if you got the tension correct, the rocket could come to a complete stop (for some value of a small amount of time) next to a platform which could allow people to alight / derocket, and then go up to orbit themselves using nothing other than the tension in the ACME. rinse and repeat, with a few chemical kickers along the way to defeat that pesky friction stuff. you wouldn't want to hang about though i suspect when de-rocketing alighting.

      1. AdamT

        In theory it doesn't even need to be elastic, just spinning:

        https://en.wikipedia.org/wiki/Skyhook_(structure)

        I think getting the timing of everything just right is fairly critical.

        I recall Neal Stephenson used these in his SevenEves novel.

  5. Aladdin Sane Silver badge

    Old news

    They did it in 2010.

    1. ravenviz Silver badge

      Re: Old news

      Please see comment re standing on the shoulders of giants.

  6. Ugotta B. Kiddingme

    The most interesting use case

    that unfortunately never panned out was the Rogallo Wing planned for the Gemini crew capsules. While not technically a balloon (or at least not ALL of it), the Rogallo Wing concept was a great example of out-of-box thinking for spacecraft recovery.

    1. Neil Barnes Silver badge

      Re: The most interesting use case

      But now Rogallo wings are used by some paraglider fliers as emergency parachutes. Apparently they're a real pain to pack properly (I use a centre-pull round parachute; I can pack that myself).

      1. Gene Cash Silver badge

        Re: The most interesting use case

        They're used by Kerbals in the latest release of KSP too!

  7. phuzz Silver badge

    Amatures too

    It's not just big serious rocket companies using ballutes, Copenhagen Suborbitals are planning to use one to stabilise their capsule, in fact, they posted a video of the first test (ie, throwing it off a big building) just yesterday:

    https://www.youtube.com/watch?v=UaGyD7gKAaw

  8. Scroticus Canis Silver badge
    Boffin

    "100 per cent oxygen at 16 psi " would kill you fairly fast.

    NASA used pure oxygen but at 21% atmospheric pressure so it was at the same partial pressure as in air, not at 107% atmospheric.

    Still burns every thing at a higher rate and temperature as they found out when three astronauts were cooked in their capsule some time back. The very reason that the Russians chose to use just plain air at 1 Atm and take the weight/space penalty.

    1. Chairman of the Bored Silver badge

      Re: "100 per cent oxygen at 16 psi " would kill you fairly fast.

      @SC- quite correct. On orbit, one maintains O2 at a cabin pressure equal to the partial pressure of O2 at sea level, about 5.1psi. I guess - but don't know - that having to design for a lower static pressure makes the spacecraft lighter? Wonder what they had to do with Apollo spacecraft to move to a mixed gas system after the Apollo 1 disaster (what an awful way to die)

      Found an interesting systems description link:

      http://www.astronautix.com/g/geminitechnaldescription.html

      Looks like internal pressure at launch was about atmospheric and the astonauts would be provided pure O2. Doesn't say whether the cabin was purged to eliminate the N2 but it's probably a reasonable assumption that it was. As the rocket lifts off the cabin is allowed to depressurize to 5.1psi or so, which happens around 20-40sec after launch. Atmosphere inside is definitely pure O2 at that point. On reenty the astronauts have to repressurize with external air during descent.

      So the 'nauts are probably breathing pure O2 at full atmospheric pressure, at least while waiting for launch. Imagine that with countdown holds that might be quite a while. Wonder how close the men got to physiological limits...

      1. Anonymous Coward
        Anonymous Coward

        Re: "100 per cent oxygen at 16 psi " would kill you fairly fast.

        @Chairman of the Bored "So the 'nauts are probably breathing pure O2 at full atmospheric pressure, at least while waiting for launch."

        It seems that while waiting for launch, the astronauts were breathing a gas mix with a sensible partial pressure of oxygen, supplied by their suits. I've just read on Wikipedia that oxygen toxicity can turn up in minutes when breathing an oxygen partial pressure above 0.3 bar.

        From:

        http://www.geminiguide.com/Systems/environmental.html

        "The pilots are provided with redundant atmospheres by having a closed pressure suit circuit within the pressurized cabin."

        as part of the pre-launch procedure:

        "A ground supply of pure oxygen is connected to the pressure suit circuit purge fitting. Flow is Initiated with the face plates closed. The suit circuit gas is sampled periodically until an acceptable oxygen content is attained."

        - the only gas mentioned as being supplied by spacecraft systems is oxygen, but then again nitrogen gas isn't consumed by human metabolism.

        There is also this, which applies to spacecraft descent:

        "The pressure in the suit and cabin remains constant at 5 psia (nominal) until an altitude of approximately 27,000 feet is reached.

        As ambient pressure increases during descent, the cabin pressure relief valve admits ambient air into the cabin, preventing high differential pressures. The cabin pressure relief valve begins to open when the ambient pressure is 15.0 inches of water greater than cabin pressure and opens to maximum flow when the pressure differential is 20 inches of water.

        At an altitude of 25,600 feet, or below, the pilots manually open the cabin inflow and outflow valves to circulate external air through the cabin and suit circuit.

        Maximum negative pressure on the cabin should not exceed 2 psi as controlled by the cabin relief valve."

        I found reading the page l linked to hurt my head a bit. Cabin pressure is specified in psia and tank pressures in psig; that's okay (a=absolute; g=gauge). Then you read the suits apparently maintain internal pressure between 2.5 to 3.5 inches of water below to 2 to 9 inches of water above cabin pressure. Cabin gas leakage is measured in "standard cubic centimetres". Oxygen supply quantities are specified in pounds and the gas supplied is sent through a 10-micron filter. A tracer chemical for urine analysis is specified in millilitres. I can see how it all made perfectly good sense at the time, but still my mind boggles.

        1. Chairman of the Bored Silver badge

          Re: "100 per cent oxygen at 16 psi " would kill you fairly fast.

          @AC, thanks for that detailed post and great link. This really does boggle the mind. As a hardware engineer I tend to think I'm really hot stuff, but looking at what was accomplished in the early space program reminds me that (1) my ignorance is vastly larger than my knowledge, and (2) we truly do stand on the shoulders of giants. Thanks!

  9. John Smith 19 Gold badge
    Go

    Entertaining but not actually correct.

    HIAD increases the size of the nose of the vehicle, and it's for a vehicle, not a stage.

    But bringing a US back from orbit is (in energy terms per Kg) 20x harder than recovering a booster. Most TSTO rockets split the velocity each stage provides 50/50. F9 splits it more like 1/3:2/3.

    Musks plan is putting a big ass inflatable at the back to keep the light end facing forward, rather than the engine end, which naturally wants to lead.

    Does not sound that different, but is.

  10. MT Field
    Windows

    Gissajob

    I like the way that Musk now talks about houses when in fact he means castles. Pretty soon he will be talking about houses when he means hollowed-out volcanoes.

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