From a NASA tweet we can see the crew exiting, with a pair of quickdraws around their chest:

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Oddly, everyone seems to get a different model:

enter image description here

What are these used for?


1 Answer 1


It's always difficult to say exactly why SpaceX does things, as they are so secretive. However, the practice has historically been done in spacesuits to prevent ballooning when the suit is pressurized. In particular:

  1. Without such a restraint, the shoulders of the suit under pressure tend to spread apart laterally. This severely limits shoulder mobility; the astronauts cannot move their arms properly.

    The usual solution is a bar or strap across the chest, which limits lateral ballooning. Here is an experimental World War II flight suit with such a bar:

    Goodrich XH-1

    B. F. Goodrich developed the XH-1 suit, part of a series of increasingly better suits that were ultimately judged the best of the Word War II efforts. Bellows at the elbows and knees provided improved mobility. Note the metal rod stretching between the shoulder rings, an attempt to control side-wise ballooning. This would become a feature on most of the subsequent suits designed by Russell Colley.

    Dressing for Altitude: U.S. Aviation Pressure Suits—Wiley Post to Space Shuttle, p. 51

    Here you can see a strap across the Russian Sokol intravehicular spacesuit, also used for the nametag:

    Sokol suit

    And a similar white strap across the chest of the Mercury spacesuit:

    Mercury spacesuit

    The SpaceX quickdraws would be adequate for this purpose.

  2. Without a restraint, the fabric at the shoulders rises up, forcing the neck ring and helmet to also rise. The astronaut's mouth and nose are now down in the neck ring, with only the eyes and top of the head now visible in the helmet faceplate.

    The solution is a "helmet holddown" cable or webbing running from where the neck meets the shoulder, to the groin. In the Sokol suit (above), this is hidden inside the suit, and runs along the entry zippers. In the Mercury suit (also above), you can see silver cables in a V shape to the middle of the chest, where they meet a white strap that runs to the groin.

    The SpaceX quickdraws should help somewhat, although ideally they should attach at the neckring, not at the corners of the shoulders.

Apollo spacesuits had restraint cables that were hidden inside the suit.

American (EMU) and Russian (Orlan) EVA suits used with the Shuttle and ISS have a hard upper torso, which is rigid enough to prevent ballooning.

Gemini and the intravehicular Shuttle suits (ejection seat suit, LES, ACES) use an ingenious layer of nylon mesh called Link-Net to prevent ballooning:

The restraint layer featured a major break-through with the use of a new “distorted-angle fabric” called Link-Net, which was used to control ballooning and enhance range of motion. This eliminated the need for the tomato-worm bellows at the limb joints used by ILC and most of the World War II suits. Link-Net is a series of parallel cords that loop each other at frequent intervals. The loops are interlocked but not connected so that the cords can slide over each other and feed from one section of the suit to another. [...] The enormous advantages offered by the Link-Net fabric were initially hard to fully grasp. The fabric allowed David Clark Company to design a suit that provided reasonable mobility without resorting to complicated mechanical or metal joints, saving considerable weight and providing much better comfort.

Dressing for Altitude, pp. 248-251


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    $\begingroup$ I don't think that's an answer to the question... The type of strap you describe would be needed in space (e.g. also on the trip up), but not after landing. $\endgroup$
    – asdfex
    Commented May 4, 2021 at 10:48
  • 1
    $\begingroup$ @asdfex: Nonsense. The strap stays on through recovery, even if it is not technically "needed", until the suit is finally taken off. You can see this in pictures of recovered Mercury and Soyuz crew; they are still wearing the strap. Indeed, it is hard to find a picture of these suits being worn without the strap. $\endgroup$
    – DrSheldon
    Commented May 4, 2021 at 13:16
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    $\begingroup$ If this is "Nonsense" - why aren't the Crew-1 straps worn during launch, docking, return and splashdown? $\endgroup$
    – asdfex
    Commented May 4, 2021 at 15:01
  • $\begingroup$ I too think it's not because of a sausage effect (they are cut pretty tight) but to enable the astronaut to quickly access those straps single handed, to secure themselves either at their hip or at their shoulders and switch fixing in weightlessness. Those suits of today are different from the ones of the '60s, in both function and material. $\endgroup$
    – user40414
    Commented May 4, 2021 at 15:01
  • $\begingroup$ @Earthworm: The Sokol and ACES suits I describe above are the latest suits, not "suits of the 60s". $\endgroup$
    – DrSheldon
    Commented May 6, 2021 at 12:03

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