Orion is designed to support only one EVA. There's no airlock so the entire spacecraft would be evacuated of air during the space walk and then repressurized from gas flasks, with a storage enough for doing it only once. This might be sufficient for current ambitions for HSF, but could it be upgraded to do several EVA's? And what about Dragon v2 and CST-100, are they designed for any EVA capability?

I imagine that the service module could be extended to allow for gas storage for multiple pressurizing events. But couldn't one also attach an inflatable airlock so that the entire spacecraft does not have to be evacuated of air? That's actually how the first space walk ever was done, by Alexey Leonov in 1964 as illustrated below. Today maybe a suitport would be a better idea because Alexey had quite some problems getting back into that rubber bag. (Maybe a couple of suitports should be put on the ISS just because it's simpler than airlocks?)

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Orion was designed to be able to support travel beyond LEO but instead of trying to add everything asked for to the base module (think space shuttle) they kept the capsule itself small and focused [1]. Instead of adding features to the capsule there are multiple proposals to dock with an additional module in space to extend capability:

Proposed Androgynous Docking Airlock/Utility Module (2009)

This proposal suggests using a commercial launch provider to launch an inflatable module into orbit that Orion would dock with to provide an airlock, storage space for tools/suits, and some equipment to enhance the life support system.

Cygnus Beyond Low-Earth Orbit – Logistics and Habitation in Cis-Lunar Space (2014, page 12)

While I found this referenced as a NASA presentation, this appears to be an Orbital proposal to extend their Cygnus craft to provide living space, logistics for extended missions, and a few options including a toilet and an airlock. The idea would be to launch a Cygnus-based craft designed for Orion support, dock it and Orion together in orbit, then go do the mission with the two modules connected. One news article reporting on the presentation (to which I've lost the link) suggested Cygnus could be left in orbit for re-use, though I'm not seeing that mentioned in the presentation slides.

  • $\begingroup$ Even Cygnus!? That makes me wonder if ESA is about to develop a crewed spacecraft too, since they have launched the heavy ATV and now develop the service module for the Orion. They seem to get some pieces of the puzzle together. $\endgroup$
    – LocalFluff
    Commented Jul 25, 2015 at 12:54
  • $\begingroup$ @LocalFluff The ESA did have plans for an ATV-derived crew capsule, but they were canceled due to budget constraints. $\endgroup$
    – Philipp
    Commented Jul 26, 2015 at 21:42

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