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According to Wikipedia's regularly updated Polaris Dawn: Events:

Since the Crew Dragon lacks an airlock, the entire capsule was depressurized during the EVA, exposing all crew members to the vacuum of space, though only two partially exited the spacecraft. Depressurization of the capsule took about 30 minutes. Isaacman went first, spending seven minutes and 56 seconds outside. Gillis went next, spending seven minutes and 15 seconds outside. From hatch open to hatch close the EVA took about 26 minutes and 40 seconds. During the EVA, Isaacman and Gillis performed several tests of their suit mobility including trials of hand/body control, vertical movement, and using a foot restraint, only their lower legs were still inside the spacecraft.

Question: Does this really count as a space walk - an EVA proper - if their feet were always kept inside the capsule?

Can one simply stick a (suited, pressurized) finger through a hole and call it an EVA?

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    $\begingroup$ You have two questions in your title, and one in body. $\endgroup$
    – Russell Borogove
    Commented Sep 14 at 5:23
  • $\begingroup$ @RussellBorogove fixed that, I'll split it off separately. Since you've already posted an answer, can you double check that the edit hasn't caused a mismatch? Thanks! Asked just now: Why did the Polaris Dawn EVAers keep their feet inside the capsule? Were they not tethered? $\endgroup$
    – uhoh
    Commented Sep 14 at 6:13
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    $\begingroup$ For spacewalks on ISS, EVAs officially begin when the astronauts are still in the airlock with the hatch closed, after the lock has been depressurized. In fact the official EVA time begins at the moment when the astronauts switch their suits to internal power. The EVA officially ends when the astronauts are back in the airlock with the hatch closed and repressurization begins. $\endgroup$
    – Steve Pemberton
    Commented Sep 14 at 10:22
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    $\begingroup$ I read the question intent as looking for a strict definition of an EVA, or to define types of EVA even though that wasn’t specifically asked. A standup EVA is defined as when an astronaut partially exits the vehicle, normally heads first thus the metaphor in the name, to perform some function that does not require a full exit such as photography or assisting an astronaut who is outside the vehicle. Hypothetically there could be a need to hand something to an outside astronaut, and only some fingers exit the vehicle. Would that be considered a standup EVA? My guess is no it would still be IVA. $\endgroup$
    – Steve Pemberton
    Commented Sep 15 at 0:13
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    $\begingroup$ I guess it all means that at least for the foreseeable future we have to accept that the term Extra Vehicular does not necessarily mean being outside of the vehicle (since some astronauts during EVA remain inside the vehicle), and that a standup EVA does not mean that the astronaut is standing up (since in most cases they can't) nor in most cases are they walking in space (since in most cases they can't). But other than rankling our sensibilities, I guess there is no actual problem that any of this is creating. $\endgroup$
    – Steve Pemberton
    Commented Sep 26 at 1:22

3 Answers 3

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Who do you consider an authority on the definition of EVA?

NASA performed so-called "stand-up EVAs" - head outside the craft, feet inside - during the Gemini program (e.g. Gemini 10, Gemini 12) and on Apollo 15. Note that when stand-up and other EVAs are done on the same mission, they're referred to all in a single numbering sequence as EVA-1, EVA-2... without distinction. For the broad-scale mission plan, stand-up and other EVAs involve the same major steps and concerns; you have to suit up the crew, depressurize, open the hatch, etc., so they're treated similarly.

Your question seems to assume that "space walk" and "EVA" are synonymous; I wouldn't call a stand-up EVA a space walk.

If there was some sort of Activity that you cared to perform with just your suited finger on the Ext[erior] of your Vehicle, I suppose I would have to regard that as Extra-Vehicular Activity.

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This is mainly a matter of definitions.

For example, Jonathan McDowell uses this definition for his list of spacewalks:

[A]n activity carried out in vacuum conditions protected at most by a (not rigourously defined) spacesuit.

He explicitly acknowledges that …

My definition means that I include what NASA calls `intravehicular activity', where astronauts work inside a depressurized section of a spacecraft. My view is that a spacewalk can be either when you go outside the spaceship to enter space, or equally well when you let space into the spaceship.

According to this definition, and Jonathan McDowell's list of spacewalks, all four Polaris Dawn crew members performed a spacewalk of about 32 minutes measured from depress to repress or 26 minutes measure from hatch open to hatch close.

As Jonathan McDowell points out, the definitions are arbitrary and may become blurry. We generally consider an EVA to mean that the astronaut leaves the spacecraft. But, they only do this while still being in another spacecraft. We just call that spacecraft a "suit". Compare, for example, an EMU suit with the PLSS pack and the MMU with a Vostok capsule … can you really find some hard definition that makes one a spacecraft and the other not?

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  • $\begingroup$ By that definition, moon walks are also space walks. $\endgroup$
    – Barmar
    Commented Sep 14 at 18:18
  • $\begingroup$ @Barmar and they are on McDowell's list (as "LEVA"). So he's consistent, at least :) $\endgroup$
    – hobbs
    Commented Sep 14 at 20:04
  • $\begingroup$ McDowell has a propensity for idionsyncratic definitions. $\endgroup$
    – Russell Borogove
    Commented Sep 15 at 3:42
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    $\begingroup$ @RussellBorogove: But so do others. For example, according to NASA's own definition, where an EVA starts when the suit transitions to internal power, none of the Gemini or Vokshod "EVAs" were EVAs. In fact, according to NASA's definition, this iconic photo of Ed White floating free above the Earth, which NASA itself titles "Ed White: First American Spacewalker" is not, in fact, a photo of a spacewalk but an IVA, which also means Ed White was not the first American spacewalker. $\endgroup$
    – Jörg W Mittag
    Commented Sep 15 at 6:56
  • $\begingroup$ Maybe this was a TEVA (thorax EVA)?? $\endgroup$
    – Peter - Reinstate Monica
    Commented Sep 15 at 8:13
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Yes, it counts.

If you're in a space environment in a pressure suit and the pressure drops - you're officially "EVA". You don't have to leave the airlock.

Man-Space Integration Standards Volume I, section 14 EXTRAVEHICULAR ACTIVITY (EVA) defines an EVA as follows:

EVA is any activity performed by a pressure-suited crewmember in unpressurized or space environments. EVA begins with depressurization of the airlock or space module, and ends with repressurization of the space module or airlock after crewmember ingress. This includes any internal activities where a pressure-suited crewmember may be operating in normal modes of operation (e.g., airlocks, passageways, unpressurized work areas, donning/doffing areas) and abnormal modes of operation (e.g., unpressurized modules).

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    $\begingroup$ Great reference! $\endgroup$
    – Organic Marble
    Commented Sep 25 at 17:51
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    $\begingroup$ Interestingly I couldn't find anything in the standards about umbilicals, even though it goes into great detail about everything else. The assumption seems to be that all astronauts will only use PLSS or SOP (secondary oxygen pack) both of which are mentioned. Makes sense if geared towards Shuttle and ISS, but the title page indicates that it is not limited in scope "This document is intended for use by design engineers, systems engineers, maintainability engineers, operations analysts, human factors specialists, and others engaged in the definition and development of manned space programs." $\endgroup$
    – Steve Pemberton
    Commented Sep 25 at 23:40
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    $\begingroup$ @OrganicMarble - per the text I quoted I thought it's not limited to NASA, but maybe that is implied since it is a NASA document. The use case so far has been capsules which typically don't have room to stow a PLSS. Dave Scott used a long umbilical on Apollo 9 for his standup EVA. Long umbilicals were used for the Apollo deep space EVAs. And Dave Scott used one in the LM during his standup EVA through the docking hatch on the lunar surface. Dragon will possibly always require them. Maybe Orion? On larger vehicles it could in theory enable a crew member to assist in the airlock while in vacuum. $\endgroup$
    – Steve Pemberton
    Commented Sep 26 at 15:17
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    $\begingroup$ Umbilicals also take up stowage space of course, I wonder how much space a coiled up Apollo unbilical/tether took up compared to a PLSS? $\endgroup$
    – Steve Pemberton
    Commented Sep 26 at 15:20
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    $\begingroup$ @StevePemberton IIRC it's a lot of work for EVA crew to drag them around too. (They use them in the NBL, but have divers hovering around to move them). $\endgroup$
    – Organic Marble
    Commented Sep 26 at 15:43

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