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GordonD

What is an EVA?

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The Americans and Russians have different definitions on what constitutes an EVA. For the Americans, an astronaut must have at least his head outside the spacecraft to qualify: for instance, when the J-series Apollo flights were returning from the Moon, the CMP would carry out an EVA to retrieve the film cassettes from the Service Module's SIMBAY, while the LMP assisted. Because the LMP had his head and upper torso out of the Command Module hatch, he was credited with a Stand-up EVA (or SEVA), while the mission Commander was not, even though he was suited up and in vacuum, because he remained inside the spacecraft at all times.

 

In contrast the Russians class an EVA as any time a cosmonaut is in vacuum in a space-suit, even if they do not venture outside the spacecraft: for example, after the Progress M-34 freighter collided with Mir in 1997, Anatoli Solovyov and Pavel Vinogradov carried out an inspection of the damaged Spektr module from the inside. This was classed as an Intra-Vehicular Activity or IVA. 

 

The reason for this is because the Russians have always used an airlock of some sort, meaning that cosmonauts not actively involved in the EVA remained under normal pressure, whereas on Gemini and Apollo missions the entire spacecraft was depressurised, but it was still felt desirable that a distinction be made between those performing the EVA and those not taking part.

 

The sources I'm using for the EVA anniversary reports follow the Russian definition for that country's EVAs and the US one for theirs, and I'm doing the same here.

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Interesting little space tidbit i was not aware of! :) 


With China becoming more and more involved in the space scene, any idea what they classify as an EVA? im sure we are supposed to see one of their larger station modules go up into orbit this year. 

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7 hours ago, Kushan_Farsight said:

Interesting little space tidbit i was not aware of! :) 


With China becoming more and more involved in the space scene, any idea what they classify as an EVA? im sure we are supposed to see one of their larger station modules go up into orbit this year. 

Good point. I don't think the question has arisen yet as they haven't carried out any IVAs, so presumably they take the same line as the Americans.

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