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Author
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Topic: Intra- vs. extra-vehicular (IVA/EVA) activities
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SPACEFACTS
Member Posts: 311
From: Germany
Registered: Aug 2006
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posted 04-27-2017 06:15 AM
   
Is an intravehicular activity (IVA) a full extravehicular activity (EVA)? Rob Navias of Johnson Space Center wrote me this definition: EVA is counted as anything in which a crewmember is in a suit in vacuum whether inside structure or outside structure. If this is correct, the Apollo 11 astronauts made two EVAs: the lunar excursion and a 2-minute EVA to discard equipment (they just opened the hatch). |
Headshot
Member Posts: 891
From: Vancouver, WA, USA
Registered: Feb 2012
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posted 04-27-2017 07:01 AM
I believe the two are separate activities.While both involve a crewmember exposed to the vacuum of space, during an EVA the crewmember is also exposed to: (1) the harsh output of the sun, (2) high velocity grains of dust and space debris, (3) and the extreme cold encountered during night-side operations. |
Mike Dixon
Member Posts: 1428
From: Kew, Victoria, Australia
Registered: May 2003
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posted 04-27-2017 07:03 AM
That'll cause some thought and debate. So McDivitt should be credited with an EVA? |
Robert Pearlman
Editor Posts: 43576
From: Houston, TX
Registered: Nov 1999
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posted 04-27-2017 09:17 AM
quote:
Originally posted by SPACEFACTS:
Rob Navias of Johnson Space Center wrote me this definition...
Were you specific in your query that you were referring to a historical definition? His reply may be based on current space station practices. The NASA EVA Chronology "Walking to Olympus" (Portree, Trevino) explains: Russia and the U.S. define EVA differently. Russian cosmonauts are said to perform EVA any time they are in vacuum in a space suit. A U.S. astronaut must have at least his head outside his spacecraft before he is said to perform an EVA. The difference is based in differing spacecraft design philosophies. Russian and Soviet spacecraft have always had a specialized airlock through which the EVA cosmonaut egressed, leaving the main habitable volume of the spacecraft pressurized. The U.S. Gemini and Apollo vehicles, on the other hand, depressurized their entire habitable volume for egress. I believe the U.S. approach has changed in the space station era, as U.S. EVAs begin when the EMUs are taken to battery power, not when the hatch is opened or when the astronaut egresses. |
LM-12
Member Posts: 3324
From: Ontario, Canada
Registered: Oct 2010
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posted 04-27-2017 11:15 AM
As I mentioned in this thread, the two standup EVAs by Dave Scott (on Apollo 9 and Apollo 15) are counted in the "Apollo Program Summary Report" EVA tables, but the three similar standup EVAs by Jim Irwin, Charlie Duke and Jack Schmitt during the J-mission transearth coasts are not counted in those tables. There seems to be an inconsistency there.In the transcripts, Gene Cernan and Jack Schmitt referred to the LM equipment jettison as an EVA. When Skylab 2 had problems docking with the station, the crew suited up and depressurized the command module to remove and inspect the docking probe. Pete Conrad referred to that as the second EVA. |
Blackarrow
Member Posts: 3160
From: Belfast, United Kingdom
Registered: Feb 2002
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posted 04-27-2017 04:28 PM
I can think of no logical reason why Dave Scott's stand-up EVAs on Apollos 9 and 15 would be credited as EVAs but the stand-up EVAs by Jim Irwin, Charlie Duke and Jack Schmitt would not be credited as EVAs. There is no difference. |
LM-12
Member Posts: 3324
From: Ontario, Canada
Registered: Oct 2010
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posted 04-27-2017 06:13 PM
The EVA summary on the spacefacts.de website includes all the LM equipment jettisons and gives Irwin, Duke and Schmitt SEVA credits for the transearth EVAs.
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SPACEFACTS
Member Posts: 311
From: Germany
Registered: Aug 2006
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posted 04-28-2017 12:58 AM
Correct. But should I add the IVA and SEVA times to the total EVA times? |
LM-12
Member Posts: 3324
From: Ontario, Canada
Registered: Oct 2010
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posted 04-28-2017 07:32 AM
Going by the EVA definition, the transearth SEVAs should definitely be included.The EVA table in NASA SP-149 "Summary of Gemini Extravehicular Activity" includes equipment jettison time in the total EVA time. If you have astronauts who performed IVAs calling them EVAs, then that's good enough for me. |
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