Topic: Spacewalkers on untethered Earth orbit EVAs
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 09-19-2023 08:12 AM
How many astronauts have made untethered spacewalks in Earth orbit?
Axman Member
Posts: 497 From: Derbyshire UK Registered: Mar 2023
posted 09-19-2023 09:21 AM
I believe it's seven — although I cannot quote sources.
I know for definite the first was by Bruce McCandless from the shuttle on 7th February 1984, and the second by crewmate Robert Stewart.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 09-19-2023 09:35 AM
Mark Lee did one wearing a SAFER on STS-64.
Axman Member
Posts: 497 From: Derbyshire UK Registered: Mar 2023
posted 09-19-2023 09:47 AM
I think that was the last one (?). All the others I believe were using the Manned Manoeuvring Unit backpack.
brianjbradley Member
Posts: 177 From: Toronto, Ontario, Canada Registered: Dec 2010
posted 09-19-2023 10:34 AM
Jerry Ross and Jim Newman on STS-88 and Pete Wisoff and Michael Lopez-Alegria on STS-92 conducted SAFER tests but were tethered, so I think Lee and Carl Meade on STS-64 were the last untethered.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 09-19-2023 12:59 PM
Scott Parazynski and Vladimir Titov on STS-86 also tested the SAFER. From the press kit:
The SAFER unit to be tested on STS-86 is the first flight production model. Parazynski and Titov will be wearing the devices, and, while remaining tethered and in a foot restraint, they will evaluate the deployment of the hand controller and the firing of the automatic attitude hold feature. Firing the automatic attitude hold feature while the astronauts are in a foot restraint will test the firing mechanisms in the device, such as the valves and gas thrusters. The astronauts will not perform any free-flight testing of the SAFER as was performed on STS-64.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 09-19-2023 11:24 PM
George Nelson on STS-41C rode the MMU out to the Solar Max satellite on EVA-1 and attempted (unsuccessfully) to dock with it.
Frame 37-1718 shows that James van Hoften also rode the MMU, most probably on EVA-2. That is MMU #3.
cosmos-walter Member
Posts: 842 From: Salzburg, Austria Registered: Jun 2003
posted 09-20-2023 04:39 AM
On 2/1/1990 Aleksandr Serebrov was the first Russian to test the Soviet MMU called Ikar.
Axman Member
Posts: 497 From: Derbyshire UK Registered: Mar 2023
posted 09-20-2023 06:42 AM
Ikar also called Icarus and SPK, nicknamed the flying armchair or the spacebike was tested by Serebrov whilst it was tethered. The flying armchair remained in Mir in the Kvant-2 module but was never used again.
After a few hours searching I think there were eight astronauts, and zero cosmonauts and taikonauts to have free space walked. This is the list:
Bruce McCandless STS-41-B MMU (EVA1+)
Bob Stewart STS-41-B MMU (EVA 1+)
Pinky Nelson STS-41-C MMU (EVA 1+)
Ox Van Hoften STS-41-C MMU (EVA 2)
Joe Allen STS-51-A MMU (EVA 1)
Dale Gardner STS-51-A MMU (EVA 2)
Mark Lee STS-64 SAFER (EVA 1)
Carl Meade STS-64 SAFER (EVA 1)
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 09-20-2023 07:57 AM
I have not found any other names to add to that list.
I think there was only one SAFER unit on the STS-64 EVA. When Lee and Meade went out the hatch, Lee was wearing a SAFER unit and Meade was not. So it appears that they used the same SAFER unit during the EVA.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 09-29-2023 12:01 PM
McCandless flew both MMU #2 and MMU #3, based on what I have seen. So did Stewart, apparently.
MMU #2: McCandless, Stewart, Nelson, Gardner
MMU #3: McCandless, Stewart, Van Hoften, Allen
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 09-29-2023 08:14 PM
There are some STS-84 photos of a Russian MMU stored at the end of the Kvant-2 module at the Mir space station.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 10-07-2023 09:12 AM
How was the SAFER controlled after STS-64?
Compare these two EVA images: the first photo shows Carl Meade on STS-64. The second photo shows Chris Cassidy on Expedition 63.
On STS-64, Lee and Meade used a Hand Controller Module (HCM) to test the SAFER unit. The HCM was attached to the EMU Display and Control Module on the front of their spacesuits.
After STS-64, you typically do not see the HCM on EVA astronauts (like Cassidy) wearing the SAFER. So how did those astronauts control the SAFER had they needed to use it?
Jim Behling Member
Posts: 1931 From: Cape Canaveral, FL Registered: Mar 2010
posted 10-07-2023 03:26 PM
quote:Originally posted by LM-12: So how did those astronauts control the SAFER had they needed to use it?
It is stowed on side of the backpack. The astronaut grabs it and uses both hands on the controller.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 10-09-2023 05:21 PM
Thanks for that response. Photos showing the HCM stowed are not easy to find, but it looks like the HCM is stowed under the SAFER in this STS-76 EVA photo.
star61 Member
Posts: 316 From: Bristol UK Registered: Jan 2005
posted 10-10-2023 11:34 AM
I remember reading somewhere that Georgy Grechko on Salyut 6 was floating free through an open hatch. I think it was Romanenko who grabbed him and pulled him to safety. This could be regarded as an untethered EVA!
Axman Member
Posts: 497 From: Derbyshire UK Registered: Mar 2023
posted 10-10-2023 12:09 PM
No, not really. Just as the stand up EVAs in the Gemini series weren't space walks either.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 10-10-2023 03:50 PM
quote:Originally posted by star61: I remember reading somewhere that Georgy Grechko on Salyut 6 was floating free through an open hatch.
"Walking to Olympus" has it the other way around:
For years Soviet spaceflight observers believed that mission Commander Romanenko, in his eagerness to look out the open hatch, nearly drifted free of the station, and that only quick action by Grechko prevented him from being lost in space. Grechko now denies categorically that his commander was ever in danger, and adds ruefully that "Yuri was very angry about the story." Romanenko says that the story had its start in a "bad joke" Grechko told which was misunderstood, and adds that, even though his short safety tether was not secured, his electricity/communications umbilical firmly fastened him to Salyut 6.
star61 Member
Posts: 316 From: Bristol UK Registered: Jan 2005
posted 10-10-2023 04:52 PM
Ha! Just shows how effective rumour mills can be. Thanks for the correction.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 10-11-2023 12:55 AM
The SAFER was tested by Jeff Wisoff and Michael Lopez-Alegria on the final EVA of STS-92. There is some interesting footage of them operating the SAFER (while tethered) starting at 13:25 in this video. Lopez-Alegria is seen using the HCM.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 02-04-2024 08:50 AM
NASA has this article about photographing the untethered spacewalks on STS-41B.
The photograph, taken by a fixed camera on McCandless’s helmet, captured Challenger in its entirety, which included the payload bay with the Shuttle Pallet Satellite and a glimpse of astronaut Robert Stewart standing just beneath the spacecraft’s RMS.
I see Stewart on the opposite (starboard) side of the payload bay near the stowed MMU.
Blackarrow Member
Posts: 3725 From: Belfast, United Kingdom Registered: Feb 2002
posted 02-05-2024 09:18 AM
Did any of the eight "spacewalkers" listed by Alan (Axman, above) complete a whole orbit of Earth untethered? And was/were the individuals recorded as independent satellites?
Axman Member
Posts: 497 From: Derbyshire UK Registered: Mar 2023
posted 02-05-2024 09:33 AM
Nice enquiry. I would love to know the answer to your second question.
As to the first: they definitely made at least one orbit because as Wikipedia reports "McCandless's first EVA lasted 6 hours and 17 minutes. The second EVA (in which Stewart used the MMU) lasted 5 hours and 55 minutes."
As an orbit is about 90 minutes, they both did about four orbits as independent satellites! Whether or not they acquired COSPAR numbers or not, I have no idea.
Edit: HOLD THE FRONT PAGE! Astronautix gives this info:
So yes, they (or at least the machine they were attached to) are credited as independent satellites...
Blackarrow Member
Posts: 3725 From: Belfast, United Kingdom Registered: Feb 2002
posted 02-05-2024 12:35 PM
I well remember watching live TV coverage of Bruce McCandless leaving the shuttle cargo bay and moving slowly out into the blackness. But I didn't think the untethered part of his EVA took him entirely around the globe (and I think I recall being mildly disappointed at the time that McCandless didn't complete a full untethered orbit).
A few obvious searches haven't revealed how long he (or the other untethered spacewalkers) were actually flying independently and outside the shuttle. The information must be there somewhere.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 02-05-2024 12:44 PM
Chapter 13 in NASA SP-4219 has this paragraph:
NASA carried two MMUs (serial numbers 002 and 003) aboard three Space Shuttle flights in 1984: 41-B in February, 41-C in April, and 51-A in November. Six astronauts - Bruce McCandless II, Robert L. Stewart, George D. Nelson, James D. van Hoften, Joseph P. Allen, and Dale A. Gardner - flew the MMU. These mission specialists flew the MMU on a total of nine sorties for a total of ten hours and 22 minutes. Each astronaut donned and doffed the maneuvering unit in the open cargo bay.
It mentions "nine sorties for a total of ten hours and 22 minutes" so that narrows down the MMU time a bit. I count eight sorties.
Blackarrow Member
Posts: 3725 From: Belfast, United Kingdom Registered: Feb 2002
posted 02-05-2024 03:58 PM
It still doesn't distinguish between "MMU time" and "untethered MMU time." Attached to the shuttle (as, for instance, McCandless was while checking out the MMU) or loitering within the cargo bay shouldn't count.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 02-06-2024 04:13 PM
According to this NASA article today on the 40th anniversary of STS-41B, there were five MMU sorties on the flight, if I read it right:
EVA #1: McCandless in MMU #3 Stewart in MMU #3
EVA #2: McCandless in MMU #2 Stewart in MMU #3 McCandless in MMU #3
However, photo STS-41B-21-854 seems to show Stewart in MMU #2.
Views of Astronaut Robert L. Stewart in Maned Maneuvering Unit (MMU) taken by the fixed camera in Bruce McCandless's helmet. Stewart dons the MMU in the starboard station. Stewart, wearing Trunnion Pin Aquisition Device (TPAD), practices docking with the trunnion pin on shuttle pallet satellite (SPAS) as the Main Electronics Box (MEB) of the Solar Maximum Mission (SMM) is also visible.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 02-06-2024 06:01 PM
The photo has a date taken of Feb. 7, 1984, so that would suggest EVA #1.
Jim Behling Member
Posts: 1931 From: Cape Canaveral, FL Registered: Mar 2010
posted 02-07-2024 12:01 PM
quote:Originally posted by Axman: "McCandless's first EVA lasted 6 hours and 17 minutes..."
Those are the durations of the whole EVA and not time on the MMU.
quote:COSPAR: 1984-011xx.
That is not a credible answer to the question.
It is an assumption by Astronautix that they were to be assigned a COSPAR number. The "XX" is not the actual number but placeholders. So, that does not indicate that they were credited as independent satellites.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 02-07-2024 04:54 PM
quote:Originally posted by Blackarrow: loitering within the cargo bay shouldn't count.
If you mean wearing the MMU and moving around within the payload bay, then I think that should count as untethered time.
Axman Member
Posts: 497 From: Derbyshire UK Registered: Mar 2023
posted 02-08-2024 06:19 AM
quote:Originally posted by Jim Behling: Those are the durations of the whole EVA and not time on the MMU.
...that does not indicate that they were credited as independent satellites.
I concede the first point, absolutely.
On the second, however, I have to disagree with you. The original question was not "were the spacewalkers assigned a COSPAR number, but was: "And was/were the individuals recorded as independent satellites?"
Whether the xx are mere placeholders or not, it is clear that Astronsutix regard them as satellites and are 'recorded' as such. Furthermore, COSPAR does not list "all" satellites, so whether a COSPAR number was assigned or not is irrelevant to the original question.
(They may appear in the NORAD listings, but I have no access to that. But, again, whether they have a NORAD ID or not is also irrelevant to the original question.)
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 02-08-2024 07:01 AM
This NASA photo shows McCandless in MMU #3 on EVA #1. From the photo caption:
Stewart later tried out the MMU McCandless is using here, and the two of them tested another similar unit two days later.
So maybe the earlier photo of Stewart in MMU #2 was taken on EVA #2.
Blackarrow Member
Posts: 3725 From: Belfast, United Kingdom Registered: Feb 2002
posted 02-08-2024 08:45 PM
quote:Originally posted by LM-12: I think that should count as untethered time.
Depends whether we're talking about a "human satellite" orbiting separately. If so, it can hardly be said that an astronaut on a MMU inside the cargo bay of the shuttle is orbiting separately. But I think that's getting a bit nerdish, and we're no nearer establishing if any of the previously-named astronauts completed at least one untethered orbit.
The British Interplanetary Society's "Spaceflight" magazine has a very comprehensive "Satellite Digest" which might answer this question. I have the bound volumes for 1984 and other relevant years, but unfortunately I'm not quite sure where I have them stored! Does anyone else have access to the 1984 volume?
Axman Member
Posts: 497 From: Derbyshire UK Registered: Mar 2023
posted 02-09-2024 06:58 AM
I think an important point is being missed here. The definition of a satellite is "an artificial body placed in orbit round Earth or moon or another planet."
Being placed in orbit is key. The object that is a satellite does not have to complete an entire orbit of the Earth. Just one second of independent 'orbital' flight is enough.
Sub-orbital probes that reach enormous apogee altitudes are not satellites as they never attain orbital flight. However, objects released from another body that is already on an orbital flight path, no matter if recaptured by the same body soon afterwards, do qualify as independent satellites (unless they are retrofired into a path that gives a de-orbital descent into the atmosphere).
So, somebody floating unattached in a payload bay is orbiting, and is therefore a satellite whether they leave the bay or not. However, somebody wearing and using a maneuvering unit, if still tethered, or holding onto the shuttle surfaces by hand, or attached by foot restraint is still part of the orbiting body and is not an independent satellite.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 02-09-2024 08:07 AM
That's how I see it.
The press kit for STS-41B is confusing because it refers to the maneuvering units as MMU-1 and MMU-2.
Blackarrow Member
Posts: 3725 From: Belfast, United Kingdom Registered: Feb 2002
posted 02-09-2024 10:14 AM
A "satellite" is artificial, but once you qualify the term by referring to a "human satellite" then you are obviously discussing an orbiting human, not a piece of equipment.
This goes a bit beyond the scope of my original questions, which still stand.
Axman Member
Posts: 497 From: Derbyshire UK Registered: Mar 2023
posted 02-09-2024 11:48 AM
Precisely. A human is not artificial, and cannot therefore be a satellite. But he can 'ride' a MMU. The maneuvering unit is the satellite, not (for e.g.) Bruce McCandless.
But to all intents and purposes we are talking about the astronaut not the manoeuvring unit. They are, apart from the defining qualities, one and the same!
Secondly, being exposed to open space, as opposed to inside a closed vessel, would be my defining moment of when to start defining independent orbiting, regardless of how close to the vessel one is.
Blackarrow Member
Posts: 3725 From: Belfast, United Kingdom Registered: Feb 2002
posted 02-09-2024 01:09 PM
"Human satellite" is simply an oxymoron, like "living dead."
Let's put it this way: if I had had the honour and privilege of flying the MMU in orbit, I would have seen myself in a different light if I had made a complete orbit of the Earth, untethered and completely outside my spacecraft. I suspect I would have called myself a "human satellite." I don't think a spacewalker tethered to the ISS would see himself in quite the same light.
Axman Member
Posts: 497 From: Derbyshire UK Registered: Mar 2023
posted 02-09-2024 02:09 PM
And what I'm saying is yes, I agree. Apart from the small matter of completing "one full Earth orbit"... I mean, 25 minutes, 92 minutes, 105 minutes... what's the difference when you're floating free in space with no means available to get back independently if something goes wrong?
Anybody strapped to an MMU untethered was an independent satellite. Full stop. It doesn't take a full 90 minute orbit at 200 miles altitude to qualify it as such.
LM-12 Member
Posts: 3973 From: Ontario, Canada Registered: Oct 2010
posted 02-09-2024 02:26 PM
Here is a bit of trivia from "Walking to Olympus" about the tethered EVA by Linda Godwin and Rich Clifford on STS-76:
Clifford wore the flight test SAFER unit used on STS-64, while Godwin wore a refurbished ground test unit.
Clifford was wearing SAFER #2 and Godwin was wearing SAFER #1.
posted 09-19-2023 08:12 AM
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