NASASpaceFlight.com Forum
General Discussion => Historical Spaceflight => Topic started by: jaysne on 01/04/2015 01:52 am
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On those missions, astronauts Mattingly, Worden and Evans did spacewalks to retrieve film canisters from the service module after the command/service module had left lunar orbit and was speeding back toward Earth.
My question is, were they tethered to the spacecraft somehow? And even if they were, how did they stay in the same place in space relative to the spacecraft? After all, the spacecraft was moving at thousands of miles per hour and the walkers were not moving at all.
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They were all tethered, however your intuition about relative velocity is wrong. Consider Newton's first law of motion: the tendency of a body in motion to remain in motion unless acted upon by an outside force.
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They did have a tether. But you're misunderstanding a few basic concepts here. The spacewalkers are traveling at the same thousands of miles per hour as the spacecraft, it's just that their relative velocities are small or zero, so they stay together. There's (almost) nothing to cause drag in space, so they could be traveling 10 times as fast, and still be fine.
edit: what QuantumG said.
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Okay… I think what you're saying is that because they were in the spacecraft before they got out, they assumed the velocity of the craft, and when they got out, they kept up the same velocity?
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Okay… I think what you're saying is that because they were in the spacecraft before they got out, they assumed the velocity of the craft, and when they got out, they kept up the same velocity?
Yeah, that's a reasonable way to say it.
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My question is, were they tethered to the spacecraft somehow? And even if they were, how did they stay in the same place in space relative to the spacecraft? After all, the spacecraft was moving at thousands of miles per hour and the walkers were not moving at all.
i think you've got the basic idea, but how about this for a mental image: let's say you're in an airplane and you stand up in the aisle and jump! do you suddenly fly backwards to the rear of the airplane? no, you don't. your body is moving along with the airplane, several hundred miles per hour. it would be a little bit different if you jumped out the door, due to drag from the air slowing you down and the fact that the airplane has engines that are pushing it forward.
however, in space there's no drag from the air, and because of that a spacecraft doesn't need to have its engines on all the time. rockets in space fire for a short time to get up to speed, and then they switch off the engines and coast. the majority of the time they are in space, spaceships don't fire their rocket engines at all (this is one of the things that science fiction movies do wrong all the time, because in the movies they have the rocket engines firing all the time on their spaceships - this is just for dramatic effect). so when the astronauts were doing their space walks, they were not firing the rocket engines. the spacecraft was coasting, and the astronauts were coasting along with the spacecraft, just like you would if you jumped inside of an airplane.
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Those were very cool and unique spacewalks, with both the moon and the earth appearing quite small in the sky.
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What kind of spacesuits were worn on these spacewalks? Was it the same spacesuit used for walking on the surface of the Moon? Are there pictures of these spacewalks?
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The spacewalks were performed by the CMP (Command Module Pilot), who stayed up in the CM during the moonwalks. His spacesuit's umbilical connections were different from the moonwalking suits, which had to provide connections for the the life-support backpacks. There may have been other differences.
The Apollo 15 and 16 (?) spacewalks were shown live on network TV. I recall Apollo 17 was not shown live:
https://www.youtube.com/watch?v=-mwfNAm4e9Y
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What kind of spacesuits were worn on these spacewalks? Was it the same spacesuit used for walking on the surface of the Moon? Are there pictures of these spacewalks?
they wore the pressure suits they wore at launch for the EVAs. the CM was fully depressurized for the spacewalk, so all three astronauts were suited up and they were hooked into the Command Module's life support system. there are a couple of pictures and some more information in this reddit thread: http://www.reddit.com/r/space/comments/23mk31/during_the_apollos_evas_en_route_not_on_the_moon/
there are more pictures available in the mission links at the Apollo Archives: http://www.apolloarchive.com/apollo_gallery.html
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On a related note and maybe a daft question - Was it feasible on the Apollo 13 mission for similar space walk to have been carried out to inspect the damage after the explosion to find out the extent of the damage . They had eva suits, and even if it wasn't an option to depressurise the command module they still could have gone out and back in via the the LM. Was it even considered on the ground to conduct such an ad hoc mission with dubious gains & risks attached?
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On a related note and maybe a daft question - Was it feasible on the Apollo 13 mission for similar space walk to have been carried out to inspect the damage after the explosion to find out the extent of the damage . They had eva suits, and even if it wasn't an option to depressurise the command module they still could have gone out and back in via the the LM. Was it even considered on the ground to conduct such an ad hoc mission with dubious gains & risks attached?
No. They did not have either the consumables or the time. The CM/SM was rapidly dying so they had to transfer the platform alignment to the LM and power down as soon as possible if they were going to have enough for the duration of the trip back. They had to save whatever was left in the CM (batteries) for entry, and they could not waste any of the capabilities of the LM. Also, trying to do an eva in the unknown conditions of the damaged spacecraft (debris, venting, no hand-holds, etc.) would have been too hazardous.
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What kind of spacesuits were worn on these spacewalks? Was it the same spacesuit used for walking on the surface of the Moon? Are there pictures of these spacewalks?
they wore the pressure suits they wore at launch for the EVAs. the CM was fully depressurized for the spacewalk, so all three astronauts were suited up and they were hooked into the Command Module's life support system...
The Apollo pressure suits, made by the International Latex Corporation (ILC), had a model number of A7L. (The A stood for Apollo.) Two different versions of the suits were created, the A7L and the A7LB. Of each of those versions, there was an Intra-Vehicular (IV) suit and an Extra-Vehicular (EV) suit.
First off, the EV suits differed from the IV suits in having an extra set of micrometeoroid and thermal protection layers, and having connections for the water cooling to flow from the LM or the PLSS backpack into the water-cooled underwear worn by the moonwalkers. The IV suit could be attached only to the air hoses in the CM, and didn't support the water-cooled underwear. Also, the EV suits were designed to accommodate the visor assemblies, backpack straps, lunar overshoes, etc., while the IV suits had no special fixtures or connections for most of those items.
The A7L differed from the later A7LB suits mostly in the EV suits. These had extra waist jointing added to help the moonwalkers bend over farther and move their hips better, which let them more easily sit down in the Rover seats and generally made it easier for the LM crews to move around on the lunar surface. (Also, the A7L suits had a nifty gray teflon pad woven into the suit backs, to protect the suit's easily frayed Beta cloth exterior from being chafed by the PLSS backpacks. The A7LB EV suits lacked those teflon pads, the Beta cloth being toughened with some kind of treatment instead.)
The A7LB IV suits were adapted to be connected both to the CM's oxygen hoses and to one of the OPS emergency oxygen bottles that the moonwalkers used during their moonwalks. The addition of the OPS gave the spacewalking CM pilots an emergency backup capability that made the trans-lunar spacewalks a lot safer to attempt.
On Apollos 7 and 8, all crew members wore the A7L IV suits. On Apollos 9 through 14, the LM crews wore the A7L EV suits, while the CM pilots wore the A7L IV suits. On Apollos 15 through 17, the LM crews wore A7LB EV suits, and the CM pilots wore the A7LB IV suits.
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On a related note and maybe a daft question - Was it feasible on the Apollo 13 mission for similar space walk to have been carried out to inspect the damage after the explosion to find out the extent of the damage . They had eva suits, and even if it wasn't an option to depressurise the command module they still could have gone out and back in via the the LM. Was it even considered on the ground to conduct such an ad hoc mission with dubious gains & risks attached?
No. They did not have either the consumables or the time. The CM/SM was rapidly dying so they had to transfer the platform alignment to the LM and power down as soon as possible if they were going to have enough for the duration of the trip back. They had to save whatever was left in the CM (batteries) for entry, and they could not waste any of the capabilities of the LM. Also, trying to do an eva in the unknown conditions of the damaged spacecraft (debris, venting, no hand-holds, etc.) would have been too hazardous.
Well, hmm... yes and no. Your "also" points are actually more germane than your main points.
The main consumable you used during an EVA was the oxygen. Despite what most people think, the LM had plenty of oxygen. It was designed for three full depress/repress cycles on an H mission such as 13, two EVAs plus a third depress to jettison the PLSSes, trash, etc. The LM also had its cabin purged of air several times during the outbound trip, to vent the regular Earth-normal air it launches with and replace it with pure oxygen, and to purge any possible outgassing from the equipment, etc., before the crew moved in for landing operations. So, in all, the oxygen was not a limiting consumable in Aquarius, and indeed could have supported an EVA during trans-Earth coast.
Power was only slightly more limiting. You could probably deal with having the LMP and CMP on the suit circuit and the CDR on his PLSS, and the suit circuit fans took about the same amount of electricity out of the batteries as the cabin fans did. The depress and repress operations took no power -- you just closed the valves from the oxygen tanks and opened the valve to the great outdoors to depress, and reversed that process to repress. No air pumps were used to effect either the depress or the repress. You might use a tiny bit more power doing an EVA than if you didn't, but not enough to have made any real difference.
The most limited consumable, water, would not be affected by an EVA, either. The PLSSes were pre-loaded with their cooling water, and only the EVA astronaut would need to use the liquid cooling garment for thermal control. The LM water was critical for cooling the LM's electronics, which would not be needed any more with or without an EVA.
Time was not a limitation, because there would be absolutely no reason to go EVA during the period between the accident and the shutdown of the CSM. Knowing exactly what happened, or at least seeing the damage, would have done nothing to extend the CSM's life or change the need to move the crew into the LM. You would have done an EVA during trans-Earth coast, if at all. When there was plenty of time to do one.
The biggest technical reason not to do an EVA was, as you mentioned, the area where the damage was visible had no handholds or other ways for a guy to maintain his body position. It had torn and broken metal, and for at least a while had some remnant outgassing from the various lines that ran through that SM bay. It was an unhealthy place to ask a guy in a space suit to go.
The actual biggest reason why not to do an EVA was -- why? You knew that, if you got the crew home, you would be able to see the damage after you jettisoned the SM, and get pictures of it, without risking an EVA. They had enough telemetry to have determined pretty well what had happened before the crew ever got home, so even if the crew failed to get home with their pictures and eyewitness accounts, it would have made no difference in the accident investigation.
The only reason I have ever been able to think of for doing an EVA on 13 was to see if they could tell whether or not the tank explosion damaged the heat shield on the Apollo CM. Problem is, you likely couldn't have seen the heat shield well enough to tell, even through the hole where the bay door was blown out. And also -- if you saw that the heat shield was badly cracked or even had a big chunk taken out, what good would it have done? If that had been the case, the crew was dead regardless. There was absolutely no way to repair a cracked or broken Apollo heat shield with what the crew had on hand.
So, with no compelling reason to do an EVA, they made the best decision, and didn't even think about it.
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The most limited consumable, water, would not be affected by an EVA, either. The PLSSes were pre-loaded with their cooling water, and only the EVA astronaut would need to use the liquid cooling garment for thermal control. The LM water was critical for cooling the LM's electronics, which would not be needed any more with or without an EVA.
My thinking was that, in not powering down the LM for the amount of time it would have taken for the EVA (hours, probably) they would have been using power, and along with that cooling water, at a higher rate than they would have powered down. At that point in the problem they could not afford the expenditure.
<edit, addition>
Ok, having said all that and recognizing the conclusion, COULD the crew have done an EVA to examine the damage?
Let's assume the CM/SM is in fact dying and has only a limited life to go, too short a time for the EVA. The CM pilot has to either remain in the pressurized CM while the rest of the crew are in the LM which will be depressed for the EVA crewman to go outside, OR be able to connect to the LM suit circuit during the EVA, while the EVA astronaut is on his PLSS. Swigert was wearing the the A7L IV suit, which could not connect to the EVA OPS. Could that suit connect to the LM suit circuit?
More practically, would three suited crewmembers, one wearing the PLSS/OPS even fit in the LM cabin, with enough room for the EVA crewman to maneuver in and out if the hatch?
Final point comes to mind... were there even restraint tethers on board, long enough for the EVA? Once the EVA crewman got past the handholds around the CM side hatch, was there anything to even attach one to?
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What kind of spacesuits were worn on these spacewalks? Was it the same spacesuit used for walking on the surface of the Moon? Are there pictures of these spacewalks?
they wore the pressure suits they wore at launch for the EVAs. the CM was fully depressurized for the spacewalk, so all three astronauts were suited up and they were hooked into the Command Module's life support system...
The Apollo pressure suits, made by the International Latex Corporation (ILC), had a model number of A7L. (The A stood for Apollo.) Two different versions of the suits were created, the A7L and the A7LB. Of each of those versions, there was an Intra-Vehicular (IV) suit and an Extra-Vehicular (EV) suit.
First off, the EV suits differed from the IV suits in having an extra set of micrometeoroid and thermal protection layers, and having connections for the water cooling to flow from the LM or the PLSS backpack into the water-cooled underwear worn by the moonwalkers. The IV suit could be attached only to the air hoses in the CM, and didn't support the water-cooled underwear. Also, the EV suits were designed to accommodate the visor assemblies, backpack straps, lunar overshoes, etc., while the IV suits had no special fixtures or connections for most of those items.
The A7L differed from the later A7LB suits mostly in the EV suits. These had extra waist jointing added to help the moonwalkers bend over farther and move their hips better, which let them more easily sit down in the Rover seats and generally made it easier for the LM crews to move around on the lunar surface. (Also, the A7L suits had a nifty gray teflon pad woven into the suit backs, to protect the suit's easily frayed Beta cloth exterior from being chafed by the PLSS backpacks. The A7LB EV suits lacked those teflon pads, the Beta cloth being toughened with some kind of treatment instead.)
The A7LB IV suits were adapted to be connected both to the CM's oxygen hoses and to one of the OPS emergency oxygen bottles that the moonwalkers used during their moonwalks. The addition of the OPS gave the spacewalking CM pilots an emergency backup capability that made the trans-lunar spacewalks a lot safer to attempt.
On Apollos 7 and 8, all crew members wore the A7L IV suits. On Apollos 9 through 14, the LM crews wore the A7L EV suits, while the CM pilots wore the A7L IV suits. On Apollos 15 through 17, the LM crews wore A7LB EV suits, and the CM pilots wore the A7LB IV suits.
Interesting. Did the LM crews have to clean off their suits before returning to the command module, then? In pictures the suits are filthy from walking around on the surface of the Moon.
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The most limited consumable, water, would not be affected by an EVA, either. The PLSSes were pre-loaded with their cooling water, and only the EVA astronaut would need to use the liquid cooling garment for thermal control. The LM water was critical for cooling the LM's electronics, which would not be needed any more with or without an EVA.
My thinking was that, in not powering down the LM for the amount of time it would have taken for the EVA (hours, probably) they would have been using power, and along with that cooling water, at a higher rate than they would have powered down. At that point in the problem they could not afford the expenditure.
<edit, addition>
Ok, having said all that and recognizing the conclusion, COULD the crew have done an EVA to examine the damage?
Let's assume the CM/SM is in fact dying and has only a limited life to go, too short a time for the EVA. The CM pilot has to either remain in the pressurized CM while the rest of the crew are in the LM which will be depressed for the EVA crewman to go outside, OR be able to connect to the LM suit circuit during the EVA, while the EVA astronaut is on his PLSS. Swigert was wearing the the A7L IV suit, which could not connect to the EVA OPS. Could that suit connect to the LM suit circuit?
More practically, would three suited crewmembers, one wearing the PLSS/OPS even fit in the LM cabin, with enough room for the EVA crewman to maneuver in and out if the hatch?
Final point comes to mind... were there even restraint tethers on board, long enough for the EVA? Once the EVA crewman got past the handholds around the CM side hatch, was there anything to even attach one to?
If you were to have done an EVA on 13 to check out the damage, you would have closed the hatch to the CM and just depressed the LM. Except for powering up the VHF radio circuit to communicate with the EVA astronaut, you wouldn't have to power up the LM any further than it was powered up for the trans-Earth coast in real life.
Your biggest issue is the correct one -- fitting three guys in suits into the LM cabin and trying to get one of them out the front door at the same time. Swigert could connect his O2 hoses to the LM suit circuit, but the EVA guy (I figure that would have been Lovell) would have to be on the PLSS O2 from the time he sealed up his suit. But even with Swigert floating up into the tunnel area, with the CM hatch closed there's not lots of room back there.
AFAIK, Apollo 12 was the last flight to carry the 100-foot tether designed for entering craters on foot (since they were to enter the Surveyor crater and didn't know if they might need to have just one guy go down to the Surveyor with the other holding on to the rope). There wouldn't be handholds in the area of the SM where the explosion happened, so the EVA crewman would have had to grab onto possibly sharp ends where the SM bay door blew off. So, no -- it would have been a dangerous and unhealthy place for the EVA guy to approach and work around.
Again, there would never have been an opportunity to try and go EVA while the crew was moving over to the LM. They barely got the LM powered up and the platform alignment moved from the CSM to the LM before the CSM died -- that was simply not a time where they crew could have gone into a two-hour EVA prep. And any less time for EVA prep would have compromised safety so much that even the idea of an EVA would be canned. The only timeframe when an EVA could have been attempted would have been during trans-Earth coast.
And again, there would have been nothing anyone could have done on EVA to keep the CSM alive any longer. The EVA wasn't needed for the accident investigation, and could have killed someone just by itself. Therefore, with no pressing need to do so, trying an EVA was a lot of risk for no return.
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What kind of spacesuits were worn on these spacewalks? Was it the same spacesuit used for walking on the surface of the Moon? Are there pictures of these spacewalks?
they wore the pressure suits they wore at launch for the EVAs. the CM was fully depressurized for the spacewalk, so all three astronauts were suited up and they were hooked into the Command Module's life support system...
The Apollo pressure suits, made by the International Latex Corporation (ILC), had a model number of A7L. (The A stood for Apollo.) Two different versions of the suits were created, the A7L and the A7LB. Of each of those versions, there was an Intra-Vehicular (IV) suit and an Extra-Vehicular (EV) suit.
First off, the EV suits differed from the IV suits in having an extra set of micrometeoroid and thermal protection layers, and having connections for the water cooling to flow from the LM or the PLSS backpack into the water-cooled underwear worn by the moonwalkers. The IV suit could be attached only to the air hoses in the CM, and didn't support the water-cooled underwear. Also, the EV suits were designed to accommodate the visor assemblies, backpack straps, lunar overshoes, etc., while the IV suits had no special fixtures or connections for most of those items.
The A7L differed from the later A7LB suits mostly in the EV suits. These had extra waist jointing added to help the moonwalkers bend over farther and move their hips better, which let them more easily sit down in the Rover seats and generally made it easier for the LM crews to move around on the lunar surface. (Also, the A7L suits had a nifty gray teflon pad woven into the suit backs, to protect the suit's easily frayed Beta cloth exterior from being chafed by the PLSS backpacks. The A7LB EV suits lacked those teflon pads, the Beta cloth being toughened with some kind of treatment instead.)
The A7LB IV suits were adapted to be connected both to the CM's oxygen hoses and to one of the OPS emergency oxygen bottles that the moonwalkers used during their moonwalks. The addition of the OPS gave the spacewalking CM pilots an emergency backup capability that made the trans-lunar spacewalks a lot safer to attempt.
On Apollos 7 and 8, all crew members wore the A7L IV suits. On Apollos 9 through 14, the LM crews wore the A7L EV suits, while the CM pilots wore the A7L IV suits. On Apollos 15 through 17, the LM crews wore A7LB EV suits, and the CM pilots wore the A7LB IV suits.
Interesting. Did the LM crews have to clean off their suits before returning to the command module, then? In pictures the suits are filthy from walking around on the surface of the Moon.
They tried to clean off their suits, yes. They had a little vacuum cleaner they used to clean off the rock boxes, film magazines and suits. But there was so much dirt that on some return voyages, dust floated off the suits and gear and clogged up the CM air filters.
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but the EVA guy (I figure that would have been Lovell) would have to be on the PLSS O2 from the time he sealed up his suit.
And it would be dumping water vapor into the cabin.
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but the EVA guy (I figure that would have been Lovell) would have to be on the PLSS O2 from the time he sealed up his suit.
And it would be dumping water vapor into the cabin.
Only after he started running the PLSS water cooling sublimator. And the nominal LM depress happened while two PLSSes were dumping water vapor, so it's not a real off-nominal situation. Once the front door was opened, the tiny pressure caused by the PLSS water vapor venting becomes negligible. (But close the hatch and the vent valve, and a PLSS did build up a little cabin pressure pretty fast.)
The EVA guy would have had the PLSS cooling up and running, though, while setting up. Also, there is a fair amount of air in the suit to breathe, so you could fasten helmet and gloves and be off the suit circuit and be able to breathe for 15 minutes or more. That happened to Pete Conrad, actually, and the first sign that he was breathing down the air in his suit was that the suit pulled in against him, particularly the shoulders pulled down such that he couldn't straighten his body out. He figured he was off the suit circuit but hadn't yet started the PLSS O2, and just started PLSS O2 to fix it. It didn't actually cause a problem.
Speaking of water, though, you'd likely end up running the suit circuit for Haise and Swigert but keep the water separators powered down, to conserve LM electricity. So, if those guys ended up sweating, you ran the risk of fouling the suit circuit with perspiration.
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On Apollo 12 and beyond, with the astronauts on the moon doing multiple EVAs, did they need to replenish their backpacks with consumables from the LM systems?
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Yes. They refilled the water and oxygen tanks from the LM stores, and replaced the battery pack that ran the PLSS pumps, the radio, etc., for each EVA. Even Apollos 9, 10 and 11 had the LM and PLSS fixtures to replenish the backpacks, they just didn't use them. In fact, they had to be careful to follow the proper instructions or the refills didn't go right. On Apollo 15, a combination of the LM being at a tilt and a crew desire to refill both backpacks at once led to Irwin's water fill being both less than normal, and having ingested too much oxygen, because it was filled pretty much on its side. It caused enough of a refill issue that his PLSS kept generating error tones throughout the early part of EVA-2.