Author Topic: A Question About Eagle Lunar Stay Times  (Read 879 times)

Offline Daelkyr

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A Question About Eagle Lunar Stay Times
« on: 08/02/2017 04:08 AM »
Hello all. First time poster here.
I've searched for the answer to two questions but can't seem to find them.

First, and the most pressing:

What were the Life Support amounts for Eagle (LM-5). I know that Apollo 12-14 (H Missions) were set for 48 hours of use with (I believe) a 6 hr reserve for lunar rendezvous emergencies. Was Eagle similarly supplied or was it's supplies less? Any help would be appreciated.

As an aside question: were there every any tests if this long an astronaut could survive in the A7 suit without the PLSS? This answer also seems to elude me.

Thanks again for any help.

- Josh

Offline Jim

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Re: A Question About Eagle Lunar Stay Times
« Reply #1 on: 08/02/2017 01:32 PM »
No, there would have not been any such tests. 

Offline kbalch

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Re: A Question About Eagle Lunar Stay Times
« Reply #2 on: 08/02/2017 03:56 PM »
On the lunar surface, with a complete PLSS failure, the OPS was good for 30 minutes.  Lots of relevant info to be found at these two links:

https://www.hq.nasa.gov/alsj/alsj-OPS.html
http://www.workingonthemoon.com/WOTM-OPS.html

Offline the_other_Doug

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Re: A Question About Eagle Lunar Stay Times
« Reply #3 on: 08/07/2017 07:23 PM »
Hi, guys!

De-cloaking for a minute, here -- extreme family concerns have taken almost all of my spare time for the past, what, nearly a year, so while I keep touch with the fora here, I've had no time to post.

But this one question got me to decide to post a quick response.  Well, quick for me... ;)

First and foremost, LM-5 was fully fueled and provisioned, it had the same amount of consumables as, say, LM-6.  For the first landing, the surface stay time was limited simply to provide greater cushions.  The actual performance of the systems during a landing mission was not completely known (since this was the first one), so they wanted to make sure there were good margins on as many things as possible.

The real answer, on LM lifetimes in general, of course, is -- it depends.  On a few factors.

The G and H mission versions of the LM -- the baseline landing-capable configurations, prior to the J-series Extended LMs (*) -- were generally referred to as 45-hour spacecraft.  This meant that the consumables could, with good surpluses, support lunar surface stay times of up to 38 hours, fully powered up for what was needed at each stage of the flight.  The H-mission baseline had been to support surface stay times of up to 35 hours, but surpluses were good enough through the first two landings that the final H missions were planned for surface stay times of up to 38-39 hours.

It is, however, important to remember that the LM consumables were split into the ascent and descent stage consumables.  Up to the point of final preparations for lunar lift-off, the LM used power, water and oxygen from the descent stage.  And as all of us who have read detailed accounts of the Apollo 13 flight have learned, water (for cooling the electronics) was the constraining consumable.

For each of the H missions, there were healthy remaining consumables in the descent stages at the time they were abandoned on the surface.  So, had there been an emergency need to extend the lunar surface stay times with any of these vehicles, you could have done this by severely powering down systems, a la Apollo 13.  The duration by which you could extend the lifetime would depend on when, during your stay time, you decided you needed to power down and conserve consumables.  So, you could extend surface stay times for up to 40 or 50 additional hours if you powered down to just oxygen flow and the low-power radio transmitter, again a la Apollo 13.  But only if you started right after landing.  Once you were near the end of the planned stay, there would only be consumables enough to stretch for maybe another half a day.

But that applies to the period while the ascent and descent stages are attached.  Regardless of G, H or J missions, the ascent stage had enough consumables to support just that stage for something like eight hours, fully powered up.  That, of course, could be extended if some of the gear was powered down, but the oxygen and water constraints were much more severe in just the ascent stage than for the combined vehicle.

So, the ascent stage, once you separated and had lifted off from the surface, had a very severely limited lifetime.  If the original three-rev, 6-hour co-elliptic rendezvous sequence not gone off as planned, they needed to get the spacecraft together with no more than about a three-revolution slip past the planned three-revolution rendezvous.  In other words, you had about twelve hours after launch from the surface to get docked, before you started running out of cooling water.  And that factored in powering down the radar systems and some of the radio gear for part of that time.

Just to let you know what the timing for water depletion for just the ascent stage looked like, on Apollo 11, the ascent stage was cast off and just left in orbit, powered up.  No de-orbit maneuver occurred.  It ran out of cooling water less than one full revolution after its final undocking from Columbia.  The electronics continued to work for another hour or more before failing from overheating.

So, to recap -- you could extend a G- or H-mission surface stay by a sliding scale of time, depending on when you started.  But for any version of the LM, once the ascent stage had cast off from the descent stage, you had at most about 12 hours before systems began to fail.

As for the testing of spending long periods of time in an A7 pressure suit -- I know some tests were done of operating the spacecraft, pushing the water gun and food sticks through the little "chow locks" in the neck ring of the suit, emptying the urine collection bags, etc., in pressurized suits in one of the vacuum chambers.  But as far as I know, these were fairly short tests, to make sure it could all be done, and everyone involved knew how to do it, in an emergency.  I don't think they ever made any poor sod sit there for a week in a hard suit... ;)


(*) -- The J-series LM was referred to as the ELM, for "Extended Lunar Module", for more than a year after studies and then manufacturing funding were approved to provide for J-mission surface capabilities.  It was as late as 1970 when the directive came to reference these spacecraft as simply the LM, dropping the "E" from the acronym.

This came after the decision to move lunar missions past the first landing from the Apollo Applications umbrella into what was called "Mainline Apollo".  Up to that point, Apollo would only have designated missions up through the first landing, and all missions thereafter would have been called Apollo Applications missions.  FYI.  :)
-Doug  (With my shield, not yet upon it)

Offline zubenelgenubi

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Re: A Question About Eagle Lunar Stay Times
« Reply #4 on: 08/07/2017 08:18 PM »
Good to hear from you again, t_o_Doug!
Support your local planetarium!

Offline Kansan52

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Re: A Question About Eagle Lunar Stay Times
« Reply #5 on: 08/07/2017 10:58 PM »
Good luck!!

Thanks for the info. The more I learn about Apollo the more I appreciate how close to the edge they flew!

Offline the_other_Doug

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Re: A Question About Eagle Lunar Stay Times
« Reply #6 on: 08/08/2017 10:04 PM »
Thanks, guys!  I'm in a bit of a lull in things at the moment, which is why I have a minute or two for posting, here.  I don't suspect it will last for long -- unless things turn considerably worse, which could then free up some of my time, but at the expense of losing a loved one.  (It's a truly long story.)

As for running Apollo right up to the edge -- yeah, they did.  Especially in the J missions.  Take, as just one example, the J-series "extended" PLSS life support backpacks.

All they did to extend the PLSS lifetime was to pump up the pressure in the oxygen tanks (both in the PLSS and in the OPS, the emergency oxygen bottle worn atop the PLSS).  That's really about it.  And instead of keeping the reserve cooling water tank in reserve, in case of a leak or other problem in the main water tank, the 7-hour lifetime was based on *always* switching to the secondary water tank, between five and six hours into the EVAs.

So, to get seven-plus hours of EVA out of the PLSSes, they ran them until they were almost empty... ;)

This is why Bob Gilruth got more and more uncomfortable as the later landings proceeded.  The system was as mature as it was going to get, and yet each mission faced anomalies and malfunctions which ranged from a full-on, life-threatening mission abort, to problems which, if they had been encountered in conjunction with just one more major problem, could have easily caused mission aborts at the least, and fatal accidents at the worst.

But... that element of risk just made the accomplishments all the more inspiring.  :)
-Doug  (With my shield, not yet upon it)

Offline Kansan52

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Re: A Question About Eagle Lunar Stay Times
« Reply #7 on: 08/08/2017 11:20 PM »
But... that element of risk just made the accomplishments all the more inspiring.  :)

So true!

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