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Author Topic: CSM hibernation?  (Read 5067 times)
macieksoft
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« on: January 03, 2017, 04:41:15 PM »

I again launched my NASSP CSM to dock with Delta Glider...
...This time my RCS budget was not wasted as much as before and my SPS was all right. Unfortunately i have no idea how to perform rendezvous burns with VAGC so i was using EMS delta V burns and also direct thrusting.

...But this thread is not really about making rendezvous planning, however if you have some tips on how to use RTCC MFD to perform such manouvers you can post it here.
This thread is about CSM hibernation. Well, i don't know too much about what happened to CSM when attached to Skylab for long peroids of time but i guess they had to "hibernate" it to preserve cryo.

So what can i do when i want to hibernate CSM? Can i completely switch it OFF with no power at all (all fuel cells shut and no battery power)? Or maybe it will cause fuel cells to fail when i try to switch them ON.
And was there some kind of external power to CSM when it was attached to Skylab (i know it would not be modelled in NASSP, but i'd like to know anyway)?
I know that i can set crew to 0 in PAMFD to prevent ECS from geting poisoned, but what will happen to temperature inside CM when i switch all the systems OFF?
Will the glycool freeze if i switch off the pumps and bypass the radiators?
Can i switch off IMU together with its heaters? Or will the IMU freeze and say goodbye forever?
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indy91
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« Reply #1 on: January 03, 2017, 05:43:20 PM »

The CSM EPS is a very advanced simulation in NASSP. So you should be able to shut everything down and then start the CSM again from the batteries, like Apollo 13 did. The fuel cells can not be started again without Ground Support Equipment. Regarding how it was done for Skylab, here is an excerpt of the Skylab Reference Flight Plan:



So they let the 2 Fuel Cells (Skylab missions only had 2) run until depletion, then connected the CSM to Skylab power and did the reentry on the batteries. Pretty sure they had better batteries than the lunar missions, so they would hold up for a few hours.

There is a thermal engine in NASSP, so the temperature will probably go down without ECS running. What is not simulated (yet) is the heating all the systems provide for the cabin. This was a big reason why the temperature almost got to 0°C at the end for Apollo 13. If anything actually freezes, well, I at least know that the RCS won't work if the temperature is too low. I don't know if that is the case for all systems, so you have to try it I guess.

And regarding rendezvous, I would suggest using the Apollo 11 launch scenario for that, which has the AGC version Comanche055. Apollo 7-9 didn't have all the rendezvous programs yet, only TPI with Program 34. CSI (P32) and CDH (P33) had to be ground calculated maneuvers. And I also wouldn't use the Apollo 15 launch scenario (Artemis072), because the rendezvous programs are not fully compatible with Earth orbit anymore. Depending on how you want to rendezvous you have to use a tool like the RTCC MFD to set up the CSM in the right place, so that the AGC can be used for the rest. If you have any more specific questions about that, just ask.
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meik84
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« Reply #2 on: January 04, 2017, 09:14:44 AM »

The Skylab CSMs had 3 'DES batteries' in the SM, each rated at 500 Ah. I guess the CSM was in a 'half-powered' state when docked, with only the TELCOMs (the OWS had no own voice com system, only telemetry) and primary glycol loop running, all supplied from the station. The DES bats were then used after undocking until SM sep.
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macieksoft
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« Reply #3 on: January 04, 2017, 10:12:36 AM »

But what happened to the cryo after deplation? They needed it for ECS after separation from Skylab. Surge tank could not hold too much oxygen.
And why FC cannot be restarted? Is it a thermal issue (will they freeze), or what actually happens to them after shutdown?

And it would be nice to have some checklist for rendezvous. Also I have no idea on how to actually set up Lambert for TPI in RTCC MFD. Unfortunately A11 have problems with TVC DAP in NASSP do I would like to use another mission.
« Last Edit: January 04, 2017, 10:14:41 AM by macieksoft » Logged

indy91
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« Reply #4 on: January 04, 2017, 10:44:42 AM »

And it would be nice to have some checklist for rendezvous. Also I have no idea on how to actually set up Lambert for TPI in RTCC MFD.

You can find more information about the RTCC MFD in the manual, under "\Doc\Project Apollo - NASSP\Programmers Notes\ApolloRTCCMFD.pdf" At the very end the Apollo 7 TPI is described and before that all the MFD input parameters for the other Apollo 7 maneuvers, setting up the CSM in the correct position for rendezvous.

The rendezvous very much depends where you are and where your target is. The initial setup (before you would be able to use the Virtual AGC) is tricky. Perhaps you are in a orbit somewhere below your target and are slowly phasing towards it? One problem with the onboard targeting is that it depends on an initial knowledge of the TPI time. There isn't really a general answer for your question. Once you are on a standard rendezvous profile I can help you much more.

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Unfortunately A11 have problems with TVC DAP in NASSP do I would like to use another mission.

Does it? When have you tried it the last time? A lot has changed and Apollo 11 doesn't even use the same AGC version as the other missions anymore since August. And last I checked (probably August, too) the TVC worked even better than for Apollo 7-9.
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macieksoft
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« Reply #5 on: January 04, 2017, 10:51:13 AM »

Well. It was some time ago when I was checking TVC. I got full deflection of both gimbals every time CMC was in control of TVC. When I started burn I got crazy spin due to this deflection.
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meik84
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« Reply #6 on: January 04, 2017, 11:08:43 AM »

Quote
Surge tank could not hold too much oxygen.
Good question. The surge tank held 3.7 lbs at 900 psi, the repress package another 3 lbs or 3 kg total. AFAIK NASA calculated with 0.84 kg O2 per man and day so that 3 kg / (3*0.84 kg) would make 1.19 days or 28 h 33 min. Surge tank alone about 16 hours. Plus the oxygen in the cabin itself, which could be breathed away to some degree. More then enough, I'd say.
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Is it a thermal issue (will they freeze), or what actually happens to them after shutdown?
Sort of. The electrolyte (KOH solution) freezes at some point and then it's over.
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indy91
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« Reply #7 on: January 04, 2017, 11:28:24 AM »

The reference flight plan has the items "Remove air interchange duct" and "EPS, ECS, SPS Quiescent Mode Termination" just 2.5 hours before undocking. So CSM ECS won't really be needed before that.

Well. It was some time ago when I was checking TVC. I got full deflection of both gimbals every time CMC was in control of TVC. When I started burn I got crazy spin due to this deflection.

Docked burn with the LM? Because that was definitely fixed. And CSM alone should also be no problem in the Apollo 11 scenario since August, and in the Apollo 10 scenario (using the same AGC version) since last January.
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macieksoft
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« Reply #8 on: January 05, 2017, 10:41:55 AM »

Quote
Surge tank could not hold too much oxygen.
Good question. The surge tank held 3.7 lbs at 900 psi, the repress package another 3 lbs or 3 kg total. AFAIK NASA calculated with 0.84 kg O2 per man and day so that 3 kg / (3*0.84 kg) would make 1.19 days or 28 h 33 min. Surge tank alone about 16 hours. Plus the oxygen in the cabin itself, which could be breathed away to some degree. More then enough, I'd say.
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Is it a thermal issue (will they freeze), or what actually happens to them after shutdown?
Sort of. The electrolyte (KOH solution) freezes at some point and then it's over.
But why they didn't simply added heaters to prevent electrolyte from freezing? It would be much more "elegant" solution than forcing the crew to use batteries that had much more limited capacity. It would also take less weight. So after shutdown of FC they could run heaters and  probably also pumps on power from Skylab, and then they could restart them when needed.

I also wonder how it was done in SS. Could SS FC be restarted?

And was the surge tank and repress package tanks modified for Skylab missions? In NASSP in Apollo 7 and 8 scenarios i am getting enough oxygen to do reentry, but nothing more than reentry.
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meik84
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« Reply #9 on: January 05, 2017, 12:10:44 PM »

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In NASSP in Apollo 7 and 8 scenarios i am getting enough oxygen to do reentry, but nothing more than reentry.
Hm. You're right, the pressure drops way to fast once you close the SM supply valve. The O2 flow itself is about right, according to the meter. Maybe both tanks are too small, but I can't find the actual size in the code. Maybe somebody has a deeper insight there and can help.
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Puma
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« Reply #10 on: January 05, 2017, 12:56:58 PM »

 What?
Hi macieksoft, your video tutorial here :

https://www.youtube.com/watch?v=Kgsw3_d8fkc&feature=youtu.be

is quite awesome, it had help me a lot in NASSP. I am having a little trouble with the P52 procedure in Apollo 7, its been quite difficult for me to get it right, since I see you know how to make a good working NASSP tutorial, I wonder if you could make another short video tutorial by using the latest build: NASSP-V7.0-RC-master-314, with the MCC Up links included showing the P52 procedure. Thanks.
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macieksoft
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« Reply #11 on: January 05, 2017, 03:05:03 PM »

Well, the problem with P52 tutorial is that P52 has 4 different options. I know how to use option 2 but i am not sure about the other. This is why i didn't made P52 tutorial.
I also never tried MCC uplinks, all uplinks i am using are from PAMFD. Its mainly because i am not focusing on recreating any historic flight, i always was a king of experimentator who tries different thing with NASSP CSM Happy

Option 2 is fairly simple, just follow the checklists.
First you have to enter GET. It will align your IMU to local vertical at specific GET, thats how option 2 works.
Then you getting coarse align of the IMU.
Then you are making sighting on 2 stars, much like P51 but in P52 you can let CMC to position optics somewhere near the star and just do the little correction to make it more precise.
Then AFAIK you are getting balls, this is the star angle difference Happy
And then there should be the torgue, AFAIK torque is a kind of fine IMU align.
Finally it asks you if you want to check how precise your orientation is, i am always bypassing this step.
« Last Edit: January 05, 2017, 03:10:52 PM by macieksoft » Logged

Puma
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« Reply #12 on: January 05, 2017, 04:41:13 PM »

I really appreciate your quick response, but I really learn by watching and not by reading. Everyone is not the same is this world, I have an special condition so that's how I understand. I do everything I watch at YOUTUBE, but if you make a video maybe I get into it, but Thanks any way. Yes  

   
“Example isn't another way to teach, it is the only way to teach”

Albert Einstein
« Last Edit: January 05, 2017, 05:11:32 PM by Puma » Logged
macieksoft
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« Reply #13 on: January 08, 2017, 02:11:02 PM »

Well, i am just trying to hibernate it and i found that it already has fuel cell heaters.

I did following things:
I just removed all the crew to simulate air conditioning from DGIV :-P Anyway, it would be nice to have some option in PAMFD to simulate air conditioning from Skylab.
I shut down so many systems. All comms, whole CMC + IMU and its heaters. Everything related with SCS was also killed, so no BMAG, no FDAI etc. Well, preatty much all the systems that are not required.
I let the glycool flow, but i decided to bypass radiators because temp was getting low, even heaters were not so much helpfull.

Then i shut down FC2 and i started getting FC rad out temp low so i bypassed radiators. OFC all FC heaters remained ON to do not let them freeze.
There is no simulated power from station (or DGIV) to CMC so i decided to keep EPS running on FC1 and FC3. I know that one FC would be more than enough but this is the first test so i prefeer to keep 1 and 3 running because i am still not sure if i will be able to restart FC2.

Then i did time acceleration to skip about 15 hours.

I will let you know what happened when i try to restart everything.

BTW: Has anybody idea what was nitrogen in fuel cell system for? I am reading some docs about CSM and i found they have nitrogen system with nitrogen tanks for something.

Quote
here is an excerpt of the Skylab Reference Flight Plan:
Well, do you know how to vent LH2? Nevermind they had such option.
« Last Edit: January 08, 2017, 02:14:35 PM by macieksoft » Logged

meik84
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« Reply #14 on: January 08, 2017, 07:22:43 PM »

Quote
Has anybody idea what was nitrogen in fuel cell system for?
The N2 pressurizes the electrolyte, the glycol accumulator and provides a reference pressure for the H2 and O2 regulators. Some sort of 'service air', only more pure and most important CO2 free -KOH absorbs CO2 (it was one mature ingredient of soda lime in the old days).
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