Author Topic: NASA evaluating CCP Loss Of Crew and Mishap procedures  (Read 17686 times)

Offline yg1968

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #40 on: 09/10/2015 02:10 PM »
The discussion about safety has me wondering. Will commercial crew have some kind of flip maneuver or other visual inspection to see if the heatshield of the capsule is fit for reentry (i.e. that there hasn't been any micrometeorite damage to its heatshield during its stay at the ISS)?
« Last Edit: 09/10/2015 02:12 PM by yg1968 »

Offline Graham

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #41 on: 09/10/2015 02:19 PM »
The discussion about safety has me wondering. Will commercial crew have some kind of flip maneuver or other visual inspection to see if the heatshield of the capsule is fit for reentry (i.e. that there hasn't been any micrometeorite damage to its heatshield during its stay at the ISS)?

The heat shields won't be visible, they're protected by the trunk/ SM so MMOD damage/ damage on ascent isn't a concern like it was for the orbiters who had an exposed TPS
« Last Edit: 09/10/2015 02:23 PM by Graham »
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Offline yg1968

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #42 on: 09/10/2015 02:52 PM »
The discussion about safety has me wondering. Will commercial crew have some kind of flip maneuver or other visual inspection to see if the heatshield of the capsule is fit for reentry (i.e. that there hasn't been any micrometeorite damage to its heatshield during its stay at the ISS)?

The heat shields won't be visible, they're protected by the trunk/ SM so MMOD damage/ damage on ascent isn't a concern like it was for the orbiters who had an exposed TPS

I wasn't thinking about damage during ascent. I was thinking more of the damage to the capsule while it is docked to the ISS (which is for a six month period). But you are right that the SM or trunk would protect the heatshield to a certain extent. Thanks.
« Last Edit: 09/10/2015 02:54 PM by yg1968 »

Offline Comga

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #43 on: 09/11/2015 03:20 PM »
The MMOD thing for CC is very odd. Surely this must be an overly conservative estimate or ISS, Mir, Skylab, or the various Salyuts would've no doubt been punctured in their pressurized sections by now (considering they've been nearly permanently in orbit since the early 1970s). Even Shuttle didn't receive a fatal strike to its enormous heat shield from MMOD.

models have been updated based on more data and a lot, LOT more debris.  Recall ISS is now flying lower to mitigate risk of MMOD.  Yes, the capsule heat shields are protected but they are going to be up there for 6 months with their butts into the debris wind so to speak for Node 2 forward.  A lot can happen.

(emphasis mine)
At the risk of going off topic, the ISS originally orbited around 390 km, dropped back as low as ~330 km, and then went up to ~440 km when the Shuttle retired.  It has now sunk to just over 400 km.  Is it trying to keep a constant drag/density to balance the MMOD risk with reboost fuel usage?

Back on topic, do we have a numerical breakdown of the 1/270 LOC number into its components? 
Saying that MMOD is the third biggest risk without quantifying them is like saying that Three Mile Island is the third worst nuclear plant release while ignoring the many orders of magnitude between it and Chernobyl. 
« Last Edit: 09/11/2015 03:20 PM by Comga »
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Online mtakala24


At the risk of going off topic, the ISS originally orbited around 390 km, dropped back as low as ~330 km, and then went up to ~440 km when the Shuttle retired.  It has now sunk to just over 400 km.  Is it trying to keep a constant drag/density to balance the MMOD risk with reboost fuel usage?

Discussed here: http://forum.nasaspaceflight.com/index.php?topic=37234.0
edit: and here: http://forum.nasaspaceflight.com/index.php?topic=36322.0
« Last Edit: 09/11/2015 05:53 PM by mtakala24 »

Offline vt_hokie

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #45 on: 09/14/2015 06:26 PM »
I'm surprised I haven't seen more mention of Soyuz in the reliability and safety discussions, given that it has set the benchmark for human spaceflight over several decades. Does anyone happen to know what its estimated LOC probability is?

Offline erioladastra

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #46 on: 09/17/2015 01:06 AM »
The discussion about safety has me wondering. Will commercial crew have some kind of flip maneuver or other visual inspection to see if the heatshield of the capsule is fit for reentry (i.e. that there hasn't been any micrometeorite damage to its heatshield during its stay at the ISS)?

NASA is looking into various inspection options.  as noted elsewhere the heat shields are protected so can't do that and a flip doesn't get you much (before docking risk is near zero, after undocking you don't have time to analyze the photos, could only eyeball a huge hit).  Probably will be some combo of SSRMS and hope.

Offline yg1968

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #47 on: 09/17/2015 06:09 PM »
Thanks! The ASAP also made some interesting comments on this topic. See this post in a different thread:

http://forum.nasaspaceflight.com/index.php?topic=35717.msg1424626#msg1424626
« Last Edit: 09/17/2015 06:10 PM by yg1968 »

Offline MP99

The discussion about safety has me wondering. Will commercial crew have some kind of flip maneuver or other visual inspection to see if the heatshield of the capsule is fit for reentry (i.e. that there hasn't been any micrometeorite damage to its heatshield during its stay at the ISS)?

The heat shields won't be visible, they're protected by the trunk/ SM so MMOD damage/ damage on ascent isn't a concern like it was for the orbiters who had an exposed TPS

CST-100 looks OK with the SM protecting until reentry.

Dragon could have cameras in the trunk to perform checks. Or a shield if no unpressurized cargo.

Cheers, Martin

Online guckyfan

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #49 on: 09/19/2015 12:57 PM »
CST-100 looks OK with the SM protecting until reentry.

Dragon could have cameras in the trunk to perform checks. Or a shield if no unpressurized cargo.

Dragon has Kevlar shields inside the trunk. It does protect the heat shield.

Edit: The cargo Dragon has. No doubt the Crew Dragon will have it too.

« Last Edit: 09/19/2015 12:58 PM by guckyfan »

Offline MP99

Many thanks for that.

Cheers, Martin

Offline the_other_Doug

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #51 on: 09/20/2015 03:31 AM »
I will also note that the Russians, and before as the Soviets, have been keeping Soyuz on-station in LEO for up to six months at a time for, well, more than 30 years, going back to Salyut 6.  They haven't lost any of them, not one of the dozens upon dozens, to TPS damage.  And they have nothing more or less than Starliner or Dragon will have, a module covering the main TPS.

None have ever been holed by MMOD to the extent they lost pressure or critical systems, either.

Shuttle was different because its TPS was always fully exposed to MMOD, and it had a far more fragile TPS than Dragon or Starliner will.  The Shuttle-style TPS inspections will not be needful for the new commercial crew vehicles.
-Doug  (With my shield, not yet upon it)

Online guckyfan

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #52 on: 09/20/2015 08:37 AM »
I will also note that the Russians, and before as the Soviets, have been keeping Soyuz on-station in LEO for up to six months at a time for, well, more than 30 years, going back to Salyut 6.  They haven't lost any of them, not one of the dozens upon dozens, to TPS damage.  And they have nothing more or less than Starliner or Dragon will have, a module covering the main TPS.

None have ever been holed by MMOD to the extent they lost pressure or critical systems, either.

My thougts as well. It is a concern of NASA but I don't understand where that concern comes from.

Shuttle was different because its TPS was always fully exposed to MMOD, and it had a far more fragile TPS than Dragon or Starliner will.  The Shuttle-style TPS inspections will not be needful for the new commercial crew vehicles.

If I remember correctly the TPS inspections were introduced because of possible damage on start, not because of possible MMOD. It would cover MMOD as well though. While the SpaceShuttle heat shield would be exposed for a much shorter time it is much shorter and probably more sensitive.


Offline MP99



I will also note that the Russians, and before as the Soviets, have been keeping Soyuz on-station in LEO for up to six months at a time for, well, more than 30 years, going back to Salyut 6.  They haven't lost any of them, not one of the dozens upon dozens, to TPS damage.  And they have nothing more or less than Starliner or Dragon will have, a module covering the main TPS.

None have ever been holed by MMOD to the extent they lost pressure or critical systems, either.

My thougts as well. It is a concern of NASA but I don't understand where that concern comes from.

To achieve an overall 1:270, the chance of any individual failure must be lower than that. Even 1:1000 would be a large contribution.

What is the confidence level that the evidence listed translates to 1:1000 or better?

Cheers, Martin

Offline the_other_Doug

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #54 on: 09/20/2015 03:23 PM »
If I remember correctly the TPS inspections were introduced because of possible damage on start, not because of possible MMOD. It would cover MMOD as well though. While the SpaceShuttle heat shield would be exposed for a much shorter time it is much shorter and probably more sensitive.

Actually, we're both right.  On post-Columbia missions, there were two full TPS inspections using the RMS boom extension.  The first happened during the transfer orbits prior to rendezvous with the ISS, and that one checked for launch damage.  The second was done after the Shuttle undocked from ISS and separated, and that one was to look for MMOD.
-Doug  (With my shield, not yet upon it)

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