Author Topic: NASA evaluating CCP Loss Of Crew and Mishap procedures  (Read 19844 times)

Offline Coastal Ron

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #20 on: 06/01/2015 04:41 AM »
...And let's not forget that CST-100 will also be lifted by two powerful solid motors during the first 90 seconds of flight, which have some of the same failure modes present in SRBs.

My assumption is that no transportation system will be perfect, and certainly the far more mature mass transit systems we have today are not perfect either.

Which is why I suggested that each new system should be compared to the last, not some made up number.  And if they are more safe then that's good.  CST-100 on Atlas V sure looks more inherently safe than the Shuttle.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Online Jarnis

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #21 on: 06/01/2015 04:59 AM »
... the Shuttle showed that even though it had fatal flaws, like no realistic way to survive an inflight failure ...
Only a catastrophic failure of an SRB during the first two minutes of flight presented this hazard.  Everything else to my knowledge had an abort mode or modes to provide a means of crew survival.  One orbiter actually did an abort-to-orbit when it lost an SSME.

Well, some of those abort modes had asterisks to footnotes with something like "* requires a metric ton of good luck and some acts of god". Also before Challenger any abort mode that did not land on a runway was... umm... unlikely to result in a happy ending. Those scenarios did get better once pressure suits and bailout procedures were added.

Offline woods170

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #22 on: 06/01/2015 08:54 AM »
... the Shuttle showed that even though it had fatal flaws, like no realistic way to survive an inflight failure ...
Only a catastrophic failure of an SRB during the first two minutes of flight presented this hazard.  Everything else to my knowledge had an abort mode or modes to provide a means of crew survival.  One orbiter actually did an abort-to-orbit when it lost an SSME.

Well, some of those abort modes had asterisks to footnotes with something like "* requires a metric ton of good luck and some acts of god". Also before Challenger any abort mode that did not land on a runway was... umm... unlikely to result in a happy ending. Those scenarios did get better once pressure suits and bailout procedures were added.

Emphasis mine.
Notably, the Return To Lauch Site abort mode (RTLS)

Offline muomega0

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #23 on: 06/01/2015 10:59 AM »
...And let's not forget that CST-100 will also be lifted by two powerful solid motors during the first 90 seconds of flight, which have some of the same failure modes present in SRBs.

My assumption is that no transportation system will be perfect, and certainly the far more mature mass transit systems we have today are not perfect either.

Which is why I suggested that each new system should be compared to the last, not some made up number.  And if they are more safe then that's good.  CST-100 on Atlas V sure looks more inherently safe than the Shuttle.
The capsule is on top, has an abort system and parachutes (which do not like solids), but will be certified on a LV configuration that will be retired and replaced by another LV that uses solids in non common configurations.  So would CST-100 or Orion or Dragon look inherently safer on Atlas V or other LVs?  Does actual flight rate and number of flights in a common configuration matter?  Is ascent/reentry an actual driver in LOC?

So what I would propose is a system that simply determines if a new system is potentially more safe than the previous system, and then make sure to quantify what the dangers still are (both known and and potential) such as MMOD.

For instance, what if the crew is in the vehicle on the launch pad and something goes wrong, is there a system that can get them to safety?  ...    And going forward as more transportation systems get added the free market forces will guide what levels of safety are acceptable.
LOC during ascent represents just a few percent of the total--while the addition of an abort system without solids should improve safety, the likelihood of it being used is very small.  A common configuration for cargo and crew provides likely pays much larger dividends since the unknown failure mode has a chance to happen on the cargo flight.

As far as MMOD and total LOC, for missions to the Moon, L2, or elsewhere, the risk will need to be assessed for time period spacecraft resides mainly in 'LEO'.  For ISS, 'debris' represents approximately 2/3rds of the MMOD risk.  The meteroid risk far from Earth is generally less than the risk in LEO.  So why stage *mission* hardware in LEO?

The best way to improve safety is to shift funds to the main safety drivers.  The only way to reduce launch costs is to provide a stable number of government launches..adding more providers will not help--the providers need more payloads.   Funding LV capacity to meet demand would benefit budgets too.

Stage the propellant (70%+ of the per mission mass) in a LEO depot designed to survive MMOD to reduce launch costs by providing 'commercial' payload instead of having the LVs sit idle.  Take risks with dirt cheap propellant delivery in a *common* configuration.  Stage all the transient mission hardware at L2 and minimize its stay in LEO. Have multiple tugs.

The US however will spend the next decade certifying LVs and multiple capsules for government missions and not spend cash on the things that make up the other 90+ percent of LOC.   'Commercial' may also create "voluntary consensus standards" but it appears they need a law to do this voluntarily and to reach a consensus (is re-use more safe than expendable? land vs water landing?).  Are not costs and safety conflicting requirements?

Offline Jim

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #24 on: 06/01/2015 01:07 PM »
NASA learnt to give the Space Shuttle a hull inspection before it docked to the ISS. Will the Commercial Crew vehicles be required to undergo a similar inspection?


No, that was a shuttle unique

Offline Ben the Space Brit

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #25 on: 06/01/2015 02:14 PM »
To me, the obvious first step is to have at least one level of failure tolerance allowing ATES (Abort to Earth Surface) for all critical systems where this is practical.

For example, there has yet to be a spacecraft designed with a redundant re-entry TPS. However, some kind of lamination of view-ports to increase their resistance to MMOD and redundant flight controls are an obvious step.

Both the CCP finalists are heavily-automated with touch-screen controls. I was glad to see that SpaceX had installed alternate physical controls (including, hopefully, at least one redundant control data path) in Dragon v.2. This is the sort of thinking that shows the contractors are taking potential faults and maximising crew survivability seriously.
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Offline MattMason

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #26 on: 06/01/2015 02:36 PM »
To me, the obvious first step is to have at least one level of failure tolerance allowing ATES (Abort to Earth Surface) for all critical systems where this is practical.

For example, there has yet to be a spacecraft designed with a redundant re-entry TPS. However, some kind of lamination of view-ports to increase their resistance to MMOD and redundant flight controls are an obvious step.

Both the CCP finalists are heavily-automated with touch-screen controls. I was glad to see that SpaceX had installed alternate physical controls (including, hopefully, at least one redundant control data path) in Dragon v.2. This is the sort of thinking that shows the contractors are taking potential faults and maximising crew survivability seriously.

I was thinking that, too. Physical switches and redundant and independent controls that still allow vehicle control if that central panel has a failure is important. It's actually one of the design elements of Crew Dragon that give me the willies.
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Offline guckyfan

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #27 on: 06/01/2015 03:48 PM »
I remember a very old comment about the parachutes of Dragon. It was said, they have a fully manual release mechanism as backup. Dragon can reenter on pure aerodynamic stability without any control though the g-forces would be much harsher than on a controlled entry. If this is still true and why would it not, then from the moment after reentry burn they can lose electronics completely and still get the crew safely to the ground.

Online Hog

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #28 on: 06/01/2015 05:08 PM »
NASA learnt to give the Space Shuttle a hull inspection before it docked to the ISS. Will the Commercial Crew vehicles be required to undergo a similar inspection?

We may be able to patch a hole at the ISS. We can certainly launch a replacement vehicle.
Commercial Crew TPS isn't exposed during launch like STS was.  Shuttle vs. capsule.

Good.

The primary TPS across the underneath of the capsules is covered but the side walls, top and windows are exposed permitting MMOD.
Referring to the inspection Shuttle performed before it docked to ISS.  While I'm sure that MMOD(Micrometeroid and Orbital Debris) was a small factor for the RPM and the OBSS inspections(using its 4 sensor systems), these were largely done to mitigate the TPS damage risk caused by launch debris, being sidemount to the ET.

The risk of a MMOD strike between launch and docking is smaller, due to the time period being shorter. Of course the risk is greater when referring to the entire orbital mission.
Paul

Offline baldusi

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #29 on: 06/01/2015 05:49 PM »
[..]
And let's not forget that CST-100 will also be lifted by two powerful solid motors during the first 90 seconds of flight, which have some of the same failure modes present in SRBs.
Consider the weight of the stack at SRB separation and you'll note that without the RD-180 the T/W will never go above 1.6. And the two SRB are not on the same plane, so the capsule can sort of safely turn on the other side. Note that for Balance reasons the Shuttle was closer to the SSRB than the mid plane. So while it does introduces a slight complication (nothing like all liquid in this regard). The degree of danger is much less.

Offline erioladastra

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #30 on: 06/03/2015 12:44 AM »
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.

Offline erioladastra

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #31 on: 06/03/2015 12:46 AM »
Does anyone think they may move up the time frame for the commercial crews due to recent events with the Russian failures?

Very desirable but won't happen.  While 2 companies is great for redundancy it slows things down (spreads the money out and ties up the NASA resources), the money does not appear to be coming as needed for this (and as predicted), the companies are scrambling as hard as they can and they will be very hard pressed to make 2017 as it is.  Not going to be able to reduce the time unless a LOT more $$$$ comes now.

Online RonM

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #32 on: 06/03/2015 01:09 AM »
Does anyone think they may move up the time frame for the commercial crews due to recent events with the Russian failures?

Very desirable but won't happen.  While 2 companies is great for redundancy it slows things down (spreads the money out and ties up the NASA resources), the money does not appear to be coming as needed for this (and as predicted), the companies are scrambling as hard as they can and they will be very hard pressed to make 2017 as it is.  Not going to be able to reduce the time unless a LOT more $$$$ comes now.

I agree. CC could have been sooner if Congress had fully funded the project from the start. More resources could have shorten the development time. Now it is too late to throw money at it.

Offline newpylong

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #33 on: 06/04/2015 02:17 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.

It isn't odd at all. Space Stations don't have to reenter.

Offline Sesquipedalian

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #34 on: 06/04/2015 04:38 PM »
On the subject of MMOD...

Discovery suffered a MMOD strike on STS-128 which would have led to Loss of Mission (land within 24 hours) if not for modifications and hardening in the late 1990s:
http://research.jsc.nasa.gov/BiennialResearchReport/2011/265-2011-Biennial.pdf

A pretty good overview of ISS MMOD considerations (109 slides):
https://tfaws.nasa.gov/files/MMOD_Course_TFAWS_2014.pdf

Offline psloss

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #35 on: 06/04/2015 07:50 PM »
Discovery suffered a MMOD strike on STS-128 which would have led to Loss of Mission (land within 24 hours) if not for modifications and hardening in the late 1990s:
http://research.jsc.nasa.gov/BiennialResearchReport/2011/265-2011-Biennial.pdf
Nice find, thanks for posting it.  This reference also notes when the Shuttle program instituted that change in flying attitudes for MMOD protection: after STS-50 in 1992, or about a third of the way into the flight history:
Quote
After STS-50, new flight rules were implemented that required the shuttle to fly with the payload bay to the Earth and the tail toward the velocity vector "unless payload or orbiter requirements dictate otherwise."

And there it is in the flight rules: "A2-131 ATTITUDE RESTRICTIONS FOR ORBITAL DEBRIS."  (L2 has one or two revisions; public reference to generic flight rules, PDF circa STS-107.)
« Last Edit: 06/04/2015 07:55 PM by psloss »

Offline DAZ

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #36 on: 06/07/2015 11:32 PM »
Some years ago I read an Air Force safety report on the use of solid rocket motors on launch vehicles.  The report came out after all the Shuttle, Delta, and Titan accidents.  I wish I could find the report again but I have had no luck.  The report read like unsafe at any cost.  The report did not come right out and say this as it was trying to be PC but any engineer reading it would have under stood what they were saying.

From memory.

The first part of the report was about economics of using solid rocket motors.  The report indicated that it was cheaper at first to build a LV using SRBs but that the recurring costs for SRBs and there safe use would at some point exceed the cost of just building an all liquid LV.  This number could be 5, 10 or 20 but at some point depending on your safety requirements it would happen.  It could be as low as 1 if the cost/uniqueness of the payload was high enough.  This was for expendable LV system.  I can’t see that this get better for reusable system as it has to do with the catastrophic modes of failures for solid rocket motors.  Pick your cost numbers to get your system.  It is only money for the most part.

Some things made the system much less safe and upped the costs.  More SRBs, larger, more segments and the big one composite cases.  The way to mitigate was more margins, safer handling (kid gloves) and lots and lots and lots of inspection with their entailed paper work.  You could never drive the safety to the same level as liquid boosters, just to a level that would match your cost to risk goals.

Next the report talked about the use of SRBs for manned system.  On this the report said NO.  There was no way to make a manned system safe at any cost if it used SRBs.  Unlike an all liquid LV that you could build a LAS to save the crew when you use SRBs it is not possible.  The report distinguished between possible but not economical and not possible.  Any LAS to escape from all the possible catastrophic modes of failures for solid rocket motors would result in the crew being used as red paint on the floor of the crew vehicle thus defeating the reason for a LAS.

This is what the Air Force was practically jumping up and down about saying that the Ares 1 was unsafe and that the NASA LAS would not work for a system with SRBs.  For something like the “Black Knights” on the SLS the question becomes not if but will the system have enough lunches to lose a crew.

If you believe the Air Force safety report (and the report looked correct to me) then the only crewed lunch system that looks to be reasonably safe is the SpaceX system.  Not because they are somehow better or have better safer systems but it is the only one without solid rocket motors.  Not looking at this is just looking the other way for expediency like on the Space Shuttle, not out of necessity.

Online Jarnis

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #37 on: 06/08/2015 06:16 AM »
Well, Senate Launch System can still be a fine (if expensive) heavy lift vehicle. Just ditch the LAS (more room for cargo!) and deliver the crew to on-orbit Orion using a safe and cheap commercial crew vehicle.

Doubt it will happen, but...

Online Zed_Noir

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #38 on: 06/08/2015 10:53 AM »
Well, Senate Launch System can still be a fine (if expensive) heavy lift vehicle. Just ditch the LAS (more room for cargo!) and deliver the crew to on-orbit Orion using a safe and cheap commercial crew vehicle.

Doubt it will happen, but...

If you use a commercial crew vehicle anyway, you don't need the Orion since some sort of hab module will be required for any mission beyond the Moon. IIRC the Orion got enough life support for about 21 days. Just use the commercial crew vehicles as taxis between the Earth surface and a long mission duration spacecraft.

Online Jarnis

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Re: NASA evaluating CCP Loss Of Crew and Mishap procedures
« Reply #39 on: 06/08/2015 01:22 PM »
Supposedly Orion has all these BEO things modded in (comms, radiation shielding, electronics) which mere commercial crew vehicles do not have.

Of course you could have all those things in the hab module and keep the commercial crew vehicle powered down until it is again needed for re-entry.

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