Author Topic: ASAP still has concerns over Commercial Crew LOC risks  (Read 10661 times)

Offline the_other_Doug

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #40 on: 09/05/2017 04:36 PM »
I think both the Star liner and Dragon beat Soyuz by having less separation events and three parachutes.

Actually, Crew Dragon will have four parachutes.  But Apollo 15 did teach the lesson of having a one-chute-out safety margin... :)
-Doug  (With my shield, not yet upon it)

Offline ChrisWilson68

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #41 on: 09/30/2017 02:12 AM »
I think both the Star liner and Dragon beat Soyuz by having less separation events and three parachutes.

Though a crewed version of Dream Chaser in theory should beat both of them as far as landing safety goes.

That was one one part of STS that actually had a good safety record.

I disagree.  To land on a runway you give up being able to do ballistic re-entry.  Star liner and Dragon can lose all active control and go balistic and they'll come down fine.  All they need is the parachutes to pop open in a single event.  Space planes need control surfaces and active control all the way down.  It's much more complexity, which means more things that can go wrong.

Dragon is the safest in concept because it has a backup for the parachutes -- it can fire its Super Dracos if the parachutes don't open for some reason.

Online rayleighscatter

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #42 on: 09/30/2017 09:50 PM »
Capsules can lose active control if they're already on the correct reentry path. Otherwise it will orbit forever, reenter too steep, or skip and then reenter too steep.

Offline Nibb31

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #43 on: 09/30/2017 09:56 PM »
Capsules can lose active control if they're already on the correct reentry path. Otherwise it will orbit forever, reenter too steep, or skip and then reenter too steep.

That is true for any reentry vehicle regardless of shape.

Offline wilbobaggins

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #44 on: 11/07/2017 06:16 AM »
I think both the Star liner and Dragon beat Soyuz by having less separation events and three parachutes.

Though a crewed version of Dream Chaser in theory should beat both of them as far as landing safety goes.

That was one one part of STS that actually had a good safety record.

I disagree.  To land on a runway you give up being able to do ballistic re-entry.  Star liner and Dragon can lose all active control and go balistic and they'll come down fine.  All they need is the parachutes to pop open in a single event.  Space planes need control surfaces and active control all the way down.  It's much more complexity, which means more things that can go wrong.

Dragon is the safest in concept because it has a backup for the parachutes -- it can fire its Super Dracos if the parachutes don't open for some reason.
I really hope they have added the software to do this. Just as CRS-7 dragon was lost due to lack of software to pop off nose cone it would be crap to loose a crew because parashutes failed despite having enough hydrazene in the tank for a landing.

Yes they have given up propulsive landing but only I think to the safety standard to do it every time. At the point of total parashutes failure who gives a darn what the chance of a safe propulsive landing is, it is their only hope!

Then again the chance of it firing when the parashutes are fine and shredding parashutes should be considered.


« Last Edit: 11/17/2017 11:09 AM by Chris Bergin »

Offline Space Ghost 1962

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #45 on: 11/12/2017 05:40 PM »
FWIW, to increase mission LOC/LOM now ... fly mission. Analyze. Rework. Fly again.

Why this doesn't happen ... IMO ... too much works too well ... the flights are cheaper/quicker than a certain bigger capsule ... CC converges on provable safety limits ... there then is pressure to actually fly crews.

Once crews start flying on CC, then there's pressure on the bigger capsule to do same. But it can't for cost/reasons, so everyone gets used to CC flying crew and the bigger capsule not flying crew.

This ends up not helping the big capsule, even though it should (a means to prove elements of big capsule with crew).

Because Congress doesn't want CC to follow Soyuz, they want the "big capsule" to. And, they can always blame CC for not flying, because "its too unsafe". Circular.

add:

What if CRS finds booster reuse is effective and accepts for flights? Then likewise CC might arrive at the same conclusion. NASA might be able to do a "block buy" and get perhaps 20-30 CRS/CC flights for every big capsule flight.

How might 20-30 CRS/CC flights ... benefit LOC/LOM assessment/improvement? How much of this could also feed back into big capsule refinement? Might even improve Soyuz.
« Last Edit: 11/12/2017 05:46 PM by Space Ghost 1962 »

Online rayleighscatter

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #46 on: 11/12/2017 08:14 PM »

NASA might be able to do a "block buy" and get perhaps 20-30 CRS/CC flights for every big capsule flight.

What mission requires 30 CRS flights?

As upset as everyone gets for trying to invent missions for Orion then there's obviously no need to do it for CC either.

Offline Space Ghost 1962

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #47 on: 11/12/2017 08:56 PM »

NASA might be able to do a "block buy" and get perhaps 20-30 CRS/CC flights for every big capsule flight.

What mission requires 30 CRS flights?

As upset as everyone gets for trying to invent missions for Orion then there's obviously no need to do it for CC either.
Missed the point. And its CRS/CC flights, because the same configuration could be used for both. Duh.

The point is that actual, repeated flight data of vehicle gives you bounds/reasons/means for safety improvement.

Not static, ground determined analysis. Sorry if I was unclear.

Edited by Lar.
« Last Edit: 11/14/2017 10:04 AM by Lar »

Offline A_M_Swallow

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #48 on: 11/12/2017 09:01 PM »

NASA might be able to do a "block buy" and get perhaps 20-30 CRS/CC flights for every big capsule flight.

What mission requires 30 CRS flights?

As upset as everyone gets for trying to invent missions for Orion then there's obviously no need to do it for CC either.

30 CRS flights would support multiple Moon landings. Using 5 tonne payloads it will take a while to construct a lunar base. At 40 tonnes payload to the Moon entire buildings can be delivered in one go.

Offline woods170

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #49 on: 11/13/2017 07:13 AM »

NASA might be able to do a "block buy" and get perhaps 20-30 CRS/CC flights for every big capsule flight.

What mission requires 30 CRS flights?

As upset as everyone gets for trying to invent missions for Orion then there's obviously no need to do it for CC either.
Missed the point. And its CRS/CC flights, because the same configuration could be used for both. Duh.

The point is that actual, repeated flight data of vehicle gives you bounds/reasons/means for safety improvement.

Not static, ground determined analysis. Perhaps I need to resort to purple crayon to get my point across?  ::)
Your point is clear. Two little flaws though:
- There won't be 30 missions to inform crew safety, not even when you add Cargo Dragon v2 missions into the mix.
- Purely commercial, non-NASA missions, such as the planned circumlunar mission, do not inform crew safety because NASA insight into those will be almost non-existent.

Right now the CRS/CCP providers need NASA to survive. As such they are willing to put up with the additional crew-safety burden that NASA places on them. But IMO there will come a time when at least one of those providers no longer needs NASA to achieve its goals. When that time comes it will shed NASA and its associated burdensome bureaucracy. Regardless of its his current habit of praising NASA.
« Last Edit: 11/13/2017 07:14 AM by woods170 »

Offline pathfinder_01

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #50 on: 11/13/2017 07:50 AM »


Because Congress doesn't want CC to follow Soyuz, they want the "big capsule" to. And, they can always blame CC for not flying, because "its too unsafe". Circular.

add:

What if CRS finds booster reuse is effective and accepts for flights? Then likewise CC might arrive at the same conclusion. NASA might be able to do a "block buy" and get perhaps 20-30 CRS/CC flights for every big capsule flight.

How might 20-30 CRS/CC flights ... benefit LOC/LOM assessment/improvement? How much of this could also feed back into big capsule refinement? Might even improve Soyuz.

1.  This isn't a Congress problem. Congress wants SLS because it creates the most jobs. Orion less so. Therefore Orion development takes a back seat to SLS development. It isn't like Apollo and the early space race where no new rockets were developed specifically for Mercury and Gemini(as that would only delay things) and Apollo used the Saturn 1B(which was an upgrade of an existing rocket) for a number of test flights. This is an ASAP problem. If they were interested in improving the safety of Orion they could always fly some of them on Delta IV heavy but that would require development which would take even more budget(or reduce budget to SLS, therefore delay is the better Option).

2.  There would only be limited data from Commercial Crew that would be relevant to Orion or Soyuz as one system was in development before commercial crew and the other was operational long before. The Russians already have a much more relevant data set for Soyuz and it' successors.

3. As much as I would love a block buy of 20-30 flight this isn't a good reason.  20-30 flights would improve Dragon 2 and Starliner by finding the problems that only experience could sort out. They say little to nothing about Orion.
« Last Edit: 11/13/2017 07:56 AM by pathfinder_01 »

Offline Space Ghost 1962

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Re: ASAP still has concerns over Commercial Crew LOC risks
« Reply #51 on: 11/13/2017 09:59 PM »
NASA might be able to do a "block buy" and get perhaps 20-30 CRS/CC flights for every big capsule flight.
What mission requires 30 CRS flights?
The point is that actual, repeated flight data of vehicle gives you bounds/reasons/means for safety improvement.
Your point is clear. Two little flaws though:
- There won't be 30 missions to inform crew safety, not even when you add Cargo Dragon v2 missions into the mix.
- Purely commercial, non-NASA missions, such as the planned circumlunar mission, do not inform crew safety because NASA insight into those will be almost non-existent.
1. Builds on my point. We think of such vehicles as a limiting cost and so minimize to fewest use. Which caps are ability to reach ASAP's desired LOC. Past LV reuse, things get safer/cheap in net when we get to a fair fraction of 100. SX likely to reach hundreds of missions off of reuse, so we're likely to reach comparative numbers to Shuttle.
2. AF contracts require all launches to "inform" on LV performance. A similar means to inform on crew safety under appropriate convention (possible in US but not Europe given certain laws) could supply such, part of adventurer contract of carriage.

Am quite serious about means to achieve best provable crew vehicle LOC. Which is potentially transferable to other vehicles.

Quote
Right now the CRS/CCP providers need NASA to survive. As such they are willing to put up with the additional crew-safety burden that NASA places on them. But IMO there will come a time when at least one of those providers no longer needs NASA to achieve its goals. When that time comes it will shed NASA and its associated burdensome bureaucracy. Regardless of its his current habit of praising NASA.
Yes we are both looking at the same thing. Beyond NASA. Where its just an occasional client.

BTW, there are many "NASA's" inside of NASA. True of other agencies/ministries. Some see this too.

Difference might be about where and how to achieve said "pivot". Perhaps as temporary conservator? Thus the above.

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