Author Topic: Commercial Crew (CCtCAP) - Discussion Thread  (Read 258993 times)

Online Chris Bergin

Follow on thread to the massive discussion through to the revealing of the CCtCAP winners:
http://forum.nasaspaceflight.com/index.php?topic=28699.0

Resources:

Commercial Crew News:
http://www.nasaspaceflight.com/tag/ccdev/ <--covers through to CCtCAP

L2 Commercial Crew:
http://forum.nasaspaceflight.com/index.php?board=54.0

L2 SpaceX - Covering Dragon:
http://forum.nasaspaceflight.com/index.php?board=60.0

Offline clongton

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #1 on: 09/24/2014 11:40 PM »
Thanks Chris. This is a whole new world :)
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I started my career on the Saturn-V F-1A engine

Offline Darkseraph

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #2 on: 09/25/2014 03:39 PM »
Should we worry about those seawater intrusions that have bugged the Dragon V1 on some landings? Doesn't sound good...:/ How is it even getting in?
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." R.P.Feynman

Offline kevinof

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #3 on: 09/25/2014 03:50 PM »
Why worry. Crewed Dragon won't land on water.

Should we worry about those seawater intrusions that have bugged the Dragon V1 on some landings? Doesn't sound good...:/ How is it even getting in?

Offline nadreck

Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #4 on: 09/25/2014 04:02 PM »
Why worry. Crewed Dragon won't land on water.

Should we worry about those seawater intrusions that have bugged the Dragon V1 on some landings? Doesn't sound good...:/ How is it even getting in?

It must be certified to be able to land in water. Also, in the most extreme possible launch conditions (ie the abort). As well any return from orbit that has to take place on an emergency basis the likely hood is a water landing.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline kevinof

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #5 on: 09/25/2014 04:15 PM »
True but in an emergency are you going to worry about a little water ingress? It hasn't caused any major problems for Space X yet and for all we know they may have already fixed the problem.


Why worry. Crewed Dragon won't land on water.

Should we worry about those seawater intrusions that have bugged the Dragon V1 on some landings? Doesn't sound good...:/ How is it even getting in?

It must be certified to be able to land in water. Also, in the most extreme possible launch conditions (ie the abort). As well any return from orbit that has to take place on an emergency basis the likely hood is a water landing.

Online Mongo62

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #6 on: 09/25/2014 04:42 PM »
Should we worry about those seawater intrusions that have bugged the Dragon V1 on some landings? Doesn't sound good...:/ How is it even getting in?

The water ingress would not be into the pressure vessel itself, for obvious reasons, so it must be either into volumes that are exposed to vacuum in orbit, lying between the pressure vessel and the outer casing, or into empty tanks with an open path between them and the water.

The designers would surely have known about the first case and allowed for it, so it must be the second case. One possible path for water to enter would be through a Draco rocket nozzle, past an open or partly open injector and valve and into one of the hypergolic propellant tanks.

If it had only happened once, I would think that it was an error in procedures where somebody forgot to close the valve after the tank emptied, but since it appears to have happened several times, I'm guessing that it might be a design or manufacturing flaw with the valves, where they do not fully close as commanded when there is significant water pressure on the downstream side of the valve.
« Last Edit: 09/25/2014 04:44 PM by Mongo62 »

Offline erioladastra

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #7 on: 09/25/2014 05:46 PM »
Should we worry about those seawater intrusions that have bugged the Dragon V1 on some landings? Doesn't sound good...:/ How is it even getting in?

The water ingress would not be into the pressure vessel itself, for obvious reasons, so it must be either into volumes that are exposed to vacuum in orbit, lying between the pressure vessel and the outer casing, or into empty tanks with an open path between them and the water.

The designers would surely have known about the first case and allowed for it, so it must be the second case. One possible path for water to enter would be through a Draco rocket nozzle, past an open or partly open injector and valve and into one of the hypergolic propellant tanks.

If it had only happened once, I would think that it was an error in procedures where somebody forgot to close the valve after the tank emptied, but since it appears to have happened several times, I'm guessing that it might be a design or manufacturing flaw with the valves, where they do not fully close as commanded when there is significant water pressure on the downstream side of the valve.

All incorrect.  Water was in the pressurized cargo area.  Yes, there should be concern

Online rcoppola

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #8 on: 09/25/2014 05:57 PM »
Hans recently mentioned that they moved a few "Components" from the internal pressure vessel to the exterior volume occupied by the tanks and Draco engines. This reference was for the cargo Dragon but I imagine similar and more intense efforts are underway for DV2 as well. (As well as potential additional valve redundancies and valve reengineering.)
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Online Mongo62

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #9 on: 09/25/2014 09:49 PM »
I'm guessing that it might be a design or manufacturing flaw with the valves, where they do not fully close as commanded when there is significant water pressure on the downstream side of the valve.

All incorrect.  Water was in the pressurized cargo area.  Yes, there should be concern

If water did not get in through malfunctioning valves, how did it get there? It's a sealed vessel, designed to hold pressure against a vacuum. I repeat that the only mechanism I can think of is water getting past a valve.
« Last Edit: 09/25/2014 09:50 PM by Mongo62 »

Online QuantumG

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #10 on: 09/25/2014 09:54 PM »
They're called "cracks". Slamming an object into the ocean at high speeds tends to make them.

Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline BrianNH

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #11 on: 09/25/2014 10:00 PM »
The advantage of launching unmanned versions of the vessel years in advance of a manned launch is that you can find the problems that you didn't anticipate and fix them.

Offline erioladastra

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #12 on: 09/26/2014 01:11 AM »
They're called "cracks". Slamming an object into the ocean at high speeds tends to make them.



nope, not cracks.  But I am not at liberty to say.  keen eyed folks might figure out near the end of the current flight.

Online TrevorMonty

Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #13 on: 09/26/2014 02:14 AM »
They're called "cracks". Slamming an object into the ocean at high speeds tends to make them.



nope, not cracks.  But I am not at liberty to say.  keen eyed folks might figure out near the end of the current flight.
In a vacuum any seals are designed for the interior to be at a positive pressure. When it hits the water the interior is at a negative pressure compared to water.

 Designing seals to handle opposite pressure differences is not easy.

Offline Garrett

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #14 on: 09/26/2014 10:06 AM »
They're called "cracks". Slamming an object into the ocean at high speeds tends to make them.
nope, not cracks.  But I am not at liberty to say.  keen eyed folks might figure out near the end of the current flight.
It has been mentioned a few times (on this forum and elsewhere) about pressure equalization valves being opened on purpose when Dragon splashes down, resulting in a short period of seawater incursion:
https://www.google.fr/search?q=spacex+pressure+equalization+valve
« Last Edit: 09/26/2014 10:06 AM by Garrett »
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Offline baldusi

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #15 on: 09/26/2014 03:45 PM »
Those valves and the fact that last time due to rough seas, the capsule was towed to port. So it had waves and the water had the pressure generated by the tow. Nothing like what would happen to a crewed flight.

Offline erioladastra

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #16 on: 09/26/2014 05:15 PM »
Those valves and the fact that last time due to rough seas, the capsule was towed to port. So it had waves and the water had the pressure generated by the tow. Nothing like what would happen to a crewed flight.

Not valves but related to towing.

Online deruch

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #17 on: 09/29/2014 02:09 PM »
Should we worry about those seawater intrusions that have bugged the Dragon V1 on some landings? Doesn't sound good...:/ How is it even getting in?

How much water are we talking about in total (by volume)?  Has there ever been any definitive statements on that?  As troubling as it may be from an engineering/manufacturing perspective, given the fact that the capsule was floating for 11 hours I'm not too concerned from a human safety perspective.  At least not in respect to the dangers directly posed by sea water intrusions.  What they may mean indirectly will depend on their cause.
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline Kabloona

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #18 on: 09/30/2014 10:14 PM »
Commentary by Rand Simberg on the Commercial Crew selections. I did not see this posted anywhere on NSF but beg indulgence if it's already been posted somewhere:

Good analysis of Boeing and SpaceX's situations and some mention of the SNC controversy:

http://www.nationalreview.com/corner/388477/boeing-isnt-getting-more-nasa-money-because-its-doing-better-job-spacex-rand-simberg
« Last Edit: 09/30/2014 10:15 PM by Kabloona »

Online yg1968

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Re: Commercial Crew (CCtCAP) - Discussion Thread
« Reply #19 on: 09/30/2014 10:16 PM »
Here is a link to a thread on the CCtCap RFP documentation:
http://forum.nasaspaceflight.com/index.php?topic=32412.msg1257904#msg1257904

I don't know if this has been discussed elsewhere. But I believe that the protest by SNC will put a hold on CCtCap payments until the dispute is resolved.
« Last Edit: 01/09/2017 09:39 PM by yg1968 »

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