Commercial Crew (CCtCAP) - Discussion Thread

[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

[clongton]

Thanks Chris. This is a whole new world

[Darkseraph]

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?

[kevinof]

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?

[nadreck]

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.

[kevinof]

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.

[Mongo62]

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.

[erioladastra]

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

[rcoppola]

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.)

[Mongo62]

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.

[QuantumG]

They're called "cracks". Slamming an object into the ocean at high speeds tends to make them.

[BrianNH]

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.

[erioladastra]

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.

[TrevorMonty]

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.

[Garrett]

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

[baldusi]

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.

[erioladastra]

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.

[deruch]

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.

[Kabloona]

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

[yg1968]

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.