SpaceX’s Crew Dragon spacecraft static fire anomaly - THREAD 3

[whitelancer64]

I'm waiting for a test that duplicates the conditions of the failed one. Meaning a used capsule that's hit the water and is subject to extreme vibration during the test. No reason to think any of that aggravated the problem, or that test is necessary before manned flight. It just seems like a needed step to declare victory.

It would be ridiculous to send a capsule to orbit and return it just to do a hot fire test.

[abaddon]

I'm waiting for a test that duplicates the conditions of the failed one. Meaning a used capsule that's hit the water and is subject to extreme vibration during the test. No reason to think any of that aggravated the problem, or that test is necessary before manned flight. It just seems like a needed step to declare victory.

It would be ridiculous to send a capsule to orbit and return it just to do a hot fire test.

The current investigation and hotfire (and subsequent in-flight abort test) will qualify Crew Dragon's abort capabilities for first use.  If SpaceX wants to qualify for re-use, a subsequent hotfire on the DM-3 capsule after successful return seems prudent and I think that's what Nomadd was suggesting.  I suppose they could also hotfire the DM-2 capsule after recovery from in-flight abort, but I would hope that would not be a certification requirement for flight of a new capsule.

[whitelancer64]

I'm waiting for a test that duplicates the conditions of the failed one. Meaning a used capsule that's hit the water and is subject to extreme vibration during the test. No reason to think any of that aggravated the problem, or that test is necessary before manned flight. It just seems like a needed step to declare victory.

It would be ridiculous to send a capsule to orbit and return it just to do a hot fire test.

The current investigation and hotfire (and subsequent in-flight abort test) will qualify Crew Dragon's abort capabilities for first use.  If SpaceX wants to qualify for re-use, a subsequent hotfire on the DM-3 capsule after successful return seems prudent and I think that's what Nomadd was suggesting.  I suppose they could also hotfire the DM-2 capsule after recovery from in-flight abort, but I would hope that would not be a certification requirement for flight of a new capsule.

As far as I know, hot fires will be a part of the Dragon refurbishment process anyway. That shouldn't be a part of certification.

[mn]

I'm waiting for a test that duplicates the conditions of the failed one. Meaning a used capsule that's hit the water and is subject to extreme vibration during the test. No reason to think any of that aggravated the problem, or that test is necessary before manned flight. It just seems like a needed step to declare victory.

Since they do know exactly what failed, it's fairly easy to determine that such a test serves no purpose.

[woods170]

I'm waiting for a test that duplicates the conditions of the failed one. Meaning a used capsule that's hit the water and is subject to extreme vibration during the test. No reason to think any of that aggravated the problem, or that test is necessary before manned flight. It just seems like a needed step to declare victory.

Since they do know exactly what failed, it's fairly easy to determine that such a test serves no purpose.

Particularly given the fact that the thing that failed (a check-valve) has been removed from the system and has been replaced by a burst disc.

[john smith 19]

Unless I missed something somewhere, though, the modified system cannot be simply re-fired like the original system was intended to be.  You have to replace the diaphragms first.

True.

How difficult that will be depends on how accessible those disks are and how easy they are to replace. I presume that was all worked out on the CAD models for the hardware long before they mfg the changed hardware.

Let's keep in mind this is an emergency system. Most of the time this flow path will not be used. I'd guess it would be like the pyrotechnics in the escape systems of commercial aircraft. Permanently installed but if you do have to use it (blow the doors, drop the escape chutes etc) all that's got to be replaced.  Otherwise the propellant is just for regular RCS tasks. 

It's a really neat synergy, totally eliminating the whole "escape tower" mass and development process. My instinct is this system is basically a pyro valve between the pressurization tank and the propellants. Under normal use it goes through a regulator. In emergency the full pressure hits the storable prop tanks, massively raising chamber pressure for the very short, very high thrust burn.

BTW is anyone else at least mildly impressed by that 207 day turnaround from anomaly, through fault identification to corrective action to retest?

It is always hoped that things turn out right first time but it sometimes seems to me that you only see the true quality of a development organization (good or bad) under pressure.

I think SX has been impressive.

Fingers crossed for the first US crew on a US LV carrying a US spacecraft since Shuttle before January 2020.

[TripleSeven]

Unless I missed something somewhere, though, the modified system cannot be simply re-fired like the original system was intended to be.  You have to replace the diaphragms first.

True.

.

Let's keep in mind this is an emergency system. Most of the time this flow path will not be used. I'd guess it would be like the pyrotechnics in the escape systems of commercial aircraft. Permanently installed but if you do have to use it (blow the doors, drop the escape chutes etc) all that's got to be replaced.  Otherwise the propellant is just for regular RCS tasks. 

Minor nit...there are really no "pyrotechnics" in the escape systems..."blow the doors"...really all the cabin crew do is "open" the doors with the slides armed...and the only pyros there are that with the doors armed, a "link" opens the pneumatic bottles that inflate the slides and the rest is history

it takes no electrical power only the cabin crew opening the doors.  "Most" doors today are gas operated meaning that they close and open on pnuematic pressure but again thats only a valve movement...the gas is internal.  if the door closes it will open (the B737 is the last Boeing with manual doors)

it is about 50K to "blow" the slides ...so usually it is done for testing on a real airplane near the end of life of the slides...they have to be repacked and recharged so often anyway.  also there is no damage to the plane when they open...if the slides are disconnected (" they can be used as life rafts under the supervision of a cabin crew member") they disconnect from the door system which is all internal

there is nothing remotely similar to launch escape system in a commercial plane...in the military planes there are the seats which are similar. 

on the topic of the LAS

I will be curious to see in future vehicles if what Boeing and SpaceX has done is followed.  SNC would have to do something like this...(I guess I dont have a clue what their escape system is like) ...but it strikes me that all in all the tower was a better plan.

SpaceX did the SuperD's on the capsule because at one point they were trying for propulsive landings.  so they are stuck with the "mass" of the engines throughout flight.  So is Boeings design...except I guess that they dont have it for landing...

but unless you are going to do propulsive landings its all dead mass after the LAS profile is done...and it all strikes me that the tower well at least you got rid of it

UNLESS of course (which I dont nkow) the massive thrusters are necessary for the from pad to second stage burnout LAS capability...then I guess it was the best solution.

[woods170]

on the topic of the LAS

I will be curious to see in future vehicles if what Boeing and SpaceX has done is followed.  SNC would have to do something like this...(I guess I dont have a clue what their escape system is like) ...but it strikes me that all in all the tower was a better plan.

SpaceX did the SuperD's on the capsule because at one point they were trying for propulsive landings.  so they are stuck with the "mass" of the engines throughout flight.  So is Boeings design...except I guess that they dont have it for landing...

but unless you are going to do propulsive landings its all dead mass after the LAS profile is done...and it all strikes me that the tower well at least you got rid of it

UNLESS of course (which I dont nkow) the massive thrusters are necessary for the from pad to second stage burnout LAS capability...then I guess it was the best solution.

One of the strengths mentioned by BOTH CCP providers is that their integrated abort systems offer abort capability on the pad as well as the entire ascent to orbit.

Which was very much not the case with some of the previous vehicles.

[TripleSeven]

on the topic of the LAS

I will be curious to see in future vehicles if what Boeing and SpaceX has done is followed.  SNC would have to do something like this...(I guess I dont have a clue what their escape system is like) ...but it strikes me that all in all the tower was a better plan.

SpaceX did the SuperD's on the capsule because at one point they were trying for propulsive landings.  so they are stuck with the "mass" of the engines throughout flight.  So is Boeings design...except I guess that they dont have it for landing...

but unless you are going to do propulsive landings its all dead mass after the LAS profile is done...and it all strikes me that the tower well at least you got rid of it

UNLESS of course (which I dont nkow) the massive thrusters are necessary for the from pad to second stage burnout LAS capability...then I guess it was the best solution.

One of the strengths mentioned by BOTH CCP providers is that their integrated abort systems offer abort capability on the pad as well as the entire ascent to orbit.

Which was very much not the case with some of the previous vehicles.

yes, I know the LAS tower system was weak..in terms of its full protection.  Guess I will have to do a little bit more looking into Orion's system...

[woods170]

on the topic of the LAS

I will be curious to see in future vehicles if what Boeing and SpaceX has done is followed.  SNC would have to do something like this...(I guess I dont have a clue what their escape system is like) ...but it strikes me that all in all the tower was a better plan.

SpaceX did the SuperD's on the capsule because at one point they were trying for propulsive landings.  so they are stuck with the "mass" of the engines throughout flight.  So is Boeings design...except I guess that they dont have it for landing...

but unless you are going to do propulsive landings its all dead mass after the LAS profile is done...and it all strikes me that the tower well at least you got rid of it

UNLESS of course (which I dont nkow) the massive thrusters are necessary for the from pad to second stage burnout LAS capability...then I guess it was the best solution.

One of the strengths mentioned by BOTH CCP providers is that their integrated abort systems offer abort capability on the pad as well as the entire ascent to orbit.

Which was very much not the case with some of the previous vehicles.

yes, I know the LAS tower system was weak..in terms of its full protection.  Guess I will have to do a little bit more looking into Orion's system...

When NASA switched from LockMart's 607 service module design to the ESM, the more powerful advanced Orion Main Engine was deleted in favour of a re-purposed shuttle OMS engine. This was mainly due to cost- and schedule considerations.

But the shuttle OMS engine provides quite a bit less "oomph" (27kN) than the originally designated OME (33kN). Which in turn led to the ESM design being equipped with more powerful auxilliary engines than originally intended.

This is necessary to provide Orion with sufficient thrust in those cases where it needs to abort off SLS while the LAS tower has already been jettisoned.

[TripleSeven]

on the topic of the LAS

I will be curious to see in future vehicles if what Boeing and SpaceX has done is followed.  SNC would have to do something like this...(I guess I dont have a clue what their escape system is like) ...but it strikes me that all in all the tower was a better plan.

SpaceX did the SuperD's on the capsule because at one point they were trying for propulsive landings.  so they are stuck with the "mass" of the engines throughout flight.  So is Boeings design...except I guess that they dont have it for landing...

but unless you are going to do propulsive landings its all dead mass after the LAS profile is done...and it all strikes me that the tower well at least you got rid of it

UNLESS of course (which I dont nkow) the massive thrusters are necessary for the from pad to second stage burnout LAS capability...then I guess it was the best solution.

One of the strengths mentioned by BOTH CCP providers is that their integrated abort systems offer abort capability on the pad as well as the entire ascent to orbit.

Which was very much not the case with some of the previous vehicles.

yes, I know the LAS tower system was weak..in terms of its full protection.  Guess I will have to do a little bit more looking into Orion's system...

When NASA switched from LockMart's 607 service module design to the ESM, the more powerful advanced Orion Main Engine was deleted in favour of a re-purposed shuttle OMS engine. This was mainly due to cost- and schedule considerations.

But the shuttle OMS engine provides quite a bit less "oomph" (27kN) than the originally designated OME (33kN). Which in turn led to the ESM design being equipped with more powerful auxilliary engines than originally intended.

This is necessary to provide Orion with sufficient thrust in those cases where it needs to abort off SLS while the LAS tower has already been jettisoned.

thank you so as they say "interrogative?"

as I "understand it" but I am unsure of it...CST 100 and Dragon both have abort capabilities on their internal abort system the entire range of powered flight.  indeed as I understand it to maintain that abort capability that is one reason along with the g loading, they went with the dual centaur...and the CST actually has to complete the orbital insertion so the Centaur is self disposing

is that correct?

if so interesting that the two vehicles have independent abort capability while Orion does not? 

thank you in advance

[woods170]

on the topic of the LAS

I will be curious to see in future vehicles if what Boeing and SpaceX has done is followed.  SNC would have to do something like this...(I guess I dont have a clue what their escape system is like) ...but it strikes me that all in all the tower was a better plan.

SpaceX did the SuperD's on the capsule because at one point they were trying for propulsive landings.  so they are stuck with the "mass" of the engines throughout flight.  So is Boeings design...except I guess that they dont have it for landing...

but unless you are going to do propulsive landings its all dead mass after the LAS profile is done...and it all strikes me that the tower well at least you got rid of it

UNLESS of course (which I dont nkow) the massive thrusters are necessary for the from pad to second stage burnout LAS capability...then I guess it was the best solution.

One of the strengths mentioned by BOTH CCP providers is that their integrated abort systems offer abort capability on the pad as well as the entire ascent to orbit.

Which was very much not the case with some of the previous vehicles.

yes, I know the LAS tower system was weak..in terms of its full protection.  Guess I will have to do a little bit more looking into Orion's system...

When NASA switched from LockMart's 607 service module design to the ESM, the more powerful advanced Orion Main Engine was deleted in favour of a re-purposed shuttle OMS engine. This was mainly due to cost- and schedule considerations.

But the shuttle OMS engine provides quite a bit less "oomph" (27kN) than the originally designated OME (33kN). Which in turn led to the ESM design being equipped with more powerful auxilliary engines than originally intended.

This is necessary to provide Orion with sufficient thrust in those cases where it needs to abort off SLS while the LAS tower has already been jettisoned.

thank you so as they say "interrogative?"

as I "understand it" but I am unsure of it...CST 100 and Dragon both have abort capabilities on their internal abort system the entire range of powered flight.  indeed as I understand it to maintain that abort capability that is one reason along with the g loading, they went with the dual centaur...and the CST actually has to complete the orbital insertion so the Centaur is self disposing

is that correct?

if so interesting that the two vehicles have independent abort capability while Orion does not? 

thank you in advance

Correct. Starliner does final orbit insertion itself, taking over from DEC (Dual Engine Centaur) just short of orbital insertion velocity. This ensures that, like the ET on shuttle, Centaur re-enters the atmosphere over some ocean and burns up.
G-loading profile for Starliner launch is mild, comparable to what it was for shuttle.
And yes, abort capability on Starliner is for the entire range of powered flight.

Crew Dragon is slightly different:
- Orbital insertion is done by F9 second stage, so the second stage goes into orbit as well. But S2 performs a de-orbit burn some time after Crew Dragon separation. This is similar to what is done on SpaceX CRS missions.
- G-loading profile for Crew Dragon is also mild, comparable to Starliner's
- Abort capability on Crew Dragon is also for the entire range of powered flight.

The main difference is the location of the abort system. On Crew Dragon it is integrated into the capsule itself (inherited from when Crew Dragon was supposed to do propulsive landing), so it comes down back to Earth all the way to splashdown.
On Starliner the abort system is integrated into the service module which, on a nominal mission, is dumped shortly after the de-orbit burn.

[TripleSeven]

The main difference is the location of the abort system. On Crew Dragon it is integrated into the capsule itself (inherited from when Crew Dragon was supposed to do propulsive landing), so it comes down back to Earth all the way to splashdown.
On Starliner the abort system is integrated into the service module which, on a nominal mission, is dumped shortly after the de-orbit burn.

yeap thanks pretty sure I had that correct

one more

so Orion after it loses the tower needs the final stage to abort and once the final stage starts firing (as in a normal launch) the only way to abort is to shut it down?

[edzieba]

I'm waiting for a test that duplicates the conditions of the failed one. Meaning a used capsule that's hit the water and is subject to extreme vibration during the test. No reason to think any of that aggravated the problem, or that test is necessary before manned flight. It just seems like a needed step to declare victory.

Since they do know exactly what failed, it's fairly easy to determine that such a test serves no purpose.

Particularly given the fact that the thing that failed (a check-valve) has been removed from the system and has been replaced by a burst disc.

1) AFAIK, there has been no definitive public statement yet of the source of the leak into the Helium system. The valve failed due to ingesting pressurised NTO, but SpaceX statement very carefully did not name that vale as the source of the leak during ground processing.

2) The burst discs do not replace the check valves, the check valves will still be present. They are necessary to prevent backflow (which would allow fuel to flow into the pressurant system then back out into the propellant, or vice verse, both of which are obviously catastrophic). The burst discs supplement the check valves, either upstream or downstream of them. My suspicion is downstream to keep the valves 'dry' of propellant until they are pressurised.

[abaddon]

so Orion after it loses the tower needs the final stage to abort and once the final stage starts firing (as in a normal launch) the only way to abort is to shut it down?

This is normal for tower-based systems, Soyuz for example.  In the case of Soyuz (and Orion I believe) the service module is responsible for the final burn, so not quite "the final stage" as it is a part of the integrated spacecraft through the entire mission until deorbit.

[woods170]

The main difference is the location of the abort system. On Crew Dragon it is integrated into the capsule itself (inherited from when Crew Dragon was supposed to do propulsive landing), so it comes down back to Earth all the way to splashdown.
On Starliner the abort system is integrated into the service module which, on a nominal mission, is dumped shortly after the de-orbit burn.

yeap thanks pretty sure I had that correct

one more

so Orion after it loses the tower needs the final stage to abort and once the final stage starts firing (as in a normal launch) the only way to abort is to shut it down?

There is a certain amount of time during the SLS launch that the Core Stage is still firing but the LAS tower is already gone. Abort during that phase means shutting down the Core Stage and firing the Orion OME (AND auxilliary engines) to get away from SLS pronto. But due to the limited thrust Orion is not getting away from SLS as fast as Starliner would be getting away from Atlas V or Crew Dragon getting away from F9.

When the Core Stage has finished its job the upper stage takes over to put Orion in orbit. When -during that phase - an abort is required the upper stage is shut down with again the Orion OME (AND the auxilliary engines) firing to get away from the upper stage. Same limitation in separation velocity as in the late-Core-Stage-abort scenario.

In both cases Orion enters a sub-orbital trajectory, re-enters more-or-less normally and splashes-down.

Shuttle-style Abort-To-Orbit is only possible when an abort is called very close to orbital insertion velocity (which is during upper stage operation). Don't know if this abort mode is actually being considered for Orion launches on SLS.

[woods170]

I'm waiting for a test that duplicates the conditions of the failed one. Meaning a used capsule that's hit the water and is subject to extreme vibration during the test. No reason to think any of that aggravated the problem, or that test is necessary before manned flight. It just seems like a needed step to declare victory.

Since they do know exactly what failed, it's fairly easy to determine that such a test serves no purpose.

Particularly given the fact that the thing that failed (a check-valve) has been removed from the system and has been replaced by a burst disc.

1) AFAIK, there has been no definitive public statement yet of the source of the leak into the Helium system. The valve failed due to ingesting pressurised NTO, but SpaceX statement very carefully did not name that vale as the source of the leak during ground processing.

2) The burst discs do not replace the check valves, the check valves will still be present. They are necessary to prevent backflow (which would allow fuel to flow into the pressurant system then back out into the propellant, or vice verse, both of which are obviously catastrophic). The burst discs supplement the check valves, either upstream or downstream of them. My suspicion is downstream to keep the valves 'dry' of propellant until they are pressurised.

The valve that separates the pressurant system from the propellant systems is what leaked during ground processing. NTO leaked passed this leaky valve into the pressurant system.
It is this leaky valve, separating pressurant system and propellant systems, that has been replaced by a burst disc.

[TripleSeven]

The main difference is the location of the abort system. On Crew Dragon it is integrated into the capsule itself (inherited from when Crew Dragon was supposed to do propulsive landing), so it comes down back to Earth all the way to splashdown.
On Starliner the abort system is integrated into the service module which, on a nominal mission, is dumped shortly after the de-orbit burn.

yeap thanks pretty sure I had that correct

one more

so Orion after it loses the tower needs the final stage to abort and once the final stage starts firing (as in a normal launch) the only way to abort is to shut it down?

There is a certain amount of time during the SLS launch that the Core Stage is still firing but the LAS tower is already gone. Abort during that phase means shutting down the Core Stage and firing the Orion OME (AND auxilliary engines) to get away from SLS pronto. But due to the limited thrust Orion is not getting away from SLS as fast as Starliner would be getting away from Atlas V or Crew Dragon getting away from F9.

When the Core Stage has finished its job the upper stage takes over to put Orion in orbit. When -during that phase - an abort is required the upper stage is shut down with again the Orion OME (AND the auxilliary engines) firing to get away from the upper stage. Same limitation in separation velocity as in the late-Core-Stage-abort scenario.

In both cases Orion enters a sub-orbital trajectory, re-enters more-or-less normally and splashes-down.

Shuttle-style Abort-To-Orbit is only possible when an abort is called very close to orbital insertion velocity (which is during upper stage operation). Don't know if this abort mode is actually being considered for Orion launches on SLS.

OK great so I do understand it...thanks for the explanation

[edzieba]

I'm waiting for a test that duplicates the conditions of the failed one. Meaning a used capsule that's hit the water and is subject to extreme vibration during the test. No reason to think any of that aggravated the problem, or that test is necessary before manned flight. It just seems like a needed step to declare victory.

Since they do know exactly what failed, it's fairly easy to determine that such a test serves no purpose.

Particularly given the fact that the thing that failed (a check-valve) has been removed from the system and has been replaced by a burst disc.

1) AFAIK, there has been no definitive public statement yet of the source of the leak into the Helium system. The valve failed due to ingesting pressurised NTO, but SpaceX statement very carefully did not name that vale as the source of the leak during ground processing.

2) The burst discs do not replace the check valves, the check valves will still be present. They are necessary to prevent backflow (which would allow fuel to flow into the pressurant system then back out into the propellant, or vice verse, both of which are obviously catastrophic). The burst discs supplement the check valves, either upstream or downstream of them. My suspicion is downstream to keep the valves 'dry' of propellant until they are pressurised.

The valve that separates the pressurant system from the propellant systems is what leaked during ground processing. NTO leaked passed this leaky valve into the pressurant system.
It is this leaky valve, separating pressurant system and propellant systems, that has been replaced by a burst disc.

This is not supported by any official public (or L2) information from SpaceX or NASA. Do you have an alternate source that the "leak during ground processing" was from the same valve that was destroyed? Additionally, removing a check valve would be extremely unlikely, for the reasons previously stated.

[docmordrid]

>
The valve that separates the pressurant system from the propellant systems is what leaked during ground processing. NTO leaked passed this leaky valve into the pressurant system.
It is this leaky valve, separating pressurant system and propellant systems, that has been replaced by a burst disc.

This is not supported by any official public (or L2) information from SpaceX or NASA. Do you have an alternate source that the "leak during ground processing" was from the same valve that was destroyed? Additionally, removing a check valve would be extremely unlikely, for the reasons previously stated.

And here I thought SpaceX laid it all out in gory detail in this update.