SpaceX Dragon 2 capsule destroyed in abort motor ground test

In article ,
says...

Jeff Findley wrote on Tue, 30 Apr 2019
14:08:51 -0400:


Also, from what I understand, there is a list of safety related issues
that NASA wanted SpaceX to take care of before flying crew on DM-2. The
other "silver lining" is that this gives SpaceX more time to take care
of those issues as well.


Would you happen to know what those are or be able to point me to a
description of them?

Neither SpaceX nor NASA has released this list. So I have no idea what
is on it. This is part of the double edged sword of a "commercial"
program like this. NASA is paying for results and milestones and has
insight into the designs. But the designs remain the property of the
company, not NASA. So information like this is tightly controlled.

I'm guessing that Starliner has a list of open issues as well, but again
neither Boeing nor NASA is talking about the issues (well, beyond their
anomaly with their hypergolic propellants after a ground test). We have
no idea how severe the damage was after that test because no one leaked
any pictures or video.

Also, NASA has reiterated their policy for images and video. Leaks like
that SpaceX Dragon 2 video, by a NASA employee, can have dire
consequences up to and including termination. The email sent out to KSC
employees has been widely reported on space news websites over the last
day or so.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

On 19-05-01 13:55 , Jeff Findley wrote:
In article ,
says...

On 2019-04-30 14:10, Jeff Findley wrote:

I'm pretty sure they're totally independent. The pairs of SuperDracos
are fully independent from each other.

I believe this is correct. It gives the system some redundancy to have
these separate.


Considering current role of Super Dracos as being potentially useful
only during launch, and hopefully never used, wouldn't it make more
sense for them to share the weight of fuel with the dracos?

No. Dracos are likely much lower pressure than Super Dracos. It's much
simpler to have separate tanks in this case.

aka: if all goes well at launch, the fuel is used by dracos during
on-orbit operations. And if Super Dracos is used during launch, you're
not going to need the fuel for dracos isn't you're not going to orbit.

The intent was to use the Super Dracos for vertical landing on a nominal
mission. NASA nixed that, so we're left with them being there with no
operational use on a nominal mission.

I believe that Elon Musk has said that the Super Dracos would in future
be a back-up for the Dragon 2 parachutes, slowing the capsule before the
splash-down in case of parachute failure. This is only possible if the
Super Draco propellant is not consumed in the Dracos before re-entry.

Mentioning the parachutes reminds me that the Dragon 2 DM-1 parachutes
seemed very "restless" during the descent. The parachutes billowed,
flexed, and sometimes swapped places in the 4-parachute formation. Is
this a worrying kind of instability? Can it be a result of having 4
parachutes instead of 3, giving a different kind of symmetry and
inter-parachute interaction?

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .

Niklas Holsti wrote on Wed, 1 May 2019
14:52:08 +0300:

On 19-05-01 13:55 , Jeff Findley wrote:
In article ,
says...

On 2019-04-30 14:10, Jeff Findley wrote:

I'm pretty sure they're totally independent. The pairs of SuperDracos
are fully independent from each other.

I believe this is correct. It gives the system some redundancy to have
these separate.


Considering current role of Super Dracos as being potentially useful
only during launch, and hopefully never used, wouldn't it make more
sense for them to share the weight of fuel with the dracos?

No. Dracos are likely much lower pressure than Super Dracos. It's much
simpler to have separate tanks in this case.

aka: if all goes well at launch, the fuel is used by dracos during
on-orbit operations. And if Super Dracos is used during launch, you're
not going to need the fuel for dracos isn't you're not going to orbit.

The intent was to use the Super Dracos for vertical landing on a nominal
mission. NASA nixed that, so we're left with them being there with no
operational use on a nominal mission.

I believe that Elon Musk has said that the Super Dracos would in future
be a back-up for the Dragon 2 parachutes, slowing the capsule before the
splash-down in case of parachute failure. This is only possible if the
Super Draco propellant is not consumed in the Dracos before re-entry.


True. If they had a multiple parachute failure (the thing can still
get down safely on three, the ride at the end is just a little
rougher) they could use the SuperDracos to kill vertical velocity
before splashdown. To be fair, the tiny 90 lb thrust Dracos would be
pretty unlikely to exhaust the six tons of fuel that the SuperDracos
carry in aggregate to support the huge thrust they deliver.


Mentioning the parachutes reminds me that the Dragon 2 DM-1 parachutes
seemed very "restless" during the descent. The parachutes billowed,
flexed, and sometimes swapped places in the 4-parachute formation. Is
this a worrying kind of instability? Can it be a result of having 4
parachutes instead of 3, giving a different kind of symmetry and
inter-parachute interaction?


It wouldn't surprise me that a cluster of four chutes would wind up
behaving differently in descent than the three chutes on a Dragon I.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden

JF Mezei wrote on Wed, 1 May 2019
11:27:42 -0400:

On 2019-04-30 21:19, Fred J. McCall wrote:

They didn't "start designing it for powered landings". They also
FINISHED designing it for powered landings and built the thing that
way (with the exception of removing the landing legs, which Musk says
they could still put back with little to no difficulty).


ok that answers the question then. The super Dracos need to have their
own fuel since every flight was originally meant to use the engines to
land.


The SuperDracos not only have their own fuel supply, but each pair has
its own fuel supply independent of the other three pairs. Each pair
gets about a ton and a half of propellants.


Theoretical question:

would it be possible to have shared fuel tanks, pressurize them to
"super draco" levels for take-off if needed, then reduce pressure to fit
the Draco needs? That would allow shared fuel and reduce total weight
and number of components.


Anything is possible, but what you describe INCREASES the complexity
and number of components in the system


How did the Shuttle work the differences between thrusters and OMS? were
they on totally separate fuel/pressure systems ?


OMS thrusters are typically either cold gas or hypergolics. Shuttle
main engine was liquid hydrogen/LOX. Totally different engine
designs.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

JF Mezei wrote on Wed, 1 May 2019
16:23:59 -0400:

On 2019-05-01 12:22, Fred J. McCall wrote:

OMS thrusters are typically either cold gas or hypergolics. Shuttle
main engine was liquid hydrogen/LOX. Totally different engine
designs.

I was talking about the medium engines in the back using hypergolics.
The ones used to finish orbit after MECO, and the ones used to de-orbit
the shuttle.


You need to be clearer. It's bad enough that I have to look up
answers for you. Having to guess what the hell you're actually asking
just makes it a bigger pain.


Thought they were called OMS. So asked whether they shared
fuel/pressurization with the various thrusters located throughout the
shuttle.


There are two different systems; OMS and RCS. The OMS engines are in
two pods at the after end of the Shuttle. Each has its own fuel
supply, but they can be cross-connected to allow fuel from one OMS pod
to be used by the OMS engine in the other pod. Each OMS pod also
contains RCS engines as part of the pod. I believe (I don't find
anything definitive) that these large RCS engines (they come in two
sizes) CAN share the same fuel and pressurization system as the OMS
engines in the pod (it's all build as a unit). There are other RCS
engines located in other pods around the Shuttle. These all have
their own fuel and pressurization systems ('pods' are managed as
replaceable units). OMS engines are 6000 lb thrust engines and each
OMS pod carries around six tons of propellants for the OMS engine in
the pod. The large RCS engines produce just under 1000 lbs of thrust
each. They have their own propellant supply but can be cross
connected between the two rear pods and/or cross connected with the
OMS propellant feeds. The small RCS engines (vernier engines) are
much smaller with around 25 lbs of thrust and have their own fuel
supplies.

Note that the difference between the vernier engines and the OMS
engines is about the same order as the difference between a Draco and
a SuperDraco and they have their own fuel and pressurization systems
separate from the OMS engines. I'd guess that what happens when you
'interconnect' the aft OMS and RCS engines is that the higher pressure
OMS tanks vent into the RCS tank system which then delivers the fuel
to the RCS engines at the lower pressure. Of course, there's only a
factor of six or seven between the thrust of the OMS and RCS engines,
so they may be close enough in operating pressure for it not to
matter. This is in contrast to the 200x difference in thrust between
the Draco and the SuperDraco.




--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

JF Mezei wrote on Thu, 2 May 2019
00:03:08 -0400:

On 2019-05-01 21:10, Fred J. McCall wrote:

There are two different systems; OMS and RCS.

So my reference to OMS was correct.


Perhaps, but unclear.

Note that the difference between the vernier engines and the OMS
engines is about the same order as the difference between a Draco and
a SuperDraco

That is why I asked the question. So Dragon 2 mimicks the shuttle in
having separate fuel systems for the differnt types of engines.


I don't think it's a question of 'mimicking' anything. I think it's a
case of exactly what people have been telling you being correct. That
being that the operating pressures of the two engines are sufficiently
different that feeding one from the other won't work.


And that would mean that in the "exploded" Dragon 2, the fuel and
pressurisation of the Super Draco engines had not been used during the
flight. But would still have expereinced launch vribration and
temperature extremes of space as well as spash down in salt water.


True but irrelevant. Do you seriously think they didn't check the
thing out after it landed?


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn

In article ,
says...

On 2019-04-30 21:19, Fred J. McCall wrote:

They didn't "start designing it for powered landings". They also
FINISHED designing it for powered landings and built the thing that
way (with the exception of removing the landing legs, which Musk says
they could still put back with little to no difficulty).


ok that answers the question then. The super Dracos need to have their
own fuel since every flight was originally meant to use the engines to
land.


Theoretical question:

would it be possible to have shared fuel tanks, pressurize them to
"super draco" levels for take-off if needed, then reduce pressure to fit
the Draco needs? That would allow shared fuel and reduce total weight
and number of components.

How did the Shuttle work the differences between thrusters and OMS? were
they on totally separate fuel/pressure systems ?

As usual, the KSC web pages have a wealth of information about the space
shuttle system (since this was a NASA vehicle, they're quite open about
it).

The OMS engines and RCS engines had their own sets of tanks for much the
same reason that the Dracos and Super Dracos are separate. See this
diagram:

https://upload.wikimedia.org/wikiped...d_schematic.pn
g

Lots of text about the OMS system he

https://science.ksc.nasa.gov/shuttle...f/sts-oms.html

Note from above the OMS propellant pressure was regulated to:

The primary regulator outlet pressure at normal flow is 252 to 262
psig and 247 psig minimum at high abort flow, with lockup at 266
psig maximum. The secondary regulator outlet pressure at normal
flow is 259 to 269 psig and 254 psig minimum at high abort flow,
with lockup at 273 psig maximum.

RCS system he

https://science.ksc.nasa.gov/shuttle...f/sts-rcs.html

Note from above the RCS propellant pressure was regulated to:

The primary regulates the pressure at 242 to 248 psig, the
secondary at 253 to 259 psig.

Also, the forward RCS engines had tanks and plumbing completely separate
from the aft OMS pods (there is no mention of any crossfeed to the
forward RCS system). Makes sense considering how far apart they were.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

On Wednesday, May 1, 2019 at 6:57:25 AM UTC-4, Jeff Findley wrote:
In article ,
says...

On 2019-04-30 14:05, Jeff Findley wrote:

You're going to get little to no actual useful information from a cell
phone video. It's way too low frame rate and the way they respond to
rapid changes in light pretty much means you can't trust the few frames
you have.


That video shows no exhaust from super dracos for a meaningful time
prior to even.

And it shows a pretty big explosion with lost of debris flying.

It pretty much confirms that the Dragon 2 is a total loss. (something
which SpaceX didn't confirm at least not at the time that vode was
released).

While I agree it's likely this Dragon 2 is a total loss, we really don't
know the extent of the damage from a low frame rate cell phone video.
For all we know, at the end of the video, Dragon 2 could be sitting
mostly intact just out of the frame.

Jeff
--

I saw an update on this question in AP News today. "SpaceX confirms its crew capsule was destroyed in ground testing two weeks ago."

https://apnews.com/2d41dee71a3f49feadc5987f59d603bd

Goes on to say: "SpaceX still cannot access the test stand at Cape Canaveral, Florida, because of toxic fuel contamination."

Which is yikes.

Dave

Dave

wrote on Thu, 2 May 2019 10:03:10 -0700 (PDT):

On Wednesday, May 1, 2019 at 6:57:25 AM UTC-4, Jeff Findley wrote:
In article ,
says...

On 2019-04-30 14:05, Jeff Findley wrote:

You're going to get little to no actual useful information from a cell
phone video. It's way too low frame rate and the way they respond to
rapid changes in light pretty much means you can't trust the few frames
you have.


That video shows no exhaust from super dracos for a meaningful time
prior to even.

And it shows a pretty big explosion with lost of debris flying.

It pretty much confirms that the Dragon 2 is a total loss. (something
which SpaceX didn't confirm at least not at the time that vode was
released).

While I agree it's likely this Dragon 2 is a total loss, we really don't
know the extent of the damage from a low frame rate cell phone video.
For all we know, at the end of the video, Dragon 2 could be sitting
mostly intact just out of the frame.

Jeff
--

I saw an update on this question in AP News today. "SpaceX confirms its crew capsule was destroyed in ground testing two weeks ago."


Yeah, I saw something on that, as well. What I saw said they were 500
msec away from SuperDraco ignition.


https://apnews.com/2d41dee71a3f49feadc5987f59d603bd

Goes on to say: "SpaceX still cannot access the test stand at Cape Canaveral, Florida, because of toxic fuel contamination."

Which is yikes.


Well, I guess that isn't maybe too surprising given tons of
uncombusted propellants sprayed about. Both hydrazine and dinitrogen
tetroxide are pretty toxic stuff.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden

JF Mezei wrote on Thu, 2 May 2019
15:55:52 -0400:

On 2019-05-02 15:42, Fred J. McCall wrote:

Yeah, I saw something on that, as well. What I saw said they were 500
msec away from SuperDraco ignition.

So my theory based on seeing no exhaust out of the engines prior to
explosion on that small phone video wasn't so stupid after all.


Well, yeah, it was. You realize that "500 msec" means you're right in
the midst of it, don't you?


If they know what happens 500ms prior to ignition, they should be able
to get a better idea of what went wrong.


Do you have any clue just how short 500 msec is when you're talking
about ignition of a hypergolic engine?


Are fuel tanks always compressed, or does a valve open to "prime" the
fuel tanks only once engines may be ignited ? (for instance, only
compressing the tanks when crews enter Dragon 2 (before which , the
"eject" function wouldn't be needed/used) ?


Where you say "compressed" I'll pretend you mean "pressurized" so that
your question at least makes lexical sense. You ask the question like
it matters. It doesn't, but I'll answer it anyway. The simple answer
is 'yes'. I say that because BOTH cases are true. Generally the fuel
tanks won't be initially pressurized until just before the first time
you fire the rocket engine. However, since there is no way to
depressurize the fuel tank once it's pressurized, it would be under
pressure from that point on so that if you shut the engine down, fuel
tanks are now essentially forever under pressure from that point on.
In this particular case, they wouldn't pressurize the fuel tanks just
because crew was aboard. They pressurize when they're ready to fire
the engine. If you never use it, the fuel tanks never get
pressurized.

All that said, the probabilities of what went wrong remain the same:
COPV failure, pressurization valve or sensor system failure,
propellant tank failure, propellant line failure, combustion chamber
failure.

Goes on to say: "SpaceX still cannot access the test stand at Cape Canaveral, Florida, because of toxic fuel contamination."

Aren't there suits and SCUBA units they can wear to retreive some
important debris (such as recorders) and epecially photograph the debris
and their location ?


Why would you put people at risk for any of that? You've got to clean
it up anyway, so do that.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden