Test Failure of SpaceX Merlin VTS1-221Engine

Got this in an email:

SpaceX attempted a full Mission Duty Cycle (MDC) test of the Merlin S/N
003 engine on Wednesday, 7 Sep 05 with catastrophic results.

At T+158 seconds the chamber and nozzle separated from the engine,
breaking several mounts including one of the pitch/yaw actuators and
one of two struts which attach to the TPA. Joints in the fuel lines
from the TPA to the engine injector and the gas generator were
separated causing fuel to be sprayed around the test stand for just a
short time (probably less than 1-2 seconds) but sufficient to burn for
10-15 minutes.

Most of the ablative chamber/nozzle was found in pieces beyond the
flame duct. The throat and upper part of the divergent section of the
nozzle, surprisingly, were found intact at some distance away. It
appears that the proximate cause of the failure was that the ablative
chamber separated from its attach ring. The ring is still firmly
attached to the engine. A flange, which is part of the engine dome and
keeps the chamber centered on the engine when attached, appears to have
been torn away. In the attached picture you can see the attach ring on
the top of the chamber/nozzle as it was being assembled to the engine
yesterday. The red colored RTV-covered ring on the bottom of the
engine proper is the flange described above.

It looks like when the chamber started to come off that the side forces
generated were sufficient to break the strut and pitch/yaw actuator
attach points and the engine swiveled into the TPA causing fuel lines
to break, damaging the TPA, and tearing apart the turbine exhaust and
roll control nozzle.

Technicians are evaluating now the damage done to facility wiring, tank
insulation, and valves. It may take two weeks to repair the damage and
get the stand back in shape to test a Merlin. The next Merlin engine
is in El Segundo waiting for an engine computer to complete acceptance
testing and might ship as early as next Monday. In the meantime SpaceX
intends to press with Kestrel testing which should be largely
unaffected by the Merlin problems.

wrote:

Got this in an email:




Now, if we cluster nine of these motors together for the Falcon 9, we
will be well on the way to replicating the reliability of the N-1.
Benign shutdown, my ass. :-)

Pat

On Mon, 12 Sep 2005 15:01:31 -0500, Pat Flannery
wrote:

Now, if we cluster nine of these motors together for the Falcon 9, we
will be well on the way to replicating the reliability of the N-1.

I seem to recall that the SSMEs had quite a problem working in a
cluster of 3 to begin with as well. You can see the results of that
testing when they come to it.

Benign shutdown, my ass. :-)

They did mention during initial testing that this engine used to
disassemble itself a lot, but they also mentioned that they have since
got it working reliably. Except in this case of course.

Well this disassembly happening at 158 seconds into the test, would be
very late in a real flight situation. And I don't think that it would
be accurate to compare ground test damage to flight damage.

However, this is clearly not a good thing. And I am doubting that they
would publicize this on their site.

You are also correct that this shutdown did not go too well, when it
obviously failed to detect that the end came off and fuel was now
leaking everywhere. The 1 to 2 seconds for this to shut down is an
eternity in computer time. This almost makes me wonder if this was
manually done.

You should look on the bright side though, when this may well have
been a rare exception. They will soon be back to testing. And if there
is a problem with the attach ring joint, then they can see about
fixing it.

An engine not doing this would be nice.

Cardman.

In article ,
Pat Flannery wrote:

Now, if we cluster nine of these motors together for the Falcon 9, we
will be well on the way to replicating the reliability of the N-1.
Benign shutdown, my ass. :-)

Ass, indeed. Do you suppose that they will not learn from these
failures and fix them? Did your third computer code work perfectly the
first time?

wrote:

Got this in an email:

(...) In the attached picture you can see the attach ring on
the top of the chamber/nozzle as it was being assembled to the engine
yesterday. The red colored RTV-covered ring on the bottom of the
engine proper is the flange described above.


May we see "the attached picture"?

Regards,
NE

richard schumacher wrote:

Ass, indeed. Do you suppose that they will not learn from these
failures and fix them?


They had better hope they fix them in a way that senses that there is
something wrong with the motor and shuts it down before it flies apart
like it did this time.

Did your third computer code work perfectly the
first time?



They had better have a look at _their_ computer code and how it relates
to detecting a anomaly before it becomes catastrophic like it did this time.
This is that non-benign shutdown scenario I was writing about a few days
ago, before I heard about this incident.
The kind that leads to chain reaction failures on clustered motors.

Pat

"New European" wrote
May we see "the attached picture"?


or at least, email us individual copies as requested? grin

i request!

Pat Flannery wrote:
wrote:

Got this in an email:



Now, if we cluster nine of these motors together for the Falcon 9, we
will be well on the way to replicating the reliability of the N-1.
Benign shutdown, my ass. :-)


Could we see the email - or at least a summary of
what this discussion is about? This message appears
to have been truncated.

Thanks,

- Ed Kyle

"Pat Flannery" wrote in message
...

They had better have a look at _their_ computer code and how it relates
to detecting a anomaly before it becomes catastrophic like it did this
time.
This is that non-benign shutdown scenario I was writing about a few days
ago, before I heard about this incident.
The kind that leads to chain reaction failures on clustered motors.

You're missing the possibility that this could have been a purely structural
failure. Sometimes structures fail with little to no warning when they're
placed under load. If this is the case, then there wouldn't be much of
anything to detect before the failure occurred.

Jeff
--
Remove icky phrase from email address to get a valid address.

I'll vote for unclustered motors also.