I just saw a report on a usenet group about a test-stand failure of a SpaceX Merlin engine. [Update: the original message appears to be missing, and none of the other replies contain much of the original message. I don’t know if this means that the initial report was bogus, or if it means that the person sharing it didn’t have the right to be doing so, and took it down to avoid legal problems for himself or his source.] Now, it is important to mention that the report didn’t mention which Merlin version this is. As I understand it, they have both the Merlin-1 and the Merlin-2 in development, and since the report doesn’t mention which Merlin variant the problem was with, it isn’t yet clear if this will affect the Falcon I launch planned for the end of this month. The current timeframe for the first flight was stated as being sometime between September 30th and mid-October, but if this was a failure of the exact same version of engine as is on the Falcon I that is being shipped out to Kwaj, that date might very well slip.
Here’s some excerpts from the report:
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.…
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.
Anyhow, if anyone else can verify this report, or clarify which version of the Merlin had this failure, I’d be interested to hear. The SpaceX crew has a lot of sharp engineers in their group, and I hope they’re able to figure out this bug and get things back on track for a succesful Falcon I first flight in the next month or so.
[Update 9/13/05: It appears that the original usenet post had some proprietary information in it that wasn’t supposed to be released publicly, so SpaceX has requested that the original poster remove the report. I was kinda suspicious since the person posting was an ATK employee. Anyhow, SpaceX has had test problems in the past, and they’ve been actually surprisingly forthright about most of them in Elon’s updates, as well as in other places. I’m sure there’s a good chance that we’ll hear more about the problem (sans proprietary details) and the solution to the problem in the near future.]
Jonathan Goff
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If you suppose there had been a lightweight kevlar shield around the engine, and three to eight other operating engines right beside this one, do you suppose it would have taken out at least one of those other engines?
Side note: If SpaceX is serious about being able to tolerate an engine-out, they’re going to need fuel and oxidizer cutoff valves either remote or shielded from the exploding bits.
Also, what’s the TPA? Thrust pivot assembly?
Ambivalent,
If you suppose there had been a lightweight kevlar shield around the engine, and three to eight other operating engines right beside this one, do you suppose it would have taken out at least one of those other engines?
I dunno. The loads the engine put on the structure were rather intense, and I’m not sure if a kevlar shield would have also surrounded the rest of the components. Basically, I don’t know.
Side note: If SpaceX is serious about being able to tolerate an engine-out, they’re going to need fuel and oxidizer cutoff valves either remote or shielded from the exploding bits.
Yes. But that much is pretty much obvious. I do believe the design we’re noodling for suborbital has just such an arrangement (ie with the blast shield between the shutoff valve and the engine). Of course, we will eventually have even more engines on our vehicle than the Falcon 9 (of course with regen cooled engines, good ignition detection and robust purges, the odds of blowing up an engine or having it come apart like this goes down substantially).
Also, what’s the TPA? Thrust pivot assembly?
I’m pretty sure TurboPump Assembly.
Hi, Jon.
Here’s the confirmation and a couple of quotes from Elon. It adds a couple of new details.
Thanks Ben!