"ShitElonSays.com"?! And it's a serious website. The net is a strange and wonderful place... Thanks!
On 10/7/2013 11:11 AM, Ben Brockert wrote:
On Mon, Oct 7, 2013 at 11:42 AM, Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx> wrote:One other new fact there: "During a postlaunch press briefing Sept. 29, meanwhile, SpaceX Chief Executive Elon Musk said the company had plenty of telemetry data to analyze why the rocket’s on-board computer halted the upper-stage reignition sequence." Note however that this says nothing about where in that sequence the halt came. You might easily assume the halt came on a minor pre-light discrepancy, but it could equally well have been on a major post-ignition departure from nominal. The statement carefully doesn't specify, but the fact that they didn't try again makes the latter seem more likely.Reading or listening to the post-flight conference might be productive: http://shitelonsays.com/transcript/spacex-press-conference-september-29-2013-2013-09-29 "Before deciding what the issue was, I think we want to have a bit more time to read the data, before coming to a conclusion. We essentially saw the engine initiate ignition get up to about 400 psi and then it encountered a condition that it didn't like. It may have been due to an extended spin start, maybe, but this is speculative. So it initiated an abort of the restart. But we have all of the data from the restart. So I am confident that we will be able to sort it out and address it before the next flight. It's nothing fundamental. On the test stand, we have restarted the Merlin 1-D engine in some cases dozens of times. We just have to iron out some slight differences of it operating in vacuum."
Or of it operating in zero-G (or in greatly reduced G, if they light during an RCS "settling burn".
So, the engine reached 400 psi of a roughly 1000 psi nominal operating level, then its controller saw something out of nominal and shut it down. Another interesting question then is, how strict/how detailed is "out of nominal"? Engine controller abort monitoring approaches can vary from waiting a bit then checking for higher-than-coldflow minimum chamber pressure, to tracking a whole bunch of engine parameters versus time for relatively small variations from expected values. The former approach can miss subtler problems, the latter can shut down an engine that still might have flown the mission albeit possibly off-nominally.
IE, was the shutdown over a real problem, or over a hiccup that if ignored wouldn't have caused a mission failure?
My take: SpaceX will have to satisfy this customer and its insurers before this next launch takes place, and the rest of its customers and their insurers at some point. Chances are more hard data will become public in the process.I don't share your optimism there at all. They were very effective at never releasing the incident report or other conclusions from the review board of CRS-1, and I expect the same will happen here.
Satisfying the customer and its insurers doesn't necessarily involve public release of the incident report. I expect NASA saw the CRS-1 report though, and I expect SES and its insurers will see the data and report on this relight attempt. (Or else there will be at minimum some serious renegotiation of both the flight price and the insurance coverage, and at worst the flight might not happen at all.)
And once the customer and insurers have the info, the key findings will most likely come out. The key conclusion of the CRS-1 review did come out, after all. One engine chamber split open catastrophically (as I and presumably others had already figured out from the video), the location of the split was the forward engine fuel dome, and the cause of the split was some combination of a manufacturing flaw and repeated testing stresses. Not as detailed as I'd like either, no, but it does cover the essential basics.
Henry
