…from Alan Boyle. I don’t think this is quite right, though:
What caused the engine’s sudden pressure release, which was apparently strong enough to blow off the fairing?
I think this is a misstatement of the issue. I could be wrong, because we’re still awaiting clarification from SpaceX, but my understanding is that when they shut the engine down, and there was no pressure field coming from the nozzle, the differential pressure resulting from Max Q resulted in it “imploding” inward and breaking off (and perhaps taking the nozzle with it, but that’s less clear). All that is clear is that SpaceX claims that the powerhead itself wasn’t damaged, because they continued to receive telemetry from it.
I should note that if this is the case, it eliminates any earlier concerns about the upper-stage engine causing a catastrophic failure, though questions remain about about why Orbcomm is in the wrong orbit. This is clearly a second-stage issue.
[Update a couple minutes later]
Here’s the current story from Joe Pappalardo at Popular Mechanics. I’ll probably be elaborating on it after getting more info from SpaceX.
Anyone know if the first stage was going to be recovered on this flight? I assume not or there would have been some mention of it. Looking at the damaged engine might tell them quite a bit.
The Space-X press release says: Panels designed to relieve pressure within the engine bay were ejected to protect the stage and other engines.
This implies an active process, where the panels got some kind of command and impulse applied to “eject” them. That seems to go against their KISS design practices. Perhaps the panels were designed to break off when the loads were exceeded – that seems more likely. With a passive design, there is less to go wrong.
And the silence on the Orbcomm secondary payload implies that it’s not in the desired orbit. Note that they explicitly say that the cargo resupply is not affected.
I may be wrong but it seems like SpaceX has given up trying to recover the first stage using parachutes. It looks like their long-term strategy is to have the stage land vertically under its own power.
As Buzz Aldrin pointed with Starbooster years ago, pulling a liquid fuel stage out of the ocean and refurbishing it isn’t much of a savings. By contrast if you recover it on land all you need to do is check it out and refuel, a much quicker and less expensive process.
Concur on pulling anything out of sea water and reusing it. I used to scuba dive and do underwater photography. I had my Nikonos camera refurbished after every trip – disassembled, all o-rings replaced, new silicon lube, body cleaned, etc. My 35mm housing got a similar treatement I did myself – of course it’s Lexan, so no corrosion concerns.
Yes, the story has changed somewhat. Now it’s a protective panel rather than a fairing that was ejected. What I was trying to get at is, what caused the sudden pressure loss, which was apparently quite serious?
Hi, Alan.
Well, I haven’t heard that the pressure loss that caused the shutdown was “sudden” (I haven’t heard much about it at all). All I know is that it was sufficient to result in an automatic engine shutdown (it may have been just slightly out of tolerance, as was the case with earlier launch aborts). It was the shutdown that resulted in the fairing, or protective panel, or whatever being shoved inward. Whether the cause of the engine shutdown was serious or not (other than the result of it) remains to be seen. In any event, it may be somewhat moot because whatever caused it could be a design issue of the Merlin 1C, which only has one more flight scheduled. But there are always lessons to be learned for future designs.
I was just pointing out that your terminology of a “sudden pressure release” was misleading because some might have thought you were referring to the sudden absence of pressure from the nozzle exit. To the degree that was “sudden,” it was clearly because that’s how the engine was shut down.
Also, is there some useful distinction between a “protective panel” and a fairing? Because I always thought that a fairing is simply a bunch of protective panels, or one continuous one, against aerodynamic pressure.
I was wondering the same thing. Also, “ejected” sounds as if it was intentional, wouldn’t “torn off” or “ripped to pieces” be more accurate? And even if the fragment didn’t hit the nozzle, wouldn’t the airflow be very damaging too, especially near max q? I imagine that fairing is there for a reason.
I would guess that if there was no technical issue in preventing the re-ignition of the second stage that SpaceX, through an overabundance of caution, decided to not attempt the second firing so as to avoid any possibility of an explosion that would have created a debris field that ISS could then possibly encounter.
Orbcomm has issued a press release that clarifies this.
However, due to an anomaly on one of the Falcon 9’s first stage engines, the rocket did not comply with a pre-planned International Space Station (ISS) safety gate to allow it to execute the second burn. For this reason, the OG2 prototype satellite was deployed into an orbit that was lower than intended. ORBCOMM and Sierra Nevada Corporation engineers have been in contact with the satellite and are working to determine if and the extent to which the orbit can be raised to an operational orbit using the satellite’s on-board propulsion system.
It goes on to note that Orbcomm still intends to launch the remaining satellites on Falcon 9.
Thanks, Martijn, that was a very useful input to the story I just submitted.
It appears the Orbcomm vehicle does have on-board propulsion. Hopefully it has ample reserves to correct its orbit and have a long opeartional life.
I think they simply used too much fuel to compensate for the loss of the engine, and canceled the second Stage 2 burn. They probably didn’t have enough fuel left to make it worthwhile. Of course, that’s just a guess on my part.
I wonder if a second burn could have caused a stage disposal or debris hazard issue considerign the low fuel status?
Each stage has it’s own fuel, so why would a longer burn on the first stage that compensates for the loss of an engine have any effect on the second stage fuel? The issue referred to above was ‘safety gate.’ Can somebody explain that terminology?
Gravity loss. The longer the first stage burns at sub-optimal thrust the more energy you lose to gravity, and the longer the second stage has to burn to compensate.
Ok, but two points. Gravity loss means lower energy in the rocket but has nothing to do with how much fuel is on the second stage which Rickl referred to. Second, the F9 turns off two engines anyway to keep it under 5 gs. So why would the remaining engines produce suboptimal thrust?
No, but it determines how much fuel is left when the stage reaches orbit since it has to provide more of the delta-V to reach orbit. The impact would depend on where in the launch the engine goes out; you’d see a much greater effect from an engine failing one second after launch than an engine failing one second before two were going to be shut down to reduce g-loading.
I read somewhere that the second stage burned longer too.
Of course, that could have been speculation on somebody’s part. There’s been a lot of that going around.
The slow motion video is certainly startling. It looked fairly explosive to me.
I think SpaceX is arguing that the fairing shot first.
My understanding is that after the first stage anomaly they were in a slightly different place/orbit than planned and that place/orbit was not within the “ok by Nasa to have a 2nd burn.” area. IE they had done planning to insure that the 2nd burn would not provide a hazard to ISS, when the vehicle ended up in the wrong place this was no longer within the planned parameters and thus they did not have permission to do the second burn. Its entirely possible that there was enough propellant and they could have done the 2nd burn… but the longer stage 1 burn had moved the orbit enough that they ran out of tolerance to stay within NASA’s agreed-ed upon safe box for the 2nd burn.
There’s more information on NASASpaceflight L2. Chris will be doing a writeup once the dust settles and the analysis has been done.
In short: real journalism, learn it.
Trent,
But its so much more fun to Monday morning quarterback and second guess everyone 🙂
Yes, let’s let the dust settle and see the full report. For now let’s just hope the rest of the mission goes well so the critics won’t have any more ammo to attack SpaceX with.