Stage 2 LOX Quick Disconnect (QD) Failed to Disconnect at Liftoff. This resulted in the LOX QD panel (with QD) and ~2” of LOX fill line separating from vehicle.
kevin-rf - 15/6/2007 7:51 PMQuoteSpacemanSpiff - 15/6/2007 2:27 PMDemo Flight 2 DARPA review report is posted. See website.I assume you mean on the http://www.spacex.com site refering to http://spacex.com/F1-DemoFlight2-Flight-Review.pdfInteresting, I wonder how serious some of those eight reported anomalies are. Having the quick disconnects fail and the mix wrong sounds a little scary to me. Sounds like they learned quite a bit on this launch.
SpacemanSpiff - 15/6/2007 2:27 PMDemo Flight 2 DARPA review report is posted. See website.
nobodyofconsequence - 15/6/2007 11:05 PM"Merlin shutdown will also be initiated at a lower acceleration."Insurance they won't bump Stage 2 again. Does this mean they run Stage 1 dry? Or is Merlin 1C throttle-able?
It is worth noting the Elon himself said throttling down is rough on the engine and will reduce its life.
JesseD - 18/6/2007 4:04 AM-- Stage 1 Trajectory PerformanceThe computer was given a wrong propellant utilization file, which messed up the fuel mixture, which lowered thrust, which caused the first stage trajectory to degrade. A simple fix; just copy the right file.
-- Stage Separation Re-contactThe problem wasn't the interstage, it was the rotational moment of the whole stack. This, I figure, was caused by a number of factors and highly influenced by the Stage 1 Trajectory Performance problem. Being at a lower altitude than expected caused increased aerodynamic forces, which contributed to the rotation; I also heard that the shutdown transient of the Stage 1 engine was different than they had simulated. Now they have that data, they plan to be able to fix it by throttling down the Falcon before MECO. Fixing the trajectory problem (simple computer fix) should also fix the aero force problem, and this problem should go away. It's got to just KILL Elon that if they had loaded the correct engine config file, the whole flight may have been picture perfect!!!- Jesse
pippin - 18/6/2007 4:34 AMNot sure, if it's that easy...QuoteJesseD - 18/6/2007 4:04 AM-- Stage 1 Trajectory PerformanceThe computer was given a wrong propellant utilization file, which messed up the fuel mixture, which lowered thrust, which caused the first stage trajectory to degrade. A simple fix; just copy the right file.Read carefully. They did NOT state, that they know what the correct file looks like. I would suspect they figured out that it was wrong and now have to go back to testing to find a better configuration.
Quote-- Stage Separation Re-contactThe problem wasn't the interstage, it was the rotational moment of the whole stack. This, I figure, was caused by a number of factors and highly influenced by the Stage 1 Trajectory Performance problem. Being at a lower altitude than expected caused increased aerodynamic forces, which contributed to the rotation; I also heard that the shutdown transient of the Stage 1 engine was different than they had simulated. Now they have that data, they plan to be able to fix it by throttling down the Falcon before MECO. Fixing the trajectory problem (simple computer fix) should also fix the aero force problem, and this problem should go away. It's got to just KILL Elon that if they had loaded the correct engine config file, the whole flight may have been picture perfect!!!- JesseThe aero loads are ONE problem. Fix: see above.The turbine issue may not be that easy to solve. I suspect them to shut down the engine rough for a reason. Throttling is not that simple (SpaceX themselves are claiming cavity problems in this post) and I don't think they have any engine-off pitch/yaw control. Maybe they can vent leftover LOX through the engibne or something like that to compensate for the momentum but I believe they will spend one or two nights fixing that one...
I think they are on a good learning curve and they have achieved quite something but all the "no problems, easy to fix" rhetoric is annoying. Especially, since if it were true it would really mean their quality management is really lousy letting them get away with so many simple problems, and we don't wanna suspect that, don't we?
This anomaly is two-fold. First, an incorrect propellant utilization file was loaded into the engine computer. This error caused the engine mixture ratio to be lean on lift-off and rich at altitude. Therefore, thrust was slightly lower than intended early in the flight, resulting in increased gravity losses and causing the first stage trajectory to be slightly lower and slower than predicted. SpaceX has adjusted its configuration management system to ensure that this will not recur.
JesseD - 18/6/2007 4:03 PMWell, I don't want to be annoying! In my opinion, it is a GOOD THING that all of these little things happened as they did. it's clear that SpaceX has done a lot of work, but it's also clear that when you put together a whole new rocket from scratch as fast as they did and run the whole operation with as few people as they do, you're not going to be able to forsee as many possible problems as NASA. ...This is where the old.space companies shine, planning for unforseen circumstances and working around them.
Pippin: I agree with your agreement - and your critique. Although a start up needs to be somewhat brash and appear confident to sell themselves, the reptetitive restatements that "ok, NOW we have it all figured out..." get extremely tiring and diminish their credibility.
As for "old.space", I'll also toss in the example of Delta III. They made a major error and forgot to correctly model the rotation modes of the vehicle. This wasn't a problem before with Delta II because the strap ons didn't have any TVC and therefore didn't impart any torque to that mode. However, Delta III used active control of strap ons for roll control, exiciting that mode and leading to failure. Even with all of the experience and heritage at Boeing, this seemingly obvious issue got missed.
And as a piece of trivia - but not implying any connection - among the entries on the resume of Jim Maser, recently departed President/COO of SpaceX (http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=5574&start=1), is his stint as Chief Engineer on Delta III.
JesseD - 18/6/2007 9:03 AM ... This is where the old.space companies shine, planning for unforseen circumstances and working around them. ...
Strongly disagree.
Yes old.space shines, but for different reasons. The idea was to have any kind of RELIABLE space launch services, at ANY cost profile. This is NOT a bad thing ever.
With new.space, the idea is how much can you get away with at cutting the corners, because too much cost gets carried along and you lose your cost advantage over old.space (if there is one). The game is to intentionally cut corners - lots of them!
So they do a "good enough" try, and refine through multiple tries, sometimes getting it wrong.
In the end they may not get enough this way, and the cost advantage may be too marginal to ever justify the loss on the blown launches. But the only way they can shed cost in the structure is to remove too much, find what's absolutely essential, and put back whats minimally needed.
Leaving out the baffles was simply manufacturing cost reduction and weight reduction. Turns out it was too risky, as was non-regen Merlin. They are trying for a sustainable business advantage, not simply to be a "me too!"
Vehicle Development Path-Demo flights Merlin 1A ablative engine Kestrel-1 upperstage engine Skin/stringer fairing ~700 pounds to orbit-Next 3 flights De-tuned Merlin 1C Regen engine Kestrel-2 upperstage engine Skin/stringer fairing ~1200 pounds to orbit-2009—Falcon 1E Full Merlin 1C performance Longer first stage ~1800 pounds to orbit
Zond - 23/6/2007 5:22 PMThis SpaceX presentation has some interesting info.For the next flight they are going to replace the Merlin 1A with a 1C and replace the Kestrel 1 engine with a Kestrel 2 engine.
