I got an unexpected chance to fly the Falcon Heavy again!
I learned there is a club called Sacramento Area Rocketry Group (
https://sargrocket.org/) that organizes monthly launches only an hour’s drive away. So last month I drove out to Sacramento and met some really great people. The event was well attended with a total of 144 launches.
So with a lot of attention by the crowd and some skepticism by the club’s rocket inspector, the Falcon Heavy passed the pre launch inspection and was announced as a “heads up flight”…
This launch was a FAIL. But this is a SpaceX project! So failure is only a problem if we do not learn from my mistakes. We learned several lessons…
1) Failure of center core ignition. You can see that the (B6-0) booster engines are working but not the (E12-0) center core.
This significantly diminished the assent. But
that allows us to observe a number of problems that might otherwise have remained hidden. This was a WIN!.
Failure analysis: Inspection of the center core igniter revealed a twist in the wire right at the head. The nicromium wire was fused where it touched, thereby shorting the igniter. This explains why the first launch countdown failed and a second countdown ensued…
Lesson learned: Use higher quality igniters with insulated wires for cluster launches. Quick Dip is not enough as a failure of this type would not have even turned up in a continuity check which I did not do.
2) An unplanned spin at launch. The entire rocket rotated 360 degrees before the boosters separated. Had the center core ignited, I would have expected the ½ roll that actually happens in the Falcon Heavy launch. Which is what we saw on the first successful launch.
Failure analysis: I think this was an artifact of problem 1. That the boosters were doing all of the work and if the core had ignited the roll would have been over a much longer flight path than what was observed.
Lesson learned: There is a design flaw that could be hidden with this excuse. The lower booster mount is attached to the plastic section of the core rocket that holds the fins but is ejected when the core rocket reverse recovery happens. This means that the upper booster mount and the lower booster mount are not fixed in a line but can swivel with respect to each other because the bottom section separates from the main body tube in flight. I realize the defect much earlier but booster mounts and centering rings were all built to this specification and I figured I’d just live and learn until I had the chance to build version two.
3) An unplanned ejection of the left booster nose cone.
Failure analysis: One of my goals in this build was to embody the SpaceX idea of re-usability so the only parts that I glued together are 1) the engine tubes to the centering rings, 2) the booster mounts to the body tubes, and 3) the fins to the second stage. Everything else is press fitted using electrical tape to add diameter to parts to add friction.
Lesson Learned: Tape the outside of the nose cone to booster body. I did this on the Death Valley launch but forgot to this time around. I should experiment with vent holes too.
4) Incomplete booster separation. The right booster upper mount did not release
Failure analysis: The magnetic repulsion of the right booster upper mount failed. I think this is a combination of friction inside the mount, inadequate magnetic force, and issue 2 above, which could result in booster mount binding due to the twisting of the booster relative to the core in flight.
Lesson learned: Fix issue 2 and increase the magnetic power of the booster release. There is a related problem when moving the entire rocket assembly. The entire assembly needed to be handled carefully as the magnetic booster attachment is not very strong. The booster attachment also needs to be stronger.
Conclusion:
A second flight repeated all of the above problems (this time with the center core failing to ignite because of a bad igniter (lesson learned: check continuity) and a booster mount broke. But at least some things worked; like the rear ejection recovery of the boosters. And a third flight (without the boosters) was successful, including ignition of the (C6-3) second stage! The whole experience was a blast.
The next SARG launch is March 28th, hopefully I'll have all of these issues resolved and I can try again.