The Falcon Heavy Test Flight yesterday was a near flawless success, well above the expectations of many people who really know rocketry, and many of those involved with the rocket itself, including Elon Musk.
There was, however, one problem with the flight, and that was with the attempted recovery of the core booster.
It isn’t the fact that the landing failed, but the method in which it is reported to have failed – apparently engines on the core stage didn’t re-ignite when it came time for the landing burn. Instead of being able to slow down and land on the drone ship, the stage slammed into the ocean and was destroyed.
This shows a major risk factor with stage recovery that I had rather recently thought about – what if the stage successfully makes a return burn, but fails to ignite for the actual landing? Sure, this time it was on the drone ship, but what if it had been one of the two side boosters?
Can you imagine an uncontrolled rocket stage coming back towards the cape? While certainly range safety would still have an authority to destroy the wayward stage, the fact remains that such a scenario on a returning stage could well result in it (or debris from it’s destruction by range safety) crashing somewhere else on the cape, away from the actual landing zones – that very well could be a populated area. The Falcon 9 boosters make multiple burns to slow themselves down then begin to fly back to the cape for landing, and depending on the burn, if it fired for too long or didn’t fire at all, you could have a stage fall quite short or fly too far.
That’s a worst case scenario, though, but is still a possibility. A secondary parachute system on the boosters might be useful, but at this stage I don’t see how they would implement it, given the high energies stages come down with and the very late time frame the on-board systems would have to react to such.
Don’t downplay the booster engines failing to ignite. While the rest of the flight was a major success, this is something that could, if it happened again during a booster recovery attempt, cause some serious damage. It’s still unlikely given the success rate of booster recovery and the Merlin engines, but it’s not impossible – it happened yesterday, and can easily happen again. Given the law of averages, it will.
Update: I also want to note that this apparently was a new booster, while the two side boosters were previously flown stages. Let’s note that a new set of engines had a failure – not re-flown ones. As I said in my article “Flight Proven Means Nothing To Me” however, this means minimal in the long run – a new engine can fail just as readily as an old one, as well as the other way around.
On a side note, I’d like to point out that “engine failure” was my criticism of the original ITS proposal back in September 2016 – the criticism that many people wanted to give me hell over, in saying that “redundancy” would prevent such from being an issue.
I didn’t bring up recovery during that discussion, but this incident shows that “redundancy” did no good here – the engines that had to work didn’t, and the recovery failed.
It didn’t ruin the mission by any means, but it’s not something to be ignored.