Feb 07 2018

The Loss Of The Falcon Heavy Core Booster Shouldn’t Be Ignored

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.

Permanent link to this article: http://www.xadara.com/the-loss-of-the-falcon-heavy-core-booster-shouldnt-be-ignored/

2 comments

  1. I havent read your whole article, but I’m pretty sure that all orbital insertions (rocket launches) have controlled explosives rigged inside them, in case the entire vehicle turns toward populated areas and are destroyed. From my understanding there’s a man from the military, a range officer or whatever, that has his finger on the button. The same thing must be true for retrograde propulsion landings.
    The center core not only was an unflown booster but it is a completely new design. One detail I heard is that there wasn’t enough fuel to ignite the engines for the landing burn. That is not a serious design issue.

    1. Hi there. Thanks for commenting.

      I do mention in the article about the Range Safety Officer – the person in charge of destroying a wayward booster. Probably wasn’t as clear as I should have been on that point, but oh yes, I am aware of that person. If you notice I do mention the destruction of the booster for safety reasons, but there could be, and have been in the past, situations where a booster destroyed by RSO caused damage thanks to its location and trajectory at the time of the abort and booster destruction.

      Regarding the core booster itself, I’m guessing it would have been the most recent Falcon 9 design – hardly new, just a revision as SpaceX has continually revised the booster. In this case, this is supposed to be the final state of the Falcon 9, the version that is supposed to require the least maintenance for re-flight, the most reliable yet, etc… Not a completely new design, but regardless that doesn’t change the failure, which I’m not being as critical about as many think, only showing that is an issue to perform such – the BFR plan requires this, with people on board, for the “airline like service” idea. Risky, to say the least, no matter how far along the technology develops.

      Lastly, regarding the loss of fuel, I have seen this as well from a few outlets, but in most cases I simply read that it had “failed to ignite” without cause – however, stating that other engines were firing means fuel was available, so I am inclined to believe fuel on the vehicle was good for landing (also the booster also reportedly had a pretty solid explosion upon crashing, apparently, which you wouldn’t get without reasonable fuel reserves.) The lack of concise information is one of my major criticisms of SpaceX, in that they do not directly report what actually happens when things fail, leading to constant speculation, and most information being reported by rather biased specialty news sites, or by fans on social sites like Reddit.

      Lastly, I never intended to make it seem like this was a design issue inherently, but a side effect of the law of averages – it’s inevitable an engine would fail, and will fail again, on a landing attempt. It’s not a flaw in the machine inherently but a rather risky failure mode that is something I’m not comfortable with, and I don’t think others would be either with the aforementioned airline-like BFR flights being something now proposed in place of the original ITS concept.

      Thank you for commenting 🙂

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