Ahhh…, those anomalies—those pesky anomalies. The worst kind of anomaly is when your spacecraft, in the process of being qualified for human spaceflight to the International Space Station (ISS), goes kaboom on the ground while preparing for a static firing of its launch escape system rocket motors. You know, kaboom, like this (sorry for the poor quality video—it’s all that’s presently available; there are some nasty words on the audio track.)
This happened yesterday, 2019-04-20, during preparation for a static firing (with the capsule strapped down to the ground) of the SuperDraco engines which provide the launch escape system of the Crew Dragon capsule, designed to transport crew to and from the ISS. Eight SuperDraco engines are mounted on the Crew Dragon, in pairs, and are used only in the event of a failure which requires rapid separation of the capsule from a failing booster. The launch escape system is intended to provide survivable abort from launcher failure anywhere from the launch pad to orbital insertion. In a normal mission, the SuperDraco engines are not used, and may be re-flown on subsequent flights with minimal inspection and refurbishment.
The SuperDraco engines are made largely through additive manufacturing (“3D printing”), and have been subjected to an intensive test programme. Here is a pad abort test from 2015, where the SuperDraco engines flew the profile of an abort from the launch pad (in this case, from a concrete pad instead of atop a booster). (This is one of the most Kerbal space flight tests I’ve ever seen.)
The last milestone which SpaceX was expected to have to demonstrate before launching the first crew was an in-flight abort test, where a Crew Dragon capsule would separate from its Falcon 9 launcher near the point of maximum dynamic pressure (max q), showing its ability to get the crew off a failing booster under worst-case conditions and return them safely to the sea offshore the launch site. The plan was to fly this mission in the next few months, re-using the Crew Dragon capsule successfully flown to and returned from the ISS on the Demo-1 mission in March, 2019.
It was this capsule which was being prepared for a test of the SuperDraco engines when everything went all splodey. The close-up video does not show the immediate consequences of the “anomaly”, but scuttlebutt says the capsule is “in pieces”. Observers at some distance from the test site saw a large orange cloud rising, which is the usual signature of release and combustion of hypergolic propellants as used in the SuperDraco engines.
Now, engineering is an art we learn from failure, and the reason we test is to learn the things we didn’t anticipate. That said, having the launch escape system, whose only reason for being included on the crew capsule is to save the astronauts’ lives in case something else fails, spontaneously blow the crew capsule (and crew, had any been on board) to smithereens, is about as bad as things can get. Serious thinkers about space flight safety have been asking for years whether the risks of carrying a high-energy launch escape system aloft on every flight might not actually be greater than flying without one; this incident might, in a rational world, spark discussion of this question, but the way to bet is that it won’t.
Unless it can be quickly determined that the failure was due to immersion of the capsule in salt water after its recent flight or something unrelated to performance of a new capsule, it seems likely this will result in delays to the scheduled Crew Dragon missions pushing the first crewed flight into 2020. NASA will probably have to buy additional Soyuz seats, as the Boeing crew capsule has also suffered delays due to problems in its launch escape system.
Here is Scott Manley’s quick take on the failure and potential consequences for SpaceX and commercial crew.