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Investigation into Crew Dragon incident continues - SpaceNews.com
WASHINGTON — More than a month after a Crew Dragon spacecraft was destroyed in a test of its propulsion system, NASA and SpaceX investigators are still working to determine the cause of the accident and its implications for upcoming test flights.
In a May 28 presentation to the NASA Advisory Council's human exploration and operations committee, Kathy Lueders, manager of the commercial crew program at NASA, offered few updates on the progress of the investigation into the April 20 incident at a SpaceX pad at Cape Canaveral Air Force Station in Florida.
In that incident, SpaceX was testing both the Draco thrusters and larger SuperDraco abort thrusters in preparation for an in-flight abort test of the capsule that, at the time, was scheduled for the end of June. "An anomaly occurred during activation of the SuperDraco system," she said, but offered no details on what caused that anomaly.
[...] With the investigation ongoing, Lueders said the dates of both the in-flight abort test and the Demo-2 mission are under review. Assembly of the Demo-2 capsule continues, she said, although she said workers are keeping open the vehicle's propulsion system in case they need to make modifications as a result of the investigation. "They're making progress in a lot of the other areas while trying to keep, most particularly in the prop area, access to the systems that may need to be modified," she said.
She didn't give an indication of when that investigation will be completed. "You don't push your anomaly investigation team too quick," she said, stressing the importance for them to be "methodical" while working through all parts of the fault tree of potential causes.
(Score: 0) by Anonymous Coward on Thursday May 30 2019, @12:44AM
Yeah, I know there were "No Smoking" signs everywhere. "No sparks, no grinding, no open flames, no farting" on and on it went. But, I wanted a smoke. There was even a "No Bright Ideas" sign. So, sue me.
(Score: 0) by Anonymous Coward on Thursday May 30 2019, @12:50AM (3 children)
Traditionally, emergency escape engines are simple solid fuel, mounted on top - shielded from the explosion of stages by the spaceship with excellent fire resistance. But they are single-use, and they do not perform controlled landing.
Musk wanted reusability. The only way to achieve that is to use liquid fuel engines on the bottom (rim) of the capsule. That does the job, but the price is high. The fuel and the engines are too close to the crew. The fuel - hydrazine - is poisonous, burns easily. The engines are complex, and they do not start fast. The engines are not shielded from a fireball just below.
Musk is a showman. He wants a theatrical performance out of space travel. Sometimes his requests come close to safety margins. The cause of this explosion will be found and fixed, but let's hope we never need to test the escape system with crew, on an exploding rocket.
(Score: 2) by takyon on Thursday May 30 2019, @12:56AM
Crew Dragon is just a way to grab the available ISS Commercial Crew dollars. Starship is what will ultimately be carrying hundreds or thousands of people.
The capsule that exploded had landed on the water, and NASA wants a fresh one every time for crew (reused ones can send cargo to the ISS). If that turns out to be the source of the problem, then the astronauts will probably be fine.
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(Score: 3, Interesting) by ElizabethGreene on Thursday May 30 2019, @03:36AM
If we're second guessing that design decision, can we talk about Blue origin's far sketchier placement of the abort engine too? It's literally the coffee table in the middle of the crew cabin.
(Score: 0) by Anonymous Coward on Thursday May 30 2019, @09:22AM
Accusing Musk of compromising safety for the sake of being a showman is such extreme crap. This design has nothing to do with "showmanship." It is a technical decision made for good reasons: to share fuel with the maneuvering thrusters, and to avoid having to have a separate, disposable abort system. Every additional system on a rocket adds weight and complexity.
Hydrazine fuel has been used on rockets for decades. While the fuel itself is toxic, the astronauts don't drink it.
We still do not know the cause of the accident. It is still very possible that the explosion was due to damage and not a design flaw.
You can always tell who has an agenda, it's whoever is rushing to judgement and placing blame without any facts.
(Score: 5, Informative) by KilroySmith on Thursday May 30 2019, @02:30AM
>>> Musk wanted reusability.
Well, I doubt very much that the use of hydrazine had anything to do with reusability - I doubt that anyone has any need to reuse a crew capsule that's had to use it's emergency escape system. And hydrazine is going to seriously compromise the ability to quickly reuse capsules. No, if reusability was the goal, then solid rocket motors is where its at.
What Musk wanted was the ability to soft-land on, well, land. Throttling the liquid fuel engines would have given him that as a standard landing technique, rather than splashing the capsule in the ocean. It's not the current plan, and I don't know if Crew Dragon still has that capability, but the hydrazine engines are a legacy of that desire, not reusability.
(Score: 1, Informative) by Anonymous Coward on Thursday May 30 2019, @05:46AM
There is a great explanation of why SpaceX wend with their design here: Video: https://www.youtube.com/watch?v=0MaeHNU2660 [youtube.com] . Text version: https://everydayastronaut.com/abort-towers/ [everydayastronaut.com]
The short version: The solid fuel solution is typically used with abort towers which end up being disposable and hurting reuse and complicating the mission (one more separation stage). Rear thrusters with actual differential thrust based control need to be liquid fueled, and as a bonus can share fuel with maneuvering thrusters. Propulsive landings was also considered during the design phase, but is currently not planned. Also, apparently the thermal cycling of solid fuel rockets would have been an issue when reused a lot.
(Score: 0) by Anonymous Coward on Thursday May 30 2019, @12:44PM
I heard it from some weed-smoking dude who said someone probably shot it with a high-powered rifle.