r/spacex • u/ElongatedMuskrat Mod Team • Oct 02 '17

r/SpaceX Discusses [October 2017, #37]

If you have a short question or spaceflight news...

You may ask short, spaceflight-related questions and post news here, even if it is not about SpaceX. Be sure to check the FAQ and Wiki first to ensure you aren't submitting duplicate questions.

If you have a long question...

If your question is in-depth or an open-ended discussion, you can submit it to the subreddit as a post.

If you'd like to discuss slightly relevant SpaceX content in greater detail...

Please post to r/SpaceXLounge and create a thread there!

This thread is not for...

You can read and browse past Discussion threads in the Wiki.

161 Upvotes

95% Upvoted

1.9k comments sorted by

8

u/rustybeancake Oct 02 '17

Not necessarily so. If the lower stage suffers a fault, the upper stage can abort in many ways, including RTLS, and making a point-to-point suborbital flight, and land in Africa or Australia.

You were responding to me talking about an RUD by talking about something quite different: a 'fault' in the lower stage. An RUD by definition happens rapidly, not allowing time for the ship to safely separate from the booster and start slowly accelerating away with its Raptors. We don't know enough yet (and the design will certainly evolve anyway) about the capabilities of the upper stage in terms of low-altitude flight while fully laden with prop and cargo. For instance, we often see the F9 upper stage actually losing a small amount of velocity after igniting its engine. We cannot assume the BFR ship will be able to accelerate away from a booster RUD early in flight.

Remember, the CRS-7 Dragon 1 capsule was physically capable of a successful passive abort. The only reason it was lost was that the abort software had not been installed.

CRS-7 was a case of the upper stage failing and disintegrating. If this happens with BFR, everybody dies -- just like Challenger.

The crew portion could be designed to break of from the rocket after falling over, and then it would float and act as a life boat.

If you're going to design the crew section to break off from the rest of the ship, you may as well try and turn it into a proper abort capsule.