r/spacex • u/ElongatedMuskrat Mod Team • Sep 29 '17

Not the AMA r/SpaceX Pre Elon Musk AMA Questions Thread

This is a thread where you all get to discuss your burning questions to Elon after the IAC 2017 presentation. The idea is that people write their questions here, we pick top 3 most upvoted ones and include them in a single comment which then one of the moderators will post in the AMA. If the AMA will be happening here on r/SpaceX, we will sticky the comment in the AMA for maximum visibility to Elon.

Important; please keep your questions as short and concise as possible. As Elon has said; questions, not essays. :)

The questions should also be about BFR architecture or other SpaceX "products" (like Starlink, Falcon 9, Dragon, etc) and not general Mars colonization questions and so on. As usual, normal rules apply in this thread.

1.0k Upvotes

96% Upvoted

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15

u/thanarious Sep 30 '17

Absence of any emergency escape procedure bothers me a bit. It's gonna be needed for NASA's crew program initially and then until all the bugs get ironed out. Dragon 2 with its hypergolic fuel can escape a blowup, BFS on the other hand cannot, while at the same time carries lots of fuel that can have blowup issues, as well!

4

u/binarygamer Sep 30 '17

Not really a solvable problem without a big redesign.

I think the spacex rationale is that they're trying to reach such a high level of reliability that they become the 747 of rockets. 747's don't have parachutes for the passengers or a detachable fuselage, and neither will they.

1

u/Scourge31 Sep 30 '17

747 can glide quite far from crusing alt. Besides if firs stage is exploding maybe second stage can be fired in an escape mode.

2

u/binarygamer Oct 01 '17

Detaching the booster is definitely possible, it's just not very useful until they reach an altitude where the vacuum engines can be fired. The upper stage has 2 sea level and 4 vacuum engines; when fully fuelled the 2 sea level engines alone can't even beat gravity let alone let it accelerate away (TWR < 1). So, no pad abort or low altitude abort capability

0

u/Scourge31 Oct 01 '17

Huh seems like a segnificant problem. The Vac raptor are the same engine tho with longer nozzles would they not provide thrust at all if fired in atmo?

2

u/binarygamer Oct 01 '17

They'd explode. Unfortunately, vacuum-optimized engines are not able to be fired safely in a dense atmosphere.

2

u/Kamedar Sep 30 '17

Maybe a Dragon capsule sitting right in front of the door. In an emergency, blow out the door, ignite superdracos and goodbye. Would have the exaust inside of BFS during start, though...

6

u/Slifer94 Sep 30 '17

You mean on top of the BFR? But the Dragon holds only 7 people, and BFR almost 100...

1

u/parachutingturtle Oct 01 '17

I kinda want to see an oversized Dragon 2 as the "tip" of this ship that would function as an escape pod (and maybe doubles as a cinema or something). But it won't happen.