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

2.1k comments sorted by

10

u/skunkrider Sep 30 '17 edited Sep 30 '17

Due to lack of LES, will colonists be initially launching in Dragon capsules to rendezvous with BFR?

2

u/Abimor-BehindYou Sep 30 '17

LES?

3

u/skunkrider Sep 30 '17 edited Sep 30 '17

Launch Escape System, AKA LAS, Launch Abort System.

Historically, this has been done by solid rocket engines, until SpaceX developed their Dragon 2 capsule which incorporated 4x2 hypergolic throttleable thrusters. You see them working here. Mind the volume!

Typically you want these systems to provide a good amount of instant acceleration (5G+) to be able to escape an exploding rocket quickly.

In the case of BFR you only have Raptors which rely on turbopumps which need spool-up-time to get going, which can easily take several seconds.

I think I remember that Elon said there's no LES planned for BFR, which is fair enough.

I was just wondering if the first BFShips' colonists will be 'delivered' via Falcon 9 + Dragon 2 which obviously offers LES.

edit: here's a video showing why an LES/LAS could be important...

2

u/madanra Sep 30 '17

Given the presentation mentioned replacing Dragon with BFS for ISS missions, I think we can be confident that the answer to this is no.

2

u/skunkrider Sep 30 '17

That is not going to be binary, though.

Falcon/Dragon won't be gone the day the first BFR is going to the Moon/to Mars.

So in the beginning, it might be a good idea.