The fastest way to dump propellant is though a functioning rocket engine – safer, too.
Quote from: HMXHMX on 10/07/2017 05:32 am........BFS of course, even at maximum emergency thrust, neglecting other issues, does not have any significant thrust left over to escape a fireball.
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Quote from: speedevil on 10/07/2017 12:38 pmQuote from: HMXHMX on 10/07/2017 05:32 am........BFS of course, even at maximum emergency thrust, neglecting other issues, does not have any significant thrust left over to escape a fireball.The BFS might not be able to outrun a fireball. But if separate from the booster and all engines firing at the max. Could the BFS ride out the shock wave with the retro burn shielding the BFS?
Quote from: Zed_Noir on 10/07/2017 09:50 pmQuote from: speedevil on 10/07/2017 12:38 pmQuote from: HMXHMX on 10/07/2017 05:32 am........BFS of course, even at maximum emergency thrust, neglecting other issues, does not have any significant thrust left over to escape a fireball.The BFS might not be able to outrun a fireball. But if separate from the booster and all engines firing at the max. Could the BFS ride out the shock wave with the retro burn shielding the BFS?Sure.Not being able to outrun a fireball doesn't mean your vehicle is dead.You'd need careful calculation to work out the risks of various sorts of damage and consequences.Thermal damage - does the fireball directly or indirectly (radiant heat) overheat and damage anything.Propellant damage - does fuel, oxidiser, or a combination of the two, splashed or gaseous on your craft do bad things, from prompt explosions to fire later.Fragmentation - what's directly damaged by fragments.Control - do you have enough control authority to remain pointed in a safe direction.Landing - are your sensors and available landing pads in good shape to get safely down.Amongst others.
helium COPV's...I believe the BFB will not use these?
Quote from: octavo on 10/08/2017 02:01 pmhelium COPV's...I believe the BFB will not use these?Correct.
Since it mostly likely would fly with 25 or so people on board during early missions they could use a couple of Dragon capsules as an escape pod similar to how Rockwell proposed using an Apollo capsule as an escape pod on the shuttle.The real question can a Dragon V2 handle being fired out sideways from the ship's cargo bay?
An interesting concept. The first here that would actually get the passengers out of harms way of a fireball. But getting away is the easy part. I am afraid. Does it has a heat shield to abort in high velocity situations on earth assent or is it just good for abort from BFR? Even harder, how does it land on earth, Mars or the moon? @edit: What is exactly the mission envelope the LAS should work? Only for the BFR phase of the flight on Earth and only for BFS ascent on the Moon and Mars? How about the vertical lending part when under power? What are the expected failure modes this LAS should be able to handle? Engine out or fuel tank rupture? It seems we need to answer this question first before starting on a design. I know its boring, but thats how engineering works (successful engineering I might add). First be absolutely clear what exactly you want before starting to find solutions.For the record: I expect that a useful LAS is impossible for BFR/BFS that works on Earth, Moon and Mars, but lets at least try to design one since my working hypothesis is impossible to prove. If against all odds we figure out how to do a LAS that works for the three bodies, we need to figure out how much mass it requires and then the question will be: is it worth it for flights to the Moon or Mars? How does it impact the maximal number of passengers?
I don't think so. If it's not as reliable as, say, a private jet which doesn't have a LAS, then it won't be viable from a cost point of view anyway.And LAS add their own failure modes while also reducing the payload margin that can be used for increasing robustness of the vehicle.
I stated in the other thread that the point to point system is in much greater need of a LAS than the space systems, both statistically and perceptively.Could the BFS just fly with nearly empty tanks so that it has a T/W >1? The booster is huge and people are relatively light. The consensus seems to be that firing the vacuum raptors in the atmosphere could damage them from flow separation but they would still provide thrust. From what I've seen the thrust to weight isn't actually that far off on the ship, so it could still carry landing fuel and some additional delta-v for the main mission even keeping weight down.Does that seem possible?