Quote from: Robotbeat on 10/08/2017 12:47 amAnd yeah, I think it's pretty reasonable for BFR to achieve 99.99% reliability long-term, provided it can get anywhere near the cost figure it's shooting for. Sure...only 500 times better than F9 with 10 times the complexity.
And yeah, I think it's pretty reasonable for BFR to achieve 99.99% reliability long-term, provided it can get anywhere near the cost figure it's shooting for.
Quote from: Lee Jay on 10/08/2017 03:46 amQuote from: Robotbeat on 10/08/2017 12:47 amAnd yeah, I think it's pretty reasonable for BFR to achieve 99.99% reliability long-term, provided it can get anywhere near the cost figure it's shooting for. Sure...only 500 times better than F9 with 10 times the complexity.Yes, because I expect BFR to fly >500x as many times as Falcon 9.
Quote from: Robotbeat on 10/08/2017 10:17 pmQuote from: Lee Jay on 10/08/2017 03:46 amQuote from: Robotbeat on 10/08/2017 12:47 amAnd yeah, I think it's pretty reasonable for BFR to achieve 99.99% reliability long-term, provided it can get anywhere near the cost figure it's shooting for. Sure...only 500 times better than F9 with 10 times the complexity.Yes, because I expect BFR to fly >500x as many times as Falcon 9.You're talking about ~10k flights per year, how should that happen if BFR doesn't prove to be extremely reliable and cheap beforehand?
Loads of people saying it should have a LAS, but no suggestions on how it could actually be done? Presumably because no-one has yet thought of a way of doing it? Is it even physically possible? All very well saying it should have one, but if having one means the craft never gets made because its either impossible or so hugely expensive, or make the craft useless for its intended purpose, then making it s a requirement is pointless.Musk has said it won't have one. I guess he may have thought it through.
Musk has said it won't have one. I guess he may have thought it through.
In the medium term a Dragon has no place in a BFS architecture. It means carrying a vehicle with plenty of hypergolic propellant. If they want a mobile pod for local actions they would build one based on the BFS RCS-thrusters, maybe a smaller version. It runs on methalox and can be refueled from the BFS main tanks. A Dragon would not be a good match. Such a vehicle needs an airlock. Dragon is designed around the ability to reenter. It has a quite small internal volume due to the cone shape.
Quote from: KelvinZero on 10/10/2017 01:49 pmQuote from: guckyfan on 10/10/2017 12:04 pmIn the medium term a Dragon has no place in a BFS architecture. It means carrying a vehicle with plenty of hypergolic propellant.Please have that conversation here instead: https://forum.nasaspaceflight.com/index.php?topic=43438.0...in fact I will quote it there and reply to it there now.Why there? I am in no way talking about a LES-system but my understanding was that Dragon could become a utility vehicle around BFS. I argued that Dragon is not good for that purpose.
Quote from: guckyfan on 10/10/2017 12:04 pmIn the medium term a Dragon has no place in a BFS architecture. It means carrying a vehicle with plenty of hypergolic propellant.Please have that conversation here instead: https://forum.nasaspaceflight.com/index.php?topic=43438.0...in fact I will quote it there and reply to it there now.
In the medium term a Dragon has no place in a BFS architecture. It means carrying a vehicle with plenty of hypergolic propellant.
Quote from: JamesH65 on 10/10/2017 09:57 amMusk has said it won't have one. I guess he may have thought it through.I guess he completely goes for reliability of the system. It has to be extremely reliable to work for a very large number of reuses. So he puts engineering for reliablity ahead of a LAS.I can only think of one reasonable way to have a LAS for the whole crew of 100. Carrying a LAS all the way to Mars is not an option IMO, too much of a weight penalty. So have a separate vehicle, probably a tanker with a capsule on top that crams in 100 people and has its own abort propulsion. That tanker may lose up to 100t of propellant capacity but it would be enough to top off the tanks and bring the passengers. Maybe another launch but launches are cheap. That way the ship can be mostly fueled before passengers arrive.
By the way, a LAS would add its own risk factors. For instance, if the LAS on Orion fails to separate, the crew dies.And commercial airlines are so safe that if you added a LAS or ejection seats to them, the extra risks would greatly outweigh the abort advantages, and you'd REDUCE overall safety.Again, for those in the back:If BFR is as reliable as Musk wants it to be, adding a LAS would REDUCE safety.
Its LES is pretty much the engines on the bottom of the ship, you can't have an escape system that large.