Quote from: meekGee on 11/05/2015 02:23 pmEDIT: do you have a reference to Musk's comment? I remember something vaguely, but don't remember the context.Quote from: elon twitterBase is 300 ft by 100 ft, with wings that extend width to 170 ft. Will allow refuel & rocket flyback in future.https://twitter.com/elonmusk/status/536263260056850432
EDIT: do you have a reference to Musk's comment? I remember something vaguely, but don't remember the context.
Base is 300 ft by 100 ft, with wings that extend width to 170 ft. Will allow refuel & rocket flyback in future.
I remember probably in the same presentation where he mentioned flyback he also said the Merlin engines have no meaningful limitation to their lifespan. After 40 cycles a few highly stressed components must be exchanged. He clearly was not worried about spending engine cycles.
Quote from: guckyfan on 11/05/2015 03:12 pmI remember probably in the same presentation where he mentioned flyback he also said the Merlin engines have no meaningful limitation to their lifespan. After 40 cycles a few highly stressed components must be exchanged. He clearly was not worried about spending engine cycles.A related question regarding engine cycles--for a flyback, how many of the 9 engines would be used? Maybe just one?
....There are inaccuracies above, and aero losses are different, and the dV won't be the same since you can optimize for range instead of for height and altitude, etc...
Quote from: Lars-J on 11/04/2015 10:45 pmQuote from: meekGee on 11/04/2015 09:40 pmI am pretty sure that once barge landing is routine, they will refuel on the barge and fly back.So you get rapid reusability, plus no fly-back penalty.Doubtful, I don't think that it will ever happen with F9, you would need a significantly redesigned launch vehicle. The legs cannot handle the propellant mass, and instead of a flat landing surface you need it also to be an operational launch pad. With all the LOX/RP1 and other consumables, and equipment to support it. And the man power. The people at the pads aren't just spending their work hours twiddling their thumbs. Boating it back to shore will always be cheaper.I must admit I was seriously shocked when Elon Musk mentioned flyback from the barge. I still can't believe it makes sense.
Quote from: meekGee on 11/04/2015 09:40 pmI am pretty sure that once barge landing is routine, they will refuel on the barge and fly back.So you get rapid reusability, plus no fly-back penalty.Doubtful, I don't think that it will ever happen with F9, you would need a significantly redesigned launch vehicle. The legs cannot handle the propellant mass, and instead of a flat landing surface you need it also to be an operational launch pad. With all the LOX/RP1 and other consumables, and equipment to support it. And the man power. The people at the pads aren't just spending their work hours twiddling their thumbs. Boating it back to shore will always be cheaper.
I am pretty sure that once barge landing is routine, they will refuel on the barge and fly back.So you get rapid reusability, plus no fly-back penalty.
Quote from: guckyfan on 11/05/2015 07:02 amI must admit I was seriously shocked when Elon Musk mentioned flyback from the barge. I still can't believe it makes sense.Neither can I.Perhaps it is a proxy for some other capability that they are thinking about.
I must admit I was seriously shocked when Elon Musk mentioned flyback from the barge. I still can't believe it makes sense.
Quote from: meekGee on 11/05/2015 10:27 pm....There are inaccuracies above, and aero losses are different, and the dV won't be the same since you can optimize for range instead of for height and altitude, etc...(My bold)A small point. As well as supplies of prop and other consumables for the returning vehicle, the barge will need to carry some nose fairings to be attached for the flight back. I'm not sure if the vehicle would get through max Q without one.More importantly, as always, the driver for this is economics. There's no doubt technically that it could be done like you describe. But obviously it must be cheaper to recover and reuse the vehicle using this extra sea based infrastructure than expend it. In order for this to be worthwhile, the FH flight rate will have to be high. I think it's unrealistic to expect such rates in the near future. Just because Musk mentioned the possibility of flyback, it doesn't mean they're going to do it. Once upon a time both F9 stages were going to be recovered, now that's on the back burner. The problem is that the three core design complicates recovery. And extra complications mean extra cost.I'm strongly in favour of RTLS as being the cheapest solution to re-use because of its operational advantages. Recovering the side cores will be a good saving in itself.
Quote from: douglas100 on 11/05/2015 11:00 pm...Just because Musk mentioned the possibility of flyback, it doesn't mean they're going to do it. ... That's a pretty high bar for speculation on an internet forum...
...Just because Musk mentioned the possibility of flyback, it doesn't mean they're going to do it. ...
To me it doesn't make any sense to launch off the barge to return to the Cape or Boca Chica. The barge/ship is only about 200-300 miles off shore. At 20-30 knots, they can be back at either launch site in less than a day. While on the way back, a crew could inspect the engines and structure. Then once back go to the hanger for refitting or replacement of any damaged components. It would be less stress on the engines and structure of the rocket while allowing time for inspections. It would have to be done anyway, so just do it while getting back. Once back it would be that much less time for refueling, refitting, and relaunching. Now launching from sea back to the launch site will require equipment for manufacturing lox and storage for the kerosene needed. That would be extra expense.
Ok, I thought the ship/barge they landed on was self propelled.
Quote from: meekGee on 11/06/2015 01:09 amQuote from: douglas100 on 11/05/2015 11:00 pm...Just because Musk mentioned the possibility of flyback, it doesn't mean they're going to do it. ... That's a pretty high bar for speculation on an internet forum...Why? It's an obvious point. Musk has predicted a number of possibilities which haven't happened. I agree with your other points about trades and predicting the future. It seems to me that all you gain from fly back is time. There is no payload gain. So the trade is heavily influenced by FH flight rate. That's why I'm skeptical at this time about fly back.
Ok, I thought the ship/barge they landed on was self propelled. Even at 5-6 knots. It can travel 100 miles in a day. How far offshore are they now? I know the middle core on the FH would be further out, but still. Checking and refitting 3 cores will take some time. Ones that land back at launch site can be checked and readied while waiting on the 3rd core to get back. I just don't see the need to launch back and take a chance at further stressing or damaging the core stage.
Quote from: spacenut on 11/06/2015 04:39 pmOk, I thought the ship/barge they landed on was self propelled. Even at 5-6 knots. It can travel 100 miles in a day. How far offshore are they now? I know the middle core on the FH would be further out, but still. Checking and refitting 3 cores will take some time. Ones that land back at launch site can be checked and readied while waiting on the 3rd core to get back. I just don't see the need to launch back and take a chance at further stressing or damaging the core stage. Let's say 5 days in, 5 days out.Rapid reusability means one day turn-around at most, all included.So there's a disparity there.The only way to avoid the fly-back penalty and retain rapid reusability is fly-back. That's all.Maybe they won't (fly back) and then they have to give up either performance (if they fly the core back to shore), or turn around time and launch frequency (if they haul it back by sailing). Or operate some 10 barges following your suggestion.
Quote from: meekGee on 11/06/2015 06:12 pmQuote from: spacenut on 11/06/2015 04:39 pmOk, I thought the ship/barge they landed on was self propelled. Even at 5-6 knots. It can travel 100 miles in a day. How far offshore are they now? I know the middle core on the FH would be further out, but still. Checking and refitting 3 cores will take some time. Ones that land back at launch site can be checked and readied while waiting on the 3rd core to get back. I just don't see the need to launch back and take a chance at further stressing or damaging the core stage. Let's say 5 days in, 5 days out.Rapid reusability means one day turn-around at most, all included.So there's a disparity there.The only way to avoid the fly-back penalty and retain rapid reusability is fly-back. That's all.Maybe they won't (fly back) and then they have to give up either performance (if they fly the core back to shore), or turn around time and launch frequency (if they haul it back by sailing). Or operate some 10 barges following your suggestion.F9 will never have rapid reusability like that (a one day turnaround), which renders your point moot. A follow-on vehicle might, but is another discussion. So it will never be economical to fly back FH/F9 cores.
Quote from: Lars-J on 11/06/2015 06:47 pmF9 will never have rapid reusability like that (a one day turnaround), which renders your point moot. A follow-on vehicle might, but is another discussion. So it will never be economical to fly back FH/F9 cores.A) How do you know? B) If the follow-on vehicle is of the same class, then it's the same barge size, and so the discussion is equally validC) Musk had something in mind when he said what he said about fly-back. So irrespective if it pans out - which rocket do you think he was talking about?
F9 will never have rapid reusability like that (a one day turnaround), which renders your point moot. A follow-on vehicle might, but is another discussion. So it will never be economical to fly back FH/F9 cores.
I will also suggest that if flyback is/was in the plan, then barge use is not envisioned as some temporary hack, but a permanent conop, which matches the fact that they've built one for each coast.