Quote from: edkyle99 on 02/26/2015 05:46 pmBoosters carrying more propellant than core makes no sense unless crossfeed is used, which is apparently not going to be the case. There is no performance advantage. If anything, there is a performance penalty. I am not an expert, so could you elaborate more on why this would not provide any performance advantage? Center core will be throttled down = it feels like the more propelant you have in boosters, the higher delta V you can give to the center core.
Boosters carrying more propellant than core makes no sense unless crossfeed is used, which is apparently not going to be the case. There is no performance advantage. If anything, there is a performance penalty.
The longer-burning boosters would cause the core to burn more propellant before staging.
Quote from: Robotbeat on 02/26/2015 05:32 pmQuote from: edkyle99 on 02/26/2015 05:29 pmQuote from: Robotbeat on 02/26/2015 02:01 pmI would give you 20:1 odds and still take the bet. The boosters are stretched, we have it from multiple sources.Who? - Ed KyleSpaceX multiple times and Jim.Maybe all three are stretched from v1.1. That would make sense. Boosters carrying more propellant than core makes no sense unless crossfeed is used, which is apparently not going to be the case. There is no performance advantage. If anything, there is a performance penalty. Meanwhile, we have these images to ponder. - Ed Kyle
Quote from: edkyle99 on 02/26/2015 05:29 pmQuote from: Robotbeat on 02/26/2015 02:01 pmI would give you 20:1 odds and still take the bet. The boosters are stretched, we have it from multiple sources.Who? - Ed KyleSpaceX multiple times and Jim.
Quote from: Robotbeat on 02/26/2015 02:01 pmI would give you 20:1 odds and still take the bet. The boosters are stretched, we have it from multiple sources.Who? - Ed Kyle
I would give you 20:1 odds and still take the bet. The boosters are stretched, we have it from multiple sources.
Quote from: edkyle99 on 02/26/2015 09:03 pmThe longer-burning boosters would cause the core to burn more propellant before staging.Can't the core be throttled even more? Or some core engines may even be shut down to save fuel? But I think I see your point - adding more fuel to boosters makes them carry their own weight for a longer period and the goal is to get rid of the boosters as soon as possible.
The first mission is really a demonstration flight. It's there to prove that Falcon Heavy will work. That it will deliver the payload that we say it can, and we don't have a primary customer for it, but we are likely to have several smaller secondary satellites on-board that will do a variety of things, and if we get lucky, maybe there will be a big satellite at the last minute that wants to buy the flight at a reduced price.
Quote from: Robotbeat on 02/26/2015 02:01 pmI would give you 20:1 odds and still take the bet. The boosters are stretched, we have it from multiple sources.I'll take the bet. 20:1 odds are pretty good!I think unstretched boosters makes sense given SpaceX's incremental development philosophy, plus the fact that FH is already rather late.FHv1: unstretched boosters, no crossfeed, identical tanks, interstage & grid fins for all cores, "just" stage interconnects, core throttling, and everything else which is "essential" for FH. Get 'er flying ASAP!FHv1.1: stretched boosters, new interstage for boosters, grid fin relocation, etc. Probably all in development, just not on the critical path for first flight anymore. Low-hanging fruit.FHv1.2: crossfeed. Developed only if/when a customer has need, may be bypassed by current events....FHv2: S2 reusability? (A man can dream!)That seems like a nice incremental development path, assuming that all three of FHv1, FHv1.1, FHv1.2 offer monotonic performance improvements over F9R.
Question: how much will the increased thrust of the Merlin 1D+ affect the benefits of crossfeed? If the side boosters have more thrust, you can throttle down the center core more without being eaten up alive by gravity drag, and the benefits of crossfeed should be smaller.
Ok, I'm aware this sound insane from a risk standpoint. But what if you not only throttled down the core engines but actually shut down the center engine as well? They've had a lot of experience now re-lighting it, just not while the other ones are running. So you throttle the core mains to say 80% and shut down the center engine while the boosters keep burning at 115%. Now you'd have almost half the fuel left in the core when you stage. That's significant. If the stage can survive this thrust differential at Max Q, and the additional gravity losses...hmm, needs more work...
Quote from: cuddihy on 02/28/2015 04:14 amOk, I'm aware this sound insane from a risk standpoint. But what if you not only throttled down the core engines but actually shut down the center engine as well? They've had a lot of experience now re-lighting it, just not while the other ones are running. So you throttle the core mains to say 80% and shut down the center engine while the boosters keep burning at 115%. Now you'd have almost half the fuel left in the core when you stage. That's significant. If the stage can survive this thrust differential at Max Q, and the additional gravity losses...hmm, needs more work...If engines aren't needed, why have them at all? Thrust costs money.It seems more likely that the rocket is designed to use, and need, the thrust. - Ed Kyle
I'm curious - does Falcon Heavy automatically fall under the Reusable Rockets category?Is there any mission type where none of it gets retrieved or re-used?
Yeah, anything which needs its full performance. None really exist, yet, except maybe some high energy missions like New Horizons.