I read somewhere that the 4 strap ons burn with the core and transfer fuel to the core at the same time. Then they drop off and the core continues. Maybe they don't since they are smaller. However I read that years ago.
Purely FWIW, I think that RL-10C's thrust is too low for use on Falcon Heavy, even if you use cross-feed on the core and boosters. Staging is just too low and slow (because of RTLS performance limitations). Given that limitation and given that I think that Messrs Musk and Bezos would prefer to gouge out their own eyes than work together, the only hydrolox engine likely to be used on Falcon Heavy, IMHO at least (for a certain percentage of 'likely' anyway) is MB-60.
Quote from: Lobo on 02/16/2015 06:14 pmHopefully this is the right thread for this question.Has SpaceX said anything for sure about if they plan to upgrade LC-40 to handle FH?I'd assume they would, perhaps after 39A is up and fully functional becuase an upgrade to LC-40 like that will mean it'll be out of commission for awhile, and their manifest is packed right now. But I don't recall anything for sure about it, other than an old comment by Elon saying they might build a FH HIB at a 90 degree angle to the F9 HIB. I think that was before 39A was in the mix, so they could keep flying F9 while upgrading to FH. With 39A operational, I think they can just fly from there and tear down the F9 HIB and build the FH HIB thereOr will they just leave LC-40 launching F9 only?They have mentioned doing it, but plans change, and most of those comments were pre-39A acquisition. Now that they have 39A I don't see them being in a hurry do it. Perhaps never. But it also depends on two additional factors: - What will be the ratio of F9 to FH launches going forward? - How quickly will the Texas launch pad come online (presumably built to support FH from the beginning)
Hopefully this is the right thread for this question.Has SpaceX said anything for sure about if they plan to upgrade LC-40 to handle FH?I'd assume they would, perhaps after 39A is up and fully functional becuase an upgrade to LC-40 like that will mean it'll be out of commission for awhile, and their manifest is packed right now. But I don't recall anything for sure about it, other than an old comment by Elon saying they might build a FH HIB at a 90 degree angle to the F9 HIB. I think that was before 39A was in the mix, so they could keep flying F9 while upgrading to FH. With 39A operational, I think they can just fly from there and tear down the F9 HIB and build the FH HIB thereOr will they just leave LC-40 launching F9 only?
There is a simple question and simple answer in regards to Falcon Heavy cross-feed development.Q: Why would SpaceX develop cross-feed for Falcon Heavy?A: Because it is necessary to meet sufficient demand for customer payload requirements.It isn't going to happen just because. It would happen because it was necessary for enough paying customers that would justify the development cost, or a customer needed it badly enough to pay for it. And it isn't really clear that that is something that is going to happen in the next 15 years. SpaceX themselves won't need it: their long-term Mars plans revolve around BFR. Any reusable SpaceX BFR in 10-15 years would make a cross-feed FH obsolete.So who is the customer? And don't say Bigelow. At this point, it seems a rather long shot that he ever pulls together several hundred million dollars to develop, build and fly even one of the smaller modules, much less a larger one. And, again, if you're the *only* customer for a cross-feed Falcon Heavy, guess who gets to foot the tab for development?
1 - Could the M1D thrust upgrade and prop densification fully compensate no cross feed ?2 - Just because SpaceX mentioned a few times flying people to Mars on Falcon Heavy doesn't mean it's still in the cards. SpaceX has shown multiple times the ability to evolve its plans. Don't get hung up on words from many years ago if they don't get reinforced (with more words or actions).
http://www.spacex.com/falcon-heavy: Falcon Heavy was designed from the outset to carry humans into space and restores the possibility of flying missions with crew to the Moon or Mars.
The multi-core BFR posts are out of date. Musk has made fairly clear recently (in the MIT talk, I believe?) that the BFR will be single-core (though they were looking at multi-core before), I think due to operational reasons.
[–]FoxhoundBat 12 points 20 minutes ago In order to use the full MCT design (100 passengers), will BFR be one core or 3 cores?[–]ElonMuskOfficial 6 points a minute ago At first, I was thinking we would just scale up Falcon Heavy, but it looks like it probably makes more sense just to have a single monster boost stage.
Quote from: Robotbeat on 02/17/2015 06:06 pmThe multi-core BFR posts are out of date. Musk has made fairly clear recently (in the MIT talk, I believe?) that the BFR will be single-core (though they were looking at multi-core before), I think due to operational reasons.It was at the reddit AMA :Quote from: https://www.reddit.com/r/IAmA/comments/2rgsan/i_am_elon_musk_ceocto_of_a_rocket_company_ama/cnfpn7r[–]FoxhoundBat 12 points 20 minutes ago In order to use the full MCT design (100 passengers), will BFR be one core or 3 cores?[–]ElonMuskOfficial 6 points a minute ago At first, I was thinking we would just scale up Falcon Heavy, but it looks like it probably makes more sense just to have a single monster boost stage." but it looks like it probably makes more sense "Hardly conclusive. I wouldnt dissmiss the tri core concept altogether based on a triple disclaimed sentence.
When will people stop thinking/stating with certainty that anything is CLEAR in the future, especially 10-15 years hence? In the year 2000, would you or anyone have been certain that we'd be where we are in space launch business in 2015? Stop, please. (You don't have a clue. None of us has a clue.)
Has anybody seen any recent information on whether or not SpaceX will develop a larger fairing for FH? This to me seems like another item that would only be paid for if a customer wants it, but it also seems like a much cheaper upgrade than cross-feeding.
If you go full throttle on the core and the two boosters you are hauling the mass of all three until you run out of propellant. If you throttle back on the core it still has propellant after you dump the mass of the boosters.
I thought of perhaps another way to do full cross-feed without affecting the bottom of the rocket at all. The boosters are taller than the core stage. You could arrange for each booster to have two LOX tanks and two kerosene tanks, one set half the size of the other. The smaller kerosene tank sits above the main kerosene tank, and significantly, the bottom of the smaller booster kerosene tank sits above the top of the core kerosene tank. It drains into the core kerosene tank by gravity feed. Similarly, the bottom of the smaller booster LOX tank sits above the top of the core LOX tank, and drains by gravity feed as well. Note that gravity feed is fairly powerful, as the accelerations before booster burnout are over 3G.This scheme is perfect cross-feed, but with the added weight of two more tank bulkheads and the cross piping and unions. No special lines are needed to blow the cross piping clear of propellant before closing the valves and disconnecting. The pressurization system of the booster propellant tank can positively drain all the fluid into the core tanks before separation.Given that at separation you'd have nearly full core tanks, the propellant burn before separation is always the same and any throttling down just postpones the booster separation and increases gravity losses. Once past max Q you'd ramp all the engines to 100% and leave them there through booster ECO at around 155 seconds.