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Are you kidding? The USAF has a very cozy relationship with the ULA. It was obvious to any non-naive observer at the time that the block buy was designed to loc

Are you kidding? The USAF has a very cozy relationship with the ULA. It was obvious to any non-naive observer at the time that the block buy was designed to lock in billions of dollars in government spending to the ULA before SpaceX would come along and smash the existing pricing structure, offering launches that ULA couldn't hope to compete with. Even if SpaceX's prices go up with EELV launches, and even if they would never incorporate reusability into EELV launches, they would still be able to offer launches for every possible EELV payload at prices far below ULA's. Anything ULA could launch on any of their vehicles SpaceX could launch on the Falcon Heavy, and many launches (like GPS birds) could happen on the even cheaper Falcon 9. With reusability, which SpaceX seems to have a good handle on, those costs get slashed, especially the cost of the Falcon Heavy. Any EELV payload could be launched on a reusable Falcon Heavy, even if it meant forgoing crossfeed. Even if the first stages could only be reused twice (a paltry amount) that would lower the cost of a reusable Falcon Heavy to around the cost of a Falcon 9, around $50 million. Keep in mind that every ULA launcher uses an RL-10 in the upper stage, and that's a $40 million engine. Even at discounted prices simply having an engine that expensive (to say nothing of the rest of the vehicle) on every launch makes it impossible to offer launches as cheap as SpaceX could.

mrfusion 13y ago
What is crossfeed?
- deleted 13y ago
  [deleted]
- ChillyWater 13y ago
  Usually, with aircraft or spacecraft, this is a reconfigurable plumbing setup that allows engines/jets to use the fuel source from a different engine on the fly. For instance, the Shuttle could perform OMS to RCS crossfeeds.
- InclinedPlane 13y ago
  The Falcon Heavy uses 3 identical cores as the "first stage" of the vehicle. If each of the stages burns at the same rate and burns out at the same time then it's basically just one big stage and the Falcon Heavy would just be a 2-stage launcher. Adding more stages increases payload performance of launchers because you're dumping dead weight. The plan for the Falcon Heavy is to have cross feed between the engines so that effectively the center stage's engines are run off the outer stages' fuel tanks until those tanks are dry. Then the outer stages separate and the center stage fires alone (as a 2nd stage) until it is depleted, then the upper stage fires (as a 3rd stage), massively increasing overall payload. The Delta IV Heavy throttles down the center core during launch and peels away the outer cores first in a sort of "virtual crossfeed" scenario, though this comes at the cost of liftoff thrust. The only problem with crossfeed for the Falcon Heavy is that it leaves the center core traveling a lot faster and a lot farther down range than the first stage of a Falcon 9 normally would be, which might make it a lot harder to return to the launch site for reusability. However, as a worst-case scenario the Falcon Heavy could be operated without crossfeed with all lower stage cores burning out at the same time, which would reduce payload significantly but the cost savings would probably make it worthwhile even so.
  - mrfusion 13y ago
    You might need to dumb it down a bit more for me :-( What's a core? Why would the stages burn at the same time? I thought the second stage wouldn't turn on until the first stage is jettisoned?
    - InclinedPlane 13y ago
      Right. OK. So with a simple 2-stage rocket like the Falcon 9 you have the first stage which has the 2nd stage stacked on top of it which has the payload stacked on top of it. During a normal flight the first stage (which is the biggest stage) lights, lifts the whole thing off the ground, and pushes the rocket up into the air and starts getting it up to speed. Then the first stage runs out of fuel, it separates and then the 2nd stage takes over, pushing the payload the rest of the way to orbit. The Falcon Heavy uses the same "2nd" stage but it uses 3 first stages instead of just one, which are called "cores". Each core is just a Falcon 9 first stage, for the most part. The idea of the Falcon Heavy (similar to the way the Delta IV Heavy works) is that you have three times as many first stages pushing, which leads to increased payload. With the cross-feed option you end up with effectively a 3-stage launcher. The outer two cores becomes like the first stage, and they are jettisoned when empty, then you have the inner core which now becomes a 2nd stage, and the previous 2nd stage is now a 3rd stage (or just "upper stage", to avoid confusion). But, as mentioned, when you fly this way the 2nd stage core ends up way faster and way farther away when it's done thrusting, so in the prospect of having it keep around some extra propellant so it can thrust back to the launch site and land so it can be reused becomes much more difficult. But in a worst-case scenario all of the "cores" can be run at the same time, so they burn out the same distance away from land and can each return and be reused (saving a lot of money). You end up with only a 2 stage vehicle (3 1st-stages all running at the same time plus the upper stage) which would decrease performance, but because you recover all of the first stage cores (instead of only 2/3 of them) the cost benefit would probably be worth the payload reduction.

mrfusion 13y ago

What is crossfeed?

deleted 13y ago
[deleted]
ChillyWater 13y ago
Usually, with aircraft or spacecraft, this is a reconfigurable plumbing setup that allows engines/jets to use the fuel source from a different engine on the fly. For instance, the Shuttle could perform OMS to RCS crossfeeds.
InclinedPlane 13y ago
The Falcon Heavy uses 3 identical cores as the "first stage" of the vehicle. If each of the stages burns at the same rate and burns out at the same time then it's basically just one big stage and the Falcon Heavy would just be a 2-stage launcher. Adding more stages increases payload performance of launchers because you're dumping dead weight. The plan for the Falcon Heavy is to have cross feed between the engines so that effectively the center stage's engines are run off the outer stages' fuel tanks until those tanks are dry. Then the outer stages separate and the center stage fires alone (as a 2nd stage) until it is depleted, then the upper stage fires (as a 3rd stage), massively increasing overall payload. The Delta IV Heavy throttles down the center core during launch and peels away the outer cores first in a sort of "virtual crossfeed" scenario, though this comes at the cost of liftoff thrust. The only problem with crossfeed for the Falcon Heavy is that it leaves the center core traveling a lot faster and a lot farther down range than the first stage of a Falcon 9 normally would be, which might make it a lot harder to return to the launch site for reusability. However, as a worst-case scenario the Falcon Heavy could be operated without crossfeed with all lower stage cores burning out at the same time, which would reduce payload significantly but the cost savings would probably make it worthwhile even so.
- mrfusion 13y ago
  You might need to dumb it down a bit more for me :-( What's a core? Why would the stages burn at the same time? I thought the second stage wouldn't turn on until the first stage is jettisoned?
  - InclinedPlane 13y ago
    Right. OK. So with a simple 2-stage rocket like the Falcon 9 you have the first stage which has the 2nd stage stacked on top of it which has the payload stacked on top of it. During a normal flight the first stage (which is the biggest stage) lights, lifts the whole thing off the ground, and pushes the rocket up into the air and starts getting it up to speed. Then the first stage runs out of fuel, it separates and then the 2nd stage takes over, pushing the payload the rest of the way to orbit. The Falcon Heavy uses the same "2nd" stage but it uses 3 first stages instead of just one, which are called "cores". Each core is just a Falcon 9 first stage, for the most part. The idea of the Falcon Heavy (similar to the way the Delta IV Heavy works) is that you have three times as many first stages pushing, which leads to increased payload. With the cross-feed option you end up with effectively a 3-stage launcher. The outer two cores becomes like the first stage, and they are jettisoned when empty, then you have the inner core which now becomes a 2nd stage, and the previous 2nd stage is now a 3rd stage (or just "upper stage", to avoid confusion). But, as mentioned, when you fly this way the 2nd stage core ends up way faster and way farther away when it's done thrusting, so in the prospect of having it keep around some extra propellant so it can thrust back to the launch site and land so it can be reused becomes much more difficult. But in a worst-case scenario all of the "cores" can be run at the same time, so they burn out the same distance away from land and can each return and be reused (saving a lot of money). You end up with only a 2 stage vehicle (3 1st-stages all running at the same time plus the upper stage) which would decrease performance, but because you recover all of the first stage cores (instead of only 2/3 of them) the cost benefit would probably be worth the payload reduction.