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Does anyone know if this demo will also include a triple landing attempt?
Also, if anyone has an inside track on how to watch this from the control center, please PM me. I just might be in Florida around those dates
As mentioned before, ship landings are needed for high velocity missions. Altitude & distance don't mean much for orbit. All about speed.
Ship landings are not needed for flexibility or to save fuel costs. Just not physically possible to return to launch site
If speed at stage separation > ~6000 km/hr. With a ship, no need to zero out lateral velocity, so can stage at up to ~9000 km/h
Does anyone know if this demo will also include a triple landing attempt?
From a risk standpoint, I wonder if separate LZ's are preferable anyway... so that way if one stage fall down go boom!, it doesn't wipe out the other two that just touched down next to it.
This is a rendering, but you can see that they are rather spaced out. All of these are at LZ1.
On the main central pad to give you an idea of how *BIG* it is (That is a person standing in the middle).
and the size of one booster on that pad (it easily fits within the X on the pad)
So what I am getting at is that unless something goes seriously wrong with the guidance software and or the thrusters directing the vehicle, one should be far enough away from the other than it wouldn't interfere should one tip over or come in too hard.
I am assuming the reason they were planning for 4 pads at one site is in case of explosion on one they can still land on another while the destroyed pad is repaired.
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Sorry, the rendering actually has 5 pads, you just can't see one in the screen grab from the film, because it is focused on the booster itself. That booster is landing on an out-of-frame pad at the bottom of the image.
Ah cool, thanks.. I assumed pad and LZ were synonymous... it appears not.
Speculation of course, but it would seem to me that they would remain within hundreds of feet of each other the whole way.
Ah cool, thanks.. I assumed pad and LZ were synonymous... it appears not.
That's assuming they all start back at the same time. Given the speed that they are traveling, delaying the boost back burn on one of them for say ten seconds would give lots of separation.
Here is the video from where the screen grabs came from if you want to watch:
That's assuming they all start back at the same time. Given the speed that they are traveling, delaying the boost back burn on one of them for say ten seconds would give lots of separation.
That's assuming they all start back at the same time. Given the speed that they are traveling, delaying the boost back burn on one of them for say ten seconds would give lots of separation.
The current idea as I understand it is for the two outer boosters to run at full thrust from takeoff, until they reach their fuel limits, separate, and boost back (maybe with a slight delay for one of them). The center booster will have done all the throttling needed to not exceed Max Q (aerodynamic pressure) and will continue its burn for a while longer, before separating from the second stage.
If they can actually do what was originally put forward all three boosters would be firing at the same time. There would be a crossfeed on the connections so the center booster is getting fuel from the sides such that at separation the center should still be near full of fuel. It would discard the sides and now dead weight and continue firing the rocket forward (although may slow down to allow a clean separation).
It should be noted that as I recall noone has been able to make a cross feed type system work before. So this will be yet another "it can't be done" that SpaceX puts to bed as possible.
That was the original plan, but I don't think they even want to try any more. The throttling is necessary anyway, and gives most of the benefits of the crossfeed, without most of the complexity.
Falcon Heavy | SpaceXPROPELLANT CROSS-FEED SYSTEM: For missions involving exceptionally heavy payloads—greater than 45,000 kilograms or 100,000 pounds—Falcon Heavy offers a unique cross-feed propellant system. Propellant feeds from the side boosters to the center core so that the center core retains a significant amount of fuel after the boosters separate.
This is not correct, since it ignores the benefits of saving some fuel until the accelerated dead mass is less. Here's a numerical example:
Assume each core is 30 t empty, holds 420 t of fuel, ISP = 311, and a second stage mass of 125 t. The three boosters combined mass 90 t at burnout. So running all of them in parallel, as you suggest, the delta-V is 311*9.8*ln(1260 + 90 + 125)/(90 + 125)) = 5869 m/s imparted to the second stage.
Now alternatively, use the two side cores to loft a full middle core. The the side cores burn 840 t of fuel to lift a payload of 575 t (420 fuel + 30 middle core + second stage). Thus the delta-V when the 2 cores burn out is: 311*9.8*ln((840+60+575)/(60+575)) = 2568 m/s. Then the middle core burns, adding 311*9.8*ln((420+30+125)/(30+125)) = 3995 m/s. That's a total of 6563 m/s imparted tp the second stage, about 700 m/s more than parallel staging. Of course your gravity losses are higher in the second case. You compromise by using full thrust at first, then throttle back to save more fuel for after staging.
You don't need to take my word (or calculations) for this. Look at the Delta-IV heavy ( Delta IV Heavy Rockets ). It takes off at full power, then throttles down the middle core at about 50 sec, well before acceleration limits kick in. The side cores run at full power until they run out of fuel, then they stage away and the center core resumes at full thrust. They do this precisely to maximize the delta-V in a non-crossfeed situation. Exactly the same logic will apply to the Falcon Heavy.