Author Topic: Should Super Heavy (BFR/ITS) have a smaller prototype to ease development?  (Read 46176 times)

Offline spacenut

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Re: Should ITS have a smaller prototype to ease development?
« Reply #220 on: 07/21/2017 05:43 PM »
Pads 39A and 39B both can handle 12 million lbs thrust.  SpaceX should try to build the biggest ITS within their existing capabilities.  Their factory can handle up to 10 meters in diameter.  The pads can handle the 12 million lb thrust.  How many Raptors can fit under 10 meters and give 12 million lbs thrust or less?  That fully reusable should be able to get 100+ tons to orbit payload.  It would beat SLS being reusable. 

Online Kenp51d

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Re: Should ITS have a smaller prototype to ease development?
« Reply #221 on: 07/21/2017 05:48 PM »
Let's not mention Bitsy in the same sentence as Its'y
Ok back to serious.
Lar, what would guesstimate the new LV could send to Mars surface if it had 120,000 lbs to LEO, with a handful of tanker flights to it, moon?
Would That be enough to do some real science, and start a full time base? Not colony, but base?

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« Last Edit: 07/21/2017 05:51 PM by Kenp51d »

Offline M.E.T.

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Re: Should ITS have a smaller prototype to ease development?
« Reply #222 on: 07/21/2017 05:53 PM »
Let's not mention Bitsy in the same sentence as It's
Ok back to serious.
Lar, what would guesstimate the new LV could send to Mars surface if it had 120,000 lbs to LEO, with a handful of tanker flights to it, moon?
Would That be enough to do some real science, and start a full time base? Not colony, but base?

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In my view if you go for only 50 ton dry mass payloads to LEO, then you have to look at modular launches with in orbit assembly for any one Mars trip. And I thought that was something SpaceX was avoiding due to cost issues, the need for economies of scale etc.

Online Kenp51d

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Re: Should ITS have a smaller prototype to ease development?
« Reply #223 on: 07/21/2017 06:07 PM »
Then how much dry mass payloads to LEO you would be the minimum needed to avoid in orbit assembly?
Would some in orbit assembly be  a practical aproach?


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Offline Steve D

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Re: Should ITS have a smaller prototype to ease development?
« Reply #224 on: 07/21/2017 07:37 PM »
What if the Mini ITS replaced the second stage of a falcon heavy? Would that be workable?

Online Lars-J

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Re: Should ITS have a smaller prototype to ease development?
« Reply #225 on: 07/21/2017 07:52 PM »
What if the Mini ITS replaced the second stage of a falcon heavy? Would that be workable?

That would be much smaller. Much smaller.

That's what people were arguing against when this thread was starting. To create a one-off prototype that is smaller. A smaller ITS system is another thing. But the smaller ITS will still (very likely) be much larger than what FH could lift off the pad.

Offline DJPledger

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Re: Should ITS have a smaller prototype to ease development?
« Reply #226 on: 07/22/2017 04:26 PM »
I guess the new smaller ITS will not be more than 12Mlbf liftoff thrust for the booster so it can launch from LC-39A without too much modification. It could be around 8m dia. and have 19 Raptors in 1+6+12 configuration for max. thrust to dia. ratio. Perhaps have all engines fixed for max. packing density and use differential throttling and/or cold gas thrusters for steering. For 19 engines the Raptor would have to be slightly smaller than the one announced at IAC2016 to keep within the 12Mlbf limit. Keeping the dia. to 8m will reduce the difficulty and cost of transporting it from the manufacturing site to the launch site. The mini ITS ship could use the subscale Raptor so it can basically be a downscaled version of the one announced at IAC2016. The smaller ITS will likely be a stepping stone to a next gen. ITS system along the lines of the one announced at IAC2016 which will need an entirely new launch complex. Perhaps keep the engine no. to 19 on the booster of the next gen. ITS system by scaling up the Raptor and use the vac. version of the Raptor of the booster of the mini ITS system for the ship of the next gen. ITS system. By the time serious work starts on the next gen. ITS system the mini ITS system will be launching regularly and SpaceX will have plenty of funding and experience to be able to scale up Raptor to at least F-1 class.

EM explicitly mentioned the difficulty of lighting up 27 engines for FH which makes the operation of a 42 engine booster questionable at the least. 19 engines for the booster sounds a good no. for engine out capability while keeping operational challenges of lighting up all engines to a reasonable level.

Mini ITS may use AL-Li tanks as SpaceX is appearing to be having trouble with dev. composite tanks.

Offline DOCinCT

Pads 39A and 39B both can handle 12 million lbs thrust.  SpaceX should try to build the biggest ITS within their existing capabilities.  Their factory can handle up to 10 meters in diameter.  The pads can handle the 12 million lb thrust.  How many Raptors can fit under 10 meters and give 12 million lbs thrust or less?  That fully reusable should be able to get 100+ tons to orbit payload.  It would beat SLS being reusable.
If you measure the picture from the 2016 presentation, the inner ring of 14 full size raptor engines is 10 meters in diameter. There are also 7 in the center cluster (the ones that gimbal). So 21 full size raptor engines or 13,860,000+ lbs of thrust at full rating.

Offline tater

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Re: Should ITS have a smaller prototype to ease development?
« Reply #228 on: 07/22/2017 08:06 PM »
Musk tweeted that their current factory could deal with 9m when asked about the new size.

Offline DJPledger

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Re: Should ITS have a smaller prototype to ease development?
« Reply #229 on: 07/22/2017 08:19 PM »
Pads 39A and 39B both can handle 12 million lbs thrust.  SpaceX should try to build the biggest ITS within their existing capabilities.  Their factory can handle up to 10 meters in diameter.  The pads can handle the 12 million lb thrust.  How many Raptors can fit under 10 meters and give 12 million lbs thrust or less?  That fully reusable should be able to get 100+ tons to orbit payload.  It would beat SLS being reusable.
If you measure the picture from the 2016 presentation, the inner ring of 14 full size raptor engines is 10 meters in diameter. There are also 7 in the center cluster (the ones that gimbal). So 21 full size raptor engines or 13,860,000+ lbs of thrust at full rating.
Ring of 14 full size Raptors is closer to 8m dia. than 10m so should fit under a 9m core.

Offline mme

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Re: Should ITS have a smaller prototype to ease development?
« Reply #230 on: 07/22/2017 10:28 PM »
I have to ask...

Why not make a second stage for Falcon that is fully reusable?

It doesn't have to carry any usable payload, just use it to prove that the ITS second stage systems will work.
Trying to recover S2. Isn't that the most recent Hail Mary that Musk has been talking about with FH?
Space is not Highlander.  There can, and will, be more than one.

Online docmordrid

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Offline redliox

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