Author Topic: Developing the BFS - Phase 1 Big Falcon Hopper (BFH) Discussion - THREAD 2  (Read 487506 times)

Offline rsdavis9

Yes given that they will probably be adding the 10 tonne gaseous thrusters and probably want to practice landing on a mount(for SH). This version will probably not have the RCS system. Doesn't mean that future versions of the hopper are a ideal platform to test these things. Cheap, easy to make, easy to modify. Easy to crash.

The 10t thrusters were part of the 2016 version of MCT. Also at that tíme the concept was that the thrusters do what the aerosurfaces do now. They may use very much smaller thrusters in the present version.

Not for SH. They can use this hopper to help with the landing software for the booster. It has a big surface area affected by the wind. It has engines for hovering and RCS to move sideways.
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Offline Hauerg

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Then why did they build it?
To not have the elegance of the lunar lander simulator.
The lower end is business.
The upper half is looks only.

Offline billh

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Another hole has been made.
Makes sense. You need an access port for each tank.

Offline Pallen

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Another hole has been made.
Makes sense. You need an access port for each tank.
So now we know the center of each tank?  I look forward to someone handy with graphics to make a drawing or cutaway showing an improved guess as to tank locations, size and how much room is left for the engine room/area.

I hope this inquiry is worthy of being this lurkers first post on this forums SpaceX threads that I have been enjoying so much.
« Last Edit: 01/25/2019 10:11 pm by Pallen »
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Offline dglow

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I hope this inquiry is worthy of being this lurkers first post on this forums SpaceX threads that I have been enjoying so much.

Seems worthy to me. Welcome to (posting on) NSF!

Offline Llian Rhydderch

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Welcome to the fourm, Pallen.

Certainly a worthwhile angle of inquiry to suggest to the well-trained analytical minds that frequent the NSF multiplanetary alien lounge.  ;)
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Offline su27k

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Another hole has been made.
Makes sense. You need an access port for each tank.
So now we know the center of each tank?  I look forward to someone handy with graphics to make a drawing or cutaway showing an improved guess as to tank locations, size and how much room is left for the engine room/area.

Upper manhole center is about 1.2m from the top edge, if this hole is indeed at the mid point of the LOX tank that gives LOX tank height at 2.4m, dome height is ~2.6m, dome volume is about 80m^3, total LOX tank volume is 311m^3, which is 355t of LOX.

Mixture ratio is 3.6, so methane mass would be ~99t, which gives methane tank height ~3.7m, total hopper height is 12m, so distance between lowest point of the methane tank to lower edge of the hopper is 12 - 2.4 - 3.7 - 2.6 = 3.3m

Total propellant load is 454t, still seems high, since first prod Raptor may not reach 200t thrust. Maybe they'll just let it thrust for a while on the pad until T/W is high enough for liftoff, I think Soyuz uses this method.

Offline magnemoe

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Then why did they build it?
To not have the elegance of the lunar lander simulator.
The lower end is business.
The upper half is looks only.
Top give some more realistic aerodynamic behavior and center of gravity.
Same with the legs.
Yes its part look and part for more realistic tests.

Offline FinalFrontier

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Then why did they build it?
To not have the elegance of the lunar lander simulator.
The lower end is business.
The upper half is looks only.
Top give some more realistic aerodynamic behavior and center of gravity.
Same with the legs.
Yes its part look and part for more realistic tests.
Also:
To test controllability of raptor during hovering and finite throttle tasks. Reminder that one of the early Falcon 9 barge landings failed due to sticky throttle valves.
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Offline alang

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Know why people have mobile homes in hurricane country?
  Because when it blows away, you can get another mobile home and install it for about 1/4th the money in 1/10th the time of a stick built house.
 If making and securing the shiny hopper nose against hurricanes cost 4 times as much and took 4 times as long, it really wouldn't have made much sense. And it could be months before there's any reason, other than looking pretty, before they need it.

Sensible comment from a purely financial perspective. From that point of view SpaceX should be more worried about coastal erosion and the benefits of a breakwater.
However, having nearly lost part part of a corrugated roof on an occasion when it was reported as gusting 75mph a few miles away I'm more concerned about the possible effect on other people of flying debris. I don't know how concerned people should be about anything they build. Do local building codes cover something like the hopper?

Offline Bananas_on_Mars

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Know why people have mobile homes in hurricane country?
  Because when it blows away, you can get another mobile home and install it for about 1/4th the money in 1/10th the time of a stick built house.
 If making and securing the shiny hopper nose against hurricanes cost 4 times as much and took 4 times as long, it really wouldn't have made much sense. And it could be months before there's any reason, other than looking pretty, before they need it.

Sensible comment from a purely financial perspective. From that point of view SpaceX should be more worried about coastal erosion and the benefits of a breakwater.
However, having nearly lost part part of a corrugated roof on an occasion when it was reported as gusting 75mph a few miles away I'm more concerned about the possible effect on other people of flying debris. I don't know how concerned people should be about anything they build. Do local building codes cover something like the hopper?
Since it's not a fixed structure, no building codes should apply, same as a mobile home or a shipping container...
That thing is meant to fly, not to serve as a residence.

Offline SPadre

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Raw closeup video of launch pad and 1/2Hopper from Friday

SPadre is Rachel and Gene

Offline frostbit_canadian

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They should just fly it with that that dome as the top. Looks aerodynamic enough?
« Last Edit: 01/26/2019 02:03 pm by frostbit_canadian »

Offline flyright

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They should just fly it with that that dome as the top. Looks aerodynamic enough?

I've been thinking the same thing. Maybe they'll just pretty it up a bit and fly it the way it is.

Offline Zephyrox

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They should just fly it with that that dome as the top. Looks aerodynamic enough?

I've been thinking the same thing. Maybe they'll just pretty it up a bit and fly it the way it is.

I've been thinking the other way, now when they (might) have to recreate the top, they might as well make the full SS height. Even if it doesn't weigh much, inertia should matter when testing.

Offline jpo234

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They should just fly it with that that dome as the top. Looks aerodynamic enough?

I've been thinking the same thing. Maybe they'll just pretty it up a bit and fly it the way it is.
They might, but I don't think they will. Elon wants his Tintin rocket.
You want to be inspired by things. You want to wake up in the morning and think the future is going to be great. That's what being a spacefaring civilization is all about. It's about believing in the future and believing the future will be better than the past. And I can't think of anything more exciting than being out there among the stars.

Offline RobLynn

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Something interesting in bocachicagal's latest image, looks like they put a ventilation fan on the manhole. Maybe the missing piece on the top dome serves the same function: ventilation.
They're not even close to being done inside. They're still lowering all kinds of stuff through that big hole in the top. Having that hole means there was no reason to wait to put the dome on. It

With those large holes seems to me they could be building smaller inner tanks and plumbing + instrumentation, perhaps even some engine mounting thrust structure as one road road transportable unit to be finished off-site, lowered or raised into the hopper and then welded in place.
The glass is neither half full nor half empty, it's just twice as big as it needs to be.

Offline Star One

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They should just fly it with that that dome as the top. Looks aerodynamic enough?

I've been thinking the same thing. Maybe they'll just pretty it up a bit and fly it the way it is.
They might, but I don't think they will. Elon wants his Tintin rocket.

Agree that it is not flying without it’s top as I think by now we’ve established the importance of aesthetics to Mr Musk.

Offline Oersted

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I suggest an inflatable, that'll keep the outer mold line more or less similar to Starship. Just buy it in China...
http://chinainflatabletoy.buy.burrillandco.com/iz6bc3b24-inflatable-promotional-products-fresh-come-out-mirror-silver-ball-fireproof-images.html

Offline NH22077

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Another hole has been made.
Makes sense. You need an access port for each tank.
So now we know the center of each tank?  I look forward to someone handy with graphics to make a drawing or cutaway showing an improved guess as to tank locations, size and how much room is left for the engine room/area.

Upper manhole center is about 1.2m from the top edge, if this hole is indeed at the mid point of the LOX tank that gives LOX tank height at 2.4m, dome height is ~2.6m, dome volume is about 80m^3, total LOX tank volume is 311m^3, which is 355t of LOX.

Mixture ratio is 3.6, so methane mass would be ~99t, which gives methane tank height ~3.7m, total hopper height is 12m, so distance between lowest point of the methane tank to lower edge of the hopper is 12 - 2.4 - 3.7 - 2.6 = 3.3m

Total propellant load is 454t, still seems high, since first prod Raptor may not reach 200t thrust. Maybe they'll just let it thrust for a while on the pad until T/W is high enough for liftoff, I think Soyuz uses this method.

su27k,
Minor correction. Raptors are O2 rich, mix is 3.8:1

Ned

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