Author Topic: Speculation: SFR (mini-BFR) as fully reusable Falcon Heavy replacement  (Read 171977 times)

Offline Robotbeat

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This "ITS SSTO" is totally off-topic in this thread. Shouldn't it have it's own thread?
Endorse.
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Offline envy887

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This "ITS SSTO" is totally off-topic in this thread. Shouldn't it have it's own thread?
Endorse.

I started a new thread: https://forum.nasaspaceflight.com/index.php?topic=42003.0

Offline OneSpeed

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By request, here is a speculative simulation of the Mini ITS. I've assumed the Mini BFR will have 7 x Raptor 50, and the Mini BFS 2 x Raptor 80. The Mini BFR should have no trouble landing on a single Raptor 50, but the Raptor 80s on the Mini BFS might not be able to throttle deeply enough to land. Perhaps four of the methalox vernier thrusters seen on the full scale BFS could be used as landing engines? If they have 10mT thrust each, they should be able to land the 18mT Mini BFS + fuel.

The sim gets about 118mT to a 300 x 300 km orbit. Depending on how much ullage you think is necessary, I suspect 70-80 mT of that could be payload, and still have enough fuel to land the ship.


Offline envy887

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By request, here is a speculative simulation of the Mini ITS. I've assumed the Mini BFR will have 7 x Raptor 50, and the Mini BFS 2 x Raptor 80. The Mini BFR should have no trouble landing on a single Raptor 50, but the Raptor 80s on the Mini BFS might not be able to throttle deeply enough to land. Perhaps four of the methalox vernier thrusters seen on the full scale BFS could be used as landing engines? If they have 10mT thrust each, they should be able to land the 18mT Mini BFS + fuel.

The sim gets about 118mT to a 300 x 300 km orbit. Depending on how much ullage you think is necessary, I suspect 70-80 mT of that could be payload, and still have enough fuel to land the ship.

That looks great. Does the IMLEO improve if the spaceship has a single 200:1 engine instead of two 80:1? The 200:1 has more thrust and ISP in vacuum, and the main engine isn't needed for landing.

Offline RocketmanUS

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By request, here is a speculative simulation of the Mini ITS. I've assumed the Mini BFR will have 7 x Raptor 50, and the Mini BFS 2 x Raptor 80. The Mini BFR should have no trouble landing on a single Raptor 50, but the Raptor 80s on the Mini BFS might not be able to throttle deeply enough to land. Perhaps four of the methalox vernier thrusters seen on the full scale BFS could be used as landing engines? If they have 10mT thrust each, they should be able to land the 18mT Mini BFS + fuel.

The sim gets about 118mT to a 300 x 300 km orbit. Depending on how much ullage you think is necessary, I suspect 70-80 mT of that could be payload, and still have enough fuel to land the ship.


Why not 9 engines on the BFR as F9 has?
What percentage of propellant is left for return and landing for BFR?
What is the dry mass of the BFS?

Offline hkultala

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Why not 9 engines on the BFR as F9 has?

Because 7 is cheaper than 9.

Better question is: Why 2 engines in the upper stage? 1 sounds like a more balanced design.
« Last Edit: 01/21/2017 07:23 PM by hkultala »

Online guckyfan

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7 engines means they can be equidistant for free gimaling. It is also the same arrangement as on the big first stage center. Much could be made the same.

Plus, I have suggested 7 engines long before BO announced they would use 7 on New Glenn, for the reasons above.  :)

Offline OneSpeed

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Does the IMLEO improve if the spaceship has a single 200:1 engine instead of two 80:1? The 200:1 has more thrust and ISP in vacuum, and the main engine isn't needed for landing.

Sounds feasible, so I tried it.
The mass of the Mini BFS at separation is 538mT, so T/W for a single Raptor Vac is 357 / 538 = 0.66. Just to maintain altitude I had to use crazy amounts of alpha (approaching 45 at 3000m/s), so there were considerable cosine losses. As fuel burnt off, the required alpha gradually reduced, and I did get to orbit, but total mass to orbit was about 20mT less than for two Raptor 80.

Online MATTBLAK

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Anyone else noticed that the Space X website seems to have purged most material pertaining to the ITS and Mars ambitions?!
"Those who can't, Blog".   'Space Cadets' of the World - Let us UNITE!! (crickets chirping)

Offline Robotbeat

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Anyone else noticed that the Space X website seems to have purged most material pertaining to the ITS and Mars ambitions?!
Not at all. All still there: http://www.spacex.com/mars
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To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline envy887

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Anyone else noticed that the Space X website seems to have purged most material pertaining to the ITS and Mars ambitions?!

They bumped the main page Mars video for a replay of the Iridium launch, which isn't unusual. They usually have the latest mission there. The IAC speech video and several other references to making humans interplanetary are still there.

Online MATTBLAK

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Anyone else noticed that the Space X website seems to have purged most material pertaining to the ITS and Mars ambitions?!
Not at all. All still there: http://www.spacex.com/mars
Okay; so not purged, so to speak. But all I could find were a few ITS pictures when I looked this morning?!
"Those who can't, Blog".   'Space Cadets' of the World - Let us UNITE!! (crickets chirping)

Online AncientU

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Anyone else noticed that the Space X website seems to have purged most material pertaining to the ITS and Mars ambitions?!
Not at all. All still there: http://www.spacex.com/mars

There are also two new 7-8 minute features that follow-on the themes of the IAC presentation:
SpaceX Interplanetary Transport System – Part two


SpaceX Interplanetary Transport System – Part three


These were follolw-ons to the IAC animation of ITS...
Have they been seen here before? (If so, I missed them.)

Edit: Mods, please move or remove this post as appropriate.
Started new thread:
https://forum.nasaspaceflight.com/index.php?topic=42103.msg1633686#msg1633686
« Last Edit: 01/22/2017 12:27 AM by AncientU »
"If we shared everything [we are working on] people would think we are insane!"
-- SpaceX friend of mlindner

Offline Robotbeat

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I like your videos, but should be in their own thread.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Robotbeat

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Bump.

My guess: they'll use subscale Raptor at first with a number of engines between that of FH and F9. The diameter maybe 10m.

They can stretch it as the Raptor thrust increases.

I predict they'll make the spaceship first so they can start suborbital testing first, but they'll essentially build the booster in parallel.
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To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online RotoSequence

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Bump.

My guess: they'll use subscale Raptor at first with a number of engines between that of FH and F9. The diameter maybe 10m.

They can stretch it as the Raptor thrust increases.

I predict they'll make the spaceship first so they can start suborbital testing first, but they'll essentially build the booster in parallel.

https://twitter.com/elonmusk/status/888813713800785923

Quote from: Elon Musk
A 9m diameter vehicle fits in our existing factories ...
« Last Edit: 07/22/2017 05:56 PM by RotoSequence »

Offline CTC

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What I would think is that they will change the design a bit and copy some ideas from the competition.
Reusable booster with reusable second stage. Spaceship for moving cargo and people between LEO and Moon/Mars orbits. Spaceship togheter with fully fuelled second stage can also be used for going straight to surface.
No real tankers, expendable drop tanks for second stage.
Payload lowered from 300t to the 150t to LEO range. Diameter stays at 12m for booster.

Offline M.E.T.

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What I would think is that they will change the design a bit and copy some ideas from the competition.
Reusable booster with reusable second stage. Spaceship for moving cargo and people between LEO and Moon/Mars orbits. Spaceship togheter with fully fuelled second stage can also be used for going straight to surface.
No real tankers, expendable drop tanks for second stage.
Payload lowered from 300t to the 150t to LEO range. Diameter stays at 12m for booster.

Unless I misinterpreted the post above yours, Elon has semi-confirmed a 9m diameter.

Offline Robotbeat

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What I would think is that they will change the design a bit and copy some ideas from the competition.
Reusable booster with reusable second stage. Spaceship for moving cargo and people between LEO and Moon/Mars orbits. Spaceship togheter with fully fuelled second stage can also be used for going straight to surface.
No real tankers, expendable drop tanks for second stage.
Payload lowered from 300t to the 150t to LEO range. Diameter stays at 12m for booster.
Drop tanks don't make any sense.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Robotbeat

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Bump.

My guess: they'll use subscale Raptor at first with a number of engines between that of FH and F9. The diameter maybe 10m.

They can stretch it as the Raptor thrust increases.

I predict they'll make the spaceship first so they can start suborbital testing first, but they'll essentially build the booster in parallel.

https://twitter.com/elonmusk/status/888813713800785923

Quote from: Elon Musk
A 9m diameter vehicle fits in our existing factories ...
Very good!

And is pretty close to the 8.4m diameter Shuttle External Tank, so cost to move from Hawthorne to Florida or Texas (Boca Chica) should be similar to the $3 million figure or maybe a bit less.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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