Author Topic: F9 - S2 reusable modification as evolution steps to BFS(ITS)  (Read 39039 times)

Offline raketa

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1/I think that Elon's decision to reuse S2 is not primarily driven by cost reduction
2/F9-S2 could serve as a small scale platform to finalize BFS shape, heat protection and flying/landing algorithm
3/F9-S2 could through small modification take approximate shape of BFS(ITS)
4/F9-S2 Heavy will be probably in dimension scale ~25% of BFS(ITS) and have also additional lifting capacity, to carry modification to orbit and still deliver a payload to LEO.
5/F9H with S2R could deliver cargo for paying customers and at the same time learn lessons for the development of BFS.
6/List of modification, that could be gradually implemented step by step and base on the previous flight experience:

Phase 1-Heat protection and small wings for direction purposes:
a/How much heat protection is necessary to save the tank from overheating:
if I use Space shuttle as a reference, heat protection will weight ~1ton
b/Small wings to direct S2 shuttle like approach through the atmosphere
weight ~ 1ton
c/Additional N2 for direction thruster
weight ~ several hundred kg

Phase 2 - Modified wings to optimized flight dynamics
Evolve wings shaping S2 to be even more similar to BFS
additional weight ~1-2 tons

Phase 3 -Add landing Thruster
Probably use Draco engine to softly land S2.
additional weight ~ 1 ton
I think S2 could gradually evolve to be reusable and give SpaceX great lessons for BFS finalization:
Phase 1: -survive heat
Phase 2: -improve cross landing and aerodynamic braking  characteristic
Phase3: -test landing approach and algorithm
Sounds like the modification weight could be ~5-7 ton, that for F9H could be reasonable.
Here is picture of mine idea how F9-S2 could be modified F9-S2-Reusable

Offline Robotbeat

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Gotta wonder if the Falcon Heavy Demi flight upper stage will look something like that. Doubt it's practical operationally, but should be useful as a tech demo for BFS.
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Offline cambrianera

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For what is worth... from an old thread.
For recovery gear, a 20 mm thick LI-900 heatshield would have a mass of less than 200 kg.
And landing speed should be low enough to use landing skids efficiently (wingload is less than 80 kg/square meter).
Oh to be young again. . .

Offline Peter.Colin

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I also suspect the reuse of S2 is not primarily cost driven but for ITS development purposes.
What needs to be tested first are the hardest parts,
Raptor engine, landing cradle, refueling in orbit.
Heat shield also but there is probably less risk in it not working as envisioned.


Phase 0) Titanium grid fins on maybe a bit longer cylindrical S2

This configuration might not need a big heat shield to re-enter Earths atmosphere, just a lot of fuel, and much lower payload.

Phase 1) Landing in a landing cradle, might be possible with simple S2-gridfin, steering thrusters configuration but likely to fail several times (a Hail Mary attempt). It's better to use a S2 than an already re-usable S1 for these otherwise expensive landing cradle attempts. Grasshopper attempts will probably be done first.

If the cradle landing doesn't work, landing legs are needed, or super Draco engines for more a precise landing in the cradle

Phase 2) Raptor engine(s) for S2

Phase 3) Methalox S2 refueling in orbit

Refueling in orbit by another "tanker S2", might make heavier payloads and enough fuel for landing possible with this reusable S2 version.


Phase 4) Change the body to ITS Spaceship form

Landing Legs and Super Draco will make it work with more certainty but are non-essential for ITS development
« Last Edit: 07/16/2017 07:39 PM by Peter.Colin »

Offline GORDAP

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I also suspect the reuse of S2 is not primarily cost driven but for ITS development purposes.
What needs to be tested first are the hardest parts,
Raptor engine, landing cradle, refueling in orbit.
Heat shield also but there is probably less risk in it not working as envisioned.


Phase 0) Titanium grid fins on maybe a bit longer cylindrical S2

This configuration might not need a big heat shield to re-enter Earths atmosphere, just a lot of fuel, and much lower payload.

Phase 1) Landing in a landing cradle, might be possible with simple S2-gridfin, steering thrusters configuration but likely to fail several times (a Hail Mary attempt). It's better to use a S2 than an already re-usable S1 for these otherwise expensive landing cradle attempts. Grasshopper attempts will probably be done first.

If the cradle landing doesn't work, landing legs are needed, or super Draco engines for more a precise landing in the cradle

Phase 2) Raptor engine(s) for S2

Phase 3) Methalox S2 refueling in orbit

Refueling in orbit by another "tanker S2", might make heavier payloads and enough fuel for landing possible with this reusable S2 version.


Phase 4) Change the body to ITS Spaceship form

Landing Legs and Super Draco will make it work with more certainty but are non-essential for ITS development


Landing in a landing cradle doesn't seem to be something SpaceX plans for the BFS (spacecraft) portion of the ITS system.

I think a more likely evolutionary scenario might be:

1) Develop a 'scaled' BFS as a reusable second stage for the FH.  This would have a 'captive' payload bay (no separate fairings) and would look (and land) like their published BFS renderings.  Diameter of 5.5-6 meters - whatever max would be feasible when launched with FH 1st stage(s).  From the start it would use a Raptor engine, composite tanks, and autogenous(sp?) pressurization.   This would primarily serve their constellation plans and high energy/mass GTO payloads.

2a) Develop a manned version of this craft (crew of 6-10).  Together with 2b (below), this would serve all manned LEO, cis-lunar, lunar landing, space tourism and Mars Exploration (versus colonization) purposes.  Musk's recent comments suggest he's about to make a concerted, public push to open up NASA to competitively bid all missions that SLS is currently planned for.  This craft would be SpaceX's offering.

2b) 'Tanker' version of this craft.  All 3 of these craft would have nearly identical outer mold lines.

3) Replace FH 1st stage(s) with single core 'Raptor 9'.

Offline envy887

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1) Develop a 'scaled' BFS as a reusable second stage for the FH.  This would have a 'captive' payload bay (no separate fairings) and would look (and land) like their published BFS renderings.  Diameter of 5.5-6 meters - whatever max would be feasible when launched with FH 1st stage(s).  From the start it would use a Raptor engine, composite tanks, and autogenous(sp?) pressurization.   This would primarily serve their constellation plans and high energy/mass GTO payloads.

2a) Develop a manned version of this craft (crew of 6-10).  Together with 2b (below), this would serve all manned LEO, cis-lunar, lunar landing, space tourism and Mars Exploration (versus colonization) purposes.  Musk's recent comments suggest he's about to make a concerted, public push to open up NASA to competitively bid all missions that SLS is currently planned for.  This craft would be SpaceX's offering.

2b) 'Tanker' version of this craft.  All 3 of these craft would have nearly identical outer mold lines.

3) Replace FH 1st stage(s) with single core 'Raptor 9'.

This evolutionary path has been discussed elsewhere on this forum, and the main drawbacks are the need to redesign the FH TEL and GSE, and difficulty in building a TEL and GSE that support a Raptor mini-BFS and the standard F9/FH upper stage.

The most obvious place to launch this vehicle would be 39A, but 39A is needed for NASA launches (especially crew) which require the current upper stage for the foreseeable future. The other obvious place to launch it is Boca Chica, which is great for Mars/Moon/GTO, but much less so for constellation launches due to launch azimuth constraints.

Launching anywhere else would require a new pad, so the only way this vehicle can support the initial constellation deployment in the 2019/2020 timeframe would be adding a crew tower to LC-40 and then modifying the 39A TEL/GSE to launch only FH+mini-BFS, while heavy NSS missions launch from Boca Chica and VAFB.

Offline Jim

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while heavy NSS missions launch from Boca Chica

Non started.  NSS missions only launch from the Cape and VAFB.

Online rakaydos

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while heavy NSS missions launch from Boca Chica

Non started.  NSS missions only launch from the Cape and VAFB.
Historically, what other options were there, that NSS declined?

Offline Jim

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while heavy NSS missions launch from Boca Chica

Non started.  NSS missions only launch from the Cape and VAFB.
Historically, what other options were there, that NSS declined?

It is a top level requirement, there are no options.

Offline envy887

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while heavy NSS missions launch from Boca Chica

Non started.  NSS missions only launch from the Cape and VAFB.
Historically, what other options were there, that NSS declined?

It is a top level requirement, there are no options.

Has anyone offered a NSS launch from any other site and been refused?

Offline Ionmars

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If this approach were used to establish a platform for testing BFS, there may be two basic questions. First, how much mass will Falcon 9R block 5 boost to stage separation, and (2) how much volume could be built into a partially-fuelled, empty stage 2-to-orbit vehicle that resembles the BFS. This will tell us how closely this testbed BFS could resemble a final BFS with usable payload that could be launched by an intermediate BFR.
* Mars: a convenient service station for an asteroid-sized spaceship en-route to Ceres. *

Offline envy887

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If this approach were used to establish a platform for testing BFS, there may be two basic questions. First, how much mass will Falcon 9R block 5 boost to stage separation, and (2) how much volume could be built into a partially-fuelled, empty stage 2-to-orbit vehicle that resembles the BFS. This will tell us how closely this testbed BFS could resemble a final BFS with usable payload that could be launched by an intermediate BFR.

Why launch on F9 if FH is available and could launch it fully fueled?

Offline Jim

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Has anyone offered a NSS launch from any other site and been refused?

Nobody offers an NSS launch.  They respond to a solicitation that has launch site as a requirement.

Also, part of EELV certification is having operations located at the Cape or VAFB.

Offline envy887

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Has anyone offered a NSS launch from any other site and been refused?

Nobody offers an NSS launch.  They respond to a solicitation that has launch site as a requirement.

Also, part of EELV certification is having operations located at the Cape or VAFB.

What are the reasons for the requirement? Clearly not orbital mechanics.

Offline Jim

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What are the reasons for the requirement? Clearly not orbital mechanics.

The NSS has existing infrastructure at those launch sites to support its missions.

Offline envy887

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What are the reasons for the requirement? Clearly not orbital mechanics.

The NSS has existing infrastructure at those launch sites to support its missions.

Such as?

Offline Jim

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What are the reasons for the requirement? Clearly not orbital mechanics.

The NSS has existing infrastructure at those launch sites to support its missions.

Such as?

https://www.gao.gov/assets/660/652037.pdf

Offline Peter.Colin

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I also suspect the reuse of S2 is not primarily cost driven but for ITS development purposes.
What needs to be tested first are the hardest parts,
Raptor engine, landing cradle, refueling in orbit.
Heat shield also but there is probably less risk in it not working as envisioned.


Phase 0) Titanium grid fins on maybe a bit longer cylindrical S2

This configuration might not need a big heat shield to re-enter Earths atmosphere, just a lot of fuel, and much lower payload.

Phase 1) Landing in a landing cradle, might be possible with simple S2-gridfin, steering thrusters configuration but likely to fail several times (a Hail Mary attempt). It's better to use a S2 than an already re-usable S1 for these otherwise expensive landing cradle attempts. Grasshopper attempts will probably be done first.

If the cradle landing doesn't work, landing legs are needed, or super Draco engines for more a precise landing in the cradle

Phase 2) Raptor engine(s) for S2

Phase 3) Methalox S2 refueling in orbit

Refueling in orbit by another "tanker S2", might make heavier payloads and enough fuel for landing possible with this reusable S2 version.


Phase 4) Change the body to ITS Spaceship form

Landing Legs and Super Draco will make it work with more certainty but are non-essential for ITS development


Landing in a landing cradle doesn't seem to be something SpaceX plans for the BFS (spacecraft) portion of the ITS system.

I think a more likely evolutionary scenario might be:

1) Develop a 'scaled' BFS as a reusable second stage for the FH.  This would have a 'captive' payload bay (no separate fairings) and would look (and land) like their published BFS renderings.  Diameter of 5.5-6 meters - whatever max would be feasible when launched with FH 1st stage(s).  From the start it would use a Raptor engine, composite tanks, and autogenous(sp?) pressurization.   This would primarily serve their constellation plans and high energy/mass GTO payloads.

2a) Develop a manned version of this craft (crew of 6-10).  Together with 2b (below), this would serve all manned LEO, cis-lunar, lunar landing, space tourism and Mars Exploration (versus colonization) purposes.  Musk's recent comments suggest he's about to make a concerted, public push to open up NASA to competitively bid all missions that SLS is currently planned for.  This craft would be SpaceX's offering.

2b) 'Tanker' version of this craft.  All 3 of these craft would have nearly identical outer mold lines.

3) Replace FH 1st stage(s) with single core 'Raptor 9'.


Landing in a cradle is big part of the ITS Big Falcon Rocket so why not try to practice cradle landing using a lighter cylindrical S2? (The new positioning base thrusters can be less powerful)
For a small S2, a cradle landing saves weight, for a BFR I think their primary goal is not to save weight, but to save a transportation trip from landing pad to launching pad.. because it's so F... Big.

I agree that the desired smaller rocket will be a single core raptor first stage, and that there will be a satellite deploying BFS second stage on top of it.
Walking in developing steps backward from this end design to FH.
They might do such a mini BFS for FH, but it would surprise me a lot, if they began with the BFS form factor.

My guess is there will be cylindrical second stage steps in between.
I know it's kind of boring... but a "safer" development approach.

If they where to bid for an SLS alternative, a complete mini ITS (BFR/BFS) might be smarter than a complex FH/BFS.
Another SLS alternative is a reusable mini BFR to lift all the other companies spacecraft cheaper into orbit.
And of course also a mini BFS either part of the deal or not.


« Last Edit: 07/17/2017 09:14 PM by Peter.Colin »

Offline envy887

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What are the reasons for the requirement? Clearly not orbital mechanics.

The NSS has existing infrastructure at those launch sites to support its missions.

Such as?

https://www.gao.gov/assets/660/652037.pdf

Quote
Air Force officials indicated that existing sites at locations other than the Cape and Vandenberg were not comparably equipped for NSS launches; for example, they lack the necessary payload integration facilities.

Anything else? Building integration facilities doesn't seem to be beyond the realm of possibility, as SpaceX needs them anyway for commsats. What particular requirements do NSS payloads have for integration that a commercial bird wouldn't?

Offline raketa

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I also suspect the reuse of S2 is not primarily cost driven but for ITS development purposes.
What needs to be tested first are the hardest parts,
Raptor engine, landing cradle, refueling in orbit.
Heat shield also but there is probably less risk in it not working as envisioned.


Phase 0) Titanium grid fins on maybe a bit longer cylindrical S2

This configuration might not need a big heat shield to re-enter Earths atmosphere, just a lot of fuel, and much lower payload.

Phase 1) Landing in a landing cradle, might be possible with simple S2-gridfin, steering thrusters configuration but likely to fail several times (a Hail Mary attempt). It's better to use a S2 than an already re-usable S1 for these otherwise expensive landing cradle attempts. Grasshopper attempts will probably be done first.

If the cradle landing doesn't work, landing legs are needed, or super Draco engines for more a precise landing in the cradle

Phase 2) Raptor engine(s) for S2

Phase 3) Methalox S2 refueling in orbit

Refueling in orbit by another "tanker S2", might make heavier payloads and enough fuel for landing possible with this reusable S2 version.


Phase 4) Change the body to ITS Spaceship form

Landing Legs and Super Draco will make it work with more certainty but are non-essential for ITS development

1/Craddle landing
They don't need to practice cradle landing. I think BFR will have legs in first version land like F9 S1, until they will get confident and will try to land in cradle.

2/Raptor engine
I think definitely try  tested in S2 first, but Raptor is not available now.
My suggested modifications are very small they could try to implement right now.

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