Author Topic: SpaceX Falcon X, Falcon X Heavy, Falcon XX General Discussion Thread  (Read 131026 times)

Offline AncientU

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Isn't the real long pole item Raptor?  I would think the tanks, thrust structure etc. would be pretty straightforward.

M1D is pretty much done, and SuperDraco is a few months from the pad abort test. After that's locked down the propulsion guys will need something to do - if they haven't started modeling it already.  Two questions I have is would M1D's hydroforming construction translate to Raptor production?  Could that speed its development?

Then there is Musk's testimony before the Texas legislature where a factory was mentioned for Brownsville.
bump -- bold mine
How scale-able is the tank and thrust structure design of the F9? Of course, new tooling, bigger assembly building, transportation issues, etc., but is there anything about the fundamental F9 balloon tank design that can't be scaled? And what else of F9 existing technology (avionics, launch facilities or concepts, whatever) can be used for a BFR?
« Last Edit: 10/23/2013 05:06 pm by AncientU »
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Offline Lar

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Isn't the real long pole item Raptor?  I would think the tanks, thrust structure etc. would be pretty straightforward.

M1D is pretty much done, and SuperDraco is a few months from the pad abort test. After that's locked down the propulsion guys will need something to do - if they haven't started modeling it already.  Two questions I have is would M1D's hydroforming construction translate to Raptor production?  Could that speed its development?

Then there is Musk's testimony before the Texas legislature where a factory was mentioned for Brownsville.
bump -- bold mine
How scale-able is the tank and thrust structure design of the F9? Of course, new tooling, bigger assembly building, transportation issues, etc., but is there anything about the fundamental F9 balloon tank design that can't be scaled? And what else of F9 existing technology (avionics, launch facilities or concepts, whatever) can be used for a BFR?
Excellent question, and with today's announcement that SpaceX intends to do Raptor testing at Stennis, a very worthy bump, IMHO.
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Offline Hyperion5

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Isn't the real long pole item Raptor?  I would think the tanks, thrust structure etc. would be pretty straightforward.

M1D is pretty much done, and SuperDraco is a few months from the pad abort test. After that's locked down the propulsion guys will need something to do - if they haven't started modeling it already.  Two questions I have is would M1D's hydroforming construction translate to Raptor production?  Could that speed its development?

Then there is Musk's testimony before the Texas legislature where a factory was mentioned for Brownsville.
bump -- bold mine
How scale-able is the tank and thrust structure design of the F9? Of course, new tooling, bigger assembly building, transportation issues, etc., but is there anything about the fundamental F9 balloon tank design that can't be scaled? And what else of F9 existing technology (avionics, launch facilities or concepts, whatever) can be used for a BFR?

If you're building a dedicated "BFR", you'll probably need new tooling and a bigger assembly building.  You can however use the Falcon 9 avionics and its reusability architecture for the new rocket.  The tanks would have to be larger, as Musk mentioned a 7 meter core as a minimum diameter, not a 3.66 meter core. 

Offline deltaV

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From the methane engine thread:

I think they want 50 tons of cargo to Mars per shot, with no orbital assembly.

Schilling (http://www.silverbirdastronautics.com/LVperform.html) says the following launch vehicle gets 51 tonnes to C3=17 km^2/s^2, which is about what's needed for Mars (http://www.tethers.com/papers/interplanetarymissdeshdbk.pdf, Figure 9 has 16 km^2/s^2 for a "typical" mission; I added 1 km^2/s^2 extra for margin), or 215 tonnes to a 200 km 29 degree low earth orbit:

User-defined launch vehicle
2 stages
no boosters
1st stage: 210 t dry, 4200 t prop, 60718 kN thrust, 350 s vacuum ISP
2nd stage: 20 t dry, 400 t prop, 2891 kN thrust, 375 s vacuum ISP
Cape Canaveral launch
Escape trajectory C3=17 km^2/s^2
Everything else default values

That's twenty-one 650 klbf Raptors on the first stage and one (375/350)*650 klbf Raptor on the second stage. Twenty-one Raptors divides nicely into 3 cores with seven Raptors each. Seven engines is an excellent number of engines since a single engine fits exactly in the middle of a hexagon of engines. (This was mentioned by Lars in the methane engine thread: http://forum.nasaspaceflight.com/index.php?topic=26995.msg1111946#msg1111946 .)

Metane/LOX has an effective density of 828 kg/m^3 (http://www.dunnspace.com/alternate_ssto_propellants.htm Table 1). That 4200 tonnes of first stage prop can be stored for example in three 7-m diameter cylinders that are 44 m tall. Or one 10-m diameter cylinder that's 65 m tall.

In a non-cross-feed boosters configuration with the center core throttled to 70% the performance is increased slightly to 225 tonnes to LEO and 56 tonnes to Mars. Cross-feed would presumably do even better.

BTW 50 tonnes of payload with a Raptor running at 70% throttle gives a burnout acceleration of around 4 gees, which is reasonable but near reasonable limits. Consequently unless Raptor can deep throttle if the launch vehicle is designed to send payloads to Mars without any LEO rendezvous the launch vehicle can't be much smaller than the one in this message.
« Last Edit: 10/24/2013 01:34 am by deltaV »

Offline Lars_J

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deltaV - What would the numbers be for a single core version?

Also, I couldn't resist...  ;D Fun with photoshop - Here is a 7m "MCT" with 7 raptors compared to F9 and FH.
« Last Edit: 10/24/2013 01:47 am by Lars_J »

Offline Hyperion5

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deltaV - What would the numbers be for a single core version?

Also, I couldn't resist...  ;D Fun with photoshop - Here is a 7m "MCT" with 7 raptors compared to F9 and FH.

Very impressive, though given the Raptors' thrust & Isp, it seems like a very large rocket to only get ~ the same payload into LEO as the Falcon Heavy.  If the Raptor is only putting out 293 tf of vac thrust, I would strongly expect that there absolutely has to be a minimum of 7 Raptors on the 1st stage.  I still think 9 is more likely to avoid cannibalizing the Falcon Heavy's market.  Any chance you could create a triple-core heavy version of this rocket? 

Offline deltaV

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deltaV - What would the numbers be for a single core version?

13 tonnes to Mars, 89 tonnes to LEO. Note that all these performance figures are based on a second stage size that I guesstimated to give a reasonable ignition T/W; different choices may lead to different relative performance figures of the light vs. heavy configuration and to LEO vs. to Mars.

A noteworthy comment from another thread:
Don't focus too much on expendable performance; the methane/Raptor vehicle will probably be reusable for the start.

Offline TrevorMonty

A 70t 7 engine FalconXX is now a real possibility. The FH has tested the 50t market and I assume found a market, except nobody wants to be first, still waiting for launch date. Everybody talks about NASA being the only customer for 70-200t LV. Both Russian and China a serious about doing manned missions to moon and neither has a LV to do this. Russian would be a possible customer and don't right China off. Commercial space flights to moon also become viable with these rockets. It does throw a spanner in works in regards to SLS project.

Offline Lars_J

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deltaV - What would the numbers be for a single core version?

Also, I couldn't resist...  ;D Fun with photoshop - Here is a 7m "MCT" with 7 raptors compared to F9 and FH.

Very impressive, though given the Raptors' thrust & Isp, it seems like a very large rocket to only get ~ the same payload into LEO as the Falcon Heavy.  If the Raptor is only putting out 293 tf of vac thrust, I would strongly expect that there absolutely has to be a minimum of 7 Raptors on the 1st stage.  I still think 9 is more likely to avoid cannibalizing the Falcon Heavy's market.  Any chance you could create a triple-core heavy version of this rocket? 

I think cannibalizing FH would be perfectly fine with SpaceX. While larger, it would be a simpler vehicle (7 vs 27 engines), less components, AND easier to reuse. Once this "MCT" entered service, FH would be phased out.

Offline LegendCJS

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deltaV - What would the numbers be for a single core version?

Also, I couldn't resist...  ;D Fun with photoshop - Here is a 7m "MCT" with 7 raptors compared to F9 and FH.

Very impressive, though given the Raptors' thrust & Isp, it seems like a very large rocket to only get ~ the same payload into LEO as the Falcon Heavy.  If the Raptor is only putting out 293 tf of vac thrust, I would strongly expect that there absolutely has to be a minimum of 7 Raptors on the 1st stage.  I still think 9 is more likely to avoid cannibalizing the Falcon Heavy's market.  Any chance you could create a triple-core heavy version of this rocket? 

I think cannibalizing FH would be perfectly fine with SpaceX. While larger, it would be a simpler vehicle (7 vs 27 engines), less components, AND easier to reuse. Once this "MCT" entered service, FH would be phased out.

Indeed, its not like they are averse to ending product lines with new rockets in the same performance class: There is the obvious F9 1.0 to 1.1 example, but also remember that F1 would have been replaced by the F1E before they changed course.
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Offline SpacexULA

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deltaV - What would the numbers be for a single core version?Also, I couldn't resist...  ;D Fun with photoshop - Here is a 7m "MCT" with 7 raptors compared to F9 and FH.

Would there be any advantage to a "Heavy" version of this beast?

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Offline ArbitraryConstant

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Also, I couldn't resist...  ;D Fun with photoshop - Here is a 7m "MCT" with 7 raptors compared to F9 and FH.
That's hot.

Would there be any advantage to a "Heavy" version of this beast?
Similar to FH you'd think.

Offline beancounter

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Also, I couldn't resist...  ;D Fun with photoshop - Here is a 7m "MCT" with 7 raptors compared to F9 and FH.
That's hot.

Would there be any advantage to a "Heavy" version of this beast?
Similar to FH you'd think.
So they replace their 'product' line with 7m cores and Raptor engines?  No more F9, FH, or Merlins.  Raptor ate Merlin!!   ;)
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Offline Lars_J

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Why would it replace F9? If there is a market for it, they would keep it.

Offline beancounter

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Why would it replace F9? If there is a market for it, they would keep it.

I was sort of joshing but more seriously, they would if there was a case for it.  Although the move from F1 to F9 wasn't quite as drastic.  Just saying.
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Offline MikeAtkinson

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If we assume that the MCT is sized as a SSTO Mars-Earth return vehicle, and that the second stage of the launcher is the EDS, and that the EDS is integrated into the MCT, then back-of-the-envelope calculations give the following.

For the return flight:
if you assume 7000 m/s delta-v from Mars' surface to Earth and 380 s Isp, you get a propellant mass fraction of ~0.85. Assume a T/W of 1.5 at take-off, 2.5 MN thrust for a single Raptor and 3.7 m/s2 gravity on Mars. That gives you a gross take-off weight of 450 (metric) tons, out of which 380 tons is propellant.

For the outward flight:
Assume 6000 m/s delta-v and 380 tonnes propellant. Propellant mass fraction ~0.80, gives IMLEO is 475 tonnes. The MCT would launch dry and be refuelled at a propellant depot. At Mars top-of-the-atmosphere mass would be about 150 tonnes, 55 tonnes of which is propellant for landing from about Mach 5.

If we guess that the stage + ship has a dry mass of 50 tonnes, playload Earth-Mars is 45 tonnes and Mars-Earth is 20 tonnes.

The MCT
Single Raptor engine. About 40m long and 10m diameter of approximately fairing shape. Direct entry at Mars, aero-brakes to about Mach 5, then uses propulsive descent. [vertical or horizontal landing?]

Aero-brakes into Earth LEO on return, small amount of propellant used to circularize orbit below radiation belts. Refuelled and refurbished for future missions. [or perhaps lands back on Earth?]

The Launcher
Launcher needed is 95 tonnes to LEO for the integrated stage+ship and payload, as the stage part is 20 tonnes, the launcher is in the 75 tonnes/LEO range. So assuming 30% payload loss for 1st stage reuse that is about 110 tonnes to LEO non-reusable. Assume a 2nd stage reuse penalty of 50% and a tanker version of the 2nd stage, this can place about 37 tonnes of fuel into LEO.

This is similar to the performance a 9 Raptor 1st stage would give.

So each Mars mission would consist of one MCT launch and 11 tanker flights. [Alternatively, a heavy version could place about 110 tonnes of fuel into LEO so 3 or 4 heavy launches would be needed]

[Some of these calculations were initially done by Joel]

Offline GalacticIntruder

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If we assume that the MCT is sized as a SSTO Mars-Earth return vehicle, and that the second stage of the launcher is the EDS, and that the EDS is integrated into the MCT, then back-of-the-envelope calculations give the following.

For the return flight:
if you assume 7000 m/s delta-v from Mars' surface to Earth and 380 s Isp, you get a propellant mass fraction of ~0.85. Assume a T/W of 1.5 at take-off, 2.5 MN thrust for a single Raptor and 3.7 m/s2 gravity on Mars. That gives you a gross take-off weight of 450 (metric) tons, out of which 380 tons is propellant.

For the outward flight:
Assume 6000 m/s delta-v and 380 tonnes propellant. Propellant mass fraction ~0.80, gives IMLEO is 475 tonnes. The MCT would launch dry and be refuelled at a propellant depot. At Mars top-of-the-atmosphere mass would be about 150 tonnes, 55 tonnes of which is propellant for landing from about Mach 5.

If we guess that the stage + ship has a dry mass of 50 tonnes, playload Earth-Mars is 45 tonnes and Mars-Earth is 20 tonnes.

The MCT
Single Raptor engine. About 40m long and 10m diameter of approximately fairing shape. Direct entry at Mars, aero-brakes to about Mach 5, then uses propulsive descent. [vertical or horizontal landing?]

Aero-brakes into Earth LEO on return, small amount of propellant used to circularize orbit below radiation belts. Refuelled and refurbished for future missions. [or perhaps lands back on Earth?]

The Launcher
Launcher needed is 95 tonnes to LEO for the integrated stage+ship and payload, as the stage part is 20 tonnes, the launcher is in the 75 tonnes/LEO range. So assuming 30% payload loss for 1st stage reuse that is about 110 tonnes to LEO non-reusable. Assume a 2nd stage reuse penalty of 50% and a tanker version of the 2nd stage, this can place about 37 tonnes of fuel into LEO.

This is similar to the performance a 9 Raptor 1st stage would give.

So each Mars mission would consist of one MCT launch and 11 tanker flights. [Alternatively, a heavy version could place about 110 tonnes of fuel into LEO so 3 or 4 heavy launches would be needed]

[Some of these calculations were initially done by Joel]


There is a MCT thread if anyone wants to look at those concepts.

http://forum.nasaspaceflight.com/index.php?topic=30103.msg968341#msg968341
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Offline majormajor42

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Why would it replace F9? If there is a market for it, they would keep it.

I was sort of joshing but more seriously, they would if there was a case for it.  Although the move from F1 to F9 wasn't quite as drastic.  Just saying.

MCT speculation is that it will be built near the launch site, from what I've read. The launch site they are refering to is FL, yes? I don't think they will build them and launch them out of TX and VAFB as well. Then there is also the Hawthorne factory floor. All that area just to build Raptor engines? No, I think F9R remains. It will may be cheap enough for them to operate alongside MCT. Plus, MCT doesn't push out much in the way of F9R infrustructure, so it doesn't have to be a one or the other choice.

Of course, with reusability on the way, it is hard to look too far into the future of the F9R and how they operate it, and how many new cores they will have to continue to build in the future. So the equation of  whether it makes sense to continue to operate the F9R after MCT is in service is missing some of the known values at this point.
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