Author Topic: SpaceX Falcon Heavy Discussion (Thread 3)  (Read 332197 times)

Offline Ben the Space Brit

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #440 on: 05/12/2015 02:47 pm »
IF, big if, they did make a Methane Merlin and directly replaced the kerosene on the Falcon 9, (of course they would have to adjust tank size via the common bulkhead), what kind of performance would the Falcon 9 and Falcon H have?

Please see Hyperion5's post here.
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Offline spacenut

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #441 on: 05/12/2015 06:18 pm »
Wow.  That is a fairly large increase.  24.9 tons on Falcon 9 and 78.1 on Falcon H (with crossfeed).  Without crossfeed would probably be about 65 tons to LEO.  Seems to me they should do that.  The MCT could benefit from the lower powered engines for landing on Mars with only 40% of earths gravity.  They could also benefit by being able to launch satelites to higher orbits.  Most of the same tooling for making Falcon 9 and Falcon H can be used.  The only change I see is a longer methane tank and a shorter oxygen tank than the kerolox version.  The other would be a turbopump issue for the methane vs kerosene.  Plumbing might be little different diameter.  Also, methane is only a few degrees different in liquid form than lox, so equipment would be almost identical to handle both, not like the super cold hydrogen. 

Sorry I missed that the first time. 

Offline Owlon

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #442 on: 05/12/2015 06:19 pm »
IF, big if, they did make a Methane Merlin and directly replaced the kerosene on the Falcon 9, (of course they would have to adjust tank size via the common bulkhead), what kind of performance would the Falcon 9 and Falcon H have?

Please see Hyperion5's post here.

That assumes replacing the gas generator Merlin with a "mini Raptor" methane staged combustion engine that has equal thrust to Merlin. Replacing the current Merlin with an equivalent gas generator methane engine would probably give you a small decrease in performance, since methane's ~20% lower bulk density will have a slightly larger impact than the ~4% increase in ISP you get. There are some advantages to switching to methane, but you really need an entirely new high performance engine to make a big difference.

Offline baldusi

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #443 on: 05/12/2015 08:33 pm »
Please review this pictures of the Angara-3 cross-feed preliminary design.

Well I disagree with your comments about shortcomings with my design, I am glad you posted the Angara pictures. Without understanding Russian, it is clear that tank-to-tank cross flow is viable (which I didn't think it was). Clearly by pressurizing the outboard booster tanks and not the central ones, sufficient fuel will flow from the outboard tanks to the central ones to power the central engine. The diagram shows the central tanks remaining completely full.
Instead of a spool 3-way valve, you should use two on/off valves (one for in-core tank, one for booster incoming flow), a one way valve after the booster incoming flow valve to close the circuit after separation. And another one-way valve before the in core flow valve to avoid back flow. And somehow design the piping in such a way that it leaves no bubbles (or ad a heavy gas trap). Also, you should make sure that the process of opening one valve and close the other can comply with two requirements: no head pressure drop below the minimum engine specified AND generates no turbulence that may end up in cavitation.
I don't know what's your experience with cryo liquids, but it's not that easy (but totally doable). Just not possible with a 3-way valve (which are specially heavy for big diameter piping.

Offline Lobo

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #444 on: 05/12/2015 11:15 pm »
IF, big if, they did make a Methane Merlin and directly replaced the kerosene on the Falcon 9, (of course they would have to adjust tank size via the common bulkhead), what kind of performance would the Falcon 9 and Falcon H have?

Please see Hyperion5's post here.

That assumes replacing the gas generator Merlin with a "mini Raptor" methane staged combustion engine that has equal thrust to Merlin. Replacing the current Merlin with an equivalent gas generator methane engine would probably give you a small decrease in performance, since methane's ~20% lower bulk density will have a slightly larger impact than the ~4% increase in ISP you get. There are some advantages to switching to methane, but you really need an entirely new high performance engine to make a big difference.

Agreed.  They -could- do it, but I don't know that they will.  I think these latest "v1.2" Falcon upgrades will make F9 and FH pretty much cover the commercial and goverment sat market with full reusability.  (Maybe an expended FH core for a rare big DoD bird).

All their pads will be set up for only kerolox, and they've invested a lot into the F9 cores as they will now be, as well as the latest itteration of Merlin.  If they every do entertain a methalox version of Merlin, or a "mini-raptor", I can't see it being for quite some time.  It's not needed performance wise because they will already be hitting their market goals, RP-1 isn't really significantly more expensive than LCH4 I don't think, I think the F9 core is already at the limit for what can be transported on the roadways...methalox would likely need to be a little longer or wider, and their R&D budgets are better spent on MCT and associated developments.

Offline groundbound

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #445 on: 05/13/2015 05:16 am »
Note that a lot of those conclusions are partly because of the severe US  size restraints. Though this goes against what we know of SpaceX' plans, there is a confluence of changes that they might undertake some years down the road.

Larger "hammerhead" FH upper stage + methalox  US + early start of BFR factory + methane infrastructure at future BFR pad. 

This would let them spread out some of the capital intensive activities eventually required for BFR and yield a little extra revenue during final BFR/MCT development.  Shipping a single engine and other subassemblies from Hawthorne for final US assembly is not a dealbreaker. And a few years down the road, an FH variant with a very high energy upper stage that is limited to just one of their pads might give them some additional capability without being too much of a diversion of capital and focus.

Offline guckyfan

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #446 on: 05/13/2015 05:51 am »
I don't think they will do a methalox version of Falcon. If and when it looks like competition (Blue Origin) comes up with a competetive fully reusable launch archictecture they may built a new intermediate archictecture. Something like a 9 (or 7) Raptor first stage with a single Raptor upper stage. That would cover the whole range of payloads the Falcon family can now fly. Bigger diameter and not road transportable won't matter much with a fully reusable system.

Offline baldusi

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #447 on: 05/13/2015 12:43 pm »
Do you guys think they will develop a methane Merlin?  If so, what performance increase to GTO would that bring to Falcon Heavy with a properly sized upper stage, (stretched if need be)?

They might, though if you're going to go "all-methalox", you generally want a big increase in performance to compensate for the rocket's increased dry mass and production costs.  That's why I would suggest something like the following:

Detailed figures on both Falcon 9-M & Falcon Heavy-M below:
RocketFalcon 9-MFalcon Heavy-M (cross-feed)
Payload to LEO24.93 mt78.16 mt
Gross Mass446 mt1262.99 mt
Diameter3.66 m3.66 m x 3
SI Gross Mass358.47 mt763.77 mt
SI Propellant Mass 335.06 mt716.94 mt
SI Engines9xMini-Raptor27xMini-Raptor
SI SL Thrust576 tf1728 tf
SI Vac Thrust651.4 tf1954.2 tf
SI Engine Isp321/363321/363
SII Gross Mass60.90 mt358.47 mt
SII Propellant Mass56.80 mt335.06 mt
SII SL  ThrustN/A576 tf
SII Vac Thrust70 tf651.4 tf
SII Engine Isp380321/363
SIII Gross MassN/A60.90 mt
SIII Propellant MassN/A56.80 mt
SIII Vac ThrustN/A70 tf
SIII IspN/A380
PLF Mass1.70 mt1.70 mt
PLF separation time (sec.)220220
Have Dimitry done any simulation an an Falcon 9 v1.2 M? I suspect it might cover Delta IV Heavy payloads in expendable mode.

Offline Graham

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #448 on: 05/13/2015 08:21 pm »
In this video from the Planetary Society:   
Bill Nye and others are discussing the launch of Light Sail on the Falcon Heavy, Bill Nye states that it will be the first flight of the FH. Does TPS know something we don't, given that they are customers (i.e. the first flight is now 2016) or is Mr. Nye mistaken?
« Last Edit: 05/13/2015 08:22 pm by Graham »
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Offline Roy_H

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #449 on: 05/13/2015 08:56 pm »
Please review this pictures of the Angara-3 cross-feed preliminary design.

Well I disagree with your comments about shortcomings with my design, I am glad you posted the Angara pictures. Without understanding Russian, it is clear that tank-to-tank cross flow is viable (which I didn't think it was). Clearly by pressurizing the outboard booster tanks and not the central ones, sufficient fuel will flow from the outboard tanks to the central ones to power the central engine. The diagram shows the central tanks remaining completely full.
Instead of a spool 3-way valve, you should use two on/off valves (one for in-core tank, one for booster incoming flow), a one way valve after the booster incoming flow valve to close the circuit after separation. And another one-way valve before the in core flow valve to avoid back flow. And somehow design the piping in such a way that it leaves no bubbles (or ad a heavy gas trap). Also, you should make sure that the process of opening one valve and close the other can comply with two requirements: no head pressure drop below the minimum engine specified AND generates no turbulence that may end up in cavitation.
I don't know what's your experience with cryo liquids, but it's not that easy (but totally doable). Just not possible with a 3-way valve (which are specially heavy for big diameter piping.

Well, I didn't want to get into a spitting match with you, but here goes. If you use separate valves as you propose then you will have to have manifolding where the two pipes from the valves to the turbo pumps join, thus creating an edge that will cause turbulence and a dead-end tube. You specifically said "somehow" this must be avoided. Using one spool valve is the answer to this problem. The spool valve allows the flow from tank to turbo pumps to be continuous and free of sharp bends (of the type common in one-way valves). Why are you concerned about back flow from outer tanks to central tank? First this is extremely unlikely and could only happen during the less than 1 second transition time of valve actuation. second if some were to get from the external to the core, that would be a good thing wouldn't it? At time of transition,  I would expect all engines to be throttled down for booster separation so maximum flow is not required, but as one path is being closed, from the external tanks the other path to the central tank is opening, so at no time are the turbo tanks pumps starved. During this transition time there will be significant flow from the external tanks with high inertia, I think concerns of the flow starting up from the central tank being strong enough to overcome the turbo pump requirements and then push against the high inertia momentum is near impossible. Adding a check valve is just needless complication as the path will be closed by the spool valve, and as I said before it is difficult to design a check valve that does not increase turbulence. Even if the impossible happened, how much fuel would be lost in that fraction of a second?
« Last Edit: 05/14/2015 02:55 am by Roy_H »
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Offline rst

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #450 on: 05/13/2015 09:21 pm »
In this video from the Planetary Society ...
Bill Nye and others are discussing the launch of Light Sail on the Falcon Heavy, Bill Nye states that it will be the first flight of the FH. Does TPS know something we don't, given that they are customers (i.e. the first flight is now 2016) or is Mr. Nye mistaken?

FWIW, references to FH start at about the 3:30 mark, and include CG video.  More details on the mission are at the kickstarter page:

https://www.kickstarter.com/projects/theplanetarysociety/lightsail-a-revolutionary-solar-sailing-spacecraft

which mentions that the sail will be carried by yet another experimental spacecraft (PROX-1 from Georgia Tech); all are pretty specific about FH being the launch vehicle.

One presumes that these are secondary payloads; nothing here says much specific about the primary, though.

Offline Graham

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #451 on: 05/13/2015 11:07 pm »
In this video from the Planetary Society ...
Bill Nye and others are discussing the launch of Light Sail on the Falcon Heavy, Bill Nye states that it will be the first flight of the FH. Does TPS know something we don't, given that they are customers (i.e. the first flight is now 2016) or is Mr. Nye mistaken?

FWIW, references to FH start at about the 3:30 mark, and include CG video.  More details on the mission are at the kickstarter page:

https://www.kickstarter.com/projects/theplanetarysociety/lightsail-a-revolutionary-solar-sailing-spacecraft

which mentions that the sail will be carried by yet another experimental spacecraft (PROX-1 from Georgia Tech); all are pretty specific about FH being the launch vehicle.

One presumes that these are secondary payloads; nothing here says much specific about the primary, though.
During the Light Sail reveal event last year it was stated that PROX- 1 would be a secondary payload. I was under the impression that SpaceX was still aiming to fly the demo mission by the end of 2015, but Mr. Nye states that Light Sail will fly on the first flight of the FH in 2016. I'm just wondering if anyone here has heard if the demo mission has shifted to the right or if Mr. Nye mispoke.
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Offline eriblo

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #452 on: 05/13/2015 11:27 pm »
In this video from the Planetary Society ...
Bill Nye and others are discussing the launch of Light Sail on the Falcon Heavy, Bill Nye states that it will be the first flight of the FH. Does TPS know something we don't, given that they are customers (i.e. the first flight is now 2016) or is Mr. Nye mistaken?

FWIW, references to FH start at about the 3:30 mark, and include CG video.  More details on the mission are at the kickstarter page:

https://www.kickstarter.com/projects/theplanetarysociety/lightsail-a-revolutionary-solar-sailing-spacecraft

which mentions that the sail will be carried by yet another experimental spacecraft (PROX-1 from Georgia Tech); all are pretty specific about FH being the launch vehicle.

One presumes that these are secondary payloads; nothing here says much specific about the primary, though.
During the Light Sail reveal event last year it was stated that PROX- 1 would be a secondary payload. I was under the impression that SpaceX was still aiming to fly the demo mission by the end of 2015, but Mr. Nye states that Light Sail will fly on the first flight of the FH in 2016. I'm just wondering if anyone here has heard if the demo mission has shifted to the right or if Mr. Nye mispoke.
He didn't misspeak, he just left out "operational" (as stated in the Kickstarter campaign description and likely elsewhere).
« Last Edit: 05/13/2015 11:31 pm by eriblo »

Offline Robotbeat

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #453 on: 05/13/2015 11:31 pm »
Love Bill Nye, but I don't hang on every word he says when it's about something very technical.
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Offline Graham

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #454 on: 05/13/2015 11:38 pm »
In this video from the Planetary Society ...
Bill Nye and others are discussing the launch of Light Sail on the Falcon Heavy, Bill Nye states that it will be the first flight of the FH. Does TPS know something we don't, given that they are customers (i.e. the first flight is now 2016) or is Mr. Nye mistaken?

FWIW, references to FH start at about the 3:30 mark, and include CG video.  More details on the mission are at the kickstarter page:

https://www.kickstarter.com/projects/theplanetarysociety/lightsail-a-revolutionary-solar-sailing-spacecraft

which mentions that the sail will be carried by yet another experimental spacecraft (PROX-1 from Georgia Tech); all are pretty specific about FH being the launch vehicle.

One presumes that these are secondary payloads; nothing here says much specific about the primary, though.
During the Light Sail reveal event last year it was stated that PROX- 1 would be a secondary payload. I was under the impression that SpaceX was still aiming to fly the demo mission by the end of 2015, but Mr. Nye states that Light Sail will fly on the first flight of the FH in 2016. I'm just wondering if anyone here has heard if the demo mission has shifted to the right or if Mr. Nye mispoke.
He didn't misspeak, he just left out "operational" (as stated in the Kickstarter campaign description and likely elsewhere).
Thanks, I must have missed that in the Kickstarter description. I figured that that was what he meant, but I wasn't sure.

Love Bill Nye, but I don't hang on every word he says when it's about something very technical.
I would agree with that, but I do love his enthusiasm
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Offline DanseMacabre

Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #455 on: 05/20/2015 06:04 pm »
http://spacenews.com/viasat-sees-falcon-heavy-as-pacing-item-in-growth-plans/

Seems to also indicate a FH first flight in 2016. Additionally that's a blimmin' aspirational manifest! Launching a commercial payload so soon following the inaugural flight.

Offline paulcpaulc

Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #456 on: 05/31/2015 10:21 pm »
The recent F9H video showed black legs and leg nacelles...


Is this extra thermal protection than we have had to date?

Does anyone know when we might see this leg configuration for the first time? Perhaps on a "regular" F9 launch soon?

Thanks,
Paul.

Offline cscott

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #457 on: 06/01/2015 04:53 am »
The SpaceX illustrations of their rockets always have black trim---look at interstage of the F9 on spacex.com for example---but the flying versions have been all-white.  Dunno why, it's a (very minor) mystery.

I'd expect the actual FH to be all white as well.  Note that the legs of the illustration at http://www.spacex.com/falcon-heavy are all-white---but with the same odd never-actually-seen-on-a-real-rocket black interstage as they illustrate on the F9.

I think they are using black to indicate "composite construction", not implying that the actual rocket would be painted black in that way.
« Last Edit: 06/01/2015 04:58 am by cscott »

Offline deruch

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #458 on: 06/01/2015 05:23 am »
The recent F9H video showed black legs and leg nacelles...
Is this extra thermal protection than we have had to date?
Does anyone know when we might see this leg configuration for the first time? Perhaps on a "regular" F9 launch soon?

Thanks,
Paul.

I always assumed that SpaceX intentionally used this "irregular" coloring scheme to easily differentiate between actual pictures and renderings/models.  Though I like cscott's notion that it might represent composites, too.
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Offline Kabloona

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Re: SpaceX Falcon Heavy Discussion (Thread 3)
« Reply #459 on: 06/01/2015 05:02 pm »
The recent F9H video showed black legs and leg nacelles...
Is this extra thermal protection than we have had to date?
Does anyone know when we might see this leg configuration for the first time? Perhaps on a "regular" F9 launch soon?

Thanks,
Paul.

I always assumed that SpaceX intentionally used this "irregular" coloring scheme to easily differentiate between actual pictures and renderings/models.  Though I like cscott's notion that it might represent composites, too.

Changing to a black color scheme for the legs and aft end of the stage might make sense once re-use becomes standard procedure. We've seen how the aft end gets sooted/scorched during retro burn, and black paint might cover scorch marks up for reuse better than white paint.

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