Author Topic: Describe a Perfect Earth Departure Stage for FH  (Read 34232 times)

Offline TomH

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Describe a Perfect Earth Departure Stage for FH
« on: 11/27/2014 05:42 am »
In other threads that are not SpaceX or Falcon specific, members have compared FH favorably to SLS in mt to LEO, but not so well in mt to Luna or Mars. IMHO, this has much to do with the fact that the Falcon US is designed as a 2nd stage to LEO, not as an EDS.

Elon will not be designing an EDS for FH as his designs on Mars involve a massive MCT, which requires Raptor BFR and some Earth Departure system much larger than could be suitable for FH.

I know there are numerous cost, political, and technical reasons this will not happen, but for the fun of an intellectual exercise, assume someone wanted to use FH as a platform to deep space and intended to design the ideal high-energy, high ISP Earth Departure Stage to go atop FH.

Would this stage look like Centaur, Delta US, ACES, a slimmed down EUS? Would it be H2 or CH4? Would it be purely EDS (departing from parking orbit on its first burn) or would it be something like the S-IVB on Saturn V, completing parking orbit on first burn and departing LEO on 2nd burn? Assume you wanted it to be capable of both TLI and TMI. What engines would you employ: RL-10, J-2X, MB-60, a new Methalox engine smaller than BE-4? Would you eliminate the current Falcon 2nd stage, or place this atop that?

Offline Damon Hill

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #1 on: 11/27/2014 06:33 am »
What sort of payloads to what destinations?   The mission will dictate energy requirements, which could be very substantial.

SpaceX is apparently going with methane for future systems and that should go better with ground support, otherwise I'd consider a wide-body Centaur or ACES and Integrated Vehicle Fluids for Lunar payloads.  But I'm a hydrogen enthusiast.  Methane, if IVF can be made to work with it, might simply be less expensive and good enough.

I think I'd like a high energy stage as the third stage, using the FH second stage to achieve LEO for a fully fueled HES; I'm guessing the former's high thrust would minimize orbital insertion gravity loss, but the tradeoffs with methane's higher thrust might work out differently.

An orbiter for the outer planets and a medium-heavy payload for direct delivery to Lunar surface would seem to have very different requirements.
« Last Edit: 11/27/2014 06:40 am by Damon Hill »

Offline Jim

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #2 on: 11/27/2014 11:42 am »
Would you eliminate the current Falcon 2nd stage, or place this atop that?

You don't add one, you eliminate the current 2nd stage.

Offline Dave G

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #3 on: 11/27/2014 11:56 am »
Here's a question:  Could they simply stretch the current 2nd stage with the same Merlin 1D engine?

That seems like a very easy change, but I'm not sure how it works in the simulator.

Offline vulture4

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #4 on: 11/27/2014 02:38 pm »
I think the question is whether one should depart directly from earth or assemble and fuel the mission in LEO. In either case cost is a primary consideration. For a planetary probe, direct departure may be the simplest strategy and the mission can be designed to meet the mass requirements of the launch vehicle. A third stage added to the FH might be the optimal strategy since the existing second stage has the higher thrust needed to maximize payload mass during ascent. The third stage could take the form of a Centaur for direct injection into a departure trajectory. Stretching the existing second stage is an alternative but would not provide as much performance as the Centaur, which has less thrust but very high specific impulse. This would require a supply of LH2 at LC-39, but maybe the old hydrogen sphere could be used.

Alternatively, a solar-electric third stage could be used for a slower spiral departure from LEO but a faster final velocity.

For a manned flight to the Moon or Mars my feeling is that assembly and fueling in LEO is more practical than direct departure. All materials for the mission would first be carried as payload to LEO. This means optimizing payload to LEO, which the existing FH is designed to do. The payloads can be propellants, modules, or fueled or unfueled departure stages. If cryogens are used we would need an actively cooled propellant storage depot in LEO. Another strategy is to carry water to orbit, split it by electrolysis as needed and liquify the H2 and O2 for fueling departing vehicles. Finally, with appropriate investment now, it's entirely possible that even for manned vehicles SEP will exceed the performance of chemcal propulsion.
« Last Edit: 11/27/2014 03:00 pm by vulture4 »

Offline Patchouli

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #5 on: 11/27/2014 02:50 pm »
Probably a simple pressure fed upper stage using one or two Kestrel engines as this would match Spacex's habit of doing things in house.
Plus fluids commonality with the other two stages.


Offline Dave G

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #6 on: 11/27/2014 03:10 pm »
For a manned flight to the Moon or Mars my feeling is that assembly and fueling in LEO is more practical than direct departure.

I agree, although I might replace the words "assembly and fueling" with "rendezvous" or "docking".  More complicated procedures in LEO would take some time to work out, so that would probably delay a manned Mars mission.  Docking multiple modules together before TMI seems a lot simpler.

Apollo got us used to the idea of 1 rocket launch per mission, but even back then they considered Earth orbit rendezvous (EOR).  For the first manned Mars mission, I suspect the best solution will involve rendezvous in both Earth orbit and Mars orbit. 
« Last Edit: 11/27/2014 03:11 pm by Dave G »

Offline Lars-J

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Describe a Perfect Earth Departure Stage for FH
« Reply #7 on: 11/27/2014 03:19 pm »
Probably a simple pressure fed upper stage using one or two Kestrel engines as this would match Spacex's habit of doing things in house.
Plus fluids commonality with the other two stages.

Unless a hypothetical 3rd stage has mind-blowingly great Isp, it will never make sense. Stretching the upper stage will always be more mass *and* cost efficient.

Replacing the upper stage with something else entirely - like a methane upper stage - would make the most sense if SpaceX planned on using FH for Mars missions.
« Last Edit: 11/27/2014 03:27 pm by Lars-J »

Offline clongton

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #8 on: 11/27/2014 03:57 pm »
SpaceX needs to be at least thinking about these kinds of things very early on, like now even, because it ripples all the way back to the launch vehicle. Since the launch vehicle is already designed, I tend to think that there will not be a new upper stage so I am leaning toward a third kick stage for these spacecraft. While our current experience gives LH2 the nod as the propellant of choice, I suspect that SpaceX will stick with CH4 and use that propellant for in-space engines.
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Offline Patchouli

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #9 on: 11/27/2014 04:00 pm »


Unless a hypothetical 3rd stage has mind-blowingly great Isp, it will never make sense. Stretching the upper stage will always be more mass *and* cost efficient.

Replacing the upper stage with something else entirely - like a methane upper stage - would make the most sense if SpaceX planned on using FH for Mars missions.

Not necessarily true esp if the upper stage is made recoverable.
The dry mass of the F9 second stage is something around 5,000kg stretching it would make this more.
Even something relative low ISP like a PAM type solid stage would significantly increase the GTO payload vs having to carry the dry mass of the second stage through GTO.

For a second stage stretch to have higher performance you pretty much need something with the ISP and mass fractions of a Centaur.

Of course it all boils down to cost as sometimes the best possible payload mass fraction does not equal the best possible cost.
« Last Edit: 11/27/2014 05:37 pm by Patchouli »

Offline cambrianera

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #10 on: 11/27/2014 04:34 pm »
Dry mass of second stage should be about 4000 kg.
A two meter stretch should add only 300 kg of dry mass for additional  20000 kg of propellant.
A stretch of second stage seems far easier than a third stage and quite good for performance still using MVac.

http://forum.nasaspaceflight.com/index.php?topic=36045.msg1285819#msg1285819
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Offline nimbostratus

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #11 on: 11/27/2014 04:40 pm »
Dry mass of second stage should be about 4000 kg.
A two meter stretch should add only 300 kg of dry mass for additional  20000 kg of propellant.
A stretch of second stage seems far easier than a third stage and quite good for performance still using MVac.

http://forum.nasaspaceflight.com/index.php?topic=36045.msg1285819#msg1285819
With the additional propellant, are current 9 merlins enough to lift all the mass?
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Offline Robotbeat

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #12 on: 11/27/2014 04:48 pm »
Yes. Merlin 1D has room to increase throttle, too.
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Offline Tomness

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #13 on: 11/27/2014 04:59 pm »
Would you eliminate the current Falcon 2nd stage, or place this atop that?

You don't add one, you eliminate the current 2nd stage.

As Jim has said Merlin is good engine just undersized for 1st Stage and way undersized 2nd stage. Will they ever Marvel Team up Blue and put BE-3U on FH 1 stage & make an awesome Departure Rocket? Doubt it, they did do studies with Merlin 2 & Rapture when it was H2 + O2 stage for FH
PS this is kinda of a duplicate thread with Falcon 9 3rd stage possibly be merged.

Offline cambrianera

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #14 on: 11/27/2014 05:00 pm »
Dry mass of second stage should be about 4000 kg.
A two meter stretch should add only 300 kg of dry mass for additional  20000 kg of propellant.
A stretch of second stage seems far easier than a third stage and quite good for performance still using MVac.

http://forum.nasaspaceflight.com/index.php?topic=36045.msg1285819#msg1285819
With the additional propellant, are current 9 merlins enough to lift all the mass?
Extra 20000 kg are about 3.5% of GLOW for F9, something like 1% for FH.
Both rockets have very good T/W.
No problem at liftoff, also without the extra thrust that will be available in merlins (as reminded by Robotbeat).
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Offline nadreck

Re: Describe a Perfect Earth Departure Stage for FH
« Reply #15 on: 11/27/2014 05:29 pm »
I would presume change out the current upper stage to one that is about 1.6 times the current proposed size of a FH US with the same engine and the limited sized DS probe (2000 kg). Cheapest all around solution presuming engine relight before we lose to much Lox.

Alternately, far more costly, and a slightly more operationally risky, but more efficient and flexible in terms of ultimate payload sizes and mission specs:

Design a stage to ride on top of the existing US that is very loosely based on the current US and Dragon 2 trunk RCS and solar panels that can mate with a separately launched payload, in tandem to another one like itself, or connect sideways to two other ones like it. This version should be H2/LOX and have an engine equivalent to the HM-7B. Besides avionics, and solar panels it should have (possibly discardible) reliquifaction equipment. One can envisage easily any number between 1 and 4 of these being used with virtually any sized payload to provide a very flexible BEO program base.
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Offline S.Paulissen

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #16 on: 11/27/2014 05:32 pm »
Would you eliminate the current Falcon 2nd stage, or place this atop that?

You don't add one, you eliminate the current 2nd stage.

As Jim has said Merlin is good engine just undersized for 1st Stage and way undersized 2nd stage. Will they ever Marvel Team up Blue and put BE-3U on FH 1 stage & make an awesome Departure Rocket? Doubt it, they did do studies with Merlin 2 & Rapture when it was H2 + O2 stage for FH
PS this is kinda of a duplicate thread with Falcon 9 3rd stage possibly be merged.

Your sentence is unclear; Merlin 1D is undersized for the first stage, yes, that's why they use nine of them.  However, Jim said (and I agree) that the entire upper stage is undersized, in part, because Merlin 1D vac is oversized for the second stage.  It (the stage) has a very high thrust to dry mass ratio.

EDIT: Also, we're losing sight of the thread.  He's asking what's YOUR perfect upper stage(s), not what would the most likely for SpaceX to do.  We have enough of that speculation already.  Of course "perfect" is in the eye of the beholder in this case.  Many would optimize performance, others cost, others manufactuability.
« Last Edit: 11/27/2014 05:37 pm by Exclavion »
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Offline Ben the Space Brit

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #17 on: 11/27/2014 06:49 pm »
I'm no expert but I'd want to see if I could throw together something using MB-60. Diameter would be the same as the PLF and, ideally, it could also be equipped with Dragon solar arrays to run a ZBO LOX circulation plant to maximise on-orbit loiter.

If that isn't possible, see if it was possible to build a Merlin-1m-VAC using LCH4 instead of RP1.
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Offline AncientU

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #18 on: 11/27/2014 10:13 pm »
Probably a simple pressure fed upper stage using one or two Kestrel engines as this would match Spacex's habit of doing things in house.
Plus fluids commonality with the other two stages.

Unless a hypothetical 3rd stage has mind-blowingly great Isp, it will never make sense. Stretching the upper stage will always be more mass *and* cost efficient.

Replacing the upper stage with something else entirely - like a methane upper stage - would make the most sense if SpaceX planned on using FH for Mars missions.

This methane upper is the perfect Earth departure stage with one caveat... it must be capable of being refueled on orbit.  A slightly modified upper could become the (reusable) tanker.  Now, where is that mini-raptor we need?
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Offline MATTBLAK

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #19 on: 11/27/2014 10:29 pm »
I dunno about a 'perfect' Earth Departure Stage, but I'm thinking of a stage derived from Falcon second stage tooling or maybe the 'Long Trunk' Dragon concept, fueled by hypergolics and powered by a set of 8x restartable 'Super Draco' thrusters - a Dragon 2 propulsion set. Hypergolics have proven long term in space storage abilities and a specific impulse not much 'worse' than LOX/CH4. I'd also put a docking 'cage mechanism at the front of these stages so they could be deployed inline in a 'train' for staged firings. And design them for a mass that can be launched on a standard Falcon Heavy - about 50 tons with more than 40 tons of that propellant. I imagine a trio of these stages would have enough oomph to get a nearly 40 metric ton load on a low energy Trans Mars Injection.

Of course; pump-fed LOX/Methane would be better and could use larger stages when topped up with 'tankers'.
« Last Edit: 11/27/2014 10:44 pm by MATTBLAK »
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Offline AncientU

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #20 on: 11/28/2014 12:16 am »
The 3.66m diameter second stage would also be changed to 5.2m, flush with the current fairing.  This would allow for increased tank volume for liquid methane and also could max out the capabilities of the first stage and boosters on the FH.  Earlier calculations showed this configuration could deliver 70+mT to LEO...

Edit: added reference below:
http://forum.nasaspaceflight.com/index.php?topic=32620.msg1085280#msg1085280

Quote
Falcon Heavy (raptor)    Reusable   Expendable
Payload to LEO, kg      59'000      75'000
« Last Edit: 11/28/2014 12:48 am by AncientU »
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Offline Danderman

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #21 on: 11/28/2014 12:37 am »
An EDS powered  by the Blue Origin 100,000 lb thrust LH2 engine comes to mind.

Offline savuporo

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #22 on: 11/28/2014 02:22 am »
Quote
What sort of payloads to what destinations?   The mission will dictate energy requirements, which could be very substantial.

If this rocket is actually planned to go places, a highly modular third stage option might actually make sense. Cluster of Star-48 pushed small asteroid probes. An ion engine slow tug. Maximum performance one-way lox/lh2 rocket with short mission life but maximum TLI/TMI throw. Long duration methalox potentially re-fuellable but lower performing stage.
All depends on a mission and it's highly unlikely that SpaceX would be building all these on their own, so third stage would maybe not be a bad option.
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Offline Robotbeat

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #23 on: 11/28/2014 04:15 am »
Best idea for a perfect departure stage is whatever has sufficient performance and is cheapest. Chances are, that's /probably/ an existing FH upper stage.
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Offline MATTBLAK

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #24 on: 11/28/2014 04:27 am »
Best idea for a perfect departure stage is whatever has sufficient performance and is cheapest. Chances are, that's /probably/ an existing FH upper stage.

Yup - maybe the Falcon second stage could refuel itself from a LOX/RP1 or LOX/CH4 'drop tanks', carried as the principle cargo? And if this refuellable stage had the drop tanks contained within a docking cage - that opened wide enough to eject those empty tanks - then that stage could possibly combine itself with others to form an 'Inline Train' for staged burnings; as I mentioned previously.
« Last Edit: 12/10/2014 09:50 am by MATTBLAK »
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Offline Hyperion5

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #25 on: 11/28/2014 05:12 am »
Would you eliminate the current Falcon 2nd stage, or place this atop that?

You don't add one, you eliminate the current 2nd stage.

As Jim has said Merlin is good engine just undersized for 1st Stage and way undersized 2nd stage. Will they ever Marvel Team up Blue and put BE-3U on FH 1 stage & make an awesome Departure Rocket? Doubt it, they did do studies with Merlin 2 & Rapture when it was H2 + O2 stage for FH
PS this is kinda of a duplicate thread with Falcon 9 3rd stage possibly be merged.

Your sentence is unclear; Merlin 1D is undersized for the first stage, yes, that's why they use nine of them.  However, Jim said (and I agree) that the entire upper stage is undersized, in part, because Merlin 1D vac is oversized for the second stage.  It (the stage) has a very high thrust to dry mass ratio.

EDIT: Also, we're losing sight of the thread.  He's asking what's YOUR perfect upper stage(s), not what would the most likely for SpaceX to do.  We have enough of that speculation already.  Of course "perfect" is in the eye of the beholder in this case.  Many would optimize performance, others cost, others manufactuability.

The "perfect" Falcon Heavy EDS eh?  As any good Kerbal Space Program player knows, the answer to almost every issue going beyond Kerbin can be resolved by a nuclear thermal rocket engine.  Just strap on a 800 isp NTR on a 5.2 m wide stage and you'll be launching NASA probes towards Titan in no time.  So long as this thread is about the perfect EDS, I'd say it's hard to get any more perfect than a good 5.2 m NTR-powered EDS.   

Offline MATTBLAK

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #26 on: 11/28/2014 05:32 am »
I don't think Kerbal or rocket Lego is the intent of this thread. But with tongue-in-cheek, I agree wholeheartedly. But politically, nukes flying on a rocket that might - *gasp* - blow up during launch from KSC is literally not going to fly, I fear. Mores the pity. With evolved nuclear thermal; the moons of Jupiter and Saturn could be ours to conquer...
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Offline MP99

Re: Describe a Perfect Earth Departure Stage for FH
« Reply #27 on: 11/28/2014 07:58 am »


Dry mass of second stage should be about 4000 kg.
A two meter stretch should add only 300 kg of dry mass for additional  20000 kg of propellant.
A stretch of second stage seems far easier than a third stage and quite good for performance still using MVac.

http://forum.nasaspaceflight.com/index.php?topic=36045.msg1285819#msg1285819
With the additional propellant, are current 9 merlins enough to lift all the mass?

This is an FH thread, so you meant "27 merlins". <grin>

I believe that FH will always fly with propellant densification (sub-cooling) and 112% merlins.

Since the densified propellant is less than 12% extra mass, this will give a lot of scope to increase the size of FH's upper stage without compromising liftoff T:W. (I'm not convinced it's OK to reduce this from current levels.)

Concurring with previous posters, F9US looks to be well undersized on FH, so this would be a really useful upgrade for higher dVs.

While I'd like to see a Raptor u/s on FH, the T:W is only sensible for LEO launches, IE to supply a methalox depot or similar. So, exactly the opposite of what the thread asked.

Fantasy u/s:- with mini Raptor, but that will stay fantasy.

FH, especially with crossfeed, is already a three stage rocket. Best not to complicate it by adding a fourth.

Cheers, Martin

Offline MP99

Re: Describe a Perfect Earth Departure Stage for FH
« Reply #28 on: 11/28/2014 08:04 am »
Probably a simple pressure fed upper stage using one or two Kestrel engines as this would match Spacex's habit of doing things in house.
Plus fluids commonality with the other two stages.
If we're using the CxP definition of EDS, that it burns from LEO, then Kestrel has neither the thrust, nor the Isp needed for the job.

Perhaps as a Star-48-style kick stage, but that wasn't the question asked.

Cheers, Martin

Offline Zed_Noir

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #29 on: 11/28/2014 08:24 am »
Probably a simple pressure fed upper stage using one or two Kestrel engines as this would match Spacex's habit of doing things in house.
Plus fluids commonality with the other two stages.
If we're using the CxP definition of EDS, that it burns from LEO, then Kestrel has neither the thrust, nor the Isp needed for the job.

Perhaps as a Star-48-style kick stage, but that wasn't the question asked.

Cheers, Martin
The Kestrel engine is a non-starter for enhanced FH upper stage. It got an ablative nozzle with finite burn time, along with new heavier tankage since it will have to be pressurized. Besides the low ISP.

Offline guckyfan

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #30 on: 11/28/2014 08:27 am »
How the Perfect Earth Departure Stage looks like depends on what you want to optimize for. For maximum performance it has to be a hydrogen third stage.

Optimized for cost, as SpaceX goes for, it would have to be a RP-1 or maybe methane extended second stage. Even without increased thrust Merlins it could be at least 35 tons heavier than the present upper stage without compromizing launch T/W, because the payload would be at least that much lower than for LEO.

Offline redliox

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #31 on: 11/28/2014 09:57 am »
I favor the FH for a future launch vehicle.  Regardless of the Russian engines harped about, the Atlas V will inevitably phase out sooner or later.  Getting back to topic, an EDS/Upper Stage is a key item to debate.

Hydrogen seems nearly commonplace for fuel choice, whereas methane is easier to store but not as developed for experienced engines (but getting there and certainly feasible).  Overall it seems a 50/50 choice, but since we're talking SpaceX and Ebon I think cheap, practical, yet advanced come to mind.  So I'd vote with methane, but only slightly.

As for the stage itself, some experience could be drawn from the existing 2nd stage but it would be a new stage done in the SpaceX style.  A newer methalox engine, whether Merlin or Raptor, would be utilized.  This engine would be optimized strictly for spaceflight although the maneuvering engines would be existing hypergolics.   Because of the compatible thermal needs of oxygen and methane the stage would draw on common bulkheads, allowing it to be slightly compact yet carrying a sizeable fuel load.  Like Dragon 2, there would be hull-mounted solar panels to allow for short and intermediate term operations, though I would presume a mission of 3 weeks tops - long enough to fully serve a (short-term) lunar mission or the initial departure of Martian ones.

Reusability would be tricky, since we are talking about a craft that will be screaming in at Apollo/Orion frying speeds...at the least.  Deployable heatshields could be sufficient to aerobrake, so long as the braking occurs over several orbits.  Once settled in LEO, the stage could linger in orbit as a fuel depot or do a final reentry in the same manner as the planned reusable 2nd stage - i.e. with the side opposite the solar panels playing shield.  Based on mass needs, either ditching the stage after use or aerobraking down to LEO would be the options I'd design for as neither requires landing equipment, additional fuel to land, or hull-mounted heatshield tiles.

So, taken together, my 2nd stage must-haves:
1) Methalox primary propulsion/hypergolic auxiliary propulsion
2) Common bulkheads
3) Hull-mounted solar panels (ala Dragon 2)
4) Initial capacity for 3 weeks of space operations
5a) Return to LEO via aerobraking via deployable heatshield (preferred & more feasible)
5b) Return to Earth after aerobraking with additional legs (difficult yet possibly feasible)

All together, this would still be a rocket stage but one that could stretch out the current abilities of upper stages.  It could be adapted with further abilities, but initially meant to move mass around, especially within Cislunar space.  Essentially it would be an OTV but with a specified lifespan and simplified design.  It would be up to the user whether to dump it or stow it for reuse.
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Offline GORDAP

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #32 on: 11/28/2014 12:02 pm »
Well if I was designing the optimal vehicle to go atop an FH stack, it would be essentially a 'Dragon 3'.  This would be a larger diameter, slightly stretched capsule shape (maybe 7 meter diameter and 9 meters tall). 

It would use methane/LOX for main propulsion, using side mounted (8-12?) mini-Raptor derived engines for main 2nd stage propulsion, LAS and landing (the latter 2 as in Dragon 2).  This leaves the bottom of the capsule free of engines and will be all PICA-X TPS.

The very top of the capsule would be similar to the Dragon 2 crew compartment, including the docking port at the top.  Under that would be a good sized payload bay, then under it the methalox tanks.  The payload bay could operate in either a pressurized or non-pressurized manner.  It would have a 'door' on the side that would open for payload to be ejected, then closed before reentry.  There would also be a door between the crew cabin and the payload bay to allow crews access to it when it was used in the pressurized manner.

I think such a vehicle would be extremely useful and versatile.  When used uncrewed, it could deliver large payloads to LEO and GTO, then land propulsively as the Dragon 2, making the entire rocket reusable for the first time in history.  When used with a crew, it could do station resupply (with much increased payload capacity) and do crew rotation at the same time.  If a portion of the payload bay were outfitted with auxiliary tanks, it could serve as a small 'tanker' hauling fuel to orbit.  This same vehicle then (after being refueled in LEO) could land a crew on the Moon with a non-trivial amount of payload.  Alas, I don't think could have enough fuel left for Earth return without some type of refueling on the Moon.  Is there any possibility of Moon ISRU methane and LOX?  I would guess LOX yes, methane no.

I think the same vehicle (aux tanks in portion of payload bay, then vehicle refueled in LEO) could also land a modest payload on Mars, but would not be feasible for a crewed Mars mission, even with ISRU refueling.

Anyway, I think this craft would have a lot of LEO and cis-lunar uses, making it extremely versatile while being completely reusable.
« Last Edit: 11/28/2014 03:27 pm by GORDAP »

Offline Robotbeat

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #33 on: 11/28/2014 02:56 pm »
I don't think Kerbal or rocket Lego is the intent of this thread. But with tongue-in-cheek, I agree wholeheartedly. But politically, nukes flying on a rocket that might - *gasp* - blow up during launch from KSC is literally not going to fly, I fear. Mores the pity. With evolved nuclear thermal; the moons of Jupiter and Saturn could be ours to conquer...
Don't need nuclear thermal for that. Chemical would work fine. For Jupiter and Saturn, nuclear electric would be much better anyway because of the long trip times. Or if you're really brave, aerobraking. :D
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Offline oldAtlas_Eguy

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #34 on: 11/28/2014 03:12 pm »
My optimized EDS/Tanker/Depot stage would be:

1) A Meth/Lox or Hydra/Lox prop IVF system.

2) Using a stainless steel 3.6m diameter balloon tank design which has several positive features:
   a) Lightest weight tank design.
   b) Extremely good thermal properties for cryo propellants.
   c) Very cheap and simple to manufacture.
   d) Road transportable.
   NOTE: The same welder has been used to make Centaur and the original Atlas tanks since the 1950's.  This single welder can produce as many as 100 tanks per year using 1950's welding tech!!! An updated automated welder could produce tanks even cheaper than current Centaur tank construction which uses the same welder that produced tanks in the 1950's!!

3) The stage could have optional solar arrays and thermal shields deployable for use as an extended operation or prop depot storage. Although a main engine for a stage is not usually considered as optional equipment it would be designed so that the main engine for the stage could be left off to increase the prop that can be delivered by the FH to LEO.

4) The 3.6m size is for road transport and for fitting within the faring because of the non-aerodynamic optional equipment.

5) The tank uses common bulkheads and can be sized easily for the mission.

6) Requires new engines for either Meth/Lox or Hydra/Lox operations. This also includes pressure fed RCS [gas boil-off] engines as part of IVF.

7) EDS mission is the smallest tank size because it is an integrated single stack payload cis-lunar or interplanetary mission.

8 ) A tanker is a larger size that fills more of the available volume of the faring but is based on the FH max weight to LEO carrying capability. It would not have sun shields or solar arrays if it is delivering prop to a LEO depot. It may not have a main engine either.  If delivery to a much higher orbit a main engine would be used to perform the orbit changes such as delivery to L1/L2.

9) A depot mission is the largest tank size that fills all of the faring volume with the sun shields and solar arrays.  It is filled with propellant to make up the remaining FH LEO weight capability. For a LEO location it would not have a main engine but for delivery to such as a location as L1/L2 it would have a main engine to perform the orbit changes.

10) The stage dry weight would be ~3-5mt most of which is the engines and other optional hardware.  The tanks are very light.  As an example the entire tank for an Atlas E/F booster weighed 3000lbs or <1.4mt and held >300,000lbs [136mt] of RP-1 and Lox. A max sized tank that could hold 70mt of prop [the depot] would weigh ~ .8mt and the smallest tank holding 35mt of prop [Centaur size] would weigh ~.5mt.
« Last Edit: 11/28/2014 03:15 pm by oldAtlas_Eguy »

Offline AJW

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #35 on: 11/28/2014 04:59 pm »
I don't think Kerbal or rocket Lego is the intent of this thread. But with tongue-in-cheek, I agree wholeheartedly. But politically, nukes flying on a rocket that might - *gasp* - blow up during launch from KSC is literally not going to fly, I fear. Mores the pity. With evolved nuclear thermal; the moons of Jupiter and Saturn could be ours to conquer...

Would these be possible game changers?  Reusable LVs that in a few years could have a track record of successful consecutive launches.  The ability to launch from an ocean going vessel away from land and populated areas.
We are all interested in the future, for that is where you and I are going to spend the rest of our lives.

Offline Vultur

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #36 on: 11/30/2014 08:07 pm »
I don't think Kerbal or rocket Lego is the intent of this thread. But with tongue-in-cheek, I agree wholeheartedly. But politically, nukes flying on a rocket that might - *gasp* - blow up during launch from KSC is literally not going to fly, I fear. Mores the pity. With evolved nuclear thermal; the moons of Jupiter and Saturn could be ours to conquer...

Would these be possible game changers?  Reusable LVs that in a few years could have a track record of successful consecutive launches.  The ability to launch from an ocean going vessel away from land and populated areas.

Probably not, as the fear is irrational anyway just because "it's nuclear/radiation". An unactivated nuclear reactor using uranium (IIRC that's what NERVA used) is not that bad...


I don't have the numbers, but I'm pretty sure a RTG has more Curies of radioactivity than an unactivated NERVA reactor (plutonium-238 half-life = 88 years; uranium-235 half-life = 704 million years).

Offline wdobner

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #37 on: 12/01/2014 02:20 am »
For a perfect EDS on the FH I'd think you'd have to go back to something like the depot proposals surrounding the Falcon Heavy, particularly the initial 7 launch lunar surface mission.

It'd probably go a bit like this: Launch an FH with a stretched and/or widened Falcon 2nd stage which ends up with an IMLEO of around 40mT.  Then launch a tanker equipped with a heat shield atop another FH to top off the EDS from the first launch.  That tanker can then deorbit and in the process test second stage reuse.  If the recovery is successful then that tanker would fly repeatedly to top off the EDS as needed, otherwise a second tanker launches and they have another chance at recovery.  Finally a crewed Dragon launches, attaches itself to the now nearly fully fueled EDS, and off they go to cislunar space (I'm not specifying eyeballs-out burns, or docking vs berthing) or wherever the EDS and Dragon's ELCSS will get them. 

I'd stick with RP1 and LOX for now and hope that a near fully reusable launch infrastructure would allow the mission to be affordable despite the lower specific impulse and large dry mass of the enlarged second stage.  Eventually more advanced engines and fuels can be substituted.  But IMHO they'd be able to embark upon an exploration of cislunar space as soon as they'd flown the Falcon Heavy, the manned Dragon, and had demonstrated an ability to transfer fluids in orbit.

Offline Patchouli

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #38 on: 12/01/2014 03:02 am »
I don't think Kerbal or rocket Lego is the intent of this thread. But with tongue-in-cheek, I agree wholeheartedly. But politically, nukes flying on a rocket that might - *gasp* - blow up during launch from KSC is literally not going to fly, I fear. Mores the pity. With evolved nuclear thermal; the moons of Jupiter and Saturn could be ours to conquer...

If I was going to go nuclear or even solar electric I'd definitely go with a reusable tug as the EDS and a depot though the EDS can be made to act as it's own depot if you can afford the mass penalty.

An ideal combination might be SEP for cargo and NTR or chemical with depots and ISRU for crewed flights.

Such as something like thr LANTR or Nerva shuttles for crew and something like the the Ad Astra OTV for non time critical cargo.
« Last Edit: 12/01/2014 03:13 am by Patchouli »

Offline hkultala

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #39 on: 12/01/2014 06:33 am »
Probably a simple pressure fed upper stage using one or two Kestrel engines as this would match Spacex's habit of doing things in house.
Plus fluids commonality with the other two stages.

Unless a hypothetical 3rd stage has mind-blowingly great Isp, it will never make sense. Stretching the upper stage will always be more mass *and* cost efficient.

So no russian rocket makes sense?

And they are only using hypergolic fuels or kerosine in their upper stages


Merlin engine is too powerful, too heavy for orbital manouvering. And it's isp is only something like 345 seconds.
Hydrogen allows >450s isp, and small upper stage engine can be much lighter than Merlin vac.


FH could lift a 5m dcss + 22.2 ton payload into LEO.

the dcss could then give the payload ~3250 m/s more delta-v. This means earth C3 velocity.

This means 5% bigger payload than F-H:s payload to GTO, to a destination which is 0.7km/s further than GTO.
that 0.7km/s propably costs some 20-25% of payload? F-H payload to C3 being something like 16 tons?

that 16 versus 22 tons is considerable difference in favour of the LH2 upper stage.


But, it would make launch operations much more complex and also make the rocket much more expensive, and the price/kg might get worse.


But, if a larger payload to high energy trajectory would be required, this F-H + LH2 upper stage would still be much cheaper than to use SLS.


I chose DCSS as comparison point instead of centaur because Centaur is a bit too small for these calculations in order to be started exactly in LEO where we know F-H:s capasity, it would have to have 30 ton payload to be 53 tons in LEO but it could not lift that 30 ton payload to even GTO.

But I'd say the optimal upper stage for F-H would be something quite close to centaur or DCSS, depending on destination.
« Last Edit: 12/01/2014 06:40 am by hkultala »

Offline AncientU

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #40 on: 12/01/2014 11:38 pm »
LH2 technology seems to have been considered and selected against by SpaceX.  ISP aside, why take this exit off the laid-out road to MARS?  The FH is a major player in developing the infrastructure for Mars according to Shotwell, and FH will be used to ferry fuel to depots/departing missions, so logically and strategically, fuel should remain methlox.

Remember, 'a perfect Earth departure stage for FH' has to be perfect for SpaceX.
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Offline Elmar Moelzer

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #41 on: 12/02/2014 01:29 pm »
LH2 technology seems to have been considered and selected against by SpaceX.  ISP aside, why take this exit off the laid-out road to MARS?  The FH is a major player in developing the infrastructure for Mars according to Shotwell, and FH will be used to ferry fuel to depots/departing missions, so logically and strategically, fuel should remain methlox.

Remember, 'a perfect Earth departure stage for FH' has to be perfect for SpaceX.
FH is kerolox, not methalox...

Offline RanulfC

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #42 on: 12/02/2014 07:50 pm »
Well, as long as we're describing the "perfect" EDS stage for launch on the Falcon-Heavy we might as well get the exact, right one wouldn't you say? :)

http://en.memory-alpha.org/wiki/Phoenix

Anyone want to top THAT upper-stage performance?

Randy
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Offline AncientU

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #43 on: 12/02/2014 11:08 pm »
LH2 technology seems to have been considered and selected against by SpaceX.  ISP aside, why take this exit off the laid-out road to MARS?  The FH is a major player in developing the infrastructure for Mars according to Shotwell, and FH will be used to ferry fuel to depots/departing missions, so logically and strategically, fuel should remain methlox.

Remember, 'a perfect Earth departure stage for FH' has to be perfect for SpaceX.
FH is kerolox, not methalox...

As is, the upper stage is anything but perfect... A methlox upper stage (instead of the traditional LH2) would be best fit not SpaceX plans for the FH.
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Offline Lars-J

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #44 on: 12/02/2014 11:21 pm »
LH2 technology seems to have been considered and selected against by SpaceX.  ISP aside, why take this exit off the laid-out road to MARS?  The FH is a major player in developing the infrastructure for Mars according to Shotwell, and FH will be used to ferry fuel to depots/departing missions, so logically and strategically, fuel should remain methlox.

Remember, 'a perfect Earth departure stage for FH' has to be perfect for SpaceX.
FH is kerolox, not methalox...

As is, the upper stage is anything but perfect... A methlox upper stage (instead of the traditional LH2) would be best fit not SpaceX plans for the FH.

Anything but perfect?? Geez, hold the exaggerations. It exists already (a big plus) and in the FH it will offer C3 (escape) performance in the similar ballpark of Atlas V and Delta IV-Heavy, the current marker leaders.

Offline TomH

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #45 on: 12/03/2014 12:38 am »
Anything but perfect?? Geez, hold the exaggerations.

It is no exaggeration at all. It is vastly underpowered for the tri-core heavy.

Offline Lars-J

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #46 on: 12/03/2014 12:43 am »
Anything but perfect?? Geez, hold the exaggerations.

It is no exaggeration at all. It is vastly underpowered for the tri-core heavy.

Nope, if anything it is low on propellant. It has plenty of thrust, more than any existing upper stage.

Offline TomH

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #47 on: 12/03/2014 01:24 am »
..it is low on propellant....

Yes. It is mismatched with the heavy core. The US needs to provide more total impulse to match the capacity of the tri-core.

Online wannamoonbase

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #48 on: 12/03/2014 02:13 am »
Ultimate high efficiency as you're already in orbit.

So not fueled by RP1

Reusability not required as it has 'departed'

Ultimate upper stage would be 100% reuse able (fingers crossed for that from SpaceX in the next 10 years)
« Last Edit: 12/03/2014 02:14 am by wannamoonbase »
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline AncientU

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #49 on: 12/03/2014 12:44 pm »
..it is low on propellant....

Yes. It is mismatched with the heavy core. The US needs to provide more total impulse to match the capacity of the tri-core.

Even SpaceX has discussed a high energy upper, so they don't think the second stage is perfect.  Note that this was even before FH was upgraded to v1.1 core and stretched boosters...

So yes, the F9 upper stage is anything but perfect for FH... and I'll predict hat an enhanced version that takes advantage of most of the launcher capability will appear within the first few years of FH operations.
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Offline Lars-J

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #50 on: 12/03/2014 05:46 pm »
..it is low on propellant....

Yes. It is mismatched with the heavy core. The US needs to provide more total impulse to match the capacity of the tri-core.

Even SpaceX has discussed a high energy upper, so they don't think the second stage is perfect.  Note that this was even before FH was upgraded to v1.1 core and stretched boosters...

So yes, the F9 upper stage is anything but perfect for FH... and I'll predict hat an enhanced version that takes advantage of most of the launcher capability will appear within the first few years of FH operations.

The market need isn't there at the moment (FH is overkill for the current market!), and such an upgrade won't happen unless there is a need for it. SpaceX wants a larger launcher, yes, but I think they see FH as an imperfect stop gap until the 'BFR'.

Offline RanulfC

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #51 on: 12/03/2014 06:59 pm »
The market need isn't there at the moment (FH is overkill for the current market!), and such an upgrade won't happen unless there is a need for it. SpaceX wants a larger launcher, yes, but I think they see FH as an imperfect stop gap until the 'BFR'.

Is true :) Specificaly FH is "addressing" the needs of the current market that are going to fall out of the F9 capability due to reuse. The FH is really going to be too much with a higher energy up stage. Useful of course, but not in the sense of the market F9/FH is actually aimed at.

Right now cost rather than performance is the key metric and for that reason using the already existing stage manufacturing and equipment is prefered. Intellectually I fully understand that, however, my sense of "want-more" tends to over-ride that common sense response :)

I personally find it hard to believe that SpaceX is going to dive head-first into Raptor development without trying a "small" methalox motor of some type and my "gut" feeling is they will end up developing a methalox upper stage for the F9 and FH using that motor. Such a stage while being more expensive I admit will put the F9 back into the "middle" of its market payload range even with first stage reuse which can't be anything but "good" for SpaceX. Such a stage on the FH? Out of the ballpark home run territory :)

Randy
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Offline Owlon

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #52 on: 12/03/2014 07:06 pm »
The market need isn't there at the moment (FH is overkill for the current market!), and such an upgrade won't happen unless there is a need for it. SpaceX wants a larger launcher, yes, but I think they see FH as an imperfect stop gap until the 'BFR'.

Is true :) Specificaly FH is "addressing" the needs of the current market that are going to fall out of the F9 capability due to reuse. The FH is really going to be too much with a higher energy up stage. Useful of course, but not in the sense of the market F9/FH is actually aimed at.

Right now cost rather than performance is the key metric and for that reason using the already existing stage manufacturing and equipment is prefered. Intellectually I fully understand that, however, my sense of "want-more" tends to over-ride that common sense response :)

I personally find it hard to believe that SpaceX is going to dive head-first into Raptor development without trying a "small" methalox motor of some type and my "gut" feeling is they will end up developing a methalox upper stage for the F9 and FH using that motor. Such a stage while being more expensive I admit will put the F9 back into the "middle" of its market payload range even with first stage reuse which can't be anything but "good" for SpaceX. Such a stage on the FH? Out of the ballpark home run territory :)

Randy

Except that SpaceX is already diving head-first into Raptor development with component testing at Stennis as of last year and SpaceX management have consistently said Raptor is the only engine being developed.

Offline Waz_Met_Jou

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #53 on: 12/03/2014 07:22 pm »
I disagree with the idea that Falcon Heavy should have a bigger upper stage. A bgger upper stage means a heavier empty mass to drag all the way to GTO/TLI, and while the delta V of the upper stage increases, at some point that of the lower stage decreases faster.

I did some estimates a while ago for GTO payload of Falcon Heavy with different GTO payloads, I attached a graph. Assumed was a fixed 0.94 PMF for the upper stage, with the lower stages all having 385 tons of prop, 20 tons empty. It's not the exact figure that's important, but rather the relation between the payload and the upper stage propellant load.
« Last Edit: 12/03/2014 07:24 pm by Waz_Met_Jou »

Offline Owlon

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #54 on: 12/03/2014 07:33 pm »
I disagree with the idea that Falcon Heavy should have a bigger upper stage. A bgger upper stage means a heavier empty mass to drag all the way to GTO/TLI, and while the delta V of the upper stage increases, at some point that of the lower stage decreases faster.

I did some estimates a while ago for GTO payload of Falcon Heavy with different GTO payloads, I attached a graph. Assumed was a fixed 0.94 PMF for the upper stage, with the lower stages all having 385 tons of prop, 20 tons empty. It's not the exact figure that's important, but rather the relation between the payload and the upper stage propellant load.

I'm not sure exactly how big a difference it would make, but the PMF should actually get better with an increased propellant load, since adding additional length to the tanks will add a relatively small amount of weight to the stage. Certain parts and systems might need beefing up with a large enough propellant increase, but the PMF should increase regardless.

Offline RanulfC

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #55 on: 12/03/2014 09:11 pm »
Except that SpaceX is already diving head-first into Raptor development with component testing at Stennis as of last year and SpaceX management have consistently said Raptor is the only engine being developed.

Well sure, if you're actually going to believe what they actually say :) But where's the fun in that? ;)

They have also mentioned IIRC that Raptor will NOT be a "family" of engines either, which leaves the rather sharp conundrum that the Raptor is far to powerful to be used as a landing engine for the proposed MCT which is ALSO supposed to be methalox powered...

I disagree with the idea that Falcon Heavy should have a bigger upper stage. A bigger upper stage means a heavier empty mass to drag all the way to GTO/TLI, and while the delta V of the upper stage increases, at some point that of the lower stage decreases faster.

I did some estimates a while ago for GTO payload of Falcon Heavy with different GTO payloads, I attached a graph. Assumed was a fixed 0.94 PMF for the upper stage, with the lower stages all having 385 tons of prop, 20 tons empty. It's not the exact figure that's important, but rather the relation between the payload and the upper stage propellant load.

I'm not sure exactly how big a difference it would make, but the PMF should actually get better with an increased propellant load, since adding additional length to the tanks will add a relatively small amount of weight to the stage. Certain parts and systems might need beefing up with a large enough propellant increase, but the PMF should increase regardless.

It should probably be pointed out that main subject of the thread is an "Earth Departure Stage" for the FH not one for GTO/GEO launch :) For that particular criteria a kerolox stage just isn't the "right" one to be using at all and you REALLY want a higher energy propellant and higher ISP engine.

Randy
« Last Edit: 12/03/2014 09:11 pm by RanulfC »
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Offline Lars-J

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Describe a Perfect Earth Departure Stage for FH
« Reply #56 on: 12/04/2014 04:34 am »
It should probably be pointed out that main subject of the thread is an "Earth Departure Stage" for the FH not one for GTO/GEO launch :) For that particular criteria a kerolox stage just isn't the "right" one to be using at all and you REALLY want a higher energy propellant and higher ISP engine.

Randy

Not the right one at all? Sure it is. You use what you have, and if the payload is within the performance of the upper stage (as is), then it is just fine.

You don't get brownie or bonus point for making your TMI burn with a hydrolox stage over a kerolox one.
« Last Edit: 12/04/2014 04:35 am by Lars-J »

Offline llanitedave

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #57 on: 12/04/2014 04:47 am »
What you get is more flexibility.  For instance, note the discussion elsewhere about the proposed Europa Clipper.  Right now it's being presented as a choice between SLS and Atlas V, trading time for payload.  A higher-energy upper stage could possibly put FH into a category that would allow it to compete for high-velocity outer planet missions, OR, heavier GTO missions, OR EOR manned missions to the Moon or beyond.  Yeah, the BFR will be very cool when it happens, but an enhanced FH can do some ground-breaking stuff that would put SpaceX on the Map as a deep-space player well before the BFR comes on line, and can make a good hedge against the teething problems that such an ambitious launcher is likely to have.
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Offline Zed_Noir

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #58 on: 12/04/2014 07:12 am »
The perfect Earth departure stage for SpaceX will be something that is cheap and quick to developed.

Maybe something like a third stage based on a slightly stretched Dragon trunk. With several NEXT ion thrusters powered by high efficiency solar panels for propulsion with hypergolic thrusters for attitude control. It will look similar to the current cargo Dragon trunk with the addition of a third sponson cover for a deployable radio antenna. Tanks of Xenon and hypergolic propellants will be in the stage along with batteries. Payload will be mounted like the Dragon on top of the trunk.

The multiple ion thrusters are for redundancy with only one thruster firing at a time.




Offline MP99

Re: Describe a Perfect Earth Departure Stage for FH
« Reply #59 on: 12/10/2014 08:27 am »


I did some estimates a while ago for GTO payload of Falcon Heavy with different GTO payloads, I attached a graph. Assumed was a fixed 0.94 PMF for the upper stage, with the lower stages all having 385 tons of prop, 20 tons empty. It's not the exact figure that's important, but rather the relation between the payload and the upper stage propellant load.

Surely, that would drop the liftoff T:W below acceptable levels?

Wouldn't you need to offload some prop from core or boosters? Boosters, I think?

Cheers, Martin

Offline guckyfan

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #60 on: 12/10/2014 09:43 am »


I did some estimates a while ago for GTO payload of Falcon Heavy with different GTO payloads, I attached a graph. Assumed was a fixed 0.94 PMF for the upper stage, with the lower stages all having 385 tons of prop, 20 tons empty. It's not the exact figure that's important, but rather the relation between the payload and the upper stage propellant load.

Surely, that would drop the liftoff T:W below acceptable levels?

Wouldn't you need to offload some prop from core or boosters? Boosters, I think?

Cheers, Martin

Not necessarily. For TMI the payload is given as 13t. That's 40t less than to LEO. You can increase second stage fuel by app. 35t and get the same liftoff T/W ratio compared to LEO launchs considering some weight for tank stretch and increased payload.

Offline MP99

Re: Describe a Perfect Earth Departure Stage for FH
« Reply #61 on: 12/10/2014 10:51 am »


I did some estimates a while ago for GTO payload of Falcon Heavy with different GTO payloads, I attached a graph. Assumed was a fixed 0.94 PMF for the upper stage, with the lower stages all having 385 tons of prop, 20 tons empty. It's not the exact figure that's important, but rather the relation between the payload and the upper stage propellant load.

Surely, that would drop the liftoff T:W below acceptable levels?

Wouldn't you need to offload some prop from core or boosters? Boosters, I think?

Cheers, Martin

Not necessarily. For TMI the payload is given as 13t. That's 40t less than to LEO. You can increase second stage fuel by app. 35t and get the same liftoff T/W ratio compared to LEO launchs considering some weight for tank stretch and increased payload.
He was adding 110t of prop.

Cheers, Martin

Offline Moe Grills

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #62 on: 12/19/2014 09:44 pm »
How about no chemical TLI nor TMI stages?
VASIMR, instead?
And simply launch a VASIMR into LEO to rendezvous with a 53 tonne payload sent up by another FH?
Too simple an idea, huh?

Offline Lars-J

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #63 on: 12/19/2014 10:52 pm »

How about no chemical TLI nor TMI stages?
VASIMR, instead?
And simply launch a VASIMR into LEO to rendezvous with a 53 tonne payload sent up by another FH?
Too simple an idea, huh?

Only if VASIMR is simple. Or practical. Or cost effective. Or any of the above.

Offline Ben the Space Brit

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Re: Describe a Perfect Earth Departure Stage for FH
« Reply #64 on: 12/20/2014 08:47 pm »
My ideal is something like either BE-3 (that's hteir Hydrolox engine, isn't it?) or even MB-60 (why was Elon in Japan recenlty?) on a PLF-diameter stage.

However, that isn't the whole of it. I'd like for there to be two distinct forms - Type one is just a light-at-sep standard upper stage. The other will have Dragon-type solar arrays to power active ZBO tank cooling, a full Draco RCS system and, optionally, a DragonEye rendezvous system. It would thus also function as a chemical-propellent tug for cis-Lunar missions.

You then can launch this baby into LEO and have it idle for six weeks or so until you launch the main mission payload with another FH. It then rendezvouses with the 'passive' payload and either heads off to the destination or awaits a BEO-rigged Dragon-2 with the mission crew.

I'd also like for the system to have a buddy/buddy propellent transfer system. At a guess, with an LH2-fuelled upper stage, FH's IMLEO would jump to around 60t. Assuming 20t for a BEO Dragon-2, that would potentially mean around 10t of excess LH2 and LOX, which could be transferred over to the EDS, thus either increasing its' through-TOI performance or ensuring tank top-off after a long LEO idle awaiting the mission crew.
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