Author Topic: Zubrin's New Falcon Heavy Architecture - Moon Direct  (Read 64063 times)

Offline Hauerg

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #40 on: 03/18/2018 08:45 am »
And in 10 years I doubt there will still be a FH.

Offline 192

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #41 on: 03/18/2018 09:13 am »
* Develop and build a Lunar Excursion Vehicle: the LEV. Cabin the size of the LM. 2 tons.
* Have on the LEV a hydrolox stage with enough fuel to do TEI and then EOI back to LEO. All told, 6 km/s.
* The above requires a mass ratio of 3.7, resulting in a 8 ton vehicle.
* Put all that in a cargo module, to be landed by the previously developed cargo lander.

Delta-V is Ascent+TEI+TCM+EOI+1% margin = (1890+1169+2+3185)*1.01 = 6308.5 m/s. RL-10C-2 ve = 4535.6 m/s. Mass ratio = exp(6308.5/4535.6) = 4.018. An 8 t vehicle would then have a dry mass of 1.99 t, including the cabin! Not going to work. Assuming a mc = 2000 kg cabin, one me = 301 kg engine, two crew at mh = 125 kg each and mr = 100 kg of samples, a stage dry mass model of ms = 0.46718*mp^{0.848}, I get ms = 1353 kg and mp = 12085 kg. Total mass is mc+2*mh+mr+me+ms+mp = 2000+2*125+100+301+1353+12085 = 16,089 kg, which is 4.1 t greater than the 12 t that can be landed!

Attached is a little program that I used for working out the stage mass. You can also use it for other hydrolox stages! Just enter the delta-V, exhaust speed, cargo mass, engine mass and number of engines.

The 2 t mass figure is for the whole Apollo ascent stage, not just a crew cabin. So includes mass of engines and tanks you have counted separately. Probably saves at least half a ton, plus further reductions in propellant and stage mass. Also, the RL-10 could lift about 70 t on the moon, which is overkill, so could probably get away with much lighter engine.

Offline A_M_Swallow

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #42 on: 03/18/2018 12:19 pm »
* Develop and build a Lunar Excursion Vehicle: the LEV. Cabin the size of the LM. 2 tons.
* Have on the LEV a hydrolox stage with enough fuel to do TEI and then EOI back to LEO. All told, 6 km/s.
* The above requires a mass ratio of 3.7, resulting in a 8 ton vehicle.
* Put all that in a cargo module, to be landed by the previously developed cargo lander.

Delta-V is Ascent+TEI+TCM+EOI+1% margin = (1890+1169+2+3185)*1.01 = 6308.5 m/s. RL-10C-2 ve = 4535.6 m/s. Mass ratio = exp(6308.5/4535.6) = 4.018. An 8 t vehicle would then have a dry mass of 1.99 t, including the cabin! Not going to work. Assuming a mc = 2000 kg cabin, one me = 301 kg engine, two crew at mh = 125 kg each and mr = 100 kg of samples, a stage dry mass model of ms = 0.46718*mp^{0.848}, I get ms = 1353 kg and mp = 12085 kg. Total mass is mc+2*mh+mr+me+ms+mp = 2000+2*125+100+301+1353+12085 = 16,089 kg, which is 4.1 t greater than the 12 t that can be landed!

Attached is a little program that I used for working out the stage mass. You can also use it for other hydrolox stages! Just enter the delta-V, exhaust speed, cargo mass, engine mass and number of engines.

The 2 t mass figure is for the whole Apollo ascent stage, not just a crew cabin. So includes mass of engines and tanks you have counted separately. Probably saves at least half a ton, plus further reductions in propellant and stage mass. Also, the RL-10 could lift about 70 t on the moon, which is overkill, so could probably get away with much lighter engine.

According to Wikipedia RL-10 engines produce between 64.7 to 110 kN.

64.7kN * 12t / 70t = 11.1 kN

That is the equivalent of three Machete engines from Masten Space which burn the monopropellent MXP-351.

Offline sevenperforce

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #43 on: 03/18/2018 01:34 pm »
Falcon Heavy definitively lowers the costs and increases the mass that can be sent per launch, and if anyone gets serious about this the ULA ACES hardware could be a good platform to use.

I've always been fond of the ACES-derived horizontal landers - they seem like an elegant solution, as opposed to the "Apollo on steroids" Altair type solutions NASA was planning to pursue.
Yes, the DTAL always seemed like an elegant solution to me as well. Thrust vector stability would have been an issue in the Apollo era but we are far past that. And if you play your cards right, you can have your single docking port available for coupling to a rover.

So the idea is to haul TEI and EOI propellant down to the lunar surface, leave behind an expendable lander, and then leave an expendable LEV in LEO because we're afraid of orbital refueling? How could it possibly make sense to pay such a high price for an EOI burn on the way back to LEO without a commitment to reuse the LEV?

This is just Apollo Direct Ascent, except with the theory that hauling around EOI propellant (and doing an extra ".5" launch) is preferable to hauling around a heatshield. I'm not convinced it is.
Unless the mass of a heat shield balloons by ~300% or the isp of your engines increases by ~200%, then taking a heat shield to LLO will always require less propellant than taking EOI propellant to LLO. Let alone to the lunar surface.

Just simple math.

To me a LEV that would go back and forth from the ISS should be something considered.
Has anyone looked into the dry mass requirements of a completely-reusable heat shield capable of doing aerocapture in a single pass? That's really the only efficient way of getting from LLO to the ISS. Keeping in mind that the heat shield needs to protect the entire vehicle; you can't jettison anything before atmospheric entry. Should be somewhat less massy than a full Earth entry shield.

Plus, on the one Falcon 9 in-flight failure, the LAS would have saved the crew.

Would it? The LAS is essentially a rocket stage with components similar in function to what failed on the two Falcon 9 failures. It could fall apart just as easily as what it is attached to. Same manufacturer. In the two Falcon 9 failures, the stage that failed wasn't even active at the time.
LAS is not safe. It is a failsafe: if something else fails, it keeps you safe. No one expects an LAS for your LAS.

But we do tend to expect some sort of LAS. Cough, STS.

Offline sevenperforce

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #44 on: 03/18/2018 01:41 pm »
BFR may be too big for the Dragon 2 life support system, unless 5-10 copies are used.
Seems like something Musk might like. They are all about multiple redundant copies of stuff. E.g., Falcon 9.

Offline sevenperforce

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #45 on: 03/18/2018 01:46 pm »
If a reusable lunar surface access vehicle was proposed, what's the ideal propellant/engine?

I was thinking that electrically-turbopumped hypergolics have some advantages. Electric pumps are pretty much infallible, and the added dry mass should be more than compensated for by lighter tanks and higher isp compared to a pressure-fed solution. Hypergolics for storability and ignition assurance.

Offline robert_d

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #46 on: 03/18/2018 01:49 pm »


Last 20 missions would be STS-115(Sept. 2006) through STS-135 (July 2011). All were successful.

You are correct. I was wrong. Edited original comment above.

Online tater

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #47 on: 03/18/2018 02:07 pm »
It seems like the crew section of the plan (FH with crew lander, plus F9 with crew) might be an issue.
FH can deliver however many tons to the Moon (meaning stage 2 makes a TLI burn), but this architecture requires that FH make such a TLI burn for the crew lander, right? This means that the crew Dragon needs to rendezvous with the FH upper stage during whatever its max coast period is. Sounds like a logistical issue. One #waywardboat and there's a big problem.

Offline sevenperforce

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #48 on: 03/18/2018 02:34 pm »
It seems like the crew section of the plan (FH with crew lander, plus F9 with crew) might be an issue.
FH can deliver however many tons to the Moon (meaning stage 2 makes a TLI burn), but this architecture requires that FH make such a TLI burn for the crew lander, right? This means that the crew Dragon needs to rendezvous with the FH upper stage during whatever its max coast period is. Sounds like a logistical issue. One #waywardboat and there's a big problem.
You would want to send up the crew Dragon first, since it has longer loiter time. An extra day or two on orbit isn't going to break your crew. Then you send up the FH+lander to do its thing, and Dragon 2 moves on its own to rendezvous.

If you end up having to scrub FH repeatedly, then you can always abort the mission, and D2 comes back under its own power.

Ideally, however, you set up a FH on 39A and a F9 on 40, so as soon as F9 completes orbital insertion, FH is cleared for launch. Not super-good for inclination matching, but a bit of a dogleg on the F9 launch never hurt anybody. At the most you'd launch FH the following day.

Is Pad 40 going to be set up with a crew access bridge, or only 39A? Pad 40 can't support FH at this time, I don't think.

Online tater

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #49 on: 03/18/2018 02:52 pm »
Currently crew is only 39A.

So short of some serious infrastructure changes, the launches would serially be at the same pad.

Of course it seems like the best way to pitch something like this would be to have the crew vehicle be CST-100 (includes more players).

Offline jeng_eo

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #50 on: 03/18/2018 02:52 pm »
It seems like the crew section of the plan (FH with crew lander, plus F9 with crew) might be an issue.
FH can deliver however many tons to the Moon (meaning stage 2 makes a TLI burn), but this architecture requires that FH make such a TLI burn for the crew lander, right? This means that the crew Dragon needs to rendezvous with the FH upper stage during whatever its max coast period is. Sounds like a logistical issue. One #waywardboat and there's a big problem.

IIRC Dr. Zubrin suggested that the FH inserts the LEV into a GTO/GEO-like high orbit. Dragon will rendezvous with the LEV there. Dragon stays and the (now dV-wise small) TLI burn is done by the LEV.

Offline sevenperforce

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #51 on: 03/18/2018 03:13 pm »
Currently crew is only 39A.

So short of some serious infrastructure changes, the launches would serially be at the same pad.
Not impossible, I suppose. And a 24-hour turnaround is better for inclination-matching, anyway. Though, does the 39A hangar have space for four cores at a time?

Quote
Of course it seems like the best way to pitch something like this would be to have the crew vehicle be CST-100 (includes more players).
This would be true if CST100 had ANY advantage over Dragon 2. It's way heavier. Does it have more onboard dV?

Offline sevenperforce

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #52 on: 03/18/2018 03:15 pm »
It seems like the crew section of the plan (FH with crew lander, plus F9 with crew) might be an issue.
FH can deliver however many tons to the Moon (meaning stage 2 makes a TLI burn), but this architecture requires that FH make such a TLI burn for the crew lander, right? This means that the crew Dragon needs to rendezvous with the FH upper stage during whatever its max coast period is. Sounds like a logistical issue. One #waywardboat and there's a big problem.

IIRC Dr. Zubrin suggested that the FH inserts the LEV into a GTO/GEO-like high orbit. Dragon will rendezvous with the LEV there. Dragon stays and the (now dV-wise small) TLI burn is done by the LEV.
That certainly fixes the loiter problem, but it would require the D2 launch to be an expendable F9. F9 RTLS/ASDS doesn't have the push to get a 10-tonne payload into GTO.

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #53 on: 03/18/2018 03:31 pm »
That also likely makes timing even more critical I would assume, since the crew vehicle then needs to rendezvous with an eccentric orbit, and one that is specifically oriented for efficient lunar orbit injection. If you missed what is (necessarily?) an instantaneous launch window, when's the next one, next month, or in a few weeks?

Offline sevenperforce

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #54 on: 03/18/2018 03:33 pm »
That also likely makes timing even more critical I would assume, since the crew vehicle then needs to rendezvous with an eccentric orbit, and one that is specifically oriented for efficient lunar orbit injection. If you missed what is (necessarily?) an instantaneous launch window, when's the next one, next month, or in a few weeks?
Makes it pretty much unworkable, really.

Online envy887

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #55 on: 03/18/2018 04:11 pm »
Currently crew is only 39A.

So short of some serious infrastructure changes, the launches would serially be at the same pad.
Not impossible, I suppose. And a 24-hour turnaround is better for inclination-matching, anyway. Though, does the 39A hangar have space for four cores at a time?

Quote
Of course it seems like the best way to pitch something like this would be to have the crew vehicle be CST-100 (includes more players).
This would be true if CST100 had ANY advantage over Dragon 2. It's way heavier. Does it have more onboard dV?
It has a crew capable launch pad already set up.

Offline jeng_eo

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #56 on: 03/18/2018 04:29 pm »
Quote
IIRC Dr. Zubrin suggested that the FH inserts the LEV into a GTO/GEO-like high orbit. Dragon will rendezvous with the LEV there. Dragon stays and the (now dV-wise small) TLI burn is done by the LEV.


I just double-checked:

* around minute 46:30 of the interview he talks about the Cargo-Lander going from GTO to TLI (delivering the habitation module and power/isru).

* at minute 21:45 he says that the LEV will be brought to the surface of the moon as the payload of another
cargo lander (but not mentioning expilictly from which orbit)

* minute 22:50 :  the cargo lander is able to land 12 tons and the LEV has a mass of 8 tons (including LOX/LH-stage and crew cabin)

* minute 23:40: "leaving the dragon behind in LEO"

So I was clearly wrong with my LEV -> GTO statement. Sorry for this.  :-[
« Last Edit: 03/18/2018 04:44 pm by jeng_eo »

Online tater

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #57 on: 03/18/2018 04:31 pm »
This would be true if CST100 had ANY advantage over Dragon 2. It's way heavier. Does it have more onboard dV?

I was thinking politically, not technically :) .

Offline butters

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #58 on: 03/18/2018 06:06 pm »
Delta-V is Ascent+TEI+TCM+EOI+1% margin = (1890+1169+2+3185)*1.01 = 6308.5 m/s. RL-10C-2 ve = 4535.6 m/s. Mass ratio = exp(6308.5/4535.6) = 4.018. An 8 t vehicle would then have a dry mass of 1.99 t, including the cabin! Not going to work. Assuming a mc = 2000 kg cabin, one me = 301 kg engine, two crew at mh = 125 kg each and mr = 100 kg of samples, a stage dry mass model of ms = 0.46718*mp^{0.848}, I get ms = 1353 kg and mp = 12085 kg. Total mass is mc+2*mh+mr+me+ms+mp = 2000+2*125+100+301+1353+12085 = 16,089 kg, which is 4.1 t greater than the 12 t that can be landed!

Yes. We're talking about doing Apollo Direct Ascent with a launch vehicle that has under one third the TLI performance of the Nova-class Saturn C-8, and we're making what seems like a poor design trade by hauling about EOI propellant rather than a reentry heatshield. It makes sense that if you work this kind of architecture backwards to the mass of the crew cabin, we get something that's probably not sufficient for a two-person crew.

I think the best way to make this work is to do direct ascent / direct reentry with Dragon using Earth orbit rendezvous. The descent/lander stage would launch on an expendable FH. If the the ascent stage can't also fit on that FH, then that's an additional F9 launch.

Offline FinalFrontier

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Re: Zubrin's New Falcon Heavy Architecture - Moon Direct
« Reply #59 on: 03/18/2018 06:07 pm »
It is not a decent architecture. Why is this proposal a thing?
Why isn't he proposing COTS/CRS/CCDEV for BEO? Something that would be far easier to sell to Congress (there is already discussion of using commercial launchers for pieces of the Lunar Platform thing)?

Elephant in the room is being ignored once again, money being wasted on a giant NASA rocket and spacecraft that could be better served elsewhere. Good luck paying for lunar mission elements while simultaneously funding that nonsense.

I am somewhat upset that Dr. Zubrin and others in similar positions don't want to talk about this issue. It is only going to get worse and more pronounced as time goes by and the commercial sector continues to mature. They don't want to talk about it to the point they are proposing whole new mission architectures and totally ignoring it.

I think Zubrin is proposing this as a replacement for DSG. He didn't propose concepts like COTS probably because he wants to show something concrete for politicians to visualize (i.e. boots on the Moon in x years). Besides, the administration's FY19 budget request already has proposal for public private partnership on lunar lander, it's called Advanced Cislunar and Surface Capabilities (ACSC), but it doesn't have a lot of funding ($116.5M for FY19, increases to $320.3M in FY23). If the administration can be convinced to move DSG's funding into lander development, then there should be enough to do something like Zubrin suggested (it probably won't launch on FH though). All of these can be done without tackling the harder problem of cancelling SLS/Orion, at least I think that's his plan.
Great example of what I meant by forest through the trees.

You should not be moving DSG's funding into anything. You should be moving SLS's funding into DSG ACSC, Lunar orbital outpost, Mars surface infrastructure, and whatever else you think you may need.

Then you bid out for the launcher, and better yet if you want to go a step further you bid for who can build each of these elements  as well instead of just giving jobs program cost plus contracts to Boeing like hand outs and calling that 'commercial' or "a nasa built thing."

We are talking about horse trading the money supply for things that we need instead of shutting down the thing we don't need. We do not need SLS. We probably do not need Orion, but it's so far along you might as well use it for something.

We do need the space lobby so replace SLS with contracting for things that the other commercial players might not be able to do very easily. This goes to DSG, Mars surface systems, maybe a larger DSG or more than one DSG to ease transit times and hardship between the earth and Mars. There are many roles here NASA should be filling wrt the moon mars and BEO hardware in general that they aren't doing, that need to be done. There is no guarantee BFS will work and even if it does it sure would be alot quicker and easier to establish a presence on Mars if NASA was helping and already had hardware there.

If we are really going to get serious about any of this stuff the interests need to work together instead of competing against each other, it makes no sense to waste the BEO budget on a useless launcher that can't compete on cost with any of the commercial alternatives.

This cannot be overstated.
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