Author Topic: Reusable Falcon for propellant depot.  (Read 29184 times)

Offline jongoff

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Re: Reusable Falcon for propellant depot.
« Reply #60 on: 11/14/2013 04:54 pm »
I have read them. Propellant transfer is a non-issue.

While I agree that propellant transfer is almost certainly not a showstopper, calling it a non-issue seems naive. I don't think it would cost much to get the experience we need to make this work, but the work still needs to get done.

~Jon

Offline TrevorMonty

Re: Reusable Falcon for propellant depot.
« Reply #61 on: 11/14/2013 10:42 pm »
One plus of fuel depots, would be to allow LV manufacturers to prove their new LV (eg FH, future FX) with an inexpensive cash on delivery payload.

Offline ncb1397

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Re: Reusable Falcon for propellant depot.
« Reply #62 on: 11/15/2013 02:02 am »
A liquid Argon depot stored at 86K in MEO makes more sense than Methane/LOX for reusable space tugs.

Benefits:
-order of magnitude more ISP
-extremely safe operation/storage(chemically inactive)
-one fuel type/ one fuel tank(the RTG/solar panels will last the life of the tug. RTG could be robotically refueled or replaced to extend life but may not be required)
-Argon is abundant in the solar system and chemically uncombined. Mars atmosphere is 1.6% Argon. Earth atmosphere is 1% Argon. Argon was detected on Titan recently although I am not sure that molar fraction is known.
-higher boiling point than Hydrogen.

Human "cargo" can just use a direct trajectory to mars with a interplanetary speed reentry. Human cargo though is a small fraction of the manifest for a mars mission. The real problem with a mars HSF mission is all the equipment they need on the surface to get back or set up shop. Electric propulsion(VASIMR is "off the shelf ") makes the most sense for the earth orbit to mars orbit transfer phase for anything that doesn't need life support. So, anyway, back to the argon tug concept. Presumeably they will refill in both mars orbit and earth orbit with the MAV refilling the mars portion from insitu mining of the martion atmosphere. If the MAV is reusable, presumeably it could drop off fuel and pick up some downlift from a tug(the tug is there anyway for refueling) all in one go.

Offline KelvinZero

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Re: Reusable Falcon for propellant depot.
« Reply #63 on: 11/15/2013 05:54 am »
A liquid Argon depot stored at 86K in MEO makes more sense than Methane/LOX for reusable space tugs.
Hi. Just to clarify, in the OP I was referring to a F9R for servicing a depot. The F9R could be carrying any propellant type. My point was really that servicing a depot is a perfect mission for an F9R, imo. When you mention humans taking a direct trajectory, this would still benefit from a LEO depot of methane/LOX or hydrogen/LOX, whatever the departure stage uses.

Offline go4mars

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Re: Reusable Falcon for propellant depot.
« Reply #64 on: 04/20/2014 06:07 am »
Yes.  All the docking could be done autonomously, perhaps using flux pinning for attachment/transfer points.
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Offline MP99

Re: Reusable Falcon for propellant depot.
« Reply #65 on: 04/20/2014 06:43 am »
How do they transfer fuel in zero G?. The only solution I had was for both vehicles to be accelerating (<0.1G) so fuel moves to bottom of tank for pumping.

Something like 0.0001 G, IIRC.

Cheers, Martin

Offline Ben the Space Brit

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Re: Reusable Falcon for propellant depot.
« Reply #66 on: 04/20/2014 02:36 pm »
I've long felt that the reusable F9r upper stage with either stretched tanks and no other payload or cryo tanks in place of its payload could be used as a tanker to support depots.
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Offline AncientU

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Re: Reusable Falcon for propellant depot.
« Reply #67 on: 04/20/2014 06:36 pm »
I've long felt that the reusable F9r upper stage with either stretched tanks and no other payload or cryo tanks in place of its payload could be used as a tanker to support depots.
Agree.  You'd want it to be reusable, of course.  The second stages themselves wouldn't be well enough insulated, in my opinion, to achieve zero boil-off needed for long term, efficient storage.

The depot itself could be launched within a standard or stretched fairing to protect the extra insulation, solar panels, docking/fuel transfer equipment, whatever other hardware is needed.  (it might be able to be flown as second stage, but I doubt it could be as well insulated or equipped)  The standard SpaceX fairing has about 200m^3 of internal volume, so could carry an empty depot with tankage to store 100-200mT of fuel, depending on the mix of LOX/liquid methane; a stretched fairing (diameter around 6m, length 20m +) could triple that.  Recall that the ACES concept was for 41mT and 73mT versions --ref below -- plus a 121mT version using one of each.
http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf
« Last Edit: 04/20/2014 06:37 pm by AncientU »
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Offline Lar

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Re: Reusable Falcon for propellant depot.
« Reply #68 on: 04/20/2014 07:43 pm »
Recall that the ACES concept was for 41mT and 73mT versions --ref below -- plus a 121mT version using one of each.
http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf

I wish ULA would just up and build that. I know why they haven't but I can still wish it anyway. Maybe BLM will bless it someday. It would help them stay relevant.
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Offline ArbitraryConstant

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Re: Reusable Falcon for propellant depot.
« Reply #69 on: 04/20/2014 09:09 pm »
How do they transfer fuel in zero G?. The only solution I had was for both vehicles to be accelerating (<0.1G) so fuel moves to bottom of tank for pumping.

Something like 0.0001 G, IIRC.

Cheers, Martin
Use a ballasted tether. Extend it outwards in the orbital plane. The depot will experience acceleration due to tidal forces without requiring reaction mass.

Offline StealerofSuns

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Re: Reusable Falcon for propellant depot.
« Reply #70 on: 04/21/2014 02:31 pm »
Why wouldn't some sort of pump work? Why would acceleration be necessary?
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Offline SpunkyEnigma

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Re: Reusable Falcon for propellant depot.
« Reply #71 on: 04/21/2014 04:03 pm »
You have to have acceleration to settle the fuel in the intakes for the pumps.

Why wouldn't some sort of pump work? Why would acceleration be necessary?

Offline Lar

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Re: Reusable Falcon for propellant depot.
« Reply #72 on: 04/21/2014 04:23 pm »
Why wouldn't some sort of pump work? Why would acceleration be necessary?
You have to have acceleration to settle the fuel in the intakes for the pumps.

To expand on that, pumps rely on something, however gentle, pushing material into their intakes. If nothing is pushing material in, they will cavitate instead.  It could be gravity (or acceleration) or it could be pressure (via a bladder/membrane. pressure by itself won't necessarily force the desired material into the intake, you could end up drawing the pressurant gas in)

So settling thrusters are used on stages to get material oriented right. Something similar likely would be needed here unless bladders/membranes were used.
« Last Edit: 04/21/2014 04:25 pm by Lar »
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"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline sugmullun

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Re: Reusable Falcon for propellant depot.
« Reply #73 on: 04/21/2014 04:37 pm »
Pure speculation on my part:
  If time isn't a constraint then high flow rates (like in feeding an engine) isn't either.
Why would pumps be needed at all. Some sort of acceleration to place the fuel at a port and then just use pressurized gas to push it through. It seems that it'd always be possible to generate at least a little higher pressure in the supplying tank than the receiving.
edited for spelling
« Last Edit: 04/21/2014 04:42 pm by sugmullun »

Offline muomega0

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Re: Reusable Falcon for propellant depot.
« Reply #74 on: 04/21/2014 05:09 pm »
Recall that the ACES concept was for 41mT and 73mT versions --ref below -- plus a 121mT version using one of each.
http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf

I wish ULA would just up and build that. I know why they haven't but I can still wish it anyway. Maybe BLM will bless it someday. It would help them stay relevant.

It would appear that 35.7B for 60 additional flights, if this is correct is worth more than building a depot.

Max Faget said that "we really need to get behind a really sensible first stage that's completely reusable and piggyback off that event" so finally Musk revisited the Titan I with only one type of RP-1 engine and possibly a reusable lower stage with legs to cut costs to the government (taxpayer).

Perhaps the BEO upper stage/depot/lander (ACES or its variant) will the future centerpiece of LM/Boeing/ULA.

Offline Proponent

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Re: Reusable Falcon for propellant depot.
« Reply #75 on: 04/21/2014 05:32 pm »
How do they transfer fuel in zero G?. The only solution I had was for both vehicles to be accelerating (<0.1G) so fuel moves to bottom of tank for pumping.

Something like 0.0001 G, IIRC.

Cheers, Martin
Use a ballasted tether. Extend it outwards in the orbital plane. The depot will experience acceleration due to tidal forces without requiring reaction mass.

Settling with small accelerations has been demonstrated many times and tethers have both been proposed, as has magnetic settling (see p. 4 of the first attachment).  Another possibility is rotation.  Stable, solid-body rotation with residual Centaur propellants was demonstrated on Atlas V AV-017 (second attachment).
« Last Edit: 04/21/2014 05:33 pm by Proponent »

Online Llian Rhydderch

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Re: Reusable Falcon for propellant depot.
« Reply #76 on: 04/21/2014 11:50 pm »

So, for example, 3 F9Rs can put 9 tankers in orbit within a week. (or for that matter, within a month)


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