Propellant depot strategy & tactics pow-wow

[Calphor]

Av-Week just put up an article on a ULA proposal for on-orbit propellant depots:

http://www.aviationweek.com/aw/generic/story.jsp?id=news/ULA08109.xml&headline=ULA%20Proposes%20On-Orbit%20Gas%20Stations%20for%20Space%20Exploration&channel=space

[agman25]

ULA Proposes On-Orbit Gas Stations for Space Exploration

http://www.aviationweek.com/aw/generic/story.jsp?id=news/ULA08109.xml&headline=ULA%20Proposes%20On-Orbit%20Gas%20Stations%20for%20Space%20Exploration&channel=space

Also Delta IV gets the centaur and The Air Force Research Laboratory is planning a hydrocarbon booster demonstration in 2018.

[simon-th]

Av-Week just put up an article on a ULA proposal for on-orbit propellant depots:

http://www.aviationweek.com/aw/generic/story.jsp?id=news/ULA08109.xml&headline=ULA%20Proposes%20On-Orbit%20Gas%20Stations%20for%20Space%20Exploration&channel=space

I think they are spot on. This IS the way forward.

I also like their near-term thinking:

Depots could be derived from the existing Centaur and planned advanced cryogenic upper stages for the EELV. The advanced stage would be designed to minimize heat transfer and propellant boil-off for extended operations in space. The depot additionally would be able to deploy a conical sunshield to fully encapsulate the tanks. “We can build a near-term depot without resorting to extreme, zero boil-off designs,” says Kutter.

I just am not sure going for a LEO depot is the way forward and they - at least according to the article - don't seem to think a L1/2 depot is what should be developed.

[adamsmith]

Av-Week just put up an article on a ULA proposal for on-orbit propellant depots:

http://www.aviationweek.com/aw/generic/story.jsp?id=news/ULA08109.xml&headline=ULA%20Proposes%20On-Orbit%20Gas%20Stations%20for%20Space%20Exploration&channel=space

I think they are spot on. This IS the way forward.

I also like their near-term thinking:

Depots could be derived from the existing Centaur and planned advanced cryogenic upper stages for the EELV. The advanced stage would be designed to minimize heat transfer and propellant boil-off for extended operations in space. The depot additionally would be able to deploy a conical sunshield to fully encapsulate the tanks. “We can build a near-term depot without resorting to extreme, zero boil-off designs,” says Kutter.

I just am not sure going for a LEO depot is the way forward and they - at least according to the article - don't seem to think a L1/2 depot is what should be developed.

Any depot is a good depot.  The concept to make self evident is that it is possible to separate the earth launch system from the space mission any type of depot will help that.

Stanley

[jongoff]

Av-Week just put up an article on a ULA proposal for on-orbit propellant depots:

http://www.aviationweek.com/aw/generic/story.jsp?id=news/ULA08109.xml&headline=ULA%20Proposes%20On-Orbit%20Gas%20Stations%20for%20Space%20Exploration&channel=space

I think they are spot on. This IS the way forward.

I also like their near-term thinking:

Depots could be derived from the existing Centaur and planned advanced cryogenic upper stages for the EELV. The advanced stage would be designed to minimize heat transfer and propellant boil-off for extended operations in space. The depot additionally would be able to deploy a conical sunshield to fully encapsulate the tanks. “We can build a near-term depot without resorting to extreme, zero boil-off designs,” says Kutter.

I just am not sure going for a LEO depot is the way forward and they - at least according to the article - don't seem to think a L1/2 depot is what should be developed.

Actually, they're interested in both LEO and L1/2 depots.  With depots both in LEO and in L1/L2, you can do missions more capable than the ESAS architectures using commercially available launchers, with no need for heavy lift.  There should be several interesting papers out at the SPACE 2009 conference next month.  Patience grasshopper.  :-)

~Jon

[mmeijeri]

There's a new set of slides about propellant depots on the ULA website.

[simon-th]

There's a new set of slides about propellant depots on the ULA website.

Thanks for the link. Great pitch by ULA, of course the Committee will recommend an HLV with a minimum capacity of 75mt to LEO class, so the 2-launch lunar scenario with EELVs they outline with propellant depots is somewhat moot.

What really is interesting to analyze right now is a 1-launch lunar architecture involving LEO depots.

Let's assume a generic 75mt to LEO HLV with the following payload characteristics (assuming the current baseline scenario + assuming an Orion+Altair+EDS stack fits into a payload bay in length):
Orion:
- 10.5mt dry mass
- 9.5mt propellant (hypergolics)
Altair:
- ascent module dry mass 5.5mt
- ascent module propellant 5mt (hypergolics)
- descent module dry mass 9mt (including pot. cargo)
- descent module propellant 26mt (LH2: 4mt /LOX: 22mt)
EDS:
- 17mt dry mass
- 103mt propellant w/ 10% margin (LH2: 15mt / LOX: 88mt)

That would mean for a hypergolics depot a single launch would be out of the question.

However with a LOX depot, the launch mass can be around 75mt with no LOX in either the EDS or Altair. Problem would be - Orion would need to do the circularization burn and rendezvous maneuvers with the depot (functioning basically as a tug to carry the whole stack to the depot). At 80mt to LEO, some LOX in the EDS could be carried along to allow the EDS to the circularization burn.

The question here is, whether 1 LOX depot and probably 10 EELV or other commercial launches to bring about 110mt of LOX to the LEO depot are cheaper than another HLV launch.

[MP99]

Another question...

For H2/O2 in a passively cooled depot, is the boiloff rate affected by the propellant load? IE is the boiloff rate the same regardless of whether the depot is 1% full or 99% full? First principles suggest there is an incoming heat load, therefore a fixed rate of boiloff is required to keep the depot cold.

cheers, Martin

[jongoff]

Another question...

For H2/O2 in a passively cooled depot, is the boiloff rate affected by the propellant load? IE is the boiloff rate the same regardless of whether the depot is 1% full or 99% full? First principles suggest there is an incoming heat load, therefore a fixed rate of boiloff is required to keep the depot cold.

I remember getting an answer about this at one point, but I can't remember the details.  I'll have to get back with you later.  Send me an email to remind me.

~Jon

[Namechange User]

Another question...

For H2/O2 in a passively cooled depot, is the boiloff rate affected by the propellant load? IE is the boiloff rate the same regardless of whether the depot is 1% full or 99% full? First principles suggest there is an incoming heat load, therefore a fixed rate of boiloff is required to keep the depot cold.

cheers, Martin

First define passively cooled....

[MP99]

Another question...

For H2/O2 in a passively cooled depot, is the boiloff rate affected by the propellant load? IE is the boiloff rate the same regardless of whether the depot is 1% full or 99% full? First principles suggest there is an incoming heat load, therefore a fixed rate of boiloff is required to keep the depot cold.

cheers, Martin

First define passively cooled....

In Jongoff's response to my previous question he said "If your depot is passively cooled" - I just copied that phrase from his response!


I must admit, though, I thought this phrase meant it was cooled by evaporation and didn't realise it was complicated. (But that's why I asked the question).

So what are my options?

cheers, Martin

[Namechange User]

Another question...

For H2/O2 in a passively cooled depot, is the boiloff rate affected by the propellant load? IE is the boiloff rate the same regardless of whether the depot is 1% full or 99% full? First principles suggest there is an incoming heat load, therefore a fixed rate of boiloff is required to keep the depot cold.

cheers, Martin

First define passively cooled....

In Jongoff's response to my previous question he said "If your depot is passively cooled" - I just copied that phrase from his response!


I must admit, though, I thought this phrase meant it was cooled by evaporation and didn't realise it was complicated. (But that's why I asked the question).

So what are my options?

cheers, Martin

When it comes to cryo tanks there are multiple ways to passively cool it.  For example, using the boil-off you do have and using it in a vapor cooled shield to protect from thermal radiation.  I would consider that passive since it is putting to good use something that will happen anyway. 

Was just wanting to get everyone on the same page to best answer the question. 

[Norm Hartnett]

This is somewhat off topic but does anyone know why the ULA slides include the Scorpius Launch Vehicles? (center bottom page 3)

Seems a rather odd choice.

[grdja]

One question I haven't seen asked.

If propellant depots are actually developed. Could they have commercial role? I mean, could ULA and/or Energia and Krunichev finally build and launch tugs that stay in space and transfer comsats and weatherbirds to GEO and other non LEO orbits?

I suppose answer to that would be is (or can it be made that) keeping a tanked off propellant depot in space cheaper than using larger payload to LEO rocket and a 3rd stage for each non LEO launch.

[Namechange User]

One question I haven't seen asked.

If propellant depots are actually developed. Could they have commercial role? I mean, could ULA and/or Energia and Krunichev finally build and launch tugs that stay in space and transfer comsats and weatherbirds to GEO and other non LEO orbits?

Certainly.  And hopefully that will be/would be the goal.

[A_M_Swallow]

One question I haven't seen asked.

If propellant depots are actually developed. Could they have commercial role? I mean, could ULA and/or Energia and Krunichev finally build and launch tugs that stay in space and transfer comsats and weatherbirds to GEO and other non LEO orbits?

I suppose answer to that would be is (or can it be made that) keeping a tanked off propellant depot in space cheaper than using larger payload to LEO rocket and a 3rd stage for each non LEO launch.

The other advantage is that bigger satellites can be sent to GEO.

1) EELV (or rival) to LEO, refuel Centaur at depot, Centaur boosts satellite to GSO.

2) LV to LEO, solar electric tug collects satellite and say argon from depot,
    tug flies to GEO and releases satellite, then tug returns to LEO.

[grdja]

Doh as H. Simpson would say. I'm a space nut, I know its possible. I was asking:

In a realistic scenario where NASA goes Deep Space or Lunar Global and uses the LEO fuel depots, will there be real incentive for commercial operators to include depots in their operational plans (and by that I also mean that commercial operators share costs of developing and deploying and tanking the depots) or will business as usual be more economic option.

Edit. For example a amateur guesswork on commercial problems with depot. Electric/Ion is assumed not likely for close term. So for example a nice little .ppt spaceship, a Parom, has to fuel up, grab a sat in LEO, get it into GTO (depending on architecture sat has a engine to do circularization and plane transfer or tug has to go almost all the way to GEO with it), than our brave tug has to reverse all its orbital changes and return to LEO for another refueling.
So in such (amateurish and inefficient I know...) approach, is there a economic case for a fuel depot?

[Patchouli]

Another advantage of a propellant depot is it can conceivably turn a VTOL RLV like DCY into a lunar transportation system at least for time critical cargo such as crew.
Stuff that doesn't need a fast trip probably could be transported for lower cost with a SEP tug.
Refuel it in LEO then fly it to the moon.

Here's a good early example of what a fuel depot can do for an RLV.
http://www.astronautix.com/craft/proelena.htm

The vehicle doesn't have to be as big as rombus smaller actually might be better.

[TOG]

Another question...

For H2/O2 in a passively cooled depot, is the boiloff rate affected by the propellant load? IE is the boiloff rate the same regardless of whether the depot is 1% full or 99% full? First principles suggest there is an incoming heat load, therefore a fixed rate of boiloff is required to keep the depot cold.

cheers, Martin

First define passively cooled....

In Jongoff's response to my previous question he said "If your depot is passively cooled" - I just copied that phrase from his response!


I must admit, though, I thought this phrase meant it was cooled by evaporation and didn't realise it was complicated. (But that's why I asked the question).

So what are my options?

cheers, Martin

When it comes to cryo tanks there are multiple ways to passively cool it.  For example, using the boil-off you do have and using it in a vapor cooled shield to protect from thermal radiation.  I would consider that passive since it is putting to good use something that will happen anyway. 

Was just wanting to get everyone on the same page to best answer the question. 

IIRC - If  you keep the propellant in a closed system (where the vapor is contained instead of released, and you have an exterior shield to prevent tank wall heating, (based on standard chemistry) won't our propellant reach an equilibrium point where the act of evaporation will keep the remainder of the propellant cool?  And at the same time, with the increase in pressure due to the "vapor active" fluids, won't there be a degree of condensation internal to the tank?

The big IFs here is the method we are using to prevent additional heat from being applied to the system and whether we can contain the vaporous propellant (to keep a "closed" system) until we start to transfer the propellant to the active spacecraft.

TOG

[jimvela]

IIRC - If  you keep the propellant in a closed system (where the vapor is contained instead of released, and you have an exterior shield to prevent tank wall heating, (based on standard chemistry) won't our propellant reach an equilibrium point where the act of evaporation will keep the remainder of the propellant cool?  And at the same time, with the increase in pressure due to the "vapor active" fluids, won't there be a degree of condensation internal to the tank?

I don't see the need.  There are commercial providers with cryo experience (think instrument cooling- hint, hint) whom could build a closed loop system to return vapor to a tank in liquid form.  Once you get that, you get infinite loiter as long as your depot stays powered.

The big IFs here is the method we are using to prevent additional heat from being applied to the system and whether we can contain the vaporous propellant (to keep a "closed" system) until we start to transfer the propellant to the active spacecraft.

Again, no need. put the solar arrays on the sun side of the tankage, and the reprocessing facilities and radiators in the shadow.  The arrays (and possibly additional MLI or other insulation) help keep the tankage cool, and supply power for the system to cool propellant and  reprocess boiloff.