Author Topic: Propellant Depots - General Discussion  (Read 398350 times)

Offline DanClemmensen

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Re: Propellant Depots - General Discussion
« Reply #1100 on: 01/02/2022 11:42 pm »
Wouldn't a LOX/LH2 depot fundamentally also be a water depot, compatible with water plasma thruster based services? This, plus a potential capability to manufacture LOX/LH2 from water deliveries (which are a reasonably dense cargo, thus easy rideshare fodder), provides a secondary delivery market that is amenable to adhoc delivery?

Yeah. Propellant production from pre-placed water was a feature of Lockheed's Mars Base Camp architecture, no reason you couldn't use some of that water for other purposes. With any water-derived hydrolox production, you do have the problem of excess oxygen having to be dumped (since engines always burn fuel-rich), but accounting for the storability and density of water you might still come out ahead on a mass-to-orbit basis. And directly using water for propellant would skip that whole problem.
For crewed spacecraft depot customers, that surplus oxygen is a valuable asset. Otherwise, the depot or the customer spacecraft can use the extra oxygen for cold gas thrusters for station keeping and angular momentum dumping.

No, not a good idea.  Requires additional systems on the receiver spacecraft. 

The depot can use it itself for those purposes.
I am speculating here: The crewed craft would not have a separate receiver for the "extra" oxygen. Instead, it would receive more LOX than it needs for propellant use, and it would have a system to tap its LOX tank for crew atmosphere or for its cold gas thrusters. And you are right, it may in fact not be a good idea, it's just speculation based on the point made in the prior post.

Offline Jim

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Re: Propellant Depots - General Discussion
« Reply #1101 on: 01/02/2022 11:56 pm »
No.  Crew vehicles don’t have cold gas thrusters, much less oxygen ones.  It would require separate tanks.

Also, LOX can not be used in cold gas thrusters, not high enough pressure.
« Last Edit: 01/02/2022 11:59 pm by Jim »

Offline TrevorMonty

Re: Propellant Depots - General Discussion
« Reply #1102 on: 01/03/2022 12:45 am »
There are pros and cons for shipping and converting water in orbit.
Pros
More compact tanks on tanker, makes for lighter tanker which is big plus for lunar landers taking fuel to LO.
No issues with boiloff so trip times can be months.
Access to 24/7 solar power. Which is plus for lunar fuel.
Lot cheaper to deliver equipment to lunar orbit than lunar surface.

Cons
Depot is now complex processing plant.
Excess Oxygen, but this can be used with hydrogen or methane for earth or moon.
In case of LEO that 24/7 solar power becomes more like 12/7.

With lunar fuel going need to create some fuel on surface for landers to get into orbit.  Fuel BLLO and descents to surface can be extracted from water in orbit.

For LEO depots iy may work out cheaper to deliver fuel instead of water from earth.

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Offline mandrewa

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Re: Propellant Depots - General Discussion
« Reply #1103 on: 01/03/2022 02:23 am »
There are pros and cons for shipping and converting water in orbit.
Pros
More compact tanks on tanker, makes for lighter tanker which is big plus for lunar landers taking fuel to LO.
No issues with boiloff so trip times can be months.
Access to 24/7 solar power. Which is plus for lunar fuel.
Lot cheaper to deliver equipment to lunar orbit than lunar surface.

Another advantage of water is that every launch to the depot can go up full, or close to it.  Many payloads don't use the full capacity of the rocket.  Water is very compact.  If you have different size water tanks that would mount underneath the main payload, then every launch can go up full.

Offline Asteroza

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Re: Propellant Depots - General Discussion
« Reply #1104 on: 01/05/2022 04:18 am »
There are pros and cons for shipping and converting water in orbit.
Pros
More compact tanks on tanker, makes for lighter tanker which is big plus for lunar landers taking fuel to LO.
No issues with boiloff so trip times can be months.
Access to 24/7 solar power. Which is plus for lunar fuel.
Lot cheaper to deliver equipment to lunar orbit than lunar surface.

Another advantage of water is that every launch to the depot can go up full, or close to it.  Many payloads don't use the full capacity of the rocket.  Water is very compact.  If you have different size water tanks that would mount underneath the main payload, then every launch can go up full.

This is the core part of a question I had rolling around in the back of my mind; Why isn't Dragon using surplus upmass to fill water bladders in the trunk for delivery to ISS? Why is this potential market being ignored/avoided currently? I feel like the answers to those questions has relevance to the overall propellant depot marketplace.

Offline Redclaws

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Re: Propellant Depots - General Discussion
« Reply #1105 on: 01/05/2022 04:38 am »
What would the ISS do with the water?  And where would they store it?

Offline TrevorMonty

Re: Propellant Depots - General Discussion
« Reply #1106 on: 01/05/2022 10:19 am »
Hydrolox is really only useful to a handful of upper stages which currently don't support refuelling. Only time they'd need a top is for BLEO which are far few between.

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Offline brickmack

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Re: Propellant Depots - General Discussion
« Reply #1107 on: 01/05/2022 09:55 pm »
This is the core part of a question I had rolling around in the back of my mind; Why isn't Dragon using surplus upmass to fill water bladders in the trunk for delivery to ISS? Why is this potential market being ignored/avoided currently? I feel like the answers to those questions has relevance to the overall propellant depot marketplace.

I think Momentus was interested in doing this. Send small payloads (like the ones already deployed from JEM-AL and Bishop) up in cargo vehicles, use whatever capacity is left over for water to fuel their tugs, use the station's crew and robotics to integrate everything and mate it to a tug that goes off and brings the payloads to more useful orbits.

Really would be nice if it works out, solves a lot of different problems for multiple parties. But Momentus' future looks pretty questionable right now. And their propulsion tech is expected to produce a ton of radio interference right? Might not be able to use it in proximity to the station, so operations might have to be one-way (release new tugs and payloads, but no refueling and reuse), kinda hard to justify then

Either way, until someone actually does this, theres no point and no capability for bringing up substantial amounts of water to the station

Offline su27k

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Re: Propellant Depots - General Discussion
« Reply #1108 on: 08/29/2022 02:27 pm »
https://twitter.com/rocketrepreneur/status/1563372802484211712

Quote
For those who were asking, I wrote a blog post about the @AIAA/@AerospaceCorp Cislunar Depot Workshop I participated in this last week, including key takeaways, and a copy of my presentation.
When @mmealling finishes uploading his presentation, I'll update the post with a link.



My Independent Perspectives on Cislunar Depots


https://twitter.com/mmealling/status/1563758299920699393

Quote
Here are my slightly modified slides. I used animations that don't translate well so they needed to be updated. The last slide includes a summary of the Commodities Reserve.

An Investor’s Perspective on Cislunar Depots

Offline su27k

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Re: Propellant Depots - General Discussion
« Reply #1109 on: 09/03/2022 03:54 am »
Fill ’er up

Quote from: aerospaceamerica.aiaa.org
The push to expand Earth’s economy into space has prompted NASA to pump millions of dollars into the old idea of establishing propellant depots in Earth orbit for satellites or passenger transports and cargo tugs headed for deep space. Jon Kelvey looks at the reasons for the renewed interest — and the hurdles ahead.

Offline su27k

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Re: Propellant Depots - General Discussion
« Reply #1110 on: 09/03/2022 05:30 am »
Fill ’er up

Quote from: aerospaceamerica.aiaa.org
The push to expand Earth’s economy into space has prompted NASA to pump millions of dollars into the old idea of establishing propellant depots in Earth orbit for satellites or passenger transports and cargo tugs headed for deep space. Jon Kelvey looks at the reasons for the renewed interest — and the hurdles ahead.

https://twitter.com/davehuntsman/status/1565905499828133890

Quote
Reasonable summary article vis a vis in-space fuel depots. Only 1 tweak: sayings ‘depots’ was ‘verboten’ 12yrs ago inside NASA an understatement; have direct knowledge of 2 good NASA depot advocates- at 2 different Centers 100s miles apart-receiving firing orders on same day.



Even easy to remember date: the firing orders, dated end of Nov giving obligatory 30-day warnings of firing- noted that termination of the two civil servants would be effective “commencing Dec 25, 2011” - for both. The two felt a message was being sent. One had 35+yrs in NASA.

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