Quote from: DanClemmensen on 01/02/2022 09:46 pmQuote from: brickmack on 01/02/2022 07:07 pmQuote from: Asteroza on 10/10/2021 10:52 pmWouldn'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.
Quote from: brickmack on 01/02/2022 07:07 pmQuote from: Asteroza on 10/10/2021 10:52 pmWouldn'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.
Quote from: Asteroza on 10/10/2021 10:52 pmWouldn'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.
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?
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.
Quote from: TrevorMonty on 01/03/2022 12:45 amThere 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.
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
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
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.
Fill ’er upQuote from: aerospaceamerica.aiaa.orgThe 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.
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.
Interesting comment by Orbit Fab’s Daniel Faber at #GSSF22: ability to refuel will result a shift from electric to chemical propulsion; can trade efficiency for getting you into revenue service the fastest. (Also, price of xenon is now “terrifying,” he says.)
QuoteInteresting comment by Orbit Fab’s Daniel Faber at #GSSF22: ability to refuel will result a shift from electric to chemical propulsion; can trade efficiency for getting you into revenue service the fastest. (Also, price of xenon is now “terrifying,” he says.)
It may be cheaper in the long run to make lox from lunar soil and launch to lunar orbit or to L1 or L2. Lox has more mass or weight so launching from earth would be more expensive in the long run. Launching liquid methane or even liquid hydrogen from earth would be cheaper due to their mass or weight getting to orbit or to the moon. Water would have more mass due to the oxygen content if launched from earth. Water may also have a tendency to freeze in space causing expansion that could lead to leaks. Methane is widely handled in liquid form already on earth, unlike hydrogen which tends to leak more due to the small atom. Pound for pound methane or hydrogen would be cheaper to launch than water. Hydrogen is also not a good long term storage unless you have refrigeration equipment at the depot due to faster boil off. I think setting up lox manufacturing on the moon should be a priority for any type of moon base to cut down on transportation costs to launch to a depot. Then only methane would have to be brought from earth.
Quote from: spacenut on 10/21/2022 06:49 pmIt may be cheaper in the long run to make lox from lunar soil and launch to lunar orbit or to L1 or L2. Lox has more mass or weight so launching from earth would be more expensive in the long run. Launching liquid methane or even liquid hydrogen from earth would be cheaper due to their mass or weight getting to orbit or to the moon. Water would have more mass due to the oxygen content if launched from earth. Water may also have a tendency to freeze in space causing expansion that could lead to leaks. Methane is widely handled in liquid form already on earth, unlike hydrogen which tends to leak more due to the small atom. Pound for pound methane or hydrogen would be cheaper to launch than water. Hydrogen is also not a good long term storage unless you have refrigeration equipment at the depot due to faster boil off. I think setting up lox manufacturing on the moon should be a priority for any type of moon base to cut down on transportation costs to launch to a depot. Then only methane would have to be brought from earth. Disagree for the short to medium term, maybe even the long term. It will be cheaper to bring propellants from Earth then setting up ISRU LOX production on the Moon and the logistics of delivering it to Earth orbit.Propellants is cheap. Off Earth facilities and cislunar logistics are expensive.
