That's a very good point gbaikie, load up your depot with say 6 shipments each of 25 tonnes O2, last shipment 25 tonnes H2 gives you 175 tonnes propellant in LEO, no need for a really big rocket.
The boil off problem is why hydrogen will in practice be restricted to launch vehicles. In space chemical rockets will probably burn a storable fuel like methane.
In terms of costs and ability such an EML-2 space station could function in LEO or in Mars orbit.
Quote from: gbaikie on 07/11/2014 09:28 pmIn terms of costs and ability such an EML-2 space station could function in LEO or in Mars orbit.GBaikie, I assume you know this statement is false from front to back correct? The EML-2 space station FUNCTION is a "gateway" at the highest point in the Cis-Lunar gravity well so as to facilitate missions beyond Cis-Lunar space as well as supporting missions to the Moon itself. It can not perform this "misson" in either Martian or LEO orbits.Randy
Quote from: RonM on 07/11/2014 05:17 amQuote from: DLR on 07/10/2014 09:06 pmISRU is one of the main reasons why a lunar outpost is worth far more than an EML-2 station. On the long run, it may be cheaper as well, since it could potentially be self-sufficient in water, oxygen and propellant. An EML-2 station is a waste of taxpayer money.Unless that EML-2 station is a fuel depot for interplanetary spacecraft. The fuel can come from the lunar outpost.It seems a EML-2 station and/or lunar outpost could be waste of tax payer money.But I suppose, one should first ask what is the EML-2 station and/or lunar outpost. And how much would it cost the taxpayer.
Quote from: DLR on 07/10/2014 09:06 pmISRU is one of the main reasons why a lunar outpost is worth far more than an EML-2 station. On the long run, it may be cheaper as well, since it could potentially be self-sufficient in water, oxygen and propellant. An EML-2 station is a waste of taxpayer money.Unless that EML-2 station is a fuel depot for interplanetary spacecraft. The fuel can come from the lunar outpost.
ISRU is one of the main reasons why a lunar outpost is worth far more than an EML-2 station. On the long run, it may be cheaper as well, since it could potentially be self-sufficient in water, oxygen and propellant. An EML-2 station is a waste of taxpayer money.
Quote from: gbaikie on 07/11/2014 08:07 amQuote from: RonM on 07/11/2014 05:17 amQuote from: DLR on 07/10/2014 09:06 pmISRU is one of the main reasons why a lunar outpost is worth far more than an EML-2 station. On the long run, it may be cheaper as well, since it could potentially be self-sufficient in water, oxygen and propellant. An EML-2 station is a waste of taxpayer money.Unless that EML-2 station is a fuel depot for interplanetary spacecraft. The fuel can come from the lunar outpost.It seems a EML-2 station and/or lunar outpost could be waste of tax payer money.But I suppose, one should first ask what is the EML-2 station and/or lunar outpost. And how much would it cost the taxpayer.How did you determine that the EML2 station would be a waste of tax payer money? Yes, the concern is that the gateway could start to consume the budget much like everything else.The L2 Gateway should be thought as the re-useable voyager, the DSH that is not stuck in one location--multiple destinations.In the most optimistic program plan, the DSH is sent to L2 for one year with a few crew to demonstrate that both crew and hardware can survive the round trip to Mars. The DSH is then reused for subsequent trips for satellite assembly and repair, ARM, and emergency lunar egress. Inspirational Mars skipped this step.
Quote from: muomega0 on 07/14/2014 08:56 pmQuote from: gbaikie on 07/11/2014 08:07 amQuote from: RonM on 07/11/2014 05:17 amQuote from: DLR on 07/10/2014 09:06 pmISRU is one of the main reasons why a lunar outpost is worth far more than an EML-2 station. On the long run, it may be cheaper as well, since it could potentially be self-sufficient in water, oxygen and propellant. An EML-2 station is a waste of taxpayer money.Unless that EML-2 station is a fuel depot for interplanetary spacecraft. The fuel can come from the lunar outpost.It seems a EML-2 station and/or lunar outpost could be waste of tax payer money.But I suppose, one should first ask what is the EML-2 station and/or lunar outpost. And how much would it cost the taxpayer.How did you determine that the EML2 station would be a waste of tax payer money? Yes, the concern is that the gateway could start to consume the budget much like everything else.The L2 Gateway should be thought as the re-useable voyager, the DSH that is not stuck in one location--multiple destinations.In the most optimistic program plan, the DSH is sent to L2 for one year with a few crew to demonstrate that both crew and hardware can survive the round trip to Mars. The DSH is then reused for subsequent trips for satellite assembly and repair, ARM, and emergency lunar egress. Inspirational Mars skipped this step. there are some disadvantages if the L2 depot and gateway are combined.I have not determined that the EML2 station would be a waste of tax payer money. But it certainly could be.
Quote from: gbaikie on 07/11/2014 08:07 amQuote from: RonM on 07/11/2014 05:17 amQuote from: DLR on 07/10/2014 09:06 pmISRU is one of the main reasons why a lunar outpost is worth far more than an EML-2 station. On the long run, it may be cheaper as well, since it could potentially be self-sufficient in water, oxygen and propellant. An EML-2 station is a waste of taxpayer money.Unless that EML-2 station is a fuel depot for interplanetary spacecraft. The fuel can come from the lunar outpost.It seems a EML-2 station and/or lunar outpost could be waste of tax payer money.But I suppose, one should first ask what is the EML-2 station and/or lunar outpost. And how much would it cost the taxpayer.How did you determine that the EML2 station would be a waste of tax payer money? Yes, the concern is that the gateway could start to consume the budget much like everything else.The L2 Gateway should be thought as the re-useable voyager, the DSH that is not stuck in one location--multiple destinations.In the most optimistic program plan, the DSH is sent to L2 for one year with a few crew to demonstrate that both crew and hardware can survive the round trip to Mars. The DSH is then reused for subsequent trips for satellite assembly and repair, ARM, and emergency lunar egress. Inspirational Mars skipped this step. there are some disadvantages if the L2 depot and gateway are combined.
I would say as general note, and something learn able from ISS, is a need to determine how to have space stations have operational lifetime equal or greater than structures we have on Earth. Or we need get to point of having space stations that have lifetimes of say, 50 years or more. Being forced into a routine of having 20 year [or less] lifetime disposal space stations, in general, makes the space environment less usable or realistic in terms a potential of opening the space frontier.Or living on Earth would not work, if our structures only lasted 20 years. One could have grass huts last only a few years [which require couple days to make], but the Empire State and Golden State bridge would not be built if they were to only last 20 years. One can't construct something which requires years [or costs billions] and then not have them last for very long.So in terms of any other space stations, a primary focus should on preserving and learning how to have the ISS operate with a greater lifetime. Even if we ignore the very bad PR of crashing ISS into Earth, there is value in keeping ISS flying in order to actually learn how to live in space.And another aspect of space stations is being able to operate them at low yearly cost. Perhaps if we end up, de-orbiting ISS, one might sell idea of EML2 station on basis learning from mistakes of ISS, in terms improving future space stations so they last longer and have less daily maintenance needed. Though not sure in wake of a crashed ISS, that Congress would have much confidence in such promises.
One could also ship Hydrogen ice and arrive at destination with liquid Hydrogen.
Quote from: gbaikie on 07/13/2014 07:22 pmOne could also ship Hydrogen ice and arrive at destination with liquid Hydrogen.I really enjoy this forum.
Quote from: Hernalt on 07/17/2014 03:46 pmQuote from: gbaikie on 07/13/2014 07:22 pmOne could also ship Hydrogen ice and arrive at destination with liquid Hydrogen.I really enjoy this forum.This is something I dont understand but there is apparently a simple answer to. What does limit the sorts of temperatures you can reduce your tank to? How long would it take to heat up again?
Quote from: TrevorMonty on 08/29/2014 11:36 amThanks Sdsd for the links. I've read the DTAL paper before, its the basis of Masten XEUS lander, but haven't see the paper on fuel depots.ULA has some good ideas, but most of the hardware seems to be expendable, which is great if you are manufacturer of ACES stages. With large fully reusable LV eg Space BFR which maybe delivering 100mt+ of fuel at a time, these fuel depots start making sense. The tanker that delivers fuel to L2 also needs to be fully reusable, ie returns to LEO using aerocapture. If the fuel costs are lower enough it may end up being cheaper to reuse lander and deliver lower mass to lunar surface at a time.I do like the idea of using the surplus fuel in lander to provide power and life support for extended stays. One of the biggest issues of extended stays is power to survive a lunar night.I think getting fuel to the region of the Moon and reusing that hardware will be the first challenge we solve. Next we have to figure out how to move the reusable vehicles to Earth LEO so that they can be refueled in LEO (i.e. aerocapture, the static drag device that's been mentioned, etc.). After that the challenge is to figure out how to make a reusable Earth-LEO bulk transportation system - which even if it's water will likely be pretty hard (i.e. costly to develop and prove out).So I would concede that we'll have to live with disposable systems for quite a while, but decreases in launch costs and standardizing the construction of the fuel transports could make it affordable enough to implement.
Thanks Sdsd for the links. I've read the DTAL paper before, its the basis of Masten XEUS lander, but haven't see the paper on fuel depots.ULA has some good ideas, but most of the hardware seems to be expendable, which is great if you are manufacturer of ACES stages. With large fully reusable LV eg Space BFR which maybe delivering 100mt+ of fuel at a time, these fuel depots start making sense. The tanker that delivers fuel to L2 also needs to be fully reusable, ie returns to LEO using aerocapture. If the fuel costs are lower enough it may end up being cheaper to reuse lander and deliver lower mass to lunar surface at a time.I do like the idea of using the surplus fuel in lander to provide power and life support for extended stays. One of the biggest issues of extended stays is power to survive a lunar night.
The SLS is currently officially rated as having a 70 metric ton payload. I do not know if any of the recent changes will increase the payload to 100 tonne.
Any near term (10yr) lunar base is most likely to be a commercial venture eg Bigelow. To be viable its going to have rely on commercial LVs.