- Depots at L1/2 make more sense than depots in LEO - you don't have to store all the EDS propellant
Another disadvantage is that L1 rules out participation in propellant launches by small launch vehicles
Quote - Depots at L1/2 make more sense than depots in LEO - you don't have to store all the EDS propellantI don't think this is true. For one you couldn't refuel your upper stage in LEO, so you would need a bigger launcher to launch a fully fueled EDS.
Now I'm actually in favour of doing it this way in the short run (since it gets cryogenic depots off the critical path), but in the slightly longer run it is a disadvantage.
Another disadvantage is that L1 rules out participation in propellant launches by small launch vehicles, which negates most of the benefit of depots.
- you could have a dedicated depot for LH2/LOX or only LOX or at the beginning only hypergolics for lunar missions and a dedicated depot for argon for interplanetary missions using VASIMIR (or derivatives)
So how fast would a L1/2 depot loose LH2 to boil off?Could I fill the depot and use the fuel a year later, or would it be empty in a couple months?I am just attempting to get a feel for what the practical usefulness and limitations are for fuel depots.
With respect for Hypergolics vs Cryogenic fuels, I was under the impression that LH2 was overwhelmingly superior than Hypergolics for long range missions (like Mars).
What would the typical mission mass penalty be for using Hypergolics over LH2?
Any idea how long of a storage/mission length is required to make Hypergolics better than Cryogenics?
I am not entirely sure I understand what you are getting at. A L1/2 depot (with a small manned space station - permanently manned or just temporarily manned) would be supplied by commercial launch providers. Of course only rockets with a launch capacity of several tons to EML-1 or EML-2 make sense to use for this task. This would rule out small rockets such as Taurus II. I'd say you are in the 10-35mt to LEO launcher field with about 4 to 15mt payload capacity to EML-1/2 for depot supplying duties.
Entirely ok, if you ask me.
And the big benefit is, your depot doesn't have to store 1000mt fuel or more, it just has to hold in the range of 250-350mt of fuel for the same purpose than a LEO depot (+ you get all the added advantages above from a mission architecture perspective that a LEO depot doesn't provide you with - reusing in-deep space flight hardware - VASIMIR stages, Orion only to EML-1 or EML-2 and not all the way to Mars etc.).
How so? I'd say it's the other way around. For NEO and circumlunar precursor missions, you really don't need any fuel depots. But once you go for lunar surface missions and interplanetary missions all those nice advantages that I listed pop up for a EML-1/2 depot.
I addressed that above. I very much disagree. Small rockets (in the 5-10mt to LEO range) are inefficient in kg to cost anyway. Launching 20 rockets with a 25mt to LEO and 12mt to EML-1/2 capacity gets you a much better price per kg to LEO/EML-1/2 than 50 rockets with a 10mt to LEO launcher. That's because your variable cost start to lead your total expense line when you get into the 15-20 launches per year range.
Yes, high energy orbits offer many advantages. The thing is, you still need to get your crew capsule to such a higher energy orbit. If you can top up an existing upper stage in LEO, you need a much smaller launcher to get there.
I understand where you getting at in your posts. I just think we can't have both LEO depots and L1/2 depots from a budget perspective and rather opt for one that is geared towards lunar flights and interplenatary flights
Just a note on that point. Orion is a given. So we are stuck with a 20mt spacecraft that - once we have killed off the Ares I - can go back to a 6-crew capacity. The committee will opt for an HLV in any event which at least a 75mt to LEO and about 30mt to TLI capacity (or more if you develop J-246). That being said, any down-the line (of course not simple precursor missions) beyond-LEO mission would use Orion with some kind of MPLM/Hab or Lunar Lander (dry) (all depending on the mission) to the L1/2 space station architecture. Maxing out your HLV with Orion and that additional payload is enough for any conceivable beyond-LEO mission WITHOUT refueling your EDS in LEO.
Seek to create markets, Martijn, not mandates from government.
Am I truly less "statist" than you? That would be ironic.
With respect for Hypergolics vs Cryogenic fuels, I was under the impression that LH2 was overwhelmingly superior than Hypergolics for long range missions (like Mars). cloud? (unmanned of course)