{snip}If depots were available in 2015 how else might they be used?
Quote from: CitabriaFlyer on 06/28/2011 11:44 pm{snip}If depots were available in 2015 how else might they be used? Bigger satellites to GEO. The EELV is launched fully loaded and empties its tanks achieving LEO and docking. The propellant depot refills the tanks permitting the upper stage to fly the satellite to GEO.
Personally, I feel that the depot concept doesn't gain much from launching the propellant from earth except in the gain in economies of scale for the launch vehicles. You're still burning significant quantities of fuel to get a smaller quantity of fuel prepositioned.To me, the best business case for depots involves bringing fuel from sources that extract a much smaller 'launch penalty'. Unless the depot can provide fuel for less than the cost of sizing up the launch vehicle for the mission, it won't be able to present a viable business case. After-all, which is cheaper? 4 Falcon 9 launches or 1 Falcon Heavy?
Once upon a time gasoline was sold in pint jars through drug stores...Then the automobile came along.Demand creates new ideas creates desire creates opportunity creates new demand.Fuel depots are one of this type of 'enabler' technologies. Right now, everyone is happy buying their gas by the pint at the drugstore because they don't know how a service station is going to work. Once fuel depots are established, we'll probably wonder how we ever got along without them, but until we get one up and tested, we won't even know if the concept is viable.Personally, I feel that the depot concept doesn't gain much from launching the propellant from earth except in the gain in economies of scale for the launch vehicles. You're still burning significant quantities of fuel to get a smaller quantity of fuel prepositioned.To me, the best business case for depots involves bringing fuel from sources that extract a much smaller 'launch penalty'. Unless the depot can provide fuel for less than the cost of sizing up the launch vehicle for the mission, it won't be able to present a viable business case. After-all, which is cheaper? 4 Falcon 9 launches or 1 Falcon Heavy?
However it will most definitely be cheaper than NASA's HLV.
Quote from: DarkenedOne on 06/30/2011 06:57 pmHowever it will most definitely be cheaper than NASA's HLV.Emphasis on "NASA" as USA's recent commercial Shuttle bid has shown. If one were to take the "NASA" out of the HLV and let a commercial company operate it, there is actually profit potential there, especially when used in conjunction with (not just propellant) orbiting depots.
Fuel depots on the other hand are essentially satellites. Once you put them up there they last for decades at extremely low maintenance cost. The costs of fuel depots is incremental.
What about supporting large robotic expeditions to energetic places like Mercury?Or would it just be easier to launch on a bigger launcher, say a Falcon Heavy instead of a Falcon 9? (As Danny suggests)
Quote from: A_M_Swallow on 06/29/2011 12:01 amQuote from: CitabriaFlyer on 06/28/2011 11:44 pm{snip}If depots were available in 2015 how else might they be used? Bigger satellites to GEO. The EELV is launched fully loaded and empties its tanks achieving LEO and docking. The propellant depot refills the tanks permitting the upper stage to fly the satellite to GEO.If GEO sats were more accessible, they could be designed to be amenable to upgrades and repairs. Presently the paradigm is design, build, launch and discard.
Right now, everyone is happy buying their gas by the pint at the drugstore because they don't know how a service station is going to work.
I would love to see a largish lunar lander that we intend to use frequently, unmanned for now.
Quote from: Hop_David on 06/30/2011 05:04 pmPresently the paradigm is design, build, launch and discard.I'm resonably sure I've "heard" Jim argue that this is and was never the "paradigm" for Geo-Sats. He was quite vehment about it too
Presently the paradigm is design, build, launch and discard.
Personally, what I'm seeing is that many companies are aware of this point and it's ability to be a major "sea-change" in operations but currently they can't see an economical way to get from where we are now to that point.How would one go about building, and supporting a business case for this type of paradigm shift?
{snip}It seems to me if you want to repair or upgrade a sat, you'd need an Atlas and a Centaur to deliver parts, materials. You'd also need some way to install the parts -- telerobotic hands? And once the repair device accomplished it's mission, where would it get propellant to reach another satellite?If your going to launch an expendable upper stage to repair a satellite, it makes more sense to use the same stages to send up a replacement satellite.The case for this paradigm shift doesn't close until we have a less expensive way to deliver propellant to orbit.