FYI,

"Space Gas Station Would Blast Huge Payloads to the Moon"
Popular Mechanics
http://www.popularmechanics.com/science/air_space/4224660.html?
series=35

: Boeing has unveiled a radical redesign of NASA's plan to return to
: the lunar surface: save weight (and money) by saving gas for an
: orbital fill-'er-up, then shoot 15 times more material to the moon.
: Can the space agency jive with private space to get the new
: propellant depot off the ground?

: The rocket equation has always had one frustrating yet inevitable
: consequence: For every pound of payload headed for, say, the lunar
: surface, NASA needs hundreds more pounds of hardware and propellant
: during low Earth orbit—and many times that on the launchpad. For
: example, NASA's planned Ares V vehicle (a modern-day replacement
: for the Saturn V that delivered our first visitors to the moon over
: 30 years ago) will weigh more than 3500 tons prior to launch from
: Cape Canaveral, Fla., but land just 18 tons of weight on the
: moon—only two tons of which aren't the lander itself.

: Because each post-shuttle era launch will cost billions of dollars,
: NASA is crunching the numbers on how to get more lunar payload
: "bang" for its transport vehicle "buck." Boeing proposed what might
: be the ultimate problem solver at the AIAA (American Institute of
: Aeronautics and Astronautics) Space 2007 conference here last week:
: a low Earth orbit gas station, or propellant depot, to refill the
: lunar-injection vehicle tanks, fill up NASA's new lander and
: deliver dramatically more efficient payloads to the surface of the
: moon.

: NASA's current mission plan calls for the Ares V to send the new
: lunar lander and its payload into Earth orbit. Once there, Ares V
: would not only have to dock with the Orion crew vehicle (launched
: separately on the Ares I rocket) but also restart and provide the
: initial burn to send the assembled system into a trajectory toward
: the moon.

: Boeing's alternative would combine the Orion rendezvous with a
: pitstop for gas, allowing the Ares V to lift off from Earth with a
: much larger payload—and an empty lander. Boeing says this would
: allow NASA to deliver about three times as much mass to the lunar
: surface, and over fifteen times as much payload. What's more,
: Ares V could then send the lander-Orion package all the way to
: lunar orbit with full tanks, rather than NASA's current plan to use
: extra propellant in slowing down before soft landing.

: Of course, there's no such thing as a free launch. In order for the
: propellant depot to become a reality, it has to reach orbit—and,
: more important, so does the gas.

: Boeing's plan is to build the depot in pieces like a stripped-down
: International Space Station, only in modules based on the upper
: stage of the Delta launch vehicle. Two depots would provide
: redundancy, each one with a total capacity of 175 tons of liquid
: oxygen/liquid hydrogen (25 tons for the lander, 125 for the rocket,
: with margins for boil-off and other contingencies). And while many
: of the necessary parts and operations (i.e., orbital cryogenic
: storage and transfer) still have to be developed and matured,
: they're plausible—and critical for a space-faring civilization
: anyway.

: How the propellant would reach such a pitstop in the sky is really
: the beauty of Boeing's concept. NASA has been seeking ways to
: involve both international partners and the commercial sector
: — Michael Griffin, the agency's administrator, told PM recently
: that such a "private/public synergy" was "crucial for the future"
: — but NASA has been reluctant to put any partner on the critical
: path. The good news? Anyone can make propellant, and anyone can
: deliver it. The orbital reservoir will allow for different
: quantities from tanker vehicles both small and large. The payload
: itself is cheap, so even low-reliability launchers could
: potentially be used.

: If one provider doesn't deliver, another can pick up the slack,
: whether it's based in the U.S. or overseas. It's an ideal means to
: provide a large market for a variety of launch providers, driving
: the competition necessary to reduce launch costs. And the lower the
: propellant costs get, the lower the cost of per-pound lunar payload
: delivery gets—space economics at its finest.

: Down the road, Boeing's gas station could provide even more
: benefits than an improved lunar payload. Communications companies
: could improve their satellite payloads to geostationary orbit and
: beyond. NASA might be able to combine the dual launches in its moon
: program, or make its lunar landing vehicle reusable, with another
: depot using propellants produced on the moon. Because most of the
: mass necessary to get to the moon is propellant (though Boeing
: would never say so), a space gas station might even eliminate the
: need for a heavy-lift launcher altogether, increasing the launch
: rate of smaller, cheaper vehicles, which in turn could cut costs
: for getting to the moon and, eventually, Mars.

Mark Reiff