Hello All,

An article (see: http://www.spacedaily.com/reports/N..._DARPA_999.html ) in Space Daily describes yet another spaceplane project of DARPA. (Wikipedia www.wikipedia.org also has an article on the XS-1 [which contains additional links], but it has one of their funky URLs that ends with an ")" and won't open if posted separately.) This spaceplane, however, could possibly lead to a fully-reusable, TSTO (Two-Stage-To-Orbit) space shuttle (I'll explain).

The Space Daily article says that Northrop Grumman, Scaled Composites, and Virgin Galactic have teamed up to produce for DARPA (the Defense Advanced Research Projects Agency) the XS-1 Experimental Spaceplane, a ground-launched winged reusable booster that will carry an expendable upper stage; the system is designed to inject 3,000 pound payloads into Low Earth Orbit. (Other companies [see: http://www.space.com/26530-xs1-expe...e-pictures.html ] have also proposed XS-1 designs.) Another project requirement is quick response, being able to fly the XS-1 (with different upper stages on each flight) ten times in ten days using a minimal ground crew and infrastructure, including just a simple TEL (Transporter-Erector-Launcher) instead of a complex fixed launch pad with service structures. Also:

Boeing has previously proposed a scaled-up version of its X-37B unmanned orbital spaceplane (see: http://en.wikipedia.org/wiki/Boeing_X-37 ), the X-37C, which would transport astronauts. However, an appropriately up-scaled X-37B (incorporating internal propellant tanks and one or more vacuum-optimized rocket engines) could also serve as a second stage for the XS-1, creating a small unmanned TSTO space shuttle. While its payload capability to Low Earth Orbit might (or might not) be large enough to make the system economically viable, it would in any event be an excellent proof-of-concept system as well as a "trainer" for learning how to streamline the between-flights preparations. It would also facilitate a bigger TSTO option:

Since the XS-1 is also designed to be scalable, a large TSTO space shuttle (either unmanned or manned, or both [I'll explain]) could be built using the 26' diameter tankage tooling that was used to produce the Space Shuttle External Tanks (and is being used to build the new SLS stages' tankage). Such a vehicle would be comparable to the fully-reusable, TSTO Phase B Space Shuttle design proposals of the early 1970s, but with the benefits of decades of technological advancements that have been made since then. Such an enlarged XS-1/X-37 vehicle could carry people in a pressurized passenger module mounted in the X-37 orbiter's cargo bay, with provision for human-piloted flight control (in any emergencies, including ascent aborts) in the module, through electrical and/or fiber optic connections to the orbiter's systems. Giving the pilot exterior visibility for landing could be done either via two (for redundancy) externally-mounted TV cameras, or by providing a Mercury capsule-type extensible periscope system. For flights carrying satellites or cargo, the pressurized passenger module would be removed from the orbiter's payload bay.

I hope this information will be helpful.

__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
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