A prestigious aerospace magazine on Sunday laid out what it called "considerable evidence" that the U.S. military funded the development and testing of a small orbital space plane in the 1990s.
In an article posted to its Web site, Aviation Week & Space Technology reported that the two-person "Blackstar" space vehicle may have made more than one orbital mission. But it said the project may have since been "quietly mothballed," possibly for budgetary or operational reasons.
The report was met with skepticism from other aerospace industry observers, and even Aviation Week conceded that the evidence was inconclusive.
In the report, senior editor William B. Scott said that Aviation Week has been investigating "myriad sightings of a two-stage-to-orbit system that could place a small military spaceplane in orbit" over the past 16 years.
"Now facing the possibility that this innovative 'Blackstar' system may have been shelved, we elected to share what we've learned about it with our readers, rather than let an intriguing technological breakthrough vanish into 'black world' history, known to only a few insiders," Scott wrote.
Aviation Week reported that the "highly classified" project involved a large carrier aircraft called the SR-3, modeled on the XB-70 Valkyrie supersonic bomber of the 1960s, as well as a small space plane called the XOV (for "experimental orbital vehicle"). The mothership would carry the XOV under its fuselage, rise to high altitude, then release the space plane at supersonic speeds. After the release, the XOV would fire its rocket engines to rise into orbit, and the mothership would return to base.
At the end of its mission, the XOV would return to Earth along a flight profile much like that of the space shuttle.
Landings reportedly observed
Aviation Week said the system was designed in the 1980s "for reconnaissance, satellite insertion and, possibly, weapons delivery." The report said the Pentagon could conceivably use the system to conduct surprise reconnaissance of foreign military activities that were hidden from regularly scheduled spy-satellite overflights.
Scott wrote that "observed spaceplane landings have been reported" at Hurlburt Air Force Base in Florida, Kadena Air Base in Okinawa and Holloman Air Force Base in New Mexico. To preserve secrecy, the space planes were reportedly transported back to their home base in special C-5 Galaxy transports, and Blackstar's costs may have been charged to other projects such as the National Aero-Space Plane and the Navy's A-12 fighter, the magazine said.
"One Pentagon official suggests that the Blackstar system was 'owned' and operated by a team of aerospace contractors, ensuring government leaders' plausible deniability," Scott wrote. The report identified Boeing Aerospace as the likely prime contractor, noting that Boeing was granted patents in the late 1980s on exactly such a space system.
Despite the patent, engineers had difficulty developing an engine powerful enough for the small spaceplane, Aviation Week reported. It said that a "fuel breakthrough" was achieved in 1990-1991 when a high-energy, boron-based gel was developed to power the rocket.
Aviation Week's report did not make clear exactly why such a program might be shelved — and after reading the report, aerospace experts questioned a number of claims made for the Blackstar concept.
Speaking on condition of anonymity, sources told MSNBC.com that they believed the concept was unworkable, based on principles of rocket design. One source said the mothership would be flying much too slow and too low for a space plane to reach orbital speed after release. When the Defense Advanced Research Projects Agency sought proposals for an unmanned RASCAL satellite launcher five years ago, the specifications called for the carrier aircraft to go much higher, and the submitted designs still needed two stages to reach orbital speed.
Another skeptical expert referred to the boron-based "fuel breakthrough."
"Boron-based fuels were the white hope of the 1950s because they have about 140 percent the energy/weight ratio of kerosene," the expert advised MSNBC.com by e-mail. "The B-70 and F-108 were designed to use them, and production plants were built. But when they actually tested the stuff, it turned out to produce combustion products that were liquid and destroyed the engines. Also, borane compounds are so poisonous they have been considered
as CW [chemical weapon] agents! The whole program collapsed, and B-70 went back to kerosene."