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| By Guy Norris, Frank Morring, Jr. Los Angeles, Cape Town, South Africa
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 Amid preparations for key demonstrations of commercial cargo and crew operations to low Earth orbit, Boeing has revealed studies of scaled-up, mini-space shuttle-like variants of the reusable X-37B orbital test vehicle (OTV) which could be used to return to a runway landing. The larger derivative could be developed for potential delivery of cargo and crew to the International Space Station (ISS), with flight tests of the current version paving the way for a more ambitious stretched version, according to the manufacturer. However, NASA appears to be unconvinced by the derivative plan, describing it as a “trial balloon” aimed at gauging the agency’s interest. The development plan is targeted at providing a larger cargo backup to Boeing’s CST-100 crew vehicle as well as a potential longer-term crew-carrying successor. The concept builds on the ongoing OTV demonstration with the U.S. Air Force, the first phase of which ended with the classified unmanned OTV-1’s December 2010 demonstration flight culminating in an autonomous landing at Vandenberg AFB, Calif., after 244 days in orbit. A second mission, OTV-2, is currently under way. OTV-2 has been in space since March 5 and, assuming it has not already been covertly recovered, the vehicle is expected to remain in space until at least mid-October. William Gerstenmaier, who oversees the agency’s Commercial Crew Development (CCDev) program as NASA’s associate administrator for human exploration and operations, says a commercial X-37 is an idea whose time probably has not come. “We’ve got two cargo providers that are making real good progress,” he says. “We’re making good progress with crew, so I don’t think I would deviate much off of those paths until we show that there’s some benefit. So I think it’s some kind of trial balloon on their part to see if were interested, because there’s limited funding throughout the government. So this is a way for them to see if there’s another market.” In an interview with Aviation Week between sessions at the International Astronautical Congress (IAC) in Cape Town, South Africa, last week, Gerstenmaier said the only possible scenario for a shift to X-37 to send supplies and crew to the ISS would be “in extremis” in the event that the other commercial launch alternatives do not go well. Under its CCDev agreements, the agency could only pursue an alternative if a company defaults or stops work. The business case for these companies is really based on their having a good market share, he says. “The 20 metric-ton [capacity] was derived from what they need for a business case to deliver cargo to ISS, and if I give that business case away that erodes their ability to deliver, and that’s not a good thing,” Gerstenmaier says. NASA already has a CCDev agreement with Boeing to build the CST-100 crew vehicle, a seven-seat aluminum capsule that will ride to space atop an Atlas V, and the company official in charge of that work says the capsule will continue to be Boeing’s entry in the commercial-crew arena as the CCDev effort advances. “Clearly, [X-37B] is an option for cargo,” says John Ebon, vice president and general manager for space exploration at Boeing Defense, Space and Security. “There’s work that would have to be done for that to be used as crew. We internally traded when we were looking at going after commercial crew whether to do a capsule or a winged vehicle based on X-37. Based on the risk associated with development in a fixed-price environment of a winged vehicle as opposed to a simple capsule, we chose to go after a capsule.” Ebon, who also attended the IAC, noted that X-37B evolution study team is supporting Sierra Nevada Corp. as a supplier in its effort to build a lifting-body crew vehicle. But that work is firewalled off from the CST-100 effort, and unrelated to the Boeing CCDev entry, he says. Like Gerstenmaier, Elbon sees the X-37 as a backup, particularly as a cargo carrier in case Space Exploration Technologies (SpaceX) and Orbital Sciences Corp. fail to develop their cargo vehicles. Depending on what happens with cargo providers, it could be a real near-term solution for taking cargo to station, Elbon says. The X-37B evolution study, which harks back to the OTV’s pre-military NASA origins, envisages a three-phase build-up. The first would see the current 29-ft.-long vehicle used for demonstration flights to the ISS. As presently configured, the X-37B, launched inside the 5-meter (16.4-ft.) fairing of the Atlas V, could carry bulky items such as the station’s control moment gyro, battery discharge and pump module, Boeing says. The second phase would see the development of a 165% scaled-up version, roughly 47 ft. long and big enough to transport larger line-replaceable units (LRU) to the station. The larger version would demonstrate operations to and from the ISS, paving the way for a human-carrying derivative in the third phase. This would see a human-rated version transport “five to seven astronauts” says Boeing X-37B project chief Art Grantz. Speaking at the American Institute of Aeronautics and Astronautics Space 2011 conference in Long Beach, Calif., Grantz said, “the next step is a larger cargo vehicle that can deliver and return large ISS LRUs while retiring the risks associated with autonomous transportation of astronauts to and from LEO.” Although many details of the OTV‑1 flight remain unknown—and with OTV-2 shrouded in even more mystery—Grantz says the initial launch was aimed at “making it operate like an airborne test platform.” From a vehicle viewpoint, however, it also successfully demonstrated autonomous de-orbit using “shuttle-style” trajectory and aero-braking maneuvers as well as a “soft landing” on a runway. The test also validated the X-37B’s autonomous guidance, navigation and control system, electro-mechanical flight control system and thermal protection. In addition, during the X-37B’s eight months in space, Air Force controllers demonstrated deployment of the solar wing as well as its subsequent stowage and return for reuse. Photo: USAF | |
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