Three months after the U.S. Air Force’s experimental Orbital Test Vehicle (OTV) returned from a debut spaceflight that spanned 224 days, its sister ship is being prepared for liftoff March 4 on a follow-on mission.
Like its predecessor, OTV-2 will launch aboard an Atlas V booster from Cape Canaveral AFS. The 2-hr. launch window opens at 3:39 p.m. EST.
Exactly what the vehicle, also known as X-37B, will do in space is classified, as are any cargo or payloads that it may carry. The two spacecraft, built by Boeing Phantom Works, resemble diminutive space shuttles. They are intended to test technologies and processes for low-cost, quick-turnaround, reusable space vehicles, as well as serve as orbital testbeds for instruments that could be incorporated into future satellites.
“Once placed in an operational status, the X-37B could have applications to support missions such as technology maturation/validation; space situational awareness; intelligence, surveillance and reconnaissance; on-orbit servicing and repair; satellite deployment and/or retrieval; or orbital debris mitigation,” the Air Force writes in an email to Aviation Week.
The winged vehicles, which are 29 ft. long and 14 ft. wide, are designed to remain in orbit for up to 270 days. OTV-1 returned from flight in good condition, paving the way for launch of OTV-2 with few modifications (Aerospace DAILY, Dec. 6, 2010). A more detailed inspection and analysis of OTV-1 will be undertaken as part of its refurbishment.
OTV-1 has not yet been scheduled for a second launch, but the Air Force anticipates it will return to orbit.
“Because of the short timeframe between the OTV-1 landing in December and the launch of OTV-2 in March, focus was turned to getting OTV-2 ready for launch after the quick-look assessment of OTV-1’s re-entry and landing data and exterior inspection,” the Air Force says. “We will do a more detailed assessment after [the] OTV-2 launch to prove the objectives for a quick, low-cost turnaround.
“OTV-2 builds upon the OTV-1 on-orbit demonstration and expands the test envelope of the X-37B,” the Air Force adds. “This second test mission furthers the development of the concept of operations for and fine-tunes technical parameters of an affordable, reusable space vehicle.” That includes keeping OTV-2 in space longer than OTV-1.
Still, not everyone is a fan of the OTVs. “Because of its weight and relative lack of maneuverability, the spaceplane is not well-suited for a number of missions,” says Laura Grego of the Union of Concerned Scientists. For instance, due to extra structure to withstand repeated re-entries, the vehicle ostensibly would have a harder time carrying payloads to orbit, let alone maneuvering in space, rendezvousing with satellites, and releasing multiple payloads, she said March 2. “Yes, the spaceplane may offer more flexibility and is potentially reusable, but that comes at a very high price compared with the alternatives. We have not seen an analysis that shows why it is worth that high price.”
Officials have said no significant changes were made to OTV-2 as a result of the OTV-1 flight. Minor tweaks include a reduction in the vehicle’s main landing gear tire pressure by about 15% to help avoid repeating the blown tire that OTV-1 experienced upon landing at Vandenberg AFB, Calif., on Dec. 3. The reduced pressure should better accommodate imperfections in Vandenberg’s 15,000-ft.-long runway, the Air Force says.
“Also, based on the demonstrated ability of the electromechanical flight control and autonomous landing algorithms, we’ll place less restrictions on the cross-range and wind conditions required for landing,” the Air Force says.
The Air Force Rapid Capabilities Office manages the X-37B program.