USAF X37B

Boeing Studies X-37B Evolved Crew

LOS ANGELES — Boeing is studying scaled-up variants of the reusable X-37B orbital test vehicle (OTV) for potential delivery of cargo and crew to the International Space Station (ISS) and other low-Earth-orbit destinations.

The development plan is believed to be aimed at providing a larger cargo adjunct to the company’s CST-100 crew vehicle as well as a possible longer-term, crew-carrying successor. The plan builds on the ongoing OTV demonstration with the U.S. Air Force, the first phase of which ended when the classified, unmanned OTV-1 demonstration flight concluded in December 2010 with an autonomous landing at Vandenberg AFB, Calif., following 244 days in orbit. A second mission, OTV-2, is under way.

OTV-2 has been in space since March 5, and assuming it has not already been covertly recovered, is expected to remain in space until at least mid-October. A landing around Oct. 15 will equal the OTV-1’s mission length. Given the 270-day mission endurance limit of the X-37B, as earlier described by the Air Force, the early March launch means the landing at Vandenberg can be expected on or before Nov. 30.

The X-37B evolution study, which harks back to the pre-military NASA origins of the OTV, envisages a three-phase buildup. The first would see the current 29-ft.-long vehicle used for demonstration flights to the ISS. In its current configuration, the X-37B launched inside the 5-meter (16.5-ft.) fairing of the Atlas V could already take bulky items such as the station’s control moment gyros, 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 large enough to transport larger line replaceable units (LRUs) 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 Art Grantz, Boeing’s X-37B project chief.

Speaking at the American Institute of Aeronautics and Astronautics Space 2011 conference in Long Beach, Calif., Grantz says “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 than the first flight, Grantz says the initial launch was aimed at “making it operate like an airborne test platform.” From a vehicle viewpoint, however, it also demonstrated autonomous de-orbit using “shuttle-style” trajectory and aero-braking manuevers 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. During the X-37B’s eight months in space, Air Force controllers also demonstrated deployment of the solar wing, its subsequent stowage and return for reuse.

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LONG BEACH, Calif. — The maker of the X-37B robotic space plane has outlined new plans for the spacecraft and a scaled-up version to support space station cargo deliveries or even carry astronauts into orbit.

The Boeing X-37B robotic space plane — also known as the Orbital Test Vehicle or OTV — is being operated by the U.S. Air Force Rapid Capabilities Office, toting top-secret payloads into Earth orbit.

An X-37B OTV and derivatives plan was outlined here by Arthur Grantz, chief engineer, Experimental Systems Group at Boeing Space and Intelligence Systems in Seal Beach, Calif. He spoke at Space 2011, a conference organized by the American Institute of Aeronautics and Astronautics (AIAA).

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Small test platform

Last year, the X-37B completed its first test mission of 244 days and demonstrated the viability of a small test platform that can return experiments for post-flight inspection and analysis, Grantz reported. "We validated all the autonomous guidance, navigation and control, aerodynamics and aero-heating and the thermal protection system," he said. [Photos: Air Force's 2nd Secret X-37B Mission]

Grantz said the maiden voyage of the unpiloted X-37B proved highly successful after its launch atop an Atlas 5 501 booster. Its landing at Vandenberg Air Force Base in California required no ground intervention during the entire orbital re-entry.

Turnaround of that first vehicle for its next flight has required less time and hours than expected supporting the concept of an affordable, reusable system. In fact, the deployable and stowable solar array used on that first flight is onboard the third X-37B mission, he said.

"From a test vehicle standpoint, the 244 days is the longest duration on orbit for a reusable spacecraft," Grantz told the audience.

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The X-37B looks much like a miniature version of NASA's space shuttle, but is much smaller. Two X-37Bs could fit inside the 60-foot (18-meter) cargo bay of a NASA shuttle.

According to Air Force specifications, the basic X-37B design is about 29 feet (8.8 meters) long and 15 feet (4.5 meters) wide. At launch, it weighs about 11,000 pounds (4,990 kilograms).

A larger version of the space plane design, dubbed X-37C in Boeing studies, would also still fit inside a space shuttle payload bay. Boeing is studying potential unmanned and crewed versions of that larger space plane for future missions.

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Space plane's future uses

In scoping out future uses of the X-37B, Grantz said the craft could let loose a free-flying satellite loaded with experiments bound for low to medium Earth orbits, even to a geosynchronous Earth orbit. [Video: Secretive Space Plane, Meet the X-37B]

At the conclusion of the experiment, the free flyer would lower its orbit and re-circularize where the X-37B could rendezvous with it, collect the experiment portion of the free flyer and then return it to Earth for inspection and destructive analysis.

"We can also demonstrate three-dimensional mapping of near-earth Objects" for asteroid detection purposes, Grantz suggested.

With the retirement of the space shuttle orbiter fleet, Grantz noted that the X-37B represents the only vehicle flying in the world today that can provide a soft 1.5-G class return of sensitive cargo from the International Space Station. The X-37B, as currently designed, is able to support high-value payload delivery and return, he said.

For example, the vehicle can support the return of biological samples or material science crystals that are at the core of the space station's microgravity experiments and unsupported by high acceleration capsules, Grantz reported. Time-sensitive cargo can be quickly extracted from the payload bay after an X-37B’s runway landing.

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X-37C: New space plane for astronauts

No new technology is required to build an X-37B customized to the space station cargo mission, Grantz said. The next step, he said, is a larger vehicle with significant cargo return capabilities for ISS Line Replaceable Units (LRU’s) and experiments requiring a low acceleration return to Earth.[Infographic: Inside the X-37B Space Plane]

Grantz explained that a variety of scaled-up versions of the X-37B space plane have been studied as potential vehicles to carry astronauts or cargo into low-Earth orbit. The studies include looks at transport methods for pressurized and unpressurized cargo transport to and from the space station, as well as future Bigelow space habitats or other forms of space tourism in low-Earth orbit.

The preferred size of these derivatives is approximately 165 to 180 percent of the current X-37B.

The larger X-37C has been blueprinted, sized to support around five to six astronauts with provisions for one that is injured and requires a stretcher.

According to designs in Grantz's paper for the Space 2011 conference, crew-carrying portion of a future X-37C type space vehicle would fly in a pressurized compartment that would fit into the payload bay of the spacecraft. The seats would be arranged along one side of the spacecraft to allow room for moving through the spacecraft in orbit and to provide the crew access to seats on the launch pad.

A hatch in the main body would be used to provide entry to the space plane on the ground, according to Grantz's paper.

Launched atop an Atlas Evolved Expendable Launch Vehicle, this spacecraft would be capable of rendezvous, docking, deorbiting, re-entering, and landing autonomously. But it could also include the ability of an onboard pilot to control the craft, Grantz said.

"Once qualified for human flight, these vehicles could transport a mix of astronauts and cargo to the ISS and offer a much gentler return to a runway landing for the space tourism industry," Grantz's report states.