Capsules and winged vehicles are the two leading concepts for the Orbital Space Plane. (credit: NASA/MSFC)

Two directions for OSP

by Jeff Foust
Monday, August 4, 2003

When NASA officially announced the Orbital Space Plane (OSP) project late last year, it seemed like a relatively distant, long-term project. NASA didn’t plan to have the OSP ready as a crew return vehicle (CRV) for the International Space Station (ISS) until 2010, and as a crew transfer vehicle (CTV) launched atop an expendable vehicle until 2012. This schedule would presumably give NASA enough time to determine exactly what it wanted the OSP to do—or change its mind and start over again.

The post-Columbia environment has changed that mindset. The loss of the shuttle and its effect on the ISS has given the project new urgency. NASA officials have recently announced that they are planning to move the schedule for the OSP up by two years, with a CRV version ready by 2008; the agency has yet to decide, though, whether to move the introduction date of the CTV up to 2010. Some have even argued for a more aggressive development schedule, noting that Russian guarantees to provide Soyuz spacecraft for the station expire in 2006.

This urgency has provided momentum for an alternative OSP concept. While not explicitly stated by NASA, most assumed that the OSP would, in fact, be a space plane, a winged vehicle capable of gliding back to a runway landing like the shuttle. However, the top-level requirements issued by NASA earlier this year did not rule out the possibility of developing a capsule to fulfill the OSP’s role. Such a capsule, touching down on land like Soyuz or splashing down in the ocean like Apollo, could conceivably be much easier (and hence faster and cheaper) to develop. A study conducted by several veteran engineers and astronauts, including John Young, even made the case of deriving the OSP from the command module used on Apollo. (See “Orbital Space Plane: Back to Apollo?”, May 5, 2003)

These two approaches to OSP—winged vehicle versus capsule—have become the center of debate in the program. The arguments for and against each approach were crystallized in a Capitol Hill forum late last month organized by the House Aerospace Caucus, National Space Society, and Women in Aerospace. The event, which drew a standing room only audience in a House hearing room early on a Monday morning, illustrated the advantages and disadvantages of capsules and winged vehicles.

The case for a capsule

Samuel Durrance, a veteran of two space shuttle missions and current executive director of the Florida Space Research Institute, is a strong advocate of the capsule approach for OSP. “The system architecture requirements argue for a ‘capsule-type’ system,” he said. “One that has a robust abort capability, can land anywhere anytime, and is designed for simplicity.”

Durrance argued that the shape of the OSP is dictated by its flight environment. During launch needs a nose cone or be encapsulated in an aerodynamic payload fairing; it also needs a blunt or flattened bottom for launch aborts. During reentry the vehicle needs a blunt or lifting body shape; wings are desirable only for runway landings. These requirements, Durrance believes, argues more for a capsule approach than for a winged vehicle.

Durrance also advocates looking at the Apollo spacecraft at least as a starting point for a capsule-based OSP design. “The Apollo command module meets the requirements for the CRV,” he said. “The addition of a small service module behind that capsule could provide the crew transfer vehicle support. It could be launched on an Atlas [5] or a Delta [4].”

Such a system could also take advantage of existing launch and payload processing facilities at Cape Canaveral as a way to reduce costs. “We could establish an assembly line for recovery, refurbishment, integration, and launch,” he said. “We should try to minimize the changes needed in Atlas and Delta launch vehicles for accommodations of crews.”

The Apollo heritage and relatively simple design would allow a capsule OSP to enter service relatively quickly. Durrance said he believes such a vehicle can—and must—be ready by 2007 in order to meet station requirements. While not putting a price tag on the system, he believed that a capsule would also be less expensive to develop than a winged vehicle.

page 2: the case for a winged vehicle >>