Phil McAlister, Sam Durrance, Robert Walker (left to right) participate in the OSP forum this week. Photo: Jeff Foust

Advocates for two differing generic designs for NASA's proposed Orbital Space Plane, a winged vehicle versus a capsule, made their cases for their preferred concepts during a Washington forum this week, debating the merits of advanced technology versus low-cost designs.

The Capitol Hill event, sponsored by the House Aerospace Caucus, Women in Aerospace, and the National Space Society, was designed to examine the issues surrounding the OSP, a vehicle NASA plans to use as both a crew rescue vehicle for the International Space Station as well as a crew transfer vehicle to ferry people to and from the station. The concept, officially announced last year, has attracted considerable attention in the wake of the Columbia accident and resulting stand-down of the space shuttle fleet.

Despite the name, NASA has endorsed no specific designs for the OSP; an illustration on a NASA web site features several notional designs, including winged vehicles and lifting bodies as well as capsules. This has opened up a debate in not just the aerospace community but in larger policy circles regarding the best approach for a vehicle. The capsule approach in particular has gained traction in recent months as a vehicle that could be developed faster and cheaper than a winged vehicle.

Illustrations of various Orbital Space Plane concepts. Credit: NASA

"The system architecture requirements argue for a 'capsule-type' system," said Sam Durrance, a former astronaut and current executive director of the Florida Space Research Institute. "One that has a robust abort capability, can land anywhere anytime, and is designed for simplicity."

One proposal that has been circulating through the aerospace community in the last several months has been to adapt the Apollo command module design into a capsule-based Orbital Space Plane. A brief study of the concept by current and former astronauts and managers back in March concluded that an Apollo-based capsule OSP could be a viable design, although further study on the specific of that approach was necessary.

Durrance agreed that Apollo could serve as at least a starting point for a capsule OSP. "The Apollo command module meets the requirements for the CRV [crew return vehicle]," 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."

An artist's rendition of a Boeing capsule version of the Orbital Space Plane reenters the atmosphere. Credit: Boeing

While the capsule approach offers the ability to leverage existing technology and systems that would allow the vehicle to be fielded quickly -- Durrance believes the OSP, regardless of its design, must be in service by 2007 to meet the station's needs -- the concept does have its detractors. Some have argues that the capsule approach represents a step backwards in technology and operations, and argue for the development of a more capable -- and potentially more complex and expensive -- winged OSP.

Robert Walker, former chairman of the Commission on the Future of the US Aerospace Industry, told forum attendees that any OSP, capsule-based or otherwise, that depends on using an EELV for launch will cause problems down the road. "It becomes, in the minds of people here on Capitol Hill, a huge step backwards," he said. "It means, essentially, that we're trying to adapt technology that we know how to build."

He believes that any OSP design should be scalable for various missions that will be conducted not only by NASA but also by the Air Force. "The Air Force wants space access, they want the ability to deliver munitions, they many want personnel in space at some point," Walker said. "NASA obviously has the need for a shuttle replacement at the present time, and they have the need to do it in the near term. I believe you can design a scalable vehicle that can meet both of those ends, but it is certainly not going to be a vehicle that looks a lot like the capsule that took people to the Moon."

Such a vehicle, Walker said, should at least initially be able to be launched on an EELV, but eventually could become part of a future two-stage reusable launch vehicle. Such a vehicle could incorporate hypersonic technologies that the Air Force is currently researching as part of its National Aerospace Initiative.

An artist's rendition of a Boeing winged version of the Orbital Space Plane during reentry. Credit: Boeing

The impression that the capsule is old technology could affect the prospects for funding the vehicle in Congress, warned Walker, a former chairman of the House Science Committee. "You will get a question of the investment, which means you will get a question of the politics, which means that the money may not be there in the numbers that we need in the short term to make this all work," he said of Congress. "You have to give them a view of the future, not just a view of the present."

"There's no shortage of opinions about where we should be going," noted Phil McAlister, director of the Space and Telecommunications Division of the Futron Corporation. NASA has some experience developing successors to the shuttle, he noted, learning hard lessons from the failures of X-33 and the Space Launch Initiative. He noted that some of those lessons that appear to have been incorporated into the OSP program include not relying on the commercial launch market, not trying to develop both a new crewed vehicle and a new RLV simultaneously, and not planing to immediately phase out the shuttle once the OSP enters service.

NASA is not expected to settle on a final design for the OSP for about a year, but whatever decision it does make could affect human space transportation for the space agency for decades to come. "Whatever we design and spend money on is going to be the vehicle for the next 20 years," said Walker. "Whatever we do here is going to be around for a long time, so it seems to me that you want something that is going to be adaptable."

McAlister, though, is leery of considering the OSP as a shuttle replacement. "We don't want a shuttle replacement," he said. "The shuttle was developed back in 1972; we had a much different world back then. To say the OSP doesn't do the mission of the space shuttle is not a valid criticism. We don't want the shuttle, we want something next."