Weight Forcing NASA To Shrink Orion Crew
Frank Morring, Jr. morring@aviationweek.com 
NASA engineers are "on the verge" of pulling two crew seats from their design for the Orion crew exploration vehicle, at least at first, to save weight.
That would mean that when NASA regains the ability to fly astronauts to orbit in the post-shuttle era, it will start with a crew of four instead of six. Four seats have been the baseline for the version of Orion that would take astronauts back to the Moon, but the initial operational capability (IOC) to deliver crew to the International Space Station (ISS) currently calls for a six-seat version.
Jeff Hanley, manager of the Constellation Program that is developing the Orion, its Ares I crew launch vehicle and the follow-on lunar vehicles, told Aviation Week on April 22 that the Orion design is within "plus or minus a couple of hundred pounds" of the 21,000-pound maximum for the command module set by a requirement to land safely with only two of the three main parachutes deployed.
"Right now we're studying and really on the verge of deciding that we're going to start with four," Hanley said. "That gives us a common lunar and ISS version, but we've sized the system and have a design for six, so we'll grow our capability as we need it."
Hanley said the design change has been developed in consultation with the ISS program, which plans to double the station crew size from three to six by the end of next month. The station could sustain the larger crew size with a four-seat Orion because "our Russian partners are always going to fly Soyuz or something derivative to that, so we'll have the full coverage of being able to get the crew off the station in a pinch on the Soyuz and in the Orion." Presently one three-seat Soyuz capsule is kept at the ISS at all times as a crew lifeboat, and a second will be added to accommodate the larger crew.
Orion consists of a launch abort system that is jettisoned after ascent, a service module that stays with the vehicle until shortly before re-entry, and the command module where the crew rides during ascent, re-entry and en route to the ISS in the initial version. Hanley said the command module weight problem has persisted "for quite a while" as the Orion project has refined its design, but does not include 12-15 percent in growth margin still held against the day prime contractor Lockheed Martin starts bending metal on flight hardware.
"We're going to have the Orion preliminary design review in August," he said. "We'll review where we stand with all of that, and the amount of margin we're still holding back. We're flirting with that limit, but still protecting mass growth allowance and project manager's reserve.
"That reserve is meant to deal with the uncertainties with the design that remain because we don't have actual hardware weights yet; we have hardware predicted weights."
By designing to a four-seat IOC, Hanley said, "that gives us a good amount of early relief while we go and learn about the way the system's really going to perform in the early flights."
AviationWeek.com photo by Jefferson Morris
