May 2, 2014
NASA Partners With US Space Firms To Design Emergency Spacecraft
Brett Smith for redOrbit.com - Your Universe Online
The emergency spacecraft would be docked to the space station in case personnel need to quickly be transported back to Earth, a function currently provided by a pair of Russian Soyuz spacecraft.
Each Soyuz craft is capable of holding three people. This means that with two docked, there can be up to six individuals at a time working on the station. The team lowers to three when a single Soyuz departs and just before a different one arrives during a process called an indirect handover.
NASA’s Commercial Crew Program (CCP) requires that an emergency spacecraft must offer a shelter for astronauts in case there is a problem. Also, the craft must be able to rapidly have all its systems running and separate from the station for a prospective return to Earth.
"You've got to make sure it provides the same capability on day 210 as it does on day 1," said Justin Kerr, manager of CCP's Spacecraft Office.
Designers and engineers must consider two primary factors: power and defense against objects outside the spacecraft. The majority of the electricity generated by the ISS solar arrays is restricted to the station's systems and scientific trials. The amount of power allocated to an escape vessel would be equivalent to that required for a refrigerator here on Earth.
"There's very little power available for these spacecraft so what we're really driving the partners to do is develop this quiescent mode that draws very little power," Kerr said.
The spacecraft would ideally be shut down after it is attached to the station. However, because air flow doesn't readily circulate in microgravity, parts of the cabin might be without air for respiration, unless a powered ventilation system is used to circulate the air.
"You don't want someone to go into the spacecraft and immediately pass out because there's no breathable air in that one area," said Scott Thurston, deputy manager of CCP's Spacecraft Office.
Designers also have the distinctive challenge of building a spacecraft sufficiently strong enough to endure impacts from micrometeoroids, but without a lot of shielding because it would weigh too much to launch. Despite the fact that numerous impacts are not expected, designers are still supposed to show their craft can survive an infrequent hit.
"It's something you have to design for, the magic bb scenario," Thurston said.
He added that CCP gave the private companies a list of specifications their spacecraft need to meet during NASA’s qualifications process for use as in-orbit emergency crafts. Each company is said to be coming up with their own novel solutions.
"There's no rock left unturned," Thurston said. "Some have started out with very extravagant environmental control and life support systems and as they're doing their studies, they're slowly figuring out exactly what they need and what they don't need."
NASA is also calling for the craft to hold four to seven seats, meaning the station could host more astronauts than its current complement of six.
"You never kept more on station than you could get off the station and back home," Thurston said. "It's why we staff that station the way we do. Now, you expand the crew capacity and then the crew and that really expands the amount of science you can do."
Image 2 (Below): Illustration highlighting the need for emergency spacecraft on the ISS. Credit: NASA/Matthew Young