NASA is designing the next generation of spacecraft for astronauts travelling to and from the International Space Station. The new spacecraft will serve as a lifeboat for the International Space Station. No American spacecraft has provided this service since an Apollo command module remained docked to Skylab for about three months from 1973 to 1974.
Currently, the lifeboat function on the space station is served by a pair of Russian Soyuz spacecraft that are docked at all times. Each Soyuz holds three people. There can be six people working on the station at any one time with two Soyuz spacecrafts docked. The crew drops to three when one Soyuz leaves and before another arrives with supplies and three new astronauts.
The new NASA spacecraft must have two capabilities to be considered a lifeboat, according to NASA engineers who are working with organizations developing spacecraft in the Commercial Crew Program (CCP). The spacecraft needs to provide a shelter for astronauts in case of a problem on the station and the spaceship has to be able to quickly get all its systems operating and detach from the station for a potential 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.
The two factors that make it tough for spacecraft designers regarding the lifeboat feature are power and protection from micrometeoroids. Most of the power generated by the space station's solar arrays is dedicated to the station's systems and science experiments. The amount of power dedicated for a docked crew spacecraft is comparable to the amount of electricity used by a modern refrigerator.
"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.
Designers also have the challenge of building a spacecraft strong enough to withstand impacts from micrometeoroids. The easy answer is to add armor to the spacecraft. Unfortunately, it can't carry a lot of armor because it would be too heavy to launch.
Just like in the movie Gravity, the International Space Station is always at risk of being hit by objects in space. Even a pebble the size of a bb can cause life threatening damage to the space station when travelling at 30,000 miles per hour.
The situations when the lifeboat spacecraft will be needed are not only movie fantasy. There have been occasions on the International Space Station when the crew members took refuge in the Soyuz because space debris was passing near the station.
Boeing, Sierra Nevada Corporation and SpaceX are working in partnership with NASA on spacecraft designs that meet the lifeboat criteria. Each company is coming up with its own novel solutions for the best way to meet the needs of a spacecraft that docks with the station and then stays in orbit for seven months.
Scott Thurston is the manager of the CCP's Partner Integration Office at NASA's Kennedy Space Center in Florida. "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."
The new American spacecraft will offer more seats than the Soyuz. The final design will include four to seven seats which means the station can host more astronauts than its current regiment of six. Idealistically, that means more productivity can occur on the station since more people would be available for research duties.
"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."
More science means more discoveries. I can't wait to see what they discover next.