On Friday, August 3rd, NASA announced the selection of three competing proposals that will be funded to develop an initial capability for ferrying astronauts to and from the International Space Station – the SpaceX DragonRider, the Boeing CST-100, and the Sierra Nevada Corporation’s Dream Chaser.
Each proposal offers unique strengths and capabilities to provide the United States with expanded access to our investment in the Station and avoid dependency on a single launch vehicle, as is currently the case with the contract to provide crew rotation and lifeboat services through the Russian Soyuz capsule.
DragonRider is an evolution of SpaceX’s unmanned Dragon cargo vehicle, which successfully berthed with the ISS earlier this year, and will be enhanced with a series of SuperDraco thrusters that will provide both launch escape and powered ground landing capabilities. It will launch on SpaceX’s own Falcon 9 booster.
CST-100 builds on Boeing’s experience as prime contractor for the space station to offer a more traditional, but still versatile, capsule and will use the venerable Atlas V booster. Boeing has also partnered with Bigelow Aerospace on this project.
Dream Chaser is the most different from the other two offerings in that it will also launch vertically on an Atlas V, but it uses a lifting body design derived from NASA research to land horizontally on a runway. This approach promises faster turnaround times for crew and sample return and, potentially, a more benign landing for sensitive equipment and experiments.
All three vehicles have the ability to carry up to seven people to the ISS or some combination of cargo and crew. This is important because the availability of the crew to do experiments is the single greatest limiting factor on ISS science today, as astronaut and two-time visitor to the Station, Dr. Don Pettit, testified to Congress in July.
Only 35 hours per week, on average, are currently dedicated for crew support of science activities. The six crew members must spend the rest of their time maintaining the Station and attending to the other necessities of life on-orbit. This limitation results from the fact that the Soyuz capsule can only carry three people at a time and we must have enough vehicles docked to the Station to ensure everyone can evacuate in an emergency.
The expanded capacity of the US commercial crew vehicles will make it possible to fly more people to the Station and ensure their safe return. Every additional Station visitor or resident beyond the six-crew baseline could devote their entire work day to supporting science and research activities. So, not only will this new generation of crew vehicles promote high-tech spaceship development in the US, these spacecraft also promise to significantly increase the utility of the ISS National Laboratory itself.