SpaceX Made Major Progress on Dragon Thrusters, Comm System in 2010

Dragon floats down under three parachutes after its maiden flight to space. (Credit: SpaceX)

SpaceX’s two Falcon 9 launches and the successful Dragon flight captured the public’s imagination in 2010. The company made major progress on two technologies last that are key to its future space plans. These achievements are highlighted in the FAA’s 2011 U.S. Commercial Space Transportation Developments and Concepts: Vehicles, Technologies, and Spaceports report. Excerpts from the document follow after the break, with my comments in italics.


Draco, a SpaceX designed and developed thruster, is used for orbital maneuvering and attitude control of the Dragon spacecraft. The Draco thrusters can generate up to 400 newtons (90 pounds) of force, and they can fire in bursts as short as a few milliseconds for precision maneuvering, or up to several minutes for orbital maneuvering. Depending on the mission, each Dragon spacecraft will use as many as 18 Draco thrusters that receive propellants from eight spherical titanium propellant tanks. Four tanks carry monomethyl hydrazine fuel, and four tanks carry nitrogen tetroxide oxidizer. These propellants have long on-orbit lifetimes, permitting future Dragon flights to remain in space for a year or more. A system of valves provides redundant cross-connection between the propellant tanks for maximum reliability. The Draco thrusters will be used by the Dragon spacecraft for orbital insertion, docking maneuvers, and deorbiting.

In December 2010, SpaceX successfully tested on-orbit maneuvering of a Dragon vehicle during the first test flight under NASA’s COTS Space Act Agreement.

Editor’s Note: This technology solves a major limitation of the Russian Soyuz spacecraft, which must be replaced every six months before its systems decay. The Dragon spacecraft will given extra flexibility to the partners in the International Space Station and to private space station operations such as Bigelow Aerospace. It’s much cheaper to keep a vehicle on station than launch a brand new one every 180 days.

COTS Ultra High Frequency Communication Unit

Illustration of SpaceX's Dragon spacecraft arriving at the International Space Station. Credit: NASA

The Commercial Orbital Transportation Services (COTS) Ultra High Frequency Communication Unit (CUCU) provides a data link between the International Space Station (ISS), SpaceX’s Dragon capsule, and ground control. This system also enables astronauts on the ISS to monitor and control Dragon during uncrewed cargo missions.

Developed by SpaceX under a NASA Space Act Agreement, the CUCU enables the ISS crew to send commands to and receive acknowledgments from the Dragon. The CUCU further exchanges navigation and status data between the Dragon and the ISS. It also provides a communications path between SpaceX Mission Control and the Dragon and can support audio for possible crewed Dragon missions. Weighing approximately 29 kilograms (64 pounds), a CUCU was launched aboard STS-129 in November 2009 and stowed in the ISS ExPRESS 7 rack. The CUCU hardware successfully completed on-orbit checkout in March 2010.

Editor’s Note: This system should get a good testing out later this year when SpaceX launches its first Dragon spacecraft to ISS.