Rocketry Planet

As the last mission of Shuttle Atlantis was coming to a close, a small hatch in the cargo bay opened and deployed the PSSC-2 spacecraft. PSSC-2 (PicoSatellite Solar Cell testbed 2) is a technology demonstration spacecraft built by the Aerospace Corporation for the US Air Force.

The spacecraft's form is fairly typical of other picosatellites; its 8.2 lbm frame carries two technology demonstration experiments, along with a three-axis stabilization system, communications and control equipment, and solar cells to power the onboard systems. Design and integration took only six months, due to the sudden decision to fly STS-135.

A 3D rendering of the spacecraft, showing the four thruster assemblies.

PSSC-2 was deployed on July 19th, following the undocking of Atlantis from the space station, and quickly made itself famous by taking the final on-orbit photos of the Shuttle. To ensure mission longevity, four small thrusters were included on the spacecraft, each using the propellant grain and nozzle assembly from an Aerotech E28T rocket motor. On November 4th, the first of these motors was fired to raise the orbit and increase the mission duration. According to the astrodynamics department at Aerospace Corporation, "It is believed that this was the first firing of a rocket motor on a spacecraft this small." Robert Plunkett, of Aerospace, added that this firing "marks the first time a satellite this small has re-boosted itself," one of the keys to success for the mission.

Additionally, it was confirmed that a Copperhead igniter was not used to perform the ignition. "It was very tricky to get them to light in a vacuum. We looked into a lot of things, including copper thermite and several types of bridgewire materials," according to Aerospace.

More information on the PSSC program can be found at Aerospace's website: http://www.aero.org/publications/cro...er2009/06.html.