Satellite Technology Feature Article
SpaceX Dragon Recovers, Arrives at International Space Station
By Doug Mohney, Contributing Editor
After a rough start, a SpaceX (News - Alert) Dragon spacecraft arrived at the International Space Station (ISS) on March 3, with a hatch opening at 1:14 p.m. ET. The Dragon, launched from Cape Canaveral Air Force Station on March 1, had thruster problems that took six hours to resolve.
Originally scheduled to arrive at the space station on March 2, Dragon's problems became apparent about 11 minutes into flight after a successful and apparently flawless launch onboard a SpaceX Falcon 9 rocket. Only one of the spacecraft's four thruster pods were functional, triggering an immediate round of troubleshooting and delaying deployment of the vehicle's solar panels.
A combination of valve cycles and "pressure hammering" was used to clear an apparent blockage or stuck valve in the oxidizer pressure lines, enabling SpaceX engineers to bring back all four thruster pods back on line around 4 p.m. and start a series of burns to even out Dragon's orbit and put it on an approach to the space station.
NASA flight safety rules require at least three of the four thruster packs to work. The long, careful approach to ISS enabled SpaceX and NASA to gain confidence in the thrusters for a safe rendezvous and berthing.
SpaceX was cleared to start Dragon toward ISS on the evening March 2, with the spacecraft approaching close enough to be captured by the space station's robotic arm at 5:31 a.m. on March 3 and subsequently attached to the Harmony module of the station by 9:00 a.m. The crew onboard station opened up the hatch ahead of schedule, something that's happened in both previous Dragon visits. Faster hatch opening may be due to presence of "bonus" food items tucked aboard the Dragon at the last minute, with ice cream delivered on the last trip and apples stashed onboard this one.
Dragon delivered nearly 1,300 pounds of supplies to support continuing space station research experiments. It is scheduled to return to Earth on March 25, with a splashdown in the Pacific Ocean off the coast of Baja, California. On its trip back, it will return with nearly 2,700 pounds of science samples, including results from human research, biology and biotechnology studies, physical science investigations, and educational activities.
The SpaceX-2/CRS-2 flight marks the third successful arrival of a Dragon at ISS, the fourth flight of Dragon in orbit and the fifth mostly successful flight of the Falcon 9 v1.0 rocket. "Mostly successful" means all the primary payloads were delivered. On the previous Falcon 9 launch, one of the 9 first stage engines was shut down. The primary payload (Dragon) was successfully delivered into its insertion orbit, but the secondary payload, an ORBCOMM (News - Alert) satellite, was unable to be put into orbit due to timing safety constraints on a relight of the Falcon 9 second stage.
SpaceX will roll out an upgraded Falcon 9 v1.1 vehicle for its next launch. The vehicle will use more powerful Merlin 1D engines capable of lifting more weight, a redesigned layout of the 9 first stage engines, and larger fuel tanks to improve payload capability from around 9,000 kilograms up to 13,000 kilograms.
Edited by Brooke Neuman