Three weeks after its rousing launch from Cape Canaveral Air Force Station, Fla., SpaceX’s CRS-2 Dragon cargo ship is closing in on its scheduled return to Earth. Splashdown of the commercially-built capsule, carrying around 2,668 pounds of science samples and experiments, has been delayed by at least 24 hours and will now occur no earlier than Tuesday, 26 March, off the coast of southern California, in the Pacific Ocean. According to reports published Friday, the return of CRS-2—the second dedicated resupply mission under SpaceX’s $1.6 billion Commercial Resupply Services contract with NASA—was postponed due to forecasted high seas in the splashdown zone, and if conditions do not improve options for a return as late as 1 April are a possibility.
Despite a troubled start, CRS-2 has proven a remarkable success and an indicator that, once again, SpaceX—the Hawthorne, Calif.-based organization, headed by entrepreneur Elon Musk—can rebound from real-time difficulties to accomplish its primary objectives. Last October, the CRS-1 mission’s Falcon 9 booster experienced an engine-out anomaly, 80 seconds after launch, which doomed a small “piggyback” Orbcomm satellite, yet still provided the impetus to deliver Dragon to the International Space Station. Then, in the minutes following the launch of CRS-2 just three weeks ago, on 1 March, a glitch occurred with Dragon’s maneuvering thrusters which threatened to ruin the mission. Within hours, however, the hard work of SpaceX controllers remarkably reversed CRS-2’s fortunes and a triumphant berthing with the space station was concluded on 3 March.
Dragon transported a wide variety of payloads to the space station, including the first dedicated occupant of its unpressurized “Trunk”: a pair of Heat Rejection Subsystem Grapple Fixtures (HRSGFs)—nicknamed “grapple bars”—which will be installed on the outboard S-1 and P-1 trusses in July, during a pair of EVAs by Expedition 36 crewmen Chris Cassidy and Luca Parmitano. The bars will support the future repair or replacement of ISS radiators. Also aboard the commercial vehicle’s pressurized section were two General Laboratory Active Cryogenic ISS Experiment Refrigerators (GLACIERs), a space electronics box for a Minus-Eighty-Degree Laboratory Freezer for ISS (MELFI), a carbon dioxide removal assembly, and general crew provisions, including fresh foodstuffs.
Of primary concern was the effect that the problem with CRS-2’s four Draco thrusters pods might pose for the return to Earth. The issue now appears to have been resolved and CRS-2 has been given the go-ahead for next week’s return home. Current plans call for Expedition 35 Flight Engineer Tom Marshburn to unberth Dragon from the station’s nadir-facing Harmony node, using the 57-foot-long Canadarm2 manipulator arm, backed up by Commander Chris Hadfield. After separation, the cargo craft will execute a trio of thrusters firings to maneuver to a safe distance for its de-orbit burn. Although the Trunk will burn up during re-entry, the main pressurized capsule will survive the fiery descent through the atmosphere and return to a parachute-assisted splashdown. This makes Dragon, at present, the United States’ only home-grown craft with both upmass and downmass payload capability to and from the ISS.
With around 2,668 pounds of scientific experiments and results, excluding the weight of packaging, this will be Dragon’s heaviest-yet return from space … more than double the amount that it launched with three weeks ago. This includes another GLACIER, laden with biological and other samples stored aboard the station since the CRS-1 mission last year. For scale, the GLACIERs are equivalent in size to a double shuttle middeck locker and are capable of transporting and preserving samples which require temperatures between 4°C and -160°C. Also aboard CRS-2 will be failed or no-longer-needed equipment, including old components from the ISS’ Environmental Control and Life Support System. Recovery forces will bring Dragon back to the Port of Los Angeles, via barge, after which it will be transported to SpaceX’s McGregor, Texas, facility, and samples unloaded and returned to NASA’s Johnson Space Center in Houston.