Dragon Arrives at ISS Delivering 150 Science Experiments, Preparations Continue for Wednesday Spacewalk

SpaceX’s Dragon spacecraft was successfully grappled by Japanese astronaut and International Space Station (ISS) commander Koichi Wakata using Canada’s robotic arm, Canadarm2.  Capture was exactly on time at 7:14 am ET this morning. Installation onto a docking port is expected about 9:30 am ET.

Dragon was launched on Friday afternoon on SpaceX’s third operational cargo mission to the ISS — SpaceX CRS-3.  The robotic spacecraft is delivering 3,500 pounds of supplies and equipment, including 150 scientific experiments.  It will remain berthed to the ISS until May 18 and then return to Earth and splash down in the Pacific Ocean.  It is the only one of the five cargo spacecraft that service ISS that is designed to survive reentry, a benefit especially to scientists who want to study the results of their experiments in ground-based laboratories.  Russia’s Progress, Europe’s ATV, Japan’s HTV and Orbital Sciences Corp’s Cygnus are not equipped with heat shields to protect them from reentry forces and burn up as they descend through the atmosphere.  They are used to dispose of trash — another important task.

Among the SpaceX CRS-3  cargo are a new spacesuit and repair parts for three spacesuits already aboard the ISS.   A malfunctioning spacesuit put European astronaut Luca Parmitano in grave peril last summer when his helmet filled with water from the spacesuit’s cooling system.  NASA later determined that a filter was clogged by silica particles that were in the water.  They have replaced the filters and flushed the water systems in the suits.   Parmitano’s suit was used for a “contingency” spacewalk in December and will be used again for another contingency spacewalk this Wednesday.  

Contingency spacewalks, as compared to “planned” spacewalks, are performed when an unexpected problem develops requiring a spacewalk to repair something.  NASA has not cleared the spacesuits for planned spacewalks yet as they continue to investigate the source of the silica particles.  ISS program manager Mike Suffredini said at an April 18 press conference that they are learning a lot about water chemistry and have become more “adept” at how to keep the water clean, but have not yet done their final failure analysis.  However, they feel they have reduced the risk to an acceptable level for contingency spacewalks.

Wednesday’s spacewalk by NASA astronauts Rick Mastracchio and Steve Swanson will replace a broken computer — a Multiplexer-DeMultiplexer (MDM) — on the space station’s exterior.