At 8:35 p.m. EDT on Sunday evening, the Space Exploration Corporation (SpaceX) launched its Dragon spacecraft on the first ever commercial resupply mission to the International Space Station (ISS).
The launch itself relied on tried and true methods. The Dragon spacecraft was perched atop a SpaceX Falcon 9 rocket for most of its journey into orbit. It shed the rocket’s two stages as it went, achieving orbit in roughly 10 minutes, ready to deploy its solar panels for power as it zips around the Earth. It will take nearly three days for it to catch up to the ISS and maneuver into position to dock with it. Canada gets to wave the flag a bit once the capsule has been given a final ‘go’ for docking.
As the spacecraft approaches to a distance of 10 metres from the station, it will hold position at this ‘capture point’ and astronauts Akihiko Hoshide of Japan and Sunita Williams of NASA will use the station’s 18 metre Canadarm2 to reach out, snag the Dragon capsule and guide it in to dock with the station’s Harmony module.
The Canadarm program is run by the Canadian Space Agency, and they have produced two Canadarm models.
Canadarm was built for NASA’s Space Shuttle program. The first was installed on the Space Shuttle Columbia (STS-2) in 1981, and four more were delivered to NASA between 1983 and 1993. One was lost during the Space Shuttle Challenger accident, however there was no Canadarm installed on the Space Shuttle Columbia on its last mission. Overall, the Canadarm was used on 90 missions over 30 years, and was retired along with the shuttle program in July 2011.
Canadarm2 was built specifically for the International Space Station. It incorporates several design improvements. The original Canadarm was permanently affixed at one end to the Space Shuttle that carried it, whereas the Canadarm2 has ‘Latching End Effectors’ (LEEs) at either end of it, allowing it to ‘walk’ to any point on the station that has a Power Data Grapple Fixture (PDGF), which supplies the arm with power, as well as data and video feeds. The Canadarm had six degrees of freedom — shoulder pitch, arm yaw, shoulder roll, elbow pitch, wrist pitch and wrist yaw — making it similar to a human arm. In the Canadarm2, the developers incorporated one more degree of freedom — wrist roll — matching the capabilities of the human arm.
One of the more interesting design features of the Canadarm2 is that it has a sense of ‘touch’. The Dextre, or Dexterous Manipulator, is a robot that attaches onto the end of the Canadarm2. Using force-moment sensors, Dextre is able to ‘feel’ exactly how much force it is applying to anything it touches. It even calculates how much force it needs to apply to a task, then relay that information to a human operator.
Rounding out Canada’s robotic contributions to the ISS is the Mobile Base System, which moves up and down the length of the station on tracks, and acts as a mobile platform for the Canadarm2 and ISS astronauts during space walks.
The Canadarm2 will detach the Dragon spacecraft from the ISS on or around the 28th of this month, for its return trip to Earth. It will again be put to use in docking procedures when the Orbital Sciences Corporation launches its own resupply mission in a few months.
Find the latest SpaceX updates here or visit NASA’s page for the latest ISS news.