Posted on May 13, 2012 by Samantha Cristoforetti
Outdoor staircases and brain gymnastics
I’ve been in Montreal for a week now, staying in the charming neighborhood of Plateau Mount Royal and spending full days of robotics training at the Canadian Space Agency.
I haven’t ventured far beyond the commute route so far, except for the brief stroll to nearby cafés for breakfast, a little daily ritual that has progressively shifted later in the mornings as I have slowly digested the six-hour time shift from Europe. I have taken great pleasure in exploring the little quaint streets flanked by trees and row houses, each with a unique façade and with an outdoor staircase leading to an independent entrance on the second floor. Straight or curved, simple or elaborate, rigorously in metal with open steps, these external staircases conjure up a dynamism that matches the colorful livelihood of the neighborhood.
It’s a delightful way to start the day before making my way to the facilities of the Canadian Space Agency for training on the Space Station Robotic Manipulator System. Short: the SSRMS. For friends: the Canadarm2. In case you ever wondered how a 400-ton structure was put together on orbit, the short answer is: piece by piece, with the help of the SSRMS.
You can imagine the Canadarm2 as a robotic replica of your own arm in a bigger size. It has a shoulder, an elbow and a wrist. Like your arm, it has two straight booms between the joints. And like your arm it can bend the elbow and it can rotate shoulder and wrist in pretty much any orientation. In engineering terms it means that it has seven degrees of freedom, although we can lock one of degree of freedom to force the arm to move in a more controlled way. Station is precious; bumping into it is not an option.
To train future ISS crewmembers in SSRMS operations the Canadian Space Agency has Robotic Work Stations that are identical to the ones on orbit. There are hand controllers for translation and rotation, a computer and a control panel to configure the system and to input commands, and three monitors for camera images. There is no real arm, of course, but simulation software runs in the background and the camera views will show you exactly what you would see if you were flying the arm on orbit.
A typical simulator session might well start with what might look like playing with a toy. On a small-scale model of the robotic arm we reproduce the initial configuration based on the given deflections of each joint. I like to see it as a warm-up exercise for the brain.
If you’re a model-builder you’ll love what comes next: to be able to visualize the arm movement with respect to the Space Station, we have a tremendously detailed rapid-prototyping model of the ISS right next to the simulator workstation. I find it an object of intrinsic beauty, I’ll confess. But it’s of course intended as a tool of visualization and as an aid in the extensive brain gymnastics to come: mentally flipping camera images, predicting how the arm movement will look from different points of views, identifying the best camera combination to monitor clearances from structure, determining hand controller inputs in different coordinate frames, visualizing joint movements – these are some of the tasks that are sure to keep your brain on its toes as you fly the arm.
After one week of training I am starting to be familiar with nominal basic SSRMS operations. I’m now looking forward to learning next week about off-nominal situations like singularities and self-collisions, as well as practicing free-flyer captures, which consist in maneuvering the arm to grapple a vehicle that is not attached to the Space Station.
You can expect free-flyer captures to become more and more frequent on ISS in the coming years. Not only astronauts will continue to capture and berth the Japanese resupply ship HTV, but they will soon start doing the same for the new US commercial resupply vehicles Dragon and Cygnus. First Dragon capture is coming up soon, and I think it will be a historic moment. Make sure to watch!