Orbital Robotics: In-space Assembly

Orbital Robotics: In-space Assembly

Assembling large structures in space is an enormous undertaking, and the International Space Station, or ISS, which is longer in length than a football field, is the prime case in point. Its construction was challenging. First, the modules, or compartments, had to be built on Earth, where engineers have access to tools for piecing together an agglomeration of parts. Then, apart from being of suitable size to fit within the rocket fairing, each module had to be structurally reinforced to withstand the violent turbulence of launch. Once in space, a tricky rendezvous-and-docking sequence was employed to join them all together.

The A&R elements belonging to this category provide manipulation and transportation capabilities to assemble, operate and maintain hardware comprising the outside part of Space Laboratories. These elements may range from small robot arms equipping scientific facilities to large arms capable of handling the large structural hardware making the International Space Station (ISS). ESA has developed the European Robot Arm to function on the Russian part of the ISS ESA has also studied several smaller External Robotics means such as EuTEF and EUROBOT.

Upgrade

On-orbit assembly of space structures introduces many advantages. These include inherent serviceability, inherent expandability, launch packing efficiency, ability to launch small units independently, incremental system upgrades, structural efficiency (areal densities of 15 kg/m 2 for conventional hardware), essentially no increase in complexity with size, and the ability to build very large structures (i.e. > 100m). The disadvantage of on-orbit assembly lies in the support system required to perform the assembly. However, the system is inherently reusable, i.e. can be applied to the construction of several components and does not increase in complexity with increasing structural size. In addition, the support system directly supports operational maintenance and repair. Once a structural concept has been defined, the actual assembly is a well-defined repetitive operation, ideally suited to robotic techniques.

ISS Space Robotic Arm

This NASA video features astronaut Dottie Metcalf-Lindenburger giving an overview of the International Space Station’s Robotic Arm.

Canadarm: Canadian Robotics for the Shuttle

Canadarm, Canada’s national icon of technological innovation, made its space debut on the U.S. Space Shuttle on November 13, 1981. Designed to deploy and retrieve space payloads, the robotic arm quickly became a critical element in the Space Shuttle Program. It worked flawlessly for 90 Shuttle missions, spending a total of 944 days in space and travelling the equivalent of over 624 million km. While the Canadarm was retired after the Space Shuttle’s final flight in July 2011, the arm’s legacy lives on through the suite of Canadian robots on board the ISS, as well as the innovations in robotic prototyping being done under the Next-Generation Canadarm Program.

 

STS-133: Canadarm

During STS-133, Canadarm2 will install the Permanent Multipurpose Module and will work together with the Shuttle’s Canadarm to install the Express Logistics Carrier on flight day three. Canadarm2 will also provide support for spacewalking astronauts. Dextre, the Canadian dexterous robotic handyman, will be fitted with a new camera on flight day five. Spacewalkers will also move the failed ammonia pump module from its current location on the Mobile Base System and place it on a stowage platform adjacent to the Quest airlock. As with every shuttle mission, the original Canadarm will inspect the Shuttle using its inspection boom. Canadian robotics flight controllers at the Johnson Space Center in Houston, with the support of the Canadian Space Agency’s Mission Operations Centre in Saint-Hubert, Quebec, will assist the astronauts on the International Space Station by monitoring all operations and repositioning Canadarm2 from the ground in between major operations.

Space Shuttle STS-118 Endeavour Space Station Assembly ISS-13A

ISS Assembly

This annotated animation details the assembly of the International Space Station, from the launch of the first segment in 1998 to today and beyond

Assembly

Future space facilities, like scientific outposts to expand our horizons, solar stations to power our planet, and space hotels to enrich our experience, will be a vast departure from the satellites, shuttles and space stations of today. Space macrofacilities are characterized by immense size, which precludes their launch from Earth as monolithic units, and compels in-space assembly.

Facility venues like high orbits, LaGrange points and deep space are challenges to manned space flight due to risk, cost, and lack of appropriate spacecraft, hence robots are a workforce of choice. Macrofacilities, like solar power stations, will be optimized to such an extent that they will incorporate a wide variety of delicate elements. Hence robotic assembly, inspection, and maintenance (AIM) must succeed on fragile as well as robust facilities. Life expectancy of macrofacilities will be decades, so ongoing maintenance poses long-term requirements for resident robots and requires serviceable facilities.

The vision of these facilities calls for robots that will be self-reliant, autonomous, and capable of attaching to, maneuvering on, and working with fragile space facilities.