Table of Contents

What is the Canadarm2?

The Canadarm2, also called the Space Station Remote Manipulator System (SSRMS), is part of the Mobile Servicing System (MSS), Canada’s contribution to the International Space Station. This system, indispensable (yes! INDISPENSABLE!) to the assembly and maintenance of the Space Station, consists of the Canadarm2, a manipulator robot, and two other key elements: the Mobile Remote Servicer Base System (MBS); and the Special Purpose Dextrous Manipulator (SPDM), a smaller dual-armed robot capable of performing delicate maintenance tasks on the Station.

The Canadarm2, which was installed on the Station by Canadian Space Agency astronaut Chris Hadfield in April 2001, will be used primarily to handle heavy loads and help with shuttle docking.

The SPDM will carry out high-precision operations and assist astronauts during spacewalks. It will be able to work both solo and jointly with the Canadarm2.

The MBS will serve as a work platform/storage area mounted on rails along the outside of the Station. The Canadarm2 and the SPDM will also be able to anchor themselves to the MBS to travel across the Space Station, which when complete, will be the size of a Canadian football field. Imagine yourself trying to cross a football field—it’s pretty big! The Canadam2 certainly deserves a break . . . it works so hard!

Examine the following table carefully. It contains interesting information on the Canadarm2 and its helpers, the SPDM and MBS.

In addition to these three main elements, Canada will supply power data grapple fixtures (PDGFs), which the Canadarm2 and SPDM will use to "walk" on the Station; the Canadian Space Vision System (CSVS); and support and training facilities located at the Canadian Space Agency’s head office in Saint-Hubert, Quebec, where astronauts and cosmonauts from around the world are trained to operate the Canadarm2.

As a reward for its contribution to the International Space Station project, Canada will have access to the Station. This means that Canadian scientists will be able to send up experiments testing the effects of microgravity environments. A Canadian astronaut will also be entitled to work on board the Station for a three- to four-month period once every three years. Stay tuned to find out more about these future missions!

The Other Canadian on Space Mission STS-100

Chris Hadfield wasn’t the only Canadian representative going up in space. A Canadian technological innovation was also in tow on Mission STS-100! It’s called Canadarm2.

Canadarm2: The Next Generation in Space Robotics

Robotic technology. A powerful arm with a powerful grip. Canadian engineers have already demonstrated strength in designing and constructing the Canadarm. They won the right to build a next generation space arm for the International Space Station.

The arm they created is called Canadarm2 or the Space Station Remote Manipulator System (SSRMS).

Canadarm2 is one of three parts that will form the Mobile Servicing System (MSS) that will be used to help assemble and maintain the Space Station in the missions that follow. In the future, the SSRMS will have a platform so that it can slide along the edges of the Space Station. This platform is called the Mobile Remote Servicer Base. This will go up in space in early 2002. Canadarm2 will also be paired up with a two-armed robot called Special Purpose Dexterous Manipulator (SPDM) that can perform very delicate operations. The SPDM will launch in 2004.

Starting with Mission STS-100, Canadarm2 will work in tandem with the Canadarm. They will be used to hand payloads or cargo to one another.

There are a few differences between the two arms. The first is that the SSRMS has more flexibility than the Canadarm. That’s because it has more joints and more capabilities for bending, rotating, and getting to those hard-to-reach places! In fact, it has seven motorized joints. The "wrist" joint is a cluster of three joints that allow for up-and-down, side-to-side and rotational motions. Each joint can rotate 540°--that’s a full turn and a half! You don’t want to try that at home!

Also, the Canadarm has one free "hand" known as the end effector to grasp objects, while Canadarm2 has two ends! One hand of Canadarm2 can clamp down along a portion of the Space Station called a "grapple fixture" while the other hand is free to pick up objects. If the Space Station arm needs to "walk" or move further along the Station, it uses a flipping motion. The free hand clamps down on a grapple fixture, and the other hand frees itself and flips over the clamped hand to another grapple fixture. Only the number of the grapple fixtures limits the walking range of Canadarm2! When it moves, it looks like an inchworm!

Animation Canadarm2 (MPEG: 6,27 MB)

Physically, the Space Station arm is 17 metres long while the Canadarm is 15.2 metres long. Both arms can hold a weight of up to 120,000 kg — the mass of the Shuttle!

Finally, unlike the Canadarm, the Space Station arm will probably never return to Earth. It will stay on the Space Station for the duration of the Station’s life span.

While Canadarm2 is busy working, it will be monitored from Earth at the Canadian Space Agency’s Space Operations Support Center (SOSC) in Quebec. The team of robotics specialists on Earth will act as backup if the astronauts experience any technical problems. This control centre is linked directly to NASA’s Mission Control in Houston so that the team can troubleshoot any problems and offer support.

What’s the Point?

What’s so great about this new space arm? Why did Canada build a brand new one if we already had one that worked? There were two goals that the Canadian Space Agency (CSA) wanted to reach with the new arm.

The first goal was to further develop its expertise in robotics. After building the Canadarm, they saw increased knowledge in this technological area that resulted in spin-off technologies.

Also, they needed to create an arm that could do external repairs on the Space Station. Most of the parts on the outside of the Station can be replaced with Orbital Replacement Units—substitute parts that replace units that wear out or fail.

The second goal was to reserve a spot on the Space Station for Canadian research. Because Canada is making a significant contribution to the Space Station, Canadian scientists are entitled to set up scientific equipment on exterior platforms and on 2.3% of the scientific racks inside the non-Russian portion of the Station. That’s equivalent to one full rack per year during the lifetime of the Space Station! This means Canadian-developed experiments in microgravity and space life sciences can be conducted in space for long terms, instead of relying on short bursts of time when a Shuttle goes up for a mission.

They’ll also be able to conduct experiments in biotechnology, engineering, Earth observation and telecommunications.

Canadian scientists, astronauts, and engineers will be among the first to get their hands on Space Station real estate. It may be as soon as 2002!

The Canadian Space Vision System: The Eyes of Canadarm2

Perfected by Neptec Design Group, the National Research Council of Canada and Canadian Space Agency Astronaut Steve MacLean, the Canadian Space Vision System is designed to improve astronauts’ ability to see in space.

The System works with conventional video cameras mounted on the space shuttle’s Canadarm, Canadarm2 and the Space Station. The cameras are detectors for the Canadian Space Vision System. They follow the movements of special target dots on remotely handled objects. When the object moves, the Canadian Space Vision System tracks the changes in position of the target dots, calculates the object’s position and orientation, and presents this information to the arm’s operator in the form of alphanumeric and graphical displays. All these calculations and functions are performed by a Pentium computer that looks a lot like the computer you’re using to visit this site... Who would have thought!

Canada will help position some 600 Canadian Space Vision System targets on the International Space Station. The targets are needed to improve the Mobile Servicing System, Canada’s contribution to the International Space Station.

The Space Vision System was first used on Steve MacLean’s STS-52 mission. An improved model was then used on STS-74, Chris Hadfield’s first mission. (Do you remember what year Chris went into space for the first time?) Since the STS-74 mission in 1995 (there’s your answer!), the new Canadian Space Vision System has been used on a number of missions. The Canadian Space Vision System was first used to help assemble the Space Station in December 1998, on the STS-88 mission.

Canadarm and Canadarm2: How Are They Different?

The following table gives a quick rundown of the differences between the shuttle’s Canadarm and the Canadarm2 installed on the International Space Station.

You’ll notice right away, of course, that the Canadarm2 is longer, heavier and more sophisticated than the Canadarm. But what are the more subtle differences between grandfather and grandson? Want to know more? Let’s take a closer look...

First, unlike the Canadarm, the Canadarm2 isn’t permanently attached to the Station at one end, as the Canadarm is to the shuttle.

Each of the Canadarm2’s "hands" is equipped with a latching end effector or LEE. A LEE? What’s a LEE? A LEE enables the Canadarm2 to dock with another odd-sounding device, a power data grapple fixture or PDGF.

The LEE and PDGF work a bit like an electrical outlet and a plug. Indeed, as its name suggests, the power data grapple fixture allows electrical power and video data to be relayed between the Canadarm2 and the Robotic Workstation inside the Space Station.

The large number of PDGFs on the Station’s surface will enable the Canadarm2 to move freely around the Station to perform a range of maintenance duties.

Another important difference between the shuttle’s Canadarm and the Canadarm2 lies in their degrees of freedom or motion. The table below explains what a degree of freedom is.

 

While the original Canadarm has six degrees of freedom (three at the wrist, one at the elbow and two at the shoulder), the Canadarm2 has seven (three at the wrist and shoulder, and one at the elbow). Thus, the Canadarm2 is much more flexible that its predecessor. This improved flexibility is due primarily to the fact that the Canadarm2’s joints aren’t linear like those on the Canadarm. Ask your teacher to show you the difference between the Canadarm’s linear joints and the Canadarm2’s non-linear ones. Can you list the advantages and disadvantages of each?

Still not convinced that the Canadarm2 is more flexible? Take a close look at this animation (MPEG) that clearly shows the flexibility of the Station’s manipulator robot.

Are you convinced now?

As mentioned in the table above, another key difference between the two robotic arms is the way they are maintained. While the Canadarm is brought back to Earth after shuttle missions, which last eight-and-a-half days on average, the Canadarm2 will probably never return to Earth. Any necessary maintenance and repairs will therefore have to be done in orbit, initially by astronauts, and later by the Canadarm2 itself, which will be self-repairing.

Any idea how maintenance will be performed on the Canadarm2? No? Most of the equipment used outside the Station, including the Canadarm2, will be composed of orbital replaceable units or ORUs. ORUs are independent units that are replaced when they wear out or fail—a bit like changing a flat tire on the side of the road, except that ORUs are replaced in orbit while the Station circles the Earth...at 27,000 km/h!

Launching and Installing a Giant Robot in Orbit...No Easy Task!

The engineers who worked on designing and building the Canadarm2 had to overcome a number of challenges throughout the project. One of the trickiest, in fact, was figuring out a way to launch the new robotic arm. You must be asking, why don’t they simply put it in the space shuttle and deliver it to the International Space Station? Well, they couldn't because the Canadarm2 had to be able to withstand the incredible force to which it was subjected during the launch. Being both larger (too long to fit into the shuttle’s cargo bay at any rate) and heavier than the Canadarm (it has a mass of 1640 kg compared with the Canadarm’s 400 kg), the Canadarm2 was under greater stress than its predecessor during the eight-and-a-half-minute climb into orbit.

Preparing for the Launch

Unlike the Canadarm, which hangs along one side of the cargo bay, the Canadarm2 had to be folded and mounted onto a U-shaped pallet—a cradle-like structure taking up the entire width of the cargo bay. It was a solution arrived at after a long, highly complex design process.

The extensive preparations for the Canadarm2 launch have been underway since the arm arrived at NASA’s Kennedy Space Center (KSC) in May 1999, where it was tested in the world’s largest swimming pool, the Neutral Buoyancy Laboratory. The Canadarm2 had already been tested several times at the Canadian Space Agency’s David Florida Laboratory to make sure it would work properly in orbit and not be damaged by vibrations at launch. Imagine if you had to pass that many tests!

Once at the KSC, the Canadarm2 was folded into its final launch position and laid in its cradle. This was back in August 2000. Take a look at the picture above!

Installation

Canadian Space Agency Astronaut Chris Hadfield played a major role in installing the Canadarm2 on the Station. During this process, Chris also became the first Canadian to do a spacewalk. Wow!

On Day 4 of the mission, Chris and his American colleague Scott Parazynski donned their spacesuits and waited in the shuttle’s airlock while their fellow crew members use the shuttle’s Canadarm to grab the cradle holding the Canadarm2 and a UHF communication antenna. The cradle was then carefully pushed toward a gripper with lockable jaws on the American space lab, Destiny.

Once the cradle was securely attached to Destiny, Chris and Scott were able to walk out into space and get down to business. No time to waste admiring the Earth! (Did you know that astronauts’ favourite activity, when they have a few minutes of spare time, is to look at the Earth? Apparently the view is breathtaking!) Chris started by attaching a "toe clip" to the Canadarm, which will allow astronauts to anchor their feet to the shuttle arm and be moved around on it as they would in the aerial basket on a fire truck.

Chris and Scott then hoisted themselves on top of Destiny and readied the cables that were used to temporarily attach the Canadarm2 to the Station via its cradle. These cables supplied the 120 volts of electricity needed to keep the arm’s electronic parts warm in the extreme cold of space (your refrigerator, hairdryer and stereo are all examples of appliances that operate on 120 volts of electricity). These cables also provided a computer/video link enabling the astronauts to control the Canadarm2 from the Robotic Workstation that was delivered and installed in March 2001.

While the Canadarm2 was heating up, Chris slid his feet into the toe clip at the end of the Canadarm, installed the UHF communication antenna under Destiny, then returned alongside the Canadarm2.

Riding the Canadarm, Chris and Scott then removed the eight thermal blankets covering the Canadarm2. These blankets were designed to protect the Canadarm2’s camera and computer equipment from the cold of outer space.

Next, Chris and Scott unscrewed the eight metre-long "super-bolts" holding the Canadarm2 in its cradle. They then performed a series of complex manoeuvres to lift out the arm’s various segments, after which the Canadarm2 was fully deployed and the spacewalkers returned to the shuttle. Even though they deserved a good rest after all this hard work, their day was far from over.

The Station crew gave the Canadarm2 its first order: to rise up 90 degrees, readying it to climb out of its cradle and take its first steps . . . It was the Canadarm2’s first test to see if all systems were go. The arm was then correctly positioned to start performing its first tasks the following day.

On Day 10 of the mission, following a series of tests and trials, the Canadarm2 grabbed its cradle and passed it to the Canadarm, which returned it to the shuttle’s cargo bay. This operation was the first Canadian robotic handshake in space. By the time the shuttle returns to Earth, the system will have run through all its basic moves and will be ready to start helping build the rest of the Station.

Booms, Joints, Effectors and Grapplers

Canadarm2 is made up of two long segments called booms. These booms look somewhat like your forearm and upper arm. At each end of the robotic arm are Latching End Effectors, a set of wires that twist and snare (hold really tightly) items that Canadarm2 will lift and move. In between the two booms and at each end of the robot are joints like your elbow. These 7 joints make it possible for Canadarm2 to manoeuvre into hard-to-reach sections of the International Space Station since they can rotate up to 240º. Use your protractor to draw a 240º angle to understand the extent to which Canadarm2 is agile.

Monkey See...Monkey Do!

Picture yourself at the park. You are trying to get from one end of the monkey bars to the other. If you were to start moving forward with your left hand on the first bar, the right hand would swing freely for a moment and then attach itself to the second bar. You would continue this motion until reaching your final destination, the opposite end of the monkey bars.

Like you, Canadarm2 will reach out and attach itself to a connection device called a Power Data Grapple Fixture (PDGF).

This element looks a lot like an oversized thumbtack but it’s critical because it provides Canadarm2 with two very important elements; a place to hold on and the electrical power to keep the robot functioning.

Canadarm2 Functions

Without Canadam2 the Space Station could not be built. In fact, every shuttle mission to the Station after it is installed will need it. It is Canadarm2 that will help build and maintain the Station. Getting the arm installed and working is vital to the rest of the Station’s construction schedule, which is expected to continue until 2006.

Canadarm2 has the capacity to handle large modules and structural elements. At first, it will be used to assemble the Station. Later it will aid in routine maintenance of the Station as well as support resupply tasks.

For the people living on the International Space Station, resupply tasks are similar to grocery shopping, home care, home repairs and garbage collection all rolled into one event. Since the people living on the Space Station, do not have access to the same commodities that we have on Earth, they must rely on resupply missions in order to receive their food supplies, replacement modules to do maintenance repairs, and new experiments.

They also need the resupply missions to send back to Earth any accumulation of waste as well as any experiments that have been completed in order to make room for new supplies.

Canadarm2 will remove the module from the cargo bay of the Shuttle and bring it to the Station so that the crew living on the Station can remove the items within the module. This simple task for Canadarm2 is a procedure that the original Canadarm would not have been able to perform because it is attached to the shuttle and therefore physically unable to reach inside the cargo bay of the shuttle.

Canadarm2 is capable of lifting objects as massive as a school bus. Can you imagine your bus, with you in it, being picked up by Canadarm2?

Canadarm2 will be used to lift different payloads, such as the Station airlock—part of a future mission to the Station—which will permit astronauts to exit the International Space Station for spacewalks instead of having to wait for a shuttle mission in order to perform EVAs.

During Mission STS-100, Canadarm2 and the original Canadarm will perform the first Canadian robotic handshake in space. This manoeuvre is a test run for Canadarm2 to practice manipulating payloads so that it is fully prepared to install the Station’s airlock on the next shuttle mission.

Canadarm2 was transported to the Station on a pallet or cradle. The handshake took place once Canadarm2 was unloaded from its cradle and installed onto the Space Station. Canadarm2 lifted the pallet and moved it to the Shuttle, so that Canadarm could grasp it and return it inside the shuttle’s payload bay.

Since the Space Station is like a home away from home for the astronauts who are living aboard, they must be able to repair and maintain the Station.

Just as your parents must call a roofer to repair a leak in the roof after a spring thaw, the astronauts have to be able to rely on something to repair the Station when necessary.

Canadarm2 with the help of the mobile base and a smaller two-armed robot (both made in Canada) will be the local repair arm for the life of the Space Station.

The designers of the Station understood that the International Space Station is not nearby, so they designed the Station in such a way as to make repairs possible on orbit. Most of the equipment on the outside of the Station is made up of "Orbital Replacement Units." Orbital Replacement Units are like the patches your mother would put on clothes that still fit. The Orbital Replacement Units are self-contained packages that can be swapped for new units when they wear out or fail. The whole Space Station is based on Orbital Replacement Units so it can be repaired and maintained in space. Nothing has to come down, including Canadarm2 itself—all of its components are replaceable.

Helping build and maintain the Space Station will be the most crucial task for Canadarm2, but it has another less visible but equally significant role: it has also provided Canadian scientists with access to the Space Station laboratory facilities to conduct scientific experiments in areas like biotechnology (the study of protein crystal growth and cell culturing), fluid physics (the study of the behaviour of liquids and gases), materials science (the study of materials, how they form and change) and combustion science (how a flame burns). The research undertaken in space may one day provide insight into diseases such as diabetes and osteoporosis. It may even lead to new materials, perhaps new alloys for the next generation of super-computer chips!

Learn about the materials used to build Canadarm2 and why!

As astronauts need to wear specially designed suits—called the Extravehicular Mobility Unit or EMU—to protect them from the hostile environment of space. Space hardware such as Canadarm2 also need protection from micrometeoroids and other space debris, as well as temperature extremes, among other things.

The International Space Station is positioned at 400 km above the Earth's surface. Given its position, it can not rely on Earth's atmosphere to shield it from the intense radiation of the sun. The Space Station is therefore exposed to temperatures up to 149 ºC while in direct alignment with the sun. (At 149 ºC, you could fry an egg on the sidewalk within seconds!).

When the International Space Station passes in the shadow of the Earth, temperatures can fall to -126 ºC, a temperature at which frostbite sets in within seconds.

Multilayer Insulation (MLI) is used to control heat transfer rates. Just as home insulation prevents heat from entering or escaping, an MLI blanket performs the same function for the International Space Station and for Canadarm2. The MLI consists of several layers. Overall thickness varies from 3.2 to 6.4 mm (0.125 to .25 inch). That's very thin! Check on your ruler to see how thick (or thin!) this is.

A single aluminized outer cloth layer provides protection for the intermediate or middle layers of the Canadarm2 from atomic oxygen, meteoroids, or debris. The middle layers provide very efficient thermal radiation protection. An aluminized inner layer will not allow the arm to burst into flame when it is exposed to the intense heat of the sun and it also helps to protect the middle layers from damage during handling and installation. MLI is used both inside and outside the modules and various elements of the International Space Station, including Canadarm2 and the shuttle's Canadarm. This multi-layered blanket is what gives Canadarm2 its white appearance. Did you ever notice that the spacesuit of astronauts performing a spacewalk is also white like the shuttle's Canadarm and like Canadarm2? There is a good reason for this! The color white helps the spacewalkers or their colleagues inside the Space Station and/or the space shuttle to see better when either robots or the spacewalkers are in the shadow of the Earth or the Space Station.

The white material also reflects the heat of the sun reducing the amount of heat reaching the components of Canadarm2. Think about how you dress during the summer. Often on the hottest of days you may try to wear light coloured or white clothing. If you were to wear a black t-shirt or baseball cap, you would soon find that a great deal of heat had been absorbed by them. With no other protection between you and your t-shirt, the heat absorbed by the material would be transferred to your body making you quite uncomfortable.

Underneath this protective blanket are also carefully chosen materials. The gears and motors of Canadarm2 are made of stainless steel and the hinges and joints of aluminum. The booms—or segments—of the arm are made of 19 plies of high strength composite carbon fibers and high performance thermoplastic resin or PEEK. These materials were specially chosen to maintain the life and functionality of Canadarm2 in the hostile environment of space.

After selecting the materials and actually building Canadarm2, the arm was tested carefully to really make sure that it would resist the huge pressure of the launch and the hostile environment of space. What were the types of tests Canadarm2 underwent? Read on!

Teamwork to build Canadarm2

MD Robotics’ expertise in space robotics is recognised as leading edge. MD Robotics developed and built the first Canadarm under contract to the National Research Council of Canada in the late 1970’s early 80’s. The development of Canadarm, Canada’s contribution to NASA’s space shuttle program, made it possible for Canada to participate in the human exploration of space with the establishment of the Canadian Astronaut Program.

Building on the heritage of Canadarm and Canada’s expertise in robotics, MD Robotics, located in Brampton, Ontario is developing the robotics for Canada’s contribution to the International Space Station. MD Robotics is the prime contractor to the CSA and is leading a Canada-wide industrial team in the building of the Mobile Servicing System (MSS), a sophisticated robotic system critical to the assembly, maintenance and servicing of the ISS. Canadarm2 is the first element of the MSS to go to the International Space Station.

MacDonald Detwiller, from Richmond, British Columbia has been involved with the Mobile Servicing System program since 1987; their main area of involvement has been in the development of the Operation and Control Software, which is the central point of control and communication for the Mobile Servicing System.

EMS Technologies, located in both Montreal, Quebec and Ottawa, Ontario has made significant contributions to the Mobile Servicing System including the design of space flight hardware for Canadarm2, SPDM and the Robotic Work Station. It has also delivered over 60 assemblies and subsystems for the Space Station program.

IPM Group, in Halifax, Nova Scotia was responsible for the design, development and fabrication of external electrical wire harnesses for Canadarm2.

SED Systems Inc., located in Saskatoon, Saskatchewan participated in the design of a ground-based system and coordinates Canadian planning, training and monitoring activities associated with the SSRMS.

CAE Electronics Ltd., in Montreal, Quebec has supplied a number of successful projects related to Space Station operations to the CSA. One example is the MSS Operations and Training System (MOTS). Located in Saint-Hubert, the MOTS simulates Canadarm2 operations and is used to train astronauts and cosmonauts in preparation for missions to the space station. It includes simulations of robotic manipulation, 3D visualisation of camera views, support software, graphics animation, person-computer and person-machine interfaces.

FRE Composites of Saint-Andre, Quebec was among other responsible for the design, the fabrication, the assembly and the testing of all ten feet long segments, which make up Canadarm2.

Canadarm2 Testing and Integration

Guaranteeing that Canadarm2 could withstand the tremendous forces during the first few minutes after the Shuttle lifted off the pad was the responsibility of the Canadian Space Agency’s David Florida Laboratory (DFL) in Ottawa.

Items launched on the shuttle, such as Canadarm2, actually have an easier ride than most satellites, which are usually launched on unmanned rockets. Since the Shuttle has humans onboard, g-forces only reach about three times the Earth’s gravity, compared with up to 8 g’s for unmanned rockets. To test the ability of space hardware to withstand G-forces, the DFL uses a "static load" facility that applies a constant, heavy force to the payload in more than one direction and measures the structure’s response.

The DFL ensured that Canadarm2 could withstand the powerful vibrations caused when the Shuttle’s engines ignited and the vehicle plunged through the atmosphere on its way to orbit. The lab tested the ability of Canadarm2 to function in the temperature extremes it would experience in space, and ensured the arm was electromagnetically compatible with other equipment on the Station.

Electromagnetic Compatibility

The Space Station will be abristle with all kinds of electronic equipment manufactured by many different companies from all over the world. It’s critical to ensure these devices don’t interfere with each other.

Stray electromagnetic signals could not only hamper Station operations but could potentially endanger the safety of the crew. This is why every piece of electronic equipment bound for the Station is tested for electromagnetic compatibility. The testing goes in both directions: "we have to prove our equipment doesn’t emit undesirable electromagnetic waves that could cause problems for somebody else on the Station. We also have to prove that we’re not susceptible, that the performance of our equipment will not be adversely affected by other people’s equipment," cautioned Doug Bassett, MSS Deputy Program Manager for Development with the Canadian Space Agency.

Extreme Temperatures

Space hardware is subjected to both extreme heat when in direct sunlight, and extreme cold when shielded from the sun by the Earth or by structures like the Space Station or the shuttle. With no atmosphere to distribute the sun’s heat, transitions between heat and cold can be sharp and sudden. This creates thermal stress that can cause equipment to fail. To test these conditions, the DFL has a number of thermal vacuum chambers of varying sizes that can simulate both the thermal and vacuum conditions of outer space.

Canadarm2 was tested not as a single unit, but component by component, and each one was rated for its own expected temperature range. Each piece of the Canadarm2 was evaluated individually to test its workmanship and guarantee its quality. The entire arm was then assembled and tested on its pallet to ensure that it is 100% fit for spaceflight.

The DFL also performs "thermal balance" tests to predict how space hardware will react to changing temperature conditions in space. The models indicate that this bit should get so hot and that bit should get so cold. The testing involves subjecting hardware to known thermal conditions in the lab and measuring its response to see if the actual temperature responses match those predicted by its designers.