Matt Pepper, Robotic Arm Instructor
A lot of hard work will be done on the STS-118 shuttle mission, and a couple of arms will be getting a real workout.
These arms don't need exercise, however -- they're the robotic arms on the space shuttle and the International Space Station.
While the space shuttle's Canadarm and the space station's Canadarm2 are capable of some amazing things, they cannot do anything without human operators. Any time one of the arms is used, an astronaut is at the controls.
Operating a robotic arm is a task that demands precision. While objects in orbit are almost weightless, space station components can be massive and could damage each other if they collide. For a construction site, the station is relatively fragile. Great care must be taken when moving station elements. When the shuttle's arm removes a new element from the cargo bay, there may be only inches of clearance. Likewise, when the station's arm moves the element into place, there is little room for error.
Being able to achieve that level of precision requires preparation. Astronauts train for almost everything they will do on a spaceflight, and operating the robotic arms is no exception.
That's where people like Matt Pepper come in to assist. As STS-118's lead instructor for the shuttle's Canadarm robotic arm, Pepper is one member of a team of instructors who are preparing the STS-118 crew to use the shuttle and station arms during the mission.
As with much astronaut training, robotic arm training is done in several ways. In the classroom, astronauts learn the basics of arm operation. Computer and virtual reality exercises simulate operating the arm from on board the spacecraft. Physical mock-ups provide "real-world" training, such as the underwater model in the Neutral Buoyancy Laboratory, or NBL, a large swimming pool that allows astronauts to practice tasks in an environment that simulates weightlessness. The NBL arm allows the astronaut operating the arm to practice with others who are rehearsing for spacewalks. In another facility, a full-scale version of the station arm allows astronauts to pick up lightweight mock-ups of payloads, giving them a real-world demonstration of what the tasks should look like in space.
Besides leading practice for the mission tasks that are planned, the instructors also put the astronauts through contingency training. By tackling these "what-if" scenarios in practice, the astronauts will be better prepared in case something should go wrong during the actual mission.
The STS-118 mission will include several tasks that will involve Space Shuttle Endeavour's Canadarm robotic arm and the space station's Canadarm2.
Those tasks will begin even before the two spacecraft dock, with an inspection of the tiles on the underside of Endeavour, carried out using a boom "held" by the Canadarm.
After the shuttle docks with the station, both arms will have plenty to do, including the installation of S5, the next segment on the starboard, or right side, of the station's "backbone" truss. The S5 segment will be removed from Endeavour's cargo bay by the shuttle's arm. That arm will then position the S5 for the station's arm to take hold of it. The station's arm will then move the segment to its location at the starboard, or right, end of the truss. From there, spacewalking astronauts will complete the process of installing S5.
That's only one of the STS-118 tasks that will involve using the arms to move hardware or astronauts around the station. The second task involves the handoff of the External Stowage Platform #3, or ESP3. After installation by the station arm, the ESP3 will act as a "spare parts rack" for the station should something break in the future.
While certain astronauts are assigned as primary arm operators for a mission, almost every member of the STS-118 crew has been involved in the arm training to some extent.
"Everyone's kind of getting their feet wet with the arm," Pepper said. "We actually taught all six of the crewmembers in some form or fashion."
In particular, he said, almost every crewmember will be involved in the tile inspection performed before docking.
On the STS-118 mission, Educator Astronaut and mission specialist Barbara Morgan will be operating both the shuttle and station arms. Because of astronauts like Morgan who work on both systems, the two training teams are working even more closely together. "Now we're sharing students, so that makes coordination better," Pepper said.
Each of the two arms requires separate training because of their differences. The space shuttle carries the 50-foot-long Canadarm in its cargo bay. The 57.7-foot-long Canadarm2 is capable of moving around the space station. The Canadarm would weigh 905 pounds on Earth, while the larger Canadarm2 would weigh almost 4,000 pounds.
The Canadarm2 is not only larger than its shuttle counterpart -- it is also more complicated. The station arm, for example, is capable of "walking" around the station. Both ends of the arm can connect to ports on the outside of the station that provide power and link the arm to its controller. The arm can then move to a new location by connecting its free end to one of those ports and letting go of the place where it was previously attached.
The controls for the two arms are also very different. While they share a similar hand controller design, the station arm is much more software-driven.
"With the shuttle arm and the station arm, the hand controller is about the same, and that's about it," Pepper said.
To control each arm, Pepper explained, "each vehicle has its own coordinate system and they are not aligned with each other." In other words, directions mean different things on the shuttle and the station, and the astronauts have to understand which way each arm will move when they tell it to go a certain direction. This understanding is especially important when the two arms work together.
To train astronauts to use the arms, the instructors have to be proficient on the system themselves. Even though they can't practice their skills in space, the instructors become pros with the simulated versions, and are able to operate the arm as well or better than the astronauts. The instructors begin by going through the same arm training as the astronauts and increase their proficiency through frequent practice. To really challenge themselves, they can tackle the "greatest hits" of missions using the robotic arms – NASA saves training scenarios for the arms, so the instructors can try their hands on simulations of previous missions. This way, they can see how they fare on some of the most difficult tasks performed with the arms.
"We have to have the same skills as the astronauts," Pepper said. "It's not just knowing the book or having a teacher's manual. They could ask us at any time to do what they’re doing, and they know we know how to do it."
The team also trains to be instructors. Before becoming the lead for STS-118 shuttle arm training, Pepper was part of the Canadarm training team for STS-115. The lead instructor for that mission, Linda Toole, is serving as Pepper's mentor for STS-118, helping him make the transition into the lead spot.
"She works with me beforehand with facility and class preparation to ensure that when I teach the crew they get the best instruction possible," he said. "I do a lot of the crew classes for 118, but I don't shoulder the burden alone."
Pepper, who studied electrical and computer engineering in college, said he enjoys how his job combines that field with training. "In this job, you have to be a teacher and an engineer at the same time," he said.
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STS-118 Shuttle Mission
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