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The first two versions of CETA are called the manual and mechanical cart designs. The third is the electrical design. All of the versions include brakes and provisions for moving in reverse, which, for the electrical version consists of turning the pedals backward, creating a reverse current that in turn drives the electric motor backward.
Ross and Apt will evaluate the amount of energy required to move each version; comfort; how secure they feel moving in them; control; and visibility. Sensors on the track and cart will provide information on the amount of stress each version places on the track and handrails. Although CETA is a one-person cart, Ross and Apt also will propel themselves “piggyback" on each version to test the cart's cargo-carrying ability.
The astronauts also will test a one-person “tether shuttle," a very simple, small cart designed to attach a tether to so it can slide along as an astronaut pulls hand-over-hand along the railway. The "tether shuttle” is intended as a way for one crew member, Carrying no extra cargo, to move around if the main cart were in use or broken.
CETA will take up most of the single, six-hour spacewalk planned, but Apt and Ross will do some additional tasks. Using the shuttle's robot arm, they will evaluate how much flexibility can be allowed in the Astronaut Positioning System (APS) and how quickly an astronaut can be moved comfortably at the end of an arm. The APS is a manipulator arm planned for use when astronauts begin assembling the truss structure for Space Station Freedom. It will move an astronaut, standing in foot restraints at its end, from place to place to assemble the various joints.
Using the Crew Loads Instrumented Pallet (CLIP), an EVA workstation mounted on the side of the shuttle's bay, the astronauts will gather more information on stresses imparted to structures during space work. The pallet part of CLIP has flown twice aboard the shuttle.
The results of CETA and the other EVA experiments scheduled on STS-37 could make some designs for Space Station Freedom spacewalk aids less complex, Whitsett said.
"It has been kind of a crash program, but there's been a real fine team," Whitsett said. "It's fallen into place quickly and smoothly."
The launch of STS-37 originally was scheduled for June, but it has been reset for November. The delay is disappointing for those who've worked on CETA, but the extra time won't be wasted.
"The time will allow for some things we were a little pressed on to be double-checked," Whitsett said.
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