JSC News Release Log 1990/90-022
NASA's First Spacewalk in Over Five Years is Set for November
In November, astronauts will step out the door 243 nautical miles above Earth for the first NASA spacewalk in five years, or as it might be better described, a space ride.
Shuttle mission STS-37 crew members Jerry Ross and Jay Apt will conduct the Crew and Equipment Translation Aid (CETA) Flight experiment in the payload bay of Atlantis. Ross and Apt will try three different methods of propelling a small cart along rails in the bay in an effort to identify the best way to move on the exterior of Space Station Freedom. Necessity, good timing and enthusiasm have pushed CETA a long way in a short time.
"EVA's are something it's easy to get people excited about," said Ed Whitsett, CETA project manager at the Johnson Space Center. “People have been willing to make a lot of sacrifices to pull this all together."
CETA didn't exist until June 1989, after the final payload review for STS-37 had already taken place, Whitsett said. But the experiment, through long hours put in by those supporting it, came together and was ready for the previously scheduled launch of STS-37 this June. The flight crew played a large part in getting the experiment on track for the prospective launch date.
Although mechanical tests and procedure checks of CETA are the primary reason behind the spacewalk, an important contributing factor is the simple need for NASA to take a walk on the high side again.
“We're excited about it," explained Ross, who will make his third spacewalk. "We're anxious to build up the EVA team again, to build up the experience base. We see a large quantum jump ahead in the amount of time spent EVA as space station gets closer."
The five-year lapse has taken a toll on experienced EVA personnel available among astronauts, flight controllers, engineers and other team members.
“The crew needs to get operational experience for EVAs and we need to get EVA inputs for space station design — it's a perfect match," Whitsett said.
By coincidence, Ross was the last American to shut the door on space, after conducting two spacewalks on STS-61B in late November 1985.
"When I got back inside after my second EVA on 61B, I thought that was the finale … I'd never have that opportunity again," Ross said. “But through a strange twist, I'm going to do this one. You know, I smile a lot thinking about it. It is really a fantastic experience you just can never fully explain to anyone.”
A method for crew members to move up and down the 400-foot long space station truss structure has always been planned, but the original concept was akin to a large space golf cart.
"We thought it was overkill," Whitsett said. “It was like taking a bus when all you need to do is go out to the back field on your motorcycle."
Although the simplest method of movement would be a hand-over-hand pull down the truss, with no special equipment except a tether, such a method could cause excessive wear and tear on the truss and suit. Also, it would be difficult to carry cargo.
CETA may be the answer. It is a small cart that runs along a track which can be built into the Space Station Freedom truss. Astronauts would ride prone on CETA, and could pull equipment along behind them. But how to propel the cart, how much stress the various methods of movement would put on the truss and the astronaut, and how fast it can be comfortably and safely moved are questions to be studied on STS-37.
The cart will be mounted on a track in the payload bay, skirted by two handrails for half of the bay and by one rail, to be extended following deployment of the Gamma Ray Observatory (GRO), for the entire distance 46 feet. Apt and Ross will move the cart in three different fashions: lying prone, one crewman will pull himself along the track hand over hand; with the astronaut angled upward slightly, the cart will be changed to accommodate a lever that can be pumped to move it up and down the track, much like an old railroad handcar; and, also with the crewman at about a 45-degree angle, the cart will be propelled by hand-pushed pedals similar to a bicycle - the pedals will generate electricity to drive the cart.
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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