Spaceflight Now: STS-92 Mission Report

100th shuttle flight packed with dramatic space work

Posted: September 19, 2000

The sun rises on Discovery at launch pad 39A. Photo: NASA-KSC
The shuttle Discovery is poised for blastoff Oct. 5 on the 100th shuttle mission, a high stakes flight to mount an 18,400-pound truss housing four stabilizing gyroscopes and critical electronic gear on the international space station.

While providing fuel-saving stability for the growing lab complex, the so-called Z1 truss also features the station's main communications antenna and will serve as the temporary attachment point for a huge set of power-producing solar arrays slated for delivery in December.

Operating the shuttle's 50-foot-long robot arm, Japanese astronaut Koichi Wakata is charged with moving the boxy Z1 truss from Discovery's cargo bay to the top, or zenith, port of the U.S. Unity node, one of the three modules currently making up the space station.

Then, four back-to-back spacewalks by a quartet of astronauts working in two-man teams will be staged to wire up the truss and prepare it for arrival of the solar arrays in December.

The spacewalkers also will help mount a pressurized docking tunnel to Unity's Earth-facing, or nadir, hatch, which will then serve as the primary docking port for upcoming shuttle visits. The forward-facing port currently used for shuttle dockings is where the U.S. laboratory module Destiny will be attached in late January.

During the fourth spacewalk planned by Discovery's crew, Jeff Wisoff and Michael Lopez-Alegria also will test fly small emergency jetpacks that serve as the last line of defense for space station assembly crews.

Illustration shows the new docking port being transported from shuttle bay toward installation on Unity. Photo: NASA TV/Spaceflight Now
Should a spacewalker ever become untethered and drift away into open space, the jetpack could be used to fly back to the safety of an airlock. To make sure, Wisoff and Lopez-Alegria will take turns hauling each other back to Discovery's airlock in a simulated emergency.

Once the spacewalks are out of the way, Discovery's international seven-member crew plans to re-enter the space station to deliver supplies and to complete the electrical integration of the Z1 truss.

"We're looking forward to a very rich, varied mission," said spacewalker William McArthur. "It's got anything you could ever want to do in space. If you're a real space cadet at heart, it's just a dream come true."

Said Lopez-Alegria: "If you're in the space business, it just doesn't get any better than this."

Or more difficult.

Shuttle mission STS-92 rivals a Hubble Space Telescope repair mission in sheer complexity. But as NASA launches a steady stream of station assembly flights over the next five years, complex multi-spacewalk shuttle missions will become the rule, not the exception.

The shuttle Atlantis's launch Sept. 8 on the 99th shuttle mission was the first of nine flights planned over a 12-month period, NASA's most intense period of launch activity since the pre-Challenger era. The agency plans to routinely launch seven flights a year with a surge capability of eight.

Inside the Mission Control Center just before liftoff of Atlantis on Sept. 8. Photo: NASA-JSC
"Flying eight flights a year was not outside the scope of what we did in the early part of the program and we have a fairly good understanding of what it takes to do that," said veteran shuttle flight director Phil Engelauf. "I will concede that also manning the station consoles and flying two vehicles at the same time does put an increased stress on the available manpower.

"It's challenging, it's demanding, it's hard to work multiple projects at the same time and that's what we're going to have to do," he said. "But at the same time, that's what people want to do, that's why we came here. We'd like to fly eight flights a year more than we'd like to fly two or three or four flights a year.

"I think now that the training has gotten rolling and we're picking up steam, I think you're going to see people hitting their stride, with a renewed sense of enthusiasm, really invigorated by the pace rather than being drawn down by it."