“Ready. Ready. Grab!”
The words of Rick Hieb echoed through the silent Mission Control Center.
The view through Space Shuttle Endeavour’s aft flight deck windows on the evening of 13 May 1992 was quite different from anything ever seen before. Not only was this the maiden voyage of NASA’s newest orbiter—a vehicle which, but for the loss of Challenger, might have remained a set of structural spares—but it also involved the first EVA with as many as three people. This mission, STS-49, commanded by Chief Astronaut Dan Brandenstein, had long been anticipated to be the most visible shuttle flight of 1992, but it demonstrated that human space flight retains the ability to deliver unexpected surprise. When the crew was announced, their mandate was to retrieve the Intelsat 603 communications satellite, delivered into an improper orbit by a Commercial Titan booster in March 1990. Spacewalkers Hieb and Pierre Thuot would venture into Endeavour’s payload bay to attach a new rocket motor, after which Intelsat would be boosted into its 22,000-mile (35,000-km) geosynchronous orbit, ahead of its pivotal role in covering the 1992 Summer Olympics in Barcelona.
After the Intelsat activities, a further two spacewalks—the first with Kathy Thornton and Tom Akers, the second with Thuot and Hieb—would rehearse Space Station Freedom construction techniques. Thornton’s inclusion made her only the third woman, after Svetlana Savitskaya and Kathy Sullivan, to perform an EVA. It was a role for which she had previously trained in preparation for her first shuttle mission, STS-33, in November 1989. “I absolutely insisted that she be the EVA person,” her STS-33 commander, Fred Gregory, later recalled in his NASA oral history, “over great protest … If we had not insisted, probably a person of her size would never have done something like this. Kathy [Sullivan] was a larger woman who could fit into the suits … but Kathy Thornton was not, so we really had to force the issue.” Doubtless, Dan Brandenstein was in full agreement that Thornton—nicknamed “K.T.” in the Astronaut Office—was the most appropriate choice. She would go on to fly as part of the EVA team which first serviced Hubble in December 1993.
The other three astronauts involved in the STS-49 EVAs were male. Rick Hieb was already in training to fly STS-39 at the time the Intelsat crew was assembled in December 1990, and Tom Akers had returned only weeks earlier from the Ulysses deployment mission, STS-41. The man in charge of the team—designated “EV1” and wearing red stripes around the legs of his pure-white space suit for identification—was Pierre Thuot, nicknamed “Pepe.” When he flew STS-36 in the spring of 1990, Thuot became the first of his class to be assigned a mission and the first to actually fly. Mike Mullane remembered Thuot as a fast mover and a fast thinker. “Pepe was a 24-volt guy in a 12-volt world,” he wrote. “He reminded me of a hummingbird in the way he darted at whatever he was doing, whether he was turning the page of a checklist, punching in a phone number or flipping cockpit switches.” From a personal perspective, as a teenager, I contacted Thuot to ask him about his career. One comment in particular stood out and proved illustrative of his work ethic. “Whatever you do in life,” he told me, “always make sure that you enjoy what you’re doing and aim high. Pick challenging goals and work hard to achieve them.”
If everything ran as timelined, STS-49 would thus be the first shuttle flight to feature as many as three spacewalks and include two teams of spacewalkers; both of which were critical prerequisites if NASA was to execute as many as five EVAs per mission to service Hubble and build Space Station Freedom. On the face of it, retrieving and repairing Intelsat, for all its drama, offered something of a backward glance to the shuttle’s pre-Challenger heyday and was unusual, for in the wake of the disaster it had been mandated that the reusable orbiters would henceforth not be used for commercial missions. STS-49 was thus the last of its kind. At the same time, as Space Shuttle Program Director Bob Crippen explained in June 1990, it offered “an opportunity for expanding our experience base in the planning, training and performance of EVA” by “helping preparations for Freedom.”
Others agreed that such a mission was useful for other purposes. It was “a throwback to the good old days,” said Endeavour’s first processing manager, John Talone, “when we used to go out and do these kinds of things.” Added NASA’s Associate Administrator for Space Flight, former astronaut Bill Lenoir: “It’s a mission we wanted to do. It gave me the opportunity to have real work that really mattered; that was going to get measured, where we either succeeded or failed.”
The Intelsat 6 series represented the eighth generation of communications satellites, designed by Hughes for the International Telecommunications Satellite Organisation—originally an inter-governmental consortium, but since July 2001 a private company, known as Intelsat, Ltd.—which were capable of providing 33,000 telephone circuits and four television channels. Five were built between 1983 and 1991, and a half-scale model of the satellite today resides in the lobby of Intelsat’s Washington, D.C., headquarters. The 9,200-pound (4,170-kg) cylindrical satellites were spin-stabilized at 30 revolutions per minute, with a “de-spun” segment to house the communications payload and direct it toward a desired location on Earth. Originally scheduled to be flown aboard the European Ariane 4 booster and, in the pre-Challenger era, also the shuttle, Intelsat 6 was a wide-body satellite, measuring 11.8 feet (3.6 meters) in diameter and 17 feet (5.2 meters) tall, expanding to a height of 38.4 feet (11.7 meters) when its concentric solar arrays and communications payload were fully operational in geosynchronous orbit.
These huge satellites were fed by a twin-propellant system of nitrogen tetroxide and monomethyl hydrazine, which fed radial and axial thrusters for station-keeping and attitude control. The outer surfaces of the satellites were coated with photovoltaic solar cells, which provided around 2,600 watts of electrical power, whilst nickel-hydrogen pressure vessel batteries supported operations whilst in Earth’s eclipse. The communications payload carried 38 C-band and 10 Ku-band transponders. The third Intelsat 6—codenamed “603”—was launched atop a Commercial Titan III from Cape Canaveral Air Force Station in Florida on 14 March 1990, but the rocket’s second stage failed to separate properly and the satellite could only be released by means of jettisoning its attached Orbus-21 perigee kick motor. This left it effectively unable to achieve geosynchronous altitude, and the $157 million Intelsat—which had not been insured, but was “self-insured” with the company’s own funds—was left stranded in an inoperable low-Earth orbit.
In the weeks and months following the malfunction, Hughes entered into a contract with NASA, worth in excess of $90 million, for a shuttle flight to reboost Intelsat 603. Two possible options quickly gained prominence: either to carry a new perigee kick motor into orbit and attach it to the satellite to reboost it into geosynchronous transfer orbit or retrieve Intelsat and bring it back to Earth for refurbishment. Concerns about the extent to which the satellite’s surfaces might degrade over two years were allayed by the test flight of several solar array sample “coupons,” attached to Discovery’s Remote Manipulator System (RMS) mechanical arm during the STS-41 mission in October 1990. These were exposed to the harsh atomic oxygen environment for a minimum of 23 hours, with few ill-effects. Two months later, in December, the STS-49 crew was named to conduct the audacious salvage.
Dan Brandenstein found himself in command of the first flight of a new space shuttle and a rendezvous and retrieval mission with EVAs which promised to be filled with drama. “One of my first concerns when we first got assigned and started working with Hughes on the mission,” he told the NASA oral historian, “was if we try and grab it, if we bump it, is it going to go out of whack and float away? Part of the requirements from the customer were that we didn’t touch any sensitive area, which left you a very small ring that … had a limited accessibility and that was supposed to the way we grabbed it.”
The mechanism by which Thuot and Hieb would grab Intelsat was a so-called “capture bar,” designed and built by engineers in the Crew and Thermal Systems Division at NASA’s Johnson Space Center in Houston, Texas. Weighing 160 pounds (73 kg), it measured 15 feet (4.6 meters) long by about 3.3 feet (1 meter) wide and included detachable beam extensions and a steering wheel. As Thuot rode on the end of Endeavour’s RMS arm, he would be positioned close to the base of Intelsat 603 and after grappling it would lower it delicately into a Hughes-built cradle assembly. “There was a lot of analysis done,” continued Brandenstein, “and we were assured that because it was spinning slightly and it had a lot of mass, we could bump it and it would stay pretty much in place and wasn’t going to be a problem.” Throughout 1991 Thuot and Hieb trained underwater and on the air-bearing table, to such an extent that they could follow the procedure with their eyes closed.
Endeavour arose from a series of already extant shuttle spares, assembled before the loss of Challenger to facilitate repairs or possibly the creation of a new vehicle in the event of an accident. The $389 million contract to build the spares—which consisted of an aft-fuselage, a mid-fuselage, two halves of the forward fuselage, a vertical stabiliser and rudder, wings, elevons, and an aft body flap—was awarded to the shuttle’s prime contractor, Rockwell International, in April 1983. Three years later, the destruction of Challenger added a new level of urgency to these plans and led directly to a decision to assemble the spares into a new craft, designated Orbiter Vehicle-105 (OV-105). However, several powerful political voices opposed the idea. The White House’s Chief of Staff Donald Regan and several members of Congress argued that the cost of developing the spares into a new shuttle could be better spent on an entirely new spacecraft. Nevertheless, in September, the construction of OV-105 was approved, and in July 1987 NASA awarded a $1.3 billion contract to Rockwell. Construction was completed within three years, and the orbiter was formally powered-up to begin systems testing on 6 July 1990.
By this time, OV-105 had received the name “Endeavour.” It was spelt in the English fashion, since it paid homage to Captain James Cook, whose own vessel, HMS Endeavour, had sailed to the South Pacific in 1768-71 to observe the transit of Venus, part of ongoing scientific investigations to measure the distance between Earth and the Sun. During the course of the voyage, Cook reached Tahiti and Hawaii, charted New Zealand for the first time, and surveyed the eastern coast of Australia.
In response to the tremendous outpouring of student grief in the wake of Challenger, Republican Congressman Tom Lewis of Florida initiated a resolution to enable students to name the new orbiter. Lewis’ bill, passed in Congress in October 1987, inaugurated the “NASA Orbiter Naming Program.” More than 71,000 students, representing 6,154 schools across the United States, submitted their entries during the course of 1988. The guidelines dictated that the name must have previously belonged to an exploratory or research vessel, that it must be “appropriate” for the new shuttle, that it must capture the spirit of America’s mission in space, and that it should be easy to pronounce for radio transmission.
Three finalists were eventually announced by the judges and by NASA’s Educational Programs Officer Muriel Thorne: Endeavour, Horizon, and North Star. Of these, Endeavour was by far the most popular entry, accounting for almost a third of all state-level winners in the competition, and in May 1989 the new orbiter was formally named by President George H.W. Bush. When the STS-49 crew came to design their crew patch, they not only included Captain Cook’s Endeavour … but also exhibited the colours of the two winning schools—Senatobia, Mississippi (Division I, elementary) and Tallulah Falls, Georgia (Division II, secondary)—atop the ship’s masts.
Less than two years after Bush named Endeavour, on 25 April 1991, the sparkling new shuttle was rolled out of Rockwell’s Palmdale facility in California and was delivered to the Kennedy Space Center in Florida on 7 May. Her targeted maiden launch in May of the following year quickly became mired with difficulty, as “hundreds of problems” were identified by NASA: faulty cables and connectors, contaminated propellant lines, incorrectly fitted insulation blankets, and even a biscuit, mistakenly dropped in the fuselage. At their worst, in the late summer of 1991, up to 70 electronic, hydraulic, or mechanical problems were being reported each week, prompting NASA to announce that it expected to delay STS-49 from May until at least July 1992. The cannibalisation of parts during Endeavour’s construction to address hydrogen-leak problems with her sister ships Columbia and Atlantis compounded the delay. Then, in March 1991, cracks in Discovery’s 17-inch (43-cm) External Tank disconnect doors prompted inspections of Endeavour and uncovered a similar flaw. However, it was subsequently revealed that these cracks represented an inherent design error, rather than a result of poor manufacturing.
With these problems in mind, it is quite remarkable that the anticipated delay to STS-49 did not transpire, and she was rolled out to Pad 39B on 13 March 1992 to begin final preparations for launch. In physical appearance, Endeavour differed very little, outwardly, from her sister ships. Internally, though, she carried Advanced General Purpose Computers, with twice as much memory and three times as much processing speed as the older versions, as well as being smaller, lighter (at just 64 pounds or 29 kg), and requiring less power (around 550 watts). The High-Accuracy Inertial Navigation System was intended to eventually replace earlier inertial measurement units, with one HAINS flying alongside two of the older devices on STS-49. Endeavour was also fitted with three improved Tactical Air Navigation systems, a pair of enhanced Master Events Controllers, and solid-state trackers. Her Auxiliary Power Units were enhanced over previous models, as were her gas generators, fuel pumps, redundant seals, and new materials.
Many of these upgrades were designed to be more reliable than earlier systems, utilising lower power and requiring far less maintenance. She also featured a new drag chute to improve landing safety and was fitted with the plumbing and electrical connections to enable Extended Duration Orbiter (EDO) missions of up to 28 days. A fifth cryogenic oxygen tank and a fifth hydrogen tank beneath her payload bay floor supported this provision. “On the rest of the orbiter fleet,” noted a NASA release, “Columbia also has five tank pairs and Atlantis and Discovery each have four tank sets.” Although the official plans at the time called for Columbia alone to fly EDO missions, Endeavour would perform one such flight, lasting almost 17 days, later in her career.
Three weeks after rollout to the pad, on 6 April, her three main engines underwent the standard Flight Readiness Firing (FRF). This test firing had historically been performed before each orbiter’s maiden voyage to demonstrate the engines’ capability to throttle and gimbal as they would during flight. Preparations for the FRF proceeded in a manner not unlike a real countdown:
“T-minus 12, 11, 10, nine … we have a Go for engine start … ”
At four seconds, Endeavour’s engines roared to life at 120-millisecond intervals, reaching 90 percent of their rated thrust and hitting the 100-percent mark precisely at T-zero.
“ … two, one, zero … ”
The shuttle visibly flexed, as if she ached to break free of her shackles and climb, crewless, toward the heavens.
“ … engines are now at 100 percent of rated power … ”
And so they were. Vast clouds of steam billowed from the pad. Three seconds later, engineers simulated the retraction of the External Tank umbilical and the Solid Rocket Boosters’ hold-down posts, and after a further 15 seconds of stable thrust, shutdown commands were issued to all three engines. In total, the FRF lasted 22 seconds and was a great success, but for a couple of technical issues. High vibration levels were detected in one of the engines’ high-pressure liquid oxygen turbopumps, whilst another exhibited a loud “popping” noise shortly after shutdown, indicative of hydrogen ingestion into the fuel injector. Prudently, on 8 April NASA decided to replace all three engines with a set previously earmarked for Atlantis’ STS-46 mission in July, although a second FRF for Endeavour was not considered necessary.
Her next big test would be to launch.
The second part of this article will appear tomorrow.
Missions » ISS »