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From: "Gary Johnson" <gjohnson144@comcast.net>
Date: May 11, 2015 at 3:43:30 PM CDT
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: Remembering Endeavour's Maiden Voyage

 

 

AmericaSpace

For a nation that explores
May 9th, 2015

'Where We Either Succeeded or Failed': Remembering Shuttle Endeavour's Maiden Voyage (Part 1)

By Ben Evans

 

In the first, and so far only, three-person EVA, astronauts Rick Hieb, Tom Akers and Pierre Thuot manhandle Intelsat 603 into Endeavour's payload bay for the attachment of a new rocket motor. Photo Credit: NASA

"Ready. Ready. Grab!"

The words of Rick Hieb echoed through the silent Mission Control Center (MCC) at the Johnson Space Center (JSC) in Houston, Texas.

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 telecommunications satellite, delivered into an improper orbit by a Commercial Titan III 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 603 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 Russia's Svetlana Savitskaya and NASA's 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 the Hubble Space Telescope (HST) in December 1993.

Proudly demonstrative of her nautical and exploratory heritage through Captain James Cook's vessel, and bearing the colors of the elementary and secondary schools which named her, Endeavour's first patch is bordered by the names of her first seven astronauts: Commander Dan Brandenstein, Pilot Kevin Chilton, and Mission Specialists Rick Hieb, Bruce Melnick, Pierre Thuot, Kathy "K.T." Thornton, and Tom Akers. Image Credit: NASA

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 603 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. In his memoir, Riding Rockets, fellow STS-36 astronaut 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."

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 603, 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 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.

Intelsat 603 floats in space during rendezvous activities with Endeavour. Photo Credit: NASA

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 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 the shuttle to reboost Intelsat 603. Two possible scenarios 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 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."

Pictured in front of Endeavour, the STS-49 crew conducted one of the most dramatic shuttle missions in history. From left to right: Kathy "K.T." Thornton, Bruce Melnick, Pierre Thuot, Dan Brandenstein, Kevin Chilton, Tom Akers, and Rick Hieb. Photo Credit: NASA

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 (JSC) 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 (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 1986, 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.

Named in honor of Captain James Cook's vessel, it was obvious from the outset that Space Shuttle Endeavour would open new horizons…and so she did. Photo Credit: NASA

Three finalists were eventually announced by the judges and by NASA 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, Miss. (Division I, elementary) and Tallulah Falls, Ga. (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 (KSC) 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 cannibalization of parts during Endeavour's construction to address hydrogen-leakage 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 (ET) 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 (APUs) 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 25-mission career.

Endeavour's engines roar to life for the last Flight Readiness Firing (FRF) of the shuttle era. Photo Credit: NASA

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 ET umbilical and the Solid Rocket Boosters' (SRBs) 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, although a second FRF for Endeavour was not considered necessary.

Her next big test would be to launch.

 

Copyright © 2015 AmericaSpace - All Rights Reserved

 

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AmericaSpace

For a nation that explores
May 10th, 2015

'Big Mental Switch': Remembering Shuttle Endeavour's Maiden Voyage (Part 2)

By Ben Evans

 

With the possible exception of Columbia and the very first space shuttle mission, few orbiters had as dramatic and exciting a maiden voyage as Endeavour. On STS-49, she provided a reliable stage for the longest EVA in history and the first three-man EVA in history. Despite the trials and tribulations of the flight, she performed admirably. It was a characteristic which would serve Endeavour well throughout her 25-mission career. Photo Credit: NASA

More than two decades ago, on 7 May 1992, the last virgin space shuttle speared for the heavens. Orbiter Vehicle (OV)-105, better known as "Endeavour," had arisen from a set of structural spares and had been assembled to replace her late sister, Challenger. With the possible exception of Columbia—which flew the very first shuttle mission in April 1981—there is perhaps no other orbiter than Endeavour which made her entrance on-stage in such a dramatic manner. Her first flight would rendezvous, retrieve, and deploy the stranded Intelsat 603 communications satellite and, for the first time, would involve as many as three EVAs, featuring no fewer than four astronauts. As circumstances would transpire, Endeavour would break even that record on STS-49 … and would continue to break records for the rest of her 25-flight career.

Originally scheduled for the evening of 4 May 1992, the launch of STS-49 was postponed until the 7th in order to permit greater conditions of daylight for photographic coverage of the ascent. After a 34-minute delay, caused by marginal weather conditions at one of the Transoceanic Abort Landing (TAL) sites, STS-49 duly thundered into space at 7:40 p.m. EDT on 7 May, and during the next couple of days Intelsat controllers maneuvered their satellite into a "control box," some six degrees of arc of the shuttle's orbit. These maneuvers also served to reduce Intelsat's rotation from 10.5 to around 0.65 rpm. By the 10th, as they approached to within 8 miles (13 km) of the satellite, Thuot and Hieb completed their procedures of suiting-up and were assisted into the airlock by crewmate Akers. Shortly thereafter, at 4:25 p.m. EDT, they opened Endeavour's outer hatch into the payload bay—then in the pitch black of orbital darkness—and Thuot fastened himself into a foot restraint on the end of the Remote Manipulator System (RMS) mechanical arm, deftly operated by veteran astronaut Bruce Melnick. Drawing closer toward the satellite, Thuot extended the capture bar into position, but the latches failed to latch.

He tried again, without success.

A third attempt was similarly fruitless.

From his station on Endeavour's aft flight deck, Brandenstein noticed that Intelsat 603 was beginning to oscillate and drift somewhat, "so I got in my chase-it mode, because I had to keep him aligned." When Thuot's third attempt failed, Brandenstein had used a "tremendous" amount of propellant and instinctively knew that the chances of success were slim at best. The RMS exacerbated the difficulty, because its joints were being driven into positions which they could not support. "We decided, though consultations with the ground, to get out of there and try another day," Brandenstein recollected. "That was a pretty low point, because when we left, it had a pretty good rate. We thought we'd lost this $150 million satellite … and Pierre was particularly depressed because, obviously, he thought it was his fault."

Spectacular liftoff for Endeavour on her maiden voyage. Photo Credit: NASA

Thuot and Hieb returned inside Endeavour after three hours and 43 minutes, and later that evening Hughes engineers confirmed that they had managed to stabilize Intelsat. Next day, at 4:30 p.m. EDT on 11 May, the spacewalkers were back outside for a second attempt. "Instead of doing it at night, we were going to wait and do it in daylight," Brandenstein said. "We decided we weren't going to even make an attempt until everything was just perfect. Pierre went in and the rotation slowed down." From Hieb's position, it looked as if Thuot had completed the capture, but, alas, the satellite again began to oscillate. The astronaut's alignment was unquestionably correct, but the capture bar—described in yesterday's AmericaSpace history article—refused to seat itself properly and Intelsat wobbled. A few weeks after the mission, Thuot explained to this author that the satellite "was much more dynamic than our training had led us to believe."

As the disappointed spacewalkers returned inside the cabin for the second time—this time after 5.5 hours—they at least knew that the Hughes engineers could regain control of Intelsat 603 for another attempt. However, although propellant reserves allowed for it, three separate rendezvous on a single shuttle mission had never been attempted, and Brandenstein recommended a day off to plan for the third attempt. In an interview for the Smithsonian, Rick Hieb remembered that the evening of the 11th was a sombre time. At one point, Kevin Chilton, the STS-49 pilot and the only "rookie" member of the crew, joined Hieb on the flight deck and the pair entered an impromptu brainstorming session. It was a session that would mark a significant turnaround in the fortunes of a mission which seemed snake-bitten.

As Hieb and Chilton talked, other members of the crew floated upstairs to join them. The main concern was where to manually grab Intelsat. The top of the satellite, where the delicate antennas were located, was not ideal, and it was Bruce Melnick who suggested an EVA with not two spacewalkers, but three. No excursion in history had ever involved more than two members, partly due to safety concerns and partly because of the sheer practicality of getting three people into the tiny airlock. On the other hand, Endeavour carried four suits for Thuot, Hieb, Thornton, and Akers, so in theory it was a possibility.

"When Bruce said that," recalled Hieb, "a big mental switch flipped over, at least for me. In my mind, having a third set of hands out there meant that we would be successful, although we weren't yet sure how."

Mission Control knew that the astronauts were still awake, because Endeavour's monitors had not been turned off. At length, the crew turned them off and continued talking in the dark, but eventually called the ground with Melnick's idea. Years later, Brandenstein remembered that it was Chilton who sketched out the practicalities of the three-person EVA scenario and held it in front of the television camera to allow mission controllers to see it. "The big choke point," Brandenstein said, "was can you put three people in the airlock to get them outside?" In the Houston water tank, fellow astronauts Story Musgrave, Jim Voss, and Michael "Rich" Clifford donned suits and demonstrated the techniques and geometries involved in setting themselves up to accomplish the feat.

Armed with the capture bar mechanism, Pierre Thuot provides a measure of scale of the enormous size of Intelsat 603. Photo Credit: NASA

Their consensus: It was doable. On the evening of 12 May, Capcom Charles "Sam" Gemar radioed Mission Control's approval to the crew.

Late on 13 May, the third attempt got underway. Truss members belonging to the Assembly of Station by EVA Methods (ASEM)—a Space Station Freedom demonstration payload, to be used during EVA tests later in the mission—were removed and arranged into a triangular structure for Thuot, Hieb, and Akers to anchor their feet. Brandenstein positioned the orbiter directly beneath Intelsat 603, and controllers verified that its surface temperatures would not exceed the 160 degrees Celsius (320 degrees Fahrenheit) touch limit of the astronauts' gloves. With Hieb close to the starboard payload bay wall, Akers in the center, attached to an ASEM strut, and Thuot on the end of the RMS on the port side, the astronauts could do little but watch as Endeavour drew closer. They studied its slow rotation for about 15 minutes, until, on Hieb's call, they moved in for the capture.

All at once, Thuot spotted a slight wobble. He called the attempt off.

Shortly thereafter, they tried again. This time, at last, the three men grabbed the satellite and held it firmly. The time was 7:55 p.m. EDT. "I actually thought the other two guys had stopped it from rotating," Thuot said later, "so little force had I applied. Very gently, the thing came to a stop." From the flight deck, Dan Brandenstein asked them if they had a good grasp. On Thuot's response in the affirmative, the commander was able to advise ground controllers, with more than a hint of relief: "Houston, I think we've got a satellite!"

With Intelsat snared, the astronauts removed the steering wheel and installed an extension to the capture bar, which Melnick grappled using the RMS. The satellite was then positioned above its 23,000-pound (10,430-kg) Orbus-21 solid-fueled perigee kick motor, which sat vertically in its cradle. After closing four docking clamps to secure the pair, and attaching two electrical umbilicals between Intelsat and the motor itself, the spacewalkers set a pair of deployment timers and retreated to Endeavour's airlock. Meanwhile, Kathy Thornton prepared to activate the springs to deploy the payload. At first, it did not move. "They had made a change in the wiring of the deploy system," recalled Brandenstein, "and the change never made it through the process [and] never got into the checklist. Fortunately, somebody in Mission Control apparently knew about it. They just quick called up a different switch sequence and she did that sequence and it went." Deployment occurred at 12:53 a.m. EDT on 14 May, and the satellite vacated the payload bay. Less than an hour later, the three spacewalkers repressurized the airlock and returned inside the cabin.

In the first, and so far only, three-person EVA, astronauts Rick Hieb, Tom Akers, and Pierre Thuot manhandle Intelsat 603 into Endeavour's payload bay for the attachment of a new rocket motor. Photo Credit: NASA

Speaking a decade or more after the flight, Dan Brandenstein regarded those few days of STS-49 as "one of those missions from hell," and for newly-appointed NASA Administrator Dan Goldin it was truly "a baptism of fire." Nevertheless, at 1:25 p.m. EDT on the following day, 15 May, Intelsat 603's new motor ignited perfectly, and it was on-station in geosynchronous orbit by the 21st. As well as becoming the first shuttle crew to accomplish as many as three EVAs in a single mission—a record which they would break with a fourth excursion—the triumphant three-man spacewalk established itself as the longest in history. Their eight hours and 29 minutes outside would remain unbroken until March 2001. By now, the difficulties had prompted the Mission Management Team (MMT) to extend STS-49 by 48 hours from its planned seven-day duration. On 14 May, a record-breaking fourth EVA got underway when Akers and Kathy Thornton ventured outside for the ASEM station tests. Originally scheduled to involve two EVAs—one by Thornton and Akers and the second by Thuot and Hieb—the Intelsat 603 retrieval forced the cancellation of one spacewalk.

Activities included the construction of a pyramid-shaped truss, the unberthing of a Mission-Peculiar Equipment Support Structure (MPESS)—maneuverd by the RMS—and efforts to evaluate the ability of spacewalkers to work at positions "above" and "forward" of the payload bay, including "over the nose" of the shuttle. The MPESS contained two node boxes for the pyramid, a releasable grapple fixture and interface plate, and a truss leg and strut dispenser. Five crew rescue techniques were to be trialed, including a lasso-like "astro-rope," a seven-section telescoping pole and a hand-held propulsive device. The latter, according to NASA's STS-49 press kit, was "a redesigned hand-held maneuvering unit from the Skylab program," in which pressurized nitrogen jets were employed as thrusters.

During their seven hours and 43 minutes in the payload bay, Thornton and Akers completed the construction and disassembly of the ASEM attachment fixture, tested the propulsive device, affixed six of eight legs onto the MPESS, and, unexpectedly, were called upon to manually stow Endeavour's Ku-band antenna, which had experienced a positioning motor failure. According to NASA's post-mission report, this EVA was planned to be RMS-intensive, although the mechanical arm was used to accomplish only a single ASEM task and the spacewalkers' timeline was further impacted by the Ku-band activity.

Returning inside Endeavour's airlock after the excursion, the astronauts of STS-49 could now boast four EVAs—lasting a cumulative of 25 hours and 27 minutes—which had snatched success from the fangs of defeat. The physical appearance of the four spacewalkers in their snow-white suits was also quite distinct from previous missions, all of which had featured no more than two members. In order to distinguish them, Thuot (designated "EV1") wore red stripes around his suit legs, whilst Hieb (EV2) wore a pure-white suit, and, for the first time, Thornton (EV3) wore dashed stripes around her suit legs and Akers (EV4) wore red diagonal hatches around his suit legs. In spite of the remarkable achievement of performing four back-to-back EVAs on a single mission, only relatively minor glitches plagued the spacewalkers—a failed joint on one of the portable foot restraints, a loud noise over the headsets when power tools were being used, and a battery problem, among others—and their suits held up exceptionally well.

The shuttle's first drag chute blossoms from Endeavour during rollout on 16 May 1992. Photo Credit: NASA

Endeavour's return to Earth on 16 May 1992, concluding her first flight in a 25-voyage career, brought with it a number of test objectives, the most visible of which was the deployment of the shuttle's long-awaited drag chute on the runway. Measuring 39 feet (11.8 meters) in diameter when fully unfurled, the chute was designed to reduce steering problems and relieve stress on the shuttle's brakes and tires, which had suffered particularly significant damage on Mission 51D in April 1985. In the post-Challenger era, options to improve landing safety were extensively evaluated. As well as the drag chute, options included the emplacement of an arresting barrier at the end of the runway or the installation of a special "skid" on the landing gear. In the event of a blown tire, the latter was meant to preclude the chance of a second tyre failing, effectively providing a "roll-on-rim" capability for a predictable rollout pattern.

Design requirements for the drag chute—which was tested extensively at NASA's Dryden Flight Research Center at Edwards Air Force Base, Calif.—included an ability to bring an orbiter to a halt in less than 8,200 feet (2,500 meters) with an 11-mile (17.7-km) tail wind and maximum braking at a ground speed of 160 mph (257 km/h). Housed in a cylindrical container, just beneath the shuttle's vertical stabilizer fin, the chute was to be manually deployed by the pilot after main gear touchdown and ahead of nose gear touchdown. It would then be jettisoned when the rollout speed had dropped to around 70 mph (110 km/h). During re-entry, the orbiter's main engines were repositioned some 10 degrees "lower" than normal, in order to eliminate the chance of damage to the chute.

Air trials at Dryden in the summer of 1990 saw it fitted to a modified NB-52 carrier aircraft—piloted by former astronaut Gordon Fullerton—which tested it at landing speeds of between 160-230 mph (257-370 km/h), with no negative effects. These trials enabled engineers to predict that it would reduce the shuttle's landing rollout distance by some 1,000-2,000 feet (300-600 meters). Early in January of the following year, NASA modified its production contract for Endeavour with Rockwell International by $33.3 million to include the design, fabrication, and installation of the chute. Since STS-49 was to be its the first space mission, plans called for it to be deployed after all six wheels—main gear and nose—were firmly on the runway. After an uneventful re-entry, Endeavour's main gear touched concrete Runway 22 at Edwards, at 1:57 p.m. PDT (4:57 p.m. EDT), followed by the nose a few seconds later.

Then came the chute.

The crew pose triumphantly in front of Endeavour at Edwards Air Force Base, Calif., on 16 May 1992. Photo Credit: NASA

At the pilots' command, pyrotechnics blew the door away from the chute compartment and a mortar fired, driving out firstly a 10-foot pilot chute, then the main canopy, which "reefed" to 40 percent of its total diameter for a few seconds to lessen the initial structural loads on Endeavour herself. It trailed the orbiter by 89 feet (27 meters) on a 41-foot (12.4-meter) riser. Following the successful operational of the reefing line cutter, the chute blossomed to its fully inflated condition. Photographic analysis of the landing illustrated that the reefed chute rode at a higher angle than anticipated and the door trajectory differed slightly from the NB-52 tests; additionally, its behavior and closeness to the centerline were attributed to the effect of the aerodynamic flow for the fully-open speed brake.

Summing up his fourth and final shuttle mission—for he would retire from NASA in October 1992—Dan Brandenstein was happy with Endeavour's performance on her maiden voyage. This was particularly important in view of the Intelsat 603 difficulties and the relative paucity of additional time to tend to systems glitches. "They built a beautiful vehicle," he said, "because it's based on all the other things that diverted our attention on that flight. It was really nice that Endeavour performed like an old pro." Indeed, NASA's official post-mission report highlighted only 36 anomalies, none of which were of sufficient concern to impact the successful conduct of the mission.

In the aftermath of STS-49, the crew themselves would highlight the fact that their mission raised awareness of the need for more EVA experience in the years before the start of construction of Space Station Freedom. At one stage, in the late 1980s, as many as four EVAs per week were envisaged—an astonishing estimate which NASA Administrator Dick Truly deemed totally unacceptable. Yet as the plans for the station matured, it was obvious that the construction process would be EVA-intensive and that required different ways of working and training. "We have to take a good look at the time it takes to do a job," Brandenstein said. "We need better ways to train so that the learning curve isn't quite so steep." Pierre Thuot added that the Intelsat 603 retrieval task was something that the crew "couldn't train for fully."

After their return from STS-49, Kathy Thornton and Tom Akers—who would go on to service the Hubble Space Telescope (HST) together in December 1993—took an active role in developing new EVA methods in the Weightless Environment Training Facility (WET-F) in Houston. "Even in the tank, you still have the resistance of water," Dan Brandenstein recalled, "so you can kick your feet and swim. In zero gravity, we've got movies of Tom going to that instinct. You can see him kicking his legs and nothing's happening. Also, if you move something in the water, as soon as you stop moving it, the reason is the water stops it. But in zero gravity, you start moving something and it just keeps moving until you come back on it. They made some significant chances in the tank training procedures." The first flight of Endeavour's career had gone spectacularly well and had played a significant role in shaping the missions—and the assembly of the space station—which would follow.

 

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