Monday, June 24, 2013

Fwd: A Legacy of Women in Space: Twenty Years Since STS-57



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From: "Gary Johnson" <gjohnson144@comcast.net>
Date: June 24, 2013 11:35:56 AM GMT-06:00
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: A Legacy of Women in Space: Twenty Years Since STS-57

 

AmericaSpace

AmericaSpace

For a nation that explores
June 22nd, 2013

A Legacy of Women in Space: Twenty Years Since STS-57 (Part 1)

By Ben Evans

 

Joined by Pilot Brian Duffy, STS-57 Mission Specialists Janice Voss (left) and Nancy Sherlock made history on the flight. For the first time, a civilian woman and a military woman served together aboard the same space mission. Photo Credit: NASA

Joined by Pilot Brian Duffy, STS-57 Mission Specialists Janice Voss (left) and Nancy Sherlock made history on the flight. For the first time, a civilian woman and a military woman served together aboard the same space mission. Photo Credit: NASA

Fifty years ago this month, the first woman ventured into space. Thirty years ago, also this month, the first U.S. woman ventured into space. And twenty years ago this very week, two women from different backgrounds—one a U.S. Army aviator, the other a civilian engineer—flew together into space for the first time. STS-57 was not the first mission in history to include two female members. Nor was it the first mission to feature a military woman among its crew. However, with the presence of both civilian and military women aboard Endeavour when she rocketed into orbit on 21 June 1993, it offered a reminder of how far women astronauts had advanced in a mere handful of decades.

This relatively minor historic footnote was scarcely noticed at the time, for STS-57 was dominated by an all-new commercial scientific laboratory and the retrieval of a European free-flying satellite. The names of Janice Voss and Nancy Sherlock (today Currie) represented just two more female spacefarers, seemingly lost in a sea of astronauts and an ocean of shuttle missions. Yet both went on to carve remarkable careers at NASA. Voss went on to fly five times, including STS-83 and STS-94 in April and July 1997, which marked the only occasion in shuttle history on which the same crew launched twice to complete the same mission. Currie flew four times, including STS-88 in December 1998, the first International Space Station assembly mission. But it was STS-57 on which both women cut their teeth in low-Earth orbit.

With the surnames of the six crew members emblazoned around "walls" of the Spacehab module, it was no accident that the STS-57 patch was shaped for its primary payload. Image Credit: NASA

With the surnames of the six crew members emblazoned around the "walls" of the Spacehab module, it was no accident that the STS-57 patch was shaped for its primary payload. Image Credit: NASA

Like so many shuttle missions, preparations and processing began several years ahead of launch, but in the late spring of 1993 an unusual cargo was loaded aboard Endeavour for STS-57. Known as "Spacehab," it was a small, flat-roofed laboratory and occupied barely a quarter of the shuttle's payload bay. It was designed and built not by governments, but by private enterprise. Its truncated-cone configuration was immortalized by STS-57 Commander Ron Grabe in the shape of the mission's official crew patch. When Spacehab-1 rose from Earth in June 1993, it marked the culmination and realization of a decade-old dream for aerospace engineer Bob Citron, who founded Spacehab, Inc. in 1983 and incorporated it the following year. Since 2009, the company has been known under its present corporate name, Astrotech Corp.

"People often ask me why I started Spacehab," Citron recalled on Astrotech's website, "and my response usually goes something like this: It took a small group of wide-eyed dreamers and determined space enthusiasts who believed we could pull it off. We didn't have a clue about the enormous problems we would encounter and the nearly insurmountable technical, financial, and institutional roadblocks that would stand in our way. Nobody had done anything like this before." The primary goal of Citron—who died from prostate cancer in January 2012—was to create the world's first privately funded company to support human space missions, using the cavernous payload bay of the shuttle as a carrier of commercial pressurized research modules.

The need for such provision was self-evident. In the shuttle's pre-Challenger heyday, more than a dozen missions were planned each year and a primary thrust of the Reagan Administration's 1983 space policy was for the commercial exploitation of the microgravity environment. Already, middeck lockers were being used to carry out experiments in crystal growth and pharmaceutical development, but the limited volume meant that their commercial viability was restricted. The Spacehab module—accessed by a tunnel connected to the middeck airlock hatch—measured 9 feet long, 11 feet high, and 13.5 feet across the width of the payload bay and effectively quadrupled the shuttle's available pressurized working and living envelope. It supplied environmental, electrical, temperature, command, and data provisions and could house a maximum of 61 middeck-sized lockers and up to two large racks, either in "single" or "double" configurations.

After incorporating Spacehab in 1984, Citron admitted that the company was "on the verge of failure on a number of occasions during its first years," until he brought in critical professional management personnel and "things started to happen" through negotiations with NASA, the Italian Alenia Spazio, and German MBB-Erno organizations and Martin Marietta and McDonnell Douglas. By the end of 1985, only weeks before the Challenger tragedy, Spacehab was tentatively scheduled for its first flight in 1987 and a lease of $5 million per mission was quoted by Flight International. Early plans called for the assembly of three modules, but center-of-gravity issues gave NASA cause for concern and threatened to affect the placement of other cargoes in the payload bay.

Ultimately, McDonnell Douglas was selected as the lead contractor and a decision was made to build two flight modules and an engineering test model. Other worries lingered, but in late 1986 Spacehab signed a Space System Development Agreement, in which NASA agreed to fly five inaugural missions. By October 1987, 42 firm requests had been received, with lockers priced at $300,000 for non-government users and $100,000 for government agencies and contractors. The concept was now growing from initial designs into reality. In September 1989, Patent No. 4,867,395 for a "Flat End-Cap Module for Space Transportation System" was awarded to Spacehab, Inc. by the U.S. Patent Office.

The flat-topped Spacehab-1 module is pictured in Endeavour's payload bay, ahead of final close-out for flight. Photo Credit: NASA

The flat-topped Spacehab-1 module is pictured in Endeavour's payload bay, ahead of final close-out for flight. Photo Credit: NASA

Hopes to fly the modules on very early post-Challenger missions received a rude awakening, however, and it was expected to be at least three years after the resumption of shuttle operations before the maiden Spacehab flight could be expected. According to NASA's April 1988 schedule, Spacehab-1 was listed as a primary payload on STS-51 in June 1991, co-manifested with the retrieval of the European Retrievable Carrier (EURECA) and the deployment of Italy's LAGEOS-II satellite. This schedule slipped and, at length, the first module was not unveiled until early 1992 at the custom-built Spacehab Payload Processing Facility (SPPF) at the Kennedy Space Center, Fla. By this time, under the Commercial Middeck Augmentation Module procurement, initiated in February 1990 and formally signed the following December, NASA agreed to lease 200 Spacehab lockers at a cost of $184.2 million. Over the coming years, the SPPF would host more than a hundred astronauts and cosmonauts, enabling them to train on real experiment hardware.

The formal unveiling of Spacehab coincided closely with the assignment of the first crew members for STS-57. The names of Payload Commander David Low and Mission Specialist Janice Voss were announced in February 1992. (It is a tragic coincidence that, like Bob Citron, both astronauts later succumbed to cancer—Low of colon cancer in March 2008 and Voss of breast cancer in February 2012.) Within weeks of their announcement to STS-57, four more astronauts were named to the crew: Commander Ron Grabe, Pilot Brian Duffy, and two further Mission Specialists, Nancy Sherlock and Jeff Wisoff. For Duffy, who was in quarantine at KSC, a few days ahead of his STS-45 mission at the time, it came as a special surprise. "Jeez, I sure hope I like this," he remembered asking himself, "because I just signed up for two of them!" In all seriousness, Duffy appreciated the fact that he would be entering STS-57 training pumped up, fresh, and ready to go. At the time, launch was provisionally scheduled for late in April 1993.

Janice Elaine Voss came from South Bend, Ind., where she was born on 8 October 1956. Space exploration as a possibility first entered her head whilst in the sixth grade, when she read Madeleine L'Engle's novel A Wrinkle in Time; this guided her deeper into science fiction and from thence into science generally. "I just found the whole thing so fascinating," she told the NASA oral historian before her last shuttle mission, "that I've never been interested in doing anything else." Her love of learning was such that, in 1998, with four shuttle missions and a handful of degrees to her credit, she once told a group of pre-teen girls that her next personal goal was to learn the piano.

In high school, she pursued mathematics and science. Later, she earned a degree in engineering from Purdue, whilst working on a NASA co-operative program in computer simulations with the Engineering and Development Directorate at the Johnson Space Center in Houston, Texas. Reflecting on Purdue, Voss was well aware of the fact that the exalted college had produced more astronauts than any other U.S. educational institution, outside of the military academies. After gaining her degree in 1975, she completed a master's qualification in electrical engineering and returned to JSC in 1977 as a crew trainer, teaching re-entry guidance and navigation. Ten years later, she gained her doctorate in aeronautics and astronautics from MIT and worked for a time for Orbital Sciences Corp. Finally, on her fifth application to NASA, she was accepted as an astronaut candidate in January 1990.

Janice Voss translates through the connecting tunnel between Endeavour's middeck and the Spacehab-1 module. Photo Credit: NASA

Janice Voss translates through the connecting tunnel between Endeavour's middeck and the Spacehab-1 module. Photo Credit: NASA

Also selected that year was U.S. Army aviator Nancy Jane Sherlock. Her path to NASA could not have been more different from that of Voss. Born on 29 December 1958 in Wilmington, Del., she admitted that a career in the space program—or even in the uniformed military services—was unthinkable during her childhood. "Women weren't military pilots," she told the NASA oral historian. "Women weren't astronauts. It really wasn't a concrete goal of mine until much later in my life." Having said this, she considered it a surprisingly natural progression to enter the military and pursue an education which ultimately opened professional routes which might previously have been closed to her. Only at the end of her time in high school did the military begin to accept female aviators, and only whilst she was at Ohio State University, studying the biological sciences, did NASA begin to accept female astronauts. Upon receipt of her degree in 1980, she entered the Army with a dream of becoming an aviator and perhaps eventually a military doctor. However, women were gradually being introduced into combat positions and after rotary-wing pilot training she served as an instructor pilot at the Army Aviation Center. Other positions followed—section leader, platoon leader, and brigade flight-standardisation officer—and in 1985 Sherlock earned a master's degree in safety engineering from the University of Southern California.

Eventually, she became a Master Army Aviator and by the end of her military career in 2005 she had logged over 3,900 hours in the air aboard various rotary-wing and fixed-wing aircraft. Years later, she remembered her first day in a helicopter and had the instant thought: This is for me. This is what I want to do. Her decision to pursue a master's in safety engineering is an interesting side note. "When I was in flight school," she explained, "we actually had an accident that killed my instructor pilots and two of the guys that I flew with every day. It was just kind of a strange coincidence that I wasn't in the aircraft. It was at that time that I decided to devote a portion of my career and my academic life to safety engineering." Later, during her NASA life, she went on to earn a doctorate in industrial engineering, with emphasis upon human factors. "Catastrophic things can happen," she reflected, sadly, "due to human error in the cockpit or human error combined with a malfunction in the aircraft."

Sherlock's arrival at JSC came in September 1987 as a flight simulation engineer on the Shuttle Training Aircraft. She had earlier applied unsuccessfully for admission into that year's astronaut candidate class. That same year her daughter Stephanie was born. Three years later she was selected as an astronaut and for the first half of the 1990s until she met her future husband, Davie Currie, she was a single parent. "It was somewhat difficult for a mom to have a lifestyle like that," she said of her early NASA career, "gone an awful lot on travel and studying a lot at home." That study was particularly intense in the months leading up to STS-57, for Sherlock served as the flight engineer, responsible for assisting Commander Grabe and Pilot Duffy with monitoring Endeavour's systems during ascent and re-entry. By the end of her career, she had served as flight engineer on four shuttle missions, more times than any other female astronaut.

All six members of the crew were responsible for aspects of Spacehab-1, which encompassed a wide range of experiments in the life and microgravity sciences. A dozen of these were sponsored by NASA Centers for the Commercial Development of Space and one by the agency's Langley Research Center of Hampton, Va., and many had flown aboard previous missions. The year 1993 was expected to mark a significant watershed for commercial access to space, with a total of 56 research payloads planned aboard Spacehab-1 and, in November, aboard Spacehab-2.

Nancy Sherlock (now Currie) was assigned duties with the Canadian-built RMS robotic arm and as flight engineer on STS-57. She holds the record for having served as a Shuttle flight engineer on more missions (four) than any other woman astronaut. Photo Credit: NASA

Nancy Sherlock (now Currie) was assigned duties with the Canadian-built RMS robotic arm and as flight engineer on STS-57. She holds the record for having served as a shuttle flight engineer on more missions (four) than any other woman astronaut. Photo Credit: NASA

Aboard STS-57, materials science investigations included the Equipment for Controlled Liquid Phase Sintering Experiments (ECLiPSE), developed by the University of Alabama at Huntsville, Ala., which sought to explore "sintering"—a process by which metallic powders are consolidated into metals at temperatures of only 50-75 percent of that needed to melt all the constituent phases—of several metallic composites, with possible applications ranging from stronger, lighter, and more durable materials for bearings, cutting tools, electrical brushes, and contacts. Other areas of research included demonstrations of the feasibility of producing materials for high-speed digital circuits, as well as "zeolites," commonly used in catalysts, molecular sieves, absorbents, and ion-exchange methods, and experiments in gas-permeable polymers and the processing of advanced polymer membranes in support of the commercial membrane industry.

In the life sciences, Astroculture continued a programme of testing the equipment for an operational plant-growth unit. BioServe Space Technologies, based at the University of Colorado in Boulder, provided a pilot laboratory to support various experiments, including the Rhizobium trifolii bacterium, which is known to form symbiotic relationships with Earth-plants, such as alfalfa, clover, and soybean. Such research was expected to lead ultimately to new insights about manipulating the processes responsible for crop infections. Other experimental foci included observations of the growth and development of the E. coli bacterium and studies of gravitational influences upon frogs' kidney cells. BioServe's Commercial Generic Bioprocessing Apparatus supported experiments into biomedical testing and drug development and controlled ecological life-support systems, agricultural development, and manufacture of biological-based materials. These placed emphasis upon the processes by which cells destroy foreign materials and examined the ability of the immune system to respond to infections. Long-term implications for the work included an improved understanding of bone and developmental disorders and the healing of wounds and cancers and other cellular diseases. The development of wasps, seeds, algae, and micro-organisms in the weightless environment was also monitored.

The Organic Separation payload offered the commercial and scientific communities an opportunity to separate cells and particles for analysis, whilst next-generation protein crystal growth equipment employed vapour-diffusion and direct-control methods. Twelve adult male rats were also flown in a pair of Animal Enclosure Modules and were used to evaluate the performance of implanted growth factors. NASA provided a facility to accommodate cell and tissue cultures, a charged particle directional spectrometer, a three-dimensional accelerometer, the Space Acceleration Measurement System, and an experimental life-support apparatus to test water-recycling methods for Space Station Freedom.

A series of Human Factors Assessment studies, mainly performed by orbiter crew members Grabe, Duffy, and Sherlock, involved the collection of data on the astronauts' ease of movement through the middeck-to-Spacehab tunnel, the shuttle's acoustic and lighting environment, and the usefulness of electronic procedures to fulfil tasks. Endeavour's pilots also participated in neutral body posture investigations, sponsored by JSC's Space and Life Sciences Directorate, to observe changes in spinal lengthening and overall posture in the microgravity environment.

By the time the long-delayed STS-55 mission returned to Earth in early May 1993, the Spacehab-1 flight had slipped into early June. However, engineers discovered that one of two springs which keep ball bearings in place in the high-pressure oxygen turbopump of the No. 2 main engine had an improperly-placed inspection stamp, which it was thought might weaken it to the point of breakage. It was considered prudent to replace the turbopump and a firm launch date of the 20th—Brian Duffy's 40th birthday—was established. Grabe had hoped to send his crewmate over the hill in style with an on-time launch, but it was not to be. The countdown proceeded normally until the standard "hold" at T-9 minutes, when weather conditions at all three Transoceanic Abort Landing sites of Banjul in Gambia, Ben Guerir in Morocco, and Moron in Spain, and the Shuttle Landing Facility itself at the Cape, were considered unacceptable to support Endeavour's flight. Nonetheless, a decision was taken to proceed down to T-5 minutes and wait out the weather, but to no avail. Eventually, the 71-minute launch window ran out and the attempt was scrubbed.

Brian Duffy would have to wait another day for launch, but the wait would be worth it.

 

 

Copyright © 2013 AmericaSpace - All Rights Reserved

 

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AmericaSpace

AmericaSpace

For a nation that explores
June 23rd, 2013

A Legacy of Women in Space: Twenty Years Since STS-57 (Part 2)

By Ben Evans

 

With the RMS robotic arm deftly operated by Nancy Sherlock, astronauts David Low and Jeff Wisoff are maneuvered around Endeavour's payload bay. The Spacehab module is clearly visible in the foreground. Photo Credit: NASA

With the RMS robotic arm deftly operated by Nancy Sherlock, astronauts David Low and Jeff Wisoff are maneuvered around Endeavour's payload bay. The Spacehab module is clearly visible in the foreground. Photo Credit: NASA

Fifty years ago this month, the first woman ventured into space. Thirty years ago, also this month, the first U.S. woman ventured into space. And twenty years ago this very week, two women from quite different backgrounds—U.S. Army aviator Nancy Sherlock (now Currie) and civilian engineer Janice Voss—flew together into space for the first time. STS-57 was not the first mission in history to include two female members. Nor was it the first mission to feature a military woman among its crew. However, with the presence of both civilian and military women aboard Endeavour when she rocketed into orbit in June 1993, it offered a reminder of how far women astronauts had advanced in a mere handful of decades.

Rocketing into orbit posed something of a problem on the morning of 20 June, when bad weather at the Transoceanic Abort Landing sites put paid to hopes that Pilot Brian Duffy might celebrate his 40th birthday in style. As described in yesterday's history article, STS-57 was an important mission, carrying the first commercial "Spacehab" research laboratory and destined to recover the European Retrievable Carrier (EURECA) after ten months in orbit. Next morning, the 21st, conditions had improved markedly, but as the six astronauts—Duffy, Sherlock, and Voss, together with fellow crewmates David Low and Jeff Wisoff and Commander Ron Grabe—boarded Endeavour a scratch was observed on the outer seal of the crew access hatch. After consultation with mission managers, it was decided to replace the seal, and this was accomplished with little impact on the countdown.

At T-5 minutes, the hold was extended by 22 seconds in order to shoo an unauthorised aircraft out of the launch danger zone and STS-57 rocketed off the pad at 9:07 a.m. EDT. The ascent was electrifying, particularly for the three "rookie" members of the crew, with Main Engine Cutoff and the onset of weightlessness both memorable. "The bear jumps off your chest," remembered Jeff Wisoff in an interview for the Smithsonian, "and you see your seatbelts float upward, which is kinda cool."

Endeavour rockets into space on 21 June 1993, beginning the first mission to include military and civilian female crew members. Photo Credit: NASA

Endeavour rockets into space on 21 June 1993, beginning the first mission to include military and civilian female crew members. Photo Credit: NASA

Despite initial difficulties, the shuttle's Remote Manipulator System (RMS) mechanical arm was initialized and checked out, in readiness for the retrieval of EURECA on the third day of the flight. A number of thruster firings were performed by Grabe and Duffy over the next 48 hours to effect closure with EURECA, whose orbit had already been lowered under ground command in recent weeks from its operational altitude of 320 miles to more closely approximate Endeavour's altitude of some 190 miles. With Grabe at the shuttle's controls for the final phases of the rendezvous, the satellite was successfully grappled by the RMS, under the deft control of David Low, at 9:53 a.m. on 24 June. Endeavour's Ku-band radar satisfactorily tracked the satellite from a distance of 30 miles to less than 100 feet, with no loss of data. Although EURECA's solar arrays successfully folded up, its two antennas—which should have retracted and latched prior to grappling—failed to close. As a consequence, it was decided to use a portion of Low and Wisoff's planned spacewalk on the 25th to tend to the problem.

An EVA was not originally planned for STS-57, but in the aftermath of the Intelsat-603 repair mission NASA decided in late 1992 to add spacewalks to as many shuttle flights as possible in order to build up an experience base within the astronaut office. In mid-February 1993, an EVA was added to STS-57, during which Low and Wisoff would spend four hours outside "to refine training methods for spacewalks, expand the EVA experience levels of astronauts, flight controllers, and instructors, and aid in better understanding the differences between true microgravity and the ground simulations used in training." Since Endeavour carried the RMS arm for the EURECA retrieval, it was decided to make use of it to rehearse procedures ahead of the Hubble Space Telescope servicing mission in December 1993. However, the criticality of Low and Wisoff's EVA was of a low level and it was stressed that only if STS-57's nominal mission duration was extended from seven to eight days would it be cleared to take place.

The decision was to be made shortly after launch and was based upon calculations of the propellant and energy expenditure and how well they matched predictions. Fortunately, these proved to be in line with expectations and on 23 June the Mission Management Team agreed to extend STS-57 to eight days. Plans for the EVA involved Low and Wisoff taking turns in a foot restraint on the end of the RMS—manipulated by Nancy Sherlock—and handling each other's mass to imitate the movement of large pieces of equipment. Moving large masses on the end of the mechanical arm was expected to be a critical requirement for both Hubble and Space Station Freedom missions. The spacewalkers also trained to investigate techniques for managing their safety tethers. The EVA, which ran to five hours and 50 minutes in total, ran exceptionally smoothly, with Sherlock positioning Low on the RMS to enable him to secure EURECA's antennas against their latching mechanisms. Payload controllers then remotely drove the latches to secure each antenna.

Since the EVA required the astronauts to depart Endeavour via the middeck-to-Spacehab tunnel, it was necessary for the pressurized module to be temporarily closed off. Subsequent investigation revealed no pressure loss from Spacehab during this time. It may, however, have induced an event which scared the daylights out of the four crew members inside the cabin. During the EVA, the shuttle was positioned with her belly toward the Sun, in order to simulate the deep cold of space which would be experienced at phases of Hubble servicing and Space Station Freedom construction.

David Low (right) and Jeff Wisoff at work during their EVA. Photo Credit: NASA

David Low (right) and Jeff Wisoff at work during their EVA. Photo Credit: NASA

"All of a sudden, it was as if somebody took the orbiter and hit it with a bulldozer," recalled Brian Duffy in his NASA oral history. "The whole vehicle shook. It got quiet on the flight deck and we thought maybe we were hit by something. We looked outside and didn't see any damage. Nothing came flying through the wings or through the payload bay." They informed Mission Control, who also saw nothing amiss in their data. The most likely explanation, it seemed, was that residual forces that had built up on the ground in the struts holding the Spacehab-1 tunnel in place had released "and it rang the whole vehicle." When the two spacewalkers returned to the cabin, they said that they had felt nothing. "They didn't have a clue," Duffy chuckled, "but if they'd looked inside at that time, they would have seen eight big eyes!"

Low and Wisoff's EVA demonstrated the importance and usefulness of having astronauts on hand to tend to unforeseen contingencies. It also provided EVA experience for another pair of astronauts, including the first spacewalk for a member of the 1990 astronaut class. Years later, Wisoff was asked about it by a NASA interviewer. "It's an incredible opportunity," he said, "an incredible experience. You're kind of in your own little spaceship in the space suit and you can't beat that view of the Earth while you're working. It's an incredible sight!" Despite the successful closure of EURECA's twin antennas, an attempt to activate the RMS arm's Special Purpose End Effector (SPEE) connector power relay, which was to provide electrical sustenance to the satellite, failed. It subsequently became clear from on-orbit video footage and post-flight inspection that the SPEE had been incorrectly rotated by 180 degrees.

Spacehab-1, in particular, proved to be an enormous success. The module's interior environment had a tendency to be quite cool at times, prompting a pair of in-flight maintenance procedures by the astronauts to successfully adjust the cold-water bypass valve and increase the temperature slightly. The cause was later attributed to lower electrical power requirements for Spacehab than had been predicted in pre-flight tests. In other words, it was not generating as much waste heat as predicted, but the cooling system was still working at full capacity. Overall, the module's experiments exceeded 90 percent of plans. The mission was challenging for all six crew members, including Grabe, who had never done rendezvous or EVA on any of his previous three missions. "We had Ron kinda carrying the ball," Brian Duffy recalled. "Particularly in the training, he was just really good about knowing what was important for us, what we needed to know, what we should focus on."

With a one-day extension to the mission, STS-57 was scheduled to land on 29 June, but Endeavour's return actually came 48 hours later than planned. Unsatisfactory weather in the vicinity of the Shuttle Landing Facility at KSC forced a one-orbit wave-off, and when there was no improvement a 24-hour postponement was ordered. The next day, the 30th, offered no respite and another 24-hour delay was imposed. Finally, early on 1 July, Grabe and Duffy performed the de-orbit burn at 7:41 a.m. EDT, committing the vehicle to its hypersonic dive through the atmosphere. Touchdown on Runway 33 came an hour later at 8:52 a.m., just 15 minutes short of ten full days since liftoff.

Endeavour touches down within sight of the gigantic Vehicle Assembly Building (VAB) on 1 July 1993. Photo Credit: NASA

Endeavour touches down within sight of the gigantic Vehicle Assembly Building (VAB) on 1 July 1993. Photo Credit: NASA

The re-entry, Duffy related, was nominal, but characterised by one unanticipated event. "This one was a flatter, lower trajectory" than his first flight, he said. "We were coming across northern Mexico and then across the Gulf, coming in almost due east, and it was … after sunrise, maybe mid-morning." All at once, as they passed through Mach 21, a sudden wham echoed through the vehicle's airframe. About 30 seconds later, another one followed. Nancy Sherlock, sitting in the flight engineer's seat, looked up in surprise after the first event, but noticed that Grabe and Duffy—the veterans—seemed unperturbed and said nothing. When it happened again, Grabe turned to his pilot.

"Have you ever felt that before?"

"No," replied Duffy, perplexed. It later became clear that Endeavour had been shaken by a "density shear"—an air-mass differential at extreme high altitude, which Endeavour had transitioned at hypersonic speed. "Those things extend up at a high altitude," Duffy reflected later, "and when you're going very fast and you change from one to the other, you get an instantaneous notification that you're somewhere else. It's like somebody really picks up and shakes the whole orbiter. The whole vehicle rings, because [it's] not very sturdy. It looks sturdy, [but] it's about as stiff as a Twinky and, truth be known, during ascent you can actually feel it flexing."

With the exception of an ammonia cooling glitch on the runway, which required Grabe to work closely with ground crews to establish cooling and prevent an emergency power-down, Endeavour's return from her fourth flight was a spectacular success. It also cemented life-long friendships for the STS-57 crew and reinforced memories of their flight. "Nancy and I were on the flight deck one night," said Duffy, during the weather wave-off period, "where we were waiting to go to bed—basically hanging out—and she and I were upstairs, turned all the lights out on the flight deck and the two of us just sat there and floated in the window and watched the Earth going by in the dark. It was pretty neat." The down side of having to spend two additional days in orbit was that they had to budget their camera film and by 1 July it was all gone. "We didn't even have film to shoot" at the end, noted Duffy, "so we just got to look and just enjoy it. It was really cool."

The safe return of the STS-57 crew, two decades ago, marked yet another milestone in the history of women in space, with military and civilian female astronauts aboard the same mission for the first time. Barely three decades had passed since Valentina Tereshkova became the first woman in space and a mere ten years since Sally Ride picked up the baton for the United States. In that span of time, a woman had walked in space, three women had flown aboard a single mission, and the first African-American woman astronaut had been launched. In the ten years after STS-57, the first female shuttle pilots would fly missions, and in the ten years after that the first female International Space Station commanders. Earlier this month, NASA selected its 21st group of astronaut candidates. Eight strong, and including four women, they mark the most evenly matched mix of the sexes in any astronaut (or cosmonaut) selection in history. Today, in June 2013, two women—China's Wang Yaping aboard the Shenzhou-10/Tiangong-1 complex and NASA's Karen Nyberg aboard the ISS—continue the legacy.

And what of the next ten years? And the ten after that? The first woman on the Moon, perhaps? The first female to set foot on an asteroid … or even Mars? The door to the future stands open.

 

Copyright © 2013 AmericaSpace - All Rights Reserved

 

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