Twenty-five years ago, next week, the crew of Columbia roared into orbit to begin the longest shuttle mission ever attempted at that time. Equipped with the Extended Duration Orbiter (EDO) hardware—a pallet of additional hydrogen and oxygen reactant tanks in the payload bay, together with other associated upgrades—Columbia and her seven-strong crew were expected to remain in low-Earth orbit for almost 13 days, a full 48 hours longer than the next-longest mission in Space Shuttle Program (SSP) history. As circumstances transpired, the STS-50 astronauts completed a record-breaking mission, landing just a few hours shy of 14 days in space, and in doing so they set an important benchmark in preparation for the construction and operations of today’s International Space Station (ISS).
It had long been expected that Columbia, the oldest and heaviest member of NASA’s extant shuttle fleet after the Challenger accident, would support the bulk of EDO missions. Following her STS-40 flight in June 1991, she was withdrawn from service for almost a year for the requisite hardware enhancements to be implemented. A $93.5 million contract upgrade with shuttle prime contractor Rockwell International of Palmdale, Calif., awarded in January 1991, allowed for the work, which would transform Columbia from a vehicle with an approximately ten-day lifespan to as many as 16 days, plus two contingency days, per mission. Specific improvements to the vehicle—which had completed 11 flights by June 1991, totaling over 70 days in orbit—included new Environmental Control and Life Support Systems (ECLSS), better waste management facilities and additional gaseous nitrogen and crew stowage provisions.
Flown out to Palmdale in August 1991, Columbia received 150 modifications, most visibly the (1,630 kg) EDO pallet and a new Regenerative Carbon Dioxide Removal System (RCRS). The pallet measured 15.1 feet (4.6 meters) in diameter and housed four liquid oxygen tanks, two liquid hydrogen tanks and a pair of helium tanks. When fully loaded, it could store 3,130 pounds (1,420 kg) of liquid oxygen and 368 pounds (167 kg) of liquid hydrogen, pushing its total weight to almost 7,000 pounds (3,180 kg). Meanwhile, the RCRS provided an “adsorption” method for removing the astronauts’ exhaled carbon dioxide from the cabin more efficiently than had been previously possible with replacement lithium hydroxide canisters.
Further improvements to Columbia included additional nitrogen tanks, several stowage lockers in her middeck, beefed-up synthetic tires for her Nose Landing Gear (NLG) and Main Landing Gear (MLG) and the “drag chute” to assist with controllability during touchdown and rollout. The shuttle was returned to the Kennedy Space Center (KSC) in early February 1992, tracking a launch attempt for her first EDO mission in June. “I think we’ve all been aware that living together and working together for 13 days is certainly a challenge,” said STS-50 Commander Dick Richards, whose two previous shuttle flights had lasted around four days. “We’ll be sharing the same sleeping quarters. We have only one restroom on board. We all have to co-operate to make life as good as possible.”
Following his second mission, STS-41 in October 1990, Richards approached Chief Astronaut Dan Brandenstein to express reservations about the short nature of many post-Challenger shuttle flights. “I just raved to NASA about the fact that I can’t believe we’re going up there and spending four days here,” he told the NASA oral historian. “So they said, okay, we’ve got this flight coming off called United States Microgravity Laboratory…” The rest was history.
Richards’ words highlighted a key objective of EDO: to examine the astronauts’ physical and psychological performance in close quarters over the span of a long mission. When the STS-50 stack was rolled out to Pad 39A on 3 June, his crew had been in training for around 18 months. His pilot, 35-year-old Ken “Sox” Bowersox, would secure a record as the youngest person ever to serve as a shuttle pilot. In October 1995, he would also secure the record as the youngest-ever shuttle commander.
Bowersox’s involvement in STS-50 was a curious one. When his name was announced for STS-50 in December 1990, it was as one of the Mission Specialists, serving as flight engineer to Richards and Pilot John Casper. This practice of initially flying pilot astronauts as flight engineers was not new and had been seen on a number of dual-shift missions in which a “third” pilot was needed to supervise the orbiter’s flight deck. Circumstances changed in the summer of 1991, when veteran shuttle commanders Mike Coats and Bryan O’Connor retired from NASA. The result was a shortfall in the number of available veteran pilots to rotate to the commander’s seat.
In August, the space agency announced that two astronauts previously assigned as pilots—John Casper on STS-50 and Jim Wetherbee on STS-46—would be removed from their posts to command a pair of subsequent missions. Both Casper and Wetherbee had previously flown once as a pilot, thus satisfying a requirement to command a shuttle flight. In the case of STS-50, this enabled Bowersox to rotate from the flight engineer’s seat into the pilot’s position. In turn, his old seat was taken by another astronaut, Ellen Baker.
Rounding out the seven-strong crew were a ‘science team’ of Mission Specialists Bonnie Dunbar and Carl Meade and Payload Specialists Larry DeLucas and Gene Trinh. Dunbar had been assigned to the mission in September 1990. As “Payload Commander”, she was responsible for the overall scientific success of the mission, whilst a quartet of Payload Specialist candidates—DeLucas and Trinh, together with Joe Prahl and Al Sacco—began training around the same time. DeLucas and Trinh were announced as the “prime” STS-50 Payload Specialists in May 1991, with Prahl and Sacco backing them up.
Working around-the-clock in two 12-hour shifts, the astronauts would oversee 31 experiments in crystal growth, combustion science, fluid physics and biotechnology aboard the 23-foot-long (7-meter) Spacelab pressurized module in the shuttle’s payload bay. Designated as the First U.S. Microgravity Laboratory (USML-1), it was described as a direct precursor to upcoming Space Station operations. A “red team” of Dunbar and DeLucas, led by Bowersox, and a “blue team” of Meade and Trinh, led by Baker, would utilize the microgravity environment to tackle a wide range of research experiments.
“We think we’re ready,” Dunbar told journalists as the STS-50 crew arrived at the Kennedy Space Center (KSC) in Florida on 22 June 1992, three days ahead of launch. “We’re really looking forward to an aggressive 13-day flight.” Dunbar would actually break her own record for the longest shuttle mission, jointly set as a member of the STS-32 crew, when she spent almost 11 days in orbit in January 1990. Upon her return from STS-50, she would be able to claim another record, by having the most number of hours for a female spacefarer. Her record would stand for more than a year.
In his NASA oral history, Commander Dick Richards recalled that Dunbar’s role in USML-1 ran deep. As chair of NASA’s agency’s Microgravity Materials Science Assessment Task Force in 1987, Dunbar realized that much of the planning for Space Station Freedom centered on Spacelab missions which had a life sciences bias, with little emphasis on the development of furnaces for directional solidification or materials research. In fact, the only Spacelab missions under consideration to focus on the physical sciences were those which involved European and Japanese participation.
Dunbar was keenly aware that such work had been pioneered aboard Skylab in the early 1970s and she felt that it was “a real loss of our investment and scientific discoveries of the future if we didn’t build facilities for [the new] station”. She worked closely with fellow astronaut Sally Ride, who was leading a team to prepare a strategic roadmap for NASA’s future, and one of the products of their efforts was the United States Microgravity Laboratory. “We flew USML-1…with all new facilities that were destined for the International Space Station,” Dunbar told the NASA oral historian.
Those facilities included an entirely new variety of furnaces, developed by Teledyne Brown Engineering, Inc., along with a fluid physics module and a range of life sciences experiments and lower-body negative pressure apparatus. “What was thrilling for me was to be asked to be payload commander of that flight,” she said. “In five years, I had an opportunity to see it go from a concept in a report to an actual flight of brand-new equipment and hardware.”
For 21 months, Dunbar worked on the mission timelines and would later derive satisfaction from the fact that “hand-overs” between the two USML-1 shifts were so seamless than they typically lasted no more than 15 minutes. It illustrated the excellence of their training. Much of that training was initially centred on the various institutions which developed the experiments. “You understand what the researcher wants to find, first,” Dunbar explained, “because you’re their hands, eyes and ears and if you don’t understand what they’re looking for, then when the unexpected comes up you also don’t recognize that, either. You’re part of the research team.”
By December 1991, the Spacelab crew was running fully integrated simulations; picking the busiest day of the flight, choreographing it to the minute and running crisply through their tasks. “You train like you fly,” Dunbar said, “and you fly like you train. You don’t have a chance to start over on orbit.”