Mission for Science and Technology: 18 Years Since STS-77 (Part 2)

Fully deployed, the Inflatable Antenna Experiment (IAE) sprouts from the SPARTAN-207 satellite. Photo Credit: NASA

Fully deployed, the Inflatable Antenna Experiment (IAE) sprouts from the SPARTAN-207 satellite. Photo Credit: NASA

Eighteen years ago this week, six men orbited Earth aboard Shuttle Endeavour on one of the most complex research flights ever conducted in the program’s 30-year history. With such a large number of payloads aboard, it was imperative for the STS-77 crew to begin activating as many experiments as possible on the first day of their planned 10-day flight. As described in yesterday’s AmericaSpace history article, STS-77 was tasked with a multitude of experiments in the commercial Spacehab-4 laboratory and the deployment and retrieval of as many as four free-flying satellite payloads. Launch was originally targeted for 16 May 1996, but was pushed back to the 19th, since the earlier date was not available to NASA on the Eastern Range schedule. Commander John Casper, pilot Curt Brown, and mission specialists Andy Thomas, Dan Bursch, Mario Runco, and Canada’s Marc Garneau had been training for the mission for almost a year, having been assigned in June 1995, and took their seats aboard Endeavour for a rousing, early-morning liftoff at 6:30 a.m. EDT.

Shortly after entering orbit and doffing their pressure suits, the six men set to work. In spite of a problem with a cooling device for one of the orbiter’s hydraulic power units, Thomas and Garneau opened the hatch into the Spacehab module, floated inside, and began powering up experiments. Later in the day, Thomas also checked out the shuttle’s Canadian-built Remote Manipulator System (RMS) mechanical arm, ahead of the deployment of their SPARTAN-207 satellite payload.

As the only first-time spacefarer on STS-77 crew, Andrew Sydney Withiel Thomas served as the payload commander, with overall responsibility of all of the mission’s research objectives and science goals. Born in Adelaide, South Australia, on 18 December 1951, Thomas’ father would later recount that his son became fascinated by space exploration as a child and built a steady stream of model rockets from cardboard and plastic. He received much of his early schooling in Adelaide, then earned a first-class degree in mechanical engineering from the University of Adelaide in 1973 and stayed on to pursue his PhD. “As a young kid, growing up in Australia, the likelihood of me being selected as an astronaut was pretty thin,” Thomas told a NASA interviewer, “and I didn’t really consider it a very realistic possibility.” In his mind, the power of gaining a good education was the fundamental cornerstone, coupled with a conscious effort to steer his subsequent career goals toward the space programme. “I took steps in my career that would give me exposure to the right kinds of technical problems and technical experiences,” he said, “which would make me a good candidate for an astronaut position.” In 1977, shortly before receiving his doctorate, Thomas became a research scientist with the Lockheed Aeronautical Systems Company, with responsibility for investigations into the control of fluid-dynamic instabilities and aircraft drag. He was promoted to Principal Aerodynamic Scientist in 1980 and accepted the headship of the Advanced Flight Sciences Department in 1983, overseeing a group which explored problems in advanced aerodynamics and aircraft flight testing.

With a keen eye on joining NASA as an astronaut, Thomas became a naturalized U.S. citizen in December 1986, became the manager of Lockheed’s Flight Sciences Division the following year and in 1989 moved to Pasadena, Calif., to join the Jet Propulsion Laboratory (JPL), later rising to become supervisor of the Microgravity Research Group. Three years later, in March 1992, he was selected by NASA as an astronaut candidate. His lifelong dream had been realised, and all due to the power of education. Thomas’ attitude was that education opened a path to many of his life experiences. “In fact,” he concluded, “it can open doors that you can’t even imagine and that would remain forever closed.”

The STS-77 crew. Seated are John Casper (right) and Curt Brown (left), with Dan Bursch, Mario Runco, Marc Garneau and Andy Thomas standing. Photo Credit: NASA, via SpaceFacts.de

The STS-77 crew. Seated are John Casper (right) and Curt Brown (left), with Dan Bursch, Mario Runco, Marc Garneau, and Andy Thomas standing. Photo Credit: NASA, via SpaceFacts.de

Flying in space for the first time on STS-77 was a totally new path for Andy Thomas, even when placed alongside many of the challenges he had overcome on Earth. “And although the environment is totally alien and unnatural, your body starts to accept it as being natural and psychologically you accept it as being natural,” he said. “You start to feel that being weightless is just the normal way to be; that everything does float and that you float. It’s just the amazing adaptability of the human body. Of course, the down side to that is when you come back, you have to re-educate your body to working in gravity. You feel all your internal organs being pulled down, your arms being pulled down, your head being pulled down and you stand up and just feel this ponderous mass of your entire body. It gives you a perspective on gravity … that people just generally never get unless you go through that. You realize just what a demanding force it actually is.”

In Endeavour’s middeck, the Immune-3 experiment tested the ability of insulin-like growth factor to prevent or reduce the detrimental effects of microgravity exposure on the immune and skeletal systems of rats, whilst three investigations sought to crystallize various protein crystals with objectives to address a range of diseases and the Gas Permeable Polymer Membrane (GPPM) pioneered the development of enhanced polymers for manufacturing rigid gas-permeable contact lenses. The National Institutes of Health provided a tissue culture incubator, and its experiments focused on the influence of weightlessness on the muscle and bone cells of chicken embryos. Elsewhere, the metamorphosis of tobacco hornworm was examined, as part of efforts to understand the synthesis of muscle-forming proteins,   the processes of fertilisation, and embryonic development of small aquatic organisms, including starfish, mussels, and sea urchins. In fact, the latter was one of the first experiments to be activated by Mario Runco, a few hours after liftoff.

With such substantial involvement from Canada, it seemed unsurprising that STS-77 featured a Canadian astronaut as one of its four mission specialists. In fact, Joseph Jean-Pierre Marc Garneau became Canada’s first man in space when he served as a payload specialist aboard shuttle mission STS-41G in October 1984. He came from Quebec City, where he was born on 23 February 1949. His father was an army officer “and we traveled quite a bit when I was growing up,” he told a NASA interviewer, “and I thought that I would like to have a military career, although I was drawn more towards the Navy.” Garneau would explain this decision in just three words: love of adventure. He was educated in Quebec and received his degree in engineering physics from the Royal Military College of Canada in Kingston in 1970. Garneau traveled to England in pursuit of his doctorate, studying electrical engineering at the Imperial College of Science and Technology in London. After gaining his PhD in 1973, he joined the Canadian Forces Maritime Command as a Navy engineer, serving aboard HMCS Algonquin and later as a forces fleet school instructor. During this period, Garneau designed a simulator to train weapons officers to use the missile systems aboard Tribal-class destroyers. Whilst at staff college in 1982, he was promoted to the rank of commander in the Canadian Navy. He was transferred to Ottawa the following year to design naval communications and electronic warfare systems and equipment.

In December 1983 he was selected as an astronaut candidate, and in February he was seconded from the Department of National Defence to commence full-time training. Following his first shuttle mission, Garneau was promoted to captain in the Navy and retired from active military service in 1989 to become deputy director of the Canadian Astronaut Programme (CAP). In mid-1992, alongside fellow Canadian Chris Hadfield, he was selected by NASA for mission specialist training.

STS-77's primary cargoes dominate this view of Endeavour's payload bay in orbit. In the foreground is the Spacehab-4 module, with SPARTAN-207 visible in the background. Photo Credit: NASA

STS-77’s primary cargoes dominate this view of Endeavour’s payload bay in orbit. In the foreground is the Spacehab-4 module, with SPARTAN-207 visible in the background. Photo Credit: NASA

If Endeavour’s crew cabin and the Spacehab module both represented a hive of activity during STS-77, then the payload bay was similarly packed with experiments. The Brilliant Eyes Ten Kelvin Sorption Cryocooler Experiment (BETSCE) was carried as part of ongoing efforts to develop technologies to rapidly cool infrared and other sensors to near-absolute zero Kelvin (-273.15 degrees Celsius). The aim of BETSCE was to employ a highly reliable “sorption cooler,” which exhibited virtually no detrimental effects of vibration, to cool infrared sensors to just 10 degrees Kelvin (-263.1 degrees Celsius). “Sorption coolers work by using specialised metal alloy powders, called metal hydridges, that absorb the hydrogen refrigerant through means of a reversible chemical reaction,” NASA explained in its STS-77 pre-flight press kit. “In the sorption compressor, the metal powder is first heated to release and pressurise the hydrogen, and then cooled to room temperature to absorb hydrogen and reduce its pressure. By sequentially heating and cooling the powder, the hydrogen is circulated through the refrigeration cycle. Ten degrees Kelvin is achieved by expanding the pressurised hydrogen at the cold tip of the refrigerator. This expansion actually freezes the hydrogen to produce a solid ice cube. The heat load generated by the device being cooled then sublimates the ice. This closed-cycle operation is repeated over and over.”

Previous astronomy missions which conducted their studies in the infrared needed to carry large, heavy, and expensive dewars of liquid helium or hydrogen to accomplish operating temperatures as low as 10 Kelvin, but the duration of their useful lives were restricted when the cryogens eventually boiled off and ran out. “The ability to achieve a lifetime of ten or more years, with no vibration,” NASA added, “opens the door to a wide variety of future missions that could benefit from this novel technology.”

Mounted atop a Hitchhiker structure in Endeavour’s payload bay was the Technology Experiments for Advancing Missions in Space (TEAMS), provided by NASA’s Goddard Space Flight Center (GSFC) of Greenbelt, Md., which featured four investigations: the GPS Attitude and Navigation Experiment (GANE) to gauge the effectiveness of Global Positioning System technology, which was then in its infancy, the Vented Tank Resupply Experiment (VTRE) to evaluate improved methods for refueling in space, the Liquid Metal Thermal Experiment (LMTE) to test potassium-filled liquid metal heat pipes in microgravity, and the Passive Aerodynamically Stabilized Magnetically Damped Satellite-Satellite Test Unit (PAMS-STU). The latter was of particular interest on STS-77, for its presence led the mission to establish a new record as the first shuttle flight to complete as many as four separate rendezvous operations. Developed by NASA-Goddard, PAMS-STU was a technology demonstrator for the principle of natural “aerodynamic stabilization,” which it was hoped might increase the orbital lifetime of satellites by reducing or eliminating the need for large quantities of attitude-control propellants. “Aerodynamic stabilisation works the same way as a dart,” NASA explained shortly before the STS-77 launch. “The front of the dart is weighted and once the dart is thrown, it will always right itself with the head facing forward. In the same manner, the PAMS-STU satellite will eventually be oriented with the heavy end facing forward in orbit. This principle can be used to partially control the attitude of small satellites.”

Within sight of the giant Vehicle Assembly Building (VAB), Endeavour touches down at the Kennedy Space Center (KSC) on 29 May 1996. Photo Credit: NASA

Within sight of the giant Vehicle Assembly Building (VAB), Endeavour touches down at the Kennedy Space Center (KSC) on 29 May 1996. Photo Credit: NASA

On the fourth day of the mission, 22 May 1996, the PAMS-STU operations got underway when Runco deployed the cylindrical, 2 x 3 foot (60 x 90 cm) satellite at 5:18 a.m. EDT from a canister at the rear end of Endeavour’s payload bay.  As intended, it drifted away from the orbiter in a rotating, unstable attitude, in order to evaluate how quickly and effectively it could stabilise itself using natural aerodynamics. Casper and Brown maneuvered the shuttle to a distance of nine miles (14.6 km) to begin the first of three scheduled rendezvous exercises. A little over 4.5 hours later, they drew closer to about 1,970 feet (600 meters) to track PAMS-STU with the laser-based Attitude Measurement System (AMS) in the payload bay. However, it was noticed that the satellite had not yet stabilized itself and a strong “lock” could not be obtained. With two further rendezvous sessions, each lasting around 6.5 hours, planned for 24 and 25 May, Endeavour withdrew to a maximum distance of about 64 miles (103 km).

During their second rendezvous on 24 May, Casper and Brown reached a station-keeping point just 1,700 feet (520 meters) from PAMS-STU and held their position for more than six hours, until a problem arose with the Space Experiment Facility (SEF) in the Spacehab module and Andy Thomas was called away to commence troubleshooting. It was clear from video imagery acquired by the crew that the satellite had begun to stabilize itself with natural aerodynamic forces, albeit somewhat slower than expected. The third and final rendezvous was postponed by 24 hours, until 26 May, in order for engineers to evaluate the AMS, which provided high-accuracy data (to within one-tenth of a degree) on the behavior and relative motions of PAMS-STU. Although it had proven its ability to track the small satellite, the laser system seemed to be locking onto an unknown target (perhaps a structure in the payload bay) and was subjected to intensive troubleshooting.

Throughout those 24 hours, Endeavour moved away from the satellite, reaching a maximum distance of about 115 miles (185 km), before Casper executed a Reaction Control System (RCS) thruster firing on the 26th to begin the third period of rendezvous. Closing on PAMS-STU at about 2.3 miles (3.7 km) per orbit, this time the operation ran by the book, with Casper and Brown guiding their ship to within 1,800 feet (550 meters) of their quarry. As the orbiter’s payload bay faced the satellite, NASA-Goddard flight controllers successfully commanded the AMS to calculate its attitude to within one-tenth of a degree. The pilots moved closer, to just 1,640 feet (500 meters), and held their position for seven hours and 45 minutes. This was about 70 minutes longer than planned, as controllers verified that the AMS laser was impinging on PAMS-STU’s reflectors. Throughout the third rendezvous, the satellite remained very stable and validated the aerodynamic stabilization concept.

Departing PAMS-STU for the final time, the STS-77 crew entered the final days of their mission, heading for a landing at the Kennedy Space Center (KSC) in Florida on 29 May 1996. It was expected that the small satellite would re-enter the upper atmosphere to destruction after a few weeks, although trajectory specialists noted that it might remain aloft until as late as January 1997. (As circumstances transpired, PAMS-STU ended its days on 26 October 1996.) Weather forecasts at KSC and Edwards Air Force Base, Calif., were highly favourable for an on-time landing, with two opportunities available at each site on the 29th. The first opportunity to land in Florida was taken, and Casper executed the de-orbit burn at 6:09 a.m. EDT and guided his ship to a smooth touchdown on Runway 33, precisely an hour later, at 7:09 a.m. With more than 21 cumulative hours of formation flying, Endeavour’s crew had secured a new record for themselves by becoming the first mission to execute four discrete periods of rendezvous. STS-77 also marked the first shuttle flight to be powered into orbit by a full set of three Block I main engines and the first to be fully controlled from the new Mission Control Center (MCC) at the Johnson Space Center (JSC) in Houston, Texas.

 

This is part of a series of history articles, which will appear each weekend, barring any major news stories. Next week’s article will focus on Gemini IV in June 1965, during which astronaut Ed White became the United States’ first spacewalker.

 

 

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