Sunday, May 3, 2015

Fwd: 30 Years Since Mission 51B



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Begin forwarded message:

From: "Gary Johnson" <gjohnson144@comcast.net>
Date: May 3, 2015 at 9:30:27 PM CDT
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: 30 Years Since Mission 51B

 

 

AmericaSpace

AmericaSpace

For a nation that explores
May 2nd, 2015

A Long Wait for Space: 30 Years Since Mission 51B (Part 1)

By Ben Evans

Challenger roars into orbit on 29 April 1985. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Challenger roars into orbit on 29 April 1985. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Thirty years ago, this week, Challenger was circling the Earth on the first dedicated Spacelab science flight of the shuttle era. For seven days, the crew of Mission 51B—Commander Bob Overmyer, Pilot Fred Gregory, Mission Specialists Don Lind, Norm Thagard, and Bill Thornton, and Payload Specialists Lodewijk van den Berg and Taylor Wang—worked around the clock in two shifts to support 15 life and microgravity science experiments from U.S., European, and Indian researchers in the pressurized Spacelab-3 module. Launching on 29 April 1985, the flight made history by establishing a record of just 10 days between shuttle missions, yet as circumstances transpired it would come within milliseconds of disaster.

Spacelab-3 was actually the second voyage of the joint U.S./European research facility, following the inaugural mission of the pressurized module aboard STS-9 in the fall of 1983. Spacelab-2 was intended to be a Verification Flight Test (VFT) of the unpressurized pallet and igloo combination, but had encountered technical difficulties with the Instrument Pointing System (IPS) and ended up being slipped until after Spacelab-3. Consequently, the module and a Multi-Purpose Experiment Support Structure (MPESS) were loaded into Challenger's payload bay on 10 April, and the shuttle stack was transferred to Pad 39A at the Kennedy Space Center (KSC) just five days later. (In fact, only three days had elapsed since the launch of Mission 51D.)

During Mission 51B, Challenger would operate in a "gravity gradient" orbit, with her vertical stabilizer directed Earthward and her starboard wing pointing in the direction of travel, in order to ensure a stable microgravity environment and limit the amount of disruptive thruster firings. This would aid Spacelab-3's vibration-sensitive materials science and fluid physics investigations. In readiness for the mission, the roof-mounted Scientific Window Adapter Assembly (SWAA) was removed and replaced by an aluminum panel, whereas the Scientific Airlock (SAL) was retained to house a French-built very-wide-field camera. Outside, the MPESS would accommodate the Atmospheric Trace Molecule Spectroscopy (ATMOS) and the Studies of the Ionization of Solar and Galactic Cosmic Ray Heavy Nuclei ("Ions") experiments.

The patch for Mission 51B, emblazoned with the surnames of the seven-man crew. Image Credit: NASA

The patch for Mission 51B, emblazoned with the surnames of the seven-man crew. Image Credit: NASA

Twenty hours before launch, on 28 April 1985, a pair of male squirrel monkeys (Saimiri sciureus)—described by Don Lind as "cute"—and 24 "not so cute" male albino rats (Rattus norvegicus) were loaded aboard the Spacelab module. Animal welfare concerns, coupled with the requirement to move the primates and rodents during their "awake" time in order to avoid causing them undue stress, made it important to wait until the latter phase of the countdown before loading them into their cages. It proved an interesting event, since Challenger was oriented vertically on Pad 39A. Working from the shuttle's middeck, two technicians were gently lowered, one at a time, in sling-like seats down the tunnel into the module. One stayed in the joggle section, while the other entered the Spacelab to await the cages, which were lowered on separate slings. The two-hour process ran smoothly and the cages were installed into dual Research Animal Holding Facilities (RAHFs) on the module's port side wall.

Spacelab-3's primary focus was on microgravity research, specifically fluid physics and crystal growth, but an additional life sciences aspect evaluated how well the RAHF could support animals in an environment comparable to a ground-based vivarium. It had long been recognized that effective studies of primate or rodent behavior in space was impossible if their health and well-being were improperly maintained. In addition to water and food—rice-based bars for the rats, banana pellets for the monkeys—the RAHF supplied lighting, temperature, and humidity control functions. During the course of Mission 51B, Challenger's crew were to work in two 12-hour shifts, with physicians Thagard and Thornton assigned to separate teams to keep watch the animals around-the-clock. NASA hoped to use the RAHF again for several rodent experiments on the Spacelab-4 life sciences mission, planned for launch in the spring of 1987.

Also under test was a Dynamic Environment Measuring System (DEMS) to record the acceleration, vibration, and noise in the cages during ascent and re-entry, and a Biotelemetry System (BTS) to transmit physiological data to the ground from a series of implanted sensors. "The squirrel monkeys adapted very quickly," Lind told the NASA Oral History Project. "They had been on centrifuges and vibration tables, so they knew what the feeling of space was going to be like. Squirrel monkeys have a very long tail and if they get excited, they wrap the tail around themselves and hang onto the tip. If they get really excited, they chew on the end of their own tail. By the time we got into the laboratory, about three hours after liftoff, they were adjusted. They had, during liftoff, apparently chewed off a quarter of an inch of the end of their tails!" Both monkeys were free of various specified pathogens, and it was mandated that six months before launch they must also be free of antibodies to the Herpes saimiri virus. Although the virus was not known to cause disease in either squirrel monkey or human carriers, problems had been documented in other species and a global search found five Herpes saimiri-free primates. Due to time limitations, NASA only had the opportunity to prepare two of them for microgravity exposure and properly train them to reach the food pellets and activate the water taps in their cages.

The crew of Mission 51B departs the Operations & Checkout (O&C) Building on the morning of 29 April 1985. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

The crew of Mission 51B departs the Operations & Checkout (O&C) Building on the morning of 29 April 1985. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

The possibility, however remote, of all seven men becoming infected by herpes was hungrily pounced upon by their peers at the Johnson Space Center (JSC) in Houston, Texas, according to Mike Mullane in his 2006 memoir, Riding Rockets. Several Navy astronauts suggested that as long as the Marine Corps and Air Force members of the crew—a none-too-subtle jab at the respective military services of Overmyer and Gregory—did not "screw the monkeys," they would be fine. Alongside Overmyer and Gregory were no less than five scientists: Thagard and Thornton were both physicians, whilst Lind was a physicist, Dutch-born van den Berg was a chemical engineer, and Shanghai-born Wang was a physicist. Three of these men were intimately involved in several Spacelab-3 experiments as co-investigators: Lind on an auroral imaging study, van den Berg on a vapor crystal growth system, and Wang on the Drop Dynamics Module (DDM).

In fact, van den Berg was internationally recognized as an authority on vapor-driven crystal growth. As the list of Spacelab-3 Payload Specialist candidates was drawn up, van den Berg and his chief at EG&G Corp., Dr. Harold Lamonds, could only come up with seven names, rather than the required eight. Lamonds told fifty-something van den Berg to volunteer, joking that his age, huge spectacles, and limited physical strength would probably cause him to be dropped in the first round of the selection process. It didn't. Four candidates were eliminated by the initial screening for scientific competence. He was now down to the final four for a series of physical and mental tests, and he and metallurgical engineer Mary Helen Johnston passed with flying colors, whereas two others fell by the wayside due to possible heart issues. In June 1983, van den Berg and Johnston began training at JSC and in the fall of the following year, against all the odds, van den Berg was formally announced as the prime candidate.

If van den Berg's ascent to a prime crew was rapid, then the opposite was the case for Don Lind, who had waited 19 years since his selection as an astronaut by NASA in April 1966. Having trained extensively for Skylab, he came within days of flying with Vance Brand on a daring rescue mission to America's first space station in 1973, but wound up waiting longer than any other NASA-selected astronaut in history to reach actually space. It is a record that Lind still holds to this very day. When he was assigned to Spacelab-3 in February 1983, he expected to fly in September of the following year, but payload delays and shuttle manifest changes caused a slippage to November, then January 1985, and ultimately April, as well as switching orbiters from Challenger to Discovery, then back to Challenger again. With 54-year-old Lind, 53-year-old van den Berg, and 56-year-old Thornton aboard, this was the first U.S. piloted space mission to carry as many as three astronauts above the age of 50.

During the majority of the seven-day mission, Challenger operated in a gravity gradient orientation, with her vertical stabilizer directed Earthward and her starboard wing pointing in the direction of travel. Image Credit: NASA, via Joachim Becker/SpaceFacts.de

During the majority of the seven-day mission, Challenger operated in a gravity gradient orientation, with her vertical stabilizer directed Earthward and her starboard wing pointing in the direction of travel. Image Credit: NASA, via Joachim Becker/SpaceFacts.de

As a dual-shift flight, the seven-man crew adopted "sleep-shifting" during their final days on Earth. On the Gold Shift were Overmyer, Lind, Thornton, and Wang, whilst the Silver Shift comprised Gregory, Thagard, and van den Berg. "I was responsible for all the support systems that keep the orbiter functioning," said Gregory of his role as shift leader. "Norm and I had respective jobs on board, but we, in essence, were the folks who supported the work of the Payload Specialists." As the flight engineer, Thagard was technically part of the orbiter crew, but his work tended to cross over with that of the scientists working in the Spacelab module, and one of his responsibilities was caring for the rodents and primates on his shift. Lind, meanwhile, was in charge of the activation and deactivation of Spacelab-3 and for the bulk of its experiments, one of which had dictated Mission 51B's launch time.

Challenger had scarcely an hour available in which to launch on 29 April 1985, with her "window" opening at noon EDT. This was calculated to provide the MPESS-mounted ATMOS instrument with the maximum number of viewing opportunities of the composition of the upper atmosphere during 72 orbital sunrises and sunsets. The ATMOS calibration and observations and a program for the French very-wide-field camera were "front-loaded" into the first day of the mission. Then, about 18 hours after liftoff, Overmyer and Gregory would reorient Challenger for almost six days in a gravity-gradient attitude to provide a suitably quiescent environment for the fluid physics and crystal growth investigations.

With the exception of a hydrogen leak in loading the External Tank (ET) with propellants, the countdown proceeded smoothly until 11:56 a.m. EDT, when, at T-4 minutes, a front-end launch processor failed and prevented the liquid oxygen replenishment valve and vent hood from closing automatically. The clock was held as the valves were manually repositioned and Challenger's thunderous ascent at 12:02 p.m. was described by NASA as "nominal."

However, it was not entirely nominal, because during the Rogers Investigation into the loss of Mission 51L in 1986, Bob Overmyer would discover exactly how close his crew came to death that day.

 

Copyright © 2015 AmericaSpace - All Rights Reserved

 


 

AmericaSpace

AmericaSpace

For a nation that explores
May 3rd, 2015

'The Lord Protected Grandpa': 30 Years Since Mission 51B (Part 2)

By Ben Evans

During the majority of the seven-day mission, Challenger operated in a gravity gradient orientation, with her vertical stabilizer directed Earthward and her starboard wing pointing in the direction of travel. Image Credit: NASA, via Joachim Becker/SpaceFacts.de

During the majority of the seven-day mission, Challenger operated in a gravity gradient orientation, with her vertical stabilizer directed Earthward and her starboard wing pointing in the direction of travel. Image Credit: NASA, via Joachim Becker/SpaceFacts.de

Thirty years ago, this week, a seven-man crew with a combined age of 340 years rocketed into orbit aboard Shuttle Challenger on Mission 51B. For seven days, the astronauts—Commander Bob Overmyer, Pilot Fred Gregory, Mission Specialists Don Lind, Norm Thagard, and Bill Thornton, and Payload Specialists Lodewijk van den Berg and Taylor Wang—worked around the clock in two shifts to support 15 life and microgravity science experiments from U.S., European, and Indian researchers in the pressurized Spacelab-3 module. As described in yesterday's AmericaSpace history article, they became the first U.S. crew to include as many as three over-50s, including the then-oldest man in space, but unbeknownst at the time they came within milliseconds of disaster, soon after liftoff.

For Gregory, his first launch proved exhilarating. "I was very excited," he told the NASA Oral History Project. "I think I was probably anxious, but certainly not afraid. It was similar to the simulations, but they left out the 5 percent, and that was the 'wow'! I remember the feeling inside when the main engines started; how it was almost a non-event. I could hear it and I was aware of it, but I looked out the window and saw the tower move back. At least that's what I thought, but then I realized the orbiter was moving forward and then back, and when it came back to vertical, that's when those solids ignited and there was no doubt about it: we were going to go someplace pretty fast! I just watched the tower kind of drop down below me and was probably laughing during this timeframe. Since we had trained constantly for failures, I anticipated failures and was somewhat disappointed that there were no failures. That was Challenger and she went uphill, just as sweet as advertised. The sensation of zero-G was like a moment on a roller coaster, when you go over the top and everything just floats. Once we got there, it was business as usual, just as we had practised and performed on the ground."

For Overmyer, Gregory, and Thagard, the first order of business was pulsing their spacecraft's twin Orbital Maneuvering System (OMS) engines to position themselves in a 225-mile (360-km) circular path. The orbit was inclined at 57 degrees to the equator to provide greater observation coverage for ATMOS. For Don Lind, the reality of actually traveling into space was surprisingly close to the training. "The simulations are spectacularly accurate," he said later. "With the motion-based simulators, you even got some of the visceral sensations, because they can move the machine around and give you the sense of onset of zero-G. You can't hold it indefinitely, but we had flown hundreds of parabolas in the KC-135 aircraft, so we were quite accustomed to those things."

Challenger roars into orbit on 29 April 1985. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Challenger roars into orbit on 29 April 1985. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Gregory felt that he was well prepared, "but it took about half a day to adapt to microgravity. The body very quickly adapted to this new environment and it began to change. You could sense it when you were on orbit. You learned that your physical attitude in relation to things that looked familiar to you—like walls and floors—didn't count anymore and you translated floors and ceilings and walls to your head is always 'up' and your feet are always 'down'. That was a subconscious change in your response: it was an adjustment that occurred up there. You also learned that you didn't go fast, that you could get from one place to the other quickly, but you didn't have to do it in a speedy way. The only referencing system that you have are your eyes, so you can look at something and establish it as a reference that you use."

Following launch, the seven astronauts split into their respective 12-hour teams. Very soon, one of the two squirrel monkeys exhibited the same symptoms—lethargy and loss of appetite, but no vomiting—as humans for the first half of the mission, being hand-fed by Thagard and Thornton at one stage, before recovering completely for the final three days. The second monkey displayed no ill effects. The primates proved to be much less active in space than on Earth, although both they and the rodents grew and behaved normally, were free of chronic stress, and differed from their "controls" on Earth only by way of gravity-dependent variables. The monkeys, in particular, were spoiled, too.

"I think the environment they had come from was a place where they received a lot of attention," said Gregory. "Norm and I would look into the Spacelab and see Bill Thornton attempting to get these monkeys to do things, like touch the little trigger that would release the food pellets. I could tell they expected Bill to do that for them, even though he was outside, looking in. We looked back one time and could see that the roles were kind of reversed and Bill was doing antics on the outside of the cage and the monkeys were watching!" Thornton and Thagard could view the primates through a window in each of their cages, while a perforated opening gave them limited access to the interior.

The Spacelab-3 research module, pictured aboard Challenger's payload bay during Mission 51B. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

The Spacelab-3 research module, pictured aboard Challenger's payload bay during Mission 51B. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

The rodents' enclosures were similar to those of the squirrel monkeys, with the exception that they housed two occupants per cage, separated by a partition. Half of the 24 rats were rapidly-growing, eight-week-old juveniles and the remainder were mature 12-week-old adults. Although the animals were maintained in healthy conditions throughout their seven days in orbit, the rats proved not quite as "savvy" as the monkeys in terms of their adaptation to microgravity. Nonetheless, all of the animals were recovered in good physical condition, healthy and free of microbiological contaminants. However, the astronauts returned to Earth with a number of concerns because the animal enclosures leaked food crumbs, monkey and rodent feces, and unpleasant odors. "The later analysis was that primarily it was food," said Gregory, "though there may have been some contaminants in it. Other than interest in watching it being ejected from the holding facility, I think it was just interest. It was a passing issue; not something that would have caused any disruption in the current activities."

On the ground, however, it became a big news story. "One anecdote involved this bit of animal dung that escaped from a cage and made its way from the Spacelab module to the flight deck," Thagard told this author in a March 2006 email correspondence, referring to an object that floated past the commander's nose. "Bob Overmyer made a comment about it that prompted an editorial page cartoon that appeared in some newspapers. The cartoon depicts a shuttle astronaut saying to a crewmate words to the effect of: I'm not upset, I'm just glad we didn't have elephants on board!"

Aside from the RAHF tests, the main "operational" focus of Spacelab-3 was fluid physics and crystal growth. Taylor Wang operated his own drop dynamics experiment whilst Lodewijk van den Berg focused on the crystal growth. Eighteen hours into the mission, Overmyer and Gregory maneuvered the shuttle into her gravity-gradient attitude to support six days of fluid physics and crystal growth research.

Taylor Wang's legs emerge from the Drop Dynamics Module (DDM) as Bill Thornton assists him with his experiment. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Taylor Wang's legs emerge from the Drop Dynamics Module (DDM) as Bill Thornton assists him with his experiment. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Unfortunately, Wang's DDM experiment shorted out and failed, early in the mission. "Not only that, but I was the first person of Chinese descent to fly on the shuttle," he wrote later, "and the Chinese community had taken a great deal of interest. You don't just represent yourself—you represent your family—and the first thing you learn as a kid is to bring no shame to the family. When I realized my experiment had failed, I could imagine my father telling me, 'What's the matter with you? Can't you even do an experiment right?' I was really in a desperate situation." On the ground, Lead Flight Director Gary Coen told the crew that it was doubtful that the mission could be extended beyond seven days, since Challenger did not have the additional cryogenic reactant tanks carried by her sister, Columbia. There would be no opportunity for time lost on the troublesome experiments.

In his memoir, Riding Rockets, Mike Mullane did not specifically name Wang, but certainly made reference to the incident. "Its failure severely depressed him and he surrendered to episodes of crying," Mullane wrote, "but this was just the beginning of his torture. He turned out to be a cleanliness freak. Living aboard the shuttle doesn't leave its occupants feeling springtime fresh!" In the midst of this discomfort and upset, Wang asked Mission Control for permission to try to repair the DDM and when given the go-ahead he quickly got to work, opening the Spacelab rack, isolating the fault, and completely rewiring part of it. Several dramatic photographs, taken by his crewmates, showed Wang's legs sticking out into the module as the DDM rack appeared to completely swallow his upper body. He had already threatened not to return home if NASA refused to allow him to fix the DDM, so it proved fortuitous that his bluff was not called.

"I hadn't really figured out how not to come back," Wang told a Smithsonian interviewer years later. "The Asian tradition of honorable suicide—seppuku—would have failed, since everything on the shuttle is designed for safety. The knife on board can't even cut the bread. You could put your head in the oven, but it's really just a food warmer. If you tried to hang yourself with no gravity, you'd just dangle there like an idiot!"

The patch for Mission 51B, emblazoned with the surnames of the seven-man crew. Image Credit: NASA

The patch for Mission 51B, emblazoned with the surnames of the seven-man crew. Image Credit: NASA

With the facility successfully repaired, there was no time for suicide and Wang worked virtually non-stop to complete almost all of his experiments in the last three days of the flight, assisted by his crewmates. The results confirmed several age-old assumptions about the behavior of liquids in a microgravity environment and, in spite of its delayed start, the experiment proved highly successful. Nineteen months later, in the fall of 1986, Wang received NASA's Exceptional Scientific Achievement Medal in recognition of his "contributions to microgravity science and materials processing in space and for his exceptional contributions as Payload Specialist on Spacelab-3." Elsewhere, Lind and van den Berg oversaw a range of crystal growth and fluid physics investigations on their respective shifts. "He'd brief me and then he'd go to sleep and when he woke up, I'd brief him on what I'd done during the last shift," Lind remembered, years later. "That was pretty well worked out ahead of time."

"I don't think there was competition," said Fred Gregory of the relationship between the silver and gold teams, "because the two shifts did two different kinds of science. Each shift had its own area of interest and would pick up any unclosed item from the shift preceding them, but would very quickly transition to the activities on orbit. There were really about four hours a day when there was an interaction between the two. During that time, it would just be a kind of status brief on orbiter problems or issues, any review of notes that had come up from Mission Control or some deviation to the anticipated checklist that we had."

For Lind, the first Mormon astronaut, the gravity-gradient attitude provided a unique perspective of his home planet. "For the first two days of the flight, I did not take one single minute away from the timeline to just be a tourist," he recalled, "but, on the third day, I had about ten or 15 minutes with no immediate assignment. I floated down to the flight deck. We were flying in an orientation with the tail always pointed toward the Earth and one wing always pointed forward in the velocity vector. That oriented the windows on the flight deck from the zenith to the nadir and from horizon to horizon, so it was like a Cinerama presentation. Both my wife and I are amateur oil painters. The sensation in space is that you are always right side up, no matter how you're positioned. 'Up' and 'down' are just meaningless in space! Intellectually, you know you're moving very fast, so that orbital velocity will cancel gravity, but the sensation is that you are stationary and the world is rotating majestically below you."

The crew of Mission 51B pose for the traditional in-flight portrait. From left to right are Fred Gregory, Bob Overmyer, Don Lind, Norm Thagard, Bill Thornton, Taylor Wang and Lodewijk van den Berg. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

The crew of Mission 51B pose for the traditional in-flight portrait. From left to right are Fred Gregory, Bob Overmyer, Don Lind, Norm Thagard, Bill Thornton, Taylor Wang and Lodewijk van den Berg. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Gregory found the heavens and Earth fascinating. "You immediately realize you are either a 'dirt person' or a 'space person'," he said. "I ended up being a space person. It was a high-inclination orbit, so we went very low in the southern hemisphere and I saw a lot of star formations that I had only heard about and never seen before. "I also saw the Aurora Australis, which is the Southern Lights. If you were a dirt person, you were amazed at how quickly you crossed the ground; how, with great regularity, every 45 minutes, you'd either have daylight or dark. The sensation that I got initially was that, from space, you can't see discernible borders and you begin to question why people don't like each other, because it looked like just one big neighborhood down there. The first couple of days, I was a citizen of Washington, D.C., but Overmyer was from Cleveland and Don Lind was from Salt Lake City and Norm was from Jacksonville and Lodewijk was the Netherlands and Taylor was Shanghai, so each had their own little location for the first couple of days. After two days, I was from America, and after five days the whole world was our home. You could see this sense of ownership and awareness. We had noticed with interest the fires in Brazil and South Africa and the pollution that came from eastern Europe, but it was only with interest. Then, after five or six days, it was of concern, because you could see how the particulates from the smoke stacks in eastern Europe circled the Earth and how this localized activity had a great effect. When you looked down at South Africa and South America, you became very sensitized to deforestation and how it affected the ecology."

It has often been remarked on dual-shift Spacelab flights that the only times the entire crew really got together were shortly after launch and just prior to re-entry. "I think on that particular mission, it may have been anticipated that we would prepare a meal and everyone would eat at the same time," said Gregory. "In reality, that's not what actually happened. I called it 'almost grazing'. You would go down and perhaps get a package of beefsteak and heat it and cut it open and eat it. You may stay on the middeck or you may go back up to the flight deck or you would go back into the laboratory and eat as you were doing your other routine duties."

Their descent into Edwards Air Force Base, Calif., on 6 May 1985, proved to be among the most dramatic memories of the mission for Gregory. "Though it takes 8.5 minutes to get up to orbit," he said, "it takes more than an hour to re-enter and it feels very similar to an airplane ride. You get an excellent view of the Earth. You're going pretty fast, but you are not aware of it, because you're so high. It's an amazing vehicle, because you always know where you are in altitude and distance from your runway. You know you have a certain amount of energy and so you also know what velocity you're supposed to land, and you watch this amazing vehicle calculate and then compensate and adjust as necessary to put you in a good position to land. We normally allow the automatic system to execute all the maneuvers for ascent and for re-entry, but as we slow down for landing, it is customary for the Commander to actually fly it in, using the typical airplane controls."

Challenger touches down at Edwards Air Force Base, Calif., on 6 May 1985. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Challenger touches down at Edwards Air Force Base, Calif., on 6 May 1985. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

The de-orbit burn, lasting closely to 4.5 minutes, began at 8:04:48 a.m. PDT (11:04:48 a.m. EDT) and slowed Challenger sufficiently to drop her out of orbit and set her on course for a touchdown on the west coast of the United States. "Absolutely nominal," was Overmyer's description of re-entry at the post-flight press conference. "I sat there with my hand on top of my helmet, with essentially nothing better to do than watch, at least down to Mach 0.9."

Quipped Norm Thagard in response: "Yeah, but the rest of us didn't know you were doin' that, or we'd have been more worried!"

After performing a graceful, 193-degree heading alignment circle turn, Overmyer guided the orbiter to a precision landing on Runway 17 at 9:11 a.m. PDT (12:11 p.m. EDT). Post-mission inspections of the shuttle revealed only superficial damage to her thermal protection tiles. However, following the loss of Challenger in January 1986, the Rogers Investigation would uncover worrisome signs that Mission 51B itself came close to disaster.

Post-flight examination of the twin Solid Rocket Boosters (SRBs) indicated erosion of the secondary O-ring seal and highlighted the failure of its primary seal. So serious was the incident—the seals were meant to prevent hot gas leakage from the structure of the boosters—that launch constraints were placed on several missions, later in 1985, but routinely waived.

"The first seal on our flight had been totally destroyed," recalled Lind in his NASA Oral History, "and the [other] seal had 24 percent of its diameter burned away. All of that destruction happened in 600 milliseconds and what was left of that last O-ring, if it had not sealed the crack and stopped that outflow of gases—if it had not done that in the next 200 to 300 milliseconds—it would have gone. You'd never have stopped it and we'd have exploded. That was thought provoking! We thought that was significant in our family. I painted a picture of our liftoff, then two great celestial hands supporting the shuttle and the title of that picture is Three-Tenths of a Second. Each of [my] children have a copy of that painting, because we wanted the grandchildren to know that we think the Lord really protected Grandpa."

 

Copyright © 2015 AmericaSpace - All Rights Reserved

 


 

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