For NASA flight research, the 1980s opened with a significant administrative change --the Dryden Flight Research Center lost its independent status and became a directorate of Ames Reseach Center in 1981. This did not mean that NASA was downgrading flight research; on the contrary, several exotic programs emerged during the decade, and a variety of unusual aircraft continued to populate the skies above Edwards.
Given the cost of experimental flight aircraft and the evolution of increasingly sophisticated electronic and simulator systems, it was perhaps inevitable that NASA eventually turned to smaller, pilotless radio-controlled aircraft. In the 1980s, this idea was embodied in the HiMAT, a contraction of Highly Maneuverable Aircraft Technology. The HiMAT, powered by a General Electric J85 turbojet engine, had a length of 23 feet and a wing span of 16 feet.
The compact HiMAT was an evolutionary concept, originating during the
M2 lifting body program of the 1960s. To test a variety of lifting body
shapes in flight, an innovative NASA engineer at Edwards built a twin-engine
radio-controlled model that carried the smaller test models high into the
sky and made 120 test drops. Typical remotely piloted vehicles (or RPVs)
used an autopilot system and had restricted maneuverability. The Edwards
aircraft, on the other hand, was completely controlled from the ground,
using instrument references. By the late 1960s, Edwards personnel were
flying an actual lifting body test configuration,the Hyper III,
in drop tests from a helicopter. Veteran fliers who flew the model by remote
control found it a remarkable experience. "I have never come out of a simulator
emotionally and physically tired as is often the case after a test flight
in a research aircraft," one pilot said. "I was emotionally and physically
tired after a 3-minute flight of the Hyper III," he admitted. Although
remote flight research continued, demands of the YF-12 Blackbird program
and other projects kept it at a low level. Still, significant progress
occurred. The Edwards team took a Piper Twin Comanche fitted with an electronic
fly-by-wire system, added a television system for a remote pilot, and turned
it into a successful remotely piloted aircraft from takeoff to landing.
Although a backup pilot flew in the cockpit, the remote operators practiced
stalls, stall recoveries, and even made precise instrument landing approaches.
In the early 1970s, these skills were translated into an applicable test
program to investigate stall and spin phenomena after several fighter planes
were lost in spinning accidents. NASA let contracts to McDonnell Douglas
for three 3/8-scale models of the F-15. Each model cost $250,000; a full-sized
plane cost $6.8 million. Piloted from the ground and released from a B-52
at high altitude, the model F-15 program yielded useful information for
final revisions of the operational Air Force fighter. The remote pilots
doing the flying found the spin tests quite challenging: the heart beats
of pilots in normal, manned flights went from 70-80 per minute to 130-140
during the remotely piloted drop tests.
|The Highly Maneuverable Aircraft Technology test model (HiMAT), shown during a test flight. A modular design allowed engineers to test a variety of wings, control surfaces, and different structural materials.|
The remotely controlled flight tests were controversial. Extensive ground support systems were nearly as expensive for remote flight operations as they were for manned aircraft. Still, remotely controlled flights were useful; models offered a cost-effective method for testing esoteric designs; they were obviously advantageous in dangerous flight maneuvers. The positive factors were convincing as NASA and the military services pondered exotic configurations and materials of combat planes for the 1990s and beyond. The logic for a test vehicle like the HiMAT was unusually strong.
The HiMAT structure itself was composed of various metal alloys, graphite composites, and glass fibers. It had sharply swept wings, winglets, and canard surfaces --considered aeronautically avant garde when the first plane flew in 1978. Carried aloft by a B-52, the HiMAT was remotely --and safely-- flown through a series of complex maneuvers at transonic speeds. The HiMAT was designed as a modular vehicle so that wings, control surfaces, and structural materials could be evaluated at a fraction of the cost of building a full-sized aircraft. The HiMAT's changing configurations suggested the possible shapes of aircraft to come.
While the HiMAT continued to test alternative design ideas, flight test specialists nonetheless recognized the persistent value of full-sized manned aircraft. The result was the Grumman X-29, a plane whose dramatic configuration matched that of the HiMAT. The X-29 had a single, vertical tail fin and canard surfaces --not unique in the 1980s. What made the X-29 so fascinating was its sharply forward-swept wings.
The forward-swept wing had precursors in German designs of World War II. In 1944, Junkers put such an experimental jet into the air--the JU-287. The war ended before extensive flight tests could be carried out, but the JU-287 quickly revealed one of the major problems of any swept forward design: structural divergence. Lift forces on wings cause them to bend slightly upward. When the wings sweep forward, this force tends to twist the leading edge upward, increasing lift and the bending motion until the wing fails. One solution was to keep the wing absolutely rigid, but conventional metal construction made such wings so heavy they were impractical. Although swept forward wings occasionally appeared on various aircraft in the postwar era, construction and weight problems proved intractable. The solution appeared in the form of composites, affording wings of light weight but high strength.
Grumman had submitted an unsuccessful HiMAT design, which ran into severe wing-root drag problems. A forward-swept wing seemed to offer answers, and the company had quietly pursued the idea. NASA also became interested, and the DoD eventually agreed to support a radical new design. NASA became responsible for technical support and flight testing. In 1987, the plane was officially announced as the X-29, the first new "X" aircraft developed by the United States in more than a decade. The fuselage took shape very quickly, since the forward section came from a Northrop F-5A. Landing gear came from the General Dynamics F-16A, and the engine was adapted from a General Electric power plant developed for the McDonnell Douglas F-18 Hornet. At first glance, the X-29 seemed a sorry aeronautical compromise, merely incorporating bits and pieces from other planes. But its wings and related design elements made it truly unique. Moreover, it was highly unstable.
When the X-29 made its first flight in 1984, the forward-swept wings
and canard surfaces were its most distinguishing characteristics. In swept
back wings, controllability became a problem as increasingly turbulent
air flowed over the wing tips and tail surfaces. The X-29's wing tips,
however, were always moving in comparatively undisturbed air, enhancing
controllability at high speeds, and the canard surfaces also operated in
an air stream much less turbulent than that around the tail. The rigid
wing of the X-29 owed much to composites and the way they were layered
in relation to the angle of the wing and aerodynamic stresses, overcoming
the tendency to structural divergence.
|With its swept forward wing and composite construction, the X-29 offered weight and drag reduction of as much as 20 percent compared to conventional design and fabrication methods.|
Among the electronic advances of the X-29, the most fascinating related to its inherent instability. Most planes were built to be stable in flight, returning to straight and level flight if diverted. In a dog fight, such placidity could be fatal. The F-16 jet fighter was built to be about 5 percent unstable, but the X-29 was built to be about 35 percent unstable. This extreme instability was more than any pilot could manage, so a trio of flight computers were developed to keep the plane under control while allowing the pilot a remarkable latitude in terms of maneuverability. At a rate of 40 times per second, the computers analyze the plane's attitude and decide what is necessary to keep the plane under control while responding to the pilot's inputs. This allows for some unusual flight maneuvers which could contribute to more agile combat planes in the future. For one thing, the X-29 could "levitate" in flight --climbing while maintaining a straight and level attitude.
Exotic experimental military planes represented only one of several
areas of NASA's study. During the 1970s, the general aviation sector became
increasingly robust. Most Americans knew little about this remarkably diverse
segment of American aviation, which included all aircraft except those
flown by commercial airlines and the armed services. There were about 2400
scheduled airliners in service during the 1970s and 4300 in the 1980s,
while the general aviation fleet climbed from 150,000 to 220,000 aircraft,
ranging from propeller-driven single engine planes to multimillion dollar
executive jets. Sales of general aviation aircraft represented a significant
contribution to America's favorable balance of payments, since 90 percent
of the world's fleet of general aviation types originated in American factories.
Given the scope of general aviation operations in the United States and
the significance of American domination of the world market for this sector,
NASA's attention was probably overdue when the agency began comprehensive
studies during the late 1970s. Results came very quickly as more than a
dozen production and prototype designs incorporated features derived from
relevant NASA studies.
|Winglets were incorporated into the design of the Learjet model 55 (photo courtesy of Gates Learjet Corporation).|
One distinctive hallmark of NASA's general aviation investigations was
the wingtip winglet, a device to smooth out distorted air flow, resulting
in improved wing efficiency and enhanced fuel economy. During the 1980s,
a number of high performance business jets, such as the Learjet, as well
as late-model transports built by Boeing and McDonnell Douglas used this
innovation. The agency also developed a new high performance airfoil for
general aviation; the GAW-1. A separate research effort went into stall/spin
problems, using radio-controlled scale models as well as several different
full-sized operational aircraft. There were additional programs to probe
exhaust and engine noise, engine efficiency, and the use of composites.
A special investigation of crash survivability tested the airframes of
planes as well as injuries to passengers, represented by carefully instrumented
anthropomorphic dummies. A huge drop tower let the test planes plunge onto
a typical runway; test results were useful to many aviation industry firms,
including manufacturers of aircraft seats, seat belts, and body restraint
|In Cooperation with the Federal Aviation Administration, crash tests were aimed at developing better protection for pilots and passengers in general aviation aircraft. Crash tower and damaged plane (inset).|
Satellites and Space Science
During the 1970s, the number of American payloads put into space by rocket boosters diminished as mission planners waited for the shuttles to become operational. When the shuttles began flying with payloads in the 1980s, this did not mean that NASA's expendable rocket launches ceased. Several rocket launches had already been scheduled, and NASA also intended to maintain this capability as a backup through the mid-1980s. NASA boosters orbited a variety of communications and environmental satellites as well as several spacecraft involving space science. Moreover, the audacious Voyager continued its richly rewarding "grand tour" of the outer planets. Shuttle launches may have gotten the lion's share of news coverage, but rocketed payloads continued to demonstrate their share of utility and value in space exploration.
Meteorological satellites and other Earth-oriented space craft expanded their essential roles in contemporary society. During 1981, another Geostationary Operational Environmental Satellite (GOES-5) went into Earth-synchronous orbit. In addition to expanded hurricane observations in the Caribbean zone, GOES-5 tracked Gulf Stream currents for fishermen and others with marine interests, provided invaluable data for weather-casters, and warned citrus growers about potentially crop-killing frosts. The National Oceanic and Atmospheric Administration (NOAA) not only supplied vital data on ocean temperatures and wave patterns with NOAA-7; the multi-mission spacecraft conducted a variety of atmospheric and tidal measurements while monitoring solar particle radiation in space, alerting manned space missions and commercial aircraft of potentially hazardous conditions.
This network expanded with the launches of GOES-6 and NOAA-8 in 1983. The latter joined a space-based search and rescue system cooperatively operated by the United States, France, Canada, and the Soviet Union. Known as the Sarsat-Cospas network, the satellites of the participating countries could pinpoint the locations of emergency beacons aboard ships and aircraft in distress. Within a few months of its becoming operational, the rescue network had saved some 60 lives around the globe. Landsat-4, launched in 1982, experienced transmission failures, so Landsat-5 took over during 1984, continuing vital coverage for forestry, agriculture, mineral resources, and other uses. Also during the 1980s, NASA launched a series of new Intelsat communications satellites to replace older models in geosynchronous orbits above the Indian, Pacific, and Atlantic oceans.
Nonetheless, space science payloads and planetary probes continued to be the most dramatic performers. Following the encounter of Voyager 1 with Saturn in 1980, Voyager 2 made an even closer pass in the summer of 1981. These visits turned up considerable new information on Saturn's rings, moons, and weather systems, posing a number of new questions for planetary scientists. Continuing analysis of Pioneer Venus 1 also seemed to raise as many new issues as it closed. Launched in 1983, the Infrared Astronomical Satellite was a joint project of NASA and scientific centers in the Netherlands and Great Britain. During its 10-month lifetime, the international satellite detected new comets, analyzed infrared signals from a number of new galaxies, and yielded data that suggested many of them may be merging or colliding with each other.
Planetary probes continued to turn up surprising insights into the nature of our solar system. Four and a half years after uncovering a wealth of new data on Saturn and its spectacular rings, Voyager 2 approached Uranus in January 1986. By the time the intrepid Voyager completed its flyby, the spacecraft had revealed more information about the planet and its company of moons than observers had learned since its discovery by the English astronomer William Herschel over 200 years ago.
The spacecraft's arrival represented something of a tour de force for the JPL, managers of Voyager's aptly named "Grand Tour of the Solar System." JPL's navigators had to place the spacecraft within less than 200 miles of a point between the planet's innermost moon, Miranda, and the planet's rings. Having traveled 1.8 billion miles from Earth, Voyager 2 now whipped toward its goal at 50 times the speed of a pistol bullet. Commands from JPL to Voyager took 2 hours and 45 minutes to arrive. Unless the JPL crew did everything correctly, Voyager 2 might miss the gravitational sling from Uranus to send it on towards its rendezvous with Neptune in 1989. More important, engineers had to know the exact location of the Voyager so that its cameras would record something planetary instead of the infinite blackness of space. "That feat," explained a reporter for the National Geographic, "is equivalent to William Tell shooting an arrow in Los Angeles and hitting an apple in Manhattan." Many potential glitches were avoided, such as breaking into the onboard computer programs to fine tune the thrusters; commandeering another backup computer to improve the rate of image processing; and dispatching further signals to help Voyager perform in a colder, darker environment than was the case for its Saturn flyby.
There were other snarls as well, but Voyager 2 carried on superbly, turning up evidence of 10 new moons besides the five known orbs circling Uranus. Miranda, the smallest of the five, proved especially dramatic with a tortured surface that included an escarpment 10 times deeper than the Grand Canyon. The various moons represented a geological showcase, with mountains up to 12 miles high, plains dotted with craters, and sinuous valleys that may have been gouged out by glaciers. Voyager 2 also captured other curiosities about Uranus, including its offset magnetic field, fascinating ultraviolet sheen called an "electroglow," and erratic atmospheric patterns. Another mission to Uranus might be decades, or even centuries away. But the Voyager's legacy promised to give scientists and astronomers considerable data to ponder in the meantime.
At liftoff, the Shuttle looked and sounded like an oversized rocket booster with wings. Power for the launch came from a combination of propulsion systems. A pair of solid-fuel booster rockets straddled a huge propellant tank filled with liquid hydrogen and liquid oxygen; the Shuttle itself perched atop the cylindrical walls of the propellant tank, which fed the trio of Space Shuttle main engines mounted in the Shuttle's tail. During the initial ascent phase, all five propulsion systems drove the Shuttle upwards. Following burn-out of the solid-fuel boosters, the empty casings separated from the external tank and parachuted back to Earth, where they were recovered from the ocean, refurbished, and packed again with segments of solid fuel. The Shuttle's liquid-hydrogen main engines continued to fire, drawing propellants from the external tank. When the tank was empty, it too was jettisoned and destroyed by intense heat during its descent through Earth's atmosphere. A pair of maneuvering engines plus batteries of small rocket thrusters on the Orbiter refined its orbital path as needed and provided maneuvering capability during the mission.
Compared to the Apollo spacecraft, the Orbiter was huge, with a length of 120 feet and a wingspan of 80 feet. As many as seven crew members could live and work in the flight deck area, and the cargo bay represented an additional payload or workspace area measuring 60 feet long by 15 feet in diameter. The Shuttle was designed to carry payloads of 65,000 pounds to orbit at an attitude of 230 miles (smaller payloads allowed orbits of up to 690 miles), return to Earth, and land with payloads of 32,000 pounds (such as a malfunctioning satellite). NASA contended that the ability to reuse the booster rocket casings and the ability of Orbiters to make repeated missions made the Space Shuttle an extremely cost-effective space vehicle for years to come. Because of all the tiles on the Orbiter, personnel associated with the program often joked about the "flying brickyard," but there was great enthusiasm about the Space Transportation System, or STS.
Although launches occurred at the Kennedy Space Center, and plans called for most Orbiter flights to finish there on a special landing strip three miles long, contingencies allowed for alternative landing sites at Vandenberg Air Force Base and Edwards Air Force Base in California, at White Sands, New Mexico, and at selected emergency runways around the world. In any case, the first few landings were planned for the broad expanses of the dry lake at Edwards; the Orbiter would be carried back to KSC from any remote site atop the specially modified Boeing 747 ferry aircraft. There were only five landings at Kennedy Space Center before a blown nose wheel tire at the end of the 16th (51-D) mission shifted all subsequent touchdowns to Edwards. Some earlier flights had been diverted from Kennedy because of weather; the Boeing 747 transporter definitely proved its value in returning Orbiters from Edwards, White Sands, and Vandenberg. Following the nose wheel incident, engineers planned changes for Orbiter landing gear as well as improvements to the Kennedy landing site.
Concerns about tiles and engines kept the first Orbiter for flight missions, the Columbia, grounded at KSC for nearly two years. In the meantime, other Shuttle crews kept their flying skills sharp by participating in further drop tests of the Enterprise and by training flights in a Grumman Gulfstream modified to imitate an Orbiter's landing characteristics. Crew members and trainees practiced experiments and other tasks in a microgravity environment through long training missions in a converted Boeing C-135 transport. These missions also tested theories about the nature of nausea ("motion sickness") caused by disorientation in space--a severe problem for crew members during long space missions. The plane would fly high, arching parabolas in the sky, giving trainees several seconds of "weightlessness" at the top of each stomach-churning climb. The training missions might last several hours-repeated climbs, nose-overs, and rapid descents before the next upward surge. For those aboard the plane, all this could be either highly exhilarating or very loathsome. Officially, NASA's C-135 was designated the Reduced Gravity Aircraft; unofficially, hapless trainees dubbed it the "vomit comet," "barf buzzard," and "weightless wonder."
Finally, long hours of flight training and grueling sessions in electronic simulators came to an end. The Columbia's flight crew, astronauts John Young and Robert Crippen, joked that they had spent so much additional time in the electronic simulators that they were "130 percent trained and ready to go." Their inaugural flight was set for 10 April 1981. But the Columbia mission, like others to follow, was scrubbed at the last minute on a technicality. Two days later, the countdown for Columbia matched a day of perfect weather at KSC, and the Space Shuttle thundered off into space, boosted by 7 million pounds of thrust from its solid-fuel rockets and liquid-hydrogen engines.
Reaching an altitude of 130 nautical miles, the Columbia's crew settled into orbit for a two-day mission. The Orbiter carried no cargo except an instrumentation package to record stresses during launch, flight, and landing, plus a variety of cameras. One of these, a remote television camera aboard the Orbiter, revealed gaps around the tail section, where some tiles apparently worked loose during launch. As the crew prepared for descent back to Earth, mission controllers were quietly concerned, worried that other tiles in critical areas along the Orbiter's underside might have fallen off as well. At a blinding speed of Mach 24, Columbia began its searing reentry back into Earth's upper atmosphere, where the intense heat of atmospheric friction built to over 3000º F. There were some anxious moments as the plummeting spacecraft became enveloped by a blanket of ionized gases that disrupted radio communications. At 188,000 feet, as the Columbia slowed to only Mach 10, mission control heard a welcome report from Crippen and Young that the Orbiter was performing as planned. A long, swooping descent and a series of planned maneuvers bled off excess speed and brought the spacecraft in over the Edwards area. Parked in cars, jeeps, and campers all around the edge of the landing area, an estimated 500,000 people had come to observe the Shuttle's return. The sharp crack of a sonic boom snapped across the desert, and the crowd soon saw the Columbia, now slowed to about 300 MPH, make its final descent and touchdown, a true, "spaceliner" symbolizing a new era in astronautical ventures.
For all its teething problems, the Shuttle performed remarkably well through five years and 24 successful missions. Inevitably, there was some fine tuning and reworking of numerous tiles before a second launch of Columbia in November, the first spacecraft to return to orbit. During 1982, three more missions marked the end of flight tests and the beginning of missions to deploy satellites. The next year, four additional missions included three in the new orbiter, Challenger, ending on Columbia's flight with the ESA's "Spacelab" aboard. There were six crew members, a record number for a single spacecraft, including Ulf Merbold, a German who represented the ESA. These flights in 1983, which counted America's first woman in space (Sally Ride) as well as the first black American (Guion Bluford), not only launched additional American and international payloads, but also significantly increased activities in space science, particularly with the Spacelab mission. To deploy satellites from the cargo bay, the crew relied on a unit called the Propulsion Assist Module, or PAM, introduced on the STS-5 mission in 1982. In the payload deployment sequence, the remote manipulator system lifted the satellite out of the Orbiter cargo bay. The Orbiter then maneuvered away; the PAM attached to the satellite automatically fired about 45 minutes later boosting the payload higher. The organization owning the satellite then took over, using thrusters on the satellite to circularize its orbit, checking out its systems, and making the satellite operational. Although the PAM booster was augmented by other systems, many payloads could be left in orbit after simply lifting them out of the cargo bay with the remote manipulator system.
The orbiter Discovery joined the fleet in 1984, and Atlantis followed in 1985. The demographics of the orbiter crews reflected growing diversity, encompassing more women, Canadians, Hispanics, Orientals, assorted Europeans, a Saudi prince, a Senator, E. J. "Jake" Garn, and a Congressman, Bill Nelson. The various missions engaged astronauts in extended extravehicular activity, such as untethered excursions using manned maneuvering units. In Mission STS-11 (41-C) in 1984, an astronaut using one of these units assisted in the first capture of a disabled satellite, the Solar Maximum payload (Solar Max), followed by its repair and redeployment. The mission also had the task of placing a new satellite in orbit. Scheduled for deployment was the Long Duration Exposure Facility, a 12-sided polyhedron measuring 14 feet in diameter and 30 feet long. It carried several dozen removable trays to accommodate 57 experiments put together by some 200 researchers from eight countries. After being lifted out of the Challenger, the big structure was to stay in orbit for a year, awaiting its return on a different Shuttle flight.
For the crew aboard Challenger, the biggest task was the first planned repair of a spacecraft in orbit. The Challenger's thrusters boosted it 300 miles higher to intercept the Solar Max satellite. After some difficulties, due to the satellite's tumbling motion, it was finally stabilized and cranked down into the cargo bay by the remote manipulator system (RMS). After a night's rest, George Nelson and James van Hoften donned space suits and went to work on the balky satellite, replacing a faulty attitude control module and some electronic equipment for one of its instruments. Sent back into orbit, the Solar Max's repair job in space saved millions of dollars. Later the same year, during STS-14 (51-A), the crew of Discovery had to retrieve a pair of errant satellites placed in improper orbits by faulty thrusters. Although the Canadarm managed to capture the satellites, they would not drop into the cradles in the cargo bay for their return to Earth, and the mission specialists had to manhandle each one aboard before closing the cargo bay doors. These missions conclusively demonstrated the Shuttle's ability to recover, repair, and if necessary, refuel satellites in orbit. The DoD also made two classified missions in 1985.
Mission STS-22 (61-A), in October 1985, represented the fourth Spacelab flight and was notable for its eight-member crew-- requiring the eighth person to sleep aboard the Spacelab itself. Most significant was the special role of the West German Federal Aerospace Research Establishment, which managed the orbital work in which the Spacelab mission specialists carried out experiments in materials processing, communications, and microgravity. It was a highly successful mission, with only one memorable drawback. Aboard the Spacelab was a new holding pen for animals that contained two dozen rats and a pair of squirrel monkeys. The crew soon complained to controllers that the animal quarters needed modifications for any future flights. Food bars for the rats began to crumble, so that loose particles of rat food began floating around the Spacelab. Worse, some waste products from the rats also began to litter the Spacelab's atmosphere leading to pointed, scatological comments from the disgruntled crew.
Continuing missions carried a variety of American as well as international scientific experiments. One involved electrophoresis, in which an electric charge was used to separate biological materials; the goal in this case was the production of a medical hormone. Additional experiments emphasized vapor crystal growth, containerless processing, metallurgy, atmospheric physics, and space medicine, among other areas. The payload manifests for most missions were recognizably similar, listing satellites, experimental biomedical units, physics equipment, and so on. The manifest for STS-16 (51-D) in 1985 had a decidedly different quality, including a pair of satellites along with a "Snoopy" top, a windup car, magnetic marbles, a pop-over mouse named "Rat Stuff," and several other toys, including a yo-yo. For die-hard yo-yo buffs, a NASA brochure reported that the "flight model is a yellow Duncan Imperial." The news media gave considerable attention to the whimsical nature of the Toys in Space Mission, although the purpose was educational. The toy experiments were videotaped, with the astronauts demonstrating each toy and providing a brief narrative of scientific principles, including different behaviors in the space environment. The taped demonstrations became a favorite with educators--and the astronauts obviously delighted in this uncustomary mission assignment.
Despite occasional problems, Shuttle flights had apparently become routine--an assumption that dramatically changed with Challenger's mission on 28 January 1986.
On the morning of the flight, a cold front had moved through Florida, and the launch pad glistened with ice. It was still quite chilly when the crew settled into the Shuttle just after 8:00 A.M. Many news reports remarked on the crew's diversity; seven Americans who seemed to personify the nation's heterogenous mix of gender, race, ethnicity, and age. The media focused most of its attention on Christa McAuliffe, who taught social studies at a high school in New Hampshire. She was aboard not only as a teacher but as an "ordinary citizen," since Space Shuttle missions had seemed to become so dependable. Scheduled for a seven-day flight, the Challenger also carried a pair of satellites to be released in orbit.
NASA officials, leary of the icy state of the Shuttle and launch pad, waited two extra hours before giving permission for launch. When the Shuttle's three main engines ignited at 11:38 A.M., the temperature was still about 36º F, the coldest day ever for a Shuttle liftoff. After a few seconds, the solid-fuel boosters also ignited, and the Challenger thundered majestically upward. Everything appeared to be working well for about 73 seconds after liftoff. At 46,000 feet in a clear blue sky, the Shuttle was virtually invisible to exhilarated spectators at Cape Canaveral, but the telephoto equipment of television cameras captured every moment of the fiery explosion that destroyed the Challenger and snuffed out the lives of its crew. In the aftermath of the tragedy, stunned government and contractor personnel took action to recover remnants of the Shuttle and to begin a painstaking search for answers.
Answers were essential, because the three remaining Shuttles were grounded while the cause of the Challenger explosion was identified and corrected. Until that time, the United States could not put astronauts into space or launch any of the numerous satellites and military payloads designed only for deployment from the Shuttle cargo bay. Moreover, construction of the planned space station in Earth orbit relied entirely on the Shuttle's cargo capacity.
Detailed analysis of photography and Shuttle telemetry pointed to a joint on the right solid booster. It appeared that a spurt of flame from the joint (which joined fuel segments near the bottom of the booster) destroyed the strut attaching the booster to the bottom of the liquid hydrogen tank and burned through the tank itself. The tank erupted into a fireball, and the explosion blew apart the Challenger. Next, investigators had to understand the reasons for the faulty joint.
In the meantime, President Reagan appointed a special commission to conduct a formal inquiry--the Rogers Commission, named after its chairman, former Secretary of State William P. Rogers. The Rogers Commission discovered that NASA had been worried about the booster joints for several months. The specific problem involved O-rings, circular synthetic rubber inserts that sealed the joints against volatile gases as the rocket booster burned. It was believed that the O-rings lost their efficiency as boosters were reused; their efficiency was even less in cold weather. The Rogers Commission further discovered that NASA and managers from Thiokol, suppliers of the solid fuel boosters, had hotly debated the decision to launch during the night before Challenger's fatal flight.
The Rogers Commission report, released in the spring of 1986, included an unflattering assessment of NASA management, calling it "flawed," and recommended an overhaul to make sure managers from the Centers kept other top managers better informed. Other criticisms not only resulted in a careful redesign of the booster joints but also led to improvements in the Shuttle's main engines, a crew escape system, modified landing gear, alterations to the landing strip at Kennedy Space Center, and changes for a host of aspects in Shuttle operations. NASA originally planned to resume Shuttle flights in the spring of 1988, but nagging problems delayed new launches through the summer.
In the wake of Challenger's loss, other changes occurred. Some realignment would have occurred in any case, since NASA Administrator James Beggs, indicted for fraud and later completely exonerated, had vacated the position in December 1985. At the time of Challenger's loss, an interim leadership was in place; in the aftermath of Challenger, James C. Fletcher returned to NASA's helm again. But loss of the Shuttle colored many subsequent senior management reassignments in NASA, along with a reorganization of contractor personnel. Even though President Reagan authorized construction of a new Shuttle for operations by 1991, the existing fleet of three vehicles remained inactive for over a year and a half, severely disrupting the planned launch of civil and military payloads. For some scientific missions, desirable "launch windows" were simply lost, and other missions, rescheduled sometime in the future, were severely compromised in terms of scientific value. In the case of the Space Shuttle program, NASA had not only stumbled, but was left staggering.