T ECHNOLOGY Heated Debates A History of the Development of the Space ShuttleÕs Thermal Protection System: 1970-1981

By BRIAN WOODS tioners may strive to create order, sys- intense heat induced by atmospheric tem and control, through rational deci- drag on re-entry attracted such visible sion-making, technological develop- controversy because its solution was INTRODUCTION ment is a diverse, capricious, contradic- inextricably bound-up with the design tory and messy process. Authors in the of other major elements of the Shuttle. A documentary on the Columbia dis- both the history and sociology of sci- Airframe configuration, structure and aster, recently aired on British ence and technology have shown that materials could not be divorced from Television, concluded that the accident scientific knowledge and technological the selection of materials and structure was the result of Òflawed design.Ó In a artifacts and systems have to be treated of the thermal protection system. similar vein to commentary that fol- as socio-historical products: that the Equally, the weight and distribution of a lowed the Challenger disaster in 1986, definition and creation of an object is thermal protection system could have Nigel Henbest and Heather CouperÕs also the definition and creation of its adverse effects on the design of the documentary located the causes of this socio-technical context. To build and propulsion system.3 Òflawed designÓ and so by implication operate large complex technologies like NASA and its contractors explored the accident itself, in the technical com- the Shuttle, the protagonists have to four principal thermal protection design promises that emerged from the politi- enroll a variety of things, organizations concepts in early 1970: replaceable cal battles between NASA and the and individuals into a range of associa- ablator panels; metallic heat shields; Nixon Administration during the 1969 tions and negotiations that are continu- non-metallic materials; and carbon-car- to 1972 period. ally being enacted and re-enacted.2 The bon hot structures. Although pertinent, Henbest and aim of this paper then, is not to find Ablator technologies had been CouperÕs mistake was to separate poli- fault or to lay blame, but in light of the developed and utilized on the Mercury, tics from technology: to place politics recent Columbia disaster and as a guide Gemini and Apollo programmes. on the outside where it impinged on and to future commentary about it, to look Essentially an ablator heat shield was a was detrimental to technological back at the development of its thermal sacrificial outer layer that would burn progress. This led them to state that had protection system and reveal both the up on re-entry. The concept employed NixonÕs Administration allowed NASA difficulties and the socio-technical materials that had almost no ability to to build its original two-stage Shuttle processes that were involved in its cre- transfer heat, but would turn white hot, design, such a catastrophic failure ation. char and then melt away without trans- would not have occurred. Such state- mitting energy into the primary struc- ments, as sociologist Bruno Latour TECHNOLOGY AND CHOICE ture. Although the development of a rightly points out, Òsay nothing.Ó They low-density ablator system for Shuttle are simply tautologies that are Òfeasible The starting point of any history of application would be uncomplicated only at the end of the roadÓ long after technology is with the exposure of and workable, engineers at the Ames history has distinguished success from choice and controversy. In relation to Research Center did not regard it as failure.1 the ShuttleÕs thermal protection system, feasible unless some of the design To understand the dynamics of one Shuttle observer noted in 1970 that: requirements imposed were relaxed. An technological change and in so doing, ÒIf there is any clear cut lack of agree- expensive and complicated refit of the come to know our machines, it is nec- ment among those planning the Space orbiterÕs thermal protection system essary to dispel the myth that the tech- Shuttle, it is in the area of thermal pro- after every flight was not in harmony nological is independent from the tection.Ó The problem of shielding the with the Shuttle discourse on economic social. Although technological practi- orbiterÕs primary structure from the and routine access to space. The Office

Q U E S T 10:3 2003 39 of Manned Space FlightÕs requirement that the Shuttle system perform routine- ly over 100 missions with a cost-effec- tive level of refurbishment and mainte- nance placed a heavy demand on the design of a thermal protection system. The inter-related nature of the thermal protection system went further than its influence on other subsystems. The problems and solutions associated with thermal protection were integral to the overall justification of the programme. Without a reusable thermal protection system, the Shuttle programme was in grave danger of not being able to rationalize itself. Nevertheless, Ames continued its research into ablator tech- niques in case a backup would be required.4 Repeatedly withstanding the ther- The Space Shuttle Columbia glides down over Rogers Dry Lake as it heads for a landing at Edwards Air Force Base at the conclusion of its first orbital mission. mal environments of re-entry was the Image courtesy of NASA key determinant of a thermal protection backed with micro-quartz insulation, repeatedly exposed to high tempera- system design. Coupled with this were except for the rudder, which was made tures, which could have a detrimental other induced environments within of Inconel-718. Thus, in the early phas- influence on aerodynamic stability. which the system had to perform, such es, design emphasis was on a thermal Overall, metallic concepts were com- as acoustic loads, structural deflections protection system that was an integral plex. Design features to minimize ther- induced by aerodynamic loads, the part of the load bearing structure, pro- mal distortion, intricate panel-to-panel extreme heat and radiation of the Sun, viding commonality between materials joints, as well as the additional insula- the extreme cold of space, and the nat- for airframe structure and thermal pro- tion blanket that would be required to ural environments on Earth, such as tection and with a minimum reliance on protect the primary structure of the salt, fog, wind and rain; and because the exotic materials.6 orbiter, all conspired against a metallic thermal protection system was to cover Nonetheless, a perception pre- thermal protection system.7 the exterior of the vehicle, it also had to vailed at the Office of Manned Space In contrast to the complexity of the provide an acceptable aerodynamic sur- Flight that all the metallic heat shield metallic systems, the non-metallic heat face.5 concepts possessed some significant shield concepts appeared to possess the Due to the inter-related nature of drawbacks. Many of the metallic mate- advantage of design simplicity. the thermal protection system, most rials required coatings, such as Lockheed Missiles and Space Com- contractors involved in Space Shuttle Sylvania R-512E, to provide oxidation panyÕs early Space Shuttle proposal had proposals exhibited a tendency towards protection. Application of the coatings an orbiter constructed from convention- combinations of metallic materials in would have to be so thorough, both al aluminum with a thermal protection their design proposals. McDonnell inside and outside (including fasteners), system comprised of titanium on the Douglas and Martin Marietta proposed that complicated inspection techniques upper surfaces and its proprietary silica a titanium alloy hot-structure for the between each flight would negate the system, called LI-1500, on the lower wings and fuselage, with the lower sur- advantages of commonality. Although surface. The silica system captured faces covered with columbium shin- superalloys that did not require any NASAÕs attention. Composed of tiles gles. The contractors proposed a cobalt coatings, such as nickel chrome fabricated from 99.6 percent pure superalloy for the control surfaces and (TDNiCr), were also on the agenda as amorphous silica fibers derived from the vertical tail was to be made of a they could withstand temperatures up to common sand, the system had the nickel superalloy. North American 2,400 degrees F, the production rate of potential of offering a low density, low Rockwell also adopted a radiant heat TDNiCr (around 10,000 pounds per maintenance, reusable thermal protec- shield configuration constructed of var- year in 1970) was not sufficient to meet tion system that could be installed on a ious metallic superalloys including Shuttle demands. In addition, superal- conventional airframe. While engineers columbium-129Y, Haynes-188 and loys also showed a tendency to produce recognized that a major development Inconel-718. Grumman/BoeingÕs de- a rippling effect over the surface when programme would have to be undertak- sign consisted of metallic panels

Q U E S T 10:2 2003 40 en to bring the non-metallic materials strengthen the material to levels com- lower trajectory, but the silica system out of the laboratory to a state of high patible with the predicted thermal demanded that the initial entry angle of production and vehicle application, the stresses of re-entry; thus Lockheed, the attack should be as high as possible significant weight savings and inherent contractor working with silica, won the (around 30 to 50 degrees) to minimize design simplicity influenced NASA to contract to supply the baseline material re-entry heating. To reduce re-entry favor it as the primary material for the for the orbiterÕs thermal protection sys- heating and thus increase the lifespan of orbiterÕs thermal protection system.8 tem in June 1973.9 the thermal protection system, NASA From 1970 to 1972, two non- Although the Office of Manned and the Air Force arrived at a compro- metallic reusable materials were under Space Flight favoured the silica system, mise position whereby the Office of investigation by NASA: a silica-base this design decision conflicted with a Manned Space Flight chose an angle of material (SiO2) and a mullite (3A12O3 programmatic decision dictated by the attack profile of 40 degrees for all mis- SiO2). The various NASA Centers Air Force. During the design phase, the sions not requiring the high cross- working on the thermal protection sys- Office of Manned Space Flight adopted range.10 tem initially expected mullite to exhibit a delta wing planform to produce a high For the wingÕs leading edge and the a higher temperature capability because crossrange of 1,500 nautical miles nose cap, carbon-carbon was the only of its higher density; however, tests either side of the orbiterÕs ground track. known material that showed potential showed that the low-density silica pos- The Air ForceÕs fiercely defended for providing reuse capability for these sessed a superior thermal performance crossrange specification imposed an high temperature areas (greater than due to the small fiber diameter material angle of attack of 30 degrees or lower 2,300 degrees F). The Office of used in its formulation. The contractors to achieve the required hypersonic lift- Manned Space Flight considered car- working with mullite, McDonnell to-drag ratio. A metallic hot structures bon-carbon a clear choice for the lead- Douglas and General Electric, failed to system would have allowed for a shal- ing-edge applications because in test conditions it appeared far more durable than superalloys. Nevertheless, signifi- cant developments in coatings to pre- vent oxidation would be necessary if carbon-carbon was to become a multi- mission material.11

TESTING AND MODEL DEVELOPMENT

The Thermal Protection Branch at NASAÕs Ames Research Center had been researching and testing reusable thermal protection materials since the mid-1960s. By 1970, it stepped this programme up, as Ames conducted tests on candidate insulation materials for the Shuttle. During these tests, two problems became evident. First, facili- ties were inadequate for accurate test- ing. The arc-jets at Ames, while able to produce the necessary high-tempera- tures, were incapable of sustained tests on large samples of heat shield materi- als; and second, because the facilities at Ames were inadequate, the Thermal Protection Branch considered that it could not analyze the results of the tests satisfactorily. Underlying the argu- ments coming from the Thermal A timed exposure of the Space Shuttle STS-1, at Launch Pad A, Complex 39, turns the space vehicles and Protection Branch in 1970 were propos- support facilities into a night-time fantasy of light. Structures to the left of the Shuttle are the fixed and the als for expansion. There were already rotating service structure. Image courtesy of NASA proposals circulating NASA in 1969 to

Q U E S T 10:3 2003 41 shut Ames down. Larger facilities, sileÕs structure, that can melt or at the behind them lay a fairly mature disci- more researches and a greater role in very least severely damage the vehicle. pline on the construction and flight the Shuttle program would serve to Classical aerodynamic boundary-layer characteristics of aircraft design. both demarcate the work of Ames from theory had long dictated that streamline Aerodynamics had come a long way its main internal competitor, the needle-nose shapes were required to from its empirical roots at the start of Langley Research Center, and ensure reduce aerodynamic drag and thus min- the twentieth century. Experimental its continued survival.12 imize heat transfer to the vehicleÕs data, mathematical models and flight In part, Ames realized its strategy structure. However, Harry Julian Allen, experience all supported a firm founda- through the acquisition of a new 60- an aerodynamicist at the Ames tion of empirical and theoretical knowl- megawatt arc-jet facility in early 1975. Aeronautical Laboratory (when it was edge in aerodynamic design. However, Three times as powerful as any previ- part of the National Advisory supersonic and hypersonic flight ous facility, its primary task over the Committee for Aeronautics), presented (defined as the speed regime above next few years was to test the heat the radical idea in 1952, that re-entry Mach 5) brought with them major shifts resistance of the orbiterÕs thermal pro- shapes needed to be blunt. When a in aerodynamic theory. Within these tection system. Although Ames had yet blunt-nosed missile enters the atmos- new environments the characteristics of to fully define the verification test pro- phere a powerful bow shock wave fluid dynamics changed. Hypersonic gramme, it considered that materials builds up that generates much more airflow had to be viewed as compressi- characterization would involve the clas- heat outside the boundary layer than is ble as opposed to incompressible, sic practice of multiple tests to answer the case with a sharp-pointed nose, thus which was the case for subsonic aero- questions pertaining to life expectancy. dissipating the heat harmlessly into the dynamics. Aerodynamic engineers thus The Office of Manned Space FlightÕs surrounding air. In addition, because had to delve deeper into the physics and requirements had dictated that thermal the vehicleÕs resistance to the tenuous the chemistry of gases to deal with the protection material samples be subject- upper atmosphere would be at its maxi- new problems posed by re-entry, hyper- ed to 100 tests of 1,000 seconds each. mum, the vehicle would start to slow sonic and supersonic flight. Kinetic the- In addition, tests would focus on heat- down sooner within the thinner atmos- ory of gases, flow problems and radia- ing the materials up to 2,500 degrees phere, which would also transfer less tion transfer all moved to center stage.16 Fahrenheit and then raising the temper- heat to the vehicleÕs surface.14 The Air Force generated a great ature in increments of 100 degrees NASAÕs aerodynamicists had prac- deal of knowledge on supersonic and Fahrenheit until destruction.13 Although tice in the re-entry dynamics of blunt- hypersonic flight from its X-series of important, these tests provided only a nose vehicle configurations on the rocket planes. The Bell X-1 first broke limited interpretation of the environ- Mercury, Gemini and Apollo capsules the sound barrier in 1947, and the Air ment within which the thermal protec- during the 1960s. Nevertheless, inher- Force first entered hypersonic flight in tion system would operate. NASA and ent within the ShuttleÕs design lay 1959 with the X-15. The X-15 put into Lockheed engineers had to go much numerous contradictions and nowhere practice what engineers had learned farther. If the Shuttle was to come back did these contradictions reveal them- from theory and from hypersonic wind unscathed, they had to duplicate all re- selves more forcibly than in the aerody- tunnels tests. Although an Air Force entry conditions as accurately as possi- namics of the return flight. With the program, the Langley and Ames ble. advent of the Shuttle, NASAÕs aerody- Research Centers both contributed to Various aspects of re-entry heating namicists faced constructing a vehicle the development of the X-15, with phenomena had been under theoretical that had to realize many conflicting much of the work conducted on the investigation by Walter Hohmann since requirements. Not only was the Shuttle Langley 11-inch hypersonic tunnel, the mid-1920s, but the first steps orbiter going to be the largest vehicle to which could reach Mach 6.8, the towards a quantitative understanding of perform the task of re-entry, it had to approximate speed goal of the X-15. re-entry dynamics did not materialise land on a runway like a conventional From the X-15 spawned the X-20 until the 1950s, with the advent of re- aircraft. This meant designing an aero- Dyna-Soar, a plane that the Air Force entry ballistic missile technology and dynamic configuration that would func- intended to send aloft atop a ballistic advancements in supersonic and hyper- tion through the entire atmospheric rocket and then glide back to Earth to sonic flight. The air temperatures flight regime: from hypersonic through land like a conventional airplane. around the nose of a re-entering ballis- to subsonic and down to a landing Conceived in 1943, again in 1950, tic missile may reach tens of thousands velocity. Each speed regime demands designed in 1954 and adopted in 1957, of degrees. Shockwave compression quantifiable differences in aerodynamic the Dyna-Soar pushed at the envelope outside of the boundary layer surface design and those above Mach 6 were in design for hypersonic flight before generates part of this heat, but it is the largely unknown.15 the Secretary of Defense, Robert heat generated within the boundary When NASA embarked on its McNamara, finally recommended its layer, which is in contact with the mis- Shuttle development programme, cancellation in 1963.17

Q U E S T 10:3 2003 42 As North American RockwellÕs To a very large degree, engineers experiments to minimize the Space Shuttle Manager, Bastian Hello designing the Shuttle had to begin with uncertainties become major chal- reveals, the X-15 was an important pro- a blank sheet of paper. Indeed, the lack lenges in providing reliable test gram in founding a knowledge base for of wind tunnel data on the re-entry and results for the spacecraft designer the Shuttle: flight characteristics of a reusable space to go on.22 vehicle concerned both NASA and the I had a very, very stalwart Air Force when they examined the Most of the hypersonic wind tun- group of chief engineers... The issue in 1966. Del Tischler of the nel facilities that emerged during the combination of having very sea- NASA Office of Advance Research and 1950s and 1960s were located at the soned, space-wise engineers who Technology also identified Òaerody- NASA Ames, Langley, and Lewis had graduated from the X-15 and namics-structures-thermal protectionÓ Centers. Ames and Langley had both then into the Apollo program, and as major problem areas for the pro- worked on the problems associated then into Shuttle... finally led us... posed Shuttle in 1969. Again in 1974, with re-entry and had built up relative- to a winning proposal. ...Clearly the NASA Research and Technology ly large facilities for testing hypersonic the X-15 program, there was an Advisory Council raised concern over cruise and re-entry flight, whereas immense amount of experience deficiencies in knowledge of the aero- Lewis had concentrated on propulsion that was gained from that pro- dynamics of reusable launch vehicle aspects. Despite this impressive back- gram, which was a real pacesetter. when it highlighted Òinaccuracies in ground, the Space Shuttle was to pres- total heat-load prediction techniques ent one of the biggest challenges to now available to designers.Ó The col- NASAÕs wind tunnel complex. Indeed, Nevertheless, it would be wrong to lection of more accurate wind tunnel wind tunnel support involved every assume that the path from the X-15 to data thus became a major priority major NASA facility as well as assis- the Shuttle followed a straight line. On because of concerns that theory was tance from both the Air Force and the question of the X-20, Bastian Hello deficient, especially at the high angle of industry. Over the entire programme, recalled: attack proposed for the orbiterÕs return NASA employed at least 50 different flight.20 wind tunnels and clocked upward of For all I know, engineers In hypersonic wind tunnel opera- 100,000 hours (the equivalent of almost working for our team at that time tions aerodynamicists assumed that the 25 years) of wind tunnel work. Not all (1969-72) could well have gradu- air streaming by the body behaved as a of this work was devoted to the under- ated from the Dyna-Soar program perfect gas, as defined by the laws of standing of re-entry dynamics. without me knowing about it... but thermodynamics. However, in the Aerodynamic loads, structural heating, was there a guiding light that said regime of orbital re-entry speeds a stability and control parameters, flut- this is what Boeing did on the strong shock wave generated near the ter/buffet boundaries, propulsion sys- Dyna-Soar and hereÕs what they nose of the body produces very large tem integration, and the complex fac- did right and hereÕs what they did temperature and pressure increases that tors involved in controlling the separa- wrong? No. ... And I worked on... change the chemical composition of the tion of the twin solid rockets and exter- the X-24, the PRIME program, streaming air, with the oxygen and nal fuel tank, all presented problems but they were rudimentary. We nitrogen molecules dissociating and that those working in the wind tunnel were ... still using ablative materi- becoming electrically charged to form program had to solve.23 al on that thing, there wasnÕt the an ionized sheath around the re-entry In the area of thermal protection, sophistication of the reusable vehicle. At this time, long duration an important contribution came from tiles. ...But we used a very rudi- hypersonic wind tunnel tests were not the Langley 8-Foot High-Temperature mentary honeycomb and inserted possible at temperatures above 3,000 Structures Tunnel, conceived in the late ablative material in it and degrees F, which meant that vehicle 1950s because the then existing hyper- smoothed that down to the exteri- designers had to conduct intermittent sonic tunnels could not duplicate the or contours. ...But that had long testing to preserve the structural integri- structural problems encountered at been past by the time we came ty of the facility.21 these high velocities. Not completed around to Apollo. We had already until 1968, the tunnel came too late for been through ablators on the Even so, full duplication of Apollo, but it did provide ideal condi- underside of Mercury and on the reentry temperatures, pressures, tions for full-scale testing of the underside of Apollo and we also and velocities is beyond the reach ShuttleÕs thermal protection system as it understood what reusable things of terrestrial test equipment, and was large enough to test complete were on Apollo. ...So the whole partial simulation becomes a fact arrays of full sized tiles.24 thing had moved and it was a dif- of life. Assessing the adequacy of For NASAÕs aerodynamicists one ferent game.19 the simulation and designing of their most difficult problems was

Q U E S T 10:3 2003 43 selected representative locations on the orbiter and then collected data from tests on models in a wind tunnel that were scaled-up to flight conditions by correlating boundary-layer transition and turbulent heating as a function of the Reynolds number behind a normal shock.28 From these simplified models, Johnson mapped a re-entry trajectory that would be consistent with the ther- mal protection systemÕs capabilities. The orbiterÕs re-entry configuration, however, was not a true blunt re-entry vehicle, nor was it a slender flight vehi- cle. The flow dynamics would vary along the orbiter from the high entropy of a blunt-body nose flow asymptotical- ly toward a low entropy slender-body flow.29 More complex models and ana- lytical techniques were, therefore,

View of STS-1 payload bay and aft section, which shows some of the missing thermal tiles from the orbital required. maneuvering system (OMS) pods which flank the vertical stabilizer at left edge of photograph. Although the Shuttle orbiter was Image courtesy of NASA not the first winged vehicle ever to fly simulating turbulent flow in the labora- and has higher velocities close to the through the hypersonic speed regime, it tory. Understanding it was of great surface. This effect causes the turbulent was going to be the first real technolog- importance because maximum heating flow (all things being equal) to exert ical test of theoretical high-speed flight rates and material ablation would occur higher skin friction than the laminar above Mach 7. As JohnsonÕs Director when turbulent flow became fully flow and therefore cause extreme sur- Christopher Kraft recalled: established.25 As Johnson engineer face heating.27 Robert Ried, told a NASA technical Ames, Langley and Johnson tack- The ability to perform a re- conference in 1985: led the problem of simulating turbulent entry from Mach 26 to touch flows and boundary-layer transition down speeds...through the entire The phenomena of turbulent through the development of both sim- Mach number regime, particularly flow and boundary-layer transi- plified theoretical models and empirical from Mach numbers of 10 to 1, tion have been under intense evidence based on the previous experi- that was...a technical feat...which investigation for more than a cen- ence and knowledge gleaned from the nobody had ever done before; and tury with somewhat limited suc- blunt re-entry capsules of Mercury, one which there was no capability cess. This limitation is possibly Gemini and Apollo. They could do this to run (a) test (on) in the world...in measured by the anxiety which because geometrically similar bodies wind tunnels or anything else. We develops when engineers are develop identical flow and shock pat- had to do that by rope and by required to predict boundary-layer terns within the subsonic and superson- mathematics and by guessing.30 transition outside the range of ic speed regimes. Within the hyperson- 26 experimental data. ic speed regime, however, there is con- So, despite the maturity of aerody- siderable interaction between the namics, precedents did not exist to In general there are two types of boundary-layer and the shock pattern. facilitate many of the design require- boundary layers, laminar and turbulent, When this occurs the similitude ments. Requirements for the orbiterÕs and both are fundamentally different in requirements are more difficult to satis- thermal protection system dictated a character. Laminar flow takes place fy. To circumvent this problem the stan- more accurate and intricate definition smoothly in parallel laminae, free of dard technique was to introduce simpli- of re-entry heating than for any of irregular eddying motion. Turbulent fied models using data from accurate NASAÕs previous vehicles. The three flow, by contrast, contains a large num- predictions under incompressible flow dimensional geometric complexity and ber of small eddies that move in a conditions to provide predictions under the large scale of the orbiter posed a chaotic manner. As a result of the trans- compressible flow conditions using dis- greater challenge to the definition of the verse mixing of gases, turbulent flow tortions of geometry to balance distor- re-entry flow-field and subsequent tends to be thicker than laminar flow tions of velocity. Aerodynamicists thus heating than had any previous system.31

Q U E S T 10:3 2003 44 Thus, along with the development that the Manned Orbital Laboratory ing sufficient caution and care in the of theoretical models, an array of closed down, pulling the computer out review of the data. Concern soon arose instrumentation was required to recre- before the Air Force declared it surplus within the Office of Space Flight over ate boundary-layer transition from lam- and installing it at Ames. The acquisi- what steps both Johnson and Rockwell inar to turbulent flows in the laboratory. tion of the IBM 360-67 opened the door were taking to critically examine the The foundation for the definition of the for an aggressive research programme data for errors. Thus, in early 1976 the re-entry aerothermodynamics environ- by the Computational Fluid Dynamics Deputy Associate Administrator for ments was the wind tunnel test data Branch. In 1975, Ames acquired the Space Flight (Technical), Charles taken from scaled models of the orbiter, Illiac IV (a supercomputer capable of Donlan, assembled a team, which but wind tunnels, though invaluable performing 300 million calculations per included Joe Weil from the Dryden tools, had their limits. The most press- second and storing one trillion bits of Flight Research Center and members ing problem was the scaling-up of data information at a time) through more from Rockwell, to examine the issue.35 without the introduction of some error usual channels. Mark and Chapman After three days of discussion and or distortion. Although a range of tech- both saw the acquisition of Illiac as the review, Charles Donlan reported that he niques were available, such as pressur- deciding factor in establishing Ames as was Òsatisfied that Rockwell had com- izing or cooling the air in the tunnel, the NASA center for computational petent and knowledgeable people on chilling the models to cryogenic tem- fluid dynamics. Its performance was so the programÓ and that the Òdiscrepan- peratures, or using helium instead of revolutionary that Mark, Chapman and cies in data and judgementsÓ were air, complex mathematical equations Melvin Pirtle, head of the Illiac pro- being Òfreely aired between contractors were also a necessary part of the pre- gramme, argued that the relationship and government personal.Ó Although diction process.32 Complementing wind between wind tunnel testing and com- Joe Weil Òexpressed some skepticism,Ó tunnel activity, therefore, was an putational fluid dynamics was shifting about whether the variations in aerody- increase in the use of computer technol- in favour of the latter.34 namic parameters used in flight simula- ogy in computational fluid dynamics. Wind tunnel experiments and com- tions were broad enough to demonstrate Many of the engineers and managers at putational fluid dynamics nonetheless with 100% confidence the ability of the Ames were eager to enter what was then a new research field as Dean Chapman, Chief of AmesÕs Thermo- and Gas-Dynamics Division recalled:

IÕd been out of fluid mechan- ics for eight or nine years when I took over the division in 1969. When I reviewed the field and saw what computers were doing even then, it became clear to me that they could do a lot of things that I as an experimentalist never dreamed about, so I decided to press into that area.33

In 1970, the Theoretical Branch and the Hypersonic Free-Flight Branch combined to form the new Compu- 24 March 1979. Shuttle orbiter Columbia aboard a 747 jet transport touches down on KSCÕs Shuttle Landing Facility. tational Fluid Dynamics Branch. Ames, Image courtesy of NASA however, had the poorest computer facilities within NASA and both Ames worked in parallel on the Shuttle pro- flight control system to handle uncer- Director Hans Mark and Chapman gram and generated a colossal amount tainties, Donlan sided with Rockwell.36 sought to remedy this situation quickly. of data on the re-entry environment to Crucial to his decision was the role of The collapse of the Air ForceÕs Manned aid the design and fabrication of the Ames, as Donlan stated at the time: Orbital Laboratory Program left avail- thermal protection system. Indeed, able an IBM 360-67, which was imme- there was so much data that by early (Ames) is to be commended for its diately acquisitioned by Ames in a most 1976, Òdisquieting rumoursÓ had begun role in this area. (Ames) is not unusual manner. Hans Mark had Ames to circulate around NASA that only performing invaluable tests people in Sunnyvale on the very day Rockwell International was not exercis- on the (thermal protection tiles)

Q U E S T 10:3 2003 45 but serves as a technical con- about giving it a basic airframe In early 1974, the configuration of science for the heating program. stability.38 the external tank had been settled and They have developed for exam- hardware production begun, when ple, a three dimensional flow The use of a computer-controlled Ames notified Marshall and external model (unique in this field) that is flight control system permitted the tank contractor Martin Marietta that if being used to estimate orbiter required vehicle stability and handling ice was allowed to form on the external temperatures...The results indicate qualities to be artificially produced. The tank then debris caused by the vibration that the less sophisticated model- integration of aerodynamic control of lift-off could damage their thermal ling employed by Rockwell is requirements through an automated protection system. As the External Tank yielding conservative temperature system was thus of major importance in Development Manager, James Odem estimates over most of the body meeting flying quality goals in all the remembered: length.37 flight regimes. It also allowed the ther- mal protection system design to com- We were well into the design By this time, Ames was contribut- prise mainly of large flat areas, limiting of the tank when we realized just ing around 40% of the entire Shuttle curvature to smaller areas between the how fragile the insulation on the wind tunnel program in addition to its flat ones. This maximized the use of bottom of the orbiter was going to work in computational flight dynamics. uniform dimension tiles, which would be. So then, we had to come up... The Center had thus come a long way minimize both production and insula- with insulation on the tank that from its precarious position at the end tion costs.39 would withstand less than minus of 1969. 400 degrees (Fahrenheit) on one An important part of the design INTEGRATION AND side and still be above 32 degrees process was simplification. Simplifi- FABRICATION (Fahrenheit) on the outside so as cation was a fundamental principle of not to create ice.42 aerodynamic design because of the While the processes of theoretical inherent complexity and contradictory modeling and wind tunnel testing in the The no Òice/debrisÓ requirement nature of the orbiterÕs return flight tra- area of re-entry aerothermodynamics meant that both Marshall and Martin jectory. As such, the sophisticated geo- progressed, production of the orbiterÕs Marietta had to design a thermal system metric techniques of past aerodynami- thermal protection system got under- that would cover the entire acreage of cists were not appropriate solutions for way. Before full-scale production com- the tank, including all its feed lines, the orbiterÕs design. As Space Shuttle menced, however, it had become appar- brackets and anything else that was on Program Manager Robert Thompson, ent that the fragility of the proposed the outside. Several working sessions recalled: tiles presented a major systems integra- took place to evaluate various solutions tion problem with the external fuel to the icing problem, including de-icing Aerodynamic oriented peo- tank. Introduced in late 1971, the exter- sprays, thermal paints and heating blan- ple...had done a lot of work on try- nal fuel tank represented the most sig- kets, or shrouds. As engineers debated ing to shape (the) vehicle very nificant deviation from NASAÕs origi- these differing approaches, they nar- cleverly so that it had good aero- nal Shuttle design. Indeed, for Robert rowed their focus to the concept of a dynamic characteristics through Thompson, the move to an expendable spray-on-foam that could cover the the entire speed range; and itÕs a fuel tank was the single most important entire tank, including all the brackets very broad speed range because configuration decision made in the and feed lines. NASA had previously you go from hypersonic speeds Shuttle programme:40 employed spray-on-foams on the down to supersonic speeds to sub- Apollo/Saturn vehicles as cryogenic sonic speeds and the aerodynamic I think the biggest thing that tank insulators to create a suitable envi- characteristics change in those broke (the) logjam was our will- ronment that would limit propellant regimes, such that something ingness to give up on everything boil-off and maintain the fuel quality. shaped to fly good in one regime being reusable: to take the propel- Accordingly, in June 1974, Marshall isnÕt necessarily good to fly in lants out of the orbiter. Propellants and Martin Marietta selected the same another. So we avoided getting just made a mess out of trying to technology, the BX-250 spray-on-foam, into a lot of fancy shaping of the build the orbiter. You get them out for the external tankÕs thermal insula- vehicle, or a lot of variable geom- and get them in a fairly simple tion design.43 etry kind of solutions by just brute tank...and then throw that alu- Notwithstanding its advantages, by forcing our way through...We minium tank away, looked like a the end of 1974 the acceptability of actually used the control system good common sense way of BX-250 was in serious doubt. As James on the vehicle to stabilize it in going.41 Odem recalled, during ascent the lead- many cases. We didnÕt worry ing edge of the tank would have to

Q U E S T 10:3 2003 46 withstand aerodynamic heating, as line forms of the fiber, however, had a ing failures included: problems with would the area between the orbiter and thermal expansion coefficient 30 times glass coating composition; processing the tank: greater than the amorphorous form. A cycle errors; glazing cycle errors; or crucial element of the production problems with coating distribution.48 The insulation had to both process, therefore, was the transforma- By 1975, however, NASA was suf- insulate from an ice standpoint, tion of the silica fiber from its amor- fering from budgetary problems, the but it had to withstand very high phorous form to a crystalline structure, seeds of which had been sown years temperatures also. So those two but this was not an easy procedure. earlier. Throughout 1972, the Office of are two absolutely opposing Shrinkage and distortion of the sintered Management and Budget indicated to requirements, we...literally (had silica composites impeded the forma- NASA that it was in full accord with the to) develop very light foam insu- tion of crystalline structures that would settlement over the Shuttle.49 For lations that could withstand both be acceptable to NASA. To achieve the NASA, an important part of the 1972 aerodynamic heating as well as dimensional stability dictated by settlement entailed a commitment. being a good (cryogenic) insula- Shuttle requirements, a silica fiber NASA Administrator, James tor.44 greater than 99.6 per cent pure was nec- Fletcher, advised President Richard essary.46 Nixon in July 1973: Initial solutions such as the inclu- Locating fibers with sufficient sion of an ablator material, SLA-561, purity thus became a major concern of In January 1972 when you were not acceptable to Robert tile production. LockheedÕs supplier approved the Space Shuttle devel- Thompson, leading to the introduction (Johns-Mansville) was unable to meet opment, I stated that I could con- in November 1974 a new urethane all the purity requirements and so duct the right kind of space pro- modified isocyanurate foam material sought an alternate. However, silica gramme...at a Òconstant budgetÓ produced by the UpJohn Company: fibers provided by other suppliers were (sic) of $3.4 billion...I would have CPR-421. However, towards the end of much larger in diameter than those pro- not recommended starting the 1975, Martin Marietta had to stop work vided by Johns-Mansville, which was Shuttle at a lower budget projec- on all CPR-421 activity because of tox- unacceptable. The exact diameter of the tion.50 icity problems, which by that point had fiber was of crucial importance to the become critical. Tests at the Southern tileÕs thermal performance. Lockheed, NASAÕs interpretation of a con- Research Institute, conducted during therefore, decided to intervene in stant budget was a guaranteed annual January 1976, confirmed that the CPR- Johns-MansvilleÕs production process funding level $3.4 billion, in FY 1971 421 foam contained chemical compo- and introduced extensive post-treat- dollars, during the ShuttleÕs develop- nents, which on pyrolysis could pro- ment and rigid process controls, from ment. However, the Office of duce a toxic substance referred to as the selection of the sand used in making Management and Budget did not agree trimethylol propanephosphate. Some the fiber through to the fiberizing and with this interpretation. The Office of within NASA argued that pyrolysis on cleaning process, to minimize contami- Manage-ment and Budget immediately re-entry did not present a problem, as it nation of the Òsub-standardÓ fibers and cut FletcherÕs request for a $1 billion was Òsafe to assumeÓ that the EarthÕs bring the Johns-Manville fibers up to an Shuttle reserve and they submitted atmosphere would Òdilute the products acceptable standard.47 NASAÕs FY 1973 budget in 1973 dol- of combustion tremendously.Ó Another materials problem arose lars so NASA lost any inflationary Nevertheless, Martin Marietta reformu- during the production phase of the ther- increments.51 lated a new composition, CPR-488, mal protection tile early in 1975. In the In the months that followed which did not contain the phosphate original design concept the thermal tile NixonÕs re-election, the Office of component and was acceptable to Level was going to be applied with multiple Management and Budget formulated 1 management.45 layers of borosilicate glass coatings to plans to curb the growth in federal Meanwhile, in the area of thermal prevent moisture absorption, provide spending. Having permitted heavy protection, the transition from laborato- protection against handling damage and spending in 1972, in part to assure a ry production of the silica thermal pro- provide optical property control (solar Nixon victory in the presidential elec- tection system to full production was absorption). During thermal testing tions, the Office of Management and experiencing many scale-up problems. Ames discovered that the multi-layer Budget intended to reverse policy and Control of the purity and consistency of glass coatings had a tendency to crack work towards what they regarded as the silica fibers presented NASA and or foam. Arc-jet tests at Ames revealed desirable economic goals. In December Lockheed with their first major produc- coating failures on approximately 40 1972, the Office of Management and tion problem. The silica fiber, a key per cent of the tiles when exposed to a Budget told NASA that it had to take a ingredient in the production of the tile, succession of simulated re-entry envi- major cut in its FY 1974 funding as part came in an amorphorous form. Crystal- ronments. Possible causes of the coat- of the overall budgetary squeeze.52 As

Q U E S T 10:3 2003 47 projections for FY 1975 did not appear and Budget in 1973: By 1975, the General Accounting to offer any alleviation, Fletcher Office expressed grave doubts about advised Nixon of a pending crisis. A great deal of support for the NASAÕs ability to construct the Shuttle space program in general, and for on time and within budget. Its main It will not be possible to con- the Shuttle in particular, hinges on concern was that NASAÕs budget esti- tinue to run a balanced pro- program balance. Without this mates and schedule goals appeared to gram...unless adequate funding is balance we would lose support for be overly optimistic and as a result the provided in FY 1975 and in future the remaining program in the agency might have understated its proj- years... We...assumed (with Office Congress, by the public, and by ect estimates and overstated its of Management and Budget the scientific and users communi- reserves.59 knowledge) that the reductions ties.57 In this projection, the General were only temporary, and that Accounting Office was correct. For the future yearsÕ budgets would again And a 1974 NASA position paper development of the thermal protection reach the required level. The pro- warned: system, the result was a deferral of any grams we now have under way detailed investigation into the problems cannot be sustained at the FY A fiscally imposed slippage they were encountering. Finding a solu- 1973/74 levels, nor can they be of the Shuttle development sched- tion to the cracking tiles thus had to sustained at the Office of ule by the Executive Branch for wait until 1976. Eventually AmesÕs pro- Management and Budget project- the third consecutive year may posal, to use only a single-layer glass ed level of $3.2 billion for FY well result in termination of the coating, received funding for qualifica- 1975... Either the Shuttle will have to be cancelled and with it the only future plans for US men in space, or we will have to forgo one or more of the major areas of output.53

Despite NASAÕs supplications, the agencyÕs total FY 1975 budget only just exceeded $3.2 billion.54 The combination of sustained funding cuts and emergent overruns from some of the Shuttle contractors were, by themselves, major contribu- tors to the onset of financial difficulties at NASA. With the addition of an infla- tionary crisis, NASAÕs financial diffi- culties worsened.55 With rising costs of materials and labor, many of the ShuttleÕs contractors argued that it was difficult to continue development projects with dollars that 12 March 1979. Shuttle orbiter Columbia arriving at the Orbiter Processing Facility, KSC. bought substantially less than projected Image courtesy of NASA in 1972. NASAÕs FY 1975 funding was based on a 5% inflation factor, but by program. Congress could take it tion testing in mid-1976. After a late 1974, overall levels of inflation on as evidence of an internal lengthy verification program, NASA materials stood at around 9% and in Administration intent to create an found that the single-layer coating did some areas approached 10%.56 In a push untenable development environ- not foam during production and actual- for retention of the constant budget, ment that would lead inevitably to ly provided a better match with the NASA continually advised the presi- cancellation. Or Congress could thermal coefficient of the silica insula- dency and the executive branch of the take it as a lack of Administration tion material. The superior performance political consequences of sustained determination and real commit- of the single-layer coating over the funding cuts. As NASA Administrator, ment to preeminence that would multi-layer coating in many of the tests James Fletcher, informed Roy Ash, provide an incentive to terminate ultimately persuaded NASA officials to Director of the Office of Management the program by legislative fiat.58 change the design.60

Q U E S T 10:3 2003 48 Once these two key materials prob- Lockheed had to stamp every tile with a advanced spaceship in the world could lems had been solved, full-scale pro- number, which corresponded to a pre- not even fly from California to Florida duction could begin. Technical matters, cise position on the orbiter. Rockwell without tiles falling off, then how was it however, were not the only obstruction than had to apply each tile individually, supposed make the journey into to tile production. Funding limitations check for any differences in height that space?65 Most of the tiles that were lost in 1975 resulted in a substantial modifi- might induce turbulent flows, and care- were Òdummies,Ó applied because of cation to the Shuttle programÕs sched- fully index them before they were concern about the effects of turbulence ule and deferment of further develop- ÒgluedÓ to the structure. In addition, a on the ÒactualÓ tiles fitted, but the event ment of the thermal protection system gap of no less 0.010 inch had to be severely damaged NASAÕs reputation. until the funds were available to pro- ensured between each tile to allow for With the arrival of Columbia at cure special tooling equipment. This thermal expansion and contraction and Kennedy in late March 1979, President delayed the completion of the produc- for the flexing of the orbiterÕs wing sur- Carter announced: ÒThe first great era tion facility in Sunnyvale, California;61 face during flight. The application rate of space is over. The second is about to as JohnsonÕs Director, Christopher Kraft recalled:

We made a decision to put off building the tile factory, because we didnÕt have the money. We had to put the money into the schedule and we had to develop the sched- ule...and we just decided we could wait a couple of years.62

The Sunnyvale plant contained some of the most modern manufactur- ing equipment then available, includ- ing: precision controlled kilns and fur- naces; numerically controlled milling machines; and the most up-to-date blending and slurry casting equipment. As with flow dynamics analysis, com- puters played an important role in the A Rockwell International technician mounts some of the ceramic-coated tiles on the external surface of fabrication of the thermal protection Columbia, February 1980. system. Lockheed was able to plot Image courtesy of NASA History Office orbiter configuration coordinates from a Rockwell engineering database and was slow and hindered further by the begin.Ó The statement, largely based on then convert them into computer pro- fragility of the tile material. On aver- the assurances coming from NASA, grams, which drove the numerically age, one technician applied one tile per was nonetheless premature. The ship- controlled mills that machined the tiles week.64 ment of Columbia to Kennedy was pri- into precise dimensions.63 As the planned September 1979 marily political. As one Johnson launch date approached, Rockwell Official, Herb Yarbrough, recalled APPLICATION AND found itself behind schedule with the when Columbia arrived Kennedy Òit MODIFICATION tile application. To avoid adverse pub- was not ready for delivery, but the pro- licity, NASA Headquarters decided that gram had a milestone and we had budg- By the end of 1978, application of the technicians at Kennedy could attach the et problems and not delivering on time complex array of thermal protection remainder of the tiles. So on March 24 wouldnÕt have helped that.Ó March tiles to the Shuttle orbiter Columbia 1979, Columbia was airlifted atop 1979 had been the predicted launch was nearing completion. It was a com- NASAÕs Boeing 747 to the launch cen- date for a number of years; thus getting plex process. Lockheed had formed ter with around 6,000 tiles left to install. the Shuttle to Kennedy by that date had most of the 33,000 tiles into individual- The plan did not go as intended. Many become a key objective. Yet, it soon ly specific shapes, determined by the tiles were lost during the flight from became apparent to those at Kennedy aerodynamic and aerothermodynamics California to Kennedy. As a public rela- that the vehicle was nowhere near ready data that governed the computer-con- tions exercise it was a disaster. It to fly. As Rockwell engineer (Kennedy trolled milling machines. Thus, appeared to the media that if the most Division), John Tribe, remembered:

Q U E S T 10:3 2003 49 ÒWhen the vehicle got here it wasnÕt strength of the tiles. As Space Shuttle quite early for a simpler process known finished. ...so we had a lot of work to do Program Manager Robert Thompson, as Òtile densification,Ó which involved down here, it was almost like we had to recalled: ÒOne of the things that we got coating the surface facing the orbiter finish building it.Ó66 And as Deputy into a little bit of difficulty with, we with a colloidal silica coat. This provid- Director of Space Shuttle Projects didnÕt characterize the tile materials as ed the tiles with a new surface that Management at Kennedy, Samuel thoroughly as we should have.Ó And spread the loads more evenly. However, Beddingfield, also recollected: JohnsonÕs Director Christopher Kraft having been forced into a major modifi- remembered: ÒWhen we finally got the cation of its tile application pro- Well, when the Shuttle got factory built and started producing the gramme, NASA adopted the change here and this has been kind of a tiles, we got enough tiles to run a suffi- with caution.70 Many at NASA believed tradition, an unfortunate tradition, cient statistical sample, and low and that the tile problems should never have that when the Rockwell people behold, the strength was only half what occurred and laid the blame on deliver a spacecraft down here to we thought it was.Ó Late in 1979, Rockwell. George Jeffs, President of be launched itÕs never finished. It Johnson engineers suspected that some- Rockwell International Aerospace has a lot of work to be done on it, where between 10,000 and 12,000 tiles Operations, told Aviation Week and even though they claim that itÕs were below the ÒnewÓ specifications. Space Technology: finished. Now when that one But, as the program turned into 1980, came in the tiles were a huge aerodynamic and aerothermodynamics I think itÕs a fair criticism that problem, the thermal protection data were predicting that up to 31,000 we didnÕt define the problems system tiles. We lost a lot of them tiles would need retesting.68 more clearly. ...We worked too in transit, just flying it across the The first problem Kennedy had hard on the quality of the material country. ...It ended up that we had was how to test the tiles while they alone and waited too long for the to replace almost all the tiles on were still on the orbiter. What Johnson thermal analysis while awaiting a the whole vehicle and the work came up with was a Òproof-test deviceÓ detailed structural definition. was not very well done, they had a that combined a vacuum chuck (which Perhaps it was a bit too long to lot of sloppy workers and there attached to a single tile), a pneumatic understand what the (orbiter struc- was (sic) a lot of other things that cylinder (which applied the specified tural deflections) might be and had to be tweaked. The landing load) and six pads (which would be their effects in the tiles. I am trou- gear was not working right, the attached to the surrounding tiles to react bled that we are suffering a lot of brakes were not working right. So to the load). The device would then shots at our engineering reputa- we practically rebuilt the thing stick to the orbiter, rather like a plunger, tion because of the bloody tiles, down here; so it was a long time and attempt to pull a single tile off with- and we are doing everything we after it was delivered before the in a specified load. If the tile stayed can to clean them up.71 first flight and part of it is just fixed, then it passed the test. If it came being absolutely concerned with off, then clearly it did not. Although a KennedyÕs engineers hoped that checking it out, making sure simple and effective solution, a second the data obtained from the Òpull-testsÓ everything works. But a large part problem emerged: what if the test itself would enable a relaxation of require- of it was that it just wasnÕt fin- weakened the tile? To solve this prob- ments thus reducing the reapplication ished being built. They did the lem, KennedyÕs engineers attached an number. By the end of 1979, Kennedy same thing on the Apollo space acoustic sensor to the proof-test device had pulled off and reapplied over vehicle.67 to monitor the acoustic emissions from 12,000 tiles. Originally, the densifica- fiber breakage. This involved the estab- tion process was restricted to the black Towards the end of 1979 NASA lishment of a large-scale laboratory tiles along the bottom of the orbiter, but found that it had a large problem with programme to arrive at criteria of fail- in early 1980, there was growing con- the thermal protection system. Due to ure. The program simulated the flight cern about ÒsuspectÓ white tiles on budget and schedule pressures, NASA loads over 100 missions and monitored ColumbiaÕs topside. In addition, aero- had decided to move ahead with the tile the changing acoustic signatures as the dynamic and aerothermodynamics fabrication and installation before tiles failed.69 analysis had increased the load predic- Ames had completed the final aerody- The next problem for Kennedy tions yet again. This meant Kennedy namic loads and stress analysis. The engineers was to determine what to do had to retest all the tiles for a second design of the tiles derived from the ini- with the tiles that came off. Initially, the time, including the 12,000 that had tial predictions that had emerged from ÒrepairÓ concept was to install a been through the densification these studies. As the predictions graphite sheet under the tiles to increase process.72 became more refined, however, they their adhesion to the orbiter. However, In a tremendous effort to complete highlighted a serious weakness in the Kennedy abandoned this approach the work on Columbia in time for a

Q U E S T 10:3 2003 50 November 1979 launch, NASA moved up close to a space vehicle. For the full- and time consuming, so NASA decided over 2,000 workers from Palmdale, timers at Kennedy, getting the Shuttle to select only certain locations from California, to Kennedy at a cost of over ready to fly was turning into a night- several of the most complex air flow $1.8 million. A huge complex of tem- mare, as John Tribe recalled: fields to build up a data set. To rein- porary accommodation and facilities force the analysis, Ames aerodynami- was established at Kennedy to house all Those were some black days, cists correlated the scale model tests in the workers, who were working seven ...I wondered if weÕd ever fly. It the wind tunnel with similar airflows on days a week, three shifts a day, to finish just seem like that every time we fighter aircraft. Engineers attached building Columbia. In addition, started to put things back together some of the tiles to wing sections on an Kennedy also hired every man and there would be another (modifica- F-15 and an F-104 and then flew the women in Brevard County that wanted tion), or another crisis would aircraft through flight conditions up to to work on the Space Shuttle, to work occur, so that we had to go and 1.4 times the severity of those expected with the application of the thermal pro- start taking it apart again.75 on the Shuttle.77 tection tiles, because it was such a labor The test programme, completed in intensive operation. Included in that The sheer amount of people January 1981, forced NASA Head- workforce were over 320 high school engaged in the test, densification, tile quarters to revise the first launch date graduates and college students on their removal and reapplication process, cre- for March 1981. However, the tests summer vacation.73 John Halsema ated serious food service, toilet and showed up serious flaws in the special recalled his experiences as a temporary accommodation problems during 1979 tiles. Ames engineers speculated from technician, hired to install the thermal and 1980. Kennedy had to erect a com- the data that the high pressures of protection tiles. plex of trailers outside the Orbiter ascent could lift the windshield tiles Processing Facility to support a work- from their moorings. As with all the When I started working...we force spread over three shifts working tiles, Lockheed had machined the wind- were in a big push to get the 24 hours a day, seven days a week. At shield tiles from a block of ceramic in Shuttle finished. ...We started any one time, over 200 people were such a way as to ensure that all the working a tremendous amount of working directly on or in the vicinity of fibers run in parallel to the ShuttleÕs hours...after my initial training, Columbia, a number that was far higher surface; principally because analysis we started working 12 hours a day than the facility had been designed for. had demonstrated that a parallel grain for five days a week and 8 hours a Thus, the work platform access was not orientation would minimize the heat day on Saturday and Sunday. always available for tile work so transfer to the orbiterÕs aluminium skin. ...We had to be at work at five in Kennedy had to set up jury-rigged cat- However, this grain orientation caused the morning and we got off at walks, strung up by ropes, to reach the a reduction in the tilesÕ strength because 5:45. ...I think everybody at that otherwise inaccessible areas. The of the relatively low number of vertical period of time had a real personal whole process for each tile from fibers. The first solution, therefore, was feeling about working on the removal to densification to reapplica- to machine new tiles with the fibers Space Shuttle. Most of the people tion took about 14 days. In the summer running perpendicular to the orbiterÕs that were hired temporarily here, of 1979, the average application rate, surface. This would provide strength, grew up here and so they were in with a workforce of 800, was 450 tiles but would also reduce thermal efficien- the same situation I was, they had per week.76 cy. Thus, a second solution was also (grown up) watching rockets take- As the programme moved through necessary. On further analysis, Ames off. ...All of us were young, in our 1980, it became apparent that the tile thermal engineers found that the orbiter late teens to early twenties...there problem was much more serious than window would act as a heat sink, so were a few of the old hands that had been anticipated and concern soon they decided that by bonding the part of had been technicians during the focused on the Òspecial tilesÓ around the tile that overhung the window Apollo program and they were the wing leading edge, the windshield, directly to the glass this would increase kind of the corporate memory and the undercarriage doors, the tail, and the thermal capacity of the tile.78 we got to hear what it was like tiles in other areas that did not have After two years of testing and during the big pushes during the square or rectangular shapes. These redesign, NASAÕs confidence in the Apollo era.74 special tiles were often located in areas thermal protection tiles grew and by that would endure very complex air- March 1981, many of the problems For the temporary technicians, flows that Ames could not analyze eas- seemed solved. However, few outside working on the Shuttle was an Òinter- ily and they were not amenable to the NASA shared this confidence and as esting and enjoyableÓ experience. pull-test technique. Thus, NASA had to Columbia prepared for its first flight in Although the hours were long, for go back to wind tunnel testing on the April 1981, the question of the tileÕs many it fulfilled their dreams of getting tiles. However, this was both expensive performance was still a matter of

Q U E S T 10:3 2003 51 doubt.79 alizes the dynamics of technological especially prevalent during technologi- ColumbiaÕs first flight eventually change; it veils any internal controver- cal testing.84 took place on April 12, 1981. NASA sies from public view and presents Testing performs a vital role in the had scheduled the first launch for April technology as an autonomous thing, development, fabrication and operation 10, but the back-up flight computer which is beyond politics and society.82 of technology. Yet, in comparison to its failed 20 minutes before lift-off, mov- Thus, commentators often articulate equivalent in the sciences, the experi- ing the launch to two days later.80 This technological failure in terms of the ment, the test has received little atten- time everything went according to plan dichotomy between technical and polit- tion from the social studies of technolo- and Columbia climbed into the sky on ical decisions, between ÔobjectivityÕ gy. In technically complex projects, like the Sunday morning with no problems. and interests, where political compro- the Shuttle, many different groups of However, once in orbit, a potentially mise diverts Ôvalue-freeÕ technological engineers are involved in the testing serious problem emerged. Television progress from its ÔtrueÕ and ÔnaturalÕ processes. All the components are, at monitor cameras, fitted to observe the course. first separated and tested in isolation, payload bay doors open, caught sight of Authors in the social construction before integrated into the system as a missing tiles on the orbital maneuver- of technology, however, have shown whole. As with other elements of the ing system pods. This in itself was that interests, dispute, controversy, program, therefore, testing was a alarming to NASA, but what concerned negotiation and compromise, i.e. poli- process of negotiation: between groups Mission Control most was if tiles on the tics, are a normal part of technology of engineers; between engineers and bottom of the orbiter were also missing. building: that social matters are never managers; and between the engineers NASA spent all of April 13 attempting absent from technological production, and the technology. The Shuttle engi- to find a solution, but as Hans Mark but intrinsic to it. Indeed, they have neers pushed for the maximum techni- recalled: shown that social interests operate as cal performance from the components contributory causes of action and form for which they were responsible. There was, of course, not part of the motives for technological Confidence that the Shuttle would work much that we could really do. If change. Technology is thus a negotiated was reached gradually, through a suc- there were indeed tiles missing space where actors play out their own cession of ÔsuccessfulÕ tests taken from the portion of Columbia that agendas. Technological artifacts and together. However, the knowledge would experience the highest systems cannot exist without the social accrued through testing was invariably heating rates, then we would only interactions within and among different open to dispute and the value of the find out by making the attempt to groups. They require assemblages of results, and the accuracy of the meas- bring her back to Earth. So we people and things to bring them into urements, were often open to question.85 made our best calculations and existence, to negotiate their meaning, Similarity relationships and simili- estimates, but, in the final analysis purpose and functioning.83 tude requirements lay at the heart of we had to...hope for the best.81 Macro politics, of course, played a testing. With the development of the central role in shaping NASAÕs Space thermal protection system, the opera- Columbia returned safely on that Shuttle. Budget restrictions, cost over- tional environment dictated that Ames occasion and went on to fly many more runs and inflation were all significant could only accomplish certain tests missions before showing us all the dan- shapers of both the technology and of using scale models in artificial condi- gers and risks involved in space flight. development practice. However, central tions created from theoretical assump- to the social constructivistsÕ approach is tions, empirical knowledge, engineer- AUTONOMOUS OR the idea that social processes influence ing judgment and a reliance on instru- INTERDEPENDENT what it means for a technology to be mentation. The systems, therefore, did deemed working. Important here is the not undergo the Ôactual testÕ until the As historian of technology Thomas concept of Òinterpretative flexibility.Ó Shuttle flew as a whole for the first Hughes once noted, patterns of techno- Interpretative flexibility changes a time. The arc tests on the thermal pro- logical change only appear inevitable seemingly unambiguous thing into sev- tection system, although an indicator of because large technological systems eral different things simultaneously, heat resistance, did not represent the have embedded within them the charac- dependant upon a multiplicity of human total operational environment through teristics of the past. Such massive sys- viewpoints. This fluidity of interpreta- which the system had to work. In addi- tems, he claimed, have inertia analo- tion is often most obvious during the tion to the arc tests, AmesÕs engineers gous to that of the physical world in design stage, where a myriad of choic- had to simulate the complex airflows of that their mass of technical and organi- es are open to the technology builders. re-entry: the most difficult of which zational components tends to maintain However, interpretative flexibility was boundary-layer transitions from their steady growth in a particular operates along the entire life of a tech- laminar to turbulent flows. Recreating direction. This momentum institution- nology and, as highlighted above, is turbulent flows in the laboratory was

Q U E S T 10:3 2003 52 not an easy task. Because of their chaot- REFERENCES: (Houston, Texas: NASA, JSC, Conference Publication ic nature, similitude requirements were 2342, 1985): 209-263; Frank Reagan, Re-Entry Vehicle 1 Nigel Henbest, Heather Couper, Space Shuttle: The Dynamics (New York: American Institute of Aeronautics difficult to meet and the ÔvalidityÕ of Human Time Bomb? 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Corliss, Wind restored.86 Social Construction of Technology: A Review, Robert Tunnels of NASA (Washington DC, NASA Scientific and Fox, ed. Technological Change: Methods and Themes in Technical Information Branch, 1981): 85; Hans Mark, Negotiation about the operational the History of Technology (London: Harwood Academic Arnold Levine, The Management of Research environment was, therefore, a pervasive Publishers, 1996): 17-35; Trevor Pinch and Weibe Institutions: A Look at Government Laboratories part of the testing process. Results Bijker, ÒThe Social Construction of Facts and Artefacts,Ó (Washington DC: NASA, Scientific and Technical Social Studies of Science 14, (1984): 399-441. Information Division, 1984): 81-81. accrued through one set of tests did not 13 always correspond with results from 3 Marcel LaFollette, Jeffrey Stine, Contemplating Arc-jet facilities preheat the test gas in the stilling chamber upstream of the nozzle by means of a continu- another set of tests. This was the case Choice: Historical Perspectives on Innovation and Application of Technology, Marcel LaFollette, Jeffrey ous electric arc. The heated gas is then injected under when budgetary and schedule pressures Stine, ed. Technology and Choice: Readings from pressure into the nozzle. Though the arc-jet is an drove the decision to move ahead with Technology and Culture (Chicago: The University of extremely valuable facility for testing spacecraft heat- Chicago Press, 1991): 1-17; William Normyle, ÒShuttle shield materials, the test stream is subject to contamina- the tile fabrication and installation pro- Poses Dominant Challenge,Ó Aviation Week and Space tion from the arc. Benjamin Elson, ÒNew Unit to Test gram before Ames had completed its Technology (June 22, 1970): 99. Shuttle Thermal Guard,Ó Aviation Week and Space aerodynamic and re-entry analysis. Technology March 31 (1975): 52. 4 Robert Freitag, interview with Brian Woods, Virginia, 14 Contention soon arose about the struc- June 5, 1995; Robert Dotts, Donald Curry, Donald Richard Hallion, The Path to the Space Shuttle: The tural integrity of the tiles and confi- Tillian, ÒOrbiter Thermal Protection System,Ó Norman Evolution of Lifting Re-entry Technology. (History Office, Air Force Flight Test Center, November 1983); dence in the tile systems plummeted Chaffee, ed. Space Shuttle Technical Conference (Houston, Texas, NASA, JSC, Conference Publication Baals and Corliss, 75; Walter Vincenti, workshop pres- after the final aerodynamic, and 2342, 1985): 1062; Mike Gray, Angle of Attack (New entation at the University of Edinburgh, May 20, 1998; aerothermodynamics data indicated York: W.W. Norton, 1992): 212-215; Hans Mark, inter- Elson, 52. Jerry Grey, Enterprise (New York: William Morrow, 1979): 103-105; David Halliday, Robert that the re-entry and ascent environ- view with Brian Woods, Texas, September 8, 1995; Letter from Hans Mark to Roy Jackson, February 15, Resnik, Physics: Parts 1 and 2 (New York: John Wiley ments were far more severe than first 1972, Archives at the NASA History Office, Washington & Sons, Third Edition, 1978): chapter 18. DC; NASA, Space Shuttle Program Requirements considered. The Ôpull-test,Õ initiated by 15 Document: Level 1. Archives at the NASA History Robert Thompson, interview with Brian Woods, Texas, Kennedy, was an attempt to restore this Office, Washington DC: 4; David Baker, ÒEvolution of September 9 1995; Christopher Kraft, interview with confidence, but the result was a the Space Shuttle,Ó Spaceflight (September 1976): 311; Brian Woods, Texas, September 1 1995; Raymond redesign of the tiles. Anon 1, ÒShuttle May Use Low-Cost Ablatives,Ó Dupree, interview with Brian Woods, Alabama, August Aviation Week and Space Technology (October 5, 1970): 21 1995. In essence then, what the above 56. paper has aimed to highlight is what 16 Walter Vincenti, What Engineers Know and How They 5 Know It: Analytical Studies from Aeronautical History many working under the rubric of sci- Dotts et al., Space Shuttle Technical Conference, Part 2, 1062-1081. (Baltimore: The John Hopkins University Press, 1993): ence and technology studies have especially chapter 1; Walter Vincenti, workshop presen- argued: that technology forms part of a 6 Dennis Jenkins, Space Shuttle (Wisconsin: tation at the University of Edinburgh, May 20, 1998; Motorbooks, 1993): 76, 79, 93; Baker, 264-265. Elson, 52. Jerry Grey, Enterprise, 103-105; Halliday, and Ôseamless webÕ of society, politics, ide- Resnik, Physics: Parts 1 and 2, chapter 18. ology and economics. The development 7 Normyle, 96-121; Dotts, et al., Space Shuttle Technical 17 Conference, Part 2, 1062-1081. Walter McDougall, The Heavens and the Earth: A of a technological artifact or system is Political History of the Space Age (New York: Basic not simply a technical activity but is 8 Anon 2, ÒNon-Metallics Studied for Shuttle,Ó Aviation Books, 1985): 164, 166, 190-91, 339-41; Baals and also intrinsically a social one. When Week and Space Technology January 18, (1971): 36-39; Corliss, 107-109; Roy F. Houchin, ÒThe Diplomatic technologies fail, therefore, we should Jenkins, 89; Samuel Beddingfield, interview with Brian Demise of Dyna-Soar,Õ Aerospace Historian, Winter Woods, Florida, July 31, 1995; Anon 2, 36-39; Dotts, et (1988): 274-280. not be surprised to find politics embed- al., Space Shuttle Technical Conference, Part 2, 1062- 18 ded in the systems we create. 1081; Jenkins, 119. Bastian Hello, interview with Brian Woods, Maryland, April 27 1995. 9 William Hieronymus, ÒTwo Reusable Materials Studied 19 for Orbiter Thermal Protection,Ó Aviation Week and Ibid. Space Technology (August 23, 1973): 16-18; Dotts, et Brian Woods is a 20 al., Space Shuttle Technical Conference, Part 2, 1062- Supporting Space Research and Technology Panel Research Fellow at the 1081. Aeronautics and Astronautics Coordinating Board, Science and Technology Studies Unit, Report to the Ad Hoc Committee on Reusable Launch Department of Sociology, 10 James Young, Jimmy Underwood, Ernest Hillje, Vehicle Technology, September 14, 1966; Memorandum Arthur Whitnah, Paul Romere, Joe Gamble, Barney from George Mueller, Associate Administrator Office of University of York, UK. Roberts, George Ware, William Scallion, Bernard Manned Space Flight to Acting Associate Administrator, Spencer, James Arrington, Deloy Olsen, ÒThe Office of Advanced Research and Technology, August Aerodynamic Challenges of the Design and 25, 1969; Minutes of Meeting: NASA Research and Development of the Space Shuttle,Ó Norman Chaffee, Technology Advisory Council, Committee on Space ed. Space Shuttle Technical Conference, Part 1 Vehicles, September 25-26, 1974, Archives at NASA

Q U E S T 10:3 2003 53 History Office, Washington DC. 38 Robert Thompson, interview with Brian Woods, Texas, (Washington DC: Brookings Institute, 1981): 227; Letter September 9 1995. from James Fletcher to Roy Ash, Director of OMB, July 21 Baals and Corliss, 81. 13, 1973, Archives at the NASA History Office, 39 Ibid; Young, et al., Space Shuttle Technical Washington DC; Letter from James Fletcher to Richard 22 Ibid., 81. Conference, Part 1, 209-263. Nixon, July 13, 1973, Archives at the NASA History Office, Washington DC; Gawdiak, Fedor, NASA 23 Ibid., 86, 117-121. 40 Robert Thompson, Von Karman Lecture: The Space Historical Data Book Volume IV, Table: 4-13, p 134. Shuttle - Some Key Program Decisions (Reno, Nevada: NASAÕs total appropriation for FY 1974 stood at 24 Ibid., 95-96. AIAA 22nd Aerospace Sciences Meeting, AIAA-84- $3,039,700,000. 0574 January 9-12, 1984): 3-4. 25 Stanley Berger, Laminar Wakes (New York: American 53 Letter from James Fletcher to Richard Nixon, July 13, Elsevier Publishing Co Inc, 1971): preface; Elson, 52. 41 Robert Thompson, interview with Brian Woods, Texas, 1973, Archives at the NASA History Office, Washington September 9 1995. DC. 26 Robert Ried, ÒÔOrbiter Entry Aerothermodynamics,Ó Norman Chaffee, ed., Space Shuttle Technical 42 James Odem, interview with Brian Woods, Huntsville, 54 Gawdiak, Fedor, NASA Historical Data Book Volume Conference: Part 2 (Houston, Texas: NASA, JSC, August 21, 1995. IV, Table: 4-14, p 135. NASAÕs total appropriation for Conference Publication 2342, 1985): 1055. FY 1975 stood at $3,231,093,000. 43 Ibid; R.H. Gray, memorandum for distribution, May 7, 27 Walter Vincenti, What Engineers Know and How They 1974, Archives at the Kennedy Space Centre, Florida; 55 Itoh Makoto, The World Crisis and Japanese Know It, 37-39. Letter from Robert Thompson to Shuttle Projects Office Capitalism (London: MacMillan Press, 1990): 32-34, Manager, Kennedy, November 4, 1974, Archives at the 50-57; Eric Hobsbawm, The Age of Extremes: The Short 28 An important similarity parameter for viscosity has Kennedy Space Centre, Florida; Frederick Bachtel, Twentieth Century 1914-91 (London: Michael Joseph long been the Reynolds number. Formulated by Osborne Jerold Vaniman, James Stucey, Carroll Cray, Bernard Ltd, 1994): chapter 9. Reynolds in the late 19th Century while studying the Widofsky, ÔThermal Design of the Space Shuttle flow of water in pipes and channels, the Reynolds num- External Tank,Õ Norman Chaffee, ed. Space Shuttle 56 K. Johnsen, ÒInflation Boosts Labor Demands,Ó ber is a dimensionless number that expresses the ratio of Technical Conference Part 2 (Houston, Texas, NASA, Aviation Week and Space Technology (July 23 1974): 12- inertial forces to viscous forces and is given by the equa- JSC, Conference Publication 2342, 1985): 1041-1050. 13; Craig Covault, ÒInflation Forcing Shuttle Changes,Ó tion Re = velocity x density x characteristic length/vis- Aviation Week and Space Technology September 23 cosity coefficient. The Reynolds number is significant 44 James Odem, interview with Brian Woods, Huntsville, (1974): 20-22; Barry Casebolt, ÒOverrun on Costs Of because it allows aerodynamic engineers and naval August 21, 1995. Shuttle Studied,Ó The Huntsville Times April 14, (1974): architects to translate results obtained from scale model 5-6. experiments to full-scale conditions. If the Reynolds 45 Ibid; Letter from Robert Thompson to Shuttle Projects number is the same (i.e. the model is operated in the Office Manager, Kennedy, November 4, 1974, Archives 57 Letter from James Fletcher to Roy Ash, Director OMB, same fluid as the prototype) then similarity is achieved. at the Kennedy Space Center, Florida; Space Shuttle: July 13, 1973, Archives at the NASA History Office, For example, if a model is 1/10 the size of a full-size air- 1975 Status Report for the Committee on Science and Washington DC. craft, then the air density (the number of atmospheres) Technology, US House of Representatives (Washington inside the tunnel must be increased by a factor of 10 to DC: US Government Printing Office, February 1975): 58 NASA position paper, 18 October 1974, Archives at get wind tunnel results that are valid in regular atmos- 94; Frederick Bachtel, et al. Space Shuttle Technical the NASA History Office, Washington DC: p 2. pheric conditions with a full-size aircraft. Conference Part 2, 1041-1050; NASA Position Paper, no date, Archives at the Kennedy Space Centre, Florida: 2. 59 GAO, Staff Study: Space Transportation System 29 Ried, pp 1051-1061; Berger, preface, 3-6; B. Kent (Washington DC: General Accounting Office Joosten, ÔDescent Guidance and Mission Planning for 46 The sintering process involves the heating metal or Distribution Center, 1975): 3, 21, 24. the Space Shuttle,Õ Norman Chaffee, ed., Space Shuttle ceramic powders, under high pressure and temperatures Technical Conference: Part 1 (Houston, Texas: NASA, so that the powder grains liquefy and bond to form 60 W.H. Morita, ed. Space Shuttle System Summary JSC, Conference Publication 2342, 1985): 113-124. strong shapes. Dotts, et al., Space Shuttle Technical (Rockwell International, SSV80-1, May 1980): 110; Conference, Part 2, 1062-1081. Lockheed Missiles and Space Co., Inc., Space Systems 30 Christopher Kraft, interview with Brian Woods, Texas, Division, 325-329; Dotts, et al., Space Shuttle Technical September 1 1995. 47 Ibid.; Lockheed Missiles and Space Co., Inc., Space Conference, Part 2, 1062-1081. Systems Division, ÒSummary of High Temperature 31 Young, et al., Space Shuttle Technical Conference, Part Reusable Surface Insulation Program,Ó Space Shuttle 61 Lockheed Missiles and Space Co., Inc., Space Systems 1, 209-263; Ried, 1051-1061. 1976 Status Report for the Committee on Science and Division, 325-329. Technology US House of Representatives (Washington 32 Ibid; Paul Ceruzzi, Beyond the Limits: Flight Enters DC: US Government Printing Office, October 1975): 62 Christopher Kraft, interview with Brian Woods, Texas, the Computer Age (Cambridge, Massachusetts: MIT 325-329. September 1, 1995. Press, 1989): chapter 7. 48 Ibid. 63 Dotts, et al., Space Shuttle Technical Conference Part 33 Dean Chapman, quoted in Muenger, p 173. 2, 1062-1081. 49 Memorandum from Willis Shapely to George Low, 34 Hans Mark, Arnold Levine, 81; Muenger, 173-176; July 26, 1972; Letter from James Fletcher to Roy Ash, 64 Anon 3, ÒThermal Tiles Applied to Orbiter 102,Ó Ceruzzi, chapter 7; Dean Chapman, Hans Mark, Melvin Director of the Office of Management and Budget, July Aviation Week and Space Technology (November 27, Pirtle, ÒComputers vs Wind Tunnels for Aerodynamic 13, 1973; Letter from James Fletcher to Richard Nixon, 1978): 64; Anon 4, ÒF-15 Used in Shuttle Tile Test,Ó Flow Simulations,Ó Astronautics and Aeronautics (April July 13, 1973, Archives at the NASA History Office, Aviation Week and Space Technology February 25, 1975): 22-35. Washington DC. (1980): 23; Gregg Easterbrook, ÒThe Spruce Goose of Outer Space,Ó The Washington Monthly 12 (1980): 32- 35 Memorandum from Charles Donlan to the Associate 50 Letter from James Fletcher to Richard Nixon, July 13, 48. Administrator for Space Flight, February 19, 1976; 1973, Archives at the NASA History Office, Washington Memorandum from Charles Donlan to the Associate DC. 65 Bruce Smith, ÒLoss of Tiles Delays Orbiter Ferry Administrator for Space Flight, March 25, 1976, Flight,Ó Aviation Week and Space Technology March 19, Archives at the NASA History Office, Washington DC. 51 Robert Thompson, interview with Brian Woods, Texas, (1979): 21-22; Transcript from NBC 6:30 pm News, September 7, 1995; NASAÕs total appropriation for FY NBC TV, December 21, 1979 (NASA History Office 36 Memorandum from Charles Donlan to the Associate 1973 was $3,407,636,000. Ihor Gawdiak, Helen Fedor, Archive, Washington DC). Administrator for Space Flight, March 25, 1976, NASA Historical Data Book Volume IV (Washington Archives at the NASA History Office, Washington DC. DC: NASA History Office, 1994): Table: 4-12, p 133. 66 Jimmy Carter, quoted in NASA Activities, May, 1979, Archives at the NASA History Office, Washington DC; 37 Ibid, my emphasis. 52 James Reichley, Conservatives in an Age of Change Herb Yarbrough, interview with Brian Woods, Texas,

Q U E S T 10:3 2003 54 September 5, 1995; Anon 5, ÒKSC Personnel Face Real Schneider, Miller, 403-413. Science Technology and Social Change (London: Unwin Challenge,Ó Spaceport News, 18 (1979): 3, 6; John Tribe, Hyman Ltd, 1988). interview, with Brian Woods, Florida, July 28, 1995. 73 John Tribe, interview, with Brian Woods, Florida, July 28, 1995; R. Jeffrey Smith, ÒÔShuttle Problems 83 Barry Barnes, Interests and the Growth of Knowledge 67 Samuel Beddingfield, interview with Brian Woods, Compromise Space Program,Ó Science 206, (1979): 910- (London: Routledge, 1977); Barry Barnes, David Bloor Florida, July 31, 1995. 914; Arlen Large, ÒAmericaÕs Space Shuttle Lemon,Ó and John Henry, Scientific Knowledge: A Sociological Wall Street Journal (January 31, 1980): p 14; Deborah Analysis (London: Athlone, 1996); Trevor Pinch, The 68 Robert Thompson, Von Karman Lecture, 11-12; Kyle, ÒThe Space Shuttle: Ahead of Its Time--Or Biding Social Construction of Technology: A Review, 17-35. Robert Thompson, interview with Brian Woods, Texas, It?Ó Armed Forces Journal International (July, 1980): September 9, 1995; Christopher Kraft, interview with 44, 56; S. Diamond, ÒNASA Wasted Billions, Federal 84 Trevor Pinch and Weibe Bijker, 399-441; John Law, Brian Woods, Texas, September 1, 1995; Robert Frosch, Audit Discloses,Ó New York Times (April 23, 1986). Michel Callon, ÔThe Life and Death of an Aircraft: A Press Briefing on Dr. FroschÕs Conversation with Network Analysis of Technical Change,Õ Wiede Bijker, President Carter Regarding the Space Shuttle, November 74 John Halsema, interview with Brian Woods, Florida, John Law, ed. Shaping Technology/Building Society: 14, 1979, Archives at NASA History Office, Washington July 26, 1995. Studies in Sociotechnical Change (Cambridge, DC; Anon 6 ÒNASA, Contractor Push New Tile Tests,Ó Massachusetts: MIT Press, 1992): 21-52; Ronald Kline, Aviation Week and Space Technology (October 15, 75 John Tribe, interview, with Brian Woods, Florida, July Trevor Pinch, ÒUsers as Agents of Technological 1979): 44; Craig Covault, ÒKennedy Center Starts 28, 1995 Change: The Social Construction of the Automobile in Shuttle Stacking,Ó Aviation Week and Space Technology the United States,Ó Technology and Culture 37 (1996): (November 5, 1979): 18-19; Craig Covault, ÒShuttle 76 John Halsema, interview with Brian Woods, Florida, 763-795. Project Faces New Problems,Ó Aviation Week and Space July 26, 1995; John Tribe, interview with Brian Woods, Technology (December 10, 1979): 20-21; Anon 7, Florida, July 28, 1995; Samuel Beddingfield, interview 85 Trevor Pinch, ÔTesting - One, two, Three ... Testing! ÒOrbiter Protective Tiles Assume Structural Role,Ó with Brian Woods, Florida, July 31, 1995. Towards a Sociology of Testing,Õ Science, Technology, Aviation Week and Space Technology (February 25, and Human Values 18 (1993): 25-41; Donald 1980): 22-24. 77 Anon 4, 23; Anon 8, ÒSpace Shuttle Tile Tests MacKenzie, ÒFrom Kwajalein to Armageddon? Testing Completed,Ó Aviation Week and Space Technology and the Social Construction of Missile Accuracy,Ó David 69 William Schneider, Glenn Miller, ÒThe Challenging (January 19, 1981): 30. Gooding, Trevor Pinch, Simon Schaffer, ed. The Use of ÔScales of the BirdÕ: Shuttle Tile Structural Integrity,Ó Experiment: Studies in the Natural Sciences Norman Chaffee, ed. Space Shuttle Technical 78 Schneider, Miller, 403-413. (Cambridge: Cambridge University Press, 1989). Conference, Part 1 (Houston, Texas: NASA, JSC, Conference Publication 2342, 1985): 403-413. 79 Christopher Kraft, interview with Brian Woods, Texas, 86 Ibid; Donald MacKenzie, ÒHow do we Know the September 1, 1995. Properties of Artifacts? Applying the Sociology of 70 Ibid; Craig Covault, ÒKennedy Center Starts Shuttle Knowledge to Technology,Ó Robert Fox, ed. Stacking,Ó 18-19. 80 John Garman, ÒÔThe ÒBugÓ Heard ÔRound the World,Ó Technological Change, 247-63; Pinch, Science, Software Engineering Notes (6 October 1981): 3-10. Technology, and Human Values 18, (1993): 25-41; 71 George Jeffs, quoted in Anon 7, 22. Vincenti, What Engineers Know and How They Know It, 81 Hans Mark, Space Station: A Personal Journey chapter 5. 72 Ibid; Craig Covault, ÒÔKennedy Center Starts Shuttle (Durham: Duke University Press, 1987): 124-125. Stacking,Ó 18-19; Craig Covault, ÒÔNASA Presses to Hold Shuttle Schedule,Ó Aviation Week and Space 82 Thomas Hughes, American Genesis: A Century of Technology (July 21, 1980): 16-17; Craig Covault, Invention and Technological Enthusiasm 1870-1970 ÒNASA Tightens Shuttle Schedule Again,Ó Aviation (New York: Viking, 1989): 459-461. See also Donald Week and Space Technology (August 11, 1980): 27-28; MacKenzie, Inventing Accuracy; Steven Yearley,

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