Despite the fact that it is one of the most celebrated experimental aircraft ever flown, most historical writings have always had a rather peculiar blind spot regarding the X-15 program.¹ The citation for the 1961 Collier Trophy, for example, noted that the vehicle had made "invaluable technological contributions to the advancement of flight." It also commends "the great skill and courage" of its test pilots.² In his letter nominating the program for the award earlier that same year, NASA Deputy Administrator Hugh L. Dryden struck the same general themes, albeit in greater detail:
 

To the X-15 Research Airplane Team, the scientists, engineers, technicians, and pilots of the National Aeronautics and Space Administration; the Department of Defense; and North American Aviation, Incorporated for the conception, design, development, construction, and flight operation of the X-15 research airplane, which contributed valuable research information in the supersonic and hypersonic speed regime up to the fringes of space, and who have thereby made an outstanding contribution to American leadership in aerospace science and technology and in the operation of manned space flight.³

These two features —an outstanding piece of machinery, flown by exceptionally brave and proficient pilots— still stand as the primary legacy of the X-15.

Certainly, all of this fame is well-deserved. Considering its technical achievements, as well as its contribution to knowledge about the upper atmosphere, hypersonics, high-altitude piloted flight, and so on, the X-15 clearly stands as one of the most successful research programs in the history of aviation. Similarly, the men who flew the craft into the fringes of space at six times the speed of sound proved themselves time and again to be extraordinary individuals. These elements of the program have been recognized repeatedly, with the X-15 and its members receiving sixteen awards in addition to the Collier Trophy.

In a White House ceremony, July 18, 1961, President John F. Kennedy presented the Collier Trophy to X-15 pilot Major Robert M. White (shown standing next to the Trophy). Also receiving the award were Commander Forrest S. Petersen, and Dr. Joseph A. Walker (not pictured). (NASA photo no. 62-X-15-19).

The problem with the prevailing view of the X-15 is not so much that it is wrong, but rather that it is incomplete. For more than three decades, the vehicle's technical design, its scientific accomplishments, contributions to aerospace engineering, its flight records, and even the personal stories of its pilots have been extolled repeatedly in books, articles, monographs, and lectures. ⁴ Very little, however, has been written about how the program was actually run, and virtually nothing has ever been recorded about its overall management.⁵ Most historical accounts begin with the National Advisory Committee for Aeronautics' (NACA) decision in the early 1950s to pursue development of a high-altitude research plane, describe the technical aspects behind the selection of the contractors, and then skip over to the October 1958 rollout of the first vehicle.⁶

Not only is this view largely incomplete, but it also tends to give the impression that the X-15 experience was completely smooth and trouble free. Even the program's most serious technical problems are seldom described in any detail, and some difficulties, such as the fact that the project ran significantly over its budget, have never really been discussed at all.⁷

To take one example, which will be explored further below, the development of the vehicle's main XLR-99 rocket engine fell considerably behind schedule, at one point posing a significant threat to the entire program. Ultimately, after much wrangling with the engine contractor, Air Force and NACA officials opted to conduct initial flight tests with two smaller XLR-11 engines. Most X-15 histories, however, dispose of this affair in a couple of sentences, almost suggesting that it was nothing more than a brief annoyance. Indeed, in remarks made at the Collier Trophy Award ceremony in July 1962, Robert C. Seamans, Jr., portrays it as a routine decision, virtually planned in advance, rather than forced by necessity: "In January, 1958, the project management decided to continue the development of the 57,000-pound thrust engine, but to use a small engine as the power plant for initial X-15 flights."⁸

This account of the X-15 is unfortunate for a number of reasons. To begin with, the historical literature —laudatory as it has been— actually understates the magnitude of the program's accomplishments. Technical malfunctions, delays, and cost overruns are a normal part of any "cutting edge" research and development (R&D) program, and those in charge of the vehicle's development and operation deserve even more credit than they have received for working around such difficulties. Their efforts are especially impressive in view of the fact that the X-15 represented the NACA's (and later NASA's) first efforts at managing a large-scale project.⁹

Secondly, because most discussions of the X-15 have been so idealized, current United States space policy, and particularly NASA itself, have sometimes suffered by comparison. For years, observers have contrasted the cost, reliability, and performance of the X-15 with the ongoing problems of the space shuttle fleet.¹⁰ Since the history of the shuttle's development has been explored rather thoroughly, the extent to which such comparisons are warranted can only be determined by examining the full history of the earlier program in greater detail.¹¹

Finally, a full understanding of the X-15's administrative and managerial history can provide some important insights into the problems of the present United States space program. Given that practically all that the vehicle is known for today is its superb design, it is hardly surprising that pilots and engineers who speak of the "lessons learned" from the X-15 experience confine themselves exclusively to technical questions.¹²

The X-15 rocket airplane, designed to fly at speeds near 4,000 miles per hour and to attitudes above 50 miles, shown in Rogers Dry Lake at the NASA Flight Research Center, Edwards, California, where the research vehicle, underwent an extensive flight test program. (NASA photo no. 60-X-31).

As this chapter will show, the program still has a great deal to teach about the administration, and especially the politics, of large-scale and complex R&D programs. After a brief overview of the facts about the X-15 that are already generally known, it will examine some of the less celebrated aspects of the project, and show what administrative and especially political factors played a role in its great success.

The original mission of the X-15 was to explore the phenomena associated with hypersonic flight. Three of the rocketplanes were built by the North American Aviation Corporation. Each was constructed out of a newly-developed nickel alloy known as Inconel X, and measured fifteen meters long, with a wingspan of nearly seven meters. Missions took place within the specially constructed High Test Range, an aerodynamic corridor that stretched 780 kilometers (by 80 kilometers) from Utah across the Nevada and California deserts to Edwards Air Force Base, complete with radar tracking stations and emergency landing sites. During a typical mission, the X-15 vehicle was carried to an altitude of 14 kilometers by a modified B-52 (of which two were built) and released. The single pilot would ignite the XLR-99 engine, which would burn for approximately ninety seconds, accelerating to an average speed of Mach 5. After flying a parabolic trajectory into the upper atmosphere, the pilot would bring the craft in for a glide landing on the Rogers dry lake bed at Edwards.

The X-15 rocket airplane, showing its major components. (NASA photo no. 62-X152-22).

Serious planning for the X-15 began in the early 1950s, when the NACA began to consider the problems that were likely to be encountered in piloted space flight.¹³ By early 1954, the agency had identified four technical areas of concern: the materials and structures needed to resist the high temperatures of reentry, a better understanding of the aerodynamics operating at hypersonic speeds, systems to maintain vehicle stability and control, and the ability of pilots to work effectively in the space environment.

The NACA's Langley Aeronautical Laboratory, Ames Aeronautical Laboratory, and the High-Speed Flight Station began studying the feasibility of developing a research airplane capable of exploring these critical issues. By the middle of the year, NACA engineers had settled upon the basic design configurations for a craft capable of speeds up to 6,600 feet per second (Mach 6) and an altitude in excess of 250,000 feet.

The agency quickly realized that developing such a plane would be too large and expensive an undertaking for the NACA alone. Accordingly, in July 1954 officials met with representatives of the Air Force and the Navy, both of which were considering developing similar vehicles and saw the NACA proposal as a reasonable compromise.

Thus, in December 1954, representatives from the NACA, the Air Force, and the Navy signed a Memorandum of Understanding (MOU) for the development and testing of a winged hypersonic vehicle. The MOU called for the NACA to have technical control over the project, and for the Air Force and Navy to fund the design and construction phases, under Air Force supervision. After contractor testing was completed, the vehicle would be turned over to the NACA, which would conduct the actual flight tests.¹⁴The Air Force

Air Launch of X 15 #1 from Boeing B-52 Stratofortress. (NASA photo).

would also oversee (and pay for) construction of the High Test Range. The Navy was in charge of the simulation and training portions of the program.¹⁵ An interagency body, the Research Airplane Committee (known by participants as the "X-15 Committee"), consisting of one representative from each of the sponsoring organizations, was formally in charge of supervising the project, although it appears to have played a largely symbolic role.¹⁶ On January 17, 1955, the plane was officially designated the X-15.

The Air Force sent out invitation-to-bid letters to twelve prospective contractors on December 30, 1954, and a bidder's conference was held at Wright-Patterson Air Force Base on January 18, 1955. Proposals were received from four companies on May 9. By August, the Air Force's Wright Air Development Center and the NACA had concluded that North American Aviation's proposal had the greatest merit. Negotiations with North American were stalled, however, by the company's concern over the proposed timeframe (it was at that time also building the F-107A and F-108 aircraft). Project managers agreed to extend the program from thirty to thirty-eight months, and in November (following price negotiations), the Air Materiel Command Director of Procurement and Production issued the formal contract letter to North American for the development and construction of three X-15 aircraft. ¹⁷

Separate invitations-to-bid were issued to four potential engine contractors on February 4, 1955, and the final contract for the X-15 engine, the XLR-99, was issued to Reaction Motors on September 7, 1956. By mid-1958, when it became clear that the XLR-99 would not be ready in time for the first round of test flights, Air Force project managers directed that two smaller XLR-11 engines (also built by Reaction Motors) be used for the initial tests.

Construction on the first X-15 began in September 1957. It was delivered (without the XLR-99 engine) to the Flight Test Center at Edwards on October 17, 1958.¹⁸ Scott Crossfield, an engineering test pilot for North American (who had earlier been a Navy pilot and NACA research engineer) flew the contractor demonstration flights, including the first captive flight on March 10, 1959, the first glide flight on June 8, and the first powered flight (with the XLR-11 engines) on September 17. The first government mission, with NASA pilot Joseph A. Walker, took place on March 25, 1960. Crossfield made the first flight with the XLR-99 engine on November 15, 1960.

By the end of 1961, the X-15 had achieved its design goal of Mach 6 and had achieved altitudes in excess of 200,000 feet. On August 22, 1963, Walker achieved an altitude record for piloted aircraft, taking the X-15 to 354,000 feet (more than 67 miles). On October 3, 1967, Captain William J. "Pete" Knight set a world speed record of 4,520 miles per hour (Mach 6.7), which would stand until the first mission of the space shuttle Columbia in 1981.¹⁹

In March 1962, the X-15 Committee approved an "X-15 Follow-on Program," a series of flights in which the vehicle was converted into a testbed for use in a variety of scientific observations and technological development projects. These flights produced a wealth of scientific information in such areas as space science, solar spectrum measurements, micrometeorite research, ultraviolet stellar photography, atmospheric density measurements, high-altitude mapping. The final flight of the X-15 program, the 199th, took place on October 24, 1968.²⁰

Most of those involved with the project had expected that work with the X-15 would lead directly to an even more ambitious craft, the X-20, or Dyna-Soar (short for "Dynamic Soaring" vehicle), which would actually fly to and from Earth orbit. That project, however, was canceled in the 1960s.²¹ It would not be until the Space Shuttle program that NASA would turn to the use of winged vehicles for piloted space flight.

Even an abbreviated listing of the X-15's accomplishments is truly impressive.²² As noted above, the program achieved, and in some cases surpassed, all of its initial objectives. Its top speed of Mach 6.7 exceeded the original goal of Mach 6.0. Similarly, its record altitude flight was far above the intended 250,000 feet.

In the area of technology development, the X-1 5 saw the first use of a "man-rated," "throttleable" rocket engine, the XLR-99 (once again, the performance of this engine would only be surpassed by those of the shuttle). It was the first vehicle to employ a reaction control system

for attitude control in space, a device that would be used by all the spacecraft that followed. The program saw the development of advanced bioastronautics instrumentation (including, for the first time, the ability to gather "real time" biomedical data) and all improved full-pressure suit. Finally, the X-15 provided an essential testing ground for advances in areas such as thermal protection, guidance, and navigation. All of these new technologies were to be used later in development of the Gemini, Apollo, and shuttle programs.²³

With regard to human factors, the project demonstrated that a pilot could function at hypersonic velocities, high altitudes, and during periods of weightlessness. In particular, it showed that it was possible for a pilot to fly a reentry path, that is, to cross the region between relatively airless space and the thicker lower atmosphere. The Navy's portion of the program —pilot training— marked the first extensive use of motion simulators, such as its human centrifuge at the Naval Air Development Center in Johnsville, Pennsylvania.

Given the magnitude of its objectives, as well as the vehicle's sheer complexity, the total development time of five years from project approval to first powered flight (and two years from construction start) is quite impressive. The estimated costs of the program appear similarly modest, particularly when compared to the space-related projects that followed. The program's total cost, including development and eight years of operations are usually estimated at $300 million in 1969 dollars. Each flight is estimated to have cost $600,000. ²⁴

By the time it became fully operational, the X-15 could be turned around in less than thirty days. Using all three craft, NASA was able to fly an average of four missions per month. More important, the program had an exceptionally low casualty rate. In November 1962, the landing gear on craft number two collapsed, flipping the vehicle over on its back and injuring pilot Jack McKay (who recovered and was to fly the X-15 again). On November 15, 1967, pilot Mike Adams was killed in a crash that destroyed craft number 3. These tragedies notwithstanding, for nearly 200 missions in a high-performance aircraft operating at the fastest speeds ever attained in a region of the upper atmosphere about which little was known, the X-15's record for safety and reliability was really quite extraordinary. Indeed, the most common reason for mission delays and aborts was weather (which had to be clear along the entire High Test corridor).²⁵

Finally, the program captured the popular imagination at a time when many Americans, and much of the world, believed that the United States had fallen behind in the space race with the Soviet Union. Public interest (and media coverage) of the initial flights was quite high, although it dissipated quickly after the beginning of Project Mercury. Nevertheless, the success of the X-15 provided the first tangible evidence to the country after Sputnik and Vanguard that American science and technology were on a par with that of the Soviet Union.

Even tinder ideal conditions, a successful R&D program of the scope of the X-15 represents an extraordinary managerial challenge. In addition to the sheer complexity of the technology, project officials had to overcome a number of unique administrative difficulties:

As already noted, this was NASA's first foray into full-scale project management. As a program, the X-15 involved far more than the development and flying of the aircraft itself.

Managers also oversaw the preparation of the two B-52 bombers, the construction of an 800 kilometer-long test range, and the design of the advanced full-pressure suit and the other new biomedical equipment. A completely new pilot training regime was developed and implemented. Indeed, in many respects the range of activities associated with the prograin (including dealing with intense media coverage) seem to foreshadow the practices and procedures the agency (as NASA) would employ in the Mercury, Gemini, Apollo, and shuttle, programs.

The X-15 is also notable for being a successful joint program, bringing together the efforts of the NACA, NASA, the Air Force, and the Navy. The fact that this collaboration worked as well as it did is remarkable for a number of reasons. To begin with, the later half of the 1950s generally was characterized by a high degree of interservice and interagency rivalry, particularly on matters related to space flight.²⁶ Indeed, it is difficult to reconcile the military's solicitousness in building and testing a multimillion dollar experimental aircraft (and a test range on which to fly it) only to hand it over to (what by then had become) NASA, while it was at the same time fighting with President Eisenhower over the transfer of most of its space facilities to the same agency.²⁷ Certainly, the whole arrangement seems unimaginable today.

Joint program experiences of NASA and the Department of Defense (DOD) generally have proved disappointing. In fact, the project to which the X-15 is most often compared —the Space Shuttle— is one of the more recent cases where NASA and DOD collaboration was less than successful. Critics of the program have charged that modifying the shuttle orbiter to carry out military missions was one factor in that craft's largely unsatisfactory performance .²⁸

Conventional wisdom holds that a joint project ought to have each participant's roles clearly articulated. One of the more striking features of the X-15 MOU, however, is that the division of responsibility for the craft's design —e.g., that the NACA had "technical control" under the Air Force's "supervision"— does not seem to be all that well spelled out. Such ambiguity is almost always a potential source of trouble for any joint project, particularly in view of the fact that the Air Force was providing the bulk of the program's funding.

As was noted earlier, the interagency X-15 committee was formally in charge of the project, but it does not appear that this body had much involvement in day-to-day decision-making, or in settling disputes among the participants. One observer has described its role as that of offering high-level sanction to lower-level decisions.²⁹ There were exceptions: on one occasion, when the Air Force had started to protest over building the High Test Range only to hand it over to the NACA (like the X-15 craft itself), the committee's endorsement of the original agreement served to end the dispute. ³⁰ For most other areas of potential conflict, however, there is no evidence that the X-15 committee ever played any substantive role.

Dr Joseph A. Walker stands beside the 1961 Collier Trophy, awarded to him and the other X-15 Pilots by President John F. Kennedy. (NASA photo no. 620X-20).

Commander Forrest S. Petersen, USN, standing beside the 1961 Collier Trophy presented by President John F. Kennedy. (NASA photo no. 620X-21).

The situation was further complicated by the fact that responsibility for the development and manufacture of the X-15's systems was spread across an exceedingly large number of contractors and sub-contractors. These included not only North American Aviation and Reaction Motors, but also General Electric (which was responsible for the Auxiliary Power Units), David Clark Co. (developer of the pressurization suit), the International Nickel Company (creator of the Inconel X nickel alloy for the fuselage), Bell Aircraft (supplier of the ballistic control rockets), Sperry Gyroscope (developer of the in-flight electronic indicator systems), and many, many others. In all, more than 300 private firms participated in the project.³¹

Fortunately —and surprisingly— the internal conflicts that did occur were minor, and appear to have had no impact on the program overall. Early in the design process, for example, the NACA's request for a modification to allow for testing different types of "leading edges" was rejected by the Air Force .³² In late 1955, during the negotiations with Reaction Motors, the Navy's Bureau of Aeronautics made a bid to take over responsibility for the development of the XLR-99. The Navy based this claim on the fact that it had been working with Reaction Motors for the past three years developing the XLR-30 rocket engine, the design of which was to serve as the basis of the X-15 power plant. The Air Force rejected this argument, citing (somewhat ironically) the need to keep management responsibility within a single agency.³³ Finally, as already noted, in 1955 the Air Force sought to retain control over the High Test Range.

One area of conflict, once again between the Air Force and the NACA, did prove to be rather serious, but in some respects may actually have been somewhat beneficial. The problem involved the development of the XLR-99, which proved be the most serious technical (and administrative) obstacle in the entire program.³⁴ The NACA had already complained to the Air Force in late 1955 that the procurement process for the engine was taking too long, prompting the latter to write a letter of reassurance. Then, in April 1956, a representative of the Lewis Laboratory who had visited the Reaction Motors facility reported the company's efforts on the engine to be "inadequate" on several fronts. He felt that the development program was already behind schedule and that some of its time estimates were too optimistic by as much as a year.

Although it is not clear what immediate impact this report had on the Air Force project managers, subsequent events were to bear out the NACA's concerns. In August 1956, an Air Force representative noted in a letter to Reaction Motors that a test of the engine's thrust chamber, which had been scheduled for April, had not yet taken place. By early 1957, North American had begun to complain about the pace of the engine development. The prime contractor found that not only was the program four months behind schedule, but that the weight of the engine was increasing while its projected performance appeared to be declining.

The difficulties arising from divided authority can be illustrated by the responses to North American's criticisms. In February 1957, two sets of meetings were held between Reaction Motors personnel and representatives of the Air Force (February 12 and 18) and the NACA and North American (February 19). For its part, the Air Force appeared to come out its meetings assured that "every effort [would be] expended to prevent further engine schedule slippages."

As was the case the previous April, however, the NACA was far more pessimistic. Its report of the February 19 meeting expressed doubt that the new schedule could be met (although the agency agreed to accept a delay of four months in delivery and a weight increase from 588 to 618 pounds). More significantly, this report for the first time mentioned the possibility of using an interim engine in order to maintain the X-15's flight test schedule.

Once again, the NACA's gloomy assessment proved to be correct. In July 1957, Reaction Motors advised the Air Force that it would need a nine-month extension (it also reported another weight gain, from 618 to 836 pounds). The following December, it reported another six-month slippage. Needless to say, there were substantial cost increases as well: by January 1958, costs for the engine's development were almost double the amount estimated just six months earlier. At this point, Air Force project managers seriously considered canceling the Reaction Motors contract and bringing in a new firm, which would have delayed full-power flights until at least 1961 (and might even have resulted in the outright cancellation of the program). By February 1958, however, the decision was made to continue with the current contractor, but to procure two smaller XLR-11 engines for the initial test flights.

The timetable of the main engine development seems to have been the only area of disagreement among the project's participants involving a major subsystem on the X-15, and even this was only a matter of timing, since all parties ultimately reached the same conclusion. ³⁵ It is also worth noting here that the NACA's and the Air Force's primary concerns were with the engine's performance and completion date. Staying within the original budget does not appear to have been a major consideration in the government's dealings with Reaction Motors, even though this phase of the program already was incurring massive cost overruns.

All in all, each of the principal organizations worked very well together. Rather than fall into competitive wrangling (a common danger of joint programs, particularly when problems arise), each of the partners provided a measure of much-needed redundancy and in-depth checking.

In considering difficulties like those surrounding the XLR-99, it is important to remember that it was the most sophisticated rocket engine built up to that time, in some respects even more complex than the Saturn V.³⁶ For there to be significant delays and technical problems with such a system is only to be expected. In fact, the project team's eventual response to the XLR-99 issue demonstrates yet another of its impressive management features, namely that it was able to absorb a number of delays and still maintain something approaching an orderly test schedule.

As it turned out, the main engine was not ready for flight until November 1960, more than two years after delivery of the first vehicle. The decision to substitute the two smaller engines, rather than wait on the XLR-99, allowed at least part of the initial flight tests to go forward; other aircraft systems could be checked out and the pilots could gain some familiarity with the vehicle.

This robustness, the ability of the program to adapt to inevitable technical failures, was seen time and again throughout the life of the X-15. No doubt much of this was due to the exceptional technical skills of North American and NASA engineers. During the first glide flight of craft number one on June 8, 1959, pilot Scott Crossfield experienced wild pitching motions just prior to landing; the ground team quickly (and successfully; it never occurred again) corrected the problem, and Crossfield was able to make the first

powered flight (in craft number two) less than three months later. On November 5, an engine fire broke out on X-15 craft number two, forcing Crossfield to make an emergency landing, which, in turn, literally broke the craft's back; that particular vehicle was grounded for only 98 days.

One of the more serious incidents of the demonstration phase occurred during the first ground tests of the XLR-99 engine in June 1960. A stuck pressure regulator caused X-15 craft number three to explode. The airplane essentially disintegrated aft of its wing. Despite the fact that it needed to be rebuilt completely, craft number three was returned to NASA and made its first successful flight eighteen months later. The first use of the XLR-99 in flight occurred on November 15, 1960.

The X-15 experienced technical difficulties and malfunctions of varying degrees of severity for much of the remainder of the program, but these seldom affected its overall flight schedule. Problems with different components and subsystems were repaired or even completely replaced whenever necessary, and the vehicle returned to duty relatively quickly. As noted earlier, the engineering prowess of the flight team deserves a great deal of credit, but it would also appear that the X-15 operations crew benefitted from the same lack of economic constraints enjoyed by Reaction Motors during the development of the main engine. NASA engineers at the Flight Research Center were routinely rejecting twenty-four to thirty percent of manufactured space parts as unusable.³⁷ As was the case with the XLR-99, the primary emphasis was on reliability and performance, rather than staying within a budget.

This last point suggests that, the extraordinary performance of the X-15 project team (managers as well as engineers) notwithstanding, the program benefitted from a number of external factors that were not necessarily under any of the participants' direct control.

To begin with, it appears that the X-15 succeeded as a joint undertaking primarily because of the consensus on its specific objectives among all of the parties involved, a fortunate circumstance that clearly could not have been dictated by any one member. Whenever an interagency project fails to meet its intended goals, it is usually because each organization has brought to it a different (and sometimes even contradictory) set of priorities.

This is essentially what occurred in the Space Shuttle program. In attempting to design the shuttle in a way that satisfied both its own objectives and those of the Department of Defense (as well as meeting the cost requirements imposed by the Office of Management and Budget and the Congress), NASA engineers were forced to make too many compromises in the spacecraft's design, with severe consequences for the longrun success of the program. Similar sorts of problems have plagued the space station as well.³⁸

The reference to OMB and Congress suggests another important difference between the X-15 and the shuttle (or, for that matter, the space station). The history of the earlier program shows virtually no involvement in the project (especially its design) on the part of outside political or budgetary agencies. Indeed, one major advantage that the X-15 program had over many later U.S. space projects (and one which is seldom mentioned in any X-15 histories) was the highly favorable political, economic, and social environment that surrounded most of the period of its development and the early phases of its flight operation.

The X-15 was never forced through in-depth hearings before congressional committees or protracted negotiations with the Bureau of the Budget (as it was then known), let alone subjected to outside scrutiny each year of its existence. Although responsibility for the project was spread across a number of government agencies and private firms, these actors —the military, the NACA, the NASA, and the aerospace contractors— represented a fairly uniform set of concerns: all wished to build a high-altitude, hypersonic experimental aircraft, and there was substantial agreement on what specific design and performance criteria the vehicle was to meet. This ensured that the major design decisions on the project would be made primarily according to technical, rather than political or economic considerations.

This is most clearly evident with regard to the question of the program's original cost estimates and time frame. It is seldom acknowledged in the historical literature, but the X-15 program was a victim of what has become a fairly common occurrence in the U.S. space program, namely substantial delays and overruns. Three hundred million dollars does seem small in comparison to the cost of, say, Apollo or the shuttle, but it is still more than seven times the original estimate of $42 million.³⁹ The final development costs of the engine alone were more than $68 million (plus a $6 million fee to Reaction Motors), a tenfold increase over what was expected when the project began.⁴⁰ In addition, the complete vehicle, including the large engine, was ready for flight more than two years behind schedule. Despite all of this, development during the 1955-1957 period was never held up by a lack of funds, although in some years needed funding did not come through until the last minute.

After the launch of Sputnik I in 1957, interest in the project on the part of the military, political leaders, and the public at large grew rapidly. As already noted, media coverage of the first flights was the most intense ever seen at Edwards, and even led to some public relations mix-ups between NASA and the Air Force.⁴¹

Once the first Mercury flights got underway, public attention shifted to the events at Cape Canaveral. This might, however, have ultimately worked to the program's benefit. A major contributor to the X-15's success over the long run was its emphasis on incremental development and its use in highly specialized scientific and technical research.⁴² As experience with many later space projects (including Apollo after Apollo 11, the shuttle, etc.) has shown, the general public tends to lose interest in such "routine" undertakings rather quickly. In short, it appears as though the X-15 got a needed boost of public fanfare at precisely the right point in its history —the later development and early flight test stage— and then became regarded as a low-key effort worthy of only occasional interest just as it was entering its less "flashy" research phase. These shifts in external perception probably could not have been planned any better.

The lack of external (i.e., outside the aerospace community) scrutiny very likely contributed to one more important effect. As seen repeatedly in the case of the XLR-99, as well as in actual flight operations, project officials from both the Air Force and NASA were never hesitant to point out —and more important, work to correct— potential (or actual) technical flaws, even when this resulted in increased costs. Recently, critics of the shuttle program have accused NASA of ignoring —or even covering up— such problems for fear of the political ramifications.⁴³

To the extent that this claim has any validity, the larger question it raises is whether NASA officials are simply more timid now than they were forty years ago, or whether the prevailing political and economic climate creates conditions more conducive to error detection and recovery. This is a particularly important point since, the claims of some critics of current U.S. space policy notwithstanding, one of the most interesting aspects of the X-15 program is that, far from being substantially different from later NASA enterprises, it is in many respects a familiar story: rampant cost increases, serious delays, technical failures, and even loss of life.

To be sure, the management of the X-15 was Superb, particularly given the difficulty of its mission. There was some degree of infighting, which usually was settled quickly. As expected on a project of this nature, technical difficulties arose, necessitating design compromises, additional costs, and schedule slippages. Because the program was surrounded by a supportive political and economic environment, however, NASA officials and their counterparts in the Air Force were able to face these problems squarely, and develop solutions, some of them quite innovative.

Nevertheless, given all of the controversy besetting the present U.S. space program, it is today a cause for wonder that an undertaking that had as many serious problems as the X-15 was not only tolerated at the time, but is now touted as one of the great aerospace success stories. In this context, perhaps even more now than then, the X-15 deserved the Collier Trophy as the program for the most outstanding aerospace achievement of its time.