Transiting from Air to Space
The North American X-15
SECTION I
GENESIS OF A RESEARCH AIRPLANE
During the spring of 1952, the Committee on Aerodynamics of the National Advisory
Committee for Aeronautics (NACA) recommended that several NACA laboratories begin
studies of problems likely to be encountered in spaceflight and examine methods of
exploring such problems. The NACA Executive Committee, which endorsed the
recommendation, directed consideration of laboratory techniques, missiles,
and manned aircraft.
Work along these lines progressed quietly for the next two years. Then, in February
1954, the NACA stepped up the pace, undertaking a more specific study to determine
the extent to which an advanced research aircraft could contribute to the solution
of problems earlier identified. Technical areas of concern at that time included
high temperature structures, hypersonic aerodynamics, stability and control, and
pilotage. An important requirement, specified at the outset of the work, was that
"a period of only about three years be allowed for design and construction in
order to provide the maximum possible lead time for application of the research
results." Such a requirement precluded the development of new materials, new
construction techniques, or improved launching practices. As one official
subsequently observed, "it was obviously impossible that the proposed aircraft
be in any sense an optimum hypersonic configuration."
NACA design engineers decided early that a relatively conventional airframe
was essential to the resolution of low speed launch and landing difficulties.
High speed requirements prompted the choice of a thick wedge tail to provide
directional stability and a ventral tail to improve control at high angles of
attack (where the upper vertical tail surface was immersed in low pressure
flow fields generated by the wing and fuselage). Artificial damping seemed
essential because of persistent uncertainties about the aerodynamic environment
at extreme speeds and altitudes. Static stability for all flight conditions and
the employment of hydrogen peroxide rockets for high altitude attitude control
also became objectives of the tentative design. NACA materials experts decided
that Inconel X offered the best heat sink structure and that heating problems
in general would impose the use of a blunt wing leading edge. Assuming that
air launch in the fashion of the X-1 and X-2 aircraft would be necessary,
NACA established aircraft size as the largest that could conveniently be
handled by B-36 or B-50 carriers. A maximum velocity of 6,800 feet per
second, an altitude potential of 400,000 feet, and a gross weight of 30,000
pounds (18,000 pounds of fuel) completed the general
proposal 1.
The studies that had prompted these recommendations of early 1954 were
independently produced by the three NACA laboratory stations (Langley,
Ames, and High Speed Flight Station). They induced NACA to adopt the
official policy that a manned research airplane was essential for study
of the problems earlier defined, that the construction of such an aircraft
was wholly feasible, and that quick action should be taken to pursue the
general objective. In June of 1954, therefore, the NACA contacted the Air
Force and the Navy, asking that a special joint meeting be held to consider
the need for a new research aircraft.
Wright Air Development Center (WADC), then having cognizance over system
development, provided technical representation for the Air Force at the
meeting - held in Washington on 9 July. Headquarters of the Air Research
and Development Command (ARDC) and Headquarters, United States Air Force
(USAF), sent policy representatives. In the course of the meeting it became
apparent that neither the Air Force nor the Navy had been indifferent to
the problems which had prompted NACA interest. The Air Force's Scientific
Advisory Board had been urging the construction of a "super X-2" while the
Navy's Bureau of Aeronautics had contracted for a feasibility study of a
manned aircraft capable of reaching an altitude of 1,000,000 feet. The
NACA proposal fell roughly between these extremes, being considerably
less ambitious than the Navy program and substantially more advanced
than the Air Force objective of the moment 2.
Both Navy and Air Force representatives viewed the NACA proposal with favor,
though each had some reservations. At the close of the meeting, however,
there was agreement that both services would study further the justification
and objectives of the NACA program, and that NACA would take the initiative
in securing project approval from the Department of
Defense 3.
Three weeks later, on 29 July, Headquarters ARDC instructed WADC to submit
technical comments on the proposal and to make time and cost
estimates 4.
Almost immediately, the WADC Power Plant Laboratory identified the principal
shortcoming of the original "study" - the apparent lack of a suitable rocket
engine. Initially and tentatively, NACA had suggested employing a modified
Hermes A-1 power plant; the Power Plant Laboratory early in August pointed
out that "no current rocket engines" entirely satisfied the NACA requirements,
and urgently emphasized that the Hermes engine was not designed to be operated
in close proximity to humans - that it usually was fired only when shielded
by concrete walls. Other major objections to the Hermes engine lay in its
relatively low level of development, in its limited design life (intended
for missile use, it was not required to operate successfully more than once),
and in the apparent difficulty of incorporating thrust variation provisions.
In the stead of the Hermes power plant, the laboratory suggested consideration
of several engines originally designed for use in manned aircraft. Hesitating
to make any positive recommendations in the absence of more specific data on
the aircraft, however, WADC recommended only that the selection of an engine
be postponed until propulsion requirements could be more adequately
defined 5.
WADC technical personnel who visited Langley on 9 August drew a firm distinction
between engines intended for piloted aircraft and those designed for missiles;
NACA immediately recognized the problem, but concluded that although program
costs would go up, feasibility estimates would not be
affected 6.
WADC's official reaction to the NACA proposal went to headquarters ARDC on
August 13 a. The director of laboratories (Colonel V. R. Haugen) reported
"unanimous" agreement among WADC participants that the proposal was technically
feasible; excepting the engine situation, there was no occasion for adverse
comment from WADC technical sources on the NACA-proposed solutions to major
problems.
In one respect, however, the official letter from WADC to ARDC did
not reflect unanimity of opinion. The comment forwarded by Colonel Haugen
contained a cost estimate of $12,000,000 "distributed over three to four
fiscal years" for two research aircraft, modification of a suitable carrier,
and necessary government-furnished equipment 7.
Mr. R. L. Schulz, technical
director for aircraft in the WADC Directorate of Weapon Systems Operations,
commented informally that although his directorate had concurred in the
letter, the concurrence included a reservation about the estimated cost which
the Fighter Aircraft Division reportedly furnished. Said Mr. Schulz,
prophetically: "Remember the X-3, the X-5, [and] the X-2 overran 200%. This
project won't get started for $12,000,000. 8"
On 13 September, Major General F. B. Wood, ARDC's Deputy Commander for Technical
Operations, forwarded to Air Force headquarters an endorsement of the NACA position
and its WADC support. Specifically, General Wood recommended that the Air Force
"initiate a project to design, construct, and operate a new research aircraft
similar to that suggested by NACA without delay." The aircraft, emphasized ARDC,
should be considered a pure research vehicle and should not be programmed as a
weapon system prototype. The research command estimated that about three and
one-half years would be consumed in the design and fabrication process and
forwarded WADC's cost estimate, broken down into specifics, without change.
(Estimated costs included: $1,500,000 for design work; $9,500,000 for
construction and development, including flight test demonstration; $650,000
for government furnished equipment, including engines, $300,000 for design
studies and specifications; and $250,000 for modification of a carrier
aircraft.) ARDC further suggested a preliminary design competition, assignment
of "sole executive responsibility" to the Air Force, and eventual transfer of
the resulting aircraft to NACA following a limited Air Force flight
demonstration program 9.
Brigadier General B. S. Kelsey, Deputy Director of Research and Development
in the office of the USAF Deputy Chief of Staff, Development, on 4 October 1954
expressed general agreement with the ARDC position, noting however that the
Department of Defense had decided that the project would be a joint Navy-NACA-USAF
effort managed by the Air Force and guided by a joint steering committee.
A 1-B priority, $300,000 in FY55 funds, and directions to support the
undertaking accompanied this explanation. Air Force headquarters further
pointed out the necessity for funding a special flight test range as part
of the project 10.
Formalization of the arrangements thus proposed required nearly eight weeks.
On 5 October, the NACA Committee on Aerodynamics formally endorsed the proposal
to build a Mach 7 research airplane to explore the fringes of
space. 11 On 22
October a meeting of Navy, NACA, and Air Force representatives at Wright Field
agreed on methods of originating and coordinating design requirements for an
eventual competition. Additionally, the conferees settled on four development
engines from which a power plant could be chosen by any interested airframe
contractor. 12
Early in November the two services and NACA reached a general
agreement on future operating procedures; a formal memorandum of understanding
emerged from the office of Mr. Trevor Gardner (Special Assistant for Research
and Development to the Secretary of the Air Force), and was forwarded for the
signatures of the Assistant Secretary of the Navy for Air (Mr. J. H. Smith Jr.)
and the Director of the NACA (Dr. H. L. Dryden). The process was effectively
complete by 23 December. 13
The memorandum of understanding, which set a general pattern for the future
management of the project, assigned technical direction of the program to the
director, NACA, "with the advice and assistance of a Research Airplane
Committee" .that included Navy and Air Force representatives. (General Kelsey
became the Air Force member and Rear Admiral R. S. Hatcher the Navy member.)
The Navy and the Air Force were to finance the undertaking and the Air Force
was to administer its design and construction phases. The preliminary NACA design
was to be the basis for solicited proposals for a design and construction contract.
Upon acceptance of the airplane from the contractor, it was to become NACA property.
The memorandum concluded with the statement: "Accomplishment of this project is a
matter of national urgency." 14
Accompanying the memorandum, as a matter of course,
was a secretarial-level Air Force concurrence in the establishment of a joint
project to build the proposed research airplane. 15
In the meantime, notwithstanding the absence of formal agreements or procedure,
Wright Field had been making arrangements for a design competition. By 15 November,
individual laboratories had compiled specification data for inclusion in a letter
of invitation to prospective contractors. Coordination with NACA and Navy
organizations presented no great difficulty; by 30 November headquarters ARDC
had approved plans to prepare official copies of competition data and had advised
Wright Field that in about two weeks the Office of the Secretary of Defense
probably would authorize distribution of the material. 16
Air Force headquarters
scheduled a 13 December briefing for the Secretary of Defense and approved
certain changes in the draft requirements. (USAF specified that air-launch was
required, that a prone-pilot provision would not be acceptable, that unconventional
design approaches would be sought, that instrumentation space was to be increased,
that non-NACA facilities would be used for flight tests, and that references to
costs in excess of $5,000,000 and to 1956 engine availability were to be eliminated
from the invitation to bid.) 17
Advance notice of the forthcoming competition was informally given to prospective
contractors early in December. In the last week of December, headquarters ARDC
directed that the letter of invitation be dispatched as soon as the center
received an official teletype authorizing such action. As prescribed by existing
regulations, the letter was to be circulated by the Air Materiel Command (AMC),
although that organization declined responsibility for selecting the recipients
and held to the policy that the competition was exclusively an ARDC
affair. 18
On 29 December the action teletype from Air Force
headquarters arrived. 19 Rubber
stamp dates completed the preparation process, and on 30 December AMC, over the
signature of Colonel C. F. Damberg, Chief, Aircraft Division, sent invitation-to-bid
letters to 12 prospective contractors (Bell, Boeing, Chance-Vought, Convair,
Douglas, Grumman, Lockheed, Martin, McDonnell, North American, Northrop, and
Republic). The document asked that interested concerns notify Wright Field by
10 January 1955 and plan to attend a special briefing on 18 January.
Attached to the letter were a general preliminary outline specification, an
abstract of the NACA preliminary study, a discussion of power plant requirements
and development levels, a list of data requirements, and a cost outline statement.
Each bidder was required to satisfy various requirements thus set forth, except in
the case of the NACA abstract which was presented as "representative of possible
solutions." 20
Grumman, Lockheed, and Martin expressed slight interest in the competition and did
not appear at the 18 January briefing. Subsequently, between that date and the 9 May
deadline for the submission of proposals, Boeing, Chance-Vought, Convair, Grumman,
McDonnell, and Northrop informed AMC that they would not participate. This left Bell,
Douglas, North American and Republic as competitors.
Activity in the interim was varied. The contractors concentrated on the assembly of
attractive proposals. In the course of this effort they had frequent recourse to the
advisory services of both WADC and NACA. Concurrently, project officers (in the New
Developments Office, Fighter Aircraft Division, Directorate of Weapon Systems
Operations, which had been assigned full responsibility for the balance of the
competition) attempted to refine an evaluation procedure acceptable to all concerned
and sent supplemental data to the participating contractors. Of these tasks, the
evaluation procedure loomed larger. Headquarters ARDC in early February emphasized
the extreme importance of resolving all possible differences of opinion on the conduct
of the technical evaluation; to this end, ARDC instructed that the ultimate
recommendation reflect the opinion of NACA as well as that of WADC. Plans had been
laid for submitting the evaluation rules to the Joint Steering Committee for
approval. 21
Supplemental instructions to contractors reemphasized the urgency of the two and
one-half year development period of the X-15. b
The project office also relaxed very
slightly the rigid limitations on engine selection, instructing competitors that
"if ... an engine not on the approved list offers sufficient advantage, the
airframe company may, together with the engine manufacturer, present justification
for approval to the WSPO
(Weapon System Project Office)." 22
The Power Plant Laboratory had originally listed the XLR81 and the XLR73, the
XLR10 (and its variants - a compound XLR10 and a modification of the XLR30), and
the NA-5400 (a North American engine in early development, still lacking a military
designation) as engines that airframe competitors could use in their designs.
Early in January, the laboratory had become concerned that the builders of engines
other than those listed might protest the exclusion of their products. Consequently
there emerged from the Liquid Rocket Section of the laboratory an explanation and
justification of the engine selection process. It appeared that the engineers had
confidence in the ability of the XLR81 and XLR73 to meet airplane requirements,
had doubts about the suitability of the XLR25 (a Curtiss-Wright product), and held
the thrust potential of the XLR8 and XLR11 (similar engines) in low repute. This
for practical purposes exhausted the fund of Air Force-developed engines suitable
for manned aircraft. Navy consultants had introduced the other two engines defined
as acceptable in terms of the competition. 23
At about the time the industry briefing was held, the project office began
seriously to consider sending copies of the bid invitation to "appropriate engine
contractors." The Power Plant Laboratory discouraged unlimited distribution because
of the possible compromise of proprietary data, but suggested that limited
information be circulated and that inquiring contractors be informed what the
Air Force had said about their own engines. 24
A course similar to this eventually
was adopted; on 4 February each of the prospective engine contractors earlier
identified (Reaction Motors, General Electric, North American, and Aerojet) was
asked to submit a suitable engine development
proposal. 25 Even earlier, certain of
the engine contractors had been contacted for specific information about the
engines originally listed as suitable for the X-15
program. 26 This information,
relating to design and performance details, was distributed to all four prospective
airframe contractors. 27
Data on the North American NA-5400 was scant, and the
Reaction Motors XLR10 received a "not recommended" classification (at the suggestion
of the engine contractor himself).
Progress in the completion of evaluation arrangements was less rapid than had
originally been anticipated. A 1 March deadline established by ARDC early in
February was later extended to 1 April, and the material itself did not leave
Wright Field until 11 April. 28
Nevertheless, by that time the evaluation rules
had been fully coordinated within WADC and with NACA.
The burden of the evaluation
process fell on the project office, the WADC laboratories, and NACA - in that order.
AMC and the Navy were to play subordinate - though still significant - roles. Four
evaluation areas were specified: performance, technical design, development
capability, and cost. 29
Headquarters ARDC forwarded the WADC evaluation plan to Air Force headquarters
for approval and then advised WADC that the Research Airplane Committee planned
to meet at Wright Field on 17 May to examine the submitted designs and to review
evaluation arrangements. ARDC also suggested that commitments be obtained from the
various engine contractors as early as possible so that the engine program would
not adversely affect the selection of a winning airframe
design. 30
On the appointed day, 9 May 1955, Bell, Douglas, North American, and Republic
submitted their proposals to the project office. Two days later the technical
data went to the several laboratories with a request that evaluation results be
reported by 22 June. On 17 May the bidders made separate presentations to the
Research Aircraft Committee and to a group of senior officials from WADC, ARDC,
headquarters USAF, NACA, and the Air Force Flight Test Center. Later that day the
Research Aircraft Committee confirmed previous arrangements for the evaluation
procedure. Subsequently, both the Bureau of Aeronautics (Navy) and NACA independently
accepted the resultant evaluation plan. Bureau of Aeronautics took pains. to insure
that Navy and NACA consultants participated in the joint
evaluation. 31 Later
arrangements insured that engine evaluations, also coordinated with the Navy
and the NACA, would be available by 12 July. 32
The final evaluation meeting, to consider the results of earlier examinations
and comments, was scheduled for Wright Field on 25 July. In the interim, there
was established a free interchange of preliminary opinion between Bureau of
Aeronautics, NACA, and WADC laboratory and project office
elements. 33 Notwithstanding
this advance coordination, the evaluation results were delayed, first by the
interference of higher priority work at WADC, later by a need for formal coordination
with Bureau of Aeronautics. 34
By 5 August, the various portions of the evaluation had been completed and the
evaluation report had identified North American's proposal as having considerably
greater merit than any of the others. c
On 12 August the Research Aircraft Committee
accepted the findings. Preliminary moves to Confirm this decision and to award a
design contract to North American hit a sudden snag, however, when on 23 August
North American's local representative verbally notified the Fighter Aircraft
Division that the firm was withdrawing its proposal because of the press of other
work. 35
The immediate reaction of Wright Field was to inform everybody concerned
that the evaluation results would have to be reexamined. (No contractors had yet
been notified of the outcome.) On 30 August, the contractor officially and in
writing confirmed his earlier announcement, citing inability to perform the work
in the time allotted and recent awards in interceptor and fighter-bomber
competitions plus a heavy F-107A workload as the motives. Within a week the
project office (and the directorate) had decided that North American should
be asked to reconsider the decision. But there was agreement that if the company
held firm, Douglas would probably be ruled the competition winner, although the
Douglas design (which employed magnesium instead of Inconel X) would require
considerable modification before it satisfied NACA and USAF
requirements. 36
During the middle weeks of September, both NACA and Air Force officials discussed
with North American possible continuance of the contractor's X-15 activity. Dr.
Dryden of NACA and Brigadier General H. M. Estes of the newly formed Directorate
of Systems Management d
had prominent roles in these negotiations. A presentation
of the X-15 program at the Department of Defense level, on 14 September, induced
a recommendation that the program be approved. Concurrently, however, two changes
in philosophy appeared. First, the Army representative at the conference said
flatly that the Army would oppose the project if it required special Department
of Defense funds. This stand prompted an attempt to reduce program costs below
earlier estimates. At the same time, it began to appear inevitable that the
program would take more than the 30 months originally projected. On this basis,
it seemed that North American might still be considered a competitor. The
contractor's reluctance to proceed was frankly based on the thesis that the
company could not devote sufficient effort to the X-15 project to permit its
completion within the span of time initially provided. 37
On 20 and 21 September, contacts with Air Force headquarters confirmed earlier
information that the Department of Defense had approved the project and North
American's selection. But before any formal contract negotiations could be authorized,
said the Department of Defense, a reduction in annual budget requirements would be
necessary.
As these instructions reached Wright Field, General Estes was conferring
with Mr. J. L. Atwood, North American's president. Mr. Atwood told the general that
his company would reconsider its decision on the X-15 if the program were extended
by eight months (to 38 months). Two days later, on 23 September, this offer was
made officially. North American emphasized, however, that a program extension
was essential to the company's accepting a contract. 38
On 27 September, Air Force headquarters agreed to this condition and canceled
earlier instructions to negotiate a reduction in the contractor's fee. Information
on the decision reached the center on 28 September; on the last day of that month,
letters went to North American and to the unsuccessful bidders, officially advising
them of the outcome of the competition. 39
Price negotiations followed. Wright Field project officers took the results of
preliminary contact with North American (and with Reaction Motors, the prospective
engine contractor) to a Pentagon meeting of 11 October. By that time the
contractor's estimate of project cost had been reduced from $56,000,000 to
$45,000,000 and the maximum annual funds requirement from $26,000,000 to
$15,000,000. The USAF Directorate of Research and Development made a
presentation of these figures to the Department of Defense Coordinating
Committee on Piloted Aircraft on 19 October. The result was a committee
decision to support the project. Shortly thereafter, the Department of
Defense released the funds needed for the start of work. More meetings
between NACA, project office, and North American personnel were held on
27-28 October, largely to define changes to the aircraft configuration
originally submitted by the contractor. On 7 November, the AMC Directorate
of Procurement and Production took the first steps toward issuance of a
letter contract, by 9 November the principal clauses of that document had
been composed, on 15 November it received the approval of the procurement
directorate, on 18 November it was sent to North American, and on 8 December
the contractor returned an executed copy. 40
At that point, about $2,600,000
was available to fund initial activity; a total contract cost of $39,000,000
was foreseen for design, development, three X-15 aircraft, and a flight
demonstration program. 41
On 1 December 1955, a series of actions designed to produce an engine
contract began. 42
A letter contract with Reaction Motors became effective
on 14 February 1956. Its initial allocation of funds totaled $3,000,000,
with an eventual expenditure of about $6,000,000 foreseen as necessary for
the delivery of the first flight engine. 43
A definitive contract for North American was completed on 11 June 1956,
superseding the letter contract and two intervening amendments. To that
time, $5,315,000 had been committed to North American, in three increments,
under the letter contract. (Essentially, North American had been given
$2,715,000 more than the initial allocations.) The definitive contract
of June contemplated the eventual expenditure of $40,263,709 plus a fee
of $2,617,075. For this sum, the government was to receive three X-15
research aircraft and other specified items: a high speed and a low speed
wind tunnel model program, a free-spin model, a full-size mockup, propulsion
system tests and stands, flight tests, modification of a B-36 carrier, a
flight handbook, a maintenance handbook, technical data, periodic reports
of several types, ground handling dollies, spare parts ($100,000), and
ground support equipment ($200,000). Exclusive of contract costs were
fuel and oil, special test site facilities, and expenses incident to
operation of a B-36 carrier. Delivery date for the aircraft and support
equipment was to be 31 October 1958. 44
A final contract for the engine, the prime unit of government furnished
equipment, was effective on 7 September 1956. Superseding the letter
contract of February, it covered the expenditure of $10,160,030 plus a
fee of $614,000. e
For this sum, Reaction Motors agreed to deliver one
engine, a mockup, reports, drawings, and tools. The engine described in
the final contract was to have a maximum thrust of 50,000 pounds, to
include provisions allowing for inflight thrust variation between 30 to
100 percent of maximum output, to be capable of 90 seconds operation at
full thrust and 4 minutes 9 seconds at 30 percent thrust, to weigh 618
pounds (without fuel), and to have a specific impulse of 241 (pounds
of 45 thrust per pound of fuel per second). 45
