Updated: F-108 Mission (Below Original Post)
B-52 vs. Flying Wing?... B-70 Canceled: Why?... What exactly WAS the F-108 'Mission'?In a recent comment thread, three questions were raised as to the facts surrounding 50s-60s aircraft program histories. Normally I would blow off trying to address such diverse issues even those as narrowly defined, in one post. But it just so happens all involve information I already know via sources I’ve already acquired for other purposes.
|Last of the '49's: YRB-49A in flight|
Flying Wing Was an option to B-52 DevelopmentAs I showed in an earlier post, the B-52 for a while faced extinction until a program cancellation decision was fortunately reversed. One of the B-52’s competing concepts, contrary to what you may have been told, was the Northrop B-49 flying wing, a jet variant of the earlier propeller-driven theme. Fielding the ‘flying wing’ would have been the fruition of Jack Northop’s lifelong dream, but alas it was not to become true until after he passed away. He did die knowing the wing WOULD fly in the form of the B-2 Bomber. I could detail ‘why’ the flying wing was B-52 competitor but that is beyond the scope of this post. To the sources we go!
The year 1948 began under a dark cloud for AMC’s B-52 program managers. Air Staff officers succeeded in canceling, not simply Boeing Model 464-29, but the entire Boeing heavy bomber program due to doubts about the B-52’s ability to achieve the required range and speed. Some Air Staff officers preferred the Northrop YB-49 turbojet powered all-wing aircraft over Boeing’s conventional B-52 design: others favored opening a new competition for a heavy bomber. (Mandeles, pg 49)
Craigie added that AMC analyses of other studies of optimum airplane performance relied on extrapolations from past performance. However, these extrapolations were unreliable because aeronautic and aerodynamic knowledge was growing so quickly. Therefore, it was necessary to use the most current data and knowledge, which did not necessarily involve only extrapolations of past performance. For instance, he noted, that in 1941 Douglas Aircraft Company analyzed the predicted performance of the B-36, and concluded that the requirement of a 10,000-mile range with a 10,000-pound payload was unlikely to be achieved. The Air Force and Convair, however, used improved weight control and planning, and proved the study wrong. Despite increases in armament, radar, equipment, and the difficulty of development under wartime conditions, Convair and the Air Force produced an airplane which could meet the Air Force’s objectives. Craigie also urged discarding the alternatives to the B-52-the XB-35 and YB-49 Flying Wing and delta-wing designs. By May 1947 the delta wing did not have any marked superiority over a conventional airplane for long-range, high -speed operation. Craigie wrote that a reevaluation of these designs should be made only when “jet engine specific fuel consumption is reduced to a point to permit their [sic] use” in a bomber. (Mandeles, pgs 75-76)
At AMC, senior officers attempted to save the B-52. Maj Gen Franklin O. Carroll, AMC’s director of R&D, analyzed Northrop’s claims of superiority for the Flying Wing, and found them wanting. The basic premise for proponents of the all-wing aircraft was that the space requirements for military stores matched the space available in the optimum wing. Under this assumption, the all-wing aircraft would be more efficient than the conventional airplane. Carroll, however, argued that Northrop seriously underestimated the space needed for military stores. More space would be needed in the aircraft, and adding a body or nacelle to contain the extra military stores would vitiate the theoretical advantages of the all-wing design. The YB-49 Flying Wing also demonstrated longitudinal instability at high speed. Little was known about this instability and it could present severe engineering difficulties. The flying wing would not be versatile in a tactical setting and would be overly sensitive to changes of center of gravity caused by the position or absence of cargo. Such problems seemed not to justify reliance on the all-wing design. Carroll concluded by recommending the conventional Boeing design and that the B-52 be accorded the highest support from Air Staff. (Mandeles, pg 83)
Several days after the Symington-Allen meeting, Craig, Frederic Smith, and Craigie decided that “if the B-52 meets the requirements of the contract under which it is being bought, it will satisfy strategic requirements.” These requirements included unrefueled range of approximately 8,000 miles and a cruising speed of 500 MPH over 4,000 miles of enemy territory. 103 Boeing Model 464-35 (fig. 4) matched these strategic requirements, and Air Force Undersecretary Barrows confirmed the decision to retain Boeing as prime contractor of the heavy bomber rather than adopt the Flying Wing in early March. (Mandeles, pg 83)
Partridge and Craig urged the staff to stand firm, noting support from RAND and the National Advisory Committee for Aeronautics for the Flying Wing design. At Symington’s urging, Allen agreed to give the Flying Wing due consideration. After further discussion, key members of the Air Staff met on February 14, 1948, and decided to keep the Boeing contract and issue a change order. Undersecretary Barrows concurred in the action. Despite the painful experience, the B-52 program had been radically redirected and was now aimed at fulfilling a new concept of strategic air operations. Thus even before the Aircraft and Weapons Board met in January, two of the major proposals up for consideration had already been approved. Both the B-36 and the B-52 had received a new lease on life, as had, incidentally, the Northrop YB-49 Flying Wing. (Moody, Pgs 182-183) Note: 'Moody' is a huge PDF file.Read the complete sources for more information illustrating the point that the flying wing, specifically the YB-49 version was ‘competition’ for the B-52, and the whys and hows the B-52 came out on top.
Why was the B-70 Not Pursued?
|North American XB-70 'Valkerie'|
That the B-70 was cancelled because of ICBMs and the existing capabilities of the B-52 being sufficient is easily shown, but I’m not going to type the proof out, just show it in situ:
|Source (can't find my copy dangit!): |
"Politics and Force Levels: Politics and Defense Inside the Kennedy Administration", Pg 216
The F-108 Rapier Mission? Long Range InterceptorIf one believes in infallible ‘fact sheets’ the F-108 according to one 'fact sheet', was to have two missions: Long Range Interceptor and Escort Fighter for the B-70. Evidence supporting the escort mission assertion is so thin, it is ’invisible’, while evidence supporting the Interceptor role is bountiful.
|XF-108 Rapier: Never Reached Beyond Mock-up Stage|
Most critically, given the nature of the operational concept envisioned for the F-108 and planned end strength, the use of the F-108 as an ‘escort fighter’ would probably be less likely than the F-106 it was designed to replace. This too is easily shown. And now it will be shown, thanks to my serendipitous and very slight connection to the author of the following in his 1988 ACSC paper titled: “The Search for an Advanced Fighter: a History From the XF-108 to the Advanced Tactical Fighter”.
Then Major (later Colonel) Robert Lyons wrote (beginning on Page 4):
The MX1554 "Ultimate Interceptor, 1954" produced the Convair F-102 that fell far short of the planned speed, altitude, and range performance (95:159-165). It could only fly at 677 Knots at 35,000 feet, with a maximum ceiling of 51,800 feet and 566 nautical mile combat radius (95:173). While the F-102 and its follow-on F-106 served as "interim interceptors," the Air Force developed requirements for a long range interceptor. These long range interceptor requirements, first developed in April 1953, were rewritten in July 1955 and November 1956, after several attempts failed to get an acceptable proposal from competing airframe contractors (114:Ch 2). The Air Force sought an interceptor to counter the perceived 1960 bomber threats of Mach 2.0 speed at 61,000 feet, and the revised 1963 bomber threats of Mach 2.2 to 2.7 speed at 65,000 feet (118:7,32; 114:Ch 2). Design studies to satisfy these requirements began in 1953 at Air Research and Development Command and in industry with the MX1554 designed to achieve a Mach 4.5, 150,000 pound Gross takeoff weight aircraft, but the aircraft appeared to lie beyond the state of the art (118:7,Fig 24). So another round of design studios attempted to meet the 1955 LRI (long range interceptor) requirements. These studies called for an aircraft with a cruise speed of Mach 1.7 at 60,000 feet and combat speed of Mach 2.5 at 63,000 feet, with a gross takeoff weight of 98,500 pound, But this aircraft would have had only marginal capability against the postulated 1963 bomber threat (118:7,Fig 24).
A subsequent design competition in 1955 between Lockheed, Northrop, and North American was little better than previous ones, but North American came closest to meeting the goals, (114:23).
North American Aviation's letter contract of 6 June 1956 called for a long range interceptor that could operate at 70,000 feet with a combat speed of at least Mach 3. The all-weather interceptor aircraft was to have two engines, two crewmen, and at least two internally carried nuclear or conventional air-to-air missiles (95:330-331). Their Weapon System 202 configuration sported a single vertical tail and large delta wing, and was adopted in 1958 after considering iterations with as many as three vertical tails and a large canard (118:7, Fig 24; 95:331).
In 1960, toward the end of the heyday of the "Century Series" fighter aircraft, Weapon System 202, renamed the XF-108 Rapier interceptor, promised to serve the Air Force with a Mach 3 cruise speed and 1,000 nautical mile range as a companion to the proposed B-70 supersonic bomber (106:44). [SMSgt Mac Note: I believe the fact that the Rapier was based on common design concepts with the B-70, coming out of the same design stable and discussions concerning the parallels in performance parameters may be as much of a source of ‘escort’ fighter role stories for the F-108 as any other. ] The XF-108 design evolved to meet all of the expected Soviet bomber threats of the early 1960s. It was to have been fabricated from stainless steel sheet, a welded sandwich and honeycomb, rather than aluminum to withstand the high temperatures and stresses of sustained supersonic flight. Its two General Electric J93-5 turbojet engines were to have used a special high energy synthetic fuel (ethyl borane) (7:14). It would also use the ASG-18 Fire control system, and the GAR-9 missile. All these were under development simultaneously with the basic airframe. This combination of features allowed a totally new concept of long range interception of the supersonic bombers believed to be under development by the Soviet Union. The F-108, with its superior radar and high speed missile, was to patrol the DEW (Distant Early Warning) Line and make SAGE (Strategic Air Ground Environment) directed, semi-autonomous interceptions well before incoming bombers could launch their weapons against the major cities of Canada or the United States (118:7-8,Fig 25-26,Fig28-30).
But intelligence sources eventually proved a serious Soviet bomber threat did not exist. That news reinforced growing concerns in the Department of Defense (DoD) over the cost and viability of manned aircraft. Offensive and defensive missiles now seemed to be the logical technological choice for the 1960s (7:14; 8:7). In August 1959 the Air Force canceled the chemical fuel development program (7:14), and on 23 September canceled F-108 development (94:402; 8:7). The Air Force announced that the program had no technical difficulties and had met all goals it the time of cancellation, but that there was a shortage of funds and programming priorities had changed (57:63). Both the fire control system and the missile developments continued at a lower level of Funding. The cost estimate of five to eight billion dollars for a few squadrons of F-108s was more than could be accepted to replace the F-106, given the doubtful nature of the threat (7:14) and the unresolved fate of future manned aircraft.
With the cancellation of the F-108, there appeared temporarily to be a hiatus in supersonic interceptor work in the United States. Indeed, although the Air Force continued trying to gain support for new interceptors in general and the F-108 in particular, the DoD continued to oppose the requirement pending verification of a threat (9:3).
7. Air Force Times. 15 August 1959, p. 14.
8. Air Force Times. 3 October 1959, p. 7.
9. Air Force Times. 11 March 1964, p. 3. 57. "F-108 Cancelled." Canadian Avionics (November 1959), p.63.
94. Kennedy, William V. "Future of the Fighter." Ordnance (January-February 1970), pp. 402-406.
95. Knack, Marcelle Size. Encyclopedia of US Air Force Aircoraft and Missile Systems Volume1. Washington, D.C.: Office of Air Force History, 1978.
106. McCormacK, James, Jr., Maj Gen, USAF (Ret). "How the Air Force Is Buying Its Newest Manned Weapons." .Skyline (Fall 1958), pp. 44-47.
114. "NORAD's Quest for NIKE Zeus and a Long-Range Interceptor."(U). Ent AFB, CO: HQ NORAD/HO, 1962. SECRET-Declassified 31 December 1962. "Unclassified information only used from this source."
115. Neufeld, Jacob. "The F-15 Eagle: Origins and Development 1964-1972." (U). Pentagon, Washington, D.C.: HO USAF/HQ November 1974. SECRET "Unclassified information only used from this source."
118. Parsons, T. R. "B-70 and F-108 Perspectives on Supersonic Cruise." .Proceedings of the Conference Ob the Operational Utility of Supersonic Cruise (U).Wright-Patterson AFB, OH: ASD/XR, May 1977. SECRET.-Declassified "Unclassified information only used from this source."From the combination of the limited number of F-108 platforms, the operational concept of roving long-endurance patrols conducted at the farthest distances from home with limited and possibly nuclear payloads, as well as the intended purpose of replacing ‘interim’ interceptors, it is doubtful the F-108 would have had time for anything other than its interceptor role. If the Rapiers were to be ‘escort’ fighters at all, it would be in accompanying aircraft returning post-nuclear strike that might wander/enter their patrol areas, in a manner of what ANY fighter or other aircraft would do.
Updated 26 April 2012:
The "Standard Aircraft Capabilities" of the F-108Commenter BB1984 below reminded me of another public resource we can draw on in evaluating the accuracy of the Air Force’s F-108 ‘fact sheet’. Based upon review of the F-108’s Standard Aircraft Capability (SAC) sheets, from the earliest available at the resource (2 May 1958) to the last one available, 12 June 1959 (which was less than 6 months before the program was cancelled) we find two key points:
The primary mission of the F-108 weapon system is to deter armed attack against the U.S. and its area of defense responsibility by providing maximum defense potential against all airborne threats in the post-1962 time period. This defense function is implemented by the F-108’s potential to search out, evaluate, and destroy these hostiles at ranges beyond the capabilities of other defense systems. The F-108 is designed to operate not only in conjunction with SAGE and in cooperation with other weapons in the defense inventory, but to be equally effective well beyond the bounds of ground environment surveillance and under minimum operational control, relying on its self-contained high performance search, navigation, and communications equipment.
In time of war, F-108 operations can include directed intercepts and organized search missions resulting in repeated attacks with up to three kills by each interceptor. Operating beyond SAGE, the F-108 can make positive identification of DEW line violations, attack and trail hostile raids through remote areas, and report directly via long-range radio. Operating within the ZI, the F-108A performance features of all-weather capability, long range at Mach 3, and 15-minute turn-around, permit flexible commitment of forces to achieve the precise concentration of power required at any battle area with maximum retention of reserves.
The F-108A carries two crewmen and internally stowed missile armament. This high performance air vehicle cruises and combats at mach 3 with a 1000-nautical mile radius on internal fuel. It has a 1.2g maneuver ceiling in excess of 77,000 feet and a zoom-climb ceiling of 100,000 feet. Under normal loading and weather, the air vehicle requires runway lengths of only 3200 feet for take-of and landing. It can be operated from 6000-foot runways in all conditions of weather. From a nominal 70,000 foot combat altitude , missile launch can be accomplished against any air-breathing target flying at altitudes from sea-level to 100,000 feet. The pulsed-doppler radar, with 40-inch antenna, provides target detection in excess of 100 nautical miles at all altitudes and is backed up by infrared search and track devices.
|12 Jun 59 Standards Aircraft Capabilities Sheet, Weapons Sections|