Whereas procurement of the B-70 was doubtful even before the prototype flew, the next aircraft designed as a B-52 replacement came much closer to actually entering service’ and did in fact eventually lead to a derived production model. The General Dynamics FB-111A was bought as a replacement for the B-58 and some early B-52s, but although this gave SAC a modern medium bomber, the FB-111 was too small and short-ranged to meet all the service’s needs. Throughout the 1960s, the USAF investigated various heavy bomber concepts, coming to concentrate on an aircraft that could evade Soviet defences by flying fast at low level, while retaining a high-altitude dash capability. Under the Advanced Manned Strategic Aircraft program, Rockwell International, Boeing, and General Dynamics all put forth competing designs, and in 1969, an airframe contract was awarded to Rockwell, with General Electric to build to the F101 turbofan engines to power it. The new aircraft, to be designated B-1A, was a variable-geometry, four-engined design suitable for both high and low-level missions, and optimized for survivability in a nuclear environment.
Originally, the B-1A was intended to have a supersonic capability on the deck, but this requirement was lowered to Mach .85 to allow the use of lower-cost aluminium structures in place of the titanium that would otherwise be necessary.
One of the principal weapons of the B-1A was to have been the AGM-69B SRAM-B. This improved missile was to have a more powerful motor and a new W80 warhead in place of the AGM-69A’s W69. The new W77 gravity bomb was also being developed for use by the B-1A, and the aircraft would also be suitable as a carrier for the new Air Launched Cruise Missile. The B-1A had three weapons bays with rotary launchers, and production aircraft would have had the capability to carry ordnance on two external pylons.
Procurement plans for the B-1A called for the purchase of no fewer than 240 aircraft, to be put into service by the early 1980s. Although small compared to the bomber programs of the 1940s and 1950s, this would nonetheless allow for a roughly one-for-one replacement of the latest B-52 models with an aircraft at least twice as effective.
Rockwell’s Plant 42 at Palmdale, California was where the B-1s were assembled, with rollout of the first prototype taking place in October 1974. Originally, there were to be six flight test aircraft, but defense cutbacks later reduced this figure to four. The first flight of a B-1 occurred on 22 December 1974, and by March 1976 three aircraft were flying.
SAC’s plans were derailed in June 1977, when President Jimmy Carter announced that procurement of the B-1 would not go forward. Carter, who had never been a proponent of the costly program, believed that the AGM-86 ALCM would keep the B-52 viable until the Advanced Technology Bomber became available in the 1980s. Construction of the incomplete fourth prototype was allowed to proceed; this aircraft, 76-0174, flew in February 1979, and was distinguished externally by the Cross Eye ECM system, with its large dorsal fairing. This aircraft also lacked the escape capsule of the earlier prototypes, having conventional (and less heavy) ACES II ejection seats. Cross Eye was later removed.
Following their use as B-1B flight test articles, two of the three surviving B-1As became museum articles, while the third was dismantled and used as an electromagnetic testbed by the Rome Air Development Center.
Photo of the third B-1A launching an AGM-69 SRAM Aviation Week & Space Technology November 21, 1979 p.15
Graham Wilmer “From B-1 to LRCA” Air International July 1982 includes several color shots of the camouflaged fourth prototype
The Encyclopedia of World Air Power Bill Gunston, editor 1980 p.304: B-1A 3-view
Michael J.H. Taylor Warbirds Illustrated No. 30 Strategic Bombers 1945-1985 p.2-3: Photo of the second B-1A, fitted out as a partial B-1B prototype, seen taking off.