A budget status chart at the end of the report for Phase 3 indicated that Work Order 540 would run through July 1965 with an overall budget of $165,000, and approximately $110,000 had been spent for the first three phases. However, no status reports beyond Phase 3 were found in researching this article. The gap, however, is covered by follow-on design work that was initiated in August 1964. The results of this work were presented to Air Force Systems Command in March 1965 in a report titled Manned Hypersonic Vehicle Study.
The Manned Hypersonic Vehicle study
a) summarized the work done in the previous phases for Mach 4 to 6 designs
b) then addressed two classes of Mach 6 to 12 hydrogen-powered designs.
The first class, called Early Availability, consisted of vehicles with conventional propulsion systems, including currently available turbojets and subsonic combustion ramjets.
The second class, called Later Availability, consisted of vehicles with advanced propulsion systems, including advanced turbojets and supersonic combustion ramjets.
None of the designs were B-58 parasites, which is not surprising since Secretary of Defense Robert McNamara formally announced the retirement of the B-58 program in late 1965.
The Later Availability vehicles were based on engine and structural advances as applied to Configuration C-3. These advances included supersonic combustion ramjets and advanced turbojets. These designs, which were not detailed and not pursued, according to Kent, would be capable of reaching orbital velocities.
