This is an old solution to an old problem (e.g ramjet thrust chasm), see SA-2S in the link
http://www.codeonemagazine.com/article.html?item_id=92
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Phase 3: A Recommendation
Phase 3 began with an evaluation of alternatives to the modified B-58 as a launch platform for VS-4. The first alternative consisted of attaching the second stage of a SCOUT rocket to the underside of VSF-4 and air-launching the parasite/rocket combination from a B-52. The Lockheed D-21 drone would later be launched in this manner. SCOUT, an acronym for Solid Controlled Orbital Utility Test, was the first US-built solid-fuel rocket capable of launching a satellite into a 500-mile orbit. The second alternative consisted of ground launching VSF-4 atop the first stage of an LGM-30 Minuteman I missile. The Minuteman I was a three-stage, solid rocket-powered intercontinental ballistic missile designed to deliver nuclear warheads.
These launching alternatives led to a variable-sweep, self-accelerator version of VSF-4, which was called Configuration SA-2S. This configuration was an enlarged version of VSF-4 powered by two Pratt & Whitney J52 turbojet engines for takeoff and cruise. A solid rocket, the first stage from a SCOUT rocket, was used to accelerate the aircraft to supersonic speeds necessary to start its two Marquardt ramjet engines
SA-2S had a takeoff weight of 92,000 pounds, a pre-zone range of 2,100 nautical miles, a zone range of 4,000 nautical miles, and a post-zone range of 2,700 nautical miles. It cruised at Mach 5 and 95,000 feet. Fuel weight was 37,600 pounds. The aircraft was 87.5 feet long and 16.7 feet tall. The wingspan was 35.0 feet with the wings swept for high-speed flight. Wingspan was 60.3 feet with the wings extended for low-speed flight. Several turbojets and booster rockets, some under development, were studied as alternative powerplants to improve performance."
