No. The last one was the Space Shuttle, which was problematic as you know.
SAo, the B-52 gravity-dropped drones and X-15’s, which then rocket-boosted upwards in “space” - although few (if any ??) had a large enough booster to do more than coast up, get data, then drop back.
The SR-71 launched drones into Chinese airport at mach + speeds. Those were horizontal flight only.
The B-58 Hustler could drop loads at Mach + speeds, so we know the physics and aerodynamics of Mach+ separation pretty well, even back in the mid and late 60’s. Didn’t always work though - the SR-71 drones did have at least 2 failures that I know of.
Could the Valkyrie bomber - which could carry loads internally as large and as heavy as the B-52 could but do it supersonically and to much higher altitudes - carry a meaningful boosted-rocket payload into space? Seems that getting a payload to 75,000 feet and Mach 1. to 2.0 - even if the flight itself were short-ranged - would be a substantial improvement at the cost of refurbing the plane now museumed into oblivion.