'Riding a shockwave' was the brainchild of Alfred J Eggers, an aerodynamicist at NACA who pondered the prospect for trapping airflow underneath a supersonic wing by boxing in the flow between an expanding body underneath it and downturned wingtips...while mowing his lawn in Virgina!
This gives you some idea of the size of the XB-70. This 'authorised' engineer is walking down the port air intake.
The escape capsule with 'clam shell' doors sealed when activated maintaining pressure and oxygen during the high altitude portion of the descent. Unfortunately in the fateful crash of June 8 1968 they severely crushed pilot Al White's arm in the process.
At 15,000ft a parachute was deployed from the capsule. Once on the ground the crew member had access to cold-weather clothing, food for several days and in case the capsule landed in water, it would float like a boat and was equipped with fishing tackle and a life raft.
Similar equipment was carried in the B-58's escape capsule, but the mechanism of closing was different, utilising multiple sliding panes.
Another hypersonic egress capsule was designed for the Republic XF-103. Looking like a large shoe, one curved panel slid up the dorsal curvature to provide a seal. The final design is illustrated in the middle photo. The bottom photo capsule was built for drop testing. During the drop test it was revealed that the parachute was too small and was ripped to shreds.
(I'm unaware of what protective devices were provided for pilots of the North American X-15 and XF-108 Rapier)