Commentary by the Editor: As you can see; you can safely escape from an aerospace vehicle travelling at Mach 3 at 75,000 feet and above using an ejection seat.

So why did North American design the B-70 with escape capsules? It is my opinion that this was a SAC requirement – for an environment on the B-70's flight deck in which shirt-sleeved personnel could survive and continue to fly the aircraft, even with a loss of air pressure. USAF regulations of the time (and still do today) required a pressure suit for operations above 50,000~ feet. From experience with pressure suits on the B-36, B-47, and B-52; SAC knew that wearing them was tiring to crews; yet they were needed in case of a loss of cabin pressure.

The escape capsule that North American came up with was their solution to the problem, because the capsules had a window in their front sections, and provisions for control of the aircraft from within the capsule; so if cabin pressure were lost at 75,000 feet; the crew would simply encapsulate, and pilot the plane down to 17,000 feet or so from inside their capsules.