Up until the late sixties there was no rocket assistance. They retrofitted the F-4 Phantom Martin-Baker Mk.5 seats with the M-B Mk.7, which had rocket assistance. This gave it zero-zero capability which was essential if strapped into a stationary aircraft which was on fire.

As a result, the gun (or catapult, as it was frequently referred to) could be less powerful, being needed only to provide the initial acceleration to clear the tail fin in flight so injuries were lessened. The rocket pack continued the acceleration to gain height sufficient for man/seat separation and parachute deployment from a standing start.

Early M-B (and other manufacturer’s too) non-rocket seats were justifiably called back-breakers and many injuries were sustained due to a less-than-perfect posture and the massive instantaneous ‘g’ when the ejection took place. However, it was better than staying with the aircraft! The limitations of what a man could stand when ejected with a gun only were at their limits and with the increasing speeds of aircraft and the requirement to be clear of the fin when in flight, it was essential and accepted that another solution needed to be found. Rocket assistance solved the problem and some crew members went through two or even three successful ejections with the later seats and survived to fly again.

Notwithstanding the above, whatever seat you ejected in, if you did it in anger it was going to be a hard ride – rocket powered or not.

Anon.