When I was in the Air Force and going to tech school at Lowry AFB, in Denver, Colorado, 1966, there was a fixture outside with a ejection seat fitted.
Cadets from the Air Force academy would come up in groups and get strapped into the seat and shot up the fixture about 50 feet, then slowly lowered back to the bottom.
I don't know what they powered the seat with, compressed air, or a charge.
This was just to get them familiar with the forces of ejection.
Sometimes someone would not be positioned just right and get injured, and they'd leave on a stretcher.
Watching this was a popular pastime, I was there almost a year, and witnessed these ejection familiarizations twice.
Both times at least one Cadet was injured.