Why is this rocket firing upside down?

All “large” solid rockets, such as the Shuttle boosters, are manufactured in segments and assembled at the launch site. In the early 1960s we looked into “cast-in-place” technology where a one-piece motor casing would be filled with propellant at or near the launch site. I worked on designs for 260-inch diameter motors of the segmented and monolithic configurations. In 1965 Aerojet cast a 260-inch motor in place at a facility near Miami, FL. It was test-fired in the hole it was cast in and that is the picture on the cover of this brochure.

Getting the right performance characteristics and mechanical properties in the propellant “grain” (as it is called) of a solid rocket motor is a complex task of blending the ingredients and curing the resulting mixture under carefully-controlled environmental conditions. Doing this with a single piece of rubber binder, ammonium perchlorate oxidizer and powdered aluminum that weighs a million pounds magnifies the problem, and no solid rockets approaching the size of the 260-inch one tested in 1965 have been built since.