What is aj 10 engine?

The AJ-10 engine is a family of rocket engines developed by Aerojet Rocketdyne. It was originally designed for use in ballistic missiles in the 1950s, but has been adapted for use in several space launch vehicles, including the Delta II and Delta IV rockets. The engine uses RP-1 (kerosene) as fuel and liquid oxygen as oxidizer, with thrust ranging from 50,000 to 200,000 pounds. The AJ-10 engine has proven to be a reliable and versatile workhorse of the US space industry, with over 500 units built and over 450 successful missions.