AJ-60A

AJ-60A is a solid rocket booster produced by Aerojet Rocketdyne. Up to 2020 they were used as strap-on boosters on the United Launch Alliance Atlas V rocket.

History
The AJ-60A rocket motor was developed between 1999 and 2003 for use on the Atlas V.

On January 19, 2006 the New Horizons spacecraft to Pluto was launched directly into a solar-escape trajectory at 16.26 km/s from Cape Canaveral using an Atlas V version with 5 of these SRBs and Star 48B third stage. New Horizons passed the Moon's orbit in just nine hours.

In 2015, ULA announced that the Atlas V will switch to new GEM 63 boosters produced by Northrop Grumman Innovation Systems. (GEM 63XL, a stretched version of the GEM 63 booster will be used on the upcoming Vulcan rocket.) The first Atlas V launched with GEM 63 boosters on November 13, 2020.

Design
AJ-60A is a solid fueled rocket burning HTPB. The casing is composed of a graphite epoxy composite, and the engine throat and nozzle are made of carbon-phenolic composite. As configured for use on Atlas V, the nozzle is fixed at a 3 degree cant away from the attachment point, but Aerojet offers a variant with thrust vectoring capability. The Atlas V configuration also features an inward slanting nosecone, but it is available with a conventional nosecone or none at all for use on other rockets. The stages are designed to be transported by truck.