The Star 27 is a solid rocket motor for the upper stages of rockets. It burns HTPB fuel with an average erosion rate of 0.0011 inches per second. When used on the Pegasus air-launch rocket payloads are capable of leaving Earth orbit. A Star 27 was used in the launch of the IBEX spacecraft. The spacecraft had a mass of 105 kg by itself and together with its Star 27 motor, 462 kg. The Star 27 helped it get to a higher orbit, beyond Earth's magnetosphere.