 EELV Secondary Payload Adapter

The EELV Secondary Payload AdapterESPA, also called an ESPA ringis a payload adapter ring for launching secondary payloads on orbital launch vehicles.Originally developed for US launch vehicles in the 2000s to launch secondary payloads on US DoD space missions that used the Atlas V and Delta IV Evolved Expendable Launch Vehicles (EELV), the adapter design has become a "de facto" standard and is now also used for spaceflight missions on non-governmental private spacecraft missions as well.