Secondary payload
[2][3] As a result, the secondary payload typically obtains a substantially reduced price for transportation services to orbit, by accepting a trade off of the loss of control once the contract is signed and the payload is delivered to the launch vehicle supplier for integration to the launch vehicle.
While originally a US government-centric option for government-owned launches—where secondary payload slots were often given away by whatever allocation means a government agency might choose—an entire market has emerged over time to take advantage of the lower cost of access to space through secondary payload opportunities.
US commercial launcher United Launch Alliance (ULA) offers virtually no access for secondary payloads commercially, although the US military offers some secondary payload slots on ULA launchers Atlas V and Delta IV, that are then controlled by government launch slot allocation processes.
[5] The Photon is a satellite bus designed by Rocket Lab that is a major enhancement to the Kick Stage.
Flights were planned to be launched from SLC-4E at Vandenberg Air Force Base, starting from November 2020 on the Falcon 9 rocket.
[9][10] However, following the response to the early August announcement; later in the month SpaceX revised plans, reducing prices such that payloads of up to 200 kg (440 lb) for US$1 million.
[11] The maiden flight of this program took place on June 13, 2020, when Starlink 8 was flown with 3 SkySats manufactured by Planet Labs.
[21] The EELV Secondary Payload Adapter (ESPA) is an interstage adapter ring that was originally designed for launching secondary payloads on space missions of the United States Department of Defense that use the Atlas V and Delta IV.
[2] The ESPA ring design has become a de facto standard, and is now much more widely used than the original intent and rockets.
[3] By 2011, SpaceX was contracting for secondary payloads to be launched on their Falcon 9 rocket using a standard ESPA ring interface.
It includes five 61 cm (24 in)-diameter ports, each capable of carrying payloads weighing up 300 kilograms (660 lb).
