All Expendable Launch Vehicles use the same basic technology to get into space – two or more rocket-powered stages, which fall away when their engine burns are completed. Whatever a launch vehicle carries above the final discarded stage is considered the payload.
A payload’s weight, orbital destination and purpose determine what size launch vehicle is required. A small ELV like Pegasus can place a low-weight spacecraft into near-Earth orbit, while an expendable vehicle like the massive Saturn V was required to send manned Apollo spacecraft to the Moon.
The powerful Titan/Centaur combination carried large and complex robotic scientific explorers, such as the Vikings and Voyagers, to examine other planets in the 1970s. Among other missions, the Atlas/Agena vehicle sent several spacecraft to photograph and then impact the Moon. Atlas/Centaur vehicles launched many of the larger spacecraft into Earth orbit and beyond.
To date, Delta launch vehicles have carried more than 200 NASA scientific, wind and communications payloads into orbit, or to other planets. NASA used the Athena I and II vehicles to launch scientific satellites from VAFB, CCAFS and Kodiak Island. The Pegasus, an Orbital Sciences fleet vehicle, is the only airborne launch vehicle in the ELV fleet. The Taurus vehicle, also built by Orbital Sciences, may be used for future NASA launches.