Prometheus was a proposed crewed vertical-takeoff, horizontal-landing (VTHL) lifting body spaceplane concept put forward by Orbital Sciences Corporation in late 2010 as part of the second phase of NASA's Commercial Crew Development (CCDev) program.[full citation needed]
The Prometheus design was based on an earlier NASA design, the HL-20 Personnel Launch System. Prometheus also included other NASA-funded design improvements to HL-20 by Orbital Sciences that were done some years ago as part of NASA's Orbital Space Plane program. Whereas the HL-20 was a pure lifting body, the Prometheus design was for a Blended Lifting Body (BLB). This design combines volumetric efficiency with superior aerodynamic qualities. Prometheus could have initially carried four astronauts to the International Space Station or future commercial space stations but further development could have increased the seating capacity to six. The baselined launch vehicle was the Atlas V, but the design could have accommodated other launch vehicles. The cost of the development of the Prometheus spacecraft and of upgrading the Atlas V would be between $3.5 and $4 billion.
The Vertical Takeoff, Horizontal Landing (VTHL) vehicle would be launched on a human-rated Atlas V rocket but would land on a runway. The initial design would carry a crew of four, but it could carry up to six people or a combination of crew and cargo. In addition to Orbital Sciences, the consortium included Northrop Grumman that would have built the spaceplane and the United Launch Alliance that would have provided the launch vehicle. Virgin Galactic also confirmed it would be teaming with Orbital on the Orbital CCDev 2 project. After failing to be selected for a CCDev phase 2 award by NASA, Orbital announced in April 2011 it would likely wind down its efforts to develop a commercial crew vehicle.
issues of volumetric efficiency, high L/D for cross range, low wing loading for reduced landing speed, and passive stability for all abort conditions were addressed. ... As the optimization process continued, the HL-20 initial reference shape eventually evolved into the Blended Lifting Body (BLB). The BLB combines volumetric efficiency with superior aerodynamic qualities and was designed to launch vertically and land horizontally.
CEO Dave Thompson said ... "I don't, at this time, anticipate that we'll continue to pursue our own project in that race. We'll watch it and if an opportunity develops we may reconsider. But at this point, I would not anticipate a lot of activity on our part in the commercial crew market."