SA-1 - Space Access LLC

The SA-1 has been proposed to conduct satellite launches by Space Access LLC. The concept consists of an unpiloted spaceplane that uses a hybrid propulsion system and one or two rocket-powered upper stages to deliver a full range of payloads to LEO or GTO.

The spaceplane vehicle, or "aerospacecraft," is approximately the size of a Boeing 747 aircraft. Its propulsion system is based on a ramjet engine design that was developed in the 1960s by the USAF. Space Access has developed a proprietary modification to the engines that will allow the ramjet to operate at both subsonic and supersonic speeds (ramjets normally only operate above Mach 2). One of the company's subcontractors, Kaiser Marquardt, has reportedly tested elements of the propulsion system, and Space Access has worked with the Air Force Research Laboratory (AFRL) since September 1995 to study the "ejector" ramjet propulsion system and the design of the aerospacecraft. As of March 1998, Space Access had wind-tunnel tested the ejector ramjet engine at all of the altitude and speed points of the SA-1's planned flight profile.

The SA-1 vehicle will take off horizontally, using a mixture of air and liquid hydrogen to power its ejector ramjet engines. The aerospacecraft then climbs to 45 km, at a speed of Mach 8. When it reaches the limits of the atmosphere and its ramjets loose power, the SA-1 switches power sources and uses a liquid rocket to reach its final altitude of 90 km at Mach 9. The vehicle then releases an upper stage carrying the payload from its nose area. For LEO missions, the SA-1 carries a single upper stage that features a lifting-body design and autonomously de-orbits and lands horizontally. For missions to GTO, the SA-1 carries two such upper stages.

The SA-1 vehicle will be able to launch payloads up to 5,200 kg to GTO. Space Access intends to pursue GEO launches as its primary market, but the SA-1 will have significant LEO capability as well. Space Access also plans to introduce capability that would allow it to undertake resupply missions to the International Space Station.

In 1999, after working with NASA on the Space Transportation Architecture Study, Space Access decided to study development of a crewed version of the second stage, which would give the SA-1 the capability to provide human access to space. Space Access hopes that the SA-1 could become an alternative or replacement to the Space Shuttle.

Space Access plans to test a one-third-scale demonstrator vehicle with the ejector ramjet and other key systems. Development plans as of January 2000 called for testing of a full-size vehicle in 2001 with launch operations commencing in 2005.