a reply to: butcherguy
The X-20 Dyna-Soar was a winged space plane concept that is really not part of the Dream Chaser lineage.
Interest in lifting bodies dates back more than 60 years. Research by the National Advisory Committee for Aeronautics (NACA, the predecessor to NASA)
involved studies regarding reentry survivability of ballistic-missile nose cones, the results of which were reported in 1953. NACA engineers Alfred
Eggers and H. Julian Allen further developed the concept of lifting reentry from suborbital and orbital spaceflight, presenting their work at the
Conference on High-Speed Aerodynamics in March 1958. NACA researcher Maxine Faget concluded that the lifting body concept could be used for a manned
space vehicle. This became the basis for a series of studies and flight research projects a reusable space shuttle.
Ultimately, a delta-winged orbiter configuration was selected for use with the Space Transportation System (STS), but several lifting body designs
were flown between 1963 and 1975.These included the unmanned ASSET and PRIME test articles that were launched atop rockets and a series of manned
craft. The low-speed M2-F1 was made of wood and fabric. Unpowered, it was towed aloft behind a Pontiac sedan driving about 120 miles per hour across
the dry lakebed at Edwards Air Force Base, California. It was later towed behind a C-47 for higher-altitude glide flights. Its blunt half-cone shape
earned the M2-F1 the nickname "flying bathtub."
This was followed in 1966 by the heavyweight, rocket-powered M2-F1 that was dropped from beneath the wing of a modified B-52 bomber. Following a crash
in 1967, the vehicle was repaired and improved, and continued to fly as the M2-F3 until 1972. More-streamlined aerodynamic shapes were explored using
the HL-10 and X-24A (a manned vehicle derived from the PRIME), and the X-24B. For a while, the HL-10 was a leading contender for the STS program but a
more conventional space plane design was selected instead, eventually become what we know today as the Space Shuttle.
Possibly inspired by the U.S. lifting body efforts, the Soviets developed preliminary designs for a spaceplane concept called Spiral in 1966. Although
the craft bore a superficial resemblance to the X-24A and HL-10, it was clearly a unique configuration. Several subscale, unmanned models (BOR-1,
BOR-2, and BOR-3) were launched on suborbital trajectories between 1969 and 1974. BOR-1 was essentially a wooden mock-up. BOR-2 (a 1:3 scale model)
and BOR-3 (a 1:2 scale model) were equipped with ablative heat shields. A manned demonstrator called the MiG 105.11 was test flown in 1977 and 1978.
It was dropped from the belly of a modified Tu-95K bomber. The reusable unmanned,1:2-scale BOR-4 flew several orbital spaceflights between 1982 and
1984 to test thermal protection systems. The Soviets ultimately abandoned the Spiral project in favor of the delay-winged Buran space shuttle.
During early BOR-4 missions, the vehicle was recovered by the Soviets following splashdown in the Indian Ocean. On two occasions in 1982 and 1983 the
Royal Australian Air Force managed to obtain detailed photos of the craft. American engineers at NASA Langley Research Center used these photos to
create wind-tunnel models of the BOR-4. During nearly a decade of studies they analyzed the design and refined the shape with the idea of applying it
to a 10-ton spacecraft dubbed the HL-20. It was to be a crew transportation system for a proposed manned space station. By the late 1990s, a larger
version called the HL-42 was proposed.
Orbital Sciences Corporation picked up the idea of a BOR-4/HL-20 derivative for use as a "space taxi" under NASA's Space Launch Initiative but the
project was cancelled in 2003. In 2006, after NASA announced the Commercial Orbital Transportation Services program, a company called SpaceDev
proposed a six-passenger HL-20-type craft called Dream Chaser. In 2008, SpaceDev was acquired by Sierra Nevada Corporation (SNC). In 2010, SNC was
awarded a contract to develop Dream Chaser for the Commercial Crew Development program. The first unmanned glide flight of the Dream Chaser took place
in October 2013. A spectacular approach and touchdown was marred by an equally spectacular crash landing when one of the main gear failed to extend
and the Dream Chaser skidded off the runway and rolled in the desert. The vehicle was eventually repaired and the second flight, on 11 November 2017,
was completely successful. And so, the legacy of U.S. and Russian lifting body designs continues to advance.