Spacecraft with a lenticular design (that is, shaped like a biconvex lens) were actively studied by NASA and US industry in the late 1950s and early ‘60s. A craft of such a shape would experience lower heating on re-entry than a winged layout as the heat would be spread over a greater area.A circular design might experience less aerodynamic drag and be more manoeuvrable at subsonic speeds than a winged design.However there were drawbacks; such a craft would be aerodynamically unstable and hard to control.As far as I know no lenticular space vehicle has yet flown (although there are many who say such things are being regularly observed in our skies).
This concept was created and championed by Alan Kehlet, an aerodynamicist at NASA’s Langley research centre.Many of the giants of US aerospace studied design concept derived from Kehlet’s work in the early 1960s.
Painted by artist Gordon Phillips the fascinating piece of early 1960s concept art entitled “Dyna-Soar Hypersonic Glider”, shows the racy-looking Dyna-Soar (left) craft.Also known as the X-20, this was a planned military spaceplane for the US Air Force, which never actually flew although a prototype was being constructed when the project was cancelled in December 1963. The other craft in the right of the image is more interesting still, being Kehlet’s final lenticular concept for NASA. To be honest, it looks as though it belongs in the shuttle bay of one of the starships Enterprise! The artwork shows the vehicle’s folding aerodynamic control flaps and the retractable periscope the pilot (one of three crew members) would have used to land the vehicle on a runway or water.
The proposed lentiular design concept for the Apollo spacecraft was one of several unorthodox designs rejected in favour of the more familiar conical shape which was lighter and less complex.The lenticular design was a “road not taken”, losing out to less challenging configurations.It is strange to think that if history had proceeded differently, each Apollo crew could have ended their lunar mission by gliding to a touchdown on a runway at Edwards AFB in a flying saucer!
(Article by Colin Johnston, Science Communicator)