Shadowgraph Images of Re-entry Vehicles
Summary
These four shadowgraph images represent early re-entry vehicle concepts. A shadowgraph is a process that makes visible the disturbances that occur in a fluid flow at high velocity, in which light passing through a flowing fluid is refracted by the density gradients in the fluid resulting in bright and dark areas on a screen placed behind the fluid.H. Julian Allen pioneered and developed the Blunt Body Theory which made possible the heat shield designs that were embodied in the Mercury, Gemini and Apollo space capsules, enabling astronauts to survive the firey re-entry into Earth's atmosphere. A blunt body produces a shockwave in front of the vehicle--visible in the photo--that actually shields the vehicle from excessive heating. As a result, blunt body vehicles can stay cooler than pointy, low drag vehicles.
The Space Race began with a shock to the American public when the Soviet satellite Sputnik was launched in 1957. United states created NASA accelerate U.S. space exploration efforts and launched the Explorer 1 satellite in 1958. The Soviet Union was first again when it puts the first human, cosmonaut Yuri Gagarin, into a single orbit on April 12, 1961. Shortly after this, on May 5, the U.S. launched Alan Shepard, on a suborbital flight and reached its orbital goal on February 20, 1962, when John Glenn made three orbits around the Earth in the Mercury capsule. The Mercury space capsule was a pressurized cabin produced by McDonnell Aircraft and carried supplies of water, food, and oxygen for about one day. Mercury was launched on a top of modified Atlas D ballistic missiles. The capsule was fitted with a launch escape rocket to carry it safely away from the launch vehicle in case of a failure. Small retrorockets were used to bring the spacecraft out of its orbit, after which an ablative heat shield protected it from the heat of atmospheric reentry. Finally, a parachute slowed the craft for a water landing. Both astronaut and capsule were recovered by helicopters deployed from a U.S. Navy ship. The Mercury project missions were followed by millions on radio and TV around the world. Its success laid the groundwork for Project Gemini, which carried two astronauts in each capsule and perfected space docking maneuvers essential for manned lunar landings in the Apollo program announced just a few weeks after the first manned Mercury launch.
Project Gemini was NASA's second human spaceflight program that started in 1961 and concluded in 1966, between projects Mercury and Apollo. The Gemini spacecraft carried a two-astronaut crew. Ten crews flew low Earth orbit (LEO) missions between 1965 and 1966.
NASA Photo Collection
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