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NASA Ames Research Center Helped Bring Project Mercury Home
2.16.12
 
Legendary Ames engineer H. Julian Click image for full resolution.
Legendary Ames engineer H. Julian "Harvey" Allen shown at his blackboard conducting basic research for the design of the Mercury capsule.
Image credit: NASA

Alfred J. Eggers, Jr., stands beside the Atmospheric Entry Simulator he invented in 1958 as a laboratory means of studying the problems of aerodynamic heating and thermal stresses during re-entry. Click image for full resolution.
Alfred J. Eggers, Jr., stands beside the Atmosphere Entry Simulator he invented in 1958 as a laboratory means of studying the problems of aerodynamic heating and thermal stresses during re-entry. The tubular tank in the foreground held air under high pressure. When a valve was opened, the air flowed through the test section (the dark area under the high-voltage signs) into the chimney-like vacuum tank. As the airstream moved, a high-velocity gun fired a test model through the chamber in a left-to-right direction.
Image credit: NASA

An ablation test conducted on a Mercury capsule Click image for full resolution.
An ablation test conducted on a Mercury capsule.
Image credit: NASA
The Atmosphere Entry Simulator shown in 1958 (much larger than the pilot facility) Click image for full resolution.
A larger version of the Atmosphere Entry Simulator at NASA Ames invented by Alfred J. Eggers, Jr.
Image credit: NASA

As the nation celebrates the 50th anniversary of American orbital flight this month on Feb. 20, 2012, it's important to remember that NASA Ames Research Center played a key role in NASA's first major human spaceflight mission.

Only a week after NASA was founded, the agency announced on Oct. 7, 1958 the formation of a national manned space-flight project, later named Project Mercury, whose roots were sown by NASA's predecessor, the National Advisory Committee for Aeronautics (NACA).

In May 1952, the NACA Main Committee had passed a resolution, at the urging of the U.S. Air Force, that the NACA Laboratories begin studying how to solve various problems associated with human spaceflight. Particularly vexing to aerospace engineers were problems encountered by the spacecraft during its high-speed re-entry into Earth's atmosphere. During its fiery descent, the spacecraft would experience extremely high temperatures. Something needed to be done to prevent those spacecraft from burning up before they reached Earth.

Led by legendary engineer H. Julian "Harvey" Allen beginning in the early 1950s, the Ames laboratory solved many of the major problems of re-entry. Under Allen's inspired leadership, Ames conducted most of the basic research behind the design of the Mercury capsule.

Most importantly, Allen's work on blunt body hypersonics laid the foundation for the Mercury capsule's distinctive appearance with a curved, blunt shape to facilitate its re-entry into Earth's atmosphere. After he developed this theory, Allen worked with his colleagues in the High Speed Research Division at Ames to develop a variety of test facilities, including arc jets, ballistic ranges and hypersonic wind tunnels. Using these facilities, they tested the capsule's unusual configuration and validated the use of blunt bodies on re-entry vehicles. Allen's unique blunt body concept has been a staple of spacecraft design ever since.

Another Ames pioneer in the Mercury Project was Alfred J. Eggers, chief of Ames' 10-foot-by-14-foot Supersonic Wind Tunnel Branch. Eggers was Ames' leading theoretician on capsule design and a key member of the NASA Research Steering Committee on Manned Space Flight, chaired by Harry Goett, chief of the Full Scale and Flight Research Division at Ames. The committee's focus was the creation of a basic research program to seek solutions and ensure the success of the Mercury program. In recognition of his valued contributions to Project Mercury, Goett was named the founding director of a new NASA field center, the Goddard Space Flight Center in Maryland in 1959.

To support Project Mercury, Eggers worked closely with Allen and another Ames pioneer in hypersonic spacecraft, Clarence "Sy" Syvertson, who later became the director of Ames, to develop a unique set of research simulators to test heating problems encountered by spacecraft during re-entry into the Earth's atmosphere. They devised free-flight ballistic ranges to create re-entry speeds and validate damping characteristics to ensure the capsules would be aerodynamically stable. Alfred Seiff and Thomas Canning of the Ames Vehicle Environment Division calculated the radius and shape of the capsule's heat shield and verified their work in the ballistic ranges.

Ames also tested a small model of a re-entry vehicle in its new Atmosphere Entry Simulator, designed by Eggers. The simulator was equipped with a trumpet-shaped nozzle that accelerated a flow of high-pressure air duplicating the way Earth's atmosphere becomes thicker at lower altitudes. A precisely machined one-quarter-inch diameter plastic model matched the blunt body shape of the Mercury capsule. Using helium as a propellant, the model was launched at 17,000 miles per hour to test how much material would ablate. The test showed that less than five percent of the plastic was vaporized during the model's flight, thereby demonstrating that an ablative heat shield would work on the Mercury capsule.

Ames then conducted tests of larger models of the Mercury capsule in its 9-foot-by-7-foot, 8-foot-by-7-foot, 10-inch-by-14-inch Supersonic Wind Tunnels, the 14-foot Transonic Wind Tunnel, the Supersonic Free Flight Wind Tunnel and the Pilot Gun Tunnel. They studied flutter in the metal panels at the narrow end of the capsule, pressures and heat transfer, static and dynamic stability and aerodynamic lift and drag.

Ames also performed key tests on the launch abort system. If there were problems with the Atlas rocket, then the capsule with the astronaut would separate and lift off safely. The aerodynamics of this were complex and NASA needed to be sure the capsule would land right side up. Hours of tests were conducted in Ames' Unitary Wind Tunnels, including the one-foot-by-three-foot Supersonic Wind Tunnel, the Supersonic Free-Flight wind tunnel and the 2-inch-by 2-inch shock tunnel.

Ames continued conducting wind tunnel tests of capsule designs until NASA selected a prime contractor, McDonnell Aircraft Co., to build the Mercury capsule in 1959. The work then shifted from NASA Ames to full-scale flight tests of capsules built at NASA's Langley and Lewis (now Glenn) research centers. Their efforts, coupled with the fundamental research conducted at Ames, culminated in the successful launch on Feb. 20, 1962 of the Mercury program's Friendship 7 from Cape Canaveral with astronaut John Glenn, Jr., aboard, ensuring his place in history as the first American in orbit.

So as we celebrate 50 years of American orbital space flight, let's not forget the lasting legacy made by a group of hard-working, dedicated visionaries at NASA Ames who paved the way for future space exploration. Thanks to their tireless efforts, and those of countless other scientists and engineers throughout the agency, NASA's human space flight program has soared through history leaving numerous significant accomplishments in its wake. And hold on – there's plenty more to come.

 
 
Michael Mewhinney
Ames Research Center, Moffett Field, Calif.