Harry Julian Allen (April 1, 1910 – January 29, 1977), also known as Harvey Allen, was an

aeronautical engineer Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: aeronautical engineering and astronautical engineering. Avionics engineering is sim ...

and a Director of the

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...

Ames Research Center The Ames Research Center (ARC), also known as NASA Ames, is a major NASA research center at Moffett Federal Airfield in California's Silicon Valley. It was founded in 1939 as the second National Advisory Committee for Aeronautics (NACA) labo ...

, most noted for his "Blunt Body Theory" of

atmospheric entry Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. There are two main types of atmospheric entry: ''uncontrolled entry'', such as the en ...

which permitted successful recovery of orbiting spacecraft. His technique is still used to this day.

Career

Allen was born in

Maywood, Illinois Maywood is a village in Proviso Township, Cook County, Illinois, United States in the Chicago metropolitan area. It was founded on April 6, 1869, and organized October 22, 1881. The population was 23,512 at the 2020 United States Census. Histor ...

on April 1, 1910. He attended

Stanford University Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is conside ...

, receiving a Bachelor of Arts in engineering in 1932 and an Aeronautical Engineer professional degree in 1935. In 1936, he joined the

NACA The National Advisory Committee for Aeronautics (NACA) was a United States federal agency founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its assets ...

Langley Memorial Aeronautical Laboratory Langley may refer to: People * Langley (surname), a common English surname, including a list of notable people with the name * Dawn Langley Simmons (1922–2000), English author and biographer * Elizabeth Langley (born 1933), Canadian perform ...

. In 1940, he moved to the Ames Research Laboratory, where he served as Chief of the Ames Theoretical Aerodynamics Branch (starting in 1941), Chief of the High-Speed Research Division (starting in 1945), assistant director for Astronautics (starting in 1959), and finally Center Director (1965-1969).

Research

Allen was interested in the full range of aerodynamics research, and made contributions to the study of subsonic,

transonic Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach number, but transoni ...

supersonic Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...

and

hypersonic In aerodynamics, a hypersonic speed is one that exceeds 5 times the speed of sound, often stated as starting at speeds of Mach 5 and above. The precise Mach number at which a craft can be said to be flying at hypersonic speed varies, since ind ...

flow. When the United States became interested in the design of ballistic missiles, Allen began research in the dynamics and thermodynamics of

atmospheric reentry Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. There are two main types of atmospheric entry: ''uncontrolled entry'', such as the ...

, as well as the effects of

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...

and

meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the original object ...

s on

space vehicle A space vehicle is the combination of a spacecraft and its launch vehicle which carries it into space. The earliest space vehicles were expendable launch systems, using a single or multistage rocket to carry a relatively small spacecraft in pr ...

s. His most significant contribution in this area was the idea of using a blunt nose for reentry vehicles, otherwise known as his "Blunt Body Theory". Earlier ballistic missiles, developed by both the United States and the

Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nationa ...

, featured long nose cones with very narrow tips, which had relatively low drag when entering the atmosphere at high speeds. However, Allen demonstrated that a blunt body, although it had greater drag, would have a detached

shock wave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...

which would transfer far less heat to the vehicle than the traditional shape with its attached shock wave. Excessive heating was the greatest concern in the design of ballistic missiles and spacecraft, since it could melt their surface; the blunt body design solved this problem. Allen's theory led to the design of ablative

heat shield In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...

s that protected the astronauts of the Mercury, Gemini and

Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label= ...

programs as their space capsules re-entered the atmosphere.

Awards and honors

*Fellow of the

American Institute of Aeronautics and Astronautics The American Institute of Aeronautics and Astronautics (AIAA) is a professional society for the field of aerospace engineering. The AIAA is the U.S. representative on the International Astronautical Federation and the International Council of ...

*Fellow of the

Royal Aeronautical Society The Royal Aeronautical Society, also known as the RAeS, is a British multi-disciplinary professional institution dedicated to the global aerospace community. Founded in 1866, it is the oldest aeronautical society in the world. Members, Fellows, ...

of Great Britain *Fellow of the

American Astronautical Society Formed in 1954, the American Astronautical Society (AAS) is an independent scientific and technical group in the United States dedicated to the advancement of space science and space exploration. AAS supports NASA The National Aerona ...

*Fellow of the Meteoritical Society *Member of the

National Academy of Engineering The National Academy of Engineering (NAE) is an American nonprofit, non-governmental organization. The National Academy of Engineering is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of ...

*Sylvanus Albert Reed Award of the Institute of the Aerospace Sciences (predecessor of the AlAA) (1955) *Wright Brothers Lectureship of the Institute of the Aerospace Sciences (1957) *Distinguished Service Medal of the NACA (1957) *Airpower Trophy of the

Air Force Association The Air & Space Forces Association (AFA) is an independent, 501(c)(3) non-profit, professional military association for the United States Air Force and United States Space Force. Headquartered in Arlington, Virginia, its declared mission is ...

(1958) *Golden Plate Award of the

American Academy of Achievement The American Academy of Achievement, colloquially known as the Academy of Achievement, is a non-profit educational organization that recognizes some of the highest achieving individuals in diverse fields and gives them the opportunity to meet ...

(1962) *NASA Medal for Exceptional Scientific Achievement (1965) *

Daniel Guggenheim Medal The Daniel Guggenheim Medal is an American engineering award, established by Daniel and Harry Guggenheim. The medal is considered to be one of the greatest honors that can be presented for a lifetime of work in aeronautics. Recipients have included ...

awarded by AlAA, ASME, and SAE (1969)

References

External links

Air & Space Smithsonian Article
{{DEFAULTSORT:Allen, Harry Julian American aerospace engineers NASA people Stanford University School of Engineering alumni 1910 births 1977 deaths Fellows of the Royal Aeronautical Society People from Maywood, Illinois Engineers from Illinois 20th-century American engineers