The Complete Book of Spaceflight: From Apollo 1 to Zero Gravity

Hugh Dryden Dryden (left) arrives with John Victory (center),
NACA’s executive secretary, for a tour of the Langley Memorial
Aeronautical Laboratory. Welcoming them is engineer-incharge
Henry Reid. NASA
from Johns Hopkins University at age 17. Three years
later, in 1918, he was awarded a Ph.D. in physics and
mathematics from the same institution even though he
had been employed full-time in the National Bureau of
Standards since June 1918. His career at the Bureau,
which lasted until 1947, was devoted to studying airflow,
turbulence, and particularly the problems of boundary
layers of air next to moving objects. The work that he carried
out in the 1920s measuring turbulence in wind tunnels
facilitated research by NACA (National Advisory
Committee for Aeronautics) that led to the laminar flow
wings used in the P-51 Mustang and other World War II
aircraft. From the mid-1920s to 1947, Dryden’s publications
became essential reading for aerodynamicists
around the world. During World War II, his work on a
glide bomb named the Bat won him a Presidential Certificate
of Merit. He capped his career at the Bureau by
becoming assistant director and then associate director
during his final two years there. He then served as director
of NACA (1947–1958), and later became deputy
administrator of NASA under T. Keith Glennan and
James Webb. 276
DSCS (Defense Satellite Communications System)
The U.S. Department of Defense global network of
strategic communications satellites, referred to as “Discus.”
DSCS provides uninterrupted secure voice and
high data rate communications between major military
terminals and national command authorities. It was
developed in three phases. The first was originally known
as IDCSP (Initial Defense Communications Satellite
Dunn, Louis G. 111
Program) but renamed DSCS 1 upon becoming operational.
The second phase involved much larger spacecraft
placed in true geosynchronous orbits between 1971 and
1975. Seven of these were still working in 1982 when the
first DSCS 3 satellites were launched. A constellation of
six DSCS 3 satellites (four operational and two spares) in
geosynchronous orbit is now up and running.
DSPS (Defense Support Program Satellite)
See IMEWS.
dual spin
A spacecraft design in which the main body of the satellite
is spun to provide altitude stabilization, and the
antenna assembly is “de-spun”—in other words, rotated at
the same speed but in the opposite direction—by means
of a motor and bearing system in order to continually
point the antenna earthward. See spin stabilization.
dual thrust
Thrust that derives from two propellant grains using the
same propulsion section of a missile or space vehicle.
duct
In an air-breathing engine, a channel along which a
working fluid is forced to travel in order to increase its
momentum and thereby produce thrust.
duct propulsion
See air-breathing engine and propulsion.
Duke, Charles Moss, Jr. (1935–)
An American astronaut who served as backup Lunar
Module (LM) pilot for Apollo 13 and Apollo 17, and LM
pilot for Apollo 16. Duke received a B.S. in naval sciences
from the U.S. Naval Academy in 1957 and an M.S.
in aeronautics from the Massachusetts Institute of Technology
in 1964. Following his graduation and commission
from the Naval Academy, he entered the Air Force
and served three years in Germany before transferring to
the Aerospace Research Pilot School. He was among 19
new astronauts selected in April 1969. Duke retired from
NASA in 1975 to enter private business.
Dunn, Louis G. (1908–1979)
A South African–born engineer who played a key role in
the development of early American missiles and launch
vehicles. Dunn earned a B.S. (1936), two M.S.s—in
mechanical engineering (1937) and aeronautical engineering
(1938)—and a Ph.D. (1940) from the California
Institute of Technology, and then joined the faculty
there. He became assistant director of JPL (Jet Propulsion
Laboratory) in 1945 and then served as its director