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

110 downlink
Douglas Skyrocket The Skyrocket begins its flight after dropping
from its B-29 mothership. NASA
speed of sound (Mach 2). On November 30, 1953, pilot
A. Scott Crossfield nudged the Skyrocket—which had
been air-launched from a Boeing B-29—into a shallow dive
at 18,900 m and reached 2,136 km/hr (Mach 2.01). The D-
558 series, which also included the Skystreak, was developed
by Douglas Aircraft under the direction of Edward
H. Heinmann of the U.S. Navy. NACA (National Advisory
Committee for Aeronautics) used the Skyrocket to
explore the flight characteristics of swept-wing aircraft.
The Skyrocket set a number of speed and altitude records
before the program ended in 1956.
downlink
The radio signal received from a spacecraft, as distinct
from the uplink, which is the signal sent to the spacecraft
from the ground.
downrange
The area on Earth over which a spacecraft travels after
launch and before entering orbit.
drag
Resistance to motion through a fluid. As applied to a
spacecraft passing through an atmosphere, it is the component
of the resultant force due to relative airflow measured
parallel to the direction of motion.
Draper, Charles Stark (1901–1987)
An American engineer and physicist, regarded as the
father of inertial navigation. An Institute professor at the
Massachusetts Institute of Technology, Draper developed
the guidance systems used by aircraft, submarines, and
guided missiles that made the Apollo missions possible,
and that help steer the Space Shuttle.
drogue
A small parachute used to slow and stabilize a descending
spacecraft, usually before the opening of a main landing
parachute.
DRTS (Data Relay Test Satellite)
Two Japanese satellites—DRTS-W (West) and DRTS-E
(East)—that will carry out experiments in intersatellite
communications. Traditionally, keeping in permanent
contact with low-Earth-orbiting satellites has involved
the use of a number of expensive ground stations. The
idea of the DRTS project is to allow constant communication
between mission control and an orbiting spacecraft
by using the DRTS satellites as relay stations.
Launch of the first satellite, DRTS-W, by NASDA
(National Space Development Agency) was scheduled for
September 2002.
dry weight
The weight of a launch vehicle or spacecraft without propellants
and pressurizing gases.
Dryden Flight Research Center (DFRC)
NASA’s foremost installation for atmospheric flight
operations and flight research. Located at Edwards Air
Force Base, Dryden uses a variety of specialized research
aircraft and demonstrators to study high-speed and highaltitude
environments. Among the aims of this work are
to find ways of cutting long-distance flight travel times
and to develop new aircraft configurations and structures
to increase agility. DFRC’s origins go back to 1946, when
a small team of NACA (National Advisory Committee
for Aeronautics) engineers came to Muroc Army Airfield
(now Edwards Air Force Base) to prepare for X-1 tests in
a joint NACA–Air Force program. The following year
NACA’s Muroc Flight Test Unit was formed, which in
1949 became the NACA High-Speed Flight Research Station
with Walt Williams as its chief. The center was eventually
named after Hugh Dryden. Over the years, all of
NASA’s high-performance aircraft and flight research
vehicles have flown from here, including all of the Xplanes,
the Lunar Landing Research Vehicle or “Flying
Bedstead,” and the Space Shuttle prototype Enterprise.
Most recently, Dryden has been involved in test flights of
the X-38 lifeboat for the International Space Station and
various solar-powered aircraft.
Dryden, Hugh Latimer (1898–1965)
An aerodynamicist and career civil servant who played a
prominent role in American aerospace developments
after World War II. Dryden graduated from high school
at the remarkably young age of 14 and earned an A.B.