MIL-HDBK-143A
Doppler effect - The phenomenon evidenced by the change in the observed frequency of a
sound or radio wave caused by a time rate of change in the effective length of the path of
travel between the source and the point of observation.
doran - A Doppler ranging system which uses phase comparison to establish missile range.
double-base Propellant - A solid rocket Propellant which uses two unstable compounds, such
as nitrocellulose and nitroglycerin. A separate oxidizer is not needed to sustain combustion.
double-integrating gyro - A single-degree-of-freedom gyro (which see) with essentially no
restraint of its spin about the output axis. The output signal is produced by gimbal (which see)
angular displacement, relative to the base.
dovap - Doppler velocity and position; a range instrumentation and safety system used to
determine velocity and position of a missile with electromagnetic radiation.
down the Slat - Vernacular expression for a successful flight of a missile down the test range
and within the left and right range limits (parallel lines previously plotted on the range-
plotting board) established by range safety personnel.
downwash - Aerodynamic interference from the wings of an aircraft or missile which can
strike the aft tail surfaces in such a way as to cause positive trim angles of attack even in cases
where the wings are located at the vehicle's center-of-gravity.
drift -In guidance, the gradual lateral deviation of a missile away from the desired trajectory,
due to misalignments, electrical biases, or cross winds.
drift rate- The amount of lateral deviation of a missile away from a desired trajectory, per
second or any other unit of time.
drogue - A device, usually funnel-or cone-shaped, which is dragged or towed behind a
moving body to regulate velocity or provide gross stabilization control.
drogue parachute - 1. A type of parachute attached to a missile to slow it down (also called
deceleration parachute or drag parachute). 2. A small parachute specifically used to pull a
larger parachute out of stowage.
drogue recovery - A recovery system for stabilizing and decelerating payloads, warheads, or
booster sections from missiles in the atmosphere, so that larger recovery parachutes can be
deployed at lower altitudes within specified opening shock constraints.
drone - A remotely controlled vehicle often used as a target for Guided Missile tests or
training exercises Also applies to special missiles used as target vehicles.
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