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

designed into the system so that the unburned fuel acts as
a chamber coolant. Generally, incomplete combustion
denotes a system not functioning efficiently.
combustion chamber
The chamber of a liquid-propellant rocket engine in
which the fuel and the oxidizer burn to produce high
pressure gas expelled from the engine nozzle to provide
thrust. To begin with, the fuel and oxidizer pass separately
through a complex manifold in which each component
is broken down into smaller and smaller flow
streams, in the same way that arteries in the body divide
into increasingly smaller capillaries. Then the propellants
are injected into the combustion chamber via the injector—a
plate at the top of the chamber that takes the small
flow streams and forces them through an atomizer. The
purpose of the injector is to mix the fuel and oxidizer
molecules as thoroughly and evenly as possible. Once
mixed, the fuel and oxidizer are ignited by the intense
heat inside the chamber. To start the combustion, an ignition
source (such as an electric spark) may be needed.
Alternatively, some propellants are hypergolic—they
spontaneously combust on contact—and do not need an
ignition source.
combustion efficiency
The ratio of the energy actually released by the fuel during
combustion to the energy contained in the fuel. A
perfect combustion would release all the energy a fuel
contains, in which case combustion efficiency would be
1, or 100%.
combustion instability
Unfavorable, unsteady, or abnormal combustion of fuel
in a rocket engine.
combustion limit
In a solid-propellant rocket motor, the lowest pressure at
which a given nozzle will support the burning of fuel
without chuffing.
combustion oscillation
High-frequency pressure variations in a combustion
chamber caused by uneven propellant consumption.
comet and asteroid missions
See, in launch order: ICE (August 1978), Vega (December
1984), Sakigake (January 1985), Giotto (July 1985),
Suisei (August 1985), Galileo (October 1989), NEAR-
Shoemaker (February 1996), Cassini (October 1997),
communications satellite 83
Deep Space 1 (October 1998), Stardust (February 1999),
Genesis (August 2001), CONTOUR (July 2002),
MUSES-C (November 2002), Rosetta (January 2003),
Deep Impact (January 2004), Dawn (May 2006), and
Comet Nucleus Sample Return. Canceled projects
include CRAF and Deep Space 4 (Champollion).
Comet Nucleus Sample Return (CNSR)
A spacecraft designed to return a pristine sample of material
from a comet nucleus to Earth in order to provide
clues to the early history of the Solar System. CNSR is
identified in NASA’s Office of Space Science Strategic
Plan but remains at the concept stage.
COMETS (Communications and Broadcasting
Experimental Test Satellite)
A Japanese communications satellite launched by
NASDA (National Space Development Agency); it is
also known by the national name Kakehashi (“bridge”).
COMETS carries Ka-band communications and intersatellite
data relay payloads (see frequency bands).
Although premature shutdown 44 seconds into the H-2
second stage burn put the satellite into a much lower
orbit than intended, the onboard Unified Propulsion
System was able to raise the orbit to a more useful height.
Launch
Date: February 21, 1998
Vehicle: H-2
Site: Tanegashima
Orbit: 479 × 17,710 km × 30.1°
COMINT (communications intelligence)
A subcategory of SIGINT (signals intelligence) that
involves messages or voice information derived from the
interception of foreign communications.
command destruct
A system that destroys a launch vehicle and is activated
on command of the range safety officer whenever vehicle
performance degrades enough to be a safety hazard.
The destruction involves sending out a radio signal that
detonates an explosive in the rocket or missile.
Command Module
See Apollo.
communications satellite
See article, pages 84–85.