Glossary of Space Exploration Terminology

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N
N2O4
Nitrogen Tetroxide. Also abbreviated NTO.
Nadir
The direction from a spacecraft directly down toward the center of a planet. Opposite the zenith.
NAL
National Aerospace Laboratory of Japan.
NASA
National Aeronautics and Space Administration.
NASDA
National Space Development Agency (Japan).
Nautical mile
The distance spanned by one minute of arc in latitude, defined internationally as 1,852 meters (6,076.1033 feet).
Neptune
Eighth planet from the Sun, a gas giant or Jovian planet.
Neutron
Atomic particles having approximately the same mass as a hydrogen atom; very penetrating.
Newton
That force which gives a mass of 1 kilogram an acceleration of 1 meter per second per second; equal to 100,000 dynes.
NiCd
Nickel Cadmium.
Nitric acid
A liquid oxidizer that reacts spontaneously with hydrazine. Also see IRFNA and IWFNA.
Nitrogen tetroxide
A liquid oxidizer that reacts spontaneously with hydrazine.
Noctilucent clouds
Weakly-luminous clouds, seen at night at heights of about 50 miles (80 km) above the Earth.
Non-coherent
Communications mode wherein a spacecraft generates its downlink frequency independent of any uplink frequency.
NORAD
North American Air Defense Command (USA).
Nose shroud
A cover on the nose of a rocket or spacecraft which jettisons before insertion into orbit.
Nozzle
The projecting aperture at the end of a combustion chamber serving as an outlet for the exhaust gases.
NRC
National Research Council (USA).
NTO
Nitrogen Tetroxide. Also abbreviated N2O4.
Nucleus
The central body of a comet.

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Rocketry & Space Technology

Glossary courtesy of Robert Braeunig's
Rocketry & Space Technology website.