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

238 LiPS (Living Plume Shield)
LiPS (Living Plume Shield)
Plume shields ejected from the upper stage of NOSS
(Naval Ocean Surveillance Satellite) primary payloads;
they were used as subsatellites for conducting technology
demonstrations. The plume shield, which deflects the
exhaust of the upper-stage motor away from the primary
payload, is customarily jettisoned after use to become
space debris. However, on the LiPS experiments, the
anterior surfaces of the shield, which are unaffected by
the plume, were fitted with a variety of small experiments.
(See table, “LiPS Missions.”)
liquid hydrogen (H 2)
Hydrogen in its liquid state, used as a cryogenic rocket
fuel; hydrogen gas turns to liquid under standard atmospheric
pressure at −263°C. When oxidized by liquid oxygen,
liquid hydrogen delivers about 40% more thrust per
unit mass than other liquid fuels, such as kerosene.
Commonly referred to in rocketry as LH2. 273
liquid oxygen (O 2)
Oxygen in its liquid state, used as the oxidizer in many
liquid fuel engines. Oxygen gas turns to liquid under
standard atmospheric pressure at −183°C. Commonly
referred to in rocketry as LOX.
liquid propellant
A liquid ingredient used in the combustion chamber of
a rocket engine. Liquid propellants may be either bipropellants,
which consist of a liquid fuel (such as kerosene
or liquid hydrogen) and a liquid oxidizer (such as liquid
oxygen or nitrogen tetroxide), or monopropellants (such
as hydrazine). Liquid propellants, such as liquid oxygen
and liquid hydrogen, that must be kept at a low temperature
in order to remain liquid are known as cryogenic
propellants. See liquid-propellant rocket engine.
liquid-air cycle engine
An advanced engine cycle that uses liquid hydrogen fuel
to condense air entering an inlet. Liquid oxygen is separated
from the condensed air and pumped into the com-
LiPS Missions
Launch site: Vandenberg Air Force Base
Launch
Mission Date Vehicle Notes
LiPS 1 Dec. 9, 1980 Atlas F Launch vehicle failed on takeoff.
LiPS 2 Feb. 8, 1983 Atlas H Carried UHF single-channel transponder.
LiPS 3 May 15, 1987 Atlas H Data returned from over 140 solar-cell experiments.
bustion chamber, where it is burned with the hydrogen
to produce thrust.
liquid-fueled rocket
A rocket that derives its thrust from one or more liquidpropellant
rocket engines.
liquid-propellant rocket engine
A rocket propulsion system in which a liquid fuel (such
as kerosene or liquid hydrogen) is combined in a thrust
chamber with a liquid oxidizer (such as liquid oxygen or
fuming nitric acid). Very efficient and controllable, such
engines are used extensively in spaceflight. Unlike solidpropellant
rocket motors, they can be shut off by
remote command, simply by closing off their fuel line. In
some cases, the thrust can also be varied over a certain
range.
LISA (Laser Interferometer Space Antenna)
An array of three NASA spacecraft flying 5 million km
apart in the shape of an equilateral triangle. The center
of the triangle will be in the ecliptic plane one astronomical
unit from the Sun and 20° behind Earth. The
LISA mission, which is being designed at JPL ( Jet
Propulsion Laboratory), is intended to observe gravitational
waves from galactic and extragalactic sources,
including the supermassive black holes found in the centers
of many galaxies. Gravitational waves are one of the
fundamental building blocks of our theoretical picture
of the universe, but although there is strong indirect evidence
for their existence, they have not yet been directly
detected. The LISA spacecraft, flying in formation, will
be sensitive to the distortion of space caused by passing
gravitational waves. Each spacecraft will contain two
free-floating “proof masses.” The proof masses will
define optical paths 5 million km long, with a 60° angle
between them. Lasers in each spacecraft will be used to
measure changes in the optical path lengths with a precision
of 20 pm (trillionths of a meter). If approved, the
project will begin development in 2005 with a planned
launch in 2008.