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

6 Able
passage through a dusty medium in space, such as the
tail of a comet. An expendable surface made of ablative
material may be used as a coating in a combustion chamber
or on the heat shield of a reentry vehicle. As the
ablative material absorbs heat, it changes chemical or
physical state and sheds mass, thereby carrying the heat
away from the rest of the structure. See reentry thermal
protection.
Able
(1) A modified form of the Aerojet AJ-10 second stage of
the Vanguard rocket used as the second stage of the Thor-
Able, Thor-Able Star, and Atlas-Able launch vehicles. (2)
An early, ill-fated American lunar program approved by
President Eisenhower on March 27, 1958, and intended to
place a satellite in orbit around the Moon. Project Able
became the first lunar shot in history, preceding even
Luna 1, when a Thor-Able took off at 12:18 GMT on
August 17, 1958, before a small group of journalists. Unfortunately,
only 77 seconds into the flight, the Thor’s turbopump
seized and the missile blew up. Telemetry from
the probe was received for a further 123 seconds until the
39-kg spacecraft ended its brief journey by falling into the
Atlantic. Although not given an official name, the probe
is referred to as Pioneer 0 or Able 1. Before the launch of
the second probe, the whole program was transferred to
NASA, which renamed it Pioneer. (3) A rhesus monkey
housed in a biocapsule that was sent on a suborbital flight
by a specially configured Jupiter missile on May 28, 1959.
Able and its companion Baker, a female squirrel monkey
placed in a second biocapsule, became the first live animals
to be recovered after traveling outside Earth’s atmosphere.
Able died on June 1, 1959, from the effects of
anesthesia given to allow the removal of electrodes. An
autopsy revealed that Able had suffered no adverse effects
from its flight. 236
abort
The premature and sudden ending of a mission because of
a problem that significantly affects the mission’s chances
of success.
acceleration
The rate at which the velocity of an object changes. Acceleration
can be linear (in a straight line), angular (due to
a change in direction), or negative (when it is known as
deceleration). Related terms include: (1) acceleration stress,
which is the physiological effect of high acceleration or
deceleration on the human body; it increases with the
magnitude and duration of the acceleration. Longitudinal
accelerations cannot be tolerated as well as transverse
ones, as the former have a stronger influence on the cardiovascular
system, and (2) acceleration tolerance, which is
the maximum acceleration or deceleration that an astronaut
can withstand before losing consciousness.
acceleration due to gravity (g)
The acceleration that an object experiences when it falls
freely close to the surface of a body such as a planet. Its
value is given by the formula g = GM/R 2 , where M is the
mass of the gravitating body, R its radius, and G the gravitational
constant. On Earth, g is about 9.8 m/s 2 ,
although its value varies slightly with latitude.
accelerometer
An instrument that measures acceleration or the gravitational
force capable of imparting acceleration. It usually
employs a concentrated mass that resists movement
because of its inertia; acceleration is measured in terms
of the displacement of this mass relative to its supporting
frame or container.
ACCESS (Advanced Cosmic-ray Composition
Experiment on the Space Station)
An experiment to study the origin and makeup of cosmic
rays over a three-year period. ACCESS will be
attached to the International Space Station and is due to
replace AMS (Alpha Magnetic Spectrometer) in about
2007. Its two instruments, the Hadron Calorimeter and
the Transition Radiation Detector, will measure the elemental
makeup of cosmic rays from lightest nuclei to
heaviest and determine if the flux of high-energy electrons
in cosmic rays varies with direction, as would be the
case if some come from local sources.
ACE (Advanced Composition Explorer)
A NASA satellite designed to measure the elemental and
isotopic composition of matter from several different
sources, including the solar corona and the interstellar
medium. ACE was placed in a halo orbit around the first
Lagrangian point (L1) of the Earth-Sun system, about
1.4 million km from Earth. It carries six high-resolution
sensors and three monitoring instruments for sampling
low-energy particles of solar origin and high-energy galactic
particles with a collecting power 10 to 1,000 times
greater than previous experiments. The spacecraft can
give about an hour’s advance warning of geomagnetic
storms that might overload power grids, disrupt communications,
and pose a hazard to astronauts.
Launch
Date: August 25, 1997
Vehicle: Delta 7920
Site: Cape Canaveral
Orbit: halo
Mass at launch: 785 kg