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

Statsionar
See Raduga.
stay time
The average time spent by a gas molecule in a liquid-fuel
rocket engine’s combustion chamber before exiting
from the nozzle and producing thrust.
STEDI (Student Explorer Demonstration Initiative)
A program, managed by USRA (Universities Space
Research Association) for NASA, that is designed to
demonstrate that a small scientific or technology-based
satellite could be designed, fabricated, launched, and
operated for around $10 million. It is part of NASA’s
“smaller, cheaper, faster” initiative for research spacecraft.
Stella
A French geodetic satellite, carrying 60 laser reflectors
mounted on a dense sphere of uranium alloy, that is
tracked to measure small perturbations in Earth’s gravitational
field. Reflected laser beams enable measurements,
accurate to about 1 cm, of the geoid, oceanic and terrestrial
tides, and tectonic movements. Stella’s twin, Starlette,
launched in 1975, is also still in use.
Launch
Date: September 26, 1993
Vehicle: Ariane 4
Site: Kourou
Orbit: 793 × 803 km × 98.7°
Mass: 48 kg
Stennis Space Center (SSC)
One of 10 NASA field centers in the United States. Previously
known as the Mississippi Test Facility, it was
renamed in 1988 after U.S. Senator John C. Stennis.
Located in Hancock County, Mississippi, about 80 km
northeast of New Orleans, it is the primary center for
testing and flight certifying rocket propulsion systems for
the Space Shuttle and future generations of space vehicles.
In the past it was the static test site for Saturn- and
Nova-class launch vehicles. All Space Shuttle Main
Engines must pass a series of test firings at Stennis Space
Center prior to being installed in the back of the Orbiter.
Stennis is also NASA’s lead center for commercial remote
sensing within the Mission to Planet Earth Enterprise.
STENTOR (Satellite de Télécommunications
pour Expériences de Nouvelles Technologies
en Orbite)
An experimental communications satellite developed by
CNES (the French space agency) in association with
Stewart, Homer J. 419
French Telecom. STENTOR will carry out propagation
and transmission experiments, especially at wavelengths
that are shorter than those currently used for satellites
communications. Launch was scheduled for the second
half of 2002.
STEP (Satellite Test of the Equivalence Principle)
A satellite designed to test, in microgravity, a wellestablished
physical law—the Equivalence Principle—that
all falling objects accelerate at the same rate. Until now,
this principle escaped deep scrutiny because experiments
have always been limited by gravitational conditions at
the Earth’s surface. STEP, which involves a collaboration
between NASA and ESA (European Space Agency), will
test the principle to an accuracy 100,000 times greater
than that achieved in terrestrial laboratories. It will also
conduct experiments in quantum mechanics and gravity
variations. STEP was selected by NASA for study as a
SMEX (Small Explorer).
step principle
A design feature of rockets in which one stage is mounted
directly onto another. When a lower stage is used up, it is
ejected, and the next upper stage takes over. With each
stage’s ejection, the weight of the spacecraft decreases, so
the next stage has less work to do.
step rocket
A multistage rocket.
STEREO (Solar-Terrestrial Relations Observatory)
A mission to understand the origin of coronal mass ejections—powerful
eruptions on the Sun in which as much
as 10 billion tons of the solar atmosphere can be blown
into interplanetary space—and their consequences for
Earth. It will consist of two spacecraft, one leading and
the other lagging Earth in its orbit. These spacecraft will
each carry instrumentation for solar imaging and for insitu
sampling of the solar wind. STEREO, the third of
NASA’s Solar Terrestrial Probe missions, is being
designed and built at the Johns Hopkins University
Applied Physics Laboratory and is scheduled for launch
in 2005.
Stewart, Homer J. (1915–)
A prominent aerospace engineer involved with the U.S.
space program. Stewart earned a B.S. in aeronautic engineering
from the University of Minnesota in 1936,
joined the faculty of the California Institute of Technology
(Caltech) in 1938, and earned his doctorate from
Caltech two years later. In 1939, he took part in pioneering
rocket research with other Caltech engineers and
scientists, including Frank Malina, in the foothills of
Pasadena. Out of their efforts, JPL ( Jet Propulsion