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

150 GEC (Global Electrodynamics Connections)
and the follow-on of the Advanced Microwave Scanning
Radiometer (AMSR). It may also carry NASA’s Alpha
SCAT and CNES’s (the French space agency’s) Polarization
and Directionality of Earth’s Reflectance (POLDER).
GCOM-B1 will be able to study the distribution of
aerosols and water vapor and make measurements of ice
coverage, phytoplankton concentrations, and sea surface
wind directions. Launch is planned for about 2006.
GEC (Global Electrodynamics Connections)
A planned cluster of four NASA satellites in polar orbits,
combined with ground-based observations, that will
make systematic multipoint measurements to complete
our understanding of the role played by the ionosphere
and thermosphere in the Sun-Earth connection. GEC is
a future Solar Terrestrial Probe mission.
Geizer
A series of satellites that relay telecommunications for
the Russian Ministry of Defense.
gelled propellants
Rocket propellants that have additives to make them
thixotropic. This means they have the consistency of jelly
when at rest but can be made to move as a liquid through
pipes, valves, and so on. Experimental rocket engines
have shown gelled propellants to be generally safer than
liquid propellants yet capable of performing as well.
Gemini
See article, pages 151–158.
Gemini-Titan II
A modified version of the Titan II intercontinental ballistic
missile used as the launch vehicle for the Gemini
program. In order for the Titan II to be man-rated, a
number of safety systems had to be added, including a
malfunction detection system to warn the crew of any
failure in the rocket’s equipment, backup electrical and
hydraulic systems, and monitoring devices to check the
rocket before launch and provide telemetry about vehicle
performance during flight. In the event of an emergency,
the only mode of escape for the crew was by ejection seat.
The Titan gave a much smoother ride than the Mercury-
Atlas—and some astronauts remarked that they were
aware of initial motion only through their instrument
displays.
general theory of relativity
The geometric theory of gravitation developed by Albert
Einstein, incorporating and extending the special theory
of relativity to accelerated frames of reference and introducing
the principle that gravitational and inertial forces
are equivalent. General relativity treats special relativity
as a restricted subtheory that applies locally to any region
of space sufficiently small that its curvature can be
309, 311
neglected.
generation ship
An immense, relatively slow-moving spacecraft, also
known as an interstellar ark, aboard which many generations
would live and die on a voyage between stars. The
generation ship has been offered as an alternative to
spacecraft that travel at much higher speeds carrying conventional-sized
crews. The idea of a vessel carrying a civilization
from a dying solar system toward another star for
a new beginning was envisioned in 1918 by Robert Goddard.
114 But, perhaps concerned about professional criticism,
he placed his manuscript in a sealed envelope, and
it did not appear in print for over half a century. Konstantin
Tsiolkovsky and J. D. Bernal wrote about artificial
planets and self-contained worlds in the 1920s, as did
Olaf Stapledon in his visionary novels, and by the 1940s
the generation ship concept had been fully expanded by
science fiction writers in the publications of Hugo Gernsback
and others. Robert Heinlein (Orphans of the Sky,
1958) first raised the possibility that the crew might eventually
forget they were aboard a ship and believe instead
that they were the inhabitants of a small world (a theme
taken up in one of the original Star Trek episodes: “For the
World Is Hollow and I Have Touched the Sky”). In 1952,
L. R. Shepherd examined the idea of the generation ship
in more technical detail and described a nuclear-propelled
million-ton interstellar vessel shaped as an oblate spheroid,
which he called a “Noah’s Ark.” Such a ship would be
a microcosm of human civilization with a substantial and
highly varied population, extensive educational, recreational,
and medical facilities, food production areas,
research laboratories, and so forth—effectively, a miniature,
nomadic planet. There is perhaps a strange attraction
in the idea, though whether anyone would willingly volunteer
to exile themselves to such an environment knowing
that they would die some fraction of the way to the
ultimate goal is hard to say. Perhaps there would be less of
a psychological problem for subsequent generations who
were born aboard the ship and therefore never knew what
life was like on the surface of a planet under open skies.
Then again, how difficult would it be for those who
finally reached journey’s end to step outside the confines
of their artificial world? Like many other old ideas in
space travel, including Lucian’s waterspout and Well’s
cavorite, the generation ship now seems quaint and
romantic. Almost certainly, interstellar travel will never be
accomplished by this means, though it is still possible that
the related concept of the space colony will come to
fruition.