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

122 energy density
accelerate an object. (2) An intrinsic property of everything
in the universe, including radiation, matter (see
mass-energy relationship), and, strangely enough, even
empty space (see vacuum energy).
energy density
The energy contained per unit volume of space. General
relativity provides a way of calculating the energy density
associated with a given curvature of space-time. Some
schemes for faster-than-light (FTL) travel call for regions
of negative energy density—a strange condition, but one
that exists in phenomena such as the Casimir effect.
Enterprise
The first flight-capable version of the Space Shuttle
Orbiter but one designed for ground and gliding tests
only; its official designation is Orbiter OV-101. NASA
had originally intended to call this vehicle Constitution in
honor of several U.S. Navy vessels of the same name,
including the “Old Ironsides” frigate launched in 1797
and now on display at the Boston Navy Yard. Constitution
was also appropriate in view of the American Bicentennial,
which was being commemorated at the time of factory
rollout in 1976. However, Star Trek fans petitioned—
sending 100,000 letters to the White House—to have the
first Shuttle named after the famous fictional starship.
NASA relented and changed the name from Constitution
to Enterprise prior to rollout, pointing out that several
Navy vessels had also carried the name Enterprise, including
the first nuclear-powered aircraft carrier. During the
summer of 1976, Enterprise underwent horizontal vibration
tests at the Rockwell plant in Palmdale, California,
designed to test the Shuttle structural integrity under simulated
launch and landing conditions. Upon completion
Enterprise Enterprise flies free after being released from NASA’s 747 Shuttle Carrier Aircraft over Rogers Dry Lakebed during the
second of five free flights carried out as part of the Shuttle program’s Approach and Landing Tests. NASA