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

EELV (Evolved Expendable Launch Vehicle)
A 1995 U.S. Air Force specification for a new generation
of American medium- to heavy-lift launch vehicles
intended to reduce the cost of placing large payloads in
orbit by at least 25% over existing Delta,Atlas, and Titan
rockets. Contracts for the EELV were eventually awarded
to Boeing for the Delta IV and Lockheed Martin for the
Atlas V.
effective exhaust velocity
The velocity of an exhaust stream after reduction by
effects such as friction, nonaxially directed flow, and
pressure differences between the inside of the rocket and
its surroundings. The effective exhaust velocity is one of
two factors determining the thrust, or accelerating force,
that a rocket can develop, the other factor being the
quantity of reaction mass expelled from the rocket in unit
time. In most cases, the effective exhaust velocity is close
to the actual exhaust velocity.
As an example, a present-day chemical rocket may
achieve an effective exhaust velocity of up to 4 km/s.
Although this is not high compared with what may be
achieved in the future, a large thrust is nevertheless produced
owing to the enormous amount of reaction mass,
which is jettisoned every second. Chemical rockets generate
high thrust, but only for short periods before their
supply of propellant is used up. The final velocity a
spacecraft can achieve is fixed by the exhaust velocity of
its engines and the spacecraft’s mass ratio as shown by
the rocket equation. Because the exhaust velocity of
chemical rockets is so low, they would demand an
unachievably high mass ratio in order to propel a spacecraft
to the kind of speeds required for practical interstellar
flight. Other propulsion strategies must therefore be
considered for journeys to the stars.
Efir
Soviet scientific spacecraft based on the Vostok/Zenit
design; “efir” is Russian for “ether.” These spacecraft were
announced under the catchall Cosmos designation. (See
table, “Efir Satellites.”)
Launch
Vehicle: Soyuz-U
Site: Plesetsk
Mass: 6,300 kg
Efir Satellites
Ehricke, Krafft Arnold 117
EGNOS (European Geostationary Navigation
Overlay Service)
A European satellite navigation system intended to augment
the two operational military satellite navigation systems—the
American GPS and the Russian GLONASS—
and make them suitable for safety-critical applications
such as flying aircraft or navigating ships through narrow
channels. Consisting of three geostationary satellites and
a network of ground stations, EGNOS will transmit a signal
containing information on the reliability and accuracy
of the positioning signals sent out by GPS and
GLONASS. It will allow users in Europe and beyond to
determine their position to within 5 m, compared with
about 20 m at present. EGNOS is a joint venture of ESA
(European Space Agency), the European Commission,
and the European Organisation for the Safety of Air Navigation.
It is Europe’s contribution to the first stage of the
global navigation satellite system (GNSS) and is a precursor
to the Galileo satellite navigation system. EGNOS
will become fully operational in 2004; meanwhile, potential
users can acquaint themselves with the facility using a
test signal broadcast by two Inmarsat satellites.
egress
The act of or the mechanism for exit from an enclosure.
In a spacecraft this can describe the act of a crew member
exiting from the vehicle or the exit chamber, pressure
lock, and hatchways themselves.
EGS (Experimental Geodetic Satellite)
A Japanese geodetic satellite used by NASDA (National
Space Development Agency) to test a new launch vehicle,
the H-1, and determine the accurate location of
remote islands; it was also known by its national name,
Ajisai (“hydrangea”).
Launch
Date: August 12, 1986
Vehicle: H-1
Site: Tanegashima
Orbit: 1,479 × 1,497 km × 50.0°
Mass: 685 kg
Ehricke, Krafft Arnold (1917–1984)
A German-born rocket-propulsion engineer who was the
chief designer of the Centaur and who produced many
Spacecraft Launch Date Orbit Duration (days)
Cosmos 1543 Mar. 10, 1984 214 × 401 km × 62.8° 26
Cosmos 1713 Dec. 27, 1985 215 × 397 km × 62.8° 26