EVOLVED EXPENDABLE LAUNCH VEHICLE
Evolved Expendable Launch Vehicle, known as EELV, is designed to
improve the United States' access to space by making space launch
vehicles more affordable and reliable. The program replaced launch
systems with two families of launch vehicles, each using common
components and common infrastructure. The vehicles are the Boeing
Delta IV and Lockheed Martin Atlas V. EELV's operability improvements
over current systems include a standard payload interface, standardized
launch pads and increased off-pad processing.
As the Air Force's space-lift modernization program, EELV was
designed to reduce launch costs by at least 25 percent over heritage
Atlas, Delta and Titan space launch systems.
The initial phase of the EELV program, Low Cost Concept
Validation (LCCV), was successfully completed in November 1996. LCCV
emphasized competition in preliminary designs and risk reduction demonstrations.
Four $30-million contracts were awarded during this phase to Alliant
Techsystems, The Boeing Company, Lockheed Martin Corporation and McDonnell
Douglas Aerospace. (Note: Boeing acquired McDonnell Douglas at about
the time this competition ended.)
During the second phase, pre-engineering and manufacturing
development, two $60-million, 17-month contracts were awarded to The
Boeing Company and Lockheed Martin Corporation to continue refining
their system concepts and complete a detailed system design.
EELV phase three began in October 1998 with the award
of two development agreements and two initial launch services contracts
(known as Buy 1) totaling more than $3 billion. The development agreements
run through fiscal year 2007 and the initial launch services contracts
will run through FY 2012. Additional launch service awards were made
in Buy 2 and proposed in Buy 3 contracts.
Boeing Delta IV
The Delta IV family of launch vehicles is designed for
optimum performance for a wide range of flight profiles, and is capable
of carrying payloads ranging from 4,231 kg (9,327 lb) to 12,757 kg (28,124
lb) to geosynchronous transfer orbit (GTO). The Delta IV Medium, Medium-Plus
and Heavy configurations are evolved, combining highly reliable, flight
proven systems from Delta II and III, while incorporating the latest
technology into a family of vehicles maximizing the use of common hardware.
Commonality between all of the systems is central to the
Delta IV. Each Medium & Medium-Plus vehicle uses a single common
booster core (CBC), while the Heavy uses three CBCs. The Pratt and WBoeing
Rocketdyne-built RS-68, a liquid hydrogen/liquid oxygen engine that
produces 663,000 lbs of liftoff thrust, powers the first stage. This
engine is mounted to the CBC first-stage structure and was designed
for ease of manufacture by significantly reducing part count and thereby
increasing reliability. Thirty percent more efficient than conventional
liquid oxygen/kerosene engines, the RS-68 is environmentally friendly,
producing steam as a combustion by-product. The three Delta IV Medium-Plus
vehicles use a single CBC and are augmented by either two or four 1.5-meter
(60-inch) diameter solid rocket strap-on graphite epoxy motors (GEMs).
The cryogenic second stage is an evolutionary design incorporating
the Redundant Inertial Flight Control Assembly (RIFCA) from Delta II
and the Pratt & Whitney RL10B-2 engine. The Delta IV Medium &
Medium-Plus (4,2) vehicles use the same 4-meter diameter second stage,
while the Delta IV Medium-Plus (5,2), Medium-Plus (5,4) and Heavy vehicles
use the same RL10B-2 engine, but have larger 5-meter diameter fuel tanks
and stretched oxidizer tanks.
On the Delta IV Medium & Medium-Plus (4,2), the payload
is encapsulated in a 4-meter (13.1-feet) diameter payload fairing (PLF)
for protection. On the Delta IV Medium-Plus (5,2), Medium-Plus (5,4)
and Heavy, the payload is encapsulated with a similar 5-meter (16.7-feet)
diameter payload fairing. Both the 4 and 5-meter diameter PLFs are composite
bisector structures that were evolved from the Delta II 2.9 meter diameter
and the Delta III 4-meter diameter PLFs. The Heavy vehicle can also
employ a 5-meter diameter aluminum trisector fairing with Titan IV heritage.
United Launch has successfully launched eight Delta IV
launch vehicles. Delta IV's inaugural flight was marked by the successful
launch of a commercial satellite on a Medium-Plus (4,2) in November
2002. Two Air Force communication satellites were successfully launched
on Delta IV Medium vehicles in 2003, and the first Heavy vehicle was
launched in December 2004.
Lockheed Martin Atlas V
The Lockheed Martin Atlas V resulted from Lockheed Martin's
combination of the best practices from both the Atlas and Titan programs
into an evolved commercial and government launch system for the 21st
century. Atlas V builds on the design innovations demonstrated on Atlas
III and incorporates a structurally stable booster propellant tank,
enhanced payload fairing options and optional strap-on solid rocket
Further, all Atlas V to date were successfully launched.
The Atlas V family uses a single-stage Atlas main engine, the Russian
RD-180 and the newly developed Common Core Booster (CCB)TM with up to
five strap-on solid rocket boosters. The CCBTM is 12.5 ft. (3.8 m) in
diameter by 106.6 ft. (32.5m) long and uses 627,105 lbs. (284,453 kg)
of liquid oxygen and RP-1 rocket fuel propellants.
Additionally, on Atlas V, United Launch Allience introduced
a 4.57-meter usable diameter Contraves payload fairing in addition to
retaining the option to use the heritage Atlas payload fairings. The
Contraves fairing is a composite design and is based on flight proven
hardware. Three configurations will be manufactured to support Atlas
V. The short and medium length configurations will be used on the Atlas
V 500 series.
The Centaur upper stage uses a pressure stabilized propellant
tank design and cryogenic propellants. The Centaur stage for Atlas V
is stretched 5.5 ft (1.68 m) and is powered by either one or two Pratt
& Whitney RL10A-4-2 engines, each engine developing a thrust of
22,300 lbs. (99.2 kN). Operational and reliability upgrades are enabled
with the RL10A-4-2 engine configuration. The inertial navigation unit
(INU) located on the Centaur provides guidance and navigation for both
Atlas and Centaur, and controls both Atlas and Centaur tank pressures
and propellant use. The Centaur engines are capable of multiple in-space
starts, making possible insertion into low-earth parking orbit, followed
by a coast period and then insertion into GTO.
Primary function: Space lift vehicle
Primary contractor: United Launch Alliance
Primary function: Spacelift vehicle
Primary contractor: United Launch Alliance
Dimensions: The common core booster is 12.5 ft in diameter by 106.6
ft. long and uses 627,105 lbs. of liquid oxygen and RP-1 rocket fuel
propellants. The Centaur Stage for Atlas V is stretched 5.5 feet and
powered by either one or two Pratt & Whitney RL10A-4-2 engines.
The U.S. Air Force Evolved Expendable Launch Vehicle will
serve America's lift-to-orbit requirements with two launch vehicle families,
assuring access to space for both government and military payloads.
Common Core BoosterTM and CCBTM are registered trademarks of United
Point of Contact:
Air Force Space Command, Public Affairs Office
150 Vandenberg Street, Suite 1105
Peterson AFB, Colorado 80914.
DSN 692-3731, or (719) 554-3731
TO: THE USAF SPACE INDEX