Description:
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 Boeing 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.
Boeing has successfully launched seven 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. |
|
