Known collectively as the Delta IV Medium-plus, the three new vehicles will retain the efficient, cost-effective modular design of the entire Delta IV fleet through the use of the Delta IV "common booster core." Booster cores are 38 meters long and 5 meters in diameter -- roughly the size of a Boeing wide-body airplane.

The Delta IV fleet is designed to offer both commercial and government customers a wide range of payload capability. For missions to geosynchronous transfer orbit (GTO), the range extends from 2.2 metric tons (Delta IV Small) through 13.2 metric tons (Delta IV Heavy).

The Medium-plus versions are distinguished by the number of Alliant Techsystems-built solid rocket motors attached to the booster core and the size of the upper stages and payload fairings, which protect the satellites during the early ascent phases of flight.

"The three configurations of the Delta IV Medium-plus have been designed to give our commercial customers flexibility over a wide range of payload weights, coupled to the cost effectiveness of the modular design," reports Gale Schluter, vice president and general manager of Expendable Launch Systems, the Boeing business segment responsible for developing, marketing and flying the Delta fleet.

Members of the Delta IV Medium-plus family are:

• Delta IV Medium-plus (4,2) with two solid rocket motors and a 4-meter fairing for a GTO payload of 5.8 metric tons.
• Delta IV Medium-plus (5,2) with two solid rocket motors and a 5-meter fairing for a GTO payload of 4.7 metric tons.
• Delta IV Medium-plus (5,4) with four solid rocket motors and a 5-meter fairing for a GTO payload of 6.7 metric tons.

Delta IV launch vehicles are evolved from the Delta family of rockets which has been lifting satellites into orbit since 1960.

The Delta IV production team includes: Aerojet, Sacramento, Calif., second-stage engine for the Delta IV Small; Alliant Techsystems, Magna, Utah, solid rocket motors for the Delta IV Medium-plus versions; Allied Signal Aerospace, Teterboro, N.J., Redundant Inertial Flight Control Assembly for guidance control of all Delta IVs; Pratt & Whitney, West Palm Beach, Fla., second-stage engines for the Delta IV Medium and Heavy versions; and Raytheon Engineers and Constructors, design and construction of Delta IV launch facilities.