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Further Reading

Delta IV

Boeing's Delta IV used a larger booster core equipped with a Rocketdyne RS-68 liquid hydrogen engine than previous Delta variants. A new upper stage based on the Single Engine Centaur design was added along with varying numbers of new Delta III Graphite Epoxy Motors (GEMs) to handle a wide variety of medium class payloads. For heavier missions, three Delta IV core vehicles might be combined in a side-by-side arrangement similar to Lockheed Martin's Titan IV launch vehicle. Boeing intended to process the Delta IVs under an Integrate-Transfer-Launch (ITL) concept of operations that would not tie up the launch pad for extended periods of time. The Delta IVs were launched from Complex 37, Cape Canaveral Air Force Station, Florida.

The Delta IV family blended new and mature technology to launch virtually any size medium or heavy payload into space, with the largest success being the flight proven RS-68 engine. The Delta IV is composed of five vehicle configurations based on a common booster core (CBC) first stage powered by the RS-68 engine. Delta IV second stages were derived from the Delta III second stage, using the same RL10B-2 engine, but with two sizes of expanded fuel and oxidizer tanks, depending on the model.

Unlike the Atlas III program, Boeing (formerly McDonnel Douglas) did not improve the Delta III's engines for use on the Delta IV, but did introduce a number of new features that would be used on the Delta IV. The upper stage introduced on the Delta III was used in an expanded form (using the same RL10B-2 engine as the previous version with larger fuel and oxidizer tanks) on the Delta IV, along with the Redundant Inertial Flight Control Assembly (RIFCA) avionics system that debuted on the Delta III.

The RS-68 was designed to reduce complexity versus the SSME at the expense of efficiency and weight. It had 80% fewer parts than the SSME, and a 10% reduction in specific impulse. The combustion chamber burns liquid hydrogen and liquid oxygen at 1410 lbf/in² (9.7 MPa). The specific impulse is 4 kN·s/kg) or 408 lbf·s/lb at maximum power level. The engine itself is a gas generator cycle engine with two independent turbopumps. The nozzle has an expansion ratio of 21.5 and is made from an ablative material.

In designing the five Delta IV configurations, Boeing conducted extensive discussions with government and commercial customers concerning their present and future launch requirements. Proven technical features and processes were carried over from earlier Delta vehicles to Delta IV. New technologies and processes were incorporated where they added capability or reduced cost. The originally estimated launch price in 1999 was $170 million. Due to the collapse of the commercial launch market, this was revised by the USAF in November 2004 to $ 254 million.

On 20 November 2002 the first flight of the Boeing Delta IV family of rockets successfully delivered the commercial telecommunications satellite W5 for Eutelsat SA. The Delta IV lifted off at 5:39 p.m. EST from Space Launch Complex 37B, Cape Canaveral Air Force Station, Florida. Approximately 37 minutes after liftoff, the rocket deployed the W5 spacecraft to a geosynchronous transfer orbit with a perigee of 539 kilometers above the Earth. The Delta IV rocket that deployed W5 was a Medium+ (4,2) configuration of the five-member Delta IV family of rockets developed by Boeing Expendable Launch Systems, a major program of Boeing Integrated Defense Systems. The Medium+ category of the Delta IV featured the Boeing Common Booster Core first stage, powered by the Boeing Rocketdyne RS-68 main engine, two Alliant Technologies strap-on solid rocket motors, the flight proven Pratt & Whitney RL10B-2 upper stage engine, and a four-meter Boeing composite payload fairing.

In 2003 the Boeing Company pulled its new Delta IV booster out of the commercial satellite business. According to Boeing's Integrated Defense Systems Chief, the company was taking $1.1 billion in charges over seven years and would "eliminate all commercial launches over the next five years." This was a result of the downturn in the commercial space business. However, Boeing would continue to launch government payloads using the Delta IV as part of its USAF Evolved Expendable Launch Vehicle (EELV) contract. Boeing would also continue to provide the Sea Launch Zenit 3SL for commercial missions and the Delta II for government missions.

On 21 December 2004 the Delta IV Heavy (Delta IV-H) variant launched for the first time carrying two student-built nano-satellites. The demonstration satellite was supposed to have been inserted into a sub-geosynchronous 36,350 km circular orbit but was instead deployed in a 19,035 km x 36,413 km orbit following a 5-hour and 50-minute flight. A shorter than expected first burn of the Centaur upper stage led to an orbit well below that planned. The Air Force EELV program office claimed that the primary flight objectives were accomplished. These included the heavy boost phase, flight of the new five-meter diameter Centaur upper stage and five-meter payload fairing, extended coast, upper stage third burn and payload separation, and activation and usage of Space Launch Complex 37B at Cape Canaveral Air Force Station, Florida..