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Delta IV)
The Delta IV family of rockets are EELVs (evolved expendable launch vehicles) built by Boeing IDS. They come in five versions: medium, medium+ (4,2), medium+ (5,2), medium+ (5,4), and heavy. These vehicles are primarily designed to satisfy the needs of the US Military market.
The first stage of a Delta IV consists of one, or in the Heavy variety three, CBCs (common booster cores) powered by a Rocketdyne RS-68 engine. Unlike most first-stage rocket engines, which use solid fuel or kerosene, the RS-68 engines burn liquid hydrogen and liquid oxygen.
The upper stage of the Delta IV is powered by a Pratt & Whitney RL-10B2 engine. In the medium variety it has a 4-m–diameter payload fairing. It is capable of launching 4,210 kg (9,285 lb.) to geosynchronous transfer orbit (GTO).
The Delta IV medium+ (4,2) is similar to the medium, but uses two 1.5-m (60-in.) diameter solid rocket strap-on graphite epoxy motors (GEMs) to increase its payload capacity.
The Delta IV medium+ (5,2) is similar to the medium+ (4,2), but has a 5-m–diameter payload fairing and increased upper-stage fuel capacity.
The Delta IV medium+ (5,4) is similar to the medium+ (5,2), but it uses four GEMs instead of two.
The Delta IV Heavy is similar to the medium+ (5,2), except that it uses two additional CBCs instead of using GEMs. These are strap-on boosters which are separated earlier in the flight than the center CBC.
Capacity (separated spacecraft mass) of the Delta IV Heavy:
The total mass at launch is 733 000 kg, much less than that of the Space Shuttle (2 040 000 kg).
The Delta IV entered the space launch market at a period when global capacity was already much higher than demand. Furthermore, as an unproven design it would have difficulty finding a market in commercial launches. The first launches have been paid for by the US Military involving a cost of between $140 million and $170 million.1. The first launch of the heavy rocket was on December 21 2004 after a delay due to bad weather. It is a test launch carrying a payload consisting of:
- NanoSat-2 carried to LEO - a set of two very small satellites of 24 and 21 kg - planned to orbit for one day
- DummySat - 5900 kg; planned to be carried to GEO, but due to lower than expected performance from the first stage, this payload fell short of its intended orbit.
The first launch of a valuable payload is scheduled for fall 2005, a US Defense Support Program missile warning satellite, and the second will be a classified US National Reconnaissance Office reconnaissance satellite.
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