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The Delta IV is a family of rockets designed by Boeing IDS and built in its purpose-built facility in Decatur, Alabama with final assembly at the launch site. The rockets were designed for the United States Air Force Evolved Expendable Launch Vehicle (EELV) program and commercial satellite business. 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 U.S. military.

Vehicle Description

The first stage of a Delta IV consists of one, or in the Heavy variety three, Common Booster Cores (CBC) 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 first-stage tanks are based on the construction methods of the upper stage tanks originally developed for the Delta III, but enlarged to five meters diameter. As the name implies, the CBC is used across the entire Delta IV range, allowing the launch vehicle to accommodate different payloads with minimal changes.

The RS-68 is the first large, liquid-fueled rocket engine designed in the U.S. since the Space Shuttle Main Engine (SSME) in the 1970s. The primary goal for the RS-68 was to reduce cost versus the SSME. Some sacrifice in chamber pressure was made, hurting efficiency; however, development time, part count, and assembly labor were reduced to a fraction of the SSME, despite the RS-68 being a noticeably larger engine. The RS-68 uses channel-wall construction in the thrust chamber and upper nozzle. This method, pioneered in the Soviet Union, uses inner and outer skins brazed to a middle separator to form cooling channels. This is much simpler than tube-walled nozzles, in which hundreds of tubes are bent and brazed together. The lower nozzle, where heat transfer is lower, uses an ablative layer, which burns away as the engine runs to dissipate heat. This method is heavier, but is much simpler to construct. The RS-68 is also capable of deep throttling like its competitors. Typically, the RS-68 runs at 102% rated thrust for the first few minutes of flight, and then throttles down to 58% rated thrust before main engine cutoff.*

The Redundant Inertial Flight Control Assembly (RIFCA) guidance system used on the Delta IV is common to that carried on the Delta II, although the software is different because of the differences between the Delta II and Delta IV.

The upper stage of the Delta IV is nearly identical to that of the Delta III. It is powered by a Pratt & Whitney RL-10B2 engine.

Variants

The Delta IV Medium is the most basic Delta IV. It features a single CBC and a modified Delta III second stage, with 4-meter liquid hydrogen and liquid oxygen tanks and a 4-meter payload fairing derived from the Delta III fairing. The Delta IV Medium 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 Alliant-built 1.5-m (60-in) diameter solid rocket strap-on Graphite-Epoxy Motors (GEM-60s) to increase its payload capacity to 5,845 kg (12,890 lb) to GTO.

The Delta IV Medium+ (5,2) is similar to the Medium+ (4,2), but has a 5-m–diameter payload fairing for larger payloads and a modified second stage with a 5-meter liquid hydrogen tank and stretched liquid oxygen tank. The Medium+ (5,2) can launch 4,640 kg (10,230 lb) to GTO.

The Delta IV Medium+ (5,4) is similar to the Medium+ (5,2), but uses four GEM-60s instead of two, enabling it to lift 6,565 kg (14,475 lb) to GTO.

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. The Delta IV Heavy also features a stretched 5-meter composite payload fairing, although an aluminum fairing derived from the Titan IV is also available. *

Capacity (separated spacecraft mass) of the Delta IV Heavy:

The Heavy's total mass at launch is approximately 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 has had difficulty finding a market in commercial launches. The first launches have been paid for by the U.S. Military, with a cost of between $140 million and $170 million.1.

Comparable rockets: Atlas V - Ariane 5 - Chang Zheng 5 - Angara

Launch Sites

The Delta IV booster utilizes both East and West coast launch facilities. Space Launch Complex 37 (SLC-37) at the Cape Canaveral Air Force Station, site of several unmanned Saturn-1 and -1B launches is used in the East. Polar-orbit launches use Vandenberg Air Force Base's SLC-6 pad, which was originally intended for the cancelled Air Force MOL space station, and later for polar orbit Space Shuttle flights (neither mission ever actually launched from SLC-6).

Launch History

  • DSCS III-A3 (Defense Satellite Communications System) was the second launch, also from Cape Canaveral on 10 March 2003. The Medium placed the U.S. Air Force's satelite into GTO.

  • DSCS III-B6 was the third launch on 29 August 2003 on a Medium. This was the last of the DSCS satellites, into GTO from Cape Canaveral.

  • Heavy Demo was the first launch of the Heavy variant on 21 December 2004 after significant delays due to bad weather. Due to cavitation in the propellant lines, sensors registered depletion of propellant. The booster, and later core engines shut down prematurely, even though sufficient propellant remained to continue the burn as scheduled. The second stage attempted to compensate for the under-burn, until it ran out of propellant. This flight was a test launch carrying a payload consisting of:
    • DemoSat — 6020 kg; an alumunum cylinder filled with 60 brass rods — 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.
    • NanoSat-2, carried to low Earth orbit (LEO) — a set of two very small satellites of 24 and 21 kg, nicknamed Sparky and Ralphie — planned to orbit for one day. Given the under-burn, the two most likely did not reached stable orbit. *

  • GOES-N, a weather satellite for NOAA and NASA, was launched aboard a Medium+ (4,2) from Cape Canaveral on 24 May 2006. The launch had been delayed several times due to technical issues and a union strike.

  • NROL-22, a classified satellite for the U.S. National Reconnaissance Office (NRO) was launched aboard a Medium+ (4,2) on 27 June, 2006. This was the first Delta IV launched from SLC-6 at Vandenberg Air Force Base (VAFB).

  • DSP-23 is the first launch of a valuable payload aboard a Heavy vehicle. The main payload is the 23rd and final Defense Support Program missile-warning satellite. Launch will take place from Cape Canaveral and is curently scheduled for 31 January 2007.

  • NROL-26 will carry a classified U.S. NRO satellite on a Heavy. Launch date is currently to be determined.

List Updated: 12 July 2006.

- bgcolor="#FFDEAD" 		Date Type Serial-No. Startplace Payload Kind of Payload Orbit Outcome
November 20 2002 M+(4,2) D-293 CC LC37B Eutelsat W5 Commercial communications satellite GTO Success
March 11 2003 Medium D-296 CC LC37B DSCS-3 A3 (USA 167) Military communications satellite GTO Success
August 29 2003 Medium D-301 CC LC37B DSCS-3 B6 (USA 170) Military communications satellite GTO Success
December 21 2004 Heavy D-310 CC LC37B DemoSat / 3CS 1 / 3CS 2 Demonstration payload Nearly GTO Planned Partial success, only DemoSat reach orbit
May 24 2006 M+(4,2) D-315 CC LC37B GOES-N Weather Satellite High pergee GTO Success
June 27 2006 M+(4,2) D-317 VAFB SLC-6 NROL-22 U.S. National Reconnaissance Office HEO Success

Planed Launches

List Date: July 12 2006

- bgcolor="#FFDEAD" 		Date and Time UTC Type Serial-No. Startplace Payload Kind of Payload Orbit Outcome
November 2006 Medium ? VAFB SLC-6 DMSP 17 Millitary wether satellite on Polar Orbit SSO
January 31, 2007 Heavy ? CC SLC-37B DSP 23 Missile Warning Satellite GSO Second Delta IV Heavy launch
2007 ? M+(5,2) ? VAFB SLC-6 NRO L-25 Spy satellite of the NRO Highly Elliptical Orbit (HEO)
2007 ? Heavy ? CC SLC-37B NRO L-26 Spy satellite of the NRO GSO or HEO
Planned Launches Translated from the german Wikipedia

Upgrade options

Possible future upgrades for the Delta IV include adding extra strap-on solid motors to boost capacity, higher-thrust main engines, lighter materials, higher-thrust second stages, and more (up to six) strap-on CBCs. *

NASA originally had plans to use the Delta IV Heavy for the Crew Exploration Vehicle, the replacement for the Space Shuttle. But with the change of the CEV from a winged or lifting body spacecraft to an Apollo-like capsule and a new launch vehicle based on Space Shuttle components, the only component from the Delta IV that NASA would adopt is the RS-68 engine that would be used to power the new cryogenically-fueled Ares V rocket.

External links

Space launch vehicles | Decatur, Alabama

Delta IV | Delta IV | Delta-4 | Delta IV

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Delta IV rocket".

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