Delta IV rocket

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This article is about the rocket. For the submarine see Delta class submarine.

Fact sheet
Delta IV (Delta 9000)
Delta IV Medium launch carrying DSCS III-B6
Function	Orbital launch vehicle
Manufacturer	Boeing IDS United Launch Alliance
Country of origin	United States
Size
Height	63 - 77.2 m (206 - 253.2 ft)
Diameter	5 m (16.4 ft)
Mass	249,500 - 733,400 kg (550,000 - 1,616,800 lb)
Stages	2
Capacity
Payload to LEO	8,600 - 25,800 kg (18,900 - 56,800 lb)
Payload to GTO	3,900 - 10,843 kg (8,500 - 23,904 lb)
Launch History
Status	Active
Launch sites	SLC-37B, Cape Canaveral SLC-6, Vandenberg AFB
Total launches	8 Medium: 3 Medium+ (4,2): 3 Heavy: 2
Successes	7 Medium: 3 Medium+ (4,2): 3 Heavy: 1
Partial failures	1 (Heavy)
Maiden flight	20 November 2002
Boosters (Medium+ Variants) - GEM 60
N^o boosters	Medium: 0; M+4,2: 2; M+5: 2 or 4
Engines	1 Solid
Thrust	826.6 kN (185,817 lb_f)
Specific impulse	275 sec
Burn time	90 seconds
Fuel	Solid
Boosters (Heavy) - Delta IV CBC
N^o boosters	2
Engines	1 RS-68
Thrust	3,312.8 kN (744,737 lb_f)
Specific impulse	410 sec
Burn time	249 seconds
Fuel	LH2/LOX
First Stage - Delta IV CBC
Engines	1 RS-68
Thrust	3,312.8 kN (744,737 lb_f)
Specific impulse	410 sec
Burn time	259 seconds
Fuel	LH2/LOX
Second Stage
Engines	1 RL-10B-2
Thrust	110 kN (24,740 lb_f)
Specific impulse	462 sec
Burn time	850 - 1,125 seconds
Fuel	LH2/LOX

The Delta IV is a family of Delta rockets designed by Boeing's Integrated Defense Systems division and built in United Launch Alliance's facility in Decatur, Alabama with final assembly at the launch site by United Launch Alliance.^[1] The rockets were designed for the United States Air Force Evolved Expendable Launch Vehicle (EELV) program and commercial satellite business, and are intended to reduce the cost and effort needed to launch payloads into orbit. The Delta IV is available in five versions: Medium, Medium+ (4,2), Medium+ (5,2), Medium+ (5,4), and Heavy, which are tailored to suit specific payload size and weight ranges. The Delta IV is primarily designed to satisfy the needs of the U.S. military.

The rockets are assembled at the Horizontal Integration Facility and launched from LC-37B at Cape Canaveral, and SLC-6 at Vandenberg AFB.

1 Vehicle description
2 Variants
- 2.1 Future variants
3 Launch sites
4 Vehicle processing
5 Delta IV launches
- 5.1 Notable past launches
- 5.2 Planned launches
6 See also
7 External links
8 References

[edit] 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 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 and specific impulse was made, hurting efficiency; however, development time, part count, total cost, and assembly labor were reduced to a fraction of the SSME, despite the RS-68's significantly larger size. 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.^[2] On the Heavy variant, the core CBC's engine throttles down to 58% rated thrust around 50 seconds after liftoff, while the strap-on CBCs remain at 102%. This allows the core CBC to conserve propellant and burn longer. After the strap-on CBCs separate, the core CBC's engine throttles back up to 102%, until main engine cutoff, before which it throttles back down to 58%.^[3]

The RS-68 engine is mounted to the lower thrust structure of the vehicle by a four-legged (quadrapod) thrust frame, and enclosed in a protective composite conical thermal shield. Above the thrust structure is an aluminum isogrid (a grid pattern machined out of the inside of the tank to reduce weight) liquid hydrogen tank, followed by a composite cylinder called the centerbody, an aluminum isogrid liquid oxygen tank, and a forward skirt. Along the back of the CBC is a cable tunnel to hold electrical and signal lines, and a tube to carry the liquid oxygen to the RS-68 from the tank. The CBC is of a constant, 5-meter, diameter.

The L-3 Communications 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 RIFCA features six ring laser gyroscopes and accelerometers each, to provide a higher degree of reliability.^[4]

The upper stage of the Delta IV is nearly identical to that of the Delta III, however the tanks are either stretched (in 4-meter variants), or have a larger diameter (5-meter variants). The second stage is powered by a Pratt & Whitney RL-10B2 engine, which features an extendable carbon-carbon nozzle to improve specific impulse. Depending on variant, two different interstages are used to mate the first and second stages. A tapering interstage which narrows down from 5-meters to 4-meters in diameter is used on 4-meter variants, where a cylindrical interstage is used on 5-meter variants. Both interstages are built from composites.

To encapsulate the satellite payload, a variety of different payload fairings are available. A stretched Delta III 4-meter payload fairing is used on 4-meter variants, where an enlarged, 5-meter fairing is used on 5-meter variants. A longer version of the latter is standard on the Heavy variant, and a 5-meter, aluminum isogrid payload fairing is also available for the Heavy.

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, and the cost to launch a Delta IV is somewhat higher than that for competing vehicles. In 2003, Boeing pulled the Delta IV from the commercial market, citing low demand and high costs. In 2005, Boeing stated that it may return the Delta IV to commercial service; however as of 2006 no further announcements have been made regarding this.^[5] All but one of the first launches have been paid for by the U.S. Government, with a cost of between $140 million and $170 million.

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

[edit] Variants

The Delta IV Medium (Delta 9040) 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) (Delta 9240) 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 payload capacity to 5,845 kg (12,890 lb) to GTO.

The Delta IV Medium+ (5,2) (Delta 9250) 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. Because of the extra weight of the larger payload fairing and second stage, the Medium+ (5,2) can launch 4,640 kg (10,230 lb) to GTO, less than the Medium+ (4,2).

The Delta IV Medium+ (5,4) (Delta 9450) 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 (Delta 9250H) 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.^[6] An aluminum trisector (3 part) fairing derived from the Titan IV is also available.^[7] This was first used on the DSP-23 flight.

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

geosynchronous transfer orbit (GTO) 13,130 kg (28,950 lb), more than any other currently available launch vehicle
geosynchronous orbit (GEO) 6,275 kg
escape orbit 9,306 kg
C₃ performance of 30 km²s⁻²: 5,228 kg
C₃ performance of 60 km²s⁻²: 2,521 kg

The Heavy's total mass at launch is approximately 733,000 kg, much less than that of the Space Shuttle (2,040,000 kg).

During the Delta IV's development, a Small variant was considered. This would have featured the Delta II second stage, an optional Thiokol Star 48B third stage, and the Delta II payload fairing, all atop a single CBC.^[8] The Small variant was dropped by 1999.^[9]^[10] This was probably because the Delta II has a similar payload capability.

[edit] Future variants

Delta IV evolution (US Govt)

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, more (up to six) strap-on CBCs, and a cryogenic propellant cross feed from strap on boosters to the common core. These modifications could potentially increase the mass of the payload delivered to LEO to 100 tonnes.^[6]

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.

The possibility of an extra-heavy variant was indicated in a 2006 RAND Corporation study of national security launch requirements out to 2020,^[11] which noted, "...only the Delta IV Heavy has the performance to lift the ten NSS launch requirements that require a heavy-lift capability... the production capacity for Delta IV, with one possible exception, can satisfy the entire projected NSS launch demand. The exception involves the requirement to increase the Delta IV Heavy lift capability to accommodate a single NRO (National Reconnaissance Office) payload. The best solution to this requirement is currently under study."

[edit] Launch sites

First Delta IV Heavy with three CBCs prior to launch

Delta IV launches occur from either of two rocket launch sites. On the East coast of the United States, Launch Complex 37 (LC-37) at the Cape Canaveral Air Force Station -- site of several unmanned Saturn I and -IB launches -- is used. On the West coast, polar-orbit and high-inclination launches use Vandenberg Air Force Base's Space Launch Complex 6 (SLC-6) pad. This pad was originally intended for the cancelled Air Force MOL space station, and later for polar orbit Space Shuttle flights, but neither were ever actually launched from SLC-6.

Launch facilities at both sites are similar. At the pad is a Mobile Service Tower (MST), which provides service access to the rocket and protection from the weather. There is a crane at the top of the MST, which allows the payload and GEM-60 solid motors to be attached to the vehicle. The MST is rolled away from the rocket several hours before launch. At Vandenberg, the launch pad also has a Mobile Assembly Shelter (MAS), which completely encloses the vehicle; at CCAFS, the vehicle is partly exposed near its bottom.

Beside the vehicle is a Fixed Umbilical Tower (FUT), which has two (VAFB) or three (CCAFS) swing arms. These arms carry electrical, hydraulic, environmental control, and other support functions to the vehicle through umbilical lines. The swing arms retract at T-0 seconds to prevent them from hitting the vehicle.

Under the vehicle is a Launch Table, with six Tail Service Masts (TSMs), two for each CBC. The Launch Table supports the vehicle on the pad, and the TSMs provide further support and fueling functions for the CBCs. The vehicle is mounted to the Launch Table by a Launch Mate Unit (LMU), which is attached to the vehicle by bolts that sever at launch. Behind the Launch Table is a Fixed Pad Erector (FPE), which uses two long-stroke hydraulic pistons to raise the vehicle to the vertical position after being rolled to the pad from the Horizontal Integration Facility (HIF). Beneath the Launch Table is a flame duct, which deflects the rocket's exhaust away from the rocket or facilities.

The Horizontal Integration Facility (HIF) is situated some distance from the pad. It is a large building that allows the Delta IV CBCs and second stages to be mated and tested before they are moved to the pad.

Movement of the Delta IVs among the various facilities at the pad is facilitated by Elevating Platform Transporters (EPTs). These rubber-tired vehicles can be powered by either diesel engines or electric power. Diesel EPTs are used for moving the vehicles from the HIF to the pad, while electric EPTs are used in the HIF, where precision of movement is important.^[12]

[edit] Vehicle processing

Delta IV 4-Meter Second Stage

The Delta IVs are assembled using a process that Boeing claims reduces cost and expensive on-pad time. The CBCs are built in Boeing's factory in Decatur, Alabama. They are then loaded onto the M/V Delta Mariner, a roll-on/roll-off cargo vessel, and shipped to either launch pad. There, they are offloaded and rolled into a Horizontal Integration Facility (HIF), where they are mated with the second stages, which were shipped separately to the pad on the Delta Mariner. Also, in the HIF, the three CBCs of Heavy variant are mated to each other.

Various tests are performed, and then the vehicle is rolled horizontally to the pad, where the Fixed Pad Erector (FPE) is used to raise the vehicle to the vertical position, inside the MST. At this time, the GEM-60 solid motors, if any are required, are rolled to the pad and attached to the vehicle. After further testing, the payload (which has already been enclosed in its fairing) is transported to the pad, hoisted into the MST by a crane, and attached to the vehicle. Finally, on launch day, the MST is rolled away from the vehicle, and the vehicle is ready for launch.^[13]

[edit] Delta IV launches

For more details on this topic, see List of Delta IV launches.

GOES-N launch on a Medium+ (4,2)

[edit] Notable past launches

The first payload launched with a Delta IV was the Eutelsat W5 communications satellite. The launch vehicle was a Medium+ (4,2) variant, launched from Cape Canaveral. It carried the communications satellite into geostationary transfer orbit (GTO) on November 20, 2002.

Heavy Demo was the first launch of the Heavy variant in Dec. 2004 after significant delays due to bad weather. Due to cavitation in the propellant lines, sensors registered depletion of propellant. The strap-on, and later core CBC 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 aluminum cylinder filled with 60 brass rods — planned to be carried to GEO; however due to the sensor faults, the satellite did not reach this 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 reach a stable orbit.^[14]

A unique aerial view of NROL-22 launch from SLC-6 (USAF photo/Staff Sgt. Quinton Russ)

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

DSP-23 was the first launch of a valuable payload aboard a Heavy vehicle. This was also be the first Delta IV launch contracted by the United Launch Alliance, a joint venture between Boeing and Lockheed Martin. The main payload was the 23rd and final Defense Support Program missile-warning satellite, DSP-23. Launch, from Cape Canaveral occurred at 01:50:00 GMT on 11 November 2007 (8:50 EST, November 10, 2007).^[15]

[edit] Planned launches

The GOES-O mission will carry a weather satellite for NOAA and NASA on a Medium+ (4,2) from Cape Canaveral. Launch is currently scheduled for 2008-07-20.^[16]^[17]