Delta IV

The use of the Delta IV space launch vehicle will be discontinued in favor of the Atlas V that uses the Russian made RD-180 rocket to launch US national security payloads into space, United Launch Alliance (ULA) President and Chief Executive Officer Tory Bruno said 18 March 2015. Delta IV is entirely redundant to the Atlas V in terms of its performance. ULA will consolidate resources into the Atlas IV and develop a new rocket to replace the Russian made RD-180.

The 2015 National Defense Authorization Act (NDAA) prohibits the US Department of Defense from awarding or renewing contracts for launch vehicles that use Russian-made rockets. Under the NDAA, the current ULA contract to use the Russian RD-180 rocket runs until 2019 and will not be affected. To meet the new government requirement to replace the RD-180, ULA has developed two partnerships with the US space companies Blue Origin and Aerojet Rocketdyne. ULA will decide which of the two forthcoming rockets to use based on when each model can be ready.

There could be a two to five year gap, however, if a US-made rocket is not developed before the NDAA clause goes into effect, according to the US Air Force. To fill the gap, the US government has sought to license the US company Space X to be an alternative provider of national security payload launches. Space X argues it can compete with ULA by developing a cheaper rocket before the United States runs out of RD-180s.

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..

The Delta IV family of launch vehicles combines design simplicity, manufacturing efficiency, and streamlined mission and vehicle integration to meet customer requirements to launch high-priority U.S. Air Force (USAF), National Reconnaissance Office (NRO), NASA, and commercial payloads to orbit.

With operational launch pads on both coasts—Space Launch Complex-37 at Cape Canaveral Air Force Station, Fla., and Space Launch Complex-6 at Vandenberg Air Force Base, Calif.—every Delta IV configuration is available to service the requirements of current and future satellite programs.

The Delta IV launch system is available in five configurations: the Delta IV Medium (Delta IV M), three variants of the Delta IV Medium-Plus (Delta IV M+), and the Delta IV Heavy (Delta IV H). Each configuration is comprised of a common booster core (CBC), a cryogenic upper stage and either a 4-m-diameter or 5-m-diameter payload fairing (PLF).

There are three variants of Delta IV M+ configuration. The Delta IV M+(4,2) uses two strap-on solid rocket motors (SRMs) to augment the first-stage CBC and a 4-m diameter PLF. The Delta IV M+(5,2) and Delta IV M+(5,4) have two and four SRMs, respectively, and 5-m-diameter PLF.

The Delta IV Heavy employs two additional CBCs as strap-on liquid rocket boosters (LRBs) to augment the first-stage CBC and 5-m-diameter PLF.

Propulsion

Main Engine

Design simplicity, demonstrated capability and cost-efficiency define the RS-68A, the main engine for the Delta IV. Designed and manufactured by Pratt & Whitney Rocketdyne, the throttleable RS-68A engine is the largest existing hydrogen-burning engine. Conceived using a simplified design approach, the resulting engine requires 80 percent fewer parts than the Space Shuttle main engine, is lower risk, has reduced development and production costs and has inherently reliable operation.

Nominal Thrust (sea level): 702,000 lbs

Specific Impulse (sea level): 362 seconds
Length: 204 in
Weight: 14,876 lbs
Fuel/Oxidizer: Liquid Hydrogen/Liquid Oxygen

Solid Rocket Motors

For missions requiring additional thrust at liftoff, the Delta IV M+ configurations use either two or four Alliant Techsystems-manufactured solid rocket motors (SRM). Separation is accomplished by initiating ordnance thrusters that provide a radial thrust to jettison the expended SRMs away from the first stage.

Peak Vacuum Thrust: 280,000 lbf
Specific Impulse: 275.2 seconds
Length: 636 in
Maximum Diameter: 60 in
Weight: 74,500 lbs
Nominal Burn Time: 90 seconds

Second Stage

Both the Atlas and the Delta IV second stages rely on the RL10 propulsion system to power their second stages. Logging an impressive record of more than 385 successful flights and nearly 700 firings in space, RL10 engines, manufactured by Pratt & Whitney Rocketdyne, harness the power of high-energy liquid hydrogen and boast a precision control system and restart capability to accurately place critical payloads into orbit.

The Delta IV employs the RL10B-2 with the world’s largest carbon-carbon extendible nozzle.

Nominal Thrust: 24,750 lbs
Specific Impulse: 465.5 seconds
Fuel/Oxidizer: Liquid Hydrogen/Liquid Oxygen
Length: 86.5 in (stowed); 163.5 in (deployed)
Diameter (nozzle extension): 84.5 in
Weight: 664 lbs

Payload Fairings

The fairings protect the payload from encapsulation through the boost phase of flight.

The 4-m-diameter by 11.7-m (38.5-ft)-long fairing is a composite bisector design and is used on the Delta IV M and M+(4,2).

The 5-m-diameter composite fairing also is a bi-sector design and comes in two standard lengths. The 14.3 m (47 ft) fairing is used on the Delta IV M+(5,2) and M+(5,4). The 19.1 m (62.7 ft) fairing is used on the Delta IV Heavy.

The 5-m metallic trisector fairing (the baseline for heritage government programs) is a modified version of the flight-proven Titan IV aluminum isogrid fairing designed and manufactured by The Boeing Company.

All PLFs are configured for off-pad payload encapsulation, which enhances payload safety and security and minimizes on-pad time.

The Delta 4 Medium has completed its final launch for United Launch Alliance, delivering a GPS III satellite into orbit. "We don't see any specific payloads that would require the Delta 4 Medium that we can't fly on an Atlas 5," ULA's Gary Wentz said 22 August 2019.

Performance