Delta IV


Delta IV is a family of expendable launch vehicles designed to launch payloads into orbit for the United States Air Force Evolved Expendable Launch Vehicle (EELV) program and commercial satellite business.

Delta IV Picture

Delta IV uses rockets designed by Boeing’s Integrated Defense Systems division and built in the United Launch Alliance (ULA) facility in Decatur, Alabama. Final assembly is completed at the launch site by ULA. United Launch Alliance (ULA) is a joint venture between Boeing and Lockheed Martin.

Rocket Design

The Delta IV cons is of the Common Booster Core (CBC) powered by a Pratt and Whitney Rocketdyne RS-68 engine, a Delta Cryogenic Second Stage (DCSS) and off pad horizontal vehicle integration.

Delta IV rockets are available in five versions:

1.  Delta IV Medium: uses a CBC first stage and a 4-m diameter DCSS.

2.  Delta IV Medium+ (4,2):  uses 2 strap-on solid rocket motors (SRMs) to augment the first-stage CBC and a 4-m diameter DCSS and PLF.

3.  Delta IV Medium+ (5,2): uses two SRMs and 5-m diameter DCSS and PLF.

4.  Delta IV Medium+ (5,4): uses four SRMs and 5-m diameter DCSS and PLF.

5.  Delta IV Heavy:  uses two strap-on CBC cores with a 5-m DCSS and PLF.

Delta IV Rocket Family Picture


Delta IV First Stage consists of one Common Booster Core (CBC) or three Common Booster Cores in the Heavy version. The Common Booster Core is powered by a RS-68 rocket engine, uses liquid hydrogen and liquid oxygen as propellants. It  is 40.8 metres (134 ft) long, has a diameter of 5.1 metres (17 ft).

Delta IV Medium+ models have two or four GEM-60 60-inch diameter solid boosters.

Specs: GEM-60 solid boosters.

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

Delta IV Second Stage consists of a Delta Cryogenic Second Stage (DCSS) which is based on the Delta III upper stage, but with increased propellant capacity. The 4 m (13.1 ft) version uses lengthened propellant tanks, while the 5 m version has a 5 m diameter liquid hydrogen tank and a further lengthened liquid oxygen tank. The second stage is powered by a single Pratt & Whitney RL10B-2 engine.

The stage consists of a cylindrical LH2 tank structurally separated from an oblate spheroid LOX tank. The LH2 tank cylinder carries payload launch loads, while the LOX tank and engine are suspended below within the rocket’s inter-stage.

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 uses the RL10B-2 with the world’s largest carbon-carbon extendible nozzle.

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

Building Parts and Assembly

The Delta IV’s main components are designed by Boeing’s Defense, Space & Security division and built in the United Launch Alliance (ULA) facility in Decatur, Alabama, USA.

The Common Booster Core’s are manufactured in Decatur, Alabama and then transported by the M/V Delta Mariner cargo ship to either Cape Canaveral Air Force Station or Vandenberg Air Force Base. Final assembly for the rockets is completed at the launch sites by ULA.

Launch Sites

There are two operational launch pads on both coasts in the USA: Space Launch Complex-37 at Cape Canaveral Air Force Station, Florida and Space Launch Complex-6 (SLC-6) at Vandenberg Air Force Base, California.

Delta IV Heavy

The Delta IV Heavy uses two additional Common Booster Cores (CBCs) as liquid rocket boosters instead of the GEM-60solid rocket motors used by the Delta IV Medium+ versions. At lift-off, all three cores operate at full thrust and 44 seconds later the center core throttles down to 55% to conserve fuel until booster separation. The boosters burn out at 242 seconds after launch and are separated as the core booster throttles back up to full thrust. The core burns out 86 seconds later and the second stage completes the ascent to orbit.

Delta IV Heavy was primarily designed to satisfy the needs of the USA’s military.

The Delta IV Heavy is the largest type of the Delta IV family and the world’s highest capacity rocket currently in operation (June 2016). It was first launched in 2004. Features a stretched 5-meter composite payload fairing.

Delta IV Heavy Payload Capacity:

Ranges from:
– 28,000kg to Low Earth Orbit,
– 25,000kg to the International Station
– 6,700kg to Geosynchronous Orbit (GEO)
– 10,000kg to Lunar Transfer Orbit (LTO)
– 8,000 kg to Mars Transfer Orbit

The total mass of the Delta IV Heavy at launch is about 733,000 kg (1,616,000 lb). In comparison the Saturn V total mass at launch (used in the Apollo program) was 2,970,000 kg (6,550,000 lb).


As part of the Air Force’s EELV (Evolved Expendable Launch Vehicle) program, McDonnell Douglas/Boeing proposed Delta IV. As the program implies, many components and technologies were borrowed from existing launchers. Both Boeing and Lockheed Martin were contracted to produce their EELV designs.

  • First stage changed to liquid hydrogen fuel. Tank technologies derived from Delta III upper stage, but widened to 5 meters.
  • Kerosene engine replaced with RS-68 Rocket Engine, the first new, large liquid-fueled rocket engine designed in the US since the Space Shuttle Main Engine (SSME) in the 1970s. Designed for low cost; has lower chamber pressure and efficiency than the SSME, and a much simpler nozzle. Thrust chamber and upper nozzle is a channel-wall design, pioneered by Soviet engines. Lower nozzle is ablatively cooled.
  • Second stage and fairing taken from the Delta III in smaller (Delta IV Medium) models; widened to 5 meters in Medium+ and Heavy models.
  • Medium+ models have two or four GEM-60 60-inch diameter solid boosters.
  • Revised plumbing and electric circuits eliminate need for a launch tower.

* First Static Test Firing of a Common Booster Core was conducted on 17 March 2001 and the final test of the initial programme was conducted on 6 May. Testing was conducted using Test Stand B-2 of the John C. Stennis Space Center, a facility originally constructed for testing of the first stages of Saturn V rockets during the 1960s.

* First launch of a Common Booster Core was the maiden flight of the Delta IV, which was launched from Space Launch Complex 37B at the Cape Canaveral Air Force Station on 20 November 2002.

*   In 2002, the RS-68 became the first large liquid-propellant rocket engine designed in the USA since the Space Shuttle Main Engine (SSME).

*    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 20 November, 2002.

*  First flight of the Delta IV Heavy was on 21 December 2004 and carried a boilerplate payload and was a partial failure. On this flight all three Common Booster Cores malfunctioned, cutting off prematurely due to cavitation in their oxidiser lines and resulting in the rocket reaching a lower orbit than that which had been planned. In response to the failure, additional pressure valves were installed on future launches.

The payloads were:
(i) 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.

(ii) 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.

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

*   First successful launch from Space Launch Complex 37 (SLC-37) at the Cape Canaveral Air Force Station on 10 November, 2007. It carried the DSP-23 satellite: the 23rd and final Defense Support Program missile-warning satellite.

*   First Delta IV Heavy launch for the National Reconnaissance Office (NRO) carried the USA 202 (NROL-26), a classified reconnaissance satellite. It was launched on 18 January, 2009 from Space Launch Complex 37B at the Cape Canaveral Air Force Station, Florida. This was the third flight of a Delta IV Heavy rocket.

*  First flight of a Delta IV Heavy from Vandenberg carried NROL-49 satellite. It was launched on 20 January 20, 2011.

*    First uncrewed test flight, EFT-1 launched the Orion spacecraft (Orion Multi-Purpose Crew Vehicle) on a Delta IV Heavy on 5 December, 2014 from Space Launch Complex 37B at Cape Canaveral Air Force Station.

*    In March 2015, ULA announced plans to phase out all Delta IV launchers except the Delta IV Heavy by 2018. The Delta IV will be largely replaced by the Atlas V.

*   Delta IV Heavy is scheduled to launch Solar Probe Plus mission in 2018. This Delta IV Heavy launch will implement the Star 48BV third stage (Delta 9255H), the first use of a third stage on a Delta IV.


Vulcan rocket is planned to replace the Atlas V and Delta IV rockets. Vulcan is projected to enter service by 2019, using the Blue Origin BE-4 methane-fuelled rocket engine.

Did you know?

–   Evolved Expendable Launch Vehicle (EELV) is an expendable launch system program of the United States Air Force (USAF). The program began in the 1990s with the goal of making government space launches more affordable and reliable and to assure access to space for Department of Defense and other US government payloads. This resulted in the development of two launch systems: Delta IV and Atlas V.

–   The Delta IV-Heavy utilizes the same configuration as the Delta IV-M (no strap on Aerojet boosters) but with two additional Common Booster Cores.

–    Unlike many first-stage rocket engines, which use solid fuel or kerosene, the RS-68 engines burn liquid hydrogen and liquid oxygen.

–   United Launch Alliance (ULA) is a joint venture between Boeing and Lockheed Martin.

– The Delta Cryogenic Second Stage (DCSS) is a family of cryogenic rocket stages used on the Delta III & Delta IV rockets and which is planned to be used on the Block I Space Launch System.

–  Current Launch Vehicles that are similar to Delta IV include: Angara (Russia), Ariane 5 (ESA), Atlas V (USA), Proton-M (Russia), Long March 5 (China), Space Launch System (USA) and Falcon Heavy (USA). Retired Launch Vehicles: Titan IV (USA).

Delta IV Links:

Delta IV Heavy – RS-68A Upgrade:
Delta IV – United Launch Alliance: by United Launch Alliance (ULA).
Delta IV Data Sheet – Space Launch Report:
Delta IV Heavy: by Encyclopedia Astronautica
U.S. Air Force Set to Launch 23rd and Final Northrop Grumman-Built Defense Support Program Satellite on November 10:

Any comments or suggestions, then click on Contact Info.