Delta IV was a group of five expendable launch systems in the Delta rocket family. It flew 45 missions from 2002 to 2024. Originally designed by Boeing's Defense,Space and Security division for the Evolved Expendable Launch Vehicle (EELV) program,the Delta IV became a United Launch Alliance (ULA) product in 2006. The Delta IV was primarily a launch vehicle for United States Air Force (USAF) military payloads,but was also used to launch a number of United States government non-military payloads and a single commercial satellite.
The Delta IV had two main versions which allowed the family to cover a range of payload sizes and masses:the Medium (which had four configurations) and Heavy. The final flight of Medium occurred in 2019. The final flight of Heavy was in April 2024.
The latest evolutionary development of the Delta rocket family,Delta IV was introduced to meet the requirements of the United States Air Force's (USAF) Evolved Expendable Launch Vehicle (EELV,now National Security Space Launch (NSSL)) program. While the Delta IV retains the name of the Delta family of rockets,major changes were incorporated. Perhaps the most significant change was the switch from kerosene to liquid hydrogen fuel,with new tankage and a new engine required.[6][7]
During the Delta IV's development,a small variant was considered. This would have featured the Delta II second stage,an optional ThiokolStar 48B third stage,and the Delta II payload fairing,all atop a single Common Booster Core (CBC).[8] The Small variant was dropped by 1999.[9][10]
The L3 Technologies Redundant Inertial Flight Control Assembly (RIFCA) guidance system originally used on the Delta IV was common to that carried on the Delta II,although the software was different because of the differences between the Delta II and Delta IV. The RIFCA featured six ring laser gyroscopes and accelerometers each,to provide a higher degree of reliability.[12]
Boeing initially intended to market Delta IV commercial launch services. However,the Delta IV entered the space launch market when global capacity was already much higher than demand. Furthermore,as an unproven design it had difficulty finding a market in commercial launches,and Delta IV launch costs are higher than comparable vehicles of the same era. In 2003,Boeing pulled the Delta IV from the commercial market,citing low demand and high costs. In 2005,Boeing stated that it sought to return the Delta IV to commercial service.[13]
As of 2009,the USAF funded Delta IV EELV engineering,integration,and infrastructure work through contracts with Boeing Launch Services (BLS). On 8 August 2008,the USAF Space and Missile Systems Center increased the "cost plus award fee" contract with BLS for US$1.656 billion to extend the period of performance through the 30 September 2008 (FY09). In addition,a US$557.1 million option was added to cover FY10.[14]
In February 2010,naturalized citizen Dongfan Chung,an engineer working with Boeing,was the first person convicted under the Economic Espionage Act of 1996. Chung passed on classified information on designs including the Delta IV rocket to China and was sentenced to 15 years.[15]
In March 2015,ULA announced plans to phase out the Delta IV Medium by 2018.[16]
With the exception of the first launch,which carried the Eutelsat W5 commercial communications satellite,all Delta IV launches have been paid for by the US government. In 2015,ULA stated that a Delta IV Heavy is sold for nearly US$400 million.[17]
RS-68A booster engine upgrade
The possibility of a higher performance Delta IV was first proposed in a 2006 RAND Corporation study of national security launch requirements out to 2020. A single National Reconnaissance Office (NRO) payload required an increase in the lift capability of the Delta IV Heavy.[18] Lift capacity was increased by developing the higher-performance RS-68A engine,[19] which first flew on 29 June 2012.[20] ULA phased out the baseline RS-68 engine with the launch of Delta flight 371 on 25 March 2015. All following launches used the RS-68A,[21] and the engine's higher thrust allowed the use of a single standardized CBC design for all Delta IV Medium and M+ versions. This upgrade reduced cost and increased flexibility,since any standardized CBC could be configured for zero,two,or four solid-propellant rocket boosters. However,the new CBC led to a slight performance loss for most medium configurations.[22] The Delta IV Heavy required non-standard CBCs for the core and boosters.[23]
*Masses include a Payload Attach Fitting (240kg to 1,221kg depending on payload).[2]
Proposed upgrades that were not implemented
Possible future upgrades for the Delta IV included adding extra strap-on solid motors,higher-thrust main engines,lighter materials,higher-thrust second stages,more (up to eight) strap-on CBCs,and a cryogenic propellant cross feed from strap on boosters to the common core.[26]
A proposed upgrade to the Delta IV family was the addition of extra solid motors. The Medium+ (4,4) would have used existing mount points to pair the four GEM 60s of the M+ (5,4) with the upper stage and fairing of the (4,2). An M+ (4,4) would have had a GTO payload of 7,500kg (16,500lb),a LEO payload of 14,800kg (32,600lb),and could have been available within 36 months of the first order. It was also considered to add extra GEM 60s to the M+ (5,4),which would have required adding extra attachment points,structural changes to cope with the different flight loads,and launch pad and infrastructure changes. The Medium+ (5,6) and (5,8) would have flown with six and eight SRBs respectively,for a maximum of up to 9,200kg (20,300lb) to GTO with the M+ (5,8). The Medium+ (5,6) and (5,8) could have been available within 48 months of the first order.[29]
Successors
The Vulcan Centaur is planned to replace the Atlas V and Delta IV rockets. Vulcan Centaur had been projected to enter service by 2023,using the BE-4methane-fueled rocket engine,[30][31] but the first Vulcan launched on 8 January 2024.[32] The Atlas V is expected to stay in service for a few years after Vulcan's inaugural launch,and the Delta IV Heavy was discontinued in April 2024.[33]
Delta IV Medium
The Delta IV Medium (also referred to as 'single stick'[34][35]) was available in four configurations:Medium,Medium+ (4,2),Medium+ (5,2),and Medium+ (5,4).[36]
The Delta IV Medium (Delta 9040) was the most basic Delta IV. It featured a single CBC and a modified Delta III second stage,with 4-meter liquid hydrogen and liquid oxygen tanks (called a Delta Cryogenic Second Stage (DCSS)) and a 4-meter payload fairing. The Delta IV Medium was capable of launching 4,200kg to geostationary transfer orbit (GTO). From Cape Canaveral,GTO is 1804m/s away from GEO. The mass of fairing and payload attach fittings have been subtracted from the gross performance.[7]
The Delta IV Medium+ (5,2) (Delta 9250) was similar to the Medium+ (4,2),but had a 5-m–diameter DCSS and payload fairing for larger payloads. Because of the extra weight of the larger payload fairing and second stage,the Medium+ (5,2) could launch 5,072kg to GTO.[7]
The Delta IV Medium+ (5,4) (Delta 9450) was similar to the Medium+ (5,2),but used four GEM 60s instead of two,enabling it to lift 6,882kg to GTO.[7]
To encapsulate the satellite payload,a variety of different payload fairings were available. A stretched Delta III 4-meter diameter composite payload fairing was used on 4-meter Medium versions,while an enlarged,5-meter diameter composite fairing was used on 5-meter Medium versions.[37]
The Medium (4,2) version last flew on 22 August 2019,marking the retirement of the Delta IV Medium variants.[36][38]
The Delta IV Heavy (Delta 9250H) combines a 5m (16ft) diameter DCSS and payload fairing with two additional CBCs. These are strap-on boosters which are separated earlier in the flight than the center CBC. As of 2007,a longer 5 meter diameter composite fairing was standard on the Delta IV Heavy,[26] with an aluminum isogrid fairing also available. The aluminum trisector (three-part) fairing was built by Boeing and derived from a Titan IV fairing.[37] The trisector fairing was first used on the DSP-23 flight.[39] The Delta IV with the extended fairing is over 62m (203ft) tall. The last launch took place on 9 April 2024,carrying the NROL-70 satellite,marking the conclusion of the Delta rocket family.
On flights of the Medium,the RS-68 ran at 102% rated thrust for the first few minutes of flight,and then throttled down to 58% rated thrust before main engine cutoff.[40] On the Heavy,the main CBC's engine throttles down to 58% rated thrust around 50 seconds after liftoff,while the strap-on CBCs remain at 102%. This conserves propellant and allows the main CBC to burn after booster separation. After the strap-on CBCs separate,the main CBC's engine again throttles up to 102% before throttling back down to 58% prior to main engine cutoff.[41]
The RS-68 engine is mounted to the lower thrust structure of the CBC by a four-legged (quadrapod) thrust frame and enclosed in a protective composite conical thermal shield. Above the thrust structure is an aluminumisogrid (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 feedline to carry the liquid oxygen to the RS-68 from the tank. The CBC is of a constant,5m (16ft) diameter.[11]
The upper stage of the Delta IV was the Delta Cryogenic Second Stage (DCSS). The DCSS was based on the Delta III upper stage but has increased propellant capacity. Two versions have been produced:a 4m (13ft) diameter DCSS that was retired with the Delta IV Medium and a 5m (16ft) diameter DCSS that remains in service with the Delta IV Heavy. The 4 m diameter version lengthened both Delta III propellant tanks,while the 5-meter version has an extended diameter liquid hydrogen tank and a further lengthened liquid oxygen tank. Regardless of the diameter,each DCSS is powered by one RL10B-2 engine,with an extendable carbon-carbon nozzle to improve specific impulse.[42] Two different interstages are used to mate the first stage and DCSS. A tapering interstage that narrowed down from 5 m to 4 m diameter was used to mate the 4 m DCSS to the CBC,while a cylindrical interstage is used to mate the 5 m DCSS. Both interstages were built from composites and enclosed the liquid oxygen tank,with the larger liquid hydrogen tank making up part of the vehicle's outer mold line.[43][44]
Launch sites
First Delta IV Heavy with three CBCs prior to launch
Launch facilities at both sites are similar. A Horizontal Integration Facility (HIF) is situated some distance from the pad. Delta IV CBCs and second stages to be mated and tested in the HIF before they are moved to the pad.[45] The partial horizontal rocket assembly of the Delta IV is somewhat similar to the Soyuz launch vehicle,which is completely assembled horizontally. The Space Shuttles,the past Saturn launch vehicles,and the Space Launch System are assembled and rolled out to the launch pad entirely vertically.[citation needed]
Movement of the Delta IVs among the various facilities at the pad was facilitated by rubber-tired Elevating Platform Transporters (EPTs) and various transport jigs. Diesel engine 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.[45]
The basic launchpad structure includes a flame trench to direct the engine plume away from the rocket,lightning protection,and propellant storage. In the case of Delta IV,the vehicle was completed on the launch pad inside a building. This Mobile Service Tower (MST) provides service access to the rocket and protection from the weather and is rolled away from the rocket on launch day. A crane at the top of the MST lifts the encapsulated payload to the vehicle and also attached the GEM 60 solid motors for Delta IV Medium launches. 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.[45]
Beside the vehicle is a Fixed Umbilical Tower (FUT),which has two (VSFB) or three (CCAFS) swing arms. These arms carry telemetry signals,electrical power,hydraulic fluid,environmental control air flow,and other support functions to the vehicle through umbilical lines. The swing arms retract at T-0 seconds once the vehicle is committed to launch.[45]
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 used two long-stroke hydraulic pistons to raise the vehicle to the vertical position after being rolled to the pad from the HIF. Beneath the Launch Table is a flame duct,which deflects the rocket's exhaust away from the rocket or facilities.[45]
Vehicle processing
Delta IV CBCs and DCSSs are assembled at ULA's factory in Decatur,Alabama. They are then loaded onto the R/S RocketShip,a roll-on/roll-off cargo vessel,and shipped to either launch pad. There,they are offloaded and rolled into a HIF. For Delta IV Medium launches,the CBC and DCSS were mated in the HIF. For Delta IV Heavy launches,the port and starboard strap-on CBCs are also mated in the HIF.[46]
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. 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.[46]
GOES-N launch on a Medium+ (4,2)A unique aerial view of NROL-22 launch from SLC-6
The first payload launched with a Delta IV was the Eutelsat W5 communications satellite. A Medium+ (4,2) from Cape Canaveral carried the communications satellite into geostationary transfer orbit (GTO) on 20 November 2002.[citation needed]
Heavy Demo was the first launch of the Delta IV Heavy in December 2004 after significant delays due to bad weather. Due to cavitation in the propellant lines,sensors on all three CBCs registered depletion of propellant. The strap-on CBCs and then 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 shutdown and burned until it ran out of propellant. This flight was a test launch carrying a payload of:
DemoSat– 6020kg;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 21kg,nicknamed Sparky and Ralphie– planned to orbit for one day. Given the under-burn,the two most likely did not reach a stable orbit.[88]
DSP-23 was the first launch of a valuable payload aboard a Delta IV Heavy. This was also 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 on 10 November 2007.[89]
NROL-32 was a Delta IV Heavy launch,carrying a satellite for NRO. The payload is speculated to be the largest satellite sent into space. After a delay from 19 October 2010,the rocket lifted off on 21 November 2010.[91]
NROL-49 lifted off from Vandenberg AFB on 20 January 2011.[52] It was the first Delta IV Heavy mission to be launched out of Vandenberg. This mission was for the NRO and its details are classified.[92]
On 4 October 2012,a Delta IV M+ (4,2) experienced an anomaly in the upper stage's RL10B-2 engine which resulted in lower than expected thrust. While the vehicle had sufficient fuel margins to successfully place the payload,a GPS Block IIF satellite USA-239,into its targeted orbit,investigation into the glitch delayed subsequent Delta IV launches and the next Atlas V launch (AV-034) due to commonality between the engines used on both vehicles' upper stages.[93] By December 2012,ULA had determined the cause of the anomaly to be a fuel leak (into the combustion chamber[94]),and Delta IV launches resumed in May 2013. After two more successful launches,further investigation led to the delay of Delta flight 365 with the GPS IIF-5 satellite.[95] Originally scheduled to launch in October 2013,the vehicle lifted off on 21 February 2014.[96]
A Delta IV Heavy launched the Orion spacecraft on an uncrewed test flight,EFT-1,on 5 December 2014.[97] The launch was originally planned for 4 December 2014,but high winds and valve issues caused the launch to be rescheduled for 5 December 2014.[98]
On August 12,2018,another Delta IV Heavy launched the Parker Solar Probe on a mission to explore or "touch" the outer corona of the Sun.[99]
The second GPS Block III satellite was launched with the final Delta IV Medium+ (4,2) configuration rocket on 22 August 2019.[82]
The final flight from Vandenberg of the Delta IV Heavy launched the NROL-91 mission in September 2022.
The final flight from Cape Canaveral of the Delta IV Heavy and of the Delta rocket family took place in April 2024 carrying the NROL-70 mission.
The Delta rocket family was a versatile range of American rocket-powered expendable launch systems that provided space launch capability in the United States from 1960 to 2024. Japan also launched license-built derivatives from 1975 to 1992. More than 300 Delta rockets were launched with a 95% success rate. The series was phased out in favor of the Vulcan Centaur, with the Delta IV Heavy rocket's last launch occurring on April 9, 2024.
National Security Space Launch (NSSL) is a program of the United States Space Force (USSF) intended to assure access to space for United States Department of Defense and other United States government payloads. The program is managed by the Assured Access to Space Directorate (SSC/AA) of the Space Force's Space Systems Command (SSC), in partnership with the National Reconnaissance Office.
Delta III was an expendable launch vehicle made by McDonnell Douglas. Development was canceled before the vehicle became operational. The vehicle is the third generation of the Delta rocket family, developed from the highly successful Delta II to help meet the launch demand of larger satellites. While the Delta III never had a successful launch, some of the technologies developed were used in its successor, the Delta IV.
Atlas V is an expendable launch system and the fifth major version in the Atlas launch vehicle family. It was designed by Lockheed Martin and has been operated by United Launch Alliance (ULA) since 2006. It is used for DoD, NASA, and commercial payloads. It is America's longest-serving active rocket. After 87 launches, in August 2021 ULA announced that Atlas V would be retired, and all 29 remaining launches had been sold. As of July 2024, 15 launches remain. Production ceased in 2024. Other future ULA launches will use the Vulcan Centaur rocket.
The Graphite-Epoxy Motor (GEM) is a family of solid rocket boosters developed in the late 1980s and used since 1990. GEM motors are manufactured with carbon-fibre-reinforced polymer casings and a fuel consisting of HTPB-bound ammonium perchlorate composite propellant. GEM is produced by Northrop Grumman Space Systems. GEM boosters are used on the Atlas V and were previously used on the Delta II, Delta III, and Delta IV launch vehicles. A new variant, the GEM 63XL, flew as part of the Vulcan Centaur launch vehicle on 8 January 2024.
Vandenberg Space Launch Complex 6 is a launch pad and associated support infrastructure at Vandenberg Space Force Base in California. Construction at the site began in 1966, but the first launch didn't occur until 1995 due to program cancellations and subsequent repurposing efforts.
United Launch Alliance, LLC (ULA) is an American launch service provider formed in December 2006 as a joint venture between Lockheed Martin Space and Boeing Defense, Space & Security. The company designs, assembles, sells and launches rockets, but the company subcontracts out the production of rocket engines and solid rocket boosters.
Space Launch Complex 37 (SLC-37), previously Launch Complex 37 (LC-37), is a launch complex on Cape Canaveral Space Force Station, Florida. Construction began in 1959 and the site was accepted by NASA to support the Saturn I program in 1963. The complex consists of two launch pads. LC-37A has never been used, but LC-37B launched uncrewed Saturn I flights and was modified and launched Saturn IB flights, including the first (uncrewed) test of the Apollo Lunar Module in space. It was deactivated in 1972. In 2001 it was modified as the launch site for Delta IV, a launch system operated by United Launch Alliance.
The Wideband Global SATCOM system (WGS) is a high capacity United States Space Force satellite communications system planned for use in partnership by the United States Department of Defense (DoD), Canadian Department of National Defence (DND) and the Australian Department of Defence. The system is composed of the Space Segment satellites, the Terminal Segment users and the Control Segment operators.
The Delta IV Heavy was an expendable heavy-lift launch vehicle, the largest type of the Delta IV family. It was the world's third highest-capacity launch vehicle in operation at the time of its retirement in 2024, behind NASA's Space Launch System and SpaceX's Falcon Heavy and closely followed by CASC's Long March 5. It was manufactured by United Launch Alliance (ULA) and was first launched in 2004. ULA retired the Delta IV Heavy in 2024. Future ULA launches will use the new Vulcan Centaur rocket. Delta IV's final flight was on 9 April 2024.
The Delta Cryogenic Second Stage (DCSS) is a family of cryogenic-fuelled rocket stages used on the Delta III, Delta IV, and on the Space Launch System Block 1 launch vehicles. The DCSS employs a unique two-tank architecture where the cylindrical liquid hydrogen (LH2) tank carries payload launch loads and forms the upper section. An oblate spheroid tank filled with liquid oxygen (LOX) and the engine are suspended from the LH2 tank and covered by the interstage during initial launch.
USA-184, also known as NRO Launch 22 or NROL-22, is an American signals intelligence satellite, operated by the National Reconnaissance Office. Launched in 2006, it has been identified as the first in a new series of satellites which are replacing the earlier Trumpet spacecraft.
USA-245 or NRO Launch 65 (NROL-65) is an American reconnaissance satellite which is operated by the National Reconnaissance Office. Launched in August 2013, it is the last Block 4 KH-11 reconnaissance satellite, and the last official spacecraft to be launched in the Keyhole program.
Vulcan Centaur is a heavy-lift launch vehicle created and operated by United Launch Alliance (ULA). It is a two-stage-to-orbit launch vehicle consisting of the Vulcan first stage and the Centaur second stage. It replaces ULA's Atlas V and Delta IV rockets. It is principally designed for the National Security Space Launch (NSSL) program, which launches satellites for U.S. intelligence agencies and the Defense Department, but will also be used for commercial launches.
↑ Kyle, Ed. "Delta IV Launch Record". Space Launch Report. Archived from the original on 25 April 2022. Retrieved 21 January 2023.{{cite web}}: CS1 maint: unfit URL (link)
↑ Whitesides, Loretta Hidalgo (9 July 2008). "Why NASA Isn't Trying to Human-Rate the Atlas V or Delta IV Rockets". Wired. "You could launch a smaller human vehicle on a current expendable rocket [...] In fact, before the Columbia disaster NASA teams were working on an Orbital Space Plane (OSP) designed to do just that".
↑ Schaub, Michael B. "Mission Set Database". NASA GSFC/Honeywell TSI. Archived from the original on 20 March 2009. Retrieved 13 October 2008. This article incorporates text from this source, which is in the public domain.
This Template lists historical, current, and future space rockets that at least once attempted (but not necessarily succeeded in) an orbital launch or that are planned to attempt such a launch in the future
Symbol † indicates past or current rockets that attempted orbital launches but never succeeded (never did or has yet to perform a successful orbital launch)
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