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Delta IV (Delta 9000)
Delta IV Medium launch carrying DSCS III-B6
Delta IV Medium launch carrying DSCS III-B6
Function Orbital launch vehicle
Manufacturer Boeing BDS
United Launch Alliance
Country of origin United States
Height 63-72 m (206-235 ft)
Diameter 5 m (16.4 ft)
Mass 249,500-733,400 kg (550,000-1,616,800 lb)
Stages 2
Payload to LEO 9,420-28,790 kg[1] (20,750-63,450 lb)
Payload to
4,440-14,220 kg (8,500-28,620 lb)
Launch history
Status Active
Launch sites SLC-37B, Cape Canaveral
SLC-6, Vandenberg AFB
Total launches
  • Medium: 3
  • Medium+ (4,2): 13
  • Medium+ (5,2): 2
  • Medium+ (5,4): 5
  • Heavy: 9
  • Medium: 3
  • Medium+ (4,2): 13
  • Medium+ (5,2): 2
  • Medium+ (5,4): 5
  • Heavy: 8
Partial failures 1 (Heavy)
First flight
  • Medium: March 11, 2003
  • Medium+ (4,2): November 20, 2002
  • Medium+ (5,2): April 3, 2012
  • Medium+ (5,4): December 6, 2009
  • Heavy: December 21, 2004
Last flight
  • Medium: November 4, 2006
  • Medium+ (4,2): March 25, 2015
  • Medium+ (5,2): February 10, 2016
  • Medium+ (5,4): July 24, 2015
  • Heavy: June 11, 2016
Boosters (Medium+) - GEM 60
No boosters Medium+ (4,2), Medium+ (5,2): 2
Medium+ (5,4): 4
Gross mass 33,638 kg (74,158 lb)
Thrust 826.6 kN (185,800 lbf)
Specific impulse 245 s (sea level)
Burn time 91 seconds
Boosters (Heavy) - CBC
No boosters 2
Gross mass 226,400 kg (499,100 lb)
Engines 1 RS-68A
Thrust 3,140 kN (705,000 lbf) (sea level)
Specific impulse Sea level: 360 sec
Vacuum: 412 sec
Burn time 242 seconds[1]
Fuel LH2/LOX
First Stage - CBC
Gross mass 226,400 kg (499,100 lb)
Engines 1 RS-68A
Thrust 3,140 kN (705,000 lbf) (sea level)
Specific impulse Sea level: 360 sec
Vacuum: 412 sec
Burn time 245 seconds (328 seconds in Heavy configuration)[1]
Fuel LH2/LOX
Second Stage - DCSS
Gross mass 4-m: 24,170 kg (53,290 lb)
5-m: 30,700 kg (67,700 lb)
Engines 1 RL10-B-2
Thrust 110 kN (25,000 lbf)
Specific impulse 462 s
Burn time 850-1,125 seconds
Fuel LH2/LOX

Delta IV is an expendable launch system in the Delta rocket family. The rocket's main components are designed by Boeing's Defense, Space & Security division and built in the United Launch Alliance (ULA) facility in Decatur, Alabama. Final assembly is completed at the launch site by ULA.[2] The rockets were designed to launch payloads into orbit for the United States Air Force Evolved Expendable Launch Vehicle (EELV) program and commercial satellite business. Delta IV rockets are available in five versions: Medium, Medium+ (4,2), Medium+ (5,2), Medium+ (5,4), and Heavy, to cover a range of payload size and weight. Delta IV was primarily designed to satisfy the needs of the U.S. military.

The rockets are assembled at the Horizontal Integration Facility for launches from SLC-37B at Cape Canaveral, and in a similar facility for launches from SLC-6 at Vandenberg Air Force Base.

History[edit | edit source]

The Delta IV entered the space launch market 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 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 sought to return the Delta IV to commercial service.[3]

All of Delta IV's launches, with the exception of its debut launch carrying the Eutelsat W5 commercial communications satellite, were paid for by the US government. In 2015, ULA stated that a Delta IV Heavy is sold for nearly $400 million.[4]

Recent history[edit | edit source]

The United States Air Force (USAF) funds Delta IV engineering, integration, and infrastructure through contracts with Boeing Launch Services (BLS). On August 8, 2008 the USAF Space and Missile Systems Center increased the "cost plus award fee" contract with BLS for $1.656 billion to extend the period of performance through the end of FY09. In addition a $557.1 million option was added to cover FY10.[5]

In March 2015, ULA announced plans to phase out all Delta IV launchers except the Delta IV Heavy by 2018.[6] The Delta IV will be largely replaced by the Atlas V.[7]

2012 upper stage anomaly[edit | edit source]

On October 4, 2012, a Delta IV M+ (4,2) experienced an anomaly in the upper stage's RL10-B-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, 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.[8]

By December 2012 ULA had determined the cause of the anomaly to be a fuel leak, 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.[9] Originally scheduled to launch in October 2013, the vehicle lifted off on February 21, 2014.[10]

Planned successor[edit | edit source]

The 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.[11]

Vehicle description[edit | edit source]

Delta IV first stage[edit | edit source]

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, which burns liquid hydrogen and liquid oxygen.

In 2002, the RS-68 became the first large liquid-propellant rocket engine designed in the U.S. since the Space Shuttle Main Engine (SSME) in the 1970s.[12] 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.[13] On the Heavy variant, 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 allows the main CBC to conserve propellant and burn after booster separation. After the strap-on CBCs separate, the main CBC's engine throttles back up to 102% before throttling back down to 58% prior to main engine cutoff.[14]

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 feedline to carry the liquid oxygen to the RS-68 from the tank. The CBC is of a constant, 5-meter (16.4 ft) diameter.[12]

Delta Cryogenic Second Stage[edit | edit source]

The upper stage of the Delta IV, or DCSS, is based on the Delta III upper stage, but with increased propellant capacity. The 4-meter (13.1 ft) version uses lengthened propellant tanks, while the 5-meter version has a 5-meter diameter liquid hydrogen tank and a further lengthened liquid oxygen tank. The second stage is powered by a RL10B2 engine, which features an extendable carbon-carbon nozzle to improve specific impulse.[15] Depending on variant, two different interstages are used to mate the first and second stages. A tapering interstage which narrows down from 5 m to 4 m in diameter is used on 4-meter variants, where a cylindrical interstage is used on 5-meter variants. Both interstages are built from composites.[16][17]

Guidance, navigation, control and communications[edit | edit source]

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.[18]

Payload encapsulation[edit | edit source]

To encapsulate the satellite payload, a variety of different payload fairings are available. A stretched Delta III 4-meter composite payload fairing is used on 4-meter variants, while an enlarged, 5-meter composite fairing is used on 5-meter variants. A longer fairing version is standard on the Heavy variant, and a Boeing-built Titan IV-derived, 5-meter, aluminum isogrid fairing is also available for the Heavy.[19] The Delta IV is over 62 m (205 ft) tall.

Comparable rockets

Angara - Ariane 5 - Atlas V - Falcon 9 - Falcon Heavy - GSLV III - H-IIB - Long March 5 (or Chang Zheng 5) - UMLV - Proton

Variants[edit | edit source]

Delta IV Small[edit | edit source]

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.[20] The Small variant was dropped by 1999.[21][22]

Delta IV Medium[edit | edit source]

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. The Delta IV Medium is capable of launching 4,200 kg to geosynchronous transfer orbit (GTO). The GTO orbit is 1804 m/s away from GEO. The mass of fairing and payload attach fittings have been subtracted from the gross performance.[23]

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 booster Graphite-Epoxy Motors (GEM-60s) strap-on boosters to increase payload capacity to 6,150 kg to GTO.[23]

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 5,072 kg to GTO.[23]

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 6,882 kg to GTO.[23]

Delta IV Heavy[edit | edit source]

Delta IV Heavy launching

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.[24] An aluminum trisector (three-part) fairing derived from the Titan IV fairing is also available.[25] This was first used on the DSP-23 flight.

Delta IV evolution

RS-68A upgrade[edit | edit source]

The possibility of a higher performance Delta IV was indicated in a 2006 RAND Corporation study of national security launch requirements out to 2020,[26] which noted that a single National Reconnaissance Office (NRO) payload would require an increase in the lift capability of the Delta IV Heavy. This was achieved using the higher-performance RS-68A engine,[27] and launched on June 29, 2012.[28] ULA phased out the baseline RS-68 engine with the launch of Delta flight 371 on March 25, 2015. All future launches will use the RS-68A,[29] with the engine's higher thrust allowing use of a single CBC design for all Delta IV Medium and M+ versions. This upgrade reduces cost and increases flexibility, since any standardized CBC can be configured for zero, two, or four solid boosters; this CBC will necessitate a slight performance loss for most medium configurations.[30] The Delta IV Heavy will still require non-standard CBCs for the core and boosters.[31]


Version Fairing CBCs SRBs Payload to LEO

407 km x 51.6°

Payload to GTO

1800 m/s residual

Launches to date
Medium 4 m 1 0 8,510 kg[32] 4,440 kg[1] 0
M+(4,2) 4 m 1 2 12,000 kg[32] 6,390 kg[1] 0
M+(5,2) 5 m 1 2 10,220 kg[32] 5,490 kg[1] 1
M+(5,4) 5 m 1 4 12,820 kg[32] 7,300 kg[1] 1
Heavy 5 m 3 0 25,980 kg[32] 14,220 kg[1] 2






Payload to LEO

407 km x 51.6°

Payload to GTO

1800 m/s residual

Launches to date

Medium 4 m 1 0 8,800 kg[32] 4,540 kg[33] 3
M+(4,2) 4 m 1 2 11,920 kg[32] 6,270 kg[33] 13
M+(5,2) 5 m 1 2 10,580 kg[32] 5,430 kg[33] 1
M+(5,4) 5 m 1 4 13,450 kg[32] 7,430 kg[33] 4
Heavy 5 m 3 0 22,980 kg[32] 13,400 kg[33] 7

*Masses include Payload Attach Fitting weighing from 240 kg to 1,221 kg depending on payload.[1]

Future variants[edit | edit source]

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.[24]

At one point NASA planned to use Delta IV or Atlas V to launch the proposed Orbital Space Plane,[34] which eventually became the Crew Exploration Vehicle and then the Orion. Orion was intended to fly on the Ares I launch vehicle, then the Space Launch System after Ares I was cancelled.

In 2009 The Aerospace Corporation reported on NASA results of a study to determine the feasibility of modifying Delta IV to be human-rated for use in NASA human spaceflight missions. According to Aviation Week the study, "found that a Delta IV heavy [...] could meet NASA's requirements for getting humans to low Earth orbit."[35]

A possible upgrade to the Delta IV family is the creation of new variants by the addition of extra solid motors. One such modification, the Medium+(4,4), would pair the four GEM-60s of the M+(5,4) with the upper stage and fairing of the (4,2). This would theoretically provide a GTO payload of 7,500 kg (16,600 lb) and an LEO payload of 14,800 kg (32,700 lb). This is the simplest variant to implement and is available within 36 months of the first order. Two other possible versions, the Medium+(5,6) and (5,8), would add two or four extra GEM-60s to the (5,4) variant, respectively. These would provide significantly higher performance (up to 9,200 kg/20,200 lb to GTO for the M+(5,8)) but would require more extensive modifications to the vehicle, such as adding the extra attach points and changes to cope with the different flight loads. They would also require pad and infrastructure changes. The Medium+(5,6) and (5,8) can be available within 48 months of the first order.[36]

Launch sites[edit | edit source]

First Delta IV Heavy with three CBCs prior to launch

Delta IV launches occur from either of two rocket launch sites. Launches on the East coast of the United States, Space Launch Complex 37 (SLC-37) at the Cape Canaveral Air Force Station. On the West coast, polar-orbit and high-inclination launches use Vandenberg Air Force Base's Space Launch Complex 6 (SLC-6) pad.

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. The horizontal rocket assembly of the Delta IV are similar to the ones with the assembly of Soyuz launch vehicles; they are also assembled horizontally, unlike the Space Shuttles, the past Saturn launch vehicles and the upcoming Space Launch System, where they are assembled and rolled out to the launch pad entirely vertically.

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.[37]

Vehicle processing[edit | edit source]

Delta IV 4-Meter Second Stage

Delta IV CBCs are assembled at ULA'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.[38]

Delta IV launches[edit | edit source]

This list was last updated on June 12, 2016. For future launches, see List of Thor and Delta launches (2010–2019).

Notable past launches[edit | edit source]

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. 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 December 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 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.[70]

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

DSP-23 was the first launch of a valuable payload aboard a Heavy vehicle. 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 November 10, 2007.[71]

NROL-26 was the first "heavy" EELV launch for the NRO. It carried USA 202, a classified reconnaissance satellite, on a Delta IV Heavy that lifted off January 18, 2009.[72]

NROL-32 was a "heavy" launch, carrying a satellite for NRO. The payload is speculated to be the largest satellite sent into space. The rocket lifted off on November 21, 2010;[73] the launch was delayed from October 19.

NROL-49 lifted off from Vandenberg AFB on January 20, 2011.[44] 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.[74]

A Delta IV Heavy launched the Orion spacecraft on an uncrewed test flight, EFT-1, on December 5, 2014.[75] The launch was originally planned for December 4, but high winds and valve issues caused the launch to be rescheduled for December 5.[76]

Planned launches[edit | edit source]

  • The first GPS Block IIIA satellite will be launched using a Medium+ (4,2) rocket.

See also[edit | edit source]

References[edit | edit source]

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 "Delta IV User's Guide". ULA. June 2013. Archived from the original on July 2014. https://web.archive.org/web/20140710005717/http://www.ulalaunch.com/uploads/docs/Launch_Vehicles/Delta_IV_Users_Guide_June_2013.pdf. Retrieved July 2014. 
  2. "Boeing and Lockheed Martin Complete United Launch Alliance Transaction". Boeing. December 1, 2006. http://www.boeing.com/news/releases/2006/q4/061201a_nr.html. 
  3. "Boeing's Delta IV may return to commercial launches". Orange County Register. March 25, 2005. http://www.ocregister.com/ocr/2005/03/25/sections/business/business_nation/article_456341.php. 
  4. Clark, Stephen (22 April 2015). "ULA needs commercial business to close Vulcan rocket business case". Spaceflight Now. http://spaceflightnow.com/2015/04/22/ula-needs-commercial-business-to-close-vulcan-rocket-business-case/. Retrieved 23 April 2015. 
  5. "DefenseLink Contracts for Friday, August 08, 2008". US Department of Defense. 8 August 2008. http://www.defenselink.mil/contracts/contract.aspx?contractid=3837. Retrieved 6 January 2009. 
  6. "ULA Targets 2018 for Delta 4 Phase-out, Seeks Relaxation of RD-180 Ban". http://spacenews.com/ula-targets-2018-for-delta-4-phase-out-seeks-relaxation-of-rd-180-ban/. Retrieved 2015-03-03. 
  7. http://sputniknews.com/science/20150318/1019638384.html
  8. Bergin, Chris. "Home Forums L2 Sign Up ISS Commercial Shuttle SLS/Orion Russian European Chinese Unmanned Other Atlas V green light after RL-10 is exonerated during Delta IV anomaly review". http://www.nasaspaceflight.com/2012/12/atlas-v-green-light-rl-10-exonerated-delta-iv-review/. Retrieved December 9, 2014. 
  9. Gruss, Mike. "Glitch on October 2012 Delta 4 Mission Is Behind GPS 2F-5 Launch Delay". http://www.spacenews.com/article/military-space/37792glitch-on-october-2012-delta-4-mission-is-behind-gps-2f-5-launch-delay. Retrieved December 9, 2014. 
  10. "United Launch Alliance Successfully Launches 25th Delta IV Mission Carrying Global Positioning System Satellite for the U.S. Air Force". United Launch Alliance. 21 Feb 2014. http://www.ulalaunch.com/site/pages/News.shtml#/167/. Retrieved 21 Feb 2014. 
  11. Mike Gruss (13 April 2015). "ULA’s Next Rocket To Be Named Vulcan". Space News. http://spacenews.com/ulas-next-rocket-to-be-named-vulcan/. 
  12. 12.0 12.1 "Space Launch Report: Delta IV Data Sheet". Ed Kyle. September 5, 2010. http://www.spacelaunchreport.com/delta4.html. 
  13. "Delta IV GOES-N Launch Timeline". Spaceflight Now. June 9, 2005. http://www.spaceflightnow.com/delta/d313/050609launchtimeline.html. 
  14. "Delta IV Heavy Demo Launch Timeline". Spaceflight Now. December 1, 2004. http://www.spaceflightnow.com/delta/d310/041201launchtimeline.html. 
  15. "Delta IV Payload Planners Guide". United Launch Alliance. September 2007. pp. 1-5 to 1-6. http://www.ulalaunch.com/site/docs/product_cards/guides/DeltaIVPayloadPlannersGuide2007.pdf. 
  16. "ATK Composite and Propulsion Technologies Help Launch Defense Weather Satellite". Alliant Techsystems. November 2006. http://atk.mediaroom.com/index.php?s=25280&item=57724. 
  17. "ATK Propulsion Technologies Help Launch Boeing’s Delta IV Heavy Rocket". Alliant Techsystems. November 2007. http://www.atk.com/news-releases/atk-propulsion-technologies-help-launch-boeings-delta-iv-heavy-rocket/. 
  18. "L-3 Space & Navigation's RIFCA Trihex"
  19. "Delta IV Payload Planners Guide". United Launch Alliance. September 2007. pp. 1–7. http://www.ulalaunch.com/site/docs/product_cards/guides/DeltaIVPayloadPlannersGuide2007.pdf. 
  20. "Delta IV Small" Astronautix.com
  21. Gunter's Space page - Delta IV
  22. "Boeing Signs agreement for Delta IV Integration Facility". Boeing. January 28, 1999. http://www.boeing.com/news/releases/1999/news_release_990128b.html. 
  23. 23.0 23.1 23.2 23.3 "Delta IV Launch Services User's Guide". United Launch Alliance. June 2013. pp. 2–10,5-3. http://www.ulalaunch.com/uploads/docs/Launch_Vehicles/Delta_IV_Users_Guide_June_2013.pdf. 
  24. 24.0 24.1 "Delta Launch 310 – Delta IV Heavy Demo Media Kit - Delta Growth Options". Boeing. http://www.boeing.com/defense-space/space/delta/kits/d310_d4heavy_demo.pdf. 
  25. US Air Force - EELV Fact Sheets
  26. Forrest McCartney (2006). "National Security Space Launch Report" (PDF). RAND. pp. 6–7. https://www.rand.org/pubs/monographs/2006/RAND_MG503.pdf. 
  27. "Three Pratt & Whitney Rocketdyne RS-68A Engines Power Delta IV Heavy Upgrade Vehicle on Inaugural Flight". http://www.prnewswire.com/news-releases/three-pratt--whitney-rocketdyne-rs-68a-engines-power-delta-iv-heavy-upgrade-vehicle-on-inaugural-flight-160868765.html. Retrieved November 2014. 
  28. 28.0 28.1 28.2 "United Launch Alliance Upgraded Delta IV Heavy rocket successfully Launches Second Payload in Nine Days for the National Reconnaissance Office". United Launch Alliance. 2012-06-29. http://www.ulalaunch.com/site/pages/News.shtml#/109/. 
  29. 29.0 29.1 "Delta 4 rocket evolving to upgraded main engine". Spaceflight Now. 27 March 2015. http://spaceflightnow.com/2015/03/27/delta-4-rocket-evolving-the-upgraded-main-engine/. Retrieved 28 March 2015. 
  30. "New Delta 4 Engine Variant is Part of ULA Cost Cutting Strategy". http://www.spacenews.com/article/new-delta-4-engine-variant-part-ula-cost-cutting-strategy. 
  31. "Ongoing Launch Vehicle Innovation at United Launch Alliance". ULA. March 2010. Archived from the original on March 2014. https://web.archive.org/web/20140328201054/http://ulalaunch.com/site/docs/publications/ULA-Innovation-March-2010.pdf. Retrieved July 2014. 
  32. 32.0 32.1 32.2 32.3 32.4 32.5 32.6 32.7 32.8 32.9 "Delta IV". http://www.spacelaunchreport.com/delta4.html. 
  33. 33.0 33.1 33.2 33.3 33.4 "Delta IV Payload Planner's Guide". September 2007. http://www.scribd.com/doc/16924978/Boeing-Delta-IV-Payload-Planners-Guide. 
  34. Whitesides, Loretta Hidalgo (July 9, 2008). "Why NASA Isn’t Trying to Human-Rate the Atlas V or Delta IV Rockets". Wired. http://www.wired.com/wiredscience/2008/07/why-nasa-isnt-t/. ""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."" 
  35. Frank Morring, Jr. (June 15, 2009). "Study Finds Human-rated Delta IV Cheaper". Aviation Week. http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/Study061509.xml. 
  36. "Delta IV Payload Planners Guide". ULA. September 2007. pp. 10–15, 16. Archived from the original on July 2011. https://web.archive.org/web/20110722081616/http://www.ulalaunch.com/site/docs/product_cards/guides/DeltaIVPayloadPlannersGuide2007.pdf. 
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