Delta IV Heavy
Delta IV Heavy launches from Vandenberg Space Force Base
FunctionOrbital heavy-lift launch vehicle
ManufacturerUnited Launch Alliance
Country of originUnited States
Cost per launchUS$350 million[1]
NRO: US$440 million
Height70.7 m (232 ft)
Diameter5.1 m (17 ft)
Width15.3 m (50 ft)
Mass733,000 kg (1,616,000 lb)
Payload to LEO
Mass28,790 kg (63,470 lb)
Payload to GEO
Mass6,750 kg (14,880 lb)
Associated rockets
Launch history
Launch sites
Total launches16
Partial failure(s)1
First flight21 December 2004 (USA-181)
Last flight9 April 2024 (NROL-70)
Type of passengers/cargo
Boosters (CBC)
No. boosters2
Height40.8 m (134 ft)
Diameter5.1 m (17 ft)
Empty mass26,000 kg (57,000 lb)
Gross mass226,400 kg (499,100 lb)
Propellant mass200,400 kg (441,800 lb)[2]
Powered by1 RS-68A
Maximum thrust3,140 kN (710,000 lbf)
Total thrust6,280 kN (1,410,000 lbf)
Specific impulseSea level: 360 s (3.5 km/s)
Vacuum: 412 s (4.04 km/s)
Burn time242 seconds[3]
PropellantLH2 / LOX
First stage (CBC)
Height40.8 m (134 ft)
Diameter5.1 m (17 ft)
Gross mass226,400 kg (499,100 lb)
Propellant mass200,400 kg (441,800 lb)
Powered by1 RS-68A
Maximum thrust3,140 kN (710,000 lbf)
Specific impulseSea level: 360 s (3.5 km/s)
Vacuum: 412 s (4.04 km/s)
Burn time328 seconds
PropellantLH2 / LOX
Second stage (DCSS)
Height13.7 m (45 ft)
Diameter5.1 m (17 ft) (LH2 tank) 3.2 m (10 ft) (LOX tank)[4]
Gross mass30,700 kg (67,700 lb)
Propellant mass27,220 kg (60,010 lb)
Powered by1 RL10-B-2
Maximum thrust110 kN (25,000 lbf)
Specific impulse465.5 s (4.565 km/s)
Burn time1125 seconds
PropellantLH2 / LOX

The Delta IV Heavy (Delta 9250H) 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.[5][6] It was manufactured by United Launch Alliance (ULA) and was first launched in 2004.[7] ULA retired the Delta IV Heavy in 2024. Future ULA launches will use the new Vulcan Centaur rocket.[8][9] Delta IV's final flight was on 9 April 2024.

The Delta IV Heavy first stage consisted of a central Common Booster Core (CBC), with two additional CBCs as liquid rocket boosters instead of the GEM-60 solid rocket motors used by the Delta IV Medium+ versions. At lift-off, all three rocket engines would operate at full thrust, and 44 seconds later the central engine would throttle down to 55% to conserve fuel until the other two engines separate. The latter engines burn out at 242 seconds after launch and are separated as the central engine throttles back up to full thrust. The central engine burns out 86 seconds later, and the second stage completed the ascent to orbit.[3]

The launch vehicle used three RS-68 engines, one in the central core and one in each booster.[10] On the last seconds of countdown, the liquid hydrogen fuel would flow through the engines and upwards along the booster body, and after the ignition that hydrogen inflamed, creating the characteristic fireball and charred look of the booster.[11]


Delta IV Heavy for Exploration Flight Test-1

The Delta IV line of rockets were developed by Boeing. The program was later transferred to United Launch Alliance. The Delta IV Heavy was the most powerful member of the line, which also includes the smaller Delta IV Medium.[12] The Delta IV Heavy can lift 28,370 kg (62,550 lb) to low Earth orbit and 13,810 kg (30,450 lb) to geostationary transfer orbit (GTO).[12] It was an all liquid-fueled launch vehicle, consisting of an upper stage, one main booster and two strap-on boosters.[12]

The first launch of the Delta IV Heavy on 21 December 2004 carried a boilerplate payload and was a partial failure. Cavitation in the liquid-oxygen propellant lines caused shutdown of both boosters eight seconds early, and the core engine nine seconds early; this resulted in a lower staging velocity for which the second stage was unable to compensate. The payload was left in a lower than intended orbit.[13]

Its first operational payload was the DSP-23 satellite, successfully launched in 2007; it was then used to launch a further five visual and electronic reconnaissance satellites for the National Reconnaissance Office (NRO) through 2013. In December 2014, the Delta IV Heavy was used to launch an uncrewed test flight of the Orion spacecraft, designated Exploration Flight Test-1 (EFT-1). After several delays, the mission was successfully launched at 12:05 UTC on 5 December 2014.[14]

On 12 August 2018, the Delta IV Heavy with an additional Star 48BV third stage was used to launch the Parker Solar Probe into an elliptical heliocentric orbit.[15] In May 2023, the final Delta IV Heavy core and boosters finished construction, officially ending Delta IV production and making way for the Vulcan launch vehicle.[16] The final Delta IV heavy would launch on April 9, 2024.[17]

Delta IV's final flight was initially scheduled for March 29, 2024 for the National Reconnaissance Office;[18][19] its actual launch date was April 9, 2024 after a postponement.[20][17][21]


Capacity of the Delta IV Heavy:

The Delta IV Heavy's total mass at launch was approximately 733,000 kg (1,616,000 lb) and produce around 952,000 kg (2,099,000 lb) of thrust to power the rocket skyward at liftoff.[25]

Launch history

This section is transcluded from List of Delta IV Heavy launches. (edit | history)

Flight Date Payload [26] Mass Launch site Outcome [26]
1 21 December 2004 DemoSat, Sparkie / 3CS-1 and Ralphie / 3CS-2 6,000 kg (13,000 lb) Cape Canaveral, SLC-37B Partial failure[a]
2 11 November 2007 DSP-23 5,250 kg (11,570 lb) Cape Canaveral, SLC-37B Success
3 18 January 2009 Orion 6 / Mentor 4 (USA-202 / NROL-26) Classified Cape Canaveral, SLC-37B Success
4 21 November 2010 Orion 7 / Mentor 5 (USA-223 / NROL-32) Classified Cape Canaveral, SLC-37B Success
5 20 January 2011 KH-11 Kennen 15 (USA-224 / NROL-49) <17,000 kg (37,000 lb) Vandenberg, SLC-6 Success
6 29 June 2012 Orion 8 / Mentor 6 (USA-237 / NROL-15) Classified Cape Canaveral, SLC-37B Success
7 26 August 2013 KH-11 Kennen 16 (USA-245 / NROL-65) <17,000 kg (37,000 lb) Vandenberg, SLC-6 Success
8 5 December 2014 Orion Exploration Flight Test-1 (EFT-1) 21,000 kg (46,000 lb)[27][b] Cape Canaveral, SLC-37B Success
9 11 June 2016 Orion 9 / Mentor 7 (USA-268 / NROL-37) Classified Cape Canaveral, SLC-37B Success
10 12 August 2018 Parker Solar Probe[c] 685 kg (1,510 lb) Cape Canaveral, SLC-37B Success
11 19 January 2019 NROL-71 Classified Vandenberg, SLC-6 Success
12 11 December 2020 Orion 10 / Mentor 8 (USA-268/ NROL-44)[28][29] Classified Cape Canaveral, SLC-37B Success
13 26 April 2021 KH-11 Kennen 17 (NROL-82) Classified Vandenberg, SLC-6 Success
14 24 September 2022 KH-11 Kennen 18 (NROL-91) Classified Vandenberg, SLC-6 Success
15 22 June 2023 Orion 11 / Mentor 9 (NROL-68)[30] Classified Cape Canaveral, SLC-37B Success
16 9 April 2024 Orion 12 / Mentor 10 (NROL-70) Classified CCSFS, SLC-37B Success
  1. ^ Common Booster Cores underperformed, lower orbit than planned
  2. ^ The officially reported mass of 21,000 kg includes the Launch Abort System (LAS) which did not reach orbit, but excludes the residual mass of the upper stage, which did reach orbit, likely offsetting the mass of the LAS.
  3. ^ Star 48BV upper stage

Comparable vehicles

Further information: Heavy-lift launch vehicle


In development:

Retired or cancelled:

See also


  1. ^ "ULA CEO Tory Bruno". Retrieved 12 February 2018. Delta IV Heavy goes for about US$350M. That's current and future, after the retirement of both Delta IV Medium and Delta II.
  2. ^ "Delta IV Heavy". Spaceflight 101. Retrieved 26 July 2014.
  3. ^ a b "Delta IV Payload Planner's Guide, June 2013" (PDF). United Launch Alliance. Archived from the original (PDF) on 10 July 2014. Retrieved 26 July 2014.
  4. ^ "Delta IV Launch Services User's Guide" (PDF). United Launch Alliance. Retrieved 13 April 2024.
  5. ^ "Mission Status Center". Spaceflight Now. Retrieved 26 July 2014. The ULA Delta 4-Heavy is currently the world's largest rocket, providing the nation with reliable, proven, heavy lift capability for our country's national security payloads from both the east and west coasts.
  6. ^ Chang, Kenneth (6 February 2018). "Falcon Heavy, SpaceX's Big New Rocket, Succeeds in Its First Test Launch". The New York Times. Retrieved 6 February 2018. The Falcon Heavy is capable of lifting 140,000 pounds to low Earth orbit, more than any other rocket today.
  7. ^ "Boeing Delta IV Heavy Achieves Major Test Objectives in First Flight" (Press release). Boeing. 21 December 2004. Archived from the original on 19 April 2012. Retrieved 22 March 2012.
  8. ^ Erwin, Sandra (24 August 2020). "ULA to launch Delta 4 Heavy for its 12th mission, four more to go before rocket is retired". SpaceNews. Retrieved 29 August 2020.
  9. ^ "Delta IV Heavy - NROL-70". Next Spaceflight. 9 February 2024. Retrieved 10 February 2024.
  10. ^ "Delta 4-Heavy likely heading for geosynchronous orbit with top secret payload". Spaceflight Now. 26 August 2020. Retrieved 27 August 2020.
  11. ^ Berger, Eric (21 January 2019). "This massive rocket creates a fireball as it launches, and that's by design". Ars Technica. Retrieved 13 April 2023.
  12. ^ a b c Howell, Elizabeth (20 April 2018). "Delta IV Heavy: Powerful Launch Vehicle". Retrieved 21 July 2018.
  13. ^ "Delta 4-Heavy investigation identifies rocket's problem". Spaceflight Now. 16 March 2005. Retrieved 26 July 2014.
  14. ^ "Second Stage Ignites as First Stage Falls Away". 5 December 2014. Public Domain This article incorporates text from this source, which is in the public domain.
  15. ^ "Delta IV Parker Solar Probe". Retrieved 11 December 2020.
  16. ^ "ULA's Delta rocket assembly line falls silent". Spaceflight Now.
  17. ^ a b "Delta IV Heavy NROL-70". Retrieved 8 April 2024.
  18. ^ Chang, Kenneth (28 March 2024). "A Fiery Finale for a Rocket That Brings the Heat - The Delta IV Heavy, a rocket that briefly bursts into flame just before it lifts off, is set to launch for the last time soon". The New York Times. Archived from the original on 28 March 2024. Retrieved 29 March 2024.
  19. ^ Angle, Richard (15 March 2024). "United Launch Alliance's Delta IV Heavy readies for final flight". TESLARATI. Retrieved 21 March 2024.
  20. ^ Pare, Sascha (28 March 2024). "Secretive Delta IV Heavy rocket launch postponed indefinitely". Retrieved 30 March 2024.
  21. ^ Robert Z. Pearlman (9 April 2024). "'Heavy' history: ULA launches final Delta rocket after 64 years (video, photos)". Retrieved 11 April 2024.
  22. ^ a b c "Delta IV Launch Services User's Guide – June 2013" (PDF). United Launch Alliance. 4 June 2013. pp. 2–10, 5–3. Archived from the original (PDF) on 14 October 2013. Retrieved 31 October 2020.
  23. ^ "Delta IV Data Sheet". Space Launch Report. Archived from the original on 6 December 2012. Retrieved 26 July 2014.((cite web)): CS1 maint: unfit URL (link)
  24. ^ Ray, Justin (7 December 2004). "The Heavy: Triple-sized Delta 4 rocket to debut". Spaceflight Now. Archived from the original on 11 December 2004. Retrieved 13 May 2014.
  25. ^ "Live coverage: Launch of Delta 4-Heavy rocket set for early Saturday". Spaceflight Now. 29 August 2020. Retrieved 29 August 2020.
  26. ^ a b Krebs, Gunter. "Delta-4". Gunter's Space Page. Retrieved 15 March 2018.
  27. ^ "NASA Orion Exploration Flight Test-1 PRESS KIT" (PDF). NASA. December 2014. p. 12. Public Domain This article incorporates text from this source, which is in the public domain.
  28. ^ "Launch Schedule". Spaceflight Now. 27 October 2020. Retrieved 31 October 2020.
  29. ^ "Launch Mission Execution Forecast". 45th Weather Squadron - Patrick Air Force Base. 30 October 2020. Retrieved 31 October 2020. Public Domain This article incorporates text from this source, which is in the public domain.
  30. ^ Clark, Stephen (22 June 2023). "Delta 4-Heavy rocket lifts off with NRO spy satellite". Spaceflight Now. Retrieved 27 June 2023.