Delta IV Heavy

Delta IV Heavy

Delta IV Heavy launches from Vandenberg Space Force Base
Function	Orbital heavy-lift launch vehicle
Manufacturer	United Launch Alliance
Country of origin	United States
Cost per launch	US$350 million[1] NRO: US$440 million
Size
Height	70.7 m (232 ft)
Diameter	5.1 m (17 ft)
Width	15.3 m (50 ft)
Mass	733,000 kg (1,616,000 lb)
Stages	2+
Capacity
Payload to LEO
Mass	28,790 kg (63,470 lb)
Payload to GEO
Mass	6,750 kg (14,880 lb)
Associated rockets
Family	Delta
Comparable	Long March 5 Falcon Heavy Proton-M
Launch history
Status	Retired
Launch sites	Cape Canaveral, SLC-37 Vandenberg, SLC-6
Total launches	16
Success(es)	15
Partial failure(s)	1
First flight	21 December 2004 (USA-181)
Last flight	9 April 2024 (NROL-70)
Type of passengers/cargo	EFT-1 NRO classified payloads Kennen Orion Parker Solar Probe
Boosters (CBC)
No. boosters	2
Height	40.8 m (134 ft)
Diameter	5.1 m (17 ft)
Empty mass	26,000 kg (57,000 lb)
Gross mass	226,400 kg (499,100 lb)
Propellant mass	200,400 kg (441,800 lb)[2]
Powered by	1 RS-68A
Maximum thrust	3,140 kN (710,000 lbf)
Total thrust	6,280 kN (1,410,000 lbf)
Specific impulse	Sea level: 360 s (3.5 km/s) Vacuum: 412 s (4.04 km/s)
Burn time	242 seconds[3]
Propellant	LH2 / LOX
First stage (CBC)
Height	40.8 m (134 ft)
Diameter	5.1 m (17 ft)
Gross mass	226,400 kg (499,100 lb)
Propellant mass	200,400 kg (441,800 lb)
Powered by	1 RS-68A
Maximum thrust	3,140 kN (710,000 lbf)
Specific impulse	Sea level: 360 s (3.5 km/s) Vacuum: 412 s (4.04 km/s)
Burn time	328 seconds
Propellant	LH2 / LOX
Second stage (DCSS)
Height	13.7 m (45 ft)
Diameter	5.1 m (17 ft) (LH2 tank) 3.2 m (10 ft) (LOX tank)[4]
Gross mass	30,700 kg (67,700 lb)
Propellant mass	27,220 kg (60,010 lb)
Powered by	1 RL10-B-2
Maximum thrust	110 kN (25,000 lbf)
Specific impulse	465.5 s (4.565 km/s)
Burn time	1125 seconds
Propellant	LH2 / LOX
[edit on Wikidata]

The Delta IV Heavy (Delta 9250H) was an expendable heavy-lift launch vehicle, the largest type of the Delta IV family. It had the highest capacity of any operational launch vehicle in the world after the retirement of the Space Shuttle in 2011 until the Falcon Heavy debuted in 2018, and it was the world's third highest-capacity launch vehicle in operation at the time of its retirement in 2024.^[5][6][7] It was manufactured by United Launch Alliance (ULA) and was first launched in 2004.^[8] Delta IV Heavy was the last operating member of the Delta IV family, and its final flight was on 9 April 2024. Future ULA launches will use the Vulcan Centaur rocket.^[9][10]

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.^[11] 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.^[12]

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.^[13] 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).^[13] It was an all liquid-fueled launch vehicle, consisting of an upper stage, one main booster and two strap-on boosters.^[13]

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.^[14]

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.^[15]

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.^[16] 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.^[17] The final Delta IV heavy would launch on April 9, 2024.^[18]

Delta IV's final flight was initially scheduled for March 29, 2024 for the National Reconnaissance Office;^[19][20] its actual launch date was April 9, 2024 after a postponement.^[21][18][22]

Capacity of the Delta IV Heavy:

• Low Earth orbit (LEO), 200 km × 28.7°: 28,790 kg (63,470 lb)^[23]
• Low Earth orbit (ISS), 407 km × 51.6°: 25,980 kg (57,280 lb)^[24]
• Geosynchronous transfer orbit (GTO): 14,220 kg (31,350 lb)^[23]
• Geosynchronous orbit (GEO): 6,750 kg (14,880 lb)^[23]
• Lunar transfer orbit (LTO): 10,000 kg (22,000 lb)
• Mars transfer orbit: 8,000 kg (18,000 lb)^[25]

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.^[26]

• Comparison of orbital launch systems
• Comparison of orbital rocket engines
• National Launch System, (1991–1993) study

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