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	72 m (236 ft)
Diameter	5 m (16 ft)
Width	15 m (49 ft)
Mass	733,000 kg (1,616,000 lb)
Stages	2+
Capacity
Payload to LEO
Mass	28,790 kg (63,470 lb)
Payload to GTO
Mass	14,220 kg (31,350 lb)
Associated rockets
Family	Delta
Comparable	Long March 5 Falcon Heavy Proton-M
Launch history
Status	Retired
Launch sites	Cape Canaveral, SLC-37B 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 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 in 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]