Delta IV Heavy
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. 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 in 9 April 2024.
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 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 |
|
| Launch history | |
| Status | Retired |
| Launch sites |
|
| 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 | |
| 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) |
| 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 |
| 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) |
| 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 |
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.
The launch vehicle used three RS-68 engines, one in the central core and one in each booster. 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.