Delta IV

United Launch Alliance Delta IV rocket page.


Manufacturer: United Launch Alliance
Cost: $164 million
Stages: 2
Boosters: 2 to 4 (optional)
Height: 63 to 72 m (207 to 236 ft)
Diameter: 5 m (16 ft)
Mass: 249,500 to 733,400 kgs (550,100 to 1,616,900 lbs)
Payload capacity (to LEO): 9,190 to 28,370 kgs (20,250 to 62,540 lbs)
Maiden flight: November 20, 2002


The first digit following the M+ variants refers to the fairing size in meters. The second is the number of solid rocket boosters (SRBs).

Medium: active
M+(4,2): active
M+(5,2): active
M+(5,4): active
Heavy: active

Stage 1

Length: 36.6 m
Diameter: 5 m
Engine: 1x RS-68A
Fuel: LH2/LOX
Thrust: 3,140 kN (705,000 lbf)
Burn Time: 245 seconds

Stage 2 (2 variants)

Length: 12.2 or 13.7 m
Diameter: 4 or 5 m
Engine: 1x RL10-B-2
Fuel: LH2/LOX
Thrust: 110 kN (25,000 lbf)
Burn Time: 850 or 1,125 seconds

M+ Boosters

Length: 15.2 m
Diameter: 1.52 m
Engine: 1x GEM 60
Fuel: HTPB/Aluminum
Thrust: 826.6 kN (185,800 lbf)
Burn Time: 91 seconds

Heavy Boosters

Length: 36.6 m
Diameter: 5 m
Engine: 1x RS-68A
Fuel: LH2/LOX
Thrust: 3,140 kN (705,000 lbf)
Burn Time: 245 seconds

The Delta IV was developed by Boeing and is currently operated by United Launch Alliance. The rocket is an expendable launch system that was developed primarily to service the requirements of the U.S. Military. The Delta IV is currently offered in five variants: Medium, Medium+ (4,2), Medium+ (5,2), Medium+ (5,4), and Heavy. Initially, a sixth Small variant was proposed by Boeing but it was later dropped.

Although the Delta IV retained the name of the Delta family of launch vehicles, the rocket was unique to what had come before it. The primary difference between the Delta Iv and previous Delta rockets was that it used a new liquid hydrogen-fueled engine, the Rocketdyne RS-68. Previous Delta launch vehicles used kerosene-fueled engines. The RS-68 was also the first liquid-propellant rocket engine developed in the U.S since the Space Shuttle.

In 2002, the Delta IV was launched for the first time in a Medium+ (4,2) configuration. With the success of a maiden flight, the rocket entered a commercial launch market in which supply far outstripped demand. As a result, in 2003, Boeing made the decision to pull the Delta IV from the commercial market. In 2005, Boeing announced that they would explore the possibility of returning the Delta IV to commercial service. However, apart from its maiden flight (Eutelsat W5), every Delta IV since has been bought and paid for by the U.S. government.

The Heavy variant of the Delta IV was, for a time, the most powerful launch vehicle in the world. However, in February 2018, the Falcon Heavy surpassed the Delta IV by more than doubling its lift capacity.