The Delta IV Heavy (Delta 9250H) is an expendable heavy-lift launch vehicle, the largest type
of the Delta IV family and the world's second highest-capacity rocket in operation.
It is manufactured by United Launch Alliance and was first launched in 2004.The Delta IV
Heavy consists 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 cores operate at full thrust, and 44 seconds later the center core
throttles down to 55% to conserve fuel until booster separation.
The boosters burn out at 242 seconds after launch and are separated as the core booster
throttles back up to full thrust.
The core burns out 86 seconds later, and the second stage completes the ascent
to orbit.
== History ==
The Delta IV line of rockets was developed by McDonnell Douglas, later United Launch
Alliance.
The Delta IV Heavy is the most powerful member of the line, which also includes the smaller
rocket Delta IV Medium.
The Delta IV Heavy can lift 28,370 kg (62,540 lbs) to low earth orbit and 13,810 kg (30,440
lbs) to geostationary transfer orbit.
It is an all liquid-fueled two-stage rocket, consisting of one main booster and two strap-on
boosters.The first launch of the Delta IV Heavy in 2004 carried a boilerplate payload
(dummy payload) and failed to reach intended orbit.
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.
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 through 2013.In December 2014, the Delta IV Heavy
was used to launch an uncrewed test flight of the Orion Multi-Purpose Crew Vehicle, designated
EFT-1.
After several delays on December 4, the mission was successfully launched at 12:05 UTC on
December 5.
== Capability == Capacity of the Delta IV Heavy:
Low Earth orbit (LEO), 200 km × 28.7°: 28,790 kg (63,470 lb)
Low Earth orbit (ISS), 407 km × 51.6°: 25,980 kg (57,280 lb)
Geosynchronous transfer orbit (GTO): 14,220 kg (31,350 lb)
Geosynchronous orbit (GEO): 6,750 kg (14,880 lb)
Lunar transfer orbit (LTO): 10,000 kg (22,000 lb)
Mars transfer orbit: 8,000 kg (17,600 lb)The Delta IV Heavy's total mass at launch is approximately
733,000 kg (1,616,000 lb).
For comparison, the total mass at launch of the Falcon Heavy, first flown in 2018, is
1,420,788 kg (3,130,000 lb), and the Saturn V used in the Apollo program in the 1960s-70s
was 2,970,000 kg (6,550,000 lb).
== Launch history ==
^A Launched from Cape Canaveral, SLC-37B^B Launched from Vandenberg, SLC-6^C CBCs underperformed,
lower orbit than planned^D Star 48BV upper stage
=== Upcoming launches ===
The following missions have been announced by the National Reconnaissance Office.
== Comparable vehicles ==
== See also ==
Heavy-lift launch vehicle Comparison of orbital launch systems
Comparison of orbital rocket engines Comparison of space station cargo vehicles
National Launch System, (1991–1993) study