Delta IV

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A starting Delta IV Heavy, the largest of all Delta IV versions

The Delta IV missile family represents the most modern and final variant of the Delta missiles launched since 1960. Delta IV was created as part of the US Air Force's Evolved Expendable Launch Vehicles ( EELV) program for the development of modular missile types that include both the light Delta II who were supposed to replace the medium-weight Atlas II and Atlas III as well as the heavy-duty Titan IV . The Delta IV family was developed by Boeing and is now in direct competition with the Atlas V rocket family from Lockheed Martin, which was also created as part of the EELV program .

In contrast to the Delta II and III , which were all based on the Delta I as the first stage (although this was continuously modified), a completely new first stage was designed for the Delta IV, which is powered by a newly developed RS-68 rocket engine from Rocketdyne . The first stage was named Common Booster Core (CBC) and forms the basis for all versions of the Delta IV. Depending on the number of CBCs, a distinction can be made between the Delta IV Medium and Delta IV Heavy versions .

The Delta IV series was offered in five different versions, four of them in the "Medium" class and one as the "Heavy" variant. The first launch of a Delta IV Medium took place on November 20, 2002, the last on August 22, 2019. The Heavy version first launched on December 21, 2004 and is scheduled to make its last flight in 2023 Template: future / in 3 years. It will then be replaced by the Vulcan Heavy , which is partly based on Delta IV technology.Template: future / in 4 years


The Delta IV is a two-stage rocket, the two stages of which are operated with the high-energy fuel mixture of liquid oxygen and liquid hydrogen (LOX / LH2). It is currently the only rocket in the world that can take off from the earth with a LOX / LH2 main engine in the first stage without the aid of solid fuel boosters (see in contrast the European Ariane 5 and Japanese H-II ). Calculations even show that the first stage of Delta IV could theoretically carry a small payload into orbit without the help of the second stage and thus serve as a single stage carrier. However, this is of no importance in practice because it is uneconomical.

Main level

RS-68 engine on the test stand

The first stage of the rocket, the Common Booster Core (CBC), has been completely redeveloped in contrast to all earlier Delta versions. It forms the basis of all Delta IV versions, with the heavy heavy version using three CBCs (more on this in the Delta IV Heavy section). The CBC is 40.9 m high with a diameter of 4.88 m and weighs about 24.5 tons when empty. The stage contains a friction stir welded tank for liquid hydrogen at the bottom, a friction stir welded tank for liquid oxygen at the top and is powered by an RS-68 engine.

The RS-68 engine used in the first stage of the Delta IV rocket was developed by the US company Rocketdyne. RS-68 was created with the aim of significantly simplifying the engine compared to the SSME space shuttle main engine in order to be able to manufacture it more cheaply. In return, the efficiency of the engine was largely foregone. So were z. B. cheaper manufacturing methods were used, and an ablative cooling (see also: ablative heat shield ) of the thrust nozzle was used. These measures increased the mass of the engine, but the manufacturing costs fell significantly. The engine has a mass of 6696 kg, has a specific momentum of 3580 Ns / kg or 365 s (in a vacuum 4022 Ns / kg or 410 s) and develops a thrust of 2891 kN (in a vacuum 3312 kN) when taking off ), making it the most powerful LOX / LH2 engine in the world. The power of the engine can be regulated from a minimum of 60% to a maximum of 102% of the nominal thrust. An RS-68 will cost about 14 million US dollars . The engine is the first new development of a large rocket engine in the USA since the SSME over 20 years ago.

To increase the payload capacity, the first stage can be reinforced by several GEM-60 solid boosters, which represent an enlarged version of the GEM-46 booster of the Delta III . The boosters, with a composite housing and a diameter of 1.55 m, are built by Alliant Techsystems and have movable thrusters that help the RS-68 main engine control the rocket. On June 29, 2012, a rocket with the enhanced thrust RS-68A engines in their CBCs was launched for the first time.

Second stage of a Delta IV of the medium variant

Upper school

The second stage of the Delta IV was largely carried over from the Delta III and is powered by an RL-10B-2 engine from Pratt & Whitney . The engine generates a thrust of 110 kN, has a specific impulse of 4532 Ns / kg or 462 s and is a variant of the RL-10 engine of the Centaur upper stage, which also has an extendable thrust nozzle. This makes it easier to integrate the stage into the rocket, but still offers increased efficiency after the stage separation and subsequent extension of the nozzle to the full length. The exhaust nozzle, made of carbon fiber composite materials, is manufactured by SEP in France . The stage also differs from the Centaur in that its tanks maintain stability even without pressurization, which is not the case with the Centaur. The stage is practically identical for all versions of the rocket family and only differs in diameter and fuel capacity. There is the smaller stage with a continuous 4 m diameter, 20,410 kg fuel load and a total burning time of around 850 s, as well as the larger stage, whose oxygen tank is about 0.5 m longer and whose hydrogen tank has a diameter of 5 m. This variant of the stage can hold 27,200 kg of fuel and allows a total burn time of over 1125 s.

Payload fairings

The Delta IV Medium and Delta IV Medium + (4.2) use a payload fairing with a diameter of 4 meters made of composite materials. It is 11.75 m high, of which 6.93 m has the full outer diameter of 4 m. In the cylindrical part it has an inner diameter of 3.75 m. The remaining part of the length is taken up by the conical tip, rounded at the top.

The Delta IV Medium + (5.2) and Delta IV Medium + (5.4) use a 5 meter diameter payload fairing made of composite materials. It is 14.34 m high, of which 8.32 m has the full outer diameter of 5 m. In the cylindrical part it has an inner diameter of 4.57 m. The remaining part of the length is taken up by the tip, which is slightly curved inwards and rounded at the top.

Double start capability

ULA offers double starts. The RUAG was awarded a contract to develop twin launchers for the Atlas V and Delta IV, which should be used from 2018 in 2013. So far, however, they have not been used.


Launch complexes for the Delta IV are available on both Cape Canaveral AFS and Vandenberg AFB . In Cape Canaveral, the rocket will be launched in orbits with inclination angles of 42 ° to 110 ° from the LC-37B ramp , which was used for unmanned Saturn I and Saturn IB launches back in the 1960s . In Vandenberg, the rocket lifts off from the SLC-6 launch complex , which was originally built for the launch of the MOL program and was later to serve as a launch pad for the space shuttle. From Vandenberg, inclinations from 151 ° to 210 ° are available. The rocket is assembled and prepared horizontally in an assembly hall (HIF - Horizontal Integration Facility ); before take-off, it is erected vertically on the launch pad with the help of the FPE ( Fixed Pad Erector ). The solid fuel booster and the payload are mounted vertically on the launch pad. The rocket will be manufactured in Alabama and transported to the launch site by ship Delta Mariner .

On June 25, 2003 it was announced that Boeing had access to confidential files of its competitor Lockheed Martin and was aware of its pricing. As a result, Boeing was withdrawn from 20 flights already ordered in July 2003 and was awarded Lockheed Martin. The privilege of being the only company from Vandenberg to put satellites into orbit was also dropped.

A Delta IV Medium + 4.2 on launch pad 37 in Cape Canaveral, with the
GOES-N weather satellite

Deleted Delta IV Small versions

Originally a small series was also planned, which should use a CBC first stage with the RS-68 engine and the Delta K of the Delta II rocket as the second stage . In addition to this first version, there should also be a second small version with an additional Star 48B third stage. According to the plans, this should be able to bring 2200 kg into the geostationary transfer orbit or 1860 kg to escape speed. However, both versions have been deleted.

Delta IV medium

A Delta IV of the Medium series consisted of a CBC first stage with the RS-68 engine and the second stage with the RL-10B2 engine. Different payload fairings were used depending on the payload to be transported. In addition, small solid fuel boosters (GEM-60) could be attached to the first stage of the rocket to increase the payload capacity. Due to the variations in the payload fairings and the number of solid fuel boosters, a total of four different medium versions were available, with the help of which payloads of different mass and diameter could be started flexibly. All four variants were used.

The individual versions of the Medium series were:

  • Payload fairing of a Delta IV Medium + (4.2)
    Delta IV Medium - had a payload fairing 4 m in diameter and no solid fuel boosters. The payload capacity was 8120 kg for a low orbit and 4210 kg for a geotransfer orbit . The first launch took place on March 11, 2003.
  • Delta IV Medium + (4.2) - differed from the basic version of the medium only by two additional GEM-60 boosters, which increased the payload capacity for a low orbit to 10,430 kg and for a geotransfer orbit to 5845 kg. The first launch of this version took place on November 20, 2002 and was also the first launch of a Delta IV at all.
  • Delta IV Medium + (5.2) - differed from the Delta Medium + (4.2) in that it had a payload fairing with a diameter of 5 m and a slightly higher fuel capacity of the second stage. Due to the heavier payload fairing, the payload capacity decreased compared to the Medium + (4.2) to 7980 kg for a low orbit and 4640 kg for a geotransfer orbit. The first launch took place on April 3, 2012.
  • Delta IV Medium + (5.4) - was the most powerful version of the Medium series and differed from the Medium + (5.2) by two additional GEM-60 boosters, bringing the number of boosters to a total of four. The payload capacity was 11,425 kg for a low orbit and 6565 kg for a geotransfer orbit. This version started for the first time on December 5, 2009 with the military communications satellite WGS-3 . On August 22, 2019, she completed the last Delta IV medium flight with a GPS III navigation satellite .

Delta IV Heavy

In order to launch heavy spy satellites and replace the expensive Titan IV rocket, a heavy transport variant of the Delta IV, known as the Delta IV Heavy , was to be developed. This should be relatively cheap to manufacture and operate, and be highly reliable in order to be able to launch the military satellites, which cost up to 1 billion dollars.

Delta IV Heavy during engine ignition (Vandenberg AFB, 2011)


A Delta IV Heavy is set up

The Delta IV Heavy consists of three CBCs, with one CBC forming the central stage and the other two being arranged to the right and left of it. The second stage is powered by an RL-10B2 engine and has a payload fairing 5 m in diameter. At launch, all three CBCs are ignited at the same time, with the rocket rising very slowly and taking about 10 seconds to pass the launch tower. After a while, the RS-68 engine of the central stage is regulated down to 60% of the thrust, whereas the engines of the two additional CBCs continue to work with 102% of the thrust. This ensures that the fuel of the additional CBCs runs out more quickly, so that they are empty and can be discarded after about 4 minutes of flight. The central stage then accelerates the payload until it is completely burned out. The second stage then takes over the acceleration in order to bring the payload into the target orbit.

The Delta IV Heavy is 71 m high and weighs 717 t when it takes off. Your three bundled CBCs develop a total thrust of 8847 kN. The payload capacity is given as 23,000 kg for a low orbit and 13,130 kg for a geotransfer orbit . With the increased thrust RS-68A engines, the payload capacity in the GTO increases further to 14,560 kg. The Delta IV Heavy with the old RS-68 brings about 10,000 kg on a lunar transfer train and about 8000 kg on a Mars transfer train. This makes Delta IV Heavy with the new RS-68A engines the second most powerful US rocket currently in use (the Saturn V moon rocket was much heavier and more powerful, but is no longer in production) and its performance data surpasses both the latest European rocket Ariane 5 ECA as well as the Russian heavy load carrier Proton-M . The Falcon Heavy , on the other hand, with 26,700 kg, offers a higher GTO payload capacity than the Delta IV Heavy with RS-68, as does the future Angara-A5 with 24,500 kg.

Payload fairings

The composite payload fairing is almost 19.1 m high, 13.07 m of which has the full outer diameter of 5 m. In the cylindrical part it has an inner diameter of 4.57 m. The remaining part of the length is taken up by the tip, which is slightly curved inwards and rounded at the top.

The metal payload fairing is 19.81 m high, of which 13.76 m has the full outer diameter of 5 m. In the cylindrical part it has an inner diameter of 4.57 m. The remaining part of the length is taken up by the tip in the form of a double cone rounded at the top. This payload fairing splits into three lengthways when it is released.

As mentioned above, the Delta IV should also be able to carry out launches with two main payloads simultaneously from 2018; however, there were no payloads for which a double launch would have been an option.

First flight

The first launch of the Delta IV Heavy took place on December 21, 2004, 21:50 UTC in Cape Canaveral, with only a 6-ton dummy satellite and two student-built "test satellites" weighing 15 kg each on board. Since Boeing could not find a paying customer for the initial launch , the USAF bought the first test launch of the rocket for a sum that ranged from approximately $ 140 million to $ 170 million. However, the start did not go as planned: Both the boosters and the central stage switched off their engines a little too early, so that the payload was placed in an orbit that was too low. The reason was subsequently identified as the formation of bubbles due to cavitation in the oxygen tank, as a result of which the fuel sensors reported prematurely that the tanks were empty. Nonetheless, Boeing regards the first take-off as a success as all phases of the flight have been successfully tested.

Flight profile in a GTO orbit (231 km × 35,902 km / 27.9 °)

Time (T + ...) height speed event
0 s 0 km 410 m / s Take off, all three CBC to 102% boost
55 s 4.6 km 460 m / s Reduction of the thrust of the central stage to 58%
82 s 11 km 590 m / s Maximum aerodynamic load (Max-Q)
235 s 90 km 3,550 m / s Reduction of the boost of the booster to 58%
242 s 97 km 3,760 m / s Burnout of the booster
245 s 99 km 3,800 m / s Separation of the booster
251 s 105 km 3,890 m / s CBC at 100% thrust level
275 s 127 km 4,440 m / s Separation of the payload fairing
328 s 185 km 6,110 m / s Burn out of the CBC
334 s 193 km 6,120 m / s Stage separation of the first and second stage
347 s 280 km 6,100 m / s Second stage ignition
968 s 507 km 7,530 m / s First burnout, low earth orbit (LEO, 194 × 527 km) reached
4025 s 187 km 7,890 m / s Second ignition of the second stage
4528 s 411 km 10,060 m / s Second burn end of the second stage, GTO orbit reached

Further development

Delta IV family with a hypothetical future heavy variant with seven common booster cores

As the satellite launch market developed slowly for a while, the commercial payloads to be launched were covered by the existing Delta IV medium and heavy variants. In particular, the Delta IV Heavy is so powerful and so expensive that there are no longer any commercial payloads for it on the market, so it is only used to launch heavy spy satellites. Soon Boeing no longer offered the Delta IV on the commercial market, but instead concentrated on the more lucrative government contracts. In 2005, Boeing and Lockheed Martin formed the joint venture United Launch Alliance (ULA). ULA primarily serves for US government start-up contracts. Up until the certification of the Falcon 9 by SpaceX , ULA was practically a monopoly in this area for the transport of payloads weighing several tons, since all US government tenders for satellite transport include the condition that the supplying company must be located in the USA. Other providers in the US did not have missiles that could carry such large payloads. As a result, the starting prices almost doubled after the ULA was founded.


See list of Delta IV rocket launches

Web links

Commons : Delta IV  - collection of images, videos and audio files

Individual evidence

  1. NASA Eyes alternative to Shuttle Main Engine for Heavy Lift
  2. a b c ULA: Delta IV Payload Planners Guide, September 2007 , accessed: March 28, 2012 ( Memento of July 22, 2011 in the Internet Archive ) (PDF; 20.6 MB)
  3. United Launch Alliance (ed.): Delta IV Launch Services User's Guide June 2013 . June 2013, Section 9 AUXILIARY AND DUAL PAYLOAD ACCOMMODATIONS (English, [PDF; accessed January 27, 2019]).
  4. a b Thomas Weyrauch :: ULA: Double starts with components from RUAG., June 28, 2013, accessed June 30, 2013 .
  5. ^ Gunter Krebs: Delta-4. In: Gunter's Space Page. May 15, 2012, accessed May 31, 2012 .
  6. Gunter's Space Page: Delta-4 , accessed: July 1, 2012
  7. Capabilities & Service , SpaceX, accessed February 14, 2018.
  8. Bernd Leitenberger: US launch vehicles . 2nd Edition. BoD - Books on Demand, Norderstedt 2013, ISBN 978-3-7392-3547-9 , pp. 287 .
This version was added to the list of articles worth reading on August 16, 2005 .