Delta (rocket family)

The Delta is one of the most successful U.S. launch vehicles. It was developed by the company Douglas Aircraft Company and used the Thor rocket elementary levels. Over the years, Delta has been continually modified and expanded so that today's Delta hardly anything in common with the first models. Thus, the initial weight increased, for example, of about 50 tons in 1960 to 700 t in 2004, the payload capacity for the Geotransferorbit (short GTO) in the same period of 130 kg to 13130 ​​kg. After Douglas Aircraft Company was acquired in 1997 by Boeing, the Delta rockets are now being produced and marketed by Boeing. Since 1960, Delta has launched more than 300 times and reached there a reliability of 95%.


In January 1959, the then just created NASA by the Douglas Aircraft Company awarded a contract for twelve rockets of the type:

  • Level I: Modified Thor IRBM with a block - I- MB -3 engine ( 676 kN thrust)
  • Level II: Modified Able ( called delta ) with an Aerojet AJ -10 - 118 engine (34 kN thrust).
  • Level III: Altair with an ABL X -248 solid motor (12 kN thrust)

The rocket should have a payload capacity of 295 kg for a low Earth orbit and 45 kg for a Geotransferorbit and should serve in the years 1960-61 as an interim solution before other, more powerful missiles were ready for use. Should also be started with the rocket only scientific, meteorological and communications satellites. The rocket was named Thor - Delta, later it was called simply Delta to emphasize the non-military nature of the missile program. Eleven of the first twelve ordered missile were successful, so NASA decided to continue using the Delta and ordered already before 1962 a further 14 missiles.

Over the years, many versions of the Delta rocket emerged, the following are the main described.

Delta I

The first flight of a Thor - Delta on May 13, 1960 in which the satellite Echo 1 should be launched into space, was a failure. But already the second flight with the identical satellites Echo 1A on August 12, 1960 was successful. The rocket was soon given the name Delta and is now often called Delta I.

Early versions

  • Delta (Delta DM- 19) - is the first version of the Thor - Delta, which is also often called Delta DM -19 because of their Thor DM -19 first stage. She had a launch mass of 50 tons and could bring 130 kg into a low orbit or 45 kg in a Geotransfer orbit. This version was launched a total of twelve times, with only one launch was a failure.
  • Delta A - differs from the Delta DM -19 by a modified first stage, which was an improved engine, and now the name DM -21 was carrying. The second stage of the rocket has been modified and also received by the possibility of a re-ignition in orbit. The initial mass of the rocket remained virtually the same, but the payload capacity increased to 181 kg for a low orbit and 54 kg for the GTO. A Delta launched only twice, both launches were successful. The first launch took place on 2 October 1962.
  • Delta B - differs from the delta A only by a longer second stage, which thereby could accommodate more fuel. The payload capacity increased to 370 kg for a low orbit and 68 kg for the GTO. The rocket launched nine times, only a start was not successful. The first launch took place on 13 December in 1962 with the experimental communications satellite relay I.
  • Delta C - received a new Altair -2 third stage, which replaced the old Altair 1. There were also a delta -C1 version, which began a FW- 4D third stage. The payload capacity of the Delta C was 410 kg for a low Earth orbit and 82 kg for the GTO. Delta C ( with C1) has started a total of 16 times, where there were two false starts. The first launch took place on 27 November 1963.
  • Delta D - Delta differs from C by attaching three Castor - I- solid boosters to the first stage of the rocket. In addition, the first stage engine has been modified somewhat. The payload was 450 kg for a low orbit and 104 kg for the GTO. Delta D was started twice, both operations were successful. The first launch took place on 19 August 1964.
  • Delta E - received a new third stage, which was as hard as the old twice. In addition, the diameter of the second stage was increased, so their tanks could hold more fuel. Also, now three boosters were used by Castor Type II, which were a bit stronger than the old Castor I. Again, there was a delta -E1 version with a FW- 4D third stage. The payload capacity of the Delta E then increased to 750 kg for a low orbit, and at 150 kg for the GTO. The rocket was launched 23 times, only a start was not successful. The first launch took place on 6 November 1965.
  • Delta G - this is a Delta E without the third stage, since it was only used for starting from low-flying satellites, for which you do not need an additional third stage. The payload capacity for a low orbit was 735 kg. Delta G had two operations, both of which were successful. The first launch took place on 14 December 1966.
  • Delta Y - is a Delta E Burner with a strong 2- third stage which was about twice as high as the old Altair 2. Delta J could bring 800 kg into a low orbit or 263 kg in GTO. The rocket was launched only once, the start was successful. The first launch took place on July 4, 1968.
  • Delta L - got a somewhat more prolonged first stage, the now 20 t weighed more than the old. As a third step, an FW -4D - stage was used. Thus, the payload capacity of the delta L increased to about 300 kg for the GTO. It was a successful and an unsuccessful start. The first launch took place on 27 August 1969.
  • Delta M - differs from the Delta L by using the Burner 2 upper stage, which was already used in the Delta J. There was also a Delta - M6 version, in which for the first time six Castor II solid rocket boosters were used. The payload capacity for a GTO was 356 kg (454 kg for the Delta M6). There were a total of 13 launches of the M- versions, of which two failed. The first launch took place on September 19, 1968.
  • Delta N - differs from the Delta M only by the absence of the third stage, which was designed for launch into low orbits, for the delta N, was not needed. As in the Delta M, there was a delta -N6 version that was equipped with six boosters. The payload capacity for a low orbit was 900 kg ( 1600 kg with the Delta N6). Of the nine launches of the N versions one was not successful. The first launch took place on 16 August 1968.

Later versions

Since the designation of the many versions of the Delta had become too complicated, it was decided to introduce a new naming system. Now, each version has been assigned a four-digit number, where each digit were assigned according to the following key:

  • The first digit corresponds to a significant change at the first stage of the rocket or the solid boosters. The standing straight in use (since Delta L) Thor LLT level with the Castor II boosters got the number 0
  • The second digit is meant the number of solid rocket boosters, with 0 standing for a missile without booster.
  • The third point corresponding to the second stage. The standing straight in use stage received a 0
  • The fourth point corresponding to the third stage. A Star - 37D - stage received a 3 and a 4 Star 37E a

Delta II

The Delta II differed from the 6000 series only by a modified engine of the first stage and by new solid rocket boosters. The first stage was an RS- 27A engine, which provided a little more thrust than the RS -27. Castor IV booster were replaced by slightly larger GEM -40- booster. For the Delta II the numeric labeling system was used, it was a 7 to the first position. There is also since 2003 a Delta II with stronger GEM -46 boosters that were utilized also in the Delta III, and were adopted by this. This Delta rockets are characterized by the addition of the letter H. The payload capacity of a Delta II 7920 is about 5000 kg for a low orbit and a Delta II 7925 about 1800 kg for the GTO.

The first launch of a Delta II took place with a GPS satellite on board on 26 November 1990. Since then, she has flown more than 100 times, which so far were only two false starts, the last on January 16, 1997 ( as of early 2005). Since the Delta II has become too weak for commercial communications satellites since the early 90s, it is now mainly for starting small military satellites, such as the GPS satellites by the end of the GPS IIR -M series and to launch research satellites NASA uses. In addition, most interplanetary spacecraft NASA were started with the Delta II, such as all Mars missions from 1996 to 2003, Stardust, MESSENGER, Deep Impact, and many others.

For low Earth orbit and planetary missions also versions available with only three or four booster available. The Delta II is also used at the start of some very light spacecraft with a smaller third stage. This has a Star - 37FM - drive and weighs only 1063 kg instead of 2141 kg as the PAM -D upper level. However, the new upper reduces the payload capacity solid, which is why it is very rarely used. This high school was as a final figure 6 it was used previously only for the first missions IMAGE, Stardust, Genesis and Deep Space

Based on the nomenclature of the newer Delta IV NASA also speaks of the Delta 2xxx. Here is a likelihood of confusion with the 2000 series of the Delta I. The manufacturer Boeing but has retained the old spelling 7xxx.

The Delta II is expected to be a few more years, then they should be replaced by the newer Delta IV rocket.

Delta III

Since Delta II has become too small to launch commercial payloads by the rising satellite mass, it was decided to develop the mid- 1990s, the much stronger Delta III.

At the first stage of the Delta III was hardly changed slightly compared to Delta II: the tanks have been shortened, so as not to increase the overall length of the missile significantly, as well, the old GEM -40 solid rocket boosters of the slightly longer and wider GEM - 46 also called GEM LDXL ( Large Diameter Extended Length), replaced. Delta III received a new, high-energy second stage, which was powered by a Pratt & Whitney RL- 10B2 engine. RL- 10B2 used liquid hydrogen and oxygen as fuel and delivered a thrust of 110 kN. The engine is a variant of the RL -10 engine, the Centaur upper stage, which also has a extendable exhaust nozzle parts. This step makes it easier to integrate into the rocket, but still offers after the staging and subsequent extension of the nozzle to the full length increased performance. Consisting of carbon fiber composites exhaust nozzle is manufactured SEP in France. The stage is different from the Centaur also by the fact that their tanks maintain stability even without pressurization, which is not the case with the Centaur. The diameter of the hydrogen tank to the second stage is 4 m, that of the underlying oxygen tank 2.4 m, which corresponds to the diameter of the Delta II. In addition, the rocket was given a new more spacious payload fairing with 4 m diameter. By all these measures, the payload capacity of the Delta III more than twice a Delta II also for the Delta III rose to 3810 kg for the Geotransfer orbit, applies the numerical designation system, focus is on the first place, an 8 and in the third one 3 for the new second stage. NASA would use against it in accordance with its new nomenclature in the first place a 3.

The first launch of a Delta III was held on 27 August 1998 and ended shortly after take-off with an explosion of the rocket. Also the next launch on 5 May 1999 was a failure. It was not until the third launch on 23 August 2000, the payload reached orbit, but this was lower than expected, so this launch was to evaluate only as a partial success. All three missiles were flying in the version 8930th

After these failures, the production of the Delta III has been set, and it was eventually replaced by the new Delta IV in 2002. All payloads of the Delta III were thereby transferred to the Delta IV. Some designed for the delta III technologies are used in the delta IV, such as the second stage of the delta III is taken over almost unchanged. The GEM -46 solid rocket boosters were taken against it by the Delta III for the new Delta II Heavy versions.

Delta IV

On 20 November 2002, the first Delta IV launched from Cape Canaveral by. Delta IV was developed as part of the Evolved Expendable Launch Vehicles - Program of the U.S. Air Force to replace the older types of rockets. For the Delta IV a completely new first stage was designed to be powered by a newly developed Rocketdyne RS- 68 rocket engine. The engine burns liquid hydrogen with liquid oxygen ( LH2/LOX ). The first stage was called CBC (Common Booster Core) and formed the basis for all versions of the Delta IV second stage of the Delta IV was largely taken from the Delta III.

Currently offered by Boeing five different versions of the Delta IV series:

  • Delta IV medium - has a payload fairing of four meters in diameter and no solid rocket boosters.
  • Delta IV Medium (4,2) - differs from the medium - basic version with two additional GEM -60 booster.
  • Delta IV Medium (5,2) - differs from the Medium ( 4,2) version with a payload fairing of five meters in diameter and a slightly higher fuel capacity of the second stage.
  • Delta IV Medium (5.4 ) - the strongest version of the media number, and differs from the medium (5,2) by two further GEM -60- booster, so that the number of booster increases to four.
  • Delta IV Heavy - consists of three bundled CBCs as first stage, and is about twice as strong as the strongest medium version.