Ariane 4

In 1973, eleven nations decided to pursue joint collaboration in the field of space exploration and formed a new pan-national organisation to undertake this mission, the European Space Agency (ESA).[2] Six years later, in December 1979, the arrival of a capable European expendable launch system was marked when the first Ariane 1 launcher was successfully launched from the Centre Spatial Guyanais (CSG) at Kourou, French Guiana.[3] The Ariane 1 soon became considered to be a capable and competitive launcher in comparison to rival platforms offered by the Soviet Union and the United States of America, and it was quickly followed by improved derivatives in the form of the Ariane 2 and Ariane 3. By early 1986, the Ariane 1, along with the Ariane 2 and Ariane 3, had become the dominant launcher on the world market.[4]

In January 1982, the ESA issued its authorisation for the development and construction of the Ariane 4; the development programme had the stated objective of increasing the usable payload by 90%.[5] The Ariane 4 would be a considerably larger and more flexible launcher that the earlier members of its family, being intended to compete with the upper end of launchers worldwide. In comparison, while the Ariane 1 had a typical weight of 207 tonnes and could launch payloads of up to 1.7 tonnes into orbit; the larger Ariane 4 had a typical weight of 470 tonnes and could orbit payloads of up to 4.2 tonnes.[6] Work on the Ariane 4 was substantially eased via drawing heavily on both the technology and experiences gained from producing and operating the earlier members of the Ariane rocket. The total development cost for the Ariane 4 was valued at 476 million European Currency Units (ECU) in 1986.[5]

Posed with the requirement to produce a rocket with substantially greater thrust, the design team considered various approaches to achieve this.[7] One concept studied had involved the addition of a fifth engine to an enlarged first stage of the Ariane 3, but was found to involve a very high level of redesign work to achieve this; instead, the first stage was elongated to hold 210 tonnes of propellant instead of the 145 tonnes present on the Ariane 3. While the second and third stages remained identical to the Ariane 3, a range of strap-on boosters were developed to be applied to the type, designed to gradually increase the rocket's payload capacity.[7] Overall, the Ariane 4 was 15% smaller than the Ariane 3.[8]

In effect, the Ariane 4 was an improved and developed derivative of the earlier Ariane 3, primarily differing through the application of various solid-fuelled and liquid-fuelled boosters, the latter being the only all-new design feature of the Ariane 4; at this point, the practice of using liquid boosters was uncommon, having only previously been used in the Chinese space program.[7] Another innovation of the Ariane 4 was the dual-launch SPELDA (Structure Porteuse Externe de Lancement Double Ariane) fairing.[8] This had the function of allowing a pair of satellites, one placed on top of the other; several different SPELDA nose fairings could be installed, including normal and extended models. The SPELDA was considerably lighter than its predecessor; the guidance system also used much more accurate ring laser gyroscopes.[8] According to aviation author Brian Harvey, the advances present in the design of the Ariane 4 represented a conservative and evolutionary, rather than revolutionary, philosophy.[8]

As the Ariane 4 programme took shape, it gained the support of Belgium, Denmark, Spain, Ireland, Italy, the Netherlands, Germany, Britain, France, Sweden, and Switzerland.[8] The main contractors were Aérospatiale (responsible for the first and second stages), Messerschmitt-Bölkow-Blohm (MBB) (produced the liquid-fuelled boosters), Société Européenne de Propulsion (SEP) (engine manufacturer), Matra (equipment bay assembly), Air Liquide (production of third stage tanks and insulation), BPD Snia (maker of solid-fuelled boosters), and British Aerospace/Contraves Space AG (manufacturers of the fairing).[8] for their work on the Ariane 4, the Launch Team were subsequently awarded the Space Achievement Award by the Space Foundation in 2004.[9]

In conjunction with the development of the Ariane 4 itself, a new purpose-built launch preparation area and launch pad for the rocket, collectively designated as ELA-2, was constructed at the Centre Spatial Guyanais to service the Ariane 4 and provide a launch rate of 8 launches per year (this feat was near-unprecedented for a single large rocket, other than within the Soviet Union).[10] Unlike the earlier ELA-1 which had been used for the previous members of the Ariane family and other rockets, preparation activity for the rocket would be performed in a purpose-built 80-meter tall hall rather than on the pad itself; the completed rocket was then be transported using a specially-designed railway to slowly traverse from the hall to the launch pad, taking one hour. This railway provided the additional benefit of enabling faulty rockets to be withdrawn from the pad and be substituted for relatively quickly.[7]

On 15 June 1988, the first successful launch of the Ariane 4 was conducted.[8] For this first test flight, it was decided to fire the second most powerful version of the rocket, designated 44LP, equipped with four main engines, two solid boosters and two liquid boosters; it was also furnished with the multi-satellite SPELDA fairing. 50 seconds after take-off, the solid boosters would be expended and be detached in order to reduce the rocket's weight.[8] 143 seconds after take-off, the liquid boosters also detached, further lightening the vehicle. The maiden flight was considered a success, having put multiple satellites into orbit.[8]

For the V50 launch onwards, an improved third stage, known as the H10+, was adopted for the Ariane 4.[11] The H10+ third stage featured a new tank, which was 26 kg lighter, 32 cm longer, and contained 340 kg more fuel, which raised the rocket's overall payload capacity by 110 kg and increased its burn time by 20 seconds.[11]

Even prior to the first flight of the Ariane 4, development of a successor, designated as the Ariane 5, had already commenced.[12] In January 1985, the Ariane 5 had been officially adopted as an ESA programme. It lacked the high levels of commonality that the Ariane 4 had with its predecessors, and had been designed not only for launching heavier payloads of up to 5.2 tonnes and at a 20% cost reduction over the Ariane 4, but for a higher margin of safety due to the fact that the Ariane 5 was designed to conduct crewed space launches as well, being intended to transport astronauts using the proposed Hermes space vehicle.[13] Development of the Ariane 5 was not without controversy as some ESA members considered the more mature Ariane 4 to be more suited for meeting established needs for such launchers; it was for this reason that Britain chose not to participate in the Ariane 5 programme.[14] For some years, Ariane 4 and Ariane 5 launchers were operated interchangeably; however, it was eventually decided to terminate all Ariane 4 operations in favour of concentrating on the newer Ariane 5.[15]