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Aviation History
1989
1989 - 0038.PDF
History of Delta growth 1960 1963 1964 1965 1968 1969 1970 1971 1973 1975 1980 1982 1989 Launch vehicle configurations DELTA II DELTA 3920 PAM-D DELTA II 7925 . 2.44m Fairing - Second-. SB stage gj First - stage 1.43m extended - fuel tank - 2.89m fairing 2.23m - extended oxidizer tank 8:1 engine LEO (two-stage) 3,452 kg GTO 1.284 kg Graphite epoxy motors 1:1 engine & 12:1 engine 5,039 kg 1,819 kg Delta has more than tripled its payload capability since I960 (left). Based on the current Delta 3920, Delta II comes in two uprated forms (right) $3 million per successful launch and a $1 million a year award if all contractual obli gations are met. The sting in the tail is that one failure will kill off all incentives, two failures will halve MDC's Delta profits, and three will negate them altogether. MDC has chalked up seven commercial Delta launch contracts: Insat ID, its first commercial launch; British Satellite Broad casting's BSB 1; Inmarsat 2 Fl; Palapa B2R; Inmarsat 2 F2; BSB 2; and Nato IVA. The contracts are worth $350 million, and the satellites will be launched by the end of 1990. The company hopes to secure 12 more contracts through to the second quarter of 1992. Insurance can be handled by MDC at a fixed price, or the customer can arrange his own. Delta developments Also on the schedule are 22 launches through to the end of 1991, mainly for US Air Force Navstars, but also for the Strategic Defence Initiative Office and Nasa. The vehicles will be a mix of the remaining three Delta 3920s and variants of the 3920 and Delta II. These variants are designated 4925, 7920-10, 5920, 6920-10, and 6925-10, signi fying that they have either different solid- rocket motors, or are two-stage versions, some with 3m (10ft) fairings. Introduced into the schedule will be the new Delta II models, 6925 and 7925. McDonnell Douglas is also considering further uprated versions of the' Delta. Launch rates of seven a year are possible from Cape Canaveral, building up to 12 a year in a few years' time. Each launch is customised to the user's mission and sched ule requirements. With the absence of mani festing competition. MDC claims better cost control and overall efficiency. The introduction of the first 6925 vehicle into the two-phase Delta II development programme provides the US Air Force with an early initial launch capability for nine lighter, 839kg, Block 1 Navstar II satellites. The first of these will be launched from Cape Canaveral into the required 17,436km-high, 55°-inclined circular orbit early next year, on the first Delta II launch. The 6925, also known as the Interim Delta II, can launch 1,447kg into a 28-7°, 160km by 30,916km geostationary transfer orbit (GTO), or, as a two-stage vehicle, can lift 3,983kg into low Earth orbit (LEO) from Cape Canaveral, an improvement of 163kg and 531kg over the Delta 3920/Pam D and two-stage Delta 3920, respectively. The Delta 6925 launched from the West ern Test Range at Vandenberg Air Force Base, California, can carry 962kg into a Molniya-type highly elliptical, 320km by 34,638km orbit with an inclination of 63-4°. A two-stage Vandenberg-launched vehicle could place a 2,567kg payload into a 98-7° sun-synchronous 720km circular orbit, or 3,025kg into a 99°, 160km LEO. Vehicle modifications include the addi tion of a 2 • 9m-diameter payload fairing for use on both the two- and three-stage versions; stretching the first-stage fuel and oxidiser tanks by l-43m and 2-23m respectively; and replacement of the Thiokol Castor IV solid strap-on boosters by Castor IVAs, with higher-energy propellant, but using the same case and nozzle. The second stage and Pam D third stage remain unchanged. Originally MDC planned to replace the solid-rocket motors with similar-sized units of carbonfibre epoxy, supplied by Hercules Aerospace, and to enhance the first-stage engine expansion ratio from 8:1 to 12:1. The new vehicle was to be called the Delta II 7920, and the Delta 7925 could have been an enhanced Delta II with longer Hercules motors. The planned 7920 was discarded, however, and the 7925 became plain Delta II. In the three-stage configuration, the 6925 and 7925 vehicles are 38-41m long. The 7925 vehicle will launch at least ten of the heavier, 1,134 kg, Block II Navstar 2s, and will be able to place 1,819kg into GTO. As a two-stage vehicle it will take 5,039kg into LEO from Cape Canaveral. Delta 7925 launches from Vandenberg could carry 1,275kg to a Molniya-type orbit, 3,261kg to sun-synchronous orbit, and 3,819kg to LEO. Nominal orbital inclinations available for launches from Cape Canaveral are between 28-5° and 51°, and from Vandenberg between 63° to 145°. Thirty-six Deltas have been launched from Vandenberg, starting with the launch of Essa III by Delta 41 in October 1966. Production and assembly The Delta II programme has also included production improvements. In April 1987 final assembly was moved from Huntington Beach, California, which. employs some 1,200 MDC workers, to Pueblo, Colorado, which employs about 200. More than 80 per cent of Delta II production remains at Hunt ington Beach, including components, sub assemblies, electronics, and the interstage. Following final assembly at Pueblo, the vehicles are shipped to either Cape Canaveral or Vandenberg for integration and launch processing. There have been improvements to the two-pad Launch Complex 17 at Cape Canaveral, which has an MDC launch team of about 200. The Delta II first stage incorporates a Rocketdyne RS-27 main engine, burning 96,500kg of RP-1 fuel and liquid oxygen propellants, which are stored in cylindrical isogrid tanks. The engine has a turbine/ turbopump as well as a regeneratively cooled thrust chamber and a nozzle which is hydraulically gimballed for pitch and yaw control. Two Rocketdyne LR101-NA-11 vernier engines provide roll control. The first-stage centrebody houses control elec-, tronics, ordnance sequencing equipment, and telemetry. Nine solid-rocket motors augment first- stage thrust, six being ignited at lift-off and the remaining three during flight. With the nine boosters the lift-off thrust of the 6925 is 36 FLIGHT INTERNATIONAL, 7 January 1989
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