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A Delta III rocket
|Function||Orbital launch vehicle|
|Country of origin||United States|
|Height||35 m (114 ft)|
|Diameter||4 m (13.1 ft)|
|Mass||301,450 kg (664,580 lb)|
|Payload to LEO||8,290 kg (18,280 lb)|
|3,810 kg (8,390 lb)|
|Launch sites||SLC-17, Cape Canaveral|
|First flight||August 27, 1998|
|Last flight||August 23, 2000|
|Boosters (Stage 0)|
|No. boosters||9 Nº|
|Engines||1 GEM 46|
|Thrust||628.3 kN (141,250 lbf)|
|Specific impulse||273 s (2.68 kN·s/kg) (sea level)|
|Burn time||75 seconds|
|Engines||1 Rocketdyne RS-27A|
|Thrust||1085.79 kN (244,094 lbf)|
|Specific impulse||254 s (2.49 kN·s/kg) (sea level)|
|Burn time||320 seconds|
|Engines||1 Pratt & Whitney RL10B|
|Thrust||110.03 kN (24,736 lbf)|
|Specific impulse||462 s (4.53 kN·s/kg)|
|Burn time||700 seconds|
The Delta III rocket was an expendable launch vehicle made by Boeing. The first Delta III launch was on August 26, 1998. Of its three flights, the first two were failures, and the third, though declared successful, reached the low end of its targeted orbit range and carried only a dummy (inert) payload. Delta III had the capability to deliver 8,400 pounds (3,800 kilograms) of cargo to geostationary transfer orbit, twice the payload of its predecessor in the Delta rocket family, the Delta II.[not verified in body]
Throughout the 1990s, satellite masses were growing steadily. It was apparent that the Delta II could not lift many upcoming payloads. In addition, the Delta was a relatively complex launch vehicle, designed for mission flexibility and low development costs rather than low operating cost. Boeing felt the need to maintain market position, through increased capacity, more competitive pricing, and expedited launch-site operations.
Delta Flight 259: The inaugural launch on 26 August 1998 from Cape Canaveral Air Force Station ended in failure, when software adapted from the Delta II caused a guidance failure during first-stage flight. The failure and subsequent vehicle motion depleted the hydraulic fluid used for steering. Upon loss of control, the vehicle was destroyed. The Galaxy X satellite (Hughes HS601 HP type) crashed in the Atlantic Ocean.
Delta Flight 269: The second launch on 4 May 1999, also from Cape Canaveral, also ended in failure. The second stage engine experienced a pressure anomaly and rupture, and shut down while its second burn was underway. The Orion 3 satellite (Hughes HS601 model) was stranded in a useless orbit.
Delta Flight 280: The third and final flight was 23 August 2000, and launched the DM-F3 payload. This was a dummy payload designed to mimic an HS601 communications satellite, and equipped with sensors to monitor vehicle characteristics. Final orbit was slightly low (180.76 x 20,694 km x 27.5 deg. versus a planned 185 x 23,404 km), but the orbit apogee was within the allowable 3,000 km margin of error allowing Boeing to declare the flight a success. However, with the combined factors of a declining satellite launch market, low customer confidence following the two consecutive failures, and the advent of Boeing's new Delta IV, this would prove to be the Delta III's final launch campaign.
The Delta III had the kerosene/oxygen first stage of a Delta II. However, the complex and less-efficient stack of upper stages was replaced with a more advanced hydrogen/oxygen stage. The boosters were noticeably larger. The new fairing fit larger payloads; the first stage was modified to accommodate the larger stack.
The upper stage burned high-performance cryogenic fuel in a proven Pratt & Whitney RL10 engine design. The liquid-hydrogen tank was 4 meters in diameter, covered in insulation derived from that of the Space Shuttle External Tank, and built by Mitsubishi Heavy Industries. The separate liquid-oxygen tank retained the 2.4 m diameter of previous Deltas. Both were structurally stable.[clarification needed] The RL10 engine, from the Centaur upper stage, was in the new RL10B-2 configuration, with an extending nozzle. The nozzle fit in the vehicle stack for launch, then extended in space to increase expansion ratio and improve efficiency. The extending segments were uncooled carbon composites, made by SEP of France.
The solid rocket boosters were Alliant GEM-46s, sometimes referred to as GEM LDXL (Large Diameter Extended Length). These were 14.7 meters length and 1.17 m (46 inches) in diameter, versus 13 meters and 1.01 m (40 inches) for the GEMs on Delta II. Six were ignited on the launch pad, three were lit in flight. To maintain steering authority, three of the boosters had vectoring nozzles.
To keep the vehicle at a reasonable length and avoid steering problems in high-altitude crosswinds, the first stage was shortened. The kerosene (RP-1) fuel tank, formerly 8 feet in diameter like the liquid oxygen tank, was a squat 4 meters, like the hydrogen tank. It too was made by Mitsubishi Heavy Industries. The new length also minimized changes to the launch tower.
In keeping with the 4-digit designation system from earlier Delta rockets, the Delta III is technically referred to as the Delta 8930.
Overall, payload to GTO (Geostationary-Transfer Orbit) was doubled versus the Delta II, with reasonable program costs and streamlined operations. However, the consecutive failures of the initial Delta IIIs, combined with the more-advanced Delta IV program and the successful Sea Launch venture, left the Delta III as an interim vehicle. However, technologies and components from the Delta III contributed to the development of the Delta IV.
- "Delta 3 Rocket Falls Short, but Still a Success Boeing Says", SpaceFlightNow, 8-24-2000, http://spaceflightnow.com/delta/d280/000824loworbit.html