Delta III

The Delta III rocket was an expendable launch vehicle made by Boeing. The first Delta III launch was on August 26, 1998.[4] 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. The Delta III could deliver up to 8,400 pounds (3,800 kilograms) to geostationary transfer orbit, twice the payload of its predecessor, the Delta II.[1] Under the 4-digit designation system from earlier Delta rockets, the Delta III is classified as the Delta 8930.

This article is about the rocket. For the submarine, see Delta III-class submarine.
Delta III
A Delta III rocket
FunctionOrbital launch vehicle
ManufacturerBoeing
Country of originUnited States
Size
Height35 m (115 ft)
Diameter4 m (13 ft)
Mass301,450 kg (664,580 lb)
Stages2
Capacity
Payload to LEO8,290 kg (18,280 lb)[1]
Payload to GTO3,810 kg (8,400 lb)[1]
Associated rockets
FamilyDelta
Launch history
StatusRetired
Launch sitesSLC-17, Cape Canaveral
Total launches3
Successes0
Failures2
Partial failures1
First flightAugust 26, 1998
Last flightAugust 23, 2000
Boosters
No. boosters9 GEM 46
Thrust628.3 kN (141,200 lbf)
Specific impulse273 seconds (2.68 km/s)
Burn time75 seconds
FuelHTPB mix, similar to PBAN
First stage
Engines1 Rocketdyne RS-27A
Thrust1,085.79 kN (244,100 lbf)
Specific impulse254 seconds (2.49 km/s)
Burn time260 seconds[2]
FuelLOX/RP-1
Second stage
Engines1 Pratt & Whitney RL10B
Thrust110.03 kN (24,740 lbf)
Specific impulse462 seconds (4.53 km/s)[3]
Burn time700 seconds[2]
FuelLOX/LH2
Third stage (Optional)
Motor1 Thiokol Star 48B
Thrust66.723 kN (15,000 lbf)
Specific impulse286 seconds (2.80 km/s)
Burn time87 seconds
FuelHTPB

Description
A Delta III DCSS upper stage undergoing testing at Plum Brook Field Station in January 1998

Like the Delta II, the first stage of the Delta III burned kerosene and liquid oxygen and was powered by one Rocketdyne RS-27A main engine with two vernier engines for roll control.[5] While the propellant load and gross mass of the stage were nearly identical to the Delta II, the diameter of the kerosene tank was increased from 2.4 meters to 4 meters. This reduced the overall length of the vehicle and allowed the Delta III to use the same launch facilities as the Delta II with only minor modifications.[1] First stage thrust was augmented by nine GEM-46 solid rocket boosters, sometimes referred to as GEM LDXL (Large Diameter Extended Length). These were 14.7 meters in length, 1.2 m (46 inches) in diameter, and had a mass of 19 metric tons each, about 6 metric tons more than the Delta II's standard GEM-40 motors. Six were ignited on the launch pad, while the remaining three were ignited just before burnout and separation of the ground-lit boosters. To maintain steering authority, three of the boosters had vectoring nozzles.[1] GEM-46 boosters would later find use on the Delta II, leading to the Delta II Heavy.

The second stage of the Delta III was the newly developed Delta Cryogenic Second Stage (DCSS), which burned liquid hydrogen and liquid oxygen. The liquid hydrogen tank was 4 meters in diameter, while the separate liquid oxygen tank was 2.4 meters in diameter. This stage offered significantly better performance than the Delta II's second stage, the Delta-K, which burns hypergolic propellants.[1] The DCSS was powered by a Pratt & Whitney RL10B-2 engine, derived from the RL10 powering the Centaur upper stage but featuring electromechanical actuators for gimbal control and an extending nozzle for increased specific impulse.[5] After Delta III's retirement, this stage was modified for use as the Delta IV's second stage.[6] The payload fairing was a new composite design, matching the upper stage hydrogen tank at 4 meters diameter and allowing larger payloads than the Delta II's 9.5 or 10 foot fairing. Payload to GTO (Geostationary-Transfer Orbit) was doubled versus the Delta II but the consecutive failures of the initial Delta IIIs, combined with the more-advanced Delta IV program and the continuing success of the Delta II, left the Delta III as an interim vehicle.[3]

Launches

Delta Flight 259: The inaugural launch on August 26, 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.[7] Upon loss of control, the vehicle was destroyed. The Galaxy 10 satellite (Hughes HS601 HP type) was destroyed.[4]

Delta Flight 269: The second launch on May 4, 1999, carrying the Orion 3 satellite (Hughes HS601 model), also ended in failure.[8] The second stage engine experienced a pressure anomaly and rupture, and shut down while its second burn was underway, leaving the payload in a useless orbit.

Delta Flight 280: The third and final flight on August 23, 2000 launched a 4,348 kg (9,586 lb) satellite simulator into a 180.76 × 20,694 km orbit. While the apogee was 2,710 km lower than the targeted 185 × 23,404 km, and somewhat a partial failure,[6] it was within the allowable 3,000 km margin of error and demonstrated the propellant depletion shutdown capability of the DCSS, modified versions of which would become the second stage of the Delta IV.[9]

See also

References
  1. "Delta III Launch Vehicle". 2001. Archived from the original on November 14, 2001.
  2. "Delta III Payload Planner's Guide" (PDF). Archived from the original (PDF) on 19 November 2001.
  3. "Delta III Data Sheet". Space Launch Report. Retrieved 26 July 2014.
  4. "Delta III Takes a Dip". WIRED. Retrieved 2018-10-24.
  5. "Delta 3". Astronautix. Archived from the original on November 12, 2013. Retrieved January 5, 2015.
  6. "Delta 3 Rocket Falls Short, but Still a Success Boeing Says". SpaceFlightNow. August 24, 2000.
  7. "Boeing Changes Delta III Control Software" (Press release). Boeing. October 15, 1998.
  8. Leary, Warren E. "String of Rocket Mishaps Worries Industry". Retrieved 2018-10-24.
  9. "Delta III DM-F3 Mission Book" (PDF). Boeing. Archived from the original (PDF) on 2014-11-24. Retrieved 2015-03-12.

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