|Space Launch Report: Delta III Data Sheet|
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Boeing's Delta III was an uprated version of the Thor-Delta series. It flew several years before the company's Delta IV Evolved Expendable Launch Vehicle (EELV) was ready to enter service. Although Delta III failed commercially, it succeeded in testing the Delta IV liquid hydrogen (LH2) upper stage.
Delta III was an 8930 model under Boeing's four-digit numbering system. The rocket used an 8000-series Thor first stage with a Rocketdyne RS-27A main engine and a 4 meter diameter kerosene tank mounted on top of the standard 2.4 meter diameter liquid oxygen (LOX) tank. Nine upgraded Alliant Graphite Epoxy SRMs (GEM-46) augmented the first stage thrust. Six of the SRMs ignited on the pad. Three of the ground-lit SRM had thrust vector control steering nozzles. The remaining three SRMs ignited in the air after the first six burned out. The rocket's second stage was a new 4 meter diameter LH2/LOX unit powered by a single Pratt & Whitney RL10B-2 engine.
Delta III was designed to boost 3.8 metric tons to geosynchronous transfer orbit (GTO) or 8.3 tons to low earth orbit (LEO). Only one launch site, Cape Canaveral Space Launch Complex 17B, was adapted for Delta III.
McDonnell Douglas initiated Delta III several years before the company was merged into Boeing. Some Delta III technology was subsequently adopted for Delta IV. When Delta IV development was approved, Delta III was effectively made obsolete.
The first Delta III, Delta 259 with PanAmSat's $225 million Galaxy 10 communications satellite, failed about 75 seconds after its August 27, 1998 liftoff, just before the ground lit SRMs were to be jettisoned. The rocket's guidance system had not been properly designed to handle all possible SRM steering modes. As a result, the rocket began to suffer roll oscillations about 55 seconds after liftoff when hydraulic fluid supplies in the three thrust vector control SRMs ran dry. The rocket pitched over and broke apart, its final destruction ensured by a range safety destruct signal.
The second Delta III mission, Delta 269 with the $145 million Orion 3 comsat, also ended in failure after a May 5, 1999 launch. This time the rocket was stranded in a low parking orbit when its second stage RL10B-2 engine failed to restart. The engine's combustion chamber burst during the restart due to a manufacturing defect in a welded reinforcing strip.
A collapsing commercial satellite market, combined with concerns about Delta III's reliability, forced Boeing to fly the third Delta III with a dummy payload on August 23, 2000. The main intent of the flight was to qualify the second stage for use by Delta IV. This time, flying as Delta 280, the rocket succeeded, but the second stage slighty underperformed so that the payload just barely made it into the planned subsynchronous transfer orbit.
After Delta 280, Boeing quietly shut down Delta III production, reassigning Delta III hardware to the Delta II-Heavy and Delta IV programs.
Delta III Payload Planners Guide, April 1996
Last Update: September 5, 2010