After two successive failures, the Boeing Delta 3 (8930) rocket had a less than totally successful third flight as it placed its DM-F3 dummy payload into a transfer orbit approximately 2,700 km short of its already revised planned apogee.
The rocket had been flying a ‘dummy’ instrumented payload after failing to find a satellite to fly on the rocket which was perceived as being unproven. The launch occurred from Cape Canaveral at 11:05 GMT on 23rd August 2000 and had seemed to have gone well. However when the payload and upper stage orbits were tracked they were found to be 2,700 km short of the apogee of the intended orbit. The achieved orbit of 179.5 km perigee, 20,694 km apogee at 27.62 degrees inclination compared poorly with a planned orbit apogee of 23,378 km (the target apogee had been adjusted down from 25,408 km due to adverse atmospheric conditions, head winds, increased weights, etc).
The flight used a ‘burn to depletion’ technique which is known to be less accurate than a more normal commanded shutdown method. Despite this error, Boeing has stated that the payload was left just within the three sigma (standard deviation) limits of the target orbit and are therefore claiming the flight as a ‘success’. The company states further that if a live commercial satellite had been flown as a payload then it would have been unlikely that it would have had to use its own fuel to make up the shortfall. This is because, Boeing says, the liquid apogee motor a satellite carries for final orbital insertion would have had enough of a contingency to cope with the under-performance, as this reserve is usually designed to overcome errors within the three sigma accuracy limit of the rocket.
With the more normal commanded shut down method commercial GTO-(geosynchronous transfer orbit) capable rockets usually have three sigma limits of around plus or minus 120-150 km. Analysts have suggested that this three sigma limit at plus or minus 3,000 km may have been too great a margin to have been carried as a reserve for an apogee motor.
As such they suggest that, in the case of a real satellite, on-board thruster fuel may have had to be used to achieve the planned final orbit. This may have affected the life span of a satellite and as such may have resulted in an insurance claim for loss of life. Having had two previous failures with the rocket, Boeing disclosed that it was unable to find a willing paying passenger able to fly in time. However, to put the programme back on track it decided to pay for a demonstration flight of the rocket which carried an instrumented ‘dummy’ payload.
This demonstration flight was designed to reassure potential customers and insurers of the reliability of the rocket. The rocket’s maiden flight in 1998 ended after it was seen to explode just over a minute into its flight. Roll abnormalities caused the guidance computer/control system to use up all its hydraulic fluid. When the fluid ran out the rocket pitched over after suffering a wind shear. The commercial communications satellite payload Galaxy 10 was lost on the flight.
The second rocket failure occurred last year. The commercial communications satellite, Orion 3, was left in an unusable low Earth orbit after a breach in the second stage engine combustion chamber caused the vehicle to tumble and stop the engine. A new construction method had used brazing of strips covering the seams using silver wire. Air pockets had been left in the brazing. Both previous failures of the Delta 3 resulted in insurance losses.
This latest mishap will not enamour the Delta 3 rocket to potential users or to the insurance market. However, the Delta 3 rocket is regarded as merely an interim version and Boeing may decide to concentrate on the Delta 4 series which is due to fly in 2001. Another flight of the Delta 3 may yet occur but this may be just to test the cryogenic upper stage which is planned for use on the Delta 4M (Medium) rocket. A cancellation of Delta 3 will not prove fatal to the Boeing commercial launch space interests. Boeing still operates the reliable Delta 2 rocket series, and it still has a forty percent stake in the Zenit 3SL (Sea Launch) program which flies commercial satellites to orbit from a converted oil rig. However, in the short term, the real winners will be Boeing’s competitors: ILS partners Lockheed Martin/Khrunichev flying Atlas and Proton rockets, Arianespace flying the Ariane 5.
David Todd is space analyst for Airclaims Ltd.
His columns appear as part of regular updates for subscribers to Airclaims’ Spacetrack® database. Hyperlinks have been added to the original text.
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