Sea Launch loses ICOs satellite

On 13 March 2000, after two successes, Sea Launch had its first loss. The launch got off to a good start, with the first stage of the Zenit 3SL separating at T+145 seconds and the shroud jettisoning 32 seconds later, but contact was lost 2 minutes short of the end of the second stage's 6.5-minute burn. The earlier launches had been due east along the equator in order to achieve geosynchronous transfer orbit, but with the ICO F1 satellite heading for a medium orbit at 10,600 kilometres inclined at 45 degrees to the equator the debris fell into the sea several hundred kilometres from the Chilean coast. As there were no tracking stations along this flight path, telemetry was relayed via one of NASA's TDRS satellites. The initial focus of the investigation concerned the verniers that steered the second stage. These burned the same propellants as the main RD-120 four-chamber engine, with all four thrusters being fed by a single turbopump.9^96 It was discovered that the flight control system shut down the engine at T + 450 seconds after it had sensed that the vehicle was not functioning properly. The theory was that a computer error just after lift-off had allowed a pressure valve to remain open, causing the verniers to either misfire or fail to fire. Sea Launch said that it was more likely to have been a software error than a hardware fault, and later added that it had "strong evidence'' that the cause was a software error on the ground that failed to command a valve to close in a pneumatic system that performed several functions, including vectoring the engine.97 Telemetry indicated that this system had lost 60 per cent of its pressure, leading to a significant deviation in attitude (through the inability to gimbal the engines) which in turn had triggered the self-destruct system. Ironically, this occurred just short of the scheduled end of the second stage's burn, so it had almost made it. ICO had booked its second satellite on the Delta III, but after this vehicle suffered two successive failures ICO withdrew its satellite to

Preparing the ICO F1 satellite.

A Sea Launch Zenit 3SL lifts off on 28 June 2004 with Telstar 18.

await a successful demonstration flight.98

Sea Launch made its return to flight by launching PanAmSat 9 on 28 July 2000, and followed this with a long run of successes.99 However, the rate of launches was less than expected because the Zenit 3SL had to be stood down whenever the Block-DM stage of a Proton malfunctioned.100 As a result, the company was not operating profitably -indeed, it had yet to recoup its startup cost.101 On 28 June 2004 the early shutdown of the Block-DM of a Zenit 3SL stranded Telstar 18 in a transfer orbit with an apogee that fell short of geosynchronous altitude. However, the Loral 1300 series satellite had been loaded with such a margin of propellant for station-keeping that it was able to reach its operating position without undermining its 13-year nominal operating life.102 The three-month-long investigation concluded that a wiring problem on the Block-DM triggered a short that induced electrical interference in the circuitry carrying data on the propellant flow rates to the control system, causing this to consume fuel more rapidly than planned, resulting in an early shutdown when the tank ran dry.103 Sea Launch postponed its next mission to early 2005.

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