The XLs debut

OSC's more powerful Pegasus XL was longer than the original, to accommodate 24 per cent more propellant in the first stage and 30 per cent in the second stage. The third stage was unchanged. The 60 per cent overall increase in performance was to enable it to insert 340 kilograms into a circular orbit at an altitude of 740 kilometres. Its introduction on 27 June 1994 also marked the first use of the Lockheed L-1011 Tristar, 'Stargazer', which had been bought from Air Canada and modified to carry the rocket on its belly.16 In fact, the B-52 could not carry the stretched form of the launch vehi

The L-1011 'Stargazer' with a Pegasus mounted on its belly.

cle.17 However, at T+75 seconds, several seconds after the second stage ignited, the rocket veered off course and lost speed, prompting the safety officer to destroy it.18 The investigation revealed that the vehicle suffered an anomalous roll due to sideslip, also referred to as 'phantom yaw', derived from inadequacies in the aerodynamic model used to design the new configuration, which relied on computer simulations without verification by wind tunnel tests.19 The flight control software was revised to counter this disturbance.

The Orbcomm satellites were designed to be stacked on the nose of a Pegasus.

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