Dec 20, 2011

Breaking, Descent and Landing


Now here is where the fun really begins, it's not every day you land a robot on the moon! The Breaking Stage solid motor is used to reduce the spacecraft's speed on its approach. The direct descent landing trajectory chosen means the Lander can touch down just after lunar dawn allowing the maximum amount of time to complete the mission but also requires the timing of this burn to be very precise. To achieve this precision an on-board timer is used to trigger the ignition when the Lander passes through a specific lunar altitude. After the Lander separates from the Breaking Stage it follows a gravity turn trajectory (illustrated in the image) to the surface using its own rocket engine to control its descent. During the final approach to touchdown the Lander determines its altitude and vertical velocity using a small radar altimeter and its horizontal velocity by a landing camera coupled with the altimeter and rate gyros. Finally, after travelling a quarter of a million miles, the Lander touches down on the moon's surface and prepares to deploy the Rover and complete the GLXP mission.

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