Subj : Re: Kerosene Engines To : All From : Charles Radley Date : Thu Jul 20 2000 11:24 pm From: Charles Radley -=> Andrey Kanunnikov wrote to Charles Radley <=- AK> Hello, Charles! AK> Sunday July 16 2000 10:53, Charles Radley wrote to Andrey Kanunnikov: CR> For autonomous attitude control the interplanetary probes use a CR> combination of gyros, star sensors and sun sensors. CR> Sensors of the star Canopus are popular, because Canopus is a very CR> bright star at 90 degress to the ecliptic (solar system plane). AK> But how does the star sensor determine what the star is it watching? There is a series of aquisition rotations. First the spacraft acquires the Sun, this is the brightest object in the sky. We know in advance the angle betwen Canopus and the Sun, it is always approximately 90 degrees (slightly less). The spacecraft rotates about the Sun axis until a bright star appears in the field of view. There is only one bright star approximately 90 degrees to the Sun, so we know that it is Canopus. CR> For trajectory control, it is tracked by radar transponder, CR> mid-course correction manouvers are calculated by specialists at a CR> control center, and rocket burns are executed on control center CR> command. AK> This scheme of control is well when the space shuttle is AK> operated simultaneously. But what will happend if the AK> trajectory changed unexpected? AK> Time delay between signal transmitted to the Earth and recieved is to AK> long. Andrey, the method I described was not for the Space Shuttle, it was for interplanetary craft. The Space Shuttle uses on board inertial navigation methods, a closed loop feedback control system, using multiple real-time computers. There is no human involved, except to program the computers prior to the launch. Take care, Charles R. ... Assistant Moderator, SPACE & the 8 "SB-" prefixed echoes ___ MultiMail/MS-DOS v0.32 --- Internet Rex 2.23 * Origin: The gateway at The Region 23 Internet Source (2:236/205.777) .