...How you cannot grasp simple fundamentals that apply to all the thousands of satellites, interplanetary probes and manned flights into space........is just baffling...
On the previous page I posted a comparison to a battleship pulling up alongside an aircraft carrier and being lashed to it while they were both travelling at 30 knots.
I now think that was an inaccurate comparison. I'm wondering if Mr Bjorkman is still applying a nautical model of propulsion and steering to spacecraft.
In other words, imagine you have a ship travelling along at 5 knots on a course of 90 degrees (that is, to the east). Now imagine you want the ship to maintain that course and speed, but travel stern first. What would you do? You'd order the ship to do a 180 degree turn, then put the engines in reverse. At the instant the ship completes the turn it's travelling at 5 knots on a course of 270 degrees (possibly slower thanks to the turn). It then slows down, stops, and then picks up speed in the reverse direction (course 90 degrees) until it's travelling at 5 knots again.
I think Mr Bjorkman is expecting that the CSM has to do something similar to undertake the Transposition and Docking maneuver.
Take the example above and now imagine you have two ships, one right behind the other, travelling at 5 knots on a course of 90 degrees. You now want the front ship to reverse its facing and instead travel stern first, such that it's facing the second ship bow to bow. What would you do now? The lead ship would have to increase speed and head off at an angle (say, a course of 60 degrees) until you were a few miles away. That would give you enough room and time to circle around until you were directly in front of the second ship, slow down, stop and then accelerate in reverse, while the second ship maintained its speed and heading. If the second ship couldn't alter its speed or heading, then all the adjustments would need to be made by the first ship while it was reversing, until it could take up station bow to bow with the second ship.
But in space, direction of facing and direction of travel are completely decoupled: changing the direction the spacecraft is
facing has absolutely no effect on the direction it's
travelling.
Hence the reason I like to use the example of the shopping trolley (as long as it has four unlocked wheels) as an analogy for the motion of a spacecraft. I can push the shopping trolley in such a way that it completes a 360 degree rotation while it maintains a fixed distance in front of me (much to the delight of my sons).
