The missile knows where it is at all times.

[leeroysphitz]

It knows this because it knows where it isn't. By subtracting where it is from where it isn't or where it isn't from where it is, whichever is greater, it obtains a difference or deviation.

The guidance subsystem uses deviations to generate corrective commands to drive the missile from a position where it is to a position where it isn't and arriving at a position where it wasn't it now is.

Consequently the position where it is is now the position where it wasn't and it follows that the position that it was is now the position that it isn't.

In the event that the position that it is in is not the position that it wasn't the system has acquired a variation. The variation being the difference between where the missile is and where it wasn't.

If variation is considered to be a significant factor it too may be corrected. However the missile must also know where it was.

This scenario works as follows: Because a variation has modified some of the information the missile has obtained it is not sure just where it is. However it is sure where it isn't , within reason, and it knows where it was. It now subtracts where it should be from where it wasn't or vice versa and by differentiating this from the sum of where it shouldn't be and where it was it is able to obtain the deviation and it's variation which is called "error".

[kentauros]

1. Where It Is

http://www.archive.org/download/wh003/wh003_12_whereitis.mp3

or use the imbedded player here: http://www.archive.org/details/wh003

:D

[leeroysphitz]

4. MBM version.

http://www.youtube.com/watch?v=EHi9HsuKBk0

[hobbit709]

2. The classic instructions

"For technical reasons these warheads must be stored upside down. That is with the top at the bottom and the bottom at the top. In order that there is no mistake in storing, the bottom will be clearly marked 'TOP'"

[leeroysphitz]

3. What could go wrong? n/t