How does a cruise missile know where to go?
In: Technology
Maps and cameras!
Depends on the particular missile, but it probably has GPS, an inertial guidance system and a terrain matching camera. It has a microprocessor onboard with a flight plan, waypoints and a map of the area and it flies the programmed route.
It might also have some other back-up systems or be steerable remotely.
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There are lots of fancy systems as mentioned in other posts… including GPS, but the main component is the same as any other flying odject (include the ones that took us to the moon and back)… IGS or Inertial Guidence System.
Basically it is a bunch of gyroscopes connected to measuring devices and a simple computer. You program in where it is starting from, and where it is going to, and its weight and so on… and then you let it rip. The IGS can tell by the amount force excerted in every direction and for how long, exactly how far the missile has travelled and in what direction. To give you an idea of how accurate it is… back in the 60’s when it was developed, the very first test flight went from New York to LA with the windows blacked out and no other method of nav on board, and when they thought they were close they pulled off the curtains and found themselves within a couple of miles of LAX. Obviously it has improved since then.
The Cruise has another system that uses radar etc for tracking the profile of the ground so that it can fly really low… and a third system using cameras to track the target right at the end which they can use for both stationary and moving targets.
The missile knows where it is at all times.
It knows this because it know 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 that 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 isn’t. If variation is considered to be a significant factor, it, too, may be corrected by the GEA. However, the missile must also know where it was. The missile guidance computer 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 algebraic sum of where it shouldn’t be and where it was, it is able to obtain the deviation and its variation, which is called error.
I just use the joystick, bit remember to lay down somewhere safe first, don’t want to ruin that killstreak!
As a point of trivia, the original cruise missile (the V1 “Flying bomb”) had a little propeller that spun until it reached a pre-set number of spins (like an alarm clock) at which point the whole thing just pitched down.
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