Posted by: Paul M
« on: March 04, 2010, 02:49:58 AM »The simplest way to think of this is to remember that what you are picking up is just the reflection from the target. So for general purposes of detecting something is there you can survive with a long wave length system. As you just basically want to know that something is there, that it is at range x, and with a few rotations of your antenna is moving at velocity y. However to accurate guide a weapon to that target you need to have very accurate information on where it is, especially for a target such as an inbound missile with a small radar cross section, in this case you need a short wave length radar with a more or less fixed dish and probably it works better with multiple antennas but I'm not in the know of that.
Passive systems work by detecting emissions, and beyond the small detail that Steve skips of light lag, are generally far less exact. But in reality stealth in space would be hard since your crew needs at least 300 K to stay alive, and your power systems need to dump massive quantities of heat. That makes you an IR target of truly astounding proportions compared to the background (3 K). A working ship probably also emits on a variety of radio bands as well due to all the AC systems, what we in science call 50 Hz or 60 Hz noise.
Radar and Ladar (or Lidar) systems can also hull map a target. This is a high resolution targeting scan to pick points to fire beam weapons. It would be a step up from purely active scanning to clear hostile targeting.
The other thing to keep in mind is that over the missile flight time the ship you are targeting can move considerable distances. If you didn't have a constant lock on them, and feed constant course corrections to your missiles, the chance to hit would be close to zilch, even if the missile had active terminal guidance. The maximum range of a beam weapon excluding focusing effects, or a mass driver type weapon is given by the ships size (radius for a sphere which makes that calculation simple), the velocity of the centre of mass and the weapon transit time and velocity.
Passive systems work by detecting emissions, and beyond the small detail that Steve skips of light lag, are generally far less exact. But in reality stealth in space would be hard since your crew needs at least 300 K to stay alive, and your power systems need to dump massive quantities of heat. That makes you an IR target of truly astounding proportions compared to the background (3 K). A working ship probably also emits on a variety of radio bands as well due to all the AC systems, what we in science call 50 Hz or 60 Hz noise.
Radar and Ladar (or Lidar) systems can also hull map a target. This is a high resolution targeting scan to pick points to fire beam weapons. It would be a step up from purely active scanning to clear hostile targeting.
The other thing to keep in mind is that over the missile flight time the ship you are targeting can move considerable distances. If you didn't have a constant lock on them, and feed constant course corrections to your missiles, the chance to hit would be close to zilch, even if the missile had active terminal guidance. The maximum range of a beam weapon excluding focusing effects, or a mass driver type weapon is given by the ships size (radius for a sphere which makes that calculation simple), the velocity of the centre of mass and the weapon transit time and velocity.
. If you want some basic background, check out the wiki page for Radar: 