By this I mean, what percentage hit their tagets, what is the CEP, etc?
I have a video on the history of air power, and it describes how many sorties and bombs dropped were required to destroy bridges in the Vietnam war with the old “dumb bombs”. The hit rate was in the low single-digit percentage.
I remember another statistic from the Second Persian Gulf War (Desert Storm - I insist on calling it by its proper name) that 70% of the smart bombs (laser-guided, some TV guided) missed their target, but that this was still far better than the old dumb bombs. The images we saw on CNN being carefully selected.
What about the new JDAMS and other new generations of smart bombs?
The guidance systems have gotten accurate enought that the military is now strapping it onto concrete dummy bombs, and dropping those on targets, to reduce collateral damage, and allow its use closer to friendly troops. These guided chunks of concrete are occasionally referred to as “smart rocks.”
I think the actual information is probably classified (or maybe not if they really want to scare someone). Anyway, the technology we have now is light years away from what we had in the first Gulf War and that was another light year from Vietnam. Regular GPS with accuracy down to a couple of meters is available to everyone and the military certainly has ways to achieve accuracy better that that. It is merely a technical problem after those things are in place to build missiles that can fly through windows. I would be very disappointed in the U.S. military if they can’t achieve consistent sub-meter accuracy at this point.
Can you tell the GPS location of the bridge or what not that you are looking at in the satellite photo accurately, or do you need to be standing on it to take a good reading of where you are? Seems to me that the GPS system does the calculation in the unit at the location based on the satellites’ signals, so can you run the system in reverse and get the location that you want to bomb remotely?
But accuracy in a receiver sitting still is one thing. In a bomb that has had to continually update its location since the plane took off, wouldn’t that increase the potential for error?
Plus, when the bomb has been released, it is still dependent on the fins of the bomb to adjust its course and direct its path to the target. That must introduce an additional degree of unreliability.
Some smart missiles are way more smart than that though. They use GPS when they need to but they also use AI stuff that allows them to follow the contour of the land and then identify a target by sight including going in a window if they need to. I know I saw a video that was taken out of the nose of one of those things. It was pretty striking.
[nitpick] Ah guys, many if not most smart bombs do use GPS but rather home in on a infrared laser beam that ‘paints’ where they want the bomb to land. The laser can be run by ground troops, a spotter aircraft, or the attack aircraft itself.
TLAM (Tomahawk land attack missile) and the like use GPS, but these are not bombs. They are missiles.[/nitpick]
Good accuracy numbers are probably going to be hard to come by, since military operations tend to be insanely controversial, not to mention subject to being classified. The military has a variety of options when it comes to “smart bombs.” They can use ones that are controlled by GPS systems, laser guided, wire guided, video guided (i.e. some guy watches video taken by a camera in the nose cone and controls the bomb), image guided (the bomb/missile is programmed with an image of what the target looks like and the onboard AI guides it in), and radio guided, to name the ones that I can think of. Some can even use a combination of those things to find the target. Each individual system has it’s flaws, as well. Laser guided weapons don’t work too well in bad weather, radio/radar guided ones can be jammed, somebody can punch in the wrong GPS coordinates, etc.
The troops on the ground who radio the GPS coordinates up to the planes who’re going to be dropping the bombs don’t have to be directly in the target area. Presumably, they either have maps and math formulas by which they can figure out the correct coordinates or they have survey type equipment which allows them to find the coordinates of the bridge or whatever they want blown up, without sending a human into a hazardous area.
That’s not a nitpick. I clearly distinguished between laser-guided bombs and satguided bombs (the new JDAMS). Those are, in fact, bombs that use GPS for guidance.
Soldiers these days have GPS binoculars with built in laser range finders - it can automatically calculate the GPS coordinates of the target by measuring the distance/direction from the GPS coordinates of the binoculars.
Accuracy numbers for non-classified weapons systems, like laser-guided gravity bombs and JDAMS, are not hard to get - for example JDAMS has a CEP of 13 meters in GPS mode, and 28 meters in inertial navigation mode. What is harder to find, and somewhat controversial is not the accuracy, but the reliability. A small but significant percentage of these bombs suffer some kind of malfunction - they go out of control, target the wrong place, or just fall in an unguided mode. When they work right (i.e., most of the time) they are incredibly accurate. So much so that the move is to the Small Diameter Bomb, now in development. If you can hit the right place reliably, you can use smaller bombs for the same result.
I have no doubt that weapons systems with accuracy under a meter are in development, but they are not being fielded yet.
I assume you meant to say do not use GPS, that makes sense in your context. I don’t think your statement as I read it is correct though. I certainly don’t know the current percentages, but the JDAM kits are cheaper than the active guidence systems that use laser or video guidence and at least as accurate. I assume that they are by now more often used than the older active guidence weapons.
Tomahawk cruise missiles use terrain following guidence systems. At least in the old days they did. I don’t know what they use now. Probably a combination of systems. But I am reasonably certain that terrain guidence systems using downward looking radar is still an important part of the the system.
Not an ignorant question at all, actually. The government is continually looking to improve satellite photo “registration”. This is the process of moving satellite photos so that coordinates in them are more accurate. Allow me to describe how this works. For the example that follows, I will be referring to the unclassified Quickbird satellite run by Digital Globe, but you can use your imagination to figure out how this would apply in a more military setting.
First, the satellite tries to figure out its exact position and orientation relative to the earth via a combination of calculations. Orbits are fairly predictable, so it can just use its previous trajectory to get a good idea of where it is currently. Ground stations can also triangulate the satellite’s position from its radio signal. The satellite then checks its internal “gyroscopes” (these are actually solid state devices, similar to what keeps a Segway upright) to figure out how it is rotated. (The Ikonos satellite run by Space Imaging has very accurate gyroscopes that give a very precise reading. Quickbird’s gyroscopes are actually a bit less reliable and can be off by quite a bit). It can also take a picture of the stars in the sky, and use that to double check its orientation. The positions of prominent stars in the picture are determined, and this can be used to figure out which way the satellite is pointing.
Once the satellite photo is taken, it is transmitted back to earth along with a best guess at where on the ground it is. These raw images can still be anywhere from 15 to 50 meters off (for Quickbird imagery), so further refinement is needed. They can be compared with other satellite photos and moved until they all line up, which can improve the accuracy somewhat. If the exact coordinates of a prominent feature in the photo are known, (for example, an intersection of runway lines on an airport) then much greater accuracy is possible. Accurate elevation data must also be used, in order to properly “drape” the imagery over the surface of the earth. This elevation data can come from previous surveys done on the ground. More commonly, it can be generated by comparing two satellite photos taken of the same area from different angles, which gives a stereo view of the area.
Once all that is done, meter and sub meter accuracy is quite possible. Of course, it is now up to skilled imagery analysts to be able to tell what is a military target from above.