The U.S. Air Forces X-45A combat UAV (UCAV, or unmanned combat air vehicle) dropped its first smart bomb on April 19th. During the test, the X-45 was flying at 35,000 feet, moving at about 700 kilometers an hour and operating under the control of onboard software. The bomb dropped was an SDB (Small Diameter Bomb), a new type of smart bomb that weighs only 250 pounds (and is six inches in diameter and six feet long). A human operator on the ground authorized the release of the bomb when the X-45 signaled that it was within range. The bomb, which carried no explosives, hit the target (that is, landed within a 30 feet of it, as GPS guided bombs are supposed to do.) 

The current version of the X-45 (the X-45A) is for development only, and has flown several dozen times. A larger version, the X-45C, will begin flight testing in two years and eventually enter service. The X-45C will weigh 19 tons, have a 2.2 ton payload and be 39 feet long (with a 49 foot wingspan.) The X-45A is 27 feet long, has a wingspan of 34 feet and has a payload of 1.2 tons. The X-45C will be able to hit targets 2,300 kilometers away and be used for bombing and reconnaissance missions. Each X-45C will probably cost about $30 million and will be able to carry up to 24 SDBs. These bombs are carried internally, to maintain the UCAV's stealthy profile. The aircraft can also carry air-to-air missiles, but the testing of the UCAVs for air-to-air combat is not planned in the near future (next five years or so.) That is, unless some other country starts mucking about with this sort of thing. UCAVs fighting each other is technically possible, but the pilots who run the air force don't like the idea of fighting robots.

The X-45C is a spin-off from the X-45B project, which was dropped last year when it was decided to design a UCAV that met both air force and navy needs. This became the X-45C. The navy model will will be different than the air force one (mainly in the usual ways; stronger landing gear for carrier landings, better resistance to salt water corrosion and sensors optimized for finding ships at sea.)