An advanced unmanned weapons platform envisioned by the United States Defense Advanced Research Administration (DARPA) as a response to the changing face of international conflict.
The HCV will be designed and constructed under DARPA's open (for now) Force Application and Launch from the Continental United States (FALCON) program. The goal of the project is to develop an unmanned hypersonic aircraft that can launch (cheaply) from a runway in the Continental United States and deliver 12,000 lbs (5,500 kg) of precision munitions to a target 9,000 miles (14,500 km) distant in about 2 hours, and then return safely.
It is expected that this aircraft will be based on recent NASA hypersonic vehicles, notably the X-33 and the X-45, and will likely involve some sort of scramjet and aerospike technology. The expected cruising altitude is around 100,000 ft, very near the fuzzy edge of space. The most interesting munition to be carried by the HCV is the Common Aero Vehicle (CAV), which is essentially a 1,000 lb guided rock thrown from space onto a target. Once released, it can travel up to 3,000 additional miles and strike a target within 3 meters. Its tiny capacity is not expected to be a problem due to the tremendous force with which it will strike its target.
This likely sounds like yet another Popular Mechanics-esque X-plane that will never see the light of day, and to be fair, that's probably true. However, it does highlight the Pentagon's major concerns for the coming decades. In recent years, the United States has faced increasing threats from tiny, highly mobile adversaries operating deep inside very unfriendly territory. This situation is complicated by a recent breakdown in American foreign policy in which even closely allied countries are no longer supporting their every move. This makes it extremely difficult to secure bases of operation near enough to the threats in order to apply enough power in a sufficiently rapid manner in order to neutralize them. A case in point would be the most recent Iraq War, in which the war effort on the entire northern front was almost completely hobbled by America's inability to buy troop access through Turkey with love, money, or Big Macs.
The problem is in the ability to project power and the time that it takes to project said power. An aircraft carrier provides a good example. A modern, nuclear powered Nimitz class aircraft carrier can project power for hundreds of miles in any direction, and is relatively unfettered by regional politics. However, they move around very slowly (on the order of 30-35 knots) and are thus unable to respond to time-critical threats unless they are already in the area (and time-critical threats tend to avoid carrier battle groups). A forward base of operations can project power even farther, but they are not mobile at all and in the present political climate, almost impossible for the United States to secure on a timely basis. Both of these power centers also have the disadvantage of operating within striking distance of the enemy, bringing up the very real and increasingly unacceptable possibility of American casualties.
The FALCON Program seeks to end this problem. The official DARPA line is "The intent is to hold adversary vital interests at risk at all times, counter anti-access threats, serve as a halt-phase shock force and conduct suppression of enemy air-defense and lethal strike missions as part of integrated strategic campaigns in the 21st Century." Essentially, the HCV would allow the United States to strike any point of the face of planet with near-pinpoint accuracy in less than two hours without asking permission first.
For example, the United States gets a hot tip that our friend Osama bin Laden is hanging out at a villa in central Pakistan. A satellite is vectored in, and surveillance shows evidence of the massive dialysis machine that he has to lug around so that he doesn't immediately die of chronic kidney failure. With the present equipment and political climate, it would be impossible for the United States to even reach him before he moved again, and the entire point would be moot because there is absolutely no way that they would be able to secure the necessary overflight and strike permissions from all of the nations involved. However, with an HCV, once the satellite intel comes back, the US can launch the plane and two hours later there's a meteor falling out of sky with 1,000 lbs of high explosives and a personal greeting card from Dubya. The plane then turns around and returns to base, without even the possibilty of an American casualty
For more info see:
The DARPA Page