It looks like the Pentagon's plans to develop a prescision weapon capable of hitting anywhere on Earth with a conventional warhead in a matter of minutes or hours will remain alive for the time being.
Soon-to-be incoming Pentagon chief Leon Panetta told lawmakers during his confirmation hearings to be Secretary of Defense that he supports the effort to field such a weapon.
From his written testimony via Defense News:
Conventional prompt global strike (CPGS) weapons would provide the nation with a unique conventional capability to strike time-sensitive targets, so that distant, hard-to-reach places will no longer provide sanctuary to adversaries. It is my understanding that the only current prompt global strike capability in the U.S. inventory is a nuclear armed ballistic missile. CPGS would be a valuable option for the President to have at his disposal.Now, the Air Force says that it's not planning on sticking a conventional weapon atop a ballistic missile. The most compelling arguement against doing so is that the rapid launch of an ICBM with little to no warning to other nations (see Russia) could make people think the U.S. was launching some sort of nuclear weapon.
CPGS systems could be useful in scenarios involving regional adversaries considering an attack using weapons of mass destruction or against high-priority non-state adversaries. More broadly, CPGS may be the only systems available in situations where a fleeting, serious threat was located in a region not readily accessible by other means.
So rather than an ICBM, the Air Force may develope hypersonic vehicles that would be booster to around Mach 6 and then use a sramjet-style engine to continue on to the target at such speeds. In fact, the Air Force already looking at ways to weaponize the technology used on its main hypersonic research vehicle, the X-51A Waverider.
However, as Defense News points out, it's unclear if the Pentagon will have the cash on hand to fund such a program in the age of government austerity. Especially since it's going to be competing with new aircraft carrier programs, the F-35 Joint Strike Fighter, the next generation bomber and several new ground vehicle programs.
Speaking of the X-51A, its second test flight happened earlier this week and it was considered, well, "less than successful" after the vehicle's engine refused to fully start. This is the second time in as many flights that the X-51A has seen its test shot cut short.