The U.S. Missile Defense Agency is refining some advanced concepts for the SM-3 interceptor to attack intercontinental ballistic missiles.

These include designs for lighter weight kill vehicles, and possibly a new propulsion system for the kill vehicle as well as the missile’s upper stage.

MDA is looking at introducing liquid propulsion into the kill vehicle design, partly because the plan to move the SM-3 to land for the Aegis Ashore European defense architecture would allow the use of hypergolic propellants, which are banned for ship-based usage.

"We know from past work on the EKV [Exoatmospheric Kill Vehicle] that liquid propulsion gives us all sorts of flexibility. We can turn it on when we need it and we can turn it off when we want to shut it off," says Rich Matlock, MDA director of advanced programs. The EKV is the kill vehicle built by Raytheon and used for the Ground-Based Midcourse Defense (GMD) interceptors at Ft. Greely, Alaska, and Vandenberg Air Force Base, Calif. EKV would be the kill vehicle today that would be used if an ICBM were launched at the United States. The SM-3 lacks the range and speed needed to kill a long-range missile.

A solid propellant such as that used in the SM-3 kill vehicle design burns steadily until it is expended, limiting its flexibility. With a liquid fuel "if we have got to put some thrust into the system right now, we can put it in and shut it off and save some thrust for later … We can wait for a long period of time between those pulses," Matlock says.

Matlock says MDA also is examining some of the design concepts used by Raytheon and Lockheed Martin in their competing designs for the defunct Multiple Kill Vehicle (MKV) program. Though terminated in the Fiscal 2010 budget request, MKV was seeking designs for many tiny kill vehicles that could be put atop a single interceptor, thus boosting the per-unit effectiveness of each missile in killing numbers of warheads. The companies each explored lightweight technologies and liquid propulsion for their MKV designs.

"Technology work that we are doing right now in lightweight liquid divert and attitude fuel system … as well as the possibility of applying liquid propellant technology in upper stages of a new IIB missile are things that we are exploring," Matlock says, adding that the objective is a blend of older technology lessons from the EKV design and more recent experiences with the MKV.

Raytheon is studying various concepts for improvements to the SM-3 and a next-generation kill vehicle. Architecture study work is under way, and it will be finished this fiscal year. Systems engineering work could start as soon as October 2011, Matlock says. MDA is in discussions with Aerojet and Pratt & Whitney, the two main liquid propellant contractors, as part of the review.

Most likely, resources would be allocated for this effort in the Fiscal 2012 budget.

Photo: DoD