Vid The US Missile Defence Agency and American aerospace behemoth Lockheed is chuffed to announce that they have carried out successful hover tests of a Multiple Kill Vehicle space interceptor system this week.

Here's a vid of the test, courtesy of the missile-defence people and YouTube (remember you need Flash and a multimedia-friendly sysadmin to view these):

The test took place at the National Hover Test Facility at Edwards Air Force Base in California. To give an idea of scale, the module is rising to approximately 7 metres (23 feet) in the video, according to Lockheed.

The idea of the multiple kill vehicle is to allow a single missile-defence interceptor rocket to take out several objects in space, rather than just one. An enemy ballistic missile can easily throw a whole volley of stuff at the USA - such a "threat cluster" might easily include multiple nuclear warheads as well as decoys designed to frustrate the defences.

Not even America can afford to fire an interceptor rocket at every single object deploying from an enemy missile. This is a major criticism levelled at the entire missile defence programme: that it can never realistically defend against missiles equipped with decoys and/or multiple warheads.

Hence the multiple kill vehicle concept, which would let one interceptor hit more than one target. The MKV tested this week is the "L" version from Lockheed (there is also a parallel "R" job being built at Raytheon, on the theory that if one design doesn't work the other might*).

The MKV-L uses a central command vehicle equipped with a telescope for scanning the threat cluster, which carries its swarm of smaller kill vehicles into action. Like the existing one-shot kill modules it works essentially by holding itself exactly in the path of the oncoming warheads and decoys, destroying them using their own kinetic energy.

Any machine which is going to be able to get in the way of a nuclear warhead barrelling around the planet at thousands of miles per hour should be more than capable of hovering with some precision under its own power inside the atmosphere, and as the vid makes clear the MKV-L carrier can do this at least. According to the MDA it also "recognised and tracked a surrogate target" and transmitted video and flight telemetry during the test.

Both the MKV-L and the parallel MKV-R will need to jump over plenty more hurdles before becoming operational, however. The obstacles will probably be political and financial as much as technical. There is a strong body of scepticism in America regarding the desirability and feasibility of the entire Missile Defence effort, and the agency's friends fear that the new president may severely cut its funds - or perhaps even shut it down altogether.

Even if the MDA survives, the big ground-based midcourse interceptor rockets which are to be first to carry the MKV smartswarms may not - the GBIs are one of the agency's lamer ducks, along with the jumbo-jet laser cannon.

However, both Raytheon and Lockheed envisage putting their MKVs into the more popular Standard SM-3 naval space interceptor at some stage, so the kit might survive even in the event of a missile-defence cuts bloodbath.

For now, though, only Barack Obama could really tell you more. ®

*And also the theory that everyone deserves some of the pork.