The Beyond Visual Range Air to Air missile is a critical munition in any air force arsenal. At first it might seem easy for a western air force. Call Raytheon, order up the latest version of the AIM-120 AMRAAM, and then call it a day and have a beer. Is it really that easy? Let’s take a look.
The AIM-120 AMRAAM was the world’s first missile with an active radar seeker, and it has become the world standard. It was designed to replace the AIM-7 Sparrow semi-active radar homing missile. It features improved range, and a way-cool seeker. The Sparrow’s semi-active radar seeker requires an external source of radar to illuminate the target, usually the firing aircraft. So the aircraft has to keep flying more-or-less towards the target while the Sparrow is in flight. This strongly limits the evasive maneuvering possibilities of the launch aircraft. If the radar lock is broken, the missile becomes a useless ballistic projectile.
The AMRAAM is different. It has an inertial guidance component for the initial run towards the target. It can be updated by radar from the launch aircraft. Then, when it gets close enough to the target, it turns on the active radar seeker. This has it’s own radar, so the launch aircraft is free to turn away from the target aircraft. It’s a big improvement. The seeker can also home on jamming if the target aircraft tries to jam it.
Okay, so that’s cool. The rest of the AMRAAM is pretty typical: it’s a single-pulse solid fuel rocket. So once you light it, it burns until the fuel is gone, and only burns once. This means that during most of the intercept it’s coasting. There are also dual-pulse rockets which relight later, which helps chase down a maneuvering target. But those are more expensive, and while there’s been a lot of discussion about putting one on the AMRAAM, that still hasn’t happened yet. The AIM-120D gets its improved range from improved guidance algorithms and GPS-aided navigation. Cool. The question becomes: can we do better.
We’ll need to take a brief interlude here to define a term: the no-escape zone. This is the range in which a target can’t escape a missile by outrunning it. Outside of the no-escape zone, a fighter can turn away and light afterburners and the missile will be unable to catch it. Within the no-escape zone is not a guaranteed kill, it merely forces the fighter to maneuver aggressively to force the missile to miss.
Anyway, the Europeans have designed something nice for once in an effort to do better, and are actually getting it to market in a sort of timely fashion. This is the MBDA Meteor AAM. It’s noteworthy for two reasons. First, it has a datalink for midcourse guidance updates from the launch aircraft, which improves the accuracy of the midcourse phase of the flight at longer ranges. More importantly, it has a snazzy new engine. This is a “throttleable ducted rocket” also known as an “air-augmented rocket,” but it’s easiest to think of it as a hybrid solid-fuel rocket/ramjet motor. Like a rocket, it can give useful thrust from zero speed. Like a ramjet, it can also pull in outside air, and has no moving parts. This means it gets way more burn time from its motor, which means that it has a much bigger no-escape zone. Even the way-cool guidance algorithms in the -120D can’t get around the fact that the Meteor has a more advanced engine that provides more oomph. The Meteor isn’t that much bigger than the AMRAAM either, at least as far as length and weight. It might take some doing to get it certified for internal carriage on the F-35 though.
So where does that leave us? The Meteor is the better missile, with the bigger price tag. We’d say it’s worth it though, especially to get those early shots in on Flankers. We’ll have to spend some money to get it qualified on legacy platforms, but that’s totally worth it for the leg up on potential enemies. It’ll be interesting to see if the AMRAAM ever gets that improved motor.