To begin with, it required packaging the laser guidance electronics into a much smaller volume. Given that the operating environmental conditions for rockets are harsh – with extremes of temperatures from ice cold to 2,000°F, rain, and supersonic particulate airflow, there were tough engineering challenges.
In particular, development of the wing slot seals [which are perforated] took some time and effort, as they needed to be strong enough to withstand harsh environmental conditions yet be weak enough to be broken by the wings after the rocket was fired.
APKWS II System Description
The APKWS II program is really for the WGU-59/B mid-body guidance unit, although there were other items.
NAVAIR image of the various component parts of the APKWS II system. Image courtesy of NAVAIR
The rocket assembly itself is composed of a MK 66 Mod 4 rocket motor, a choice of two 10-pound high explosive (HE) warheads and fuzes – the MK 151 with the M 423 fuze and the new, safer MK 152 with MK 435 Mod 0 fuze – and the WGU-59/B guidance unit with four wings with an integrated optical sensor. Besides the HE warheads, BAE also announced it had successfully tested M282 Multipurpose Penetrator (MPP) warheads at close ranges in May 2012 against a triple brick wall as well as an armored personnel carrier, thus demonstrating its ability to hit targets at close range and penetrate “complex targets” in urban terrain.
However, the entire APKWS II system comprises a launching platform; the lengthened 7-tube LAU-68 F/A rocket launcher; the SCS 7 aiming cue for the UH-1Y (the AH-1W does not need it); the AUR (all up rounds) as well as two types of storage containers – the Fastpack PA-140 for four AUR and CNU-711/E for four guidance kits.
Corey says that containers are critical and are vital for ensuring the components are safe in the field. The packaging containers have been drop tested from 40 feet – simulating a fall from a helicopter onto the flight deck of a ship.
As expected, adding the guidance unit means that there was a length and weight increase of 18.5 inches and 9 pounds, respectively, over the legacy 55-inch long, 23-pound unguided rocket.
A key program tenet was simplicity for platform integration. If a platform can fire an unguided weapon, it can fire the APKWS using the same launch sequence. “It allows us to add platforms relatively cheaply,” says Corey.
APKWS can also be fired from any platform that fires Hellfire missiles, according to BAE Systems.
How the System Works
The key is in the placement of BAE DASALS (distributed aperture semi-active laser seeker) seeker optics (aperture domes) on each of the guidance section wings, says BAE. In essence, these are four eyeball-like optical sensor elements, with a 40 degree instantaneous field of regard and a 28 degree field of view for a broader capture area, that are integrated into the leading edge of each of the four wings, which also have a flaperon at their trailing edges. These seekers are connected by fiber optic cables to the electronics in the guidance unit.
In the retracted position, they are stored inside the guidance unit. Special seals protect them from environmental effects and adjacent rocket firings. The wings deploy within 0.5 seconds after the missile is fired. The optical sensors receive coded laser energy from the target. In tests, they have picked up laser energy as far way as 14 kilometers, far in excess of the 8-kilometer maximum range requirements.