Following the US Air Force's approval of a preliminary design review in early June, Northrop has been cleared to finalise the design by October and to deliver the computer upgrade for flight tests in the fourth quarter of 2009, says Ron Naylor, its B-2 programme manager. The company is upgrading the B-2's 256Kb-class processor chip with a Pentium-class Lockheed Martin integrated processing unit, with the improved FMS to feature 1Gb/s computational speed.
Once installed, the replacement processor and a new disc drive with fibre channel interfaces will enable a series of future and ongoing upgrades for the bomber's weapon and sensor systems. Northrop is upgrading its radar antenna, for example, to an active electronically scanned array. The radar processor, however, is being left alone until the FMS can handle the data throughput required to process synthetic aperture radar maps.
The USAF is also adding the Boeing GBU-39 small diameter bomb on the B-2. Without the processor upgrade, making any targeting changes for the full load-out of 80 small diameter bombs would take much longer.
The most direct upgrade supported by the new processor will be an improved communications suite. Addition of the integrated processing unit is the first increment of a larger modernisation effort called the B-2 extremely high frequency and computer upgrades programme. A second increment will replace the aircraft's Milstar ultra-high-frequency system to the EHF standard provided by the future satellite constellation of the Boeing family of advanced beyond line-of-sight terminals, making the B-2 a new "node" in the global information grid.
The upgrade requires changing the shape of the B-2's outer-mould line on the top of the aft fuselage. In a review of the programme released in March, the US Government Accountability Office reported concerns that the design changes could inadvertently alter the stealth bomber's radar cross section.
"We've had experts from across the company and the air force look at that and they say there aren't impacts to the low observability specifications from the antenna," counters Naylor. While the GAO is also concerned over the "high-risk" nature of the new disk drive, he says the design has faced problems normally associated with any computer development programme, but remains on track.
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