Penetrating High Altitude Endurance - PHAE

J-UCAS badge

When it was decided to terminate the J-UCAS programme various theories were aired about the real reasons behind this decision. The most obvious reason for the cancellation was that the differing requirements of the USAF and USN were never likely to be achieved in a single airframe, a lesson the US Defence Department should have learnt when the naval version of the F-111 had to be cancelled for exactly the same reasons. However, Nick Cook of Janes was quick to spot another reason for this cancellation when he saw in a Navy Fiscal Year 2007 budget document that the old J-UCAS programme was to be split into two separate programmes – a classified USAF programme and a Navy UCAV programme, with over $1.7 billion earmarked for these two separate programmes.

It is believed that the new USAF programme draws on much of the research and development undertaken during the J-UCAS programme, but is a completely new UAV known as the Penetrating High Altitude Endurance (PHAE). The PHAE is understood to be a highly stealthy design capable of cruising at 70,000 - 80,000 ft, with a very long endurance and is designed to be able to penetrate the most densely guarded airspace whilst remaining undetected and provide a persistent reconnaissance capability over the target.

J97-GE-3 engine

One report has suggested that the PHAE is a twin-engined design and the extra redundancy this would provide, enabling this highly classified vehicle to recover safely if one engine failed rather than crashing over enemy territory, would have considerable appeal. Power is believed to be provided by two General Electric J97-GE-3 engines that were originally built to power the single-engined AMQ-91 Compass Arrow, a stealthy UAV designed to cruise over China at 80,000 ft gathering intelligence on China’s nuclear programme that was cancelled in 1971. In 1988 a NASA paper reported that 24 of the J97-GE-3 engines were in storage at their AMES research center. The fact that NASA thought or was directed to store these highly specialised engines at their AMES research center, as opposed to them ending up on the scrap heap somewhere is significant. Perhaps even back in 1971 someone realised that at some stage in the future a requirement would re-emerge for a high-altitude UAV and that these engines would once again be capable of proving the necessary power.

With their Polecat Lockheed demonstrated their ability to design, build and fly a stealthy UAV in a short timescale using many off-the-shelf components, but I suspect the release of this information was designed to distract attention from another activity, possibly involving PHAE. Consequently, I would imagine that some development version of the PHAE is already flying but, to ensure the actual design remains a mystery for as long as possible, I imagine it will be a considerable time before any detailed photos are released to the Press.