Now a strength, aerospace's reliance on GPS for guidance and navigation could become a vulnerability with the growing threat of jamming and spoofing of the satellite signals. One answer is the development of chip-scale inertial measurement units (IMU) to give every device a self-contained ability to navigate precisely when GPS is denied. These require microscale clocks—Symmetricom's chip-scale atomic clock weighs just 35 grams—micromachined 3-D gyroscopes and new types of sensors. The U.S. Defense Advanced Research Project Agency's (Darpa) goal is to develop a 10-cu.-mm single-chip IMU with the performance of a 1,000-cu.-cm tactical inertial navigation system.
The ability to display unmanned-aircraft sensor video in helicopter cockpits has proved pivotal in two wars, and takes another step in 2014 when the U.S. Army deploys to Afghanistan new Boeing AH-64E Apaches with the ability to control its General Atomics MQ-1C Gray Eagle UAVs. Where the AH-64D has “Level 2” control of the UAV payload, the AH-64E is the first aircraft fielded with Lockheed Martin-developed avionics allowing Level 4 control of the air vehicle itself via the Ku-band tactical common data link. Future upgrades will provide multi-band and multi-UAV control from the Apache.
Burning less fuel and keeping things cool are the drivers behind development of a new type of combat-aircraft engine that can vary its bypass-ratio between fuel-efficient subsonic loiter and high-thrust supersonic dash. Under the U.S. Air Force Research Laboratory's Advanced Engine Technology Development program, General Electric and Pratt & Whitney will ground-test variable-cycle engines in 2016 that use adaptive fans and a third airflow stream—outside the core and bypass duct—to vary bypass ratio and generate additional cooling air for aircraft systems. Reengining the Lockheed Martin F-35 post-2020 and powering 2030-timeframe “sixth-generation” fighters are the program's targets.
Geese do it, so why not aircraft? The U.S. Air Force is looking at formation flying to reduce the fuel burned by its airlifter fleet. Flight tests in 2013 showed a Boeing C-17 can reduce fuel burn up to 10% by flying in the wingtip vortex of another C-17. Flying in the upward side of the rotating flow shed by the lead aircraft increases lift on the trailing aircraft's wing, reducing thrust required. Trials showed software changes enabled the autopilot and autothrottle to maintain position 3,000-6,000 ft. behind the lead C-17 without increasing crew workload. The Air Force plans an operational demonstration over the next few years.
The military is wedded to large, expensive satellites but talks about “disaggregating” their capabilities to smaller, more numerous spacecraft to reduce costs. Getting small milsats off the ground is hard, however. Darpa canceled a demo of dispersing the functions of a single satellite across networked formation-flying smallsats, and has shelved plans to fly a constellation of 30 imaging cubesats. But, for now, the agency continues development of the Alasa air-launch system to orbit 45-kg (100-lb.) payloads for $1 million a time, and plans to demo the S-1 reusable spaceplane to loft 1,800-kg payloads for $5 million a launch.