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Air Platforms

USN seeks multi-day flight with Hybrid Tiger

14 August 2017

US Navy (USN) researchers are set to begin testing a prototype Group 2 unmanned aerial vehicle (UAV) that could attain upwards of three days endurance.

Hybrid Tiger is the follow on to the US Naval Research Laboratory’s (NRL's) Ion Tiger, which flew for 48 hours using proton exchange membrane fuel cells and gaseous hydrogen stored at 5,000 psi in a cryogenic liquid hydrogen fuel tank.

Hybrid Tiger’s first flight is expected to occur by May 2018.

NRL's Hybrid Tiger effort integrates a hydrogen fuel cell, solar photovoltaics, and energy-aware guidance algorithms into a single UAV to achieve multi-day endurance. (IHS Markit/Geoff Fein)NRL's Hybrid Tiger effort integrates a hydrogen fuel cell, solar photovoltaics, and energy-aware guidance algorithms into a single UAV to achieve multi-day endurance. (IHS Markit/Geoff Fein)

“[With] the Ion Tiger programme concluded, now NRL has a follow on programme we are calling Hybrid Tiger where we are putting solar panels on the wings and we are doing autonomous soaring,” Dr Richard Stroman, senior mechanical engineer, alternative energy section, chemistry division of NRL, told Jane’s .

“The idea is that the vehicle can identify a region of rising air and exploit it to gain altitude,” he said.

Hybrid Tiger is sponsored by the US Deputy Assistant Secretary of Defense for Operational Energy and the US Marine Corps Expeditionary Energy Office, and is focused on multi-day endurance in the Pacific Area of Responsibility, according to NRL.

The UAV will use a hydrogen fuel cell, solar panels on the wings, and energy-aware guidance algorithms to achieve an endurance of more than 3.5 days, even in December and up to 50° latitude, while carrying a small intelligence, surveillance, and reconnaissance payload.

A high-pressure hydrogen tank and fuel cell system will deliver night-time power, while the solar panels provide power during the day, according to NRL.

Using autonomous soaring and energy-aware guidance algorithms, Hybrid Tiger could gain altitude from thermal updrafts.

Stroman noted there are several ways Hybrid Tiger can ‘sense’ the environment to gain altitude. One way is to watch for one wingtip to rise, which would indicate there is a temperature gradient and thus rising air in that direction, he said.

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