Let's Get 7 in IELTS

By Jonathan Amos
Science reporter, BBC News

plotting areas of ground that may or may not need fertiliser applications.

The Zephyr-6, as it is known, stayed aloft for more than three days, running through the night on batteries it had recharged in sunlight.

The flight was a demonstration for the US military, which is looking for new types of technology to support its troops on the ground.

Craft like Zephyr might make ideal platforms for reconnaissance.

They could also be used to relay battlefield communications.

Chris Kelleher, from UK defence and research firm QinetiQ, said Unmanned Aerial Vehicles (UAVs) offer advantages over traditional aircraft and even satellites.

"The principal advantage is persistence - that you would be there all the time," he told BBC News. "A satellite goes over the same part of the Earth twice a day - and one of those is at night - so it's only really getting a snapshot of activity. Zephyr would be watching all day."

Deployment close

The latest flight was conducted at the US Army's Yuma Proving Ground in Arizona.

The Zephyr flew non-stop for 82 hours, 37 minutes.

That time beats the current official world record for unmanned flight set by the US robot plane Global Hawk - of 30 hours, 24 minutes - and even Zephyr's own previous best of 54 hours achieved last year.

However, the Yuma mark remains "unofficial" because QinetiQ did not involve the FAI (Federation Aeronautique Internationale), the world air sports federation, which sanctions all record attempts.

The US Department of Defense funded the demonstration flight under its Joint Capability Technology Demonstration (JCTD) programme.

This programme is designed to advance the technologies American commanders 5would most like to see in the field. ++++5

"We think Zephyr is very close to an operational system - within the next two years is what we're aiming for," Mr Kelleher said. "We have one more step of improvements; we trying to design a robust and reliable system that will really sit up there for months; and we want to push the performance."

Energy density

The trial, which took place between 28 and 31 July, also included the participation of the UK Ministry of Defence.

The 30kg Zephyr was guided by remote control to an operating altitude in excess of 18km (60,000ft), and then flown on autopilot and via satellite communication.

It tested a communications payload weighing approximately 2kg.

At first sight, the propeller-driven Zephyr looks to be just another model aircraft, and it is even launched by hand. But this "pilotless" vehicle with its 18-metre wingspan incorporates world-leading technologies.

Its structure uses ultra-lightweight carbon-fibre material; and the plane flies on solar power generated by amorphous silicon solar arrays no thicker than sheets of paper. These are glued over the aircraft's wings.

To get through the night, the propellers are powered from lithium-sulphur batteries which are topped up during the day.

"A lot of effort has gone into power storage and light-weighting the systems," explained Mr Kelleher. "Lithium sulphur is more than double the energy density of the best alternative technology which is lithium polymer batteries.

"They are an exceptional performer. We've worked with the Sion Corporation. They've had them in development for years. We're actually the first application in the world for them."

Vulture venture

Zephyr has demonstrated that it can cope with extremes of temperature - from the blistering 45C heat found at ground level in Arizona's Sonoran Desert, to the minus 70C chill experienced at altitudes of more than 18km (60,000ft).

The engineers from the Farnborough-based company are now collaborating with the American aerospace giant Boeing on a defence project codenamed Vulture.

This would see the biggest plane in history take to the sky, powered by the sun and capable of carrying a 450-kilo (1,000lb) payload.

US commanders say the design must be able to maintain its position over a particular spot on the Earth's surface uninterrupted for five years.

QinetiQ is also developing UAV technology for civilian uses.

It has been working recently with Aberystwyth University on field monitoring trials, plotting areas of ground that may or may not need fertiliser applications.

Lightweight plane (30-34kg/70lb) is launched by hand

Coms or surveillance payload of about 2kg (4.5lb)

Flies autonomously and can climb to more than 18km (60,000ft)

By day, Zephyr flies on solar power and recharges its batteries

Advanced amorphous silicon solar arrays supplied by Unisolar

Rechargeable lithium-sulphur batteries supplied by Sion Corp

Jonathan.Amos-INTERNET@bbc.co.uk

Fertiliser 肥料,促進發展者(=fertilizer)

Lightweight 標準重量以下的人或物

Endurance 耐久力,忍耐力

Unmanned 無人的,無人駕駛的

Zephyr 微風

Aloft 在高空,在高處

Troop 軍隊,部隊; 一群,大量

Reconnaissance 偵查,勘查,事先考察

Aerial 航空的,飛機的

Persistence 持續,持久; 堅持,固執

go over 受歡迎,查看,重溫

snapshot 快照,急射,速射,簡要的印象,點滴的了解

Deployment 部署,調查

Arizona美國亞利桑那州

Sanction 認可,核准,贊成,支持

Commander 指揮官,司令官,(團體、組織)主管人,領導人

Robust 結實的,健全的,堅固耐用的

in excess of 超過

autopilot 自動駕駛儀(= automatic pilot)

payload火箭所載彈頭(或人造衛星等);彈頭內的炸藥; 收費載重量;商務載重量; 人事費

propeller-driven 螺旋槳駕駛

pilotless 無人飛機

wingspan (飛機或鳥的)翼展

amorphous silicon 非結晶矽

lithium-sulphur 硫磺鋰

polymer 聚合物

Vulture 禿鷹

Blistering (溫度,速度)極高的,極度的;極熱的,極快的; 憤怒的,猛烈的

Aerospace航空與航天空間(指地球大氣層及其外面的空間); 航空航天學

Boeing 波音客機

Civilian (與軍、警相對的)平民,百姓; 民法專家;羅馬法專家

Surveillance 看守,監視,監察,檢查

Autonomously自治地;獨立自主地

Rechargeable (蓄電池)可在充電的