‘A low-pollution solution for long-distance flight’: your letters to Professional Engineering

Article Source: IMechE

Driverless trains

“As a simple soul, I am puzzled by the vast amount of effort being put into developing driverless cars. The problem is immensely complex, involving many different and uncontrolled variables, and success is by no means certain. 

“Surely it would make sense to concentrate at first on the much simpler problem of driverless trains. After all, the Post Office railway ran successfully in London for 75 years from 1928 – admittedly there were no passengers to worry about!

“Several of our train operators have suggested saving costs by eliminating guards – but guards do something that machines cannot, they talk to passengers and help with their problems. To eliminate the drivers would seem much more sensible.

“Of course, the weight of tradition, the romance of rail and (not least) union opposition would make driverless trains difficult to achieve, but in the cold light of logic isn’t it the way to go?”

C A Hely-Hutchinson, Ludlow, Shropshire

Putting the brakes on

“Dr Jody Muelaner writes that changing from internal combustion engines to electric motors will not reduce the amounts of particulate matter from the erosion of tyres and brake pads (‘Why electric cars won’t stop air pollution,’ Professional Engineering No 7, 2019). This is not correct. 

“If the motors are used to their full capability, including regenerative braking, the wear and tear on brake components are reduced, hence fewer particulates from that source. This secondary benefit has already been demonstrated by Professor Hua Zhao and the Vulcanaer team at Brunel University London by harnessing the diesel engine as an air hybrid during overrun, thus contributing to vehicle braking that reduces dependence on the friction brakes. 

“This is in addition to the primary benefit of the technology to capture and store compressed air without use of a parasitic pump, saving fuel and, when combined with an air starter, providing energy-free stop-start operation that saves fuel, tailpipe emissions and particulate matter.”

Dr Chris Bale, Harrogate, North Yorkshire

Up, up and away… above the clouds

“Electric flight has so far been proposed for battery-powered short-range, but a solar-electric plane has flown from France to England using panels on the rear slope of the wings. It could not fly back as the panels then faced too far north to collect enough solar energy! 

A solar-powered aircraft (Credit: Shutterstock)

“An aeroplane somehow getting above the clouds could fly west to east all day. 

“With little fuel to buy or carry this could be a low-pollution and economic solution for long-distance flights.”

Geoffrey Leet, Thurso, Caithness  

Design-out defects

“In recent years I have followed NASA’s Commercial Crew Program, where Boeing’s Starliner and SpaceX’s Crew Dragon will restore US capability to launch astronauts to low Earth orbit.

“Both have inaugural manned flights slated for 2020, so now is an interesting time to follow developments including the setbacks with lessons to learn. On 4 November 2019, Boeing tested Starliner’s Launch Escape System. The test proceeded nominally until main parachute deployment, where one was pulled away from its anchor, undesirably leaving the capsule with just two.

“Space is hard. This is why we test and why we have redundancy, but what captured my attention was the reason that the parachute detached. On 7 November, Boeing revealed that it had been identified as a pin incorrectly engaged, with its correct assembly difficult to confirm because of a protective sheath. ‘Fairly easy steps’ have now been taken to verify correct assembly, including pull-tests.

“A few years ago, a friend of mine was killed when the glider she was flying suffered a structural failure. The Air Accidents Investigation Branch report subsequently identified the same issue as a primary cause – a pin not correctly engaged, because its insertion was difficult to verify. That glider was designed in 1960.

“It seems that over five decades later we still design safety-critical systems where correct assembly is difficult or impossible to confirm. As engineers we must strive to design out such deficiencies wherever possible, or, failing that, ensure that assembly procedures include suitable tests to verify correct assembly. 

“We stand on the shoulders of giants, but those giants have made mistakes that we should take care not to repeat.”

Matthew Reynolds, York

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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers. 

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