Archive for the ‘aerospace’ Category

Jet-engine silencer

Friday, July 4th, 2008

Aircraft noise is serious problem for the aviation industry, particularly during take off and landing near urban areas. Jet engines are a major source of that noise.

Now, though, Dimitri Papamoschou at the University of California, Irvine, US, says it is possible to quieten a jet engine by separating its exhaust into high and low speed flows.

He says that most of an engine’s noise comes from turbulence in the fastest-flowing air. By separating the air into two channels of different speeds, he says the noise can be directed upwards, away from the ground and its inhabitants.

In simulations, funded by NASA, Papamoschou found that this technique can reduce the amount of noise heading towards the ground by more than 6 decibels.

This is a significant amount given that decibels are a logarithmic scale, so that every drop of 3 decibels is equivalent to a halving of power. A “silenced” engine would produce about a quarter of the acoustic energy of a conventional one and be significantly quieter.

Read the jet-engine silencer patent application.

Justin Mullins, New Scientist consultant

Posted in NASA, aerospace, sound, vehicles | Comments Off

Plasma-powered flying saucer

Friday, May 9th, 2008

Pass a current or magnetic field through a conducting fluid and it will generate a force.

Numerous aerospace engineers have tried and failed to exploit this phenomenon, known as magnetohydrodynamics, as an exotic form of propulsion for aircraft. But perhaps attempts so far have all been too big.

A very small design could have a better chance of taking off, says Subrata Roy, an aerospace engineer at the University of Florida, Gainesville, US.

With a span of less than 15 centimetres, his aircraft qualifies as a micro air vehicle (MAV), but it has an unconventional design to say the least. It is a saucer shape covered with electrodes that ionise air to create a plasma. This plasma is then accelerated by an electric field to push air around and generate lift.

Roy says the machine can be filled with helium to reduce its weight, and is efficient enough to be powered by onboard batteries. Its ability to hover and generate lift electronically means that it is particularly robust against gusts of wind that send other MAVs off course, says Roy.
All he needs to do now is build one and get it flying. Like other MAVs, the primary application would probably be surveillance, but a plasma flying saucer would make a great toy too.

Read the full wingless hovering micro-flyer patent application.

Justin Mullins, New Scientist consultant

Posted in aerospace, robots, vehicles | Comments Off

Flapping spy vehicle

Friday, March 28th, 2008

If you want a bird’s eye view of what is over the next hill, your best bet is a micro air vehicle – an autonomous aircraft with a wing span of less than 15 centimetres. Making a fixed wing aircraft of this size is straightforward enough but there are a number of drawbacks, such as being easily buffeted in by light gusts of wind.

Nature’s answer to this problem is to give small birds wings that can be flapped in bursts to avoid sudden gusts. But human engineers have found it hard to build a flapping mechanism that is both light and efficient enough to get a small vehicle off the ground while also carrying a suite of useful instruments, such as a camera and a radio transmitter.

That has not stopped Sunil Agrawal, director of the Mechanical Systems Laboratory at the University of Delaware, and colleagues from trying.

One problem is that flapping is not a simple up and down movement, but a complex series of motions that include rotating the wing to “feather” it in the upward part of a stroke.

With funding from the US Army Research Office, Agrawal, says he has solved this problem using a novel mechanism powered by a single actuator. As well as powering an ornithopter, the group says the mechanism could be used to create a flapping air current, or to propel an underwater vehicle.

Read the full ornithopter UAV patent application.

Justin Mullins, New Scientist consultant

Posted in aerospace, vehicles | Comments Off