Solar Sailing in Space

NASA prepares to test a satellite that can be propelled by light particles from the sun bouncing off its sails.

For the first time, NASA is preparing to send into orbit a small satellite that can be propelled by solar sails. When light particles from the sun strike the surface of the sail, the energy is transferred to it, providing a propulsive force that moves the satellite through space.

NASA's goal is to test the complex deployment mechanism of the 10-square-meter sails, says Dean Alhorn, an engineer at NASA's Marshall Space Flight Center, in Huntsville, AL, and the lead engineer on the project. "A successful flight will not only make for a unique historical event, but will show that we have a reliable mechanism to deploy a solar sail in space for future missions," says Alhorn.

The satellite, called NanoSail-D, is scheduled to launch from Omelek Island, in the Pacific Ocean, on July 29 onboard the Falcon 1 rocket developed by Space Exploration Technologies (SpaceX), of Hawthorn, CA. The NanoSail-D satellite's main frame is only 30 centimeters long and weighs nine pounds. Its solar sail is made of a custom polymer that is thinner than a piece of paper and coated with aluminum to reflect the photons. "It looks like Saran Wrap with a metalized surface but is stronger and suited for the space environment," says Alhorn.

In theory, a solar sail could be used as propulsion for round-trip missions in the solar system. In friction-free space, the tiny propulsive force of photons could conceivably get a craft up to about 100 miles per hour. Changing the sail's angle can change the craft's trajectory. "There is a lot of potential for solar-sail propulsion once we show that this can be deployed in space," says Alhorn. "Already we are working on ways to maneuver the sails, and we can theorize better designs that are based on proven technology."

The concept of solar sailing was invented in the 1920s by two Russian scientists, and it has been the subject of a few projects over the years, says Louis Friedman, the executive director of the Planetary Society, a public space organization based in Pasadena, CA. The Russians deployed a large reflective sheet of material outside their Mir space station in 1992, and the Japanese did something similar in 2004, but neither was used for solar-sail propulsion.

The most recent effort was led by Friedman, whose team from the Planetary Society and from Cosmos Studios, a media company based in Ithaca, NY, actually built a solar-sail-powered spacecraft in Russia called Cosmos 1. It did not launch because of rocket failures. Now, Friedman is working on a satellite called Cosmos 2 that is similar to NASA's design but uses inexpensive Mylar, a basic plastic material. "Mylar is easy to get, is manufactured in large quantities, and is adequate for short flights," says Friedman. "If you want to do an interplanetary mission, which is part of NASA's future plans, you would need something longer lasting and more ultraviolet resistant, so you would use a more exotic material."

But the most complex part may be deploying sails after a spacecraft has been launched out of the earth's atmosphere. Once the NASA satellite is aloft, a computer will command a heater to burn a high-strength fishing line to open four spring-hinged panels, exposing the solar sail. Fifteen seconds later, another so-called burn-wire system will cause four booms to unfold. The booms will pull the solar sail off a center spindle, unrolling it in four different quadrants, says Alhorn. The satellite will remain in low earth orbit for between five days and two weeks, during which researchers will track and analyze the satellite.

The deployment mechanism is the most interesting part of the spacecraft, says Friedman. His craft will use an inflatable deployment system to expand the sail to a diameter of 30 meters. Unlike with NanoSail-D, his plan is to control the satellite with the sail.

Read more from source

Read more...

Hanns.G HG281DJ 28in TFT

A super-sized, high-quality display at an affordable price

Written by Paul Monckton
personal computer world, 14 Jul 2008

The first thing you notice about this display is its 28in size.

Not simply the physical dimensions of the screen, but also the enlarged type and icons.

It has the same 1,920x1,200-pixel resolution as a 24in monitor, so the individual pixels are much bigger.

We were pleased to see that, unlike with some other large-screen displays, the grid lines between the pixels were almost invisible, keeping images smooth and text easy to read.

If your eyesight isn’t great, then this monitor could make things a whole lot easier for you.

Fitted with a pair of video inputs, the HG281DJ can accept analogue video via the standard VGA port and digital connections via HDMI.

It will also accept high-definition analogue component video via an adapter, which is good news if you want to use the display for gaming on an original model Xbox 360.

At 500cd/m2, this is a very bright screen, so you can make full use of its TV-like proportions for watching HD video in well-lit rooms without difficulty.

Contrast levels could be better – there’s some noticeable backlight bleeding in dark scenes – but overall the HD281DJ acquits itself rather well for a TN panel and is capable of delivering vivid, saturated colours beyond our expectations.

However, one major omission is the lack of flexible scaling options for 16:9 and 4:3 inputs, meaning you’ll have to rely on your PC graphics card for that.

Externally, the casing is robust and well made, if a little uninspiring, with a bezel that’s rather thick by today’s standards. The power switch and menu controls are mounted vertically down the right-hand edge of the case, making them rather frustrating to use as you can’t read the labels and look at the screen simultaneously.

If you’re in the market for a large screen, the HG281DJ is a decent quality display that won’t break the bank.

Read more from source

Read more...

Solio 1000 Hybrid Charger

Get your power from the sun

Written by Paul Lester

Computeract!ve 10 Jul 2008

Solio makes a range of solar-powered battery chargers, but the Hybrid 1000 improves upon the more basic models because it contains a rechargeable battery that holds power for up to a year.

The 'Hybrid' in the name indicates that the device can be charged either by plugging it into the USB port of a computer (notebook or desktop) or, of course, by leaving it in the sun.

Supplied in the box is a USB power cable and three adaptors so that the device can be connected to a portable music player, phone or other portable device. The adapters supplied in the box connect it to Nokia phones and devices that accept mini-USB power (which more and more phones and cameras do).

There's also a generic USB connector so that you can plug in any USB cable supplied with a product that offers power. There is a wide range of additional fittings for other devices, all of which can be bought from the Solio website, but that obviously adds to the cost.

Once you've got the necessary connections sorted the Hybrid 1000 is very easy to use, with a simple Start button to kick off the charging process and a series of lights that report on the current level of charge of the internal battery.

The device worked well during our tests but we did notice that it needs to be placed in quite direct sunlight in order for the solar panels to do their job. Solio reckons that a full battery will charge the average mobile phone fully or give around 10 hours of music playback on a music player. One hour of direct sunshine will give you around 15 minutes of talk time or 40 minutes of music, then.

In our tests we found these figures a little ambitious but they're not so far off that it became a major problem. We can see the charger coming in very handy during outdoor pursuits in favourable weather (it comes with a carabiner clip for attaching to a bag). It's a shame that the Hybrid isn't a bit more rugged, or waterproof for example, but overall it's an effective way to charging portable devices in an emergency or on the move.

Read more from source

Read more...

Acer Aspire One notebook computer

Written by Tom Royal

Computeract!ve, 10 Jul 2008

Miniature notebooks, which do all the jobs of full-sized ones but with slightly less power, seem to be the order of the day in 2008.

The trend was started by the Asus Eee, but since then there's been the Packard Bell Easynote XS, the HP Mininote, the MSI Wind and now the Acer Aspire One. The latter stands out in this crowded marketplace because it's one of the cheapest around, at £230.

The One looks smart, with a white case and shiny black bezel around the 9in 1,024x600 pixel screen. The screen isn’t particularly bright, but it is good enough for browsing online and for work. Acer has employed a lot of font smoothing, though, so text doesn’t appear as pin-sharp as it does on some others.

Along the two sides are sockets: three USB, network, monitor, headphone, microphone and memory card readers. The card reader on the right side works like a normal one, but the one on the left can be used to expand the computer's main storage: a memory card inserted there will add its capacity automatically to the main storage (instead of a hard disk it uses an 8GB memory chip).

The slim battery has a relatively low capacity, so despite some useful power-saving tricks, the One doesn't last long on a charge. Without wireless networking, it ran out after two and a quarter hours in our tests, which is far lower than the MSI Wind can do, for instance. Regular travellers will have to go for the larger £80 battery (which is not yet available).

The keyboard is much better – it's well-designed with larger keys that we quickly adjusted to. The trackpad has mouse buttons on either side, but a function key can disable the touch pad entirely if it gets in the way when typing.

Inside the One you’ll find a 1.6GHZ Intel Atom processor, 512MB of memory and the 8GB of storage. It's happy enough running a few browser windows and a word processor at the same time, and is capable of playing DivX video files. A small fan cools the system, but it’s quite quiet.

Windows XP Home will be available on more expensive Aspire One models, but this one uses the free Linux operating system with a selection of useful programs installed. We liked the ability to start both Firefox and Openoffice Writer from the front screen, and the email and instant messaging programs can cleverly connect to several services.

As yet, Acer has not confirmed when the Aspire One will be available, but it's expected to ship by August. When that happens, although the competition betters it in a few areas, at just £230 the One will be the best value mini notebook out there.

Vista compatible: No

Read more from source

Read more...