Propellantless propulsion

Tom James @ 25-08-2009

Tether-satellite-NASAFollowing on from solar sails we have a discussion of that other science fictional bastion of propellantless propulsion – the space elevator – it turns out that space elevators and space tethers can be used for more than just getting into orbit:

A series of bolo tethers, each tether passing a spacecraft onto the next, could be used to achieve even larger orbit changes than a single system. For example, one tether system could catch a spacecraft from a very low orbit and swing it into a somewhat higher orbit. Another bolo picks it up from there and puts the satellite into a geosynchronous transfer orbit (GTO). A third tether catches the load again and imparts sufficient velocity to it so that it reaches escape velocity. A satellite initially orbiting just above the atmosphere could thus be slung all the way into an interplanetary orbit around the Sun, and all this without using any rocket propulsion and propellant

This is in the context of a review by Centauri Dreams of Space Tethers and Space Elevators by Michel van Pelt, which explores tethers and space elevator concepts in some detail.

[from Centauri Dreams][image from Wikimedia and NASA]


Scaled-elextric: slot cars for transport

Tom James @ 11-08-2009

slot-carToday’s dose of technocratic mass-transport conceptual design is brought to you by German designer Christian Förg. His Speedway Transport System is inspired by slot cars of his youth:

Förg’s Speedway Transport System concept uses a network of linear electric motors to propel cars along the highway.

He sees us driving around in futuristic dual-mode electric cars with small motors for city driving. When we’re ready to leave town, a contact-free linear motor would propel the car over long distances with a drifting magnetic field. Förg says linear motors would work under our existing roadways, complementing – not replacing – existing automotive technology.

“This means that you can use the roads with normal cars and also at the same time for the Speedway system,”

If this ever gets taken up it’ll be interesting to see what alternative uses the street finds for this technology.

A slight non-sequitur: Will Hutton writes in the Guardian on the dire state of the UK rail network, and how in order to remain economically competitive, Britain must invest in the kind of high-speed rail they have in Europe.

[via Wired][image from Wired]


eROCKIT – 50mph electro-assist bicycle

Paul Raven @ 16-07-2009

File under “wow, gimme one of those!” – the eROCKIT bike is described by its creators as “a new vehicle category, the human-machine-hybrid”. A trifle hyperbolic, perhaps, but it’s still pretty awesome. Watch:

The eROCKIT bridges the gap between the regular two wheeler categories. On one side the muscle-powered two wheelers, on the other side, the motorcycles. The eROCKIT concept requires a continuous muscle deployment from the rider. The vehicle’s electronic system multiplies this muscle power and deploys it as vehicle propulsion.

For the first time in the history of vehicle construction, the driver’s physical power becomes just as relevant for driving dynamics and speed as technical vehicle properties and engine power.

Send me one for review, please! Because I sure as hell can’t afford the €33,000 price tag… [via NextBigFuture]


Smartdust on the roads, in the cars

Tom James @ 01-07-2009

highway_insomniaThe old chestnut of fully automatic cars trundled a little bit closer with the development of EM2P by the European research group EMMA:

“We sought to hide the underlying complexity of in-car embedded sensors so that developers could quickly design new applications with existing electronics,” explains Antonio Marqués Moreno, coordinator of the EMMA project. “EMMA will foster cost-efficient ambient intelligence systems with optimal performance, high reliability, reduced time-to-market and faster deployment.”

The project hopes that, by hiding the complexity of the underlying infrastructure, its work will open up new prospects in the field of embedded, cooperating wireless objects.

The key of the idea is to make a middleware application between the embedded sensors in cars and designers who want to develop interesting and useful applications.

it could also work between cars – opening the prospect of cooperating cars – and, of course, it can work with traffic infrastructure like lights, warning signs, and other signalling information. All of this via the same middleware platform.

Also a possible route of entry for a hypothetical Internet of Things.

[from ICT results, via Physorg][image from Nrbelex on flickr]


Jamitons – the math of phantom traffic jams

Paul Raven @ 23-06-2009

traffic jamHave you ever wondered what causes those seemingly cause-less traffic jams the occur pretty much anywhere with a reasonable density of motor vehicles? Sure you have – but you probably didn’t have the mathematical chops to investigate further, unlike the geeks at MIT:

The mathematics of such traffic jams are strikingly similar to the equations that describe detonation waves produced by explosions, said Aslan Kasimov, a lecturer in MIT’s Department of Mathematics. Realizing this allowed the reseachers to solve traffic jam equations that were first theorized in the 1950s. The MIT researchers even came up with a name for this kind of gridlock – “jamiton.” It’s a riff on “soliton,” a term used in math and physics to desribe a self-sustaining wave that maintains its shape while moving.

The equations MIT came up with are similar to those used to describe fluid mechanics, and they model traffic jams as a self-sustaining wave.

“We wanted to describe this using a mathematical model similar to that of fluid flow,” Kasimov said.

The researchers hit upon the equation after an experiment by Japanese researchers demonstrated the formation of jamitrons on a circular road. In that experiment, drivers were instructed to travel 30 kilometers an hour (18.6 mph) while maintaining a constant distance between cars. It didn’t take long before disruptions occurred and phantom jams formed. Denser traffic brought quicker jams.

The MIT team found speed, traffic density and other factors can determine conditions that will lead to a jamiton and how quickly it will spread. Once the jam forms, the researchers say, drivers have no choice but to wait for it to clear. The new model could lead to roads designed with sufficient capacity to keep traffic density below the point at which a jamiton can form.

Now, after reading that article I found myself thinking “wouldn’t some sort of peer-to-peer traffic management system be better than building bigger roads?” So imagine how smug I felt when this article turned up a few days later:

The hope, of course, is that by understanding traffic jams we can learn to prevent them. Tom Vanderbilt, in his authoritative book Traffic, describes a simple experiment performed by the Washington Department of Transportation that involved a liter of rice, a plastic funnel, and a glass beaker. When the rice was poured into the beaker all at once, it took 40 seconds for the funnel to empty; the density of jostling grains impeded the flow. However, when the grains were poured in a gradual stream, it took only 27 seconds for the rice to pass through. What seemed slower actually turned out to be 30 percent faster. This helps explain why traffic engineers are so eager to install red lights on highway onramps: By slowing traffic before it enters the concrete funnel, they hope to prevent the road from exceeding its critical density.

I’d be willing to go out on a limb here and suggest that while vehicles are still driven manually by fallible and inherently selfish human beings, traffic jams are inevitable. The only way to truly control the side-effects of human behaviour are to take them out of the picture entirely – and while there are very few situations where I’d advocate such a thing, road traffic is one of them. [image by timsnell]


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