Thrown off course by relativity

Tom James @ 24-08-2009

Cosmos1-2006-2A preview of space-flight issues of the future: how do you account for the effects of relativity when travelling long distances? A solar sail launched from close to the Sun would have to account for relativistic effects when navigating to the edges of the solar system:

And even though those effects are relatively minor to start with, they have a significant effect over long distances.

The calculations carried out by Kezerashvili and Vazquez-Poritz show that the effects of general relativity could push a solar sail off course by as much as a million kilometers by the time it reaches the Oort Cloud

The promise of solar sails as a propulsion mechanism is impressive:

By one calculation, a solar sail with a radius of about a kilometer and a mass of 300 kg (including 150 kg of payload) would have a peak acceleration of about 0.6 g if released on a parabolic trajectory about 0.1 astronomical unit (AU) from the sun (where the radiation pressure is higher).

That kind of acceleration would take it beyond the Kuiper belt to the heliopause, the boundary between the solar system and interstellar space (and a distance of 200 AU), in only 2.5 years.

In 30 years, a solar sail could travel 2,500 AU, far enough to explore the Oort Cloud.

Of course we need to actually build one of these things first.

[from Technology Review, via Technovelgy][image from Wikimedia]


Astrophysicist replaces supercomputer with eight PlayStation 3s

Stephen Years @ 17-10-2007

ps3.jpgDr. Gaurav Khanna is trying to measure gravity waves – ripples in space-time that travel at the speed of light – that Einstein’s Theory of Relativity predicted would emerge when such an event takes place. To do this he used to use grants from the National Science Foundation to rent time on various supercomputing sites spread across the United States – usually employing two-to-five hundred nodes at a time. But each time he did this is cost about $5,000. Dr. Khanna figured out that for less than the price of one session on a Super Computer, he could build his own massively parallel computer that he could run indefinitley using Sony PlayStation 3 game consoles. Dr. Khanna wrote some custom Linux code to optimize the Cell processor found inside the PlayStation. He then approached Sony, which donated eight of the machines.

Khanna says that his gravity grid has been up and running for a little over a month now and that, crudely speaking, his eight consoles are equal to about 200 of the supercomputing nodes he used to rely on.

“Basically, it’s almost like a replacement,” he says. “I don’t have to use that supercomputer anymore, which is a good thing.”


Speed of light exceeded? Er, probably not.

Paul Raven @ 17-08-2007

You may have noticed the widely reported story that a team of German scientists have managed to make photons exceed the speed of light in the course of an experiment. Well, let’s just say that’s probably not exactly what happened. [Engadget]