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]

Sailing, sailing, over the bounding interplanetary main

Edward Willett @ 16-04-2008

solar sailI’ve always loved the idea of the solar sail, giant glistening sails that use solar radiation to propel a ship through the solar system (as in the image at left).

But the Finnish Meterological Institute has come up with a better way to utilize that radiation for spacecraft propulsion, “by using long metallic tethers and a solar-powered electron gun to create an ‘electric sail.'” (Via Gizmag.)

Invented in 2006 at the Kumpula Space Centre, the electric solar wind sail, alas, loses some of the romance of the traditional solar sail: it looks more like an antenna (view an animation here):

A full-scale version would consist of up to 100 thin conducting wires as long as 20 km that are kept in a high positive potential by the spacecraft’s on-board solar-powered electron gun. This electric field effectively turns the wires into 50 meter wide sails that can then make use of solar wind. It’s estimated that a 20km long electric sail wire (which weighs only a few hundred grams and fits in a small reel) is equivalent to a one square kilometer solar wind sail when deployed in this way.

Planning for a test mission has begun, and the researchers note that the same technology could also assist in the development of solar power satellites.

In 2004 NASA’s Solar Sail Propulsion Team successfully deployed two 10-meter solar sails made of reflective material 40 to 100 times thinner than a piece of writing paper in a laboratory vacuum environment. But the first solar sail spacecraft, Cosmos 1, failed to enter orbit after its 2005 launch.  (UPDATE: Not, as commentator Anthony points out, due to any fault of the solar sails, but due to a rocket booster failure.)

(Image: John Ballentine.)

[tags]space exploration, solar sails, space travel, solar power[/tags]