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08 February 2021


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when science fiction becomes fact.
I read about this in a magazine called "Omni" which was science based, published by the same bunch who published "Penthouse" the interior decoration magazine.

Barbara Ann

Sailing the solar winds is an evocative idea, as Arthur C. Clarke to his credit, knew way back in the early 60's. I assume that presently these craft are only able to accelerate downwind (away from the Sun). If there were a way to give them a keel of some kind that would open endless possibilities. Beating to windward back from the asteroid belt with cargo aboard, for example.

Failing that, the return journey could be made by sailing downwind to Jupiter for a slingshot back towards Earth - all without the need for chemical fueled rocket propulsion. A 21st or 22nd century equivalent of the Atlantic trade routes is a real possibility. Solar propelled ships bringing precious ore or refined goods back from the New Colonies. Tempting targets for space pirates.

The Twisted Genius

Barbara Ann,

I thought these things were just downwind or down sun sails myself, like hoisting a poncho with a couple of poles on a canoe to cross a lake. In the vacuum of space there would be nothing for a keel or centerboard to create the needed resistance for a solar sail to beat to windward. However, according to the Planetary Society and Bill Nye, LightSail 2 can gain some momentum tacking towards the Sun by angling the sail. Angular momentum is probably not the right descriptor, but it's like ricocheting a ball off a wall. And as you said, these sail powered ships could also use celestial bodies for a gravitational slingshot effect. We'd be using gravitational tide tables to pilot across the heavens. The concept does feed the imagination.


Shouldn’t a sail function as a sail in either water with a keel or the vacuum of Space without one ? A space anchor might be more difficult to envisage.
On a cost basis entire fleets could be justified to move non time sensitive material around the Solar System.
A potential means for Satellites, Landers and Rovers constructed beyond Earth’s gravitational field to be delivered to a target gravitational field to perform work.

The Twisted Genius


No, the physics governing light sailing, especially in the vacuum of space, is very different from the physics of sailing atmospheric wind currents on the water, ice or land. Light and light sails do not react to the venturi effect. Nor does a keel or daggerboard offer any kind of lateral resistance in the vacuum of space. It's much like rocket flight dynamics in space is very different than aircraft flight dynamics in the atmosphere. You're right about the space anchor, though.


Thanks for this post, TTG. I remember reading this story from Arthur C. Clarke in my younger years:


It fired my imagination, for sure. Finding various ways to exploit this technology certainly is a meritorious notion.


It has been almost 11 years since the first solar sail launch - Ikaros. And six years since JAXA lost contact probably due to it going into hibernation mode. Wonder where it is now? Perhaps still in solar orbit? JAXA had been planning another, Okeanos, a hybrid with both a solar sail and an ion engine. It would have gone way beyond the asteroid belt to the Trojan asteroids in Jupiter's orbit. It was to have a 1600 sq meter sail, and it was to have a 100 kg lander to pick up rock samples to return to earth. An ambitious program, but unfortunately that proposal lost out to LiteBIRD, a completely different non solar sail mission. But maybe in the future?


Regarding NEA Scout, I could not find any data on the payload weight. But it is only breadbox size and needs an 80 sq meter sail. That sail is only five percent of the area of Okeanos.

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