{"id":4781,"date":"2012-12-11T06:00:02","date_gmt":"2012-12-11T11:00:02","guid":{"rendered":"http:\/\/www.allandouglas.com\/blog\/?p=4781"},"modified":"2025-04-21T01:56:41","modified_gmt":"2025-04-21T05:56:41","slug":"scifi-propulsion-exotic","status":"publish","type":"post","link":"https:\/\/pineymountainfoster.org\/thoughts\/scifi-propulsion-exotic\/","title":{"rendered":"Science Fiction Fact and Fancy: Propulsion-Exotic"},"content":{"rendered":"

This week I will continue with my examination of space travel technology, focusing on propulsion; but this time looking at the less commonly discussed and written about technologies.\u00a0 Again, I remind you, reader, that I want only to help understand current theory – perhaps open some doors – not quash your imagination.<\/p>\n

Solar Sail Propulsion<\/h1>\n
\"solar<\/a>
via www.NASA.gov<\/figcaption><\/figure>\n

As a sailboat enthusiast from way back I know well the elegance and economies of using wind to power a craft.\u00a0 But light?\u00a0 Yes.<\/p>\n

The idea of powering spacecraft with sails harnessing the \u201csolar wind\u201d was first proposed by Johannes Kepler<\/a> who observed that comet tails point away from the Sun and suggested that the sun caused this effect. In a letter to Galileo in 1610, he wrote, “Provide ships or sails adapted to the heavenly breezes, and there will be some who will brave even that void.” [1<\/a>]<\/sup><\/p>\n

The technical term is Solar Radiation Pressure and it is made up of photons (light) and elemental gasses.\u00a0 The sails must be mirror-like reflective to utilize the photon energy.\u00a0 Although the SRP or \u201cSolar Wind\u201d blows at (or near) the speed of light, its actual impetus is rather low.\u00a0 It will take HUGE sails to pull a space craft of any size through the heavens.<\/p>\n

Two launch conditions are being considered both assume that the craft itself will be either boosted into orbit on a rocket or built in orbit.<\/p>\n

The first is to unfurl the sails (see video below) and allow the Solar Radiation Pressure to do a slow-but-steady push on the sails.\u00a0 The craft will pick up speed as the SRP continues to \u201cblow\u201d against it.\u00a0 But, high speeds would probably not develop before the craft is so far away from the sun that the push it gets is diminished.\u00a0 Best speed with this is estimated to be 90 km per second (km\/s).\u00a0 A modification of this is to use microwave or laser emplacements to give the craft a \u201cshove\u201d at certain points to bring the speed up to 30,000 \u00a0km\/s (1\/10 the speed of light) and bring interstellar travel into the realm of possibility.<\/p>\n

The second is to allow the craft to fall toward the sun, with its sails angled to a passive state, and perform a slingshot around the sun; swinging the sails into full-on position as it begins departure from the sun.\u00a0 Computer models of this technique show that speeds of 480,000 km\/s could be attained as a departure speed. [2<\/a>]<\/sup><\/p>\n

Fanciful wishing?\u00a0 Not at all; indeed, NASA has already accomplished a test flight with its NanoSail-D<\/a> and the Planetary Society<\/a>, a privately owned foundation, is constructing a model of its own; the Cosmos 1<\/em>, which boasts solar sails that are made of aluminum-reinforced Mylar and are approximately one fourth the thickness of a one-ply plastic trash bag.\u00a0 Many consider this to be the best technology to carry mankind to the stars.<\/p>\n