Solar Sails

Link to the blog where I originally wrote this: https://vinthebestptlr.wixsite.com/small-curiosities-an/post/solar-sails

The idea of using light as a form of power is nothing new. Since the times of the ancient Greeks, humans have known of its heating and illuminating properties. Even the idea of using it to propel spacecraft is in itself quite old; Kepler thought of it as far back as 1610. Even my favorite author, Jules Verne, mentioned light propelling spacecraft in From the Earth to the Moon: "there will some day appear velocities far greater than these [of the planets and the projectile], of which light or electricity will probably be the mechanical agent ... we shall one day travel to the moon, the planets, and the stars."

However, solar sails only entered serious scientific study when NASA began conducting extensive studies on the subject to examine its viability. In 2010, IKAROS from Japan was the first spacecraft to use solar sails as the vehicle’s primary means of transportation. The 14m x 14m sail demonstrated that such a propulsion method was valid and could work in practicality, not just within the realms of theory. (My engineering teacher has a joke regarding this: “In theory practice and theory are the same. In practice they are not”). NASA attempted to launch a satellite with dimensions 30 cm x 10cm x 10cm under the name NanoSail-d but was lost during launch. Though the past has few missions utilizing solar sails NASA has plans for similar projects in the future, including the already launched ACS3 and the future NEA scout, undertakings that will not only further test solar sails but will also expand the space field in other ways, in the case of NEA scout, studying an asteroid.

But the question remains, what exactly is a solar sail, and what promises does it hold? Solar sails are large reflective surfaces, typically aluminum covered by plastic polymers, propelled by photons hitting into them. The design, though seemingly quite simple, complicates itself once the engineer realizes how reflective the surface needs to be for it to work, along with the extreme weight requirements necessary for its operations. The larger the payload, the larger the sail, although both would increase in a linear fashion, meaning the task would still be feasible, if highly expensive and from an engineering view difficult, even for large payloads.

Given this fundamental understanding on how these machines work, what promises and advantages do they hold to the future? Solar sails are, for the most part, fuel free, the only expense of depletable fuel being the launch. Once in space, the sails can accelerate without the need of any energy carried from earth by simply facing in a direction where photons may hit and boost its speed. This unlimited fuel aspect will greatly cut down on the cost of space missions, making them cheaper and more feasible to undertake from a monetary perspective. Solar sails also have the ability to accelerate to speeds beyond the reach of currently used propulsion methods, and are far more maneuverable due to them only needing to adjust the sail’s angle, changing speed and direction. Given these pros, it’s worth considering the cons of these contraptions. Solar sails will take a painfully long time to accelerate, and have access to only a restricted amount of materials which are light yet strong enough for them to be used within the machine. Though both will pose an obstacle in the early days of testing, over time experience will gradually solve both issues, especially the latter one, which I can foresee leading to the creation of a whole new class of light yet strong and reflective materials.

Solar sails are an exciting new technology that will most definitely prove themselves worthy of a high ranking stature within the pantheon of human achievements and innovation. Their propulsion system, not using any depletable source of fuel needing to be carried in the launch, will significantly lower the cost of space missions as well as their range and control. One of man’s initial transportation inventions was the sailboat, which can be dated over five thousand years ago to Egypt and Mesopotamia, to traverse the mighty rivers that crossed and divided-yet-unified that land. Since then we have come a long way, domesticating horses for travel, creating road systems, larger sailing ships, efficient canal designs, steam ships, engines, and locomotives, the rail system, cars, planes, highways, propellers, jet engines, rocket engines, etc. And yet, at the end of it, and at the start of another new era of exploration, the second great expansion of our knowledge of the universe, from the earth to space, we are back to the humble sail. Quite beautiful, poetic, romantic. Our demand to understand the universe we inhabit will never be satiated, and as we sail into the next chapter of exploration, the sail will be our newest and yet simultaneously, our oldest, tool in our kit.