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A recent study was submitted to Acta Astronautica and is now available on the arXiv preprint server. The study explores the potential for using aerographite solar sails for traveling around the solar system and in interstellar space. (Aerographite is a synthetic foam consisting of a porous interconnected network of tubular carbon.) Solar sails could dramatically reduce both the time and fuel required for such missions.
This study comes while ongoing research into the use of solar sails is being conducted by a variety of organizations including the successful LightSail2 mission by the Planetary Society. Solar sails hold the potential to develop faster and more efficient propulsion systems for long-term space missions.
Dr. René Heller is an astrophysicist at the Max Planck Institute for solar system Research and a co-author on the study. He said, “Solar sail propulsion has the potential for rapid delivery of small payloads (sub-kilogram) throughout the solar system. Compared to conventional chemical propulsion, which can bring hundreds of tons of payload to low-Earth orbit and deliver a large fraction of that to the moon, Mars, and beyond, this sounds ridiculously small. But the key value of solar sail technology is speed.”
Conventional rockets rely on fuel in the form of combustion of chemicals to exert an external force out the back of the spacecraft. In contrast, solar sails don’t require fuel. Instead, they use sunlight for their propulsion mechanism. The giant sails catch solar photons much like wind sails catch the wind when traveling across water. The longer the solar sails are deployed, the more solar photons are captured. This gradually increases the speed of the spacecraft.
For the reported study, the researchers conducted simulations on how fast a solar sail made of aerographite with a mass of up to two and two tenths’ pounds could travel. This includes twenty-five ounces of aerographite with a cross sectional area of one hundred- and four-square yards, could reach Mars and the interstellar medium which is also called the heliopause. The heliopause is the point at which the solar wind yields to the interstellar medium. The trip to Mars would involve a trajectory called direct outward transfer. The trip to the heliopause would require a trajectory called an inward transfer method.
The direct outward transfer method for the trip to Mars involved the solar sail both deploying and departing directly from a polar orbit around the Earth. The researchers found that Mars being directly opposite Earth from the sun at the time of solar sail deployment and departure from Earth would yield the best results for both velocity and travel time. This same polar orbit deployment and departure method was also tested for the heliopause trajectory
. For the inward transfer method, the solar sail would be launched to about six tenths of an astronomical unit (AU) from the sun via traditional chemical rockets. (An AU is the distance of the Earth from the Sun.) Then, the solar sail would deploy and begin its journey to Mars or the heliopause. The reported study considers how an aerographite solar sail would make this journey more feasible.
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