NASA has launched the latest attempt to test solar sail propulsion technology.
The Advanced Composite Solar Sail System (ACS3), comprised of a microwave-oven-sized CubeSat and a solar sail, lifted off aboard a Rocket Lab Electron rocket from Launch Complex I on New Zealand’s Mahia Peninsula. . After reaching 600 miles above Earth, ACS3 released its sail.
The ACS3’s solar sail is made from a reflective polymer and supported by a boom made from carbon fiber composite material. Previous solar sail tests used metal spears that tended to warp due to the extreme temperatures of space. The sail is 680 square feet in area.
The goal of ACS3 is modest: use the solar sail to raise and lower the spacecraft’s orbit. But the technology could lead to the creation of sailing ships in the skies, which use the pressure of sunlight to fly around the solar system and even visit other star systems.
A spacecraft that uses a solar sail has advantages and disadvantages compared to those powered by rockets.
A spacecraft powered by a solar sail has three main advantages. First, it saves engine mass and rocket fuel. Secondly, it can theoretically fly forever if the solar sail remains intact and undamaged. Finally, although such a spacecraft would accelerate very slowly, the acceleration would be constant. As time passed, it would increase to incredible speeds.
Disadvantages of solar sails include that they are less effective the further from the sun they get, tend to be large and unwieldy, and susceptible to damage from even the smallest space debris, natural or man-made.
Still, a working solar sail system creates a range of possibilities for inexpensive planetary missions.
A recent study published on Phys.org suggested that a probe powered by a solar sail could reach Mars in just 26 days. On the other hand, surveys using conventional rockets take between 7 and 9 months. A combination of aerobraking and a conventional rocket would be used to insert the probe into orbit around Mars.
The University of California at Berkeley has proposed sending fleets of probes using solar sails to visit near-Earth asteroids and comets. The Berkeley Low-cost Interplanetary Solar Sail project, or BLISS, envisions swarms of these small craft sailing to these objects and obtaining high-resolution images of them.
Near-Earth objects are interesting for two reasons.
First, asteroids and comets whose orbits intersect Earth’s could provide valuable resources that fuel space industries. The type of solar sail-powered probe that BLISS envisions could discover where these objects are and their orbits.
Secondly, these objects can be a danger to the Earth and all living beings that inhabit it. More than 60 million years ago, an asteroid hit Earth and put an end to the age of dinosaurs. A similar object could do the same to the human species. Detecting objects approaching Earth and measuring their orbits and the likelihood that they will collide with our planet can give us time to prepare to deflect an object on its path to wipe out humanity.
How about using light sails to send probes beyond our solar system, say, to the Alpha Centauri system? Space.com recently discussed two studies for this mission.
The innovative Starshot envisions using lasers on Earth to accelerate a microchip-sized probe to 20% the speed of light. The probe would reach the vicinity of Alpha Centauri in just 20 years. Two studies discuss the type of materials from which a solar sail would be constructed and the shape of the sail that would ensure it would survive long enough to accelerate the probe so that it could cross interstellar distances within a human lifetime.
The idea of solar sails has been the subject of science fiction and speculation for many decades. Aside from test flights like ACS3, the technology has yet to be used seriously.
If spacecraft with solar sails ever set sail for interstellar destinations, they will convey the romance of the golden age of sailing Earth’s oceans to space travel. They will be like the clipper ships and galleons that once transported cargo and people around the world before the advent of coal, diesel and then nuclear energy.
Mark R. Whittington, who writes frequently about space policy, published a policy study on space exploration titled “Why is it so difficult to return to the Moon?” like this “The Moon, Mars and beyond”, and, more recently, “Why is America going back to the Moon?”He blogs at Corner of the Curmudgeons.
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