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Taking a drag
Of the numerous competing ideas for mitigating area junk, drag sails are one of the crucial intuitive. They’re artificial sails deployed from a spacecraft to create extra drag when its mission ends, slowing and deorbiting the craft earlier than would in any other case be doable.
“Drag sails work through the use of the slightest, thinnest layers of environment, present on the greater ranges, as a mechanism that may hit the sail and decelerate the spacecraft,” says Rohan Sood, director of UA’s Astrodynamics and Area Analysis Laboratory. “We’re deploying a sail that’s perpendicular to the path of the spacecraft’s movement, which slows down and deorbits the craft.”
One of many first craft to display the idea was NASA’s Nanosail-D2, a water bottle-sized nanosatellite that deployed a 108-square-foot (10 sq. meters) sail in 2011. As a substitute of taking an estimated 50 years to fall to Earth from its 400-mile-high (650 kilometers) orbit, the satellite tv for pc reentered the environment and burned up in lower than one yr.
As a result of drag sails work passively, utilizing nothing however atmospheric resistance, drag sails current a novel technique of stopping future area junk. Competing deorbiting applied sciences like electrical propulsion — utilized by SpaceX of their Starlink constellation — require an influence supply onboard the spacecraft, which might be susceptible to problems.
“If the spacecraft works effectively all over the mission, that’s superb, but when that host spacecraft dies or loses performance, that electrical propulsion system isn’t going to be efficient in deorbiting,” says David Spencer, a Mission Programs Supervisor with NASA’s Jet Propulsion Laboratory and director of Purdue’s Area Flight Initiatives Laboratory. “That’s the place drag sails present a extra fail-safe method, in our opinion.” (For its half, SpaceX says it doesn’t fly Starlink satellites any greater than 370 miles [600 km], which reduces the time that inoperable craft deorbit to 5 – 6 years.)
The idea is intuitive sufficient in principle, however the important thing problem is designing the deployment system, Spencer says. “We’ve bought these lengthy booms which might be stowed in a really tight space, we’ve bought giant sail supplies that must be crammed in these small storage compartments for years, and when that deployment command comes, all of it has to work correctly.”
Even efficiently deployed drag sails might encounter issues as orbits decay and spacecraft cross into decrease, denser areas of the environment. When this occurs, drag sails should stay perpendicular to the movement of the craft to maintain impact. “If the sail begins to tumble and is now not perpendicular, the drag impact decreases, and whether it is parallel, may be zero,” Sood says. “So, the problem can also be controlling the angle of the sail.”
Spacecraft usually use lively strategies of angle management, which require a supply of energy — like thrusters or response wheels. However a drag sail for a defunct satellite tv for pc wouldn’t be capable of depend on having energy.
Spencer’s staff turned to badminton for inspiration. Their Spinnaker-1 sail mannequin takes the form of a pyramid as soon as it’s deployed. “That pyramid acts like a shuttlecock would,” says Spencer, which routinely turns the automobile to the orientation that gives most drag.
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