Millions of pieces of debris currently orbit the Earth — and more than 27,000 pieces of space debris are larger than the size of a softball.
Prof. Jake J. Abbott and his team at the University of Utah are testing out a way to sweep up the mess:
The many rocket parts, paint flecks, satellite components, and spacecraft pieces found in low Earth orbit (LEO) can reach speeds of 18,000 miles per hour, almost seven times faster than a bullet . A collision at that rate could damage a spacecraft and pose a risk to human explorers.
The complexity of the space-debris challenge has led to many "out-of-the-box," un-conventional ideas, including a harpoon.
University of Utah mechanical engineering professor Jake J. Abbott is leading another inventive effort: to carefully manipulate orbiting debris with moving magnets.
Using multiple, rotating magnetic-field sources, the researchers demonstrated the movement of a target object in six degrees, including rotation.
“What we wanted to do was to manipulate the thing, not just shove it, but actually manipulate it like you do on Earth,” said Abbott in a recent news release . “That form of dexterous manipulation has never been done before.”
To test their research, the engineers made a kind of simulation of slow-moving objects in microgravity: a copper ball on a plastic raft in a tank of water.
Shown in the video below, Abbott and his team used four "Omnimagnets," located beneath the tank of water, to manipulate the sphere along a square trajectory. The Omnimagnets contain three electromagnets, all centered at the same point in space but pointing in three different directions.
"We are not controlling the orientation in this video," Abbott told Tech Briefs, "so you can see the raft rotate out of control as it is moved."
Such handling supports space applications that call for careful manipulation, including the repair of damaged satellites. The newly discovered process, according to the Utah professor, could be used with a spinning magnet on a robotic arm.
“You have to take this crazy object floating in space, and you have to get it into a position where it can be manipulated by a robot arm,” Abbott says. “But if it’s spinning out of control, you could break the robot arm doing that, which would just create more debris.”
The changing magnetic field turns the piece of debris, essentially, into an electromagnet that creates torque and force, which allows movement of the debris without having to physically grab it.
With this technology, robots could one day gently maneuver the scrap to a decaying orbit or further out into space without actually touching it, or they could repair malfunctioning objects to extend their life.
The team's research is detailed in the paper, “Dexterous magnetic manipulation of conductive non-magnetic objects ,” published this month in the science journal, Nature. The co-authors include U graduate students Lan Pham, Griffin Tabor and Ashkan Pourkand, former graduate student Jacob L. B. Aman, and U School of Computing associate professor Tucker Hermans.
In a short Q&A with Tech Briefs below, Abbott explores applications that he envisions when magnets are sent to space.
Tech Briefs: How big is the space debris problem?
Prof. Jake Abbott: In short, there are thousands of pieces of debris. Some are satellites that no longer work. Some are parts from spacecraft that came from the normal launch process, and some are parts from collisions that have already happed. The problem with space debris is that it makes more space debris. (Visit NASA's Orbital Debris Program Office .)
Tech Briefs: Space debris has led to out-of-the-box ideas, like robotic grippers and space “harpoons.” What inspired you and your team to think about using magnets?
Prof. Abbott: The problem with space debris is many objects of interest are spinning out of control, so it is difficult to safely grab them with some more traditional robot (you’ll just make more debris!).
I’ve spent the better part of my professional career thinking about how to use magnetic fields to manipulate objects without touching them, starting from my postdoctoral work at ETH Zurich. We’re usually motivated by manipulating objects inside the human body for next-generation medical robots, and the things we’re manipulating have always been magnetic materials (for example, permanent magnets as well as metals that become magnetized when subjected to an applied field). Space debris is largely made of non-magnetic metals like aluminum. Others have previously explored how to use magnetic fields to slow down spinning objects in space. I thought, if my team applied ourselves to this problem, we might be able to figure out a way to use the same physics to dexterously manipulate objects.
Tech Briefs: How do you test an idea like this (on Earth)?
Prof. Abbott: We developed models of the forces and torques that are generated on conductive metallic spheres using a combination of finite-element simulations and experiments in which we placed a metal sphere on a force-torque sensor, and then placed a spinning permanent magnet near it. Once we were equipped with a force-torque model, we developed an algorithmic framework for manipulation. We tested and tuned our method in numerical simulations in microgravity. Then, once we were happy with the results, we developed a simple microgravity simulator based on a raft (which held a metal ball, about the size of a golf ball) floating on the surface of water, which enabled us to show that we could independently control the position and rotation of the object. To manipulate it, we used four electromagnetic field sources known as Omnimagnets (a previous invention from our group).
Tech Briefs: What is the “upside” of using magnets compared to other methods? (What are the “downsides?”)
Prof. Abbott: The upside is you can manipulate an object gently and with no physical contact. The downside is that the forces and torques will be very small over even a moderate distance, which means manipulation will happen very slowly.
Tech Briefs: How do you see this kind of cleanup being carried out – in its ideal form? What technology components get brought up to space, what gets sent out into orbit, and how is the debris cleared?
Prof. Abbott: A spacecraft (probably robotic) would approach a target object and get into a synchronous orbit with it. Assuming there is some rotation of the target object, we would de-tumble it until there is no relative rotation of the object with the respect to the spacecraft. Once the object can be safely approached, it has to be made to slow down so that it will decay into the atmosphere and burn up or fall in the ocean. This could happen by attaching some other object to the debris with this specialized purpose, or it could potentially happen by applying forces using the same methods that we used to de-tumble it.
Tech Briefs: What needs to happen for this idea to be tried out in space?
Prof. Abbott: Somebody would need to have the desire and funding to try a test in space. I’m looking for partners now. I’m also seeking federal funding to continue to explore different aspects of this problem in my lab at the University of Utah.
In our past efforts, we created an accurate model of metallic spheres, which is the simplest possible geometry, and then used that model explicitly in our manipulation. We are now considering manipulation of objects for which we do not have a good model before we begin manipulating it.
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