What should I do if the satellite breaks down in space?

When satellite components in space are damaged or fuel is exhausted, it often means that their service life will also end. In order to give satellites longer service life, NASA has proposed a potential solution, which is to send orbiting robots to repair or refuel.

Over the past 20 years, the U.S. Landsat-7 satellite has orbited the Earth every 99 minutes and captured images of almost all of the Earth's surface every 16 days. One of many spacecraft observing changes on Earth, it has revealed melting glaciers in Greenland, the expansion of shrimp farms in Mexico and deforestation in Papua New Guinea. But after Landsat 7 runs out of fuel, its useful life will be over because there is currently no way to refuel it in space.

However, NASA has proposed potential solutions for this. In a few years, the agency plans to launch an orbiting robot into space and maneuver it into grasping range of Landsat 7. The robot will use a robotic arm to grab the satellite and refuel it in space. If successful, the mission will mark a new milestone as the first time a satellite has been refueled in space. The mission is just one of many public-private initiatives that intend to use robots to repair and improve billions of dollars worth of satellites in orbit.

Ultimately, such efforts could lead to better, cheaper satellites that could lower the cost of internet and cell phone networks, provide better weather forecasts, and provide unprecedented visibility into changes on Earth and the universe perspective. They may even kick off a new wave of on-orbit construction, using armies of robots to build satellites, space stations, and even spacecraft to Mars.

Giving satellites longer life

Currently, there are approximately 4,852 operating satellites in orbit, playing a vital role in communications, remote sensing and other tasks. But everyone knows that if these satellites are damaged, there is now almost no way to repair them. At the same time, most satellites occasionally require fuel to adjust their orbits. When the fuel is depleted, they can become space junk, further adding to the massive debris stream circling the Earth.

Brian Weeden, head of the space services industry group Concers, said: "Imagine you are going to buy a car tomorrow. But you have to remember that you can never buy it again. Fill it with more gas, never change the oil, and never maintain or repair anything. And you'll have to use it for the next 10 years. Now, how expensive and complicated do you think this car will be? "This is similar to what we're doing with satellites," said Carl Glen Henshaw, director of the Robotics and Machine Learning Division at the U.S. Naval Research Laboratory. "What we really want to do is. , deploying robotic mechanics in space to repair satellites when they malfunction."

Robotic rescue faces many challenges

Over the past few decades, researchers have Great progress has been made towards this goal. In a 2007 NASA demonstration project, two purpose-built vehicles resided in orbit and performed fuel transfers. Most recently, in 2020, aerospace company Northrop Grumman successfully launched two "mission extension vehicles" equipped with engines and fuel that attached to two commercial satellites and pushed the latter Entered a new track.

Two new missions expected to launch over the next decade promise to take on-orbit maintenance to the next level. The demonstration project will use semi-autonomous robots equipped with robotic arms to refuel satellites in orbit and even perform simple repairs.

Henshaw is working on robotic maintenance services for geostationary satellites as a project funded by the U.S. Defense Advanced Research Projects Agency (DARPA). If the demonstration mission, scheduled for 2024, is successful, it will mark the first time a robotic spacecraft has successfully captured a satellite that was not specifically designed to dock with it. Henshaw and colleagues recently explored the challenges of using space-based robots to repair satellites in the Annual Review of Control, Robotics, and Autonomous Systems.

Such challenges abound. Since existing satellites were never intended for repair, they lack markers called fiducials, which would make it less easy for robots to visually locate a moving satellite. At the same time, satellites do not have grabbing devices specifically designed for robots, and protruding parts on satellites are often too fragile to grab, such as antennas and solar panels.

Another problem is the time delay in communication between the robot and the Earth control team. For a robot operating in geosynchronous orbit at an altitude of about 35,000 kilometers, distance and signal processing create a communication delay of several seconds between the robot and its controller on Earth, so the robot will need to handle the most critical tasks autonomously. Task. Fortunately, this work can build on existing robotic arms in space, including the two currently in use on the International Space Station.

In a demonstration mission, Henshaw and his fellow engineers plan to select one of thousands of older, no longer active satellites still parked in remote orbits. . The robot will use cameras and laser rangefinders to match its robot to the satellite and maneuver to within approximately 2 meters of the satellite. When close enough, the robot uses one of its two robotic arms to grab the aluminum ring that previously held the satellite to the launch vehicle.

Meanwhile, another robotic arm will be responsible for detecting solar panels or antennas that fail to unfold correctly, a problem that occurs every two to three years. In addition, the arm can attach new instruments to the outside of the satellite, such as more powerful transmitters, cameras or antennas.

NASA’s ambitions

Sometime after 2025, NASA plans to launch an even more ambitious robot called On-orbit Maintenance, Assembly and Manufacturing 1 (OSAM-1) ) robot, which will first be responsible for refueling existing satellites. OSAM-1 will then demonstrate whether entirely new structures can be built in space.

Landsat 7 will be OSAM-1’s first refueling mission. The satellite was launched by the US Geological Survey in 1999 and entered low-Earth orbit at an altitude of about 700 kilometers. Its work has been taken over by more advanced satellites, but it provides scientists with the opportunity to test robotic refueling in orbit. Brent Robertson, NASA's OSAM-1 project manager, said: "More than 20 years ago, technicians usually refueled satellites before preparing for launch, and they never thought about refueling them again."

OSAM-1 will use a robotic arm to cut through the insulation, snip two wires, unscrew the bolts, then connect hoses and inject 115 kilograms of fuel, Robertson said. While servicing existing satellites is the most immediate goal of robots, assembling and manufacturing satellites in orbit may be more important in the long term. For example, OSAM-1 has an additional mission where it will carry a separate robot called SPIDER designed to demonstrate the ability to assemble things in space. SPIDER's first mission will be to assemble the seven-piece, 3-meter-long antenna and send it into orbit.

Using a similar process to 3D printing, OSAM-1 will also demonstrate that it can make structural components from scratch, creating strong yet lightweight composite beams from carbon fiber spools and other textiles. Parts like this can be connected to form the structural components necessary for satellites or other orbital structures.

If the missions currently being planned are successful, robotics could usher in a new era of space construction, helping to build more spacious space tourism stations, space fuel depots, and support space mining operations and even manufacturing in orbit. A spaceship heading to Mars. "We want to show that we can make these things even though no one has done it before," Robertson said. "If you have the ability to assemble something in space, you can bring your own materials or have them sent to you to build more. Large man-made objects.

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