The venture to clean the outer space

Last month, IAI received a warning about the high danger of a collision between the Venus satellite of the Israeli and French space agencies and the Terra satellite of the American space agency. Beyond the fact that the collision, which was avoided, could have harmed the continued operation of these satellites (the Israeli-French is conducting aerial photographs of Israel and the American is mapping the climate and its changes), it illustrates the great density that exists today in space around the Earth. One of the main reasons for this density is a growing problem that worries space agencies around the world today: space debris.

Since the first artificial satellite, Sputnik 1, was launched into space 63 years ago, humans have launched over 9,000 different spacecraft and satellites, which have been and are used by us today for communication, research, espionage, weather forecasting and more. However, this also led to the creation of a lot of debris: disused satellites floating out of the atmosphere, remnants of missiles and launchers and pieces of forgotten equipment from research spacecraft. All of these are accumulating in space, around the Earth, and can hit active satellites and even manned spacecraft.

Now, the European Space Agency (ESA) has chosen the Swiss company ClearSpace to lead the first-ever space clearing mission.

“The dimensions of space debris can range from the size of a nail to the size of a truck,” said Prof. Yoav Yair, dean of the School of Sustainability at the Interdisciplinary Center in Herzliya, who previously coordinated the Midex project – the Israeli experiment conducted by astronauts on the space agency Columbia. . According to the European Space Agency, there are about 900,000 waste items in the space of one centimeter or more, and more than 130 million items in the size of a millimeter or more.

According to Yair, even such tiny waste particles pose a risk. “These objects move at a speed that can reach 32,000 kilometers per hour, so they have tremendous kinetic energy,” he says. “As a result, even a particle the size of a screw that hits a spacecraft or satellite can damage and even destroy them.”

Why was the space debris problem created in the first place? “Due to myopia, we did not plan the spacecraft in advance so that they would destroy themselves at the end of the operation,” says Yair. “They just didn’t see it as a problem that needed to be addressed.”

According to the Kessler model, developed in 1978 by scientist Donald J. Kassler from NASA, the more debris there is in space, the greater the incidence of collisions between the items. This will cause more and more of the items to break, and the space will be flooded with countless tiny fragments – a situation that could completely block the possibility of launching satellites or manned spaceflights into low orbit. “Where satellites went out of action as a result of a piece of debris being damaged,” says Yair. “If we do not clean up the space, the risk of something bad happening will intensify.”

Cleaning up space debris is not a simple task – you can not just sweep, vacuum or move a rag like at home. Since the 1970s, NASA has been examining various proposals for ways in which this can be done: a special ring that will be placed on the debris item, nets that will wrap the particles and pull them out of place, a metal cable that will pull debris with the Earth’s magnetic field and even a satellite. Large waste and will be adhered to it using “space glue” however, so far none of them has been actually applied.

In November 2020, ClearSpace signed a $ 104 million contract with the European Space Agency, under which it will lead the first mission to remove a waste item from space. To this end, the company has developed the ClearSpace-1 spacecraft, which weighs 500 kilograms and has four robotic arms. In its first mission, scheduled for 2025, the spacecraft will capture and deploy the VESPA (Vega Secondary Payload Adapter), part of a system used to carry and place satellites in space and owned by the European Space Agency. This is an object that weighs 112 kilograms and is similar in size to that of a small satellite (that is, slightly larger than a washing machine), which was launched in 2013 and is currently hovering at an altitude of about 660 kilometers.

According to the plan, the ClearSpace-1 spacecraft will first be launched into a 500-kilometer-high orbit, where critical tests will be performed, and then it will ascend to the target orbit – and capture VESPA with its four arms. In the last stage, the two objects will together make a controlled entry into the atmosphere, during which both will be burned.

Large objects like VESPA pose a threat not only to the objects in space, but also to the humans living on Earth. “The parts of the debris do not stay in the same orbit all the time, the gravity of the earth pulls them further and further towards the atmosphere,” says Yair. “If they reach the atmosphere, the small particles burn in it – but the large objects may survive entering it, and act like meteorites. The damage they are capable of causing on Earth could be enormous.”

As a result, all waste items in space are currently continuously monitored and mapped. “There are programs that predict potential collisions with debris based on surveillance that has been underway for decades, in order to give as early a warning as possible,” says Yair. “Beyond that, in order to prevent damage to the Earth, it is necessary to accurately follow the decay times – lowering the trajectory of the debris in space towards the atmosphere – especially when it comes to large objects.”

In very rare cases, the spacecraft can return to Earth on its own. Thus, in 2001, when the Mir space station completed its mission, it entered the atmosphere in a pre-planned orbit so that it would pass over as uninhabited an area as possible, disintegrating over the South Pacific, without harming property or human life.

Another way to deal with the problem is to plan in advance the end of life of the object launched into space. “Entrepreneur Elon Musk’s SpaceX company, for example, manufactures a launcher that lands after launch: after it accelerates the missile and satellite and completes its function, it makes a controlled landing,” says Yair. “This way you can recycle the tool and prevent dirt and debris.”

“Today, anyone interested in launching a satellite or spacecraft should present a plan detailing the end-of-life planning of what is being launched,” Yair adds. “Recently, more and more companies are planning to ‘hunt’ the satellites that have completed their operations and bring them back to Earth in a complete way: repair them, replace them with batteries, refurbish them, take care of their computers and more, and then launch them again. This is a new field that is evolving.” , He concludes.