Just last week, March 11, 2021, the International Space Station threw a huge piece of space junk. It's a set of discarded nickel-metal hydride batteries, the size of an SUV and weighing up to 2.9 tons, making it the heaviest space junk ever discarded on the International Space Station. Well, really high-altitude projectiles!
NASA said the piece of space junk would not pose an impact threat to other space objects, and even so, the U.S. Space Command would keep track of it. In addition, it will operate in low Earth orbit for 2-4 years, eventually falling into the atmosphere under the weak air resistance and burning.
In fact, such a high-altitude projectile on the International Space Station is also a helpless move. This matter has to start from the battery replacement of the International Space Station.
Batteries on the International Space Station are rechargeable batteries used to store energy collected by solar panels. As early as 2011, NASA decided to replace these batteries, replacing the original 48 nickel-metal hydride batteries with 24 lithium-ion batteries.
Changing the battery in heaven is not an easy task. The work lasted four years, began in 2016, and was not completed until February 1, 2021, when astronauts Mike Hopkins and Victor Glover completed the spacewalk mission. During this period, the Japanese HTV cargo spacecraft carried out a total of 4 cargo supply missions, and 13 astronauts carried out a total of 14 spacewalk missions.
Originally, each set of old batteries would be loaded into the HTV cargo spacecraft and then taken to the atmosphere to be burned.
However, in October 2018, the Russian Alliance MS-10 mission failed to launch, and the escape procedure was urgently launched. Fortunately, two russian cosmonauts, Alexei Ovcchinin and American Nick Hague, managed to survive.
The failed launch disrupted the ISS battery replacement program, leaving an HTV cargo spacecraft without a discarded battery when it left the ISS. In this way, an additional set of discarded batteries was added to the International Space Station. The HTV cargo spacecraft happens to be retired in 2020, and the next generation of HTV-X cargo spacecraft will not be in service until at least 2022.
Therefore, after some evaluation, the administrator of the International Space Station decided to throw the discarded batteries into low Earth orbit after some evaluation. On March 11, 2021, ground crews at NASA's Johnson Space Center operated a 17.6-meter-long robotic arm from the International Space Station Orbit laboratory to deliver the batteries into low-Earth orbit.
In this regard, a new member of the huge space junk team was added.
In fact, the space junk generated by the International Space Station is just the tip of the iceberg, mainly from scrapped satellites, wreckage left over from rocket launches, and anti-satellite weapons tests.
Since the soviet union launched Sputnik 1, the first artificial satellite of mankind, in 1957, more than 4,000 launch missions have been carried out around the world, and space junk has also increased day by day, becoming an international problem that cannot be ignored.
According to the European Space Agency, the space junk currently orbiting the Earth is very amazing, with about 34,000 more than 10 centimeters in size and up to 128 million in size over 1 millimeter, and the number is still growing rapidly.
The speed of space junk can exceed 7 km /s, and the kinetic energy is huge and destructive. It poses a serious potential threat to satellites, spacecraft, space stations, and even astronauts. According to calculations, the impact of space junk at the millimeter level may stop the spacecraft from working; space junk with a size of 10 centimeters can completely destroy the spacecraft.
Friends who have watched the science fiction film "Gravity" should be impressed by this. In the film, the space station is hit by space junk, causing a devastating disaster.
So, what are the countermeasures for human beings to deal with space junk? There are three main directions for the solution.
First, space alert: maintain close monitoring and tracking of space junk to ensure that spacecraft can be evaded in time. Agencies such as the U.S. Space Monitoring Network and the Russian Space Monitoring System will catalog and monitor space junk over 10 centimeters in real time.
Second, active cleanup: some space junk will enter the atmosphere and burn due to weak air resistance or solar activity, but others will permanently run in the Earth's orbit, and humans must take the initiative to clean up. For example, many countries are studying fishing net methods for capturing space junk.
Third, independent destruction: it is necessary to treat the symptoms, but also to cure the root causes. To deal with space junk, we must start from the source, and we should try to ensure that the spacecraft reserves sufficient power when it is scrapped to re-enter the atmosphere and burn it independently. In the future, this must become an international consensus.
Here, it is necessary to mention SpaceX's Starlink program.
We know that the Starlink program is an ambitious plan of SpaceX to provide high-speed Internet access with a constellation of satellites in low-Earth orbit that could eventually reach a staggering 42,000 satellites.
Many people directly put the satellite of the starlink with the hat of space junk, they may not know that each starlink satellite is equipped with Hall thrusters, with the ability to change orbit autonomously, and can re-enter the atmosphere and burn when scrapped.