New tricks for space processing: turning spacecraft debris into treasure

Recently, a Falcon 9 rocket from the United States launched a large number of commercial payloads. One of the payloads only operated in space for a few hours before re-entering the atmosphere and burning up. However, it attracted great attention from the aerospace community, which believed that it could play an important role in future Mars missions and the space manufacturing industry, and help with the recycling of space junk.

Cost-saving space gold rush

The mission is called "Mars Outpost Demonstration-1", and the payload is relatively simple, not even a complete satellite, but just a functional module. "Outpost" implies that the Mars mission is more like looking forward to a long-term goal. According to the project initiator, the primary goal of the mission payload is to demonstrate cutting metal in space without producing chips.

Anyone who has ever been involved in metal cutting knows that no matter what material the tool is made of, as long as it comes into contact with metal at high speed, it will inevitably peel off a small part of the metal and turn it into tiny metal chips. In a machining workshop, a large amount of chips are generated every day, which is also the main source of solid waste in the factory.

On Earth, these metal scraps can be used as metallurgical raw materials and added to the large cycle of the machinery manufacturing industry. However, there is no large-scale waste collection service in space, and in a microgravity environment, if metal cutting is performed in the traditional way, the chips will fly at a speed of several kilometers per second, which is probably more powerful than machine gun bullets.

So why cut metal in space? Because the project initiator believes that the current human spacecraft manufacturing model is too expensive! Whether it is a satellite, deep space probe, spacecraft, or space station, they are all built on the earth and launched into space. Once they reach the end of their life, they often become space junk and are difficult to recycle. Most of the materials on the spacecraft are high-performance and high-value, so it would be a pity to discard them directly. In addition, in order to send spacecraft into space, rocket upper stages are often used, which increases costs. Rockets need to consume a large amount of expensive aerospace propellants to send large-mass spacecraft into space and enable them to reach sufficient speed and orbit.

As commercial spaceflight is in full swing, cost saving has gradually attracted the attention of space industry players. SpaceX and other companies in the United States have already achieved the recovery and reuse of the first stage of rockets, so can the scrapped spacecraft in orbit also be considered to be "turned into treasure"?

Manufacturing and recycling spacecraft in orbit in a space environment has been a long-term research topic in the aerospace industry, but it is still far from being formally put into practice on a large scale. After all, the difficulty in this regard is much greater than recycling electronic products on Earth.

As a highly integrated and extremely complex industrial product, spacecraft is composed of countless electronic components and precision mechanical parts, using metals, ceramics, rubber and various composite materials. Taking metal as an example, it includes aluminum alloy, the main material of the spacecraft structure, as well as alloy steel and titanium alloy. In some places, precious metals such as gold, silver and platinum are also used. With the development of aerospace electronic equipment, in addition to the use of traditional metal materials such as copper and zinc, power supply devices such as lithium batteries are becoming more and more complex.

Theoretically, the space "gold rush" activity has great "money" prospects. The most popular item should be circuit boards, because the contacts of electronic devices need to be coated with gold, silver, platinum, etc. As long as they are dissolved and refined with special liquids, there is hope of obtaining a large amount of precious metals.

Unfortunately, the huge profits are accompanied by great difficulties. On Earth, recycling used electronic products is cumbersome and complicated, and the disassembly and decomposition operations alone require a lot of manpower. But this is unrealistic in space, especially when decomposing materials with different properties, astronauts will face great risks. We can only hope that artificial intelligence technology will advance to a new stage.

The hidden secret of rocket cutting simulation

Michelle Smith, senior vice president of NanoStack, the initiator of the Mars Sentinel Validation-1 mission, said: "If humans want to go into deep space, to Mars or other places, they must build spacecraft in space, rather than relying entirely on launching all parts from the ground and then assembling them. The Mars Sentinel Validation-1 mission is the first step toward this goal. In the future, there will be more payloads to verify space metal cutting, welding and other technologies." To further reduce costs, it is also not necessary for all of these metals to be launched from the ground, as space junk provides sufficient raw materials.

According to reports, the "Mars Outpost Verification-1" functional module includes six components: measurement and control antenna, measurement and control radio equipment, payload, payload antenna, payload radio equipment and service platform. Among them, the service platform can provide power, thermal control and structural support for the payload. The entire module is quite simple, and it does not even have an attitude control subsystem.

The service platform does not have common solar panels, but only two lithium batteries, which means it cannot work in orbit for a long time, and the effective demonstration time in this mission does not exceed 10 minutes.

Specifically, the payload of the Mars Outpost Validation-1 is a sealed box containing three corrosion-resistant steel samples, made of the same material as the upper stage shell of the Vulcan-Centaur rocket that the United States is about to launch, and is about the size of a shopping mall coupon. The most important equipment is a robotic arm developed by Maxar Corporation of the United States, with a cutting tool at the front end that can rotate at high speed and use the high temperature generated by friction to cut the corrosion-resistant steel, with almost no chips.

According to the operation site video provided by two cameras, the robotic arm cut three metal samples along a curved path. The infrared thermal sensor collected data at all times and monitored the entire test process. The video and data were sent back to Earth in a timely manner.

In the next stage, NanoStack plans to conduct similar experiments in a sun-synchronous orbit with an apogee of 538 kilometers, a perigee of 531 kilometers, and an inclination of 97.5 degrees. Future processing targets will include scrapped sun-synchronous orbit satellites.

According to the test materials, NanoStack is targeting rocket upper stages as the object of space cutting and processing for the sake of caution. The structure of rocket upper stages is relatively simple. Although there are some electronic components, the main body is still cylindrical metal components such as shells, tanks, and engines. The main materials are aluminum alloy and alloy steel, which is more feasible to process with robots.

In fact, cutting the rocket upper stage into pieces is only the first step - obtaining raw materials for space manufacturing. Next, we can consider transforming the rocket upper stage into a new spacecraft, but the difficulty is quite great. After all, the design and manufacture of spacecraft are inseparable from complex processes and procedures, which are difficult tasks on Earth. If we use waste equipment to manufacture in space, even the installation accuracy is difficult to guarantee.

Judging from the fact that the project name contains "Mars", the outside world can probably infer that the main goal of NanoStack is not to manufacture finished products directly in space. Although simple processing of some experimental modules is not ruled out, the focus is on processing space debris into raw materials and then transporting them to the vicinity of Mars for large-scale use.

Nowadays, space 3D printing is a hot area of ​​aerospace manufacturing research. If aluminum alloys, alloy steels, etc. can be reduced to powder in space and provided to 3D printers, complex new parts can be manufactured. However, it is difficult to deploy heavy metal crushers in space, so sending robots to cut scrapped spacecraft into small pieces, then transport and crush them may be a feasible solution.

However, this will bring new problems: In the borderless universe, what kind of assets are decommissioned spacecraft? It may be relatively easy to determine the "ownership" of a complete decommissioned spacecraft, but what about fragments of a certain size? It is not difficult to predict that as long as the on-orbit recycling and reuse technology is rolled out on a large scale, space junk will regain its value, and disputes between companies and countries will inevitably intensify. Therefore, in order to imagine turning space junk into treasure, we must not only overcome technical difficulties, but also cannot ignore legal issues.