Tractor Beam Technology: A Solution to Space Debris

Garbage in outer spacespace debris” (space junk) is one of the serious problems in space exploration. Even a piece of debris as small as 1mm can put a satellite out of action in the wrong place. It is estimated that there are more than 100 million pieces of debris that are 1 mm or larger in size, but as satellite constellations consisting of thousands or tens of thousands of satellites are already under construction, there is a possibility that the number will increase further in the future. there is.

Also, as the collision between “Iridium 33” and “Cosmos 2251” that occurred in 2009 tells us, there is also a problem that collisions between debris generate a large number of new debris. Therefore, various methods for debris collection are being researched.

Julian Hammerl of the University of Colorado Boulder et al.tractor beamI am researching how to collect space debris with ”. It sounds like science fiction, but in fact, “something like a tractor beam” is feasible. The key to this is electrostatic force, which applies the same principle that lifts hair when rubbed with a pad.

Specifically, an electron beam is irradiated to the debris from the debris collector. Then the debris will be negatively charged, and the debris collector will be positively charged. After that, all you have to do is wait for the charged debris collection machine and the debris to attract each other by electrostatic force and make contact.

However, things are not so simple in real space. In particular, in the case of low earth orbits orbiting near the earth, the earth’s atmosphere exists, albeit thin. The rarefied atmosphere of low earth orbit is full of free electrons and ions under the influence of ultraviolet rays and radiation. In such an environment full of charged particles, the electron beam irradiation from the debris collector may not work well.

[▲ Figure 2: ECLIPS is a special vacuum chamber that can reproduce the environment of low earth orbit (Credit: Nico Goda/CU Boulder)]

Hammerl et al.’s research team has a device to verify whether this problem can be overcome “ECLIPSE(Electrostatic Charging Laboratory for Interactions between Plasma and Spacecraft)”. ECLIPS, which literally translates as “electrostatic charging laboratory for interaction between plasma and spacecraft”, is basically a vacuum chamber that achieves a high vacuum inside. However, unlike other vacuum chambers, ECLIPS can reproduce the charged environment of low earth orbit. This allows us to investigate how the charged environment affects the tractor beam.

From simple cubes to wrinkled aluminum foil, the research team experimented with objects of various shapes.By irradiating an electron beam from a debris collection machine that approaches from 15m to 25m, even debris weighing up to 1 ton each can be collected by changing its trajectory over a period of 2 to 4 months.was shown. In addition, it was also shown that even debris that rotates at high speed and is dangerous to contact can be suppressed by irradiating it with an electron beam for a short period of time.

Other debris collection methods that have been proposed so far involve direct contact with the debris by complex control of the collection machine, or changing the trajectory by non-contact means with high energy costs such as high-power lasers. Methods are being studied, and it can be said that the recovery method using a tractor beam is superior to these in terms of control stability and energy cost. In addition, it can be said that it is superior to other methods in that it is possible to irradiate multiple electron beams at once from one debris collector and collect multiple debris at the same time.

On the other hand, there are still unresolved issues in debris collection using electron beams. What has been studied so far is the retrieval of debris in low earth orbit. Certainly, it is in low Earth orbit that we have to deal with the problem of space debris quickly, so it can be said that it is effective in the near future. However, in geostationary orbits, which have high utility value, and in higher-altitude orbits where many satellites will be launched in the future, the plasma contained in the solar wind is more dominant than the earth’s atmosphere. We have to take into account the completely different environment, and this is a topic for future research.

Tractor beams are still science fiction because no debris collector with electron beams has been launched so far. However, Hammerl and others are planning to launch a debris collection vessel within the next five to ten years, and a tractor beam may be realized in the not too distant future. Depending on the results of future experiments, tractor beams may become a basic means of debris collection.

Source

• Daniel Strain. “Space tractor beams may not be the stuff of sci-fi for long”. (University of Colorado Boulder)
• Hanspeter Schaub & Daniel F. Moorer Jr. “Geosynchronous Large Debris Reorbiter: Challenges and Prospects”. (The Journal of the Astronautical Sciences)
• Trevor Bennett & Hanspeter Schaub. “Contactless electrostatic detumbling of axi-symmetric GEO objects with nominal pushing or pulling”. (Advances in Space Research)
• Kieran Wilson, et.al. “Development and characterization of the ECLIPS space environments simulation facility”. (Acta Astronautica)
• Kaylee Champion & Hanspeter Schaub. “Electrostatic Potential Shielding in Representative Cislunar Regions”. (IEEE Transactions on Plasma Science)

Text: Riri Ayae