Space Debris Mitigation: Integration of Carbon Nanotube Cold Cathode Electron Emission with Electrodynamic Tether Payload for Rapid Deorbiting of Nanosatellites

As more spacecraft are launched into Low Earth Orbit (LEO), a concerning issue arises regarding the volume of spacecraft in LEO and how these objects remain in orbit after their decommissioning. In-operable space objects, consisting of defunct or inoperative satellite, spacecraft parts, and spent launch vehicles & rockets are human made objects often called “space junk” or “orbital space debris.” Objects such as Small Satellites (SmallSats), composed of CubeSats, NanoSats, and MircoSats, are in LEO are at risk of colliding with other satellites and space laboratories. With significant growth in the international space industry, many regions of LEO are at high levels of satellite density, which increases the probability of spacecraft collisions. These collisions can cause problems with critical infrastructure such as telecommunications, earth imaging, and defence systems. The expanding landscape of SmallSat research, spanning academia and industry, underscores a notable surge in the deployment of CubeSats. Characterized by their straightforward design, cost-effectiveness, and accessibility, CubeSats have become preferred choices for universities and companies as research platforms and for various industry applications. As this technology matures, a concerted effort is underway to pioneer novel deorbiting strategies, aiming for swifter and safer removal of these satellites from orbit. As space technology matures, the demand for innovative deorbiting strategies intensifies. This study addresses this need, specifically exploring integrated solutions like Carbon Nanotube (CNT) Cold Cathode and Electrodynamic Tether (EDT). These technologies aim to enhance the efficiency and sustainability of space debris mitigation, particularly for SmallSat missions. This study looks at developing, testing, and deploying a CNT Cold Cathode Plate connected to an Electrodynamic Tether, all as a 1U CubeSat Payload. This compact form factor, being 1 CubeSat Unit, sized at 10cmx10cmx10cm allows for a small, simple, and effective solution for deorbiting a standard 2U-8U CubeSat. The use of a CNT Cold Cathode allows for the payload to emit electrons, while the EDT is collecting the electrons emitted by the CNT Cold Cathode. The use of the EDT allows the electrons to be collected, charged, and emitted again by the CNT. This payload allows the electrons to experience a force acting on them by interacting with the earth’s gravitational field. This force is called, Lorentz force, and it is the propulsive force generated when the tether, carrying an electric current, moves through the Earth's magnetic field. The CNT Cold Cathode and ETD unit allows this payload to generate a thrust through the Lorentz force, and opposes the CubeSats orbital motion, resulting in a reduction of its orbital velocity. The deployed tether also increases the atmospheric drag that the entire CubeSat is experiencing, which leads to a faster decay of orbit, leading to the quicker de-orbit of the CubeSat. The relationship of Lorentz force and atmospheric drag allow the satellite to have a controlled and effective deorbit. The process of separating CNT Cathode consists of the daughterSat which contains the CNT Cold Cathode plate, is ejected from the motherSat. This process is triggered when two locking springs embedded into the daughterSat, decompress after being disconnected from the wire tension holding it to the motherSat. This allows for wave spring to also decompress and release the entire daughterSat unit. The motherSat contains the wave spring, which propels the daughterSat out of the motherSat. The motherSat also houses the burn wire system that holds the spring locks under tension till ejection, the tether storage cylinder, and an electronics board. Looking at the payload design and layout, from the bottom of the motherSat, it contains a PCB control board, with a controller chip, memory, and interface ports, followed by a disk style tether storage cylinder in the middle, with the wave spring sitting on the top of the storage. The burn wire system is located on small ridge that is like a fence around the daughterSat. This allows for the entire payload to be a cube and sit flush against the frame of any potential CubeSat that the payload may be integrated into. The daughterSat ejects when the burn wire daughter boards, which are connected to the control board which then sends a command that burns the wire which is tensioning the locking pins, and unlocks the entire payload. The result of this system allows a SmallSat to efficiently deorbit quicker, yielding in LEO to not be cluttered with space junk, risking damage to active spacecraft and space stations. This type of payload can be developed in budget & time efficient manner, allowing for this type of payload to be integrated into all sorts of academic and industry projects.

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