Currently, most orbital spacecraft generate thrust by ejecting propellant. The need for propellant has hampered efforts to remove debris from Earth’s orbit – a problem which has resulted in an orbit increasingly cluttered by defunct satellites and the remnants of old space missions. To prevent active satellites from colliding with debris, researchers are developing a new generation of spacecraft – Hyper Transfer Vehicles (or HTVs) – designed to remove orbital debris. These HTVs need to be agile enough to grab debris, drag it down to the Earth’s atmosphere to safely burn up, then return to the higher orbit to repeat the operation. Read More
However, current spacecraft, called orbit transfer vehicles or OTVs, rely on propellants to generate thrust, presenting significant challenges. Propellant-based OTVs are not only inefficient, but they also require frequent refueling missions from Earth, making it impossible to develop reusable spacecraft capable of performing this debris-removal task at scale.
Enter Dennis Lee, Vortex Space Systems, who envisions using a revolutionary approach to a fundamental principle in physics: the conservation of angular momentum (or CAM).
The CAM principle applies to all rotating objects; from a spinning ice skater increasing their rotation by pulling in their arms, to large-scale natural phenomena such as hurricanes on Earth or the gas giant atmospheres of Jupiter and Saturn. In essence, when an object’s angular momentum is altered, a reaction torque force is imparted to the system that affects its environment and changes its linear and rotational motion.
According to Lee, the reaction forces imparted through CAM will greatly exceed electric Hall propulsion thrusters. He describes how a rotating working fluid mass on board a spacecraft could be exploited to impart linear forces in any direction required. If implemented practically, this could allow HTVs to make rapid, controlled and unlimited adjustments to their orientations and orbit trajectories – without the need for fuel. Lee has named this concept the ‘CAM drive’.
And, the benefits of this approach are significant. Lee calculates that the reusability and flexibility offered by the CAM drive could slash the cost of debris removal from $7,500 per kilogram down to just $200.
While still in the early stages of development, Lee’s findings are a promising first step toward a new generation of HTVs – one that would use high cadence operations to declutter Earth’s orbits for many years to come.
As research progresses, Lee hopes that his work will inspire researchers to consider new techniques for CAM analysis in studying nature and generating propellant-free thrust – a glimpse into the future of space travel, where propellant-free propulsion unlocks new possibilities for both orbit operations and the broader new space economy.
