UNIVERSITY PARK, Pa. — The quest for low Earth orbit is entering a new chapter as various agencies and companies around the globe make ambitious strides to utilize very low Earth orbit (VLEO). This atmospheric region lies between 60 and 280 miles above the Earth’s surface. With a growing concern for orbital congestion and the inefficiencies of traditional satellite systems, the pursuit of VLEO technology is gaining momentum, signaling a paradigm shift in how we think about satellite operation and positioning.
In recent times, traditional low Earth orbits have become increasingly plagued by problems such as overcrowding, poor imaging resolution, and significant latency in data transmission. These concerns stem from the vast number of satellites currently in orbit, including extensive fleets launched by private companies like Starlink and OneWeb. Sven Bilén, a professor of engineering design, electrical engineering, and aerospace engineering at Penn State, highlights that the prevailing density of satellites presents serious risks. In this context, the allure of VLEO becomes evident, offering numerous advantages, particularly in imaging and communications.
Working against the constraints of orbital dynamics, Bilén notes that satellites situated at lower altitudes experience heightened imaging capabilities. By orbiting closer to Earth, these satellites can capture clearer, high-resolution images and facilitate quicker data transmissions. However, one of the fundamental challenges lies in maintaining a stable orbit at these altitudes where atmospheric drag becomes a critical factor, necessitating innovative propulsion solutions.
At the forefront of this endeavor is Bilén’s research team, which has recently secured a $1 million grant from the Defense Advanced Research Projects Agency (DARPA) through the Charge Harmony program. This collaborative effort, which also involves experts from the Georgia Institute of Technology, aims to develop advanced thruster systems capable of sustaining the delicate balance of VLEO. Each day brings the team closer to unveiling breakthroughs that enhance satellite viability in these challenging circumstances.
Despite the long-standing notion that VLEO technology was an intriguing concept, it has only recently gained traction among researchers and organizations. Bilén indicates that the urgent need to address the satellite traffic crisis in low Earth orbits has prompted a reevaluation of VLEO’s potential. The sector is alight with action as numerous companies recognize the lucrative opportunities embedded within the growing field of satellite platforms.
One of the most significant hurdles facing VLEO satellites is overcoming the physical realities of dragging through Earth’s atmosphere. At these elevations, satellite thrusters must contend with aerodynamic forces that push them downward, thus requiring constant thrust to remain stable. Traditional technologies quickly deplete fuel reserves in such environments. In response, researchers are exploring alternative propulsion systems that can harness the thin atmosphere itself as a potential fuel source, thus giving rise to air-breathing electric propulsion technologies.
This revolutionary method captures rarefied air and utilizes it as a propellant, providing a promising solution for VLEO satellite operation. However, power scarcity also poses barriers for low-orbit satellites; their thrusters demand significant energy, which has traditionally stemmed from solar panels. Unfortunately, the curvature of the Earth can obstruct sunlight, reducing solar efficiency for these satellites in VLEO. Addressing these dual challenges stands as the driving force of Bilén’s team’s research.
The aim is to create a self-neutralized air-breathing plasma thruster. This innovative propulsion system not only employs air gathered from the surrounding environment but also superheats it using microwave energy before expelling it through a nozzle to generate thrust. Unlike other thruster technologies that rely on complex electromagnetic devices for thrust generation, this new system boasts an inherent self-neutralization mechanism.
The most common electric propulsion system in use today is the Hall-effect thruster, which suffers limitations in oxygen-rich environments. The distinguishing feature of Bilén’s plasma thruster lies in its omission of a cathode. It leverages thermal heating to produce thrust while minimizing erosion and wear, a root cause of failure in conventional systems. Catered for rapid prototyping in extreme atmospheric conditions, this innovation promises to advance the operational boundaries of satellite technology.
Thus far, the research team has engaged in rigorous testing of their air-breathing microwave plasma thruster (AMPT), an entirely new category of propulsion that operates based on high-power microwave-generated thermal plasma. Early results have indicated that this new thruster design is more efficient than typical propulsion technologies, yielding an impressive thrust-to-power ratio—one that far surpasses existing solutions in electric propulsion.
As the team looks ahead, DARPA has requested a scaled-down version of their innovative thruster that will be compatible with smaller satellite designs. This component is integral to the overarching goal of integrating such thruster systems into future satellite platforms that would orbit lower than any operational satellite. This ambitious vision embodies a significant leap forward as they explore practical mission applications for the AMPT.
In summary, the rapid progression of VLEO technology, propelled by rigorous research and a willingness to adapt to the challenges of modern aerospace, signifies an exciting new era in satellite operations. The potential for establishing a more efficient and less congested orbital environment awaits as Bilén and his team work diligently toward realizing their transformative propulsion systems, paving the way for a new generation of powerful surveillance and communications satellites.
Through the advancements in VLEO technology, the prospect of exploring farther into the outer reaches of space while maintaining operational satellites within Earth’s atmosphere has never felt more tangible. This fusion of engineering prowess and the ambitious spirit of innovation may ultimately redefine our capabilities for satellite technology, leading us into an uncertain yet exhilarating future.
Subject of Research: Very Low Earth Orbit (VLEO) Satellite Technology
Article Title: Pioneering Very Low Earth Orbit Satellite Technology: A New Age for Satellite Operations
News Publication Date: October 2023
Web References: https://www.eecs.psu.edu
References: Science Magazine
Image Credits: Poornima Tomy/Penn State
Keywords
Very Low Earth Orbit, Satellite Technology, Aerospace Engineering, Propulsion Systems, DARPA, Air-Breathing Thrusters, Space Research, High-Resolution Imaging, Microwave Plasma Thrusters
