A group of engineers thinks it’s found a cheaper way to use high-altitude satellites to deliver global coverage.
In spite of what SpaceX and other companies suggest with projects like Starlink, you don’t need mega-constellations comprising thousands of satellites—and all the aggravations they cause—to provide global internet coverage to the world. We’ve known since the 1980s that if you’re okay with settling for a connection a notch below gamer-quality speeds (about a half-second lag), then continuous worldwide coverage is possible with a constellation of just four satellites placed at much higher altitudes.
But HughesNet and ViaSat, the world’s biggest satellite internet providers that operate at these orbits, don’t offer anything close to global coverage. Other satellite networks that provide remote sensing and navigation services also fall woefully short of that standard. What gives?
Unsurprisingly, the big obstacle is cost. Several factors work to degrade a satellite’s orbit. These include natural drag, perturbations in Earth’s gravity field, the interfering gravitational pull of the sun and the moon, and even pressure caused by solar radiation. To combat these problems, you need a huge amount of propellant on the satellite to consistently stabilize its orbit—an amount that usually doubles the satellite’s mass. Manufacturing, launch, and operational costs are just too high for the four-satellite trick.
A new study led by engineers at The Aerospace Corporation and published in Nature Communications proposes a counterintuitive approach that turns these degrading forces into ones that actually help keep these satellites in orbit. If it worked, it would mean just four satellites could provide continuous global coverage for a fraction of the cost.
Currently, the orbits for these satellites are elliptical, and forces from the sun and moon create instabilities which break the constellation apart over time. Patrick Reed at Cornell University and his colleagues wanted to make the orbits more circular, letting the satellites get by with fewer propulsive maneuvers and lower propellant requirements. And they wanted to do this in such a way that the satellites could still provide nearly global coverage.
The team ran simulations that looked at what types of orbital configurations could best turn degrading forces into ones that actually fostered a stable, circular orbit. Instances where, say, the sun’s gravity would normally break the constellation apart could now bind the constellation together. The simulations were for four-satellite constellations that would spend at least 6,000 days (16.4 years in orbit).
After analyzing the simulations using the Blue Waters supercomputer at the University of Illinois at Urbana-Champaign, the team found two models that could work. In one, the constellation completes an orbit in a 24-hour period, at an altitude of 22,000 miles, and achieves continuous coverage for about 86% of the globe. The other works on a 48-hour period at an altitude of 42,000 miles and covers 95% of the globe. Any areas that experienced outages would face no more than about 80 minutes of downtime a day.
By Spine Divo
In spite of what SpaceX and other companies suggest with projects like Starlink, you don’t need mega-constellations comprising thousands of satellites—and all the aggravations they cause—to provide global internet coverage to the world. We’ve known since the 1980s that if you’re okay with settling for a connection a notch below gamer-quality speeds (about a half-second lag), then continuous worldwide coverage is possible with a constellation of just four satellites placed at much higher altitudes.
But HughesNet and ViaSat, the world’s biggest satellite internet providers that operate at these orbits, don’t offer anything close to global coverage. Other satellite networks that provide remote sensing and navigation services also fall woefully short of that standard. What gives?
Unsurprisingly, the big obstacle is cost. Several factors work to degrade a satellite’s orbit. These include natural drag, perturbations in Earth’s gravity field, the interfering gravitational pull of the sun and the moon, and even pressure caused by solar radiation. To combat these problems, you need a huge amount of propellant on the satellite to consistently stabilize its orbit—an amount that usually doubles the satellite’s mass. Manufacturing, launch, and operational costs are just too high for the four-satellite trick.
A new study led by engineers at The Aerospace Corporation and published in Nature Communications proposes a counterintuitive approach that turns these degrading forces into ones that actually help keep these satellites in orbit. If it worked, it would mean just four satellites could provide continuous global coverage for a fraction of the cost.
Currently, the orbits for these satellites are elliptical, and forces from the sun and moon create instabilities which break the constellation apart over time. Patrick Reed at Cornell University and his colleagues wanted to make the orbits more circular, letting the satellites get by with fewer propulsive maneuvers and lower propellant requirements. And they wanted to do this in such a way that the satellites could still provide nearly global coverage.
The team ran simulations that looked at what types of orbital configurations could best turn degrading forces into ones that actually fostered a stable, circular orbit. Instances where, say, the sun’s gravity would normally break the constellation apart could now bind the constellation together. The simulations were for four-satellite constellations that would spend at least 6,000 days (16.4 years in orbit).
After analyzing the simulations using the Blue Waters supercomputer at the University of Illinois at Urbana-Champaign, the team found two models that could work. In one, the constellation completes an orbit in a 24-hour period, at an altitude of 22,000 miles, and achieves continuous coverage for about 86% of the globe. The other works on a 48-hour period at an altitude of 42,000 miles and covers 95% of the globe. Any areas that experienced outages would face no more than about 80 minutes of downtime a day.
By Spine Divo
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