Startup aims to beam sunlight from space to Earth using satellites

Illuminating the Dark: A Satellite-Based Solar Revolution?

The ambitious vision of an American startup, Reflect Orbital, promises to redefine our relationship with sunlight. Imagine a future where darkness is no longer an insurmountable obstacle, where solar energy can be harnessed even in the absence of direct daylight. This is the tantalizing prospect offered by their groundbreaking plan: to capture solar energy in space using an armada of satellites and beam it down to Earth for power generation.

The Earendil Initiative: A Glimpse into the Future

At the heart of this revolutionary endeavor is the Earendil-1, an 18-meter test satellite slated for launch in 2026. This pioneering mission is just the first step in Reflect Orbital's audacious plan to deploy a staggering 4,000 satellites into low Earth orbit by 2030. These celestial mirrors, each boasting a colossal 54-meter diameter, will orbit at an altitude of approximately 625 kilometers. Their primary function? To act as giant cosmic lenses, gathering the sun's abundant energy and directing it towards designated terrestrial solar power stations.

Harnessing Light Across Vast Distances

The physics of beaming sunlight from such a height present unique challenges. Orbiting at 625 km, the satellites won't always be directly overhead. Consequently, they will need to reflect sunlight at an angle, covering a ground area of roughly 800 kilometers. Even with sophisticated optical systems, the illuminated patch on Earth will be at least 7 kilometers in diameter. This limitation stems from the fundamental physics of focusing light; even a perfectly curved mirror or lens cannot condense sunlight into a pinpoint at such immense distances, given the sun's apparent half-degree width in the sky. For a single 54-meter satellite, the beamed light will be significantly dimmer than direct midday sun – about 15,000 times less intense – yet remarkably, it will still outshine the light of a full moon.

Testing the Waters: From Balloons to Orbit

Reflect Orbital has already conducted crucial preliminary tests. Ben Novak, the company's founder, recently shared insights from trials involving a reflector mounted on a balloon. In these experiments, a 2.5-meter square mirror successfully directed a beam of light onto solar panels and sensors. One notable test recorded an intensity of 516 watts per square meter when the balloon was just 242 meters away, a figure that is roughly half the intensity of midday sun (around 1,000 watts per square meter). While these terrestrial tests offer valuable data, scaling them to the orbital realm reveals significant hurdles. A reflector large enough to achieve comparable intensity from 800 kilometers away would need to span an impractical 42 square kilometers.

The Intensity Challenge and Orbital Mechanics

The startup's actual target intensity is a more modest 200 watts per square meter, achievable with simpler satellite designs and strategic positioning. However, achieving even this level requires a massive constellation. If one 54-meter satellite is 15,000 times weaker than direct sunlight, generating 20% of that intensity would necessitate approximately 3,000 such satellites working in concert. This brings us to another significant operational challenge: orbital velocity. Satellites at 625 km speed along at roughly 7.5 km per second. This means each satellite can illuminate a specific target region for a mere 3.5 minutes before moving beyond the 1,000 km range. Consequently, 3,000 satellites would only provide the desired light intensity for a fleeting few minutes. To sustain illumination for a full hour, the number of satellites would need to multiply exponentially, potentially reaching thousands more.

A Sky Full of Stars, or Something More?

Novak's vision extends to a staggering 250,000 satellites in orbits above 600 kilometers, a figure that dwarfs the current count of both operational and defunct spacecraft. Given their altitude, these satellites would primarily be able to illuminate Earth's surface during twilight and dawn, precisely when their mirrors can best capture direct sunlight. To maximize their operational window, Reflect Orbital intends to position their constellation on sun-synchronous orbits, essentially skirting the terminator – the line between day and night – ensuring they perpetually remain in sunlight. However, this ambitious plan is not without its critics. Prominent astronomers, including Michael Brown from Monash University and Matthew Kenworthy from Leiden University, have raised serious concerns. They argue that this approach is not only impractical for efficient solar energy collection but also poses a severe threat of widespread light pollution, potentially blinding the very scientific endeavors that seek to understand our universe.

The Double-Edged Sword of Orbital Illumination

The potential for astronomical interference is indeed alarming. For any astronomer peering through a telescope, the reflective surface of these satellites could appear as bright as the sun itself, risking irreversible eye damage. While Reflect Orbital aims to illuminate specific locations, the powerful beams will sweep across the entire planet as the satellites move between targets. The night sky could be transformed into a canvas of pulsating flashes, brighter than the moon itself, fundamentally altering our ancient and profound connection with the cosmos.