Cracker-Sized Satellite Sends First Message Home

Credits: and ESO/M. Kornmesser
Credits: and ESO/M. Kornmesser
Sprite is the world’s smallest space probe (3.5 x 3.5 cm), about the size of a Saltine cracker. At just four grams, it is lighter than a quarter. It has its own solar panel, communication capabilities and sensors. Sprite is built using the same devices and processes used in the consumer electronics industry, its small size made possible thanks to rapid advances made in the semiconductor industry. Most of the features of a traditional spacecraft can be integrated onto a chip-scale device. Sprite is the brainchild of Zac Manchester, whose Kickstarter “KickSat” campaign at Cornell University raised the first funds to develop the concept.

In 2015, Russian billionaire Yuri Milner established Breakthrough Initiatives, a non-profit organization dedicated to enhancing the search for extraterrestrial intelligence (SETI). On the board sit Yuri Milner, Stephen Hawking and Mark Zuckerberg. In April of the following year, Breakthrough Initiatives announced the creation of Breakthrough Starshot, a program to create a lightsail-driven “wafercraft” that would make the journey to the nearest star system–Alpha Centauri–within our lifetime.

The Sprite would be used as the prototype of the eventual Breakthrough Starshot lightsail-driven “wafercraft.” Six Sprites were launched on June 23. Currently, they don’t fly on their own and so are piggybacking on two satellites. Unfortunately all of them, except one, have remained silent so far. The only one researchers have heard from is broadcasting a standard “I am here” radio signal.

The purpose of ever smaller space probes are to allow us to visit other “nearby” planets. The Kepler Space Telescope has identified 2,337 planets, with about 50 in the “goldilocks zone”–not too hot or cold, too big or too small. They’re Earth’s size and shape and orbit around the warm glow of stars like our own sun, perhaps hosting life. The closest planet to us is Proxima b, orbiting Proxima Centauri, one of three stars in the Alpha Centauri system, the nearest star system to our sun. Like Earth, Proxima b is within the so-called “habitable zone.”

But there is a problem: To reach Alpha Centauri (which is “only” four light years away) in a huge spacecraft carrying humans onboard would take tens of thousands of years to reach. That’s where a fleet of tiny, light and small-enough Sprite-like probes come into play. Estimates are that it might take a fleet of such Sprites about “only” 20 years to get to Proxima b, then another four years to beam data and pictures back to Earth.

For the Sprite to be able to accomplish this feat, it must get even smaller and lighter. It needs to weigh less than one gram, be fitted with a sail (because carrying its own fuel would add too much weight) and be equipped with an on-board small optical laser to communicate text and pictures via light, not radio, signals. For propulsion, the current idea is to equip it with sails that would be pushed through space by a laser (or an array of lasers). Directed from Earth, the laser would propel the spacecraft to speeds at 20 percent of the speed of light (more than 100 million miles an hour).

The goal is that these tiny Breakthrough Starshot spacecraft would reach Proxima b in our lifetime and send more than an “I am here” signal, like Sprite is doing today. Instead, they would also send pictures, giving us our first incredible view of a habitable Earth-like planet. And when we do find one (whether Proxima b or another), what do we do? Should we just observe? An Open Letter (signed by Yuri Milner and 31 other scientists, professors, writers, astronauts, soprano, …) asks the following questions: Do we try to make contact with advanced civilizations? Who decides? Individuals, institutions, corporations, or states? Or can we as species–as a planet–think together? Deep questions to ponder.