On Tuesday, Russian billionaire Yuri Milner and famed astrophysics Stephen Hawking announced their $100 million plan to study Alpha Centauri, the closest star system to Earth (a mere 4.37 light-years away). The goal, among several different scientific investigations, is to basically find if aliens exist in that neck of the woods, or at the very least if there any planets or moons in the system capable of supporting life.
Called the Breakthrough Starshot, the project consists of sending ultra-lightweight spacecraft (dubbed “StarChips”) on their way to Alpha Centauri carried by a lightsail propelled by a 100 gigawatt light beam.
This is just the tip of the iceberg. The whole plan comes off as either mad genius, or just plain mad. The more you dig in, however, the more and more it seems like the plan by Milner and his crew might actually be feasible.
This is because the technology they are proposing isn’t actually far off the realm of possibility. It certainly stretches the imagination, but it doesn’t break it. The lightsail technology is already being tested by quite a few research groups, including one organized by Bill Nye. The rise in CubeSats as a size-efficient, inexpensive way of conducting space research has really shown how much can be gained by creating smaller, lighter spacecraft. Nanocrafts as pitched by Starshot is just a logical step in that direction.
Still, there are plenty of questions that remain about how the hell Milner, Hawking, and even Facebook founder Mark Zuckerberg (an investor) are going to pull this off. Here are the five biggest questions about the nanocraft technology and the light beam launch system — and some answers that might provide some insight.
Light Beams as a propulsion technology — please explain!
The Starshot plan to launch these nanocraft babies doesn’t use fuel and fire — it uses light and lasers. High-powered, focused lasers have been a source of intrigue for propulsion engineers for decades now, but it’s only recently that we can finally conceive of using such technology in several applications — including moving orbital debris out of the path of critical satellites. After all, light is an energy capable of exerting force on a system.
That’s the key word, though: conceive. We have yet to actually build a laser beam that can shoot another object off into space through sheer force of photons. Scientists are working on hybrid propulsion technologies that would use lasers in combination with more conventional methods, but not as the sole propellant.
You might be saying, “but then how is a solar sail supposed to work in space?” Well, the solar sail technology calls for using the photons produced by the sun’s rays to propel the sail (and its spacecraft) forward. The sail gets to space the ol’ fashioned way though: rockets.
Starshot claims that a light beamer — an array of lasers set up in a kilometer-wide scale — could potentially provide up to 100 gigawatts of beamed energy. We wouldn’t be using one ultra-big laser, but instead many smaller ones. Perhaps millions, or hundreds of millions.
Could that be enough force to get the nanocrafts out of the Earth’s atmosphere and gravitational pull? Maybe. Milner thinks Starshot stands a better chance by setting up the launch pad at a high-altitude environment, like the Atacama Desert. (Here are four suggestions we made today.) It’s also relatively dry enough to reduce the likelihood that water vapor could build up and create added weight on the spacecraft or hinder the laser’s force as it pushes the spacecraft up.
If all goes well, the probes would be on their way to Alpha Centauri at 100 million miles per hour, and reach the system within 20 years.
Lightsails are super thin and super delicate. How is this thing supposed to survive the launch? How is it supposed to survive the rocks and dust spinning around space for twenty years?
A lightsail is made of an ultra-thin “metamaterial (a catchall term that refers to experimental materials) designed to pick up oncoming photons from a light source and use them as a force of pressure that gets exerted on the sail itself. As a result, the sail is able to move forward and even accelerate to much higher speeds.
As I mentioned, lightsails aren’t new. Bill Nye and the Planetary Society have been working on a lightsail project that seeks to prove the viability of such a technology as a cost-effective spacecraft propulsion design. NASA is launching the Near-Earth Asteroid Scout (NEA Scout) in 2018 aboard Orion for the inaugural mission for the Space Launch System, which will make its way to a nearby asteroid via an expandable solar sail.
Both of those lightsails run into the same problem of colliding with interstellar dust and debris that could poke holes in the sail and derail the whole thing. That’s a pretty distinct possibility, but it’s limited by a couple of considerations.
First: space is big. There are plenty of bits of matter floating around, but it’s not like here on Earth where particles in the air are everywhere we turn. Objects in space are miles apart — as little as 10 to as much as millions, but miles nonetheless. The possibility of hitting something — while real — is still relatively remote.
Second, these sails were specifically designed to stay relatively solid in under damage. Take the NEA Scout, for instance. NASA has tested how well its lightsail can maintain structural integrity even if it’s hit with a few bits of space junk here and there. As long as there isn’t a catastrophic injury (like, say, an asteroid the size of Texas barreling into the spacecraft), the NEA Scout can still move forward and maneuver itself upon commands from NASA.
The Starshot nanocrafts have to contend with these problems as well. Their lightsails are predicted to stretch out to something on the scale of a few meters, so they’ll be pretty small. But they’ll be just a few hundred atoms thick, and have a mass of about one gram. They’re small enough to avoid nearly every kind of oncoming number of objects floating around space — but in the unlucky odds they get hit, the whole spacecraft will likely be destroyed. And we know next to nothing about the dust content in Alpha Centauri.
But there’s one big problem the nanocraft alone has to deal with — not falling apart during the light beam launch. The sail is expected to be hit by a beam that will amount to about 60 times the sunlight that hits Earth at any given moment. The sail needs to not just keep from melting, but also manage to get into space without getting ripped to shreds by the atmospheric forces. An estimated one part in 100,000 of the laser would be more than enough to evaporate the sail. This has never been done before. There’s no telling how much testing the Starshot project will need to conduct before getting this part right.
How does the StarChip work? What kinds of data is it supposed to collect?
The StarChips — being built on the scale of one gram and able to fit in the palm of one’s hand — will not be the state-of-the-art system that something like the Curiosity rover or the Kepler Space Telescope have been in helping us to study different worlds in space. They will be very basic. The goal is to stick four cameras (two-megapixels each) on the chip that will allow for some very elementary imaging of Alpha Centauri and the different planets and moons of the system.
That data would be transmitted back to Earth using a retractable meter-long antenna, or perhaps even using the lightsail to facilitate laser-based communications that could focus a signal back towards Earth.
That seems standard enough. What exactly are those images supposed to show us?
Therein lies another unknown. When astronomers assess the potential of other worlds to be habitable, they’re looking at a slew of different data, ranging from planet temperatures, composition, distance from their host star, signs of a present atmosphere — and so much more. A lot of this stuff is only measurable through different types of cameras that can see across the electromagnetic spectrum. The nanocrafts at this point would be running on cameras not too unlike what we use on our smartphones. That’s barely helpful for really understanding just whether a planet or moon could sustain any kind of life, or is already exhibiting signs of life.
Still, when you consider the goal is to send multiple small spacecraft out to a distant system that is multiple light-years away in under two decades, you have to cut costs somewhere.
Even if this thing survives the journey to Alpha Centauri, how is it supposed to live long enough to collect enough useful data?
Longevity is crucial to the Starshot project. The nanocraft need to stay powered for several decades to really tap into their full research potential. To this end, the Breakthrough initiative is proposing an onboard energy source based on plutonium-238 or Americium-241, weighing no more than 150 milligrams.
Basically, as the plutonium or Americium isotope decays, it would charge an ultra-capacitor that switches on the StarChip components necessary for snapping up pictures and transmitting them back to Earth. A thermoelectric energy source could also be implemented to take advantage of the nanocrafts frontal surface temperatures rising as it begins to approach the atmospheres of other worlds.
Photovoltaics — turning sunlight into energy — is also under consideration. One solar sail prototype that was tested by Japan about six years ago, IKAROS, painted the surface of its solar sail with a photovoltaics. This is impractical when nanocraft finally makes it out of solar system’s boundaries, but could be useful for that duration to save even more battery power.
The big question is whether you can keep such inexpensive materials viable over 20 to 50 years. In an ideal scenario, what is probably more likely to occur is that each nanocraft will only be expected to collect data for a relatively short time span — about a few months. If Milner and company are really set on mass producing these things, then they should have no problem sending a bunch in every direction to explore as much as they can about Alpha Centauri. Expecting each one to operate for years on end is pretty impractical if we can’t directly intervene and shift their movements in new directions.
Milner’s expressed goal is to make each nanocraft for about the cost that it takes to build an iPhone. Each SmartChip and lightsail combo should be no more than a few hundred dollars — and the goal is to keep adding better technologies as they become less and less expensive over the years.
In reality, the most expensive (and arguably least feasible) part of this project is the light beam. We’re talking about 100 gigawatts of power for two minutes in order to fire the damn thing. A single gigawatt can power 700,000 homes. So that’s enough for 70,000,000 homes.
That’s enough to power to keep multiple small countries going. That’s 100 times the amount produced by a typical nuclear power plant. It’s mind-boggling to even fathom how they’re going to gather this much energy into one place to launch a bunch of nanocrafts out into space.
The total cost of one lightbeam firing coud be, according to one commenter on the Breakthrough website, $70,000.
Yeah, we’ll see about that …