Vaporware to the Stars

Student-built cubesats, released from the international space station’s Kibo module in 2012, are 2,200 times more massive than the interstellar probes envisioned by Yuri Milner.

A Russian billionaire has decided to send a bunch of iPhones to Alpha Centauri.

If it all worked out — a cosmically big “if” that would occur decades and perhaps $10 billion from now — a rocket would deliver a “mother ship” carrying a thousand or so small probes to space. Once in orbit, the probes would unfold thin sails and then, propelled by powerful laser beams from Earth, set off one by one like a flock of migrating butterflies across the universe.

Neat, someone has been reading Charlie Stross’ Accelerando and wants to do that in real life. Only, not really: these aren’t von Neumann probes being sent into the universe to build things, just a fleet of really small Voyager dummy robots (a.k.a. droneses). So it’s a neat idea, but here are five huge problems with the concept.

  1. Initial power requirements. In order to power these tiny probes up to .2c, which is 1/5 the speed of light, which is around 134,123,326 miles per hour, the lasers that will accelerate each probe will have to be powered on a scale we have never before been able to imagine. As the New York Times put it, “That is about as much energy as it takes for a space shuttle to lift off, Dr. Loeb said, and about 100 times the output of a typical nuclear power plant.” And it would have to be transmitted in less than two minutes.
  2. The frickin’ laser beams. These “lasers” will apparently be ground-based, which means that it will most likely be an array of lasers all pointing to a single, iPhone-sized solar sail through the atmosphere: no mean feat at least a mile across, tuned such that each constituent beam stays perfectly in sync through an adaptive optics system that we have never scaled beyond 10 meters (which was at huge expense).
  3. Equipment durability. These tiny probes are supposed to withstand 60,000g during their acceleration phase. A typical space launch for humans maxes out around 3g for any extended period of time, and unmanned launches rarely exceed 6g because of the risk of damaging the electronics on board. Put simply, we have no possible way of building a tiny device that can withstand such forces without being shattered to pieces. Lastly, the solar sails must be able to withstand the vast amount of laser energy being pumped into them: 100GW on such a small scale would vaporize most materials that could conceivably make for a tiny sail; they basically need to invent a brand new type of mirror that doesn’t absorb any energy (which would be cool!).
  4. Electronics. The team envisions each of these thousand-ish probes being powered by a tiny piece of Americium, which is fine as far as it goes, but it is meant to last for decades in deep space, which is awash in high-energy radiation. Away from Earth’s magnetosphere, and we would assume the heliopause, you need a lot of shielding to keep your electronics safe.
  5. Phoning Home. According to the initial plan, “Those that survived would zip past the stars, making measurements and beaming pictures back to Earth.” So we are envisioning a simplified electronics package that weighs less than a gram, but which can somehow maintain focus and sensitivity to detect anything useful while zooming through a star system at 130 million miles per hour. So that’s… difficult. But somehow those probes are supposed to transit meaningful data back at us, here on Earth. Put simply: we have no idea if interstellar communication is even possible at a planetary scale, though we assume it is. But while that vast array of impossible lasers could conceivably be modulated to transmit data over light years, how on earth would a bunch of iPhones ever have the power to send a signal back to earth? And that’s assuming they somehow solve the bandwidth issue, namely: the further away from Earth you get, the more power you need to transmit the same amount of data — which means, at Alpha Centauri, you’d have a tiny amount of bandwidth available to send back any data. Again, this is assuming they can somehow use a the power generation of a planetary society to power their transmitters, which they won’t have.

When you add all of these together, you see a really cool premise that, unfortunately, relies on so much handwavium and advances in fundamental physics that I just don’t see it happening with this method. Apart from the extreme challenges

That being said, there are plenty of other, much more promising means of designing an interstellar probe, but they’re more conventional in size and make up. And even then, if you look at ideas coming out of the think tanks focused on interstellar travel (yes, they exist, and yes they are dream jobs), anything remotely feasible involves gigantic feats of mega-engineering like placing a receiver probe 51.1 billion miles away from the Sun so it can use gravity to “focus” weak signals — a super cool project, absolutely, but so complicated and so far beyond what we can actually do right now, with 21st century budgets and engineering, that it remains fantasy.

Does that mean this sort of research should go unfunded? Absolutely not! I want Yuri Milner and every other billionaire who wants to contribute to science to keep sending in research monies so we can learn these things and explore the universe around us. At the same time, it would be nice to see projects like this discussed with a bit less child-like credulity. The sort of challenges they are undertaking are so massive that to downplay them seems almost cruel: it is setting up the public and potential investors for massive disappointment when roadblocks are invariably hit.

But I mean, apart from that, sure let’s go for it.

joshua.foust
Joshua Foust is a writer and analyst who studies foreign policy.