Shields Up, Mr. Sulu! Cruising At 20% Speed Of Light Has Some Inherent Risks

Back in April, Russian billionaire Yuri Milner and famed cosmologist Stephen Hawking unveiled Project Starshot. As the latest venture by Breakthrough Initiatives, Starshot was conceived with the aims of sending a tiny spacecraft to the neighboring star system Alpha Centauri in the coming decades.

Relying on a sail that would be driven up to relativistic speeds by lasers, this craft would theoretically be capable of making the journey is just 20 years. Naturally, this project has attracted its fair share of detractors. While the idea of sending a star ship to another star system in our lifetime is certainly appealing, it presents numerous challenges.

Not one to shy away from any potential problems, Breakthrough Starshot has begun funding the necessary research to make sure that their concept will work. The results of their first research effort appeared recently in arXiv, in a study titled “The interaction of relativistic spacecrafts with the interstellar medium“.

Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity's first interstellar voyage. Credit: breakthroughinitiatives.org
Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity’s first interstellar voyage. Credit: breakthroughinitiatives.org

Assessing the risks of interstellar travel, this paper addresses the greatest threat where relativistic speed is concerned: catastrophic collisions! To put it mildly, space is not exactly an empty medium (despite what the name might suggest). In truth, there are a lot of things out there on the “stellar highway” that can cause a fatal crash.

For instance, within interstellar space, there are clouds of dust particles and even stray atoms of gas that are the result of stellar formations and other processes. Any spacecraft traveling at 20% the speed of light (0.2 c) could easily be damaged or destroyed if it suffered a collision with even the tiniest of this particulate matter.

The research team was led by Dr. Chi Thiem Hoang, a postdoctoral fellow at Canadian Institute for Theoretical Astrophysics (CITA) at the University of Toronto. As Dr. Hoang told Universe Today via email:

“To evaluate the risks, we calculated the energy that each interstellar atom or dust grain transfers to the ship along the path of the projectile in the ship. This acquired energy rapidly heats a spot on the ship surface to high temperature, resulting in damage by reducing the material strength, melting or evaporation.”

The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA
The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA

In short, the danger of a collision comes not from the physical impact, but from the energy that is generated due to the fact that the spaceship is traveling so fast. However, what they found was that while collisions with tiny dust grains are very likely, collisions with heavier atoms that can do the most damage would be more rare.

Nevertheless, the damage from so many tiny collisions will certainly add up over time. And it would only take one collision with a larger particle to end the mission. As Dr. Hoang explained:

“We found that the ship would be damaged by collision with heavy atoms and dust grains in the interstellar medium. Heavy atoms, mostly iron can damage the surface to a depth of 0.1mm. More importantly, the surface of the ship is eroded gradually by dust grains, to a depth of about 1mm. The ship may be completely destroyed if encountering a very big dust grain larger than 15micron, although it is extremely rare.”

In terms of damage, what they determined was that each iron atom can produce a damage track of 5 nanometer across, whereas a typical dust silicate grain measuring just 0.1. micron across (and containing about one billion iron atoms) could produce a large crater on the ship’s surface.

A phased laser array, perhaps in the high desert of Chile, propels sails on their journey. Credit: Breakthrough Initiatives.
A phased laser array, perhaps in the high desert of Chile, propels sails on their journey. Credit: Breakthrough Initiatives.

Over time, the cumulative effect of this damage would pose a major risk for the ship’s survival. As a result, Dr. Hoang and his team recommended that some shielding would need to be mounted on the ship, and that it wouldn’t hurt to “clear the road” a little as well.

“We recommended to protect the ship by putting a shield of about 1 mm thickness made of strong, high melting temperature material like graphite.” he said. “We also suggested to destroy interstellar dust by using part of energy from laser sources.”

Starshot is the latest in a long line of directed energy concepts that owe their existence to Professor Phillip Lubin. A professor from the University of California, Santa Barbara (UCSB), Lubin is also the mind behind the Directed Energy Propulsion for Interstellar Exploraiton (DEEP-IN) project and the Directed Energy Interstellar Study.

These projects, which are being funded by NASA, seek to harness the technology behind directed-energy propulsion to rapidly send missions to Mars and other locations within the Solar System in the future. Long-term applications include interstellar missions, similar to Starshot.

Artist's impression of the Earth-like exoplanet discovered orbiting Alpha Centauri B iby the European Southern Observatory on October 17, 2012. Credit: ESO
Artist’s impression of the Earth-like exoplanet discovered orbiting Alpha Centauri B iby the European Southern Observatory on October 17, 2012. Credit: ES

Other interesting projects overseen by Lubin and the UCSB lab include the Directed Energy System for Targeting of Asteroids and exploRation (DE-STAR). This system calls for the use of lasers to deflect asteroids, comets, and other near-Earth objects (NEO) that pose a credible risk of impact.

In all cases, directed-energy technology is being proposed as the solution to the problems posed by space travel. In the case of Starshot, these include (but are not limited to) inefficiency, mass, and/or the limited speeds of conventional rockets and ion engines.

As Professor Lubin told Universe Today via email, he and his colleagues are in general agreement with the research team and their findings:

“The recent paper by Hoang et al revisits the section (7) in our paper “A Roadmap to Interstellar Flight” that discusses our calculation for the effects of the ISM on the wafer scale spacecraft. Their general  conclusion on the effects of the gas and dust collisions were essentially the same as ours, namely that it is an issue, but not a fatal one, if one uses the spacecraft geometry we recommend in our paper, namely orient the spacecraft edge on (like a Frisbee in flight) and then use an edge coating (we use [Beryllium], they use graphite).”

“As for the sail interactions with the ISM we recommend either rotating the sail so it is edge on (lower cross section) or ejecting the sail after the initial few minutes of acceleration as it is no longer needed for acceleration. However. as we desire to use the sail as a reflector for the laser communications we prefer to keep it, though a secondary reflector could be deployed later in the mission if necessary. These detailed questions will be part of the evolving design phase.”

Indeed, there are many safety hazards that have to be accounted for before any mission to interstellar space could be mounted. But as this recent study has shown – with which Professor Lubin agrees – they are not insurmountable, and a mission to Alpha Centauri (or, fingers crossed, Proxima Centauri!) could be performed if the proper precautions are taken.

Who knew the future of space travel would be every bit as cool as we’ve been led to believe – complete with lasers and shielding?

And be sure to enjoy this video from NASA 360, addressing directed-energy propulsion:

Further Reading: arXiv

Finding Aliens May Be Even Easier Than Previously Thought

Finding examples of intelligent life other than our own in the Universe is hard work. Between spending decades listening to space for signs of radio traffic – which is what the good people at the SETI Institute have been doing – and waiting for the day when it is possible to send spacecraft to neighboring star systems, there simply haven’t been a lot of options for finding extra-terrestrials.

But in recent years, efforts have begun to simplify the search for intelligent life. Thanks to the efforts of groups like the Breakthrough Foundation, it may be possible in the coming years to send “nanoscraft” on interstellar voyages using laser-driven propulsion. But just as significant is the fact that developments like these may also make it easier for us to detect extra-terrestrials that are trying to find us.

Not long ago, Breakthrough Initiatives made headlines when they announced that luminaries like Stephen Hawking and Mark Zuckerberg were backing their plan to send a tiny spacecraft to Alpha Centauri. Known as Breakthrough Starshot, this plan involved a refrigerator-sized magnet being towed by a laser sail, which would be pushed by a ground-based laser array to speeds fast enough to reach Alpha Centauri in about 20 years.

In addition to offering a possible interstellar space mission that could reach another star in our lifetime, projects like this have the added benefit of letting us broadcast our presence to the rest of the Universe. Such is the argument put forward by Philip Lubin, a professor at the University of California, Santa Barbara, and the brains behind Starshot.

In a paper titled “The Search for Directed Intelligence” – which appeared recently in arXiv and will be published soon in REACH – Reviews in Human Space Exploration – Lubin explains how systems that are becoming technologically feasible on Earth could allow us to search for similar technology being used elsewhere. In this case, by alien civilizations. As Lubin shared with Universe Today via email:

“In our SETI paper we examine the implications of a civilization having directed energy systems like we are proposing for both our NASA and Starshot programs. In this sense the NASA (DE-STAR) and Starshot arrays represent what other civilizations may possess. In another way, the receive mode (Phased Array Telescope) may be useful to search and study nearby exoplanets.”

DE-STAR, or the Directed Energy System for Targeting of Asteroids and exploRation, is another project being developed by scientists at UCSB. This proposed system will use lasers to target and deflect asteroids, comets, and other Near-Earth Objects (NEOs). Along with the Directed Energy Propulsion for Interstellar Exploration (DEEP-IN), a NASA-backed UCSB project that is based on Lubin’s directed-energy concept, they represent some of the most ambitious directed-energy concepts currently being pursued.

Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity's first interstellar voyage. Credit: breakthroughinitiatives.org
Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity’s first interstellar voyage. Credit: breakthroughinitiatives.org

Using these as a template, Lubin believes that other species in the Universe could be using this same kind of directed energy (DE) systems for the same purposes – i.e. propulsion, planetary defense, scanning, power beaming, and communications. And by using a rather modest search strategy, he and colleagues propose observing nearby star and planetary systems to see if there are any signs of civilizations that possess this technology.

This could take the form of “spill-over”, where surveys are able to detect errant flashes of energy. Or they could be from an actual beacon, assuming the extra-terrestrials us DE to communicate. As is stated in the paper authored by Lubin and his colleagues:

“There are a number of reasons a civilization would use directed energy systems of the type discussed here. If other civilizations have an environment like we do they might use DE system for applications such as propulsion, planetary defense against “debris” such as asteroids and comets, illumination or scanning systems to survey their local environment, power beaming across large distances among many others. Surveys that are sensitive to these “utilitarian” applications are a natural byproduct of the “spill over” of these uses, though a systematic beacon would be much easier to detect.”

According to Lubin, this represents a major departure from what projects like SETI have been doing during the last few decades. These efforts, which can be classified as “passive” were understandable in the past, owing to our limited means and the challenges in sending out messages ourselves. For one, the distances involved in interstellar communication are incredibly vast.

The Very Large Telescoping Interferometer firing it's adaptive optics laser. Credit: ESO/G. Hüdepohl
Directed-energy technology, such as the kind behind the Very Large Telescoping Interferometer, could be used by ET for communications. Credit: ESO/G. Hüdepohl

Even using DE, which moves at the speed of light, it would still take a message over 4 years to reach the nearest star, 1000 years to reach the Kepler planets, and 2 million years to the nearest galaxy (Andromeda). So aside from the nearest stars, these time scales are far beyond a human lifetime; and by the time the message arrived, far better means of communication would have evolved.

Second,  there is also the issue of the targets being in motion over the vast timescales involved. All stars have a transverse velocity relative to our line of sight, which means that any star system or planet targeted with a burst of laser communication would have moved by the time the beam arrived. So by adopting a pro-active approach, which involves looking for specific kinds of behavior, we could bolster our efforts to find intelligent life on distant exoplanets.

But of course, there are still many challenges that need to be overcome, not the least of which are technical. But more than that, there is also the fact that what we are looking for may not exist. As Lubin and his colleagues state in one section of the paper: “What is an assumption, of course, is that electromagnetic communications has any relevance on times scales that are millions of years and in particular that electromagnetic communications (which includes beacons) should have anything to do with wavelengths near human vision.”

In other words, assuming that aliens are using technology similar to our own is potentially anthropocentric. However, when it comes to space exploration and finding other intelligent species, we have to work with what we have and what we know. And as it stands, humanity is the only example of a space-faring civilization known to us. As such, we can hardly be faulted for projecting ourselves out there.

Here’s hoping ET is out there, and relies on energy beaming to get things done. And, fingers crossed, here’s hoping they aren’t too shy about being noticed!

Further Reading: arXiv

Can We Really Get to Alpha Centauri?

In a previous episode, I said that traveling within the Solar System is hard enough, traveling to another star system in our lifetime is downright impossible. Many of you said it was the most depressing episode I’ve ever done .

The distance to Pluto is, on average, about 40 astronomical units. That’s 40 times the distance from the Sun to the Earth. And New Horizons, the fastest spacecraft traveling in the Solar System took about 10 years to make the journey.

The distance to Alpha Centauri is about 277,000 astronomical units away (or 4.4 light-years). That’s about 7,000 times further than Pluto. New Horizons could make the journey, if you were willing to wait about 70,000 years. That’s about twice as long as you’d be willing to wait for Half Life 3.

But my video clearly made an impact on a plucky team of rocket scientists, entrepreneurs and physicists, who have no room in their personal dictionary for the word “impossible”. Challenge accepted, they said to themselves.

In early April, 2016, just 8 months after I said it was probably never going to happen, the billionaire Yuri Milner and famed physicist Stephen Hawking announced a strategy to send a spacecraft to another star within our lifetime. In your face Fraser, they said… in your face.

Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity's first interstellar voyage. Credit: breakthroughinitiatives.org
Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity’s first interstellar voyage. Credit: breakthroughinitiatives.org

The project will be called Breakthrough Starshot, and it’s led by Pete Worden, the former director of NASA’s AMES Research Center – the people working on a warp drive.

The team announced that they’re spending $100 million to investigate the technology it’ll take to send a spacecraft to Alpha Centauri, making the trip in just 20 years. And by doing so, they might just revolutionize the way spacecraft travel around our own Solar System.

So, what’s the plan? According to their announcement, the team is planning to create teeny tiny lightsail spacecraft, and accelerate them to 20% the speed of light using lasers. Yes, everything’s made better with lasers .

We’ve talked about solar sails in the past, but the gist is that photons of light can impart momentum when they bounce off something. It’s not very much, but if you add a tremendous amount of photons, the impact can be significant. And because those photons are going the speed of light, the maximum speed for the spacecraft, in theory, is just shy of the speed of light (thanks relativity).

You can get those photons from the Sun, but you can also get them from a directed laser beam, designed to fill the sails with photons, without actually melting the spacecraft.

In the past, engineers have talked about solar sails that might be thousands of kilometers across, made of gossamer sheets of reflective fabric. Got that massive, complicated sail in your mind?

Now think smaller. The Starshot spacecraft will measure just a few meters across, with a thickness of just a few atoms. The sail would then pull a microscopic payload of instruments. A tiny chip, capable of gathering data and transmitting information – these are called Starchips. Not even enough room for water bear crew quarters.

A phased laser array, perhaps in the high desert of Chile, propels sails on their journey. Credit: Breakthrough Initiatives.
A phased laser array, perhaps in the high desert of Chile, propels sails on their journey. Credit: Breakthrough Initiatives.

With such a low mass, a powerful laser should be able to accelerate them to 20% the speed of light, almost instantly, making a trip to Alpha Centauri only take about 20 years.

Since each Starshot might only cost a few dollars to make, the company could manufacture thousands and thousands, place them into orbit, and then start bugzapping them off to different stars.

There are, of course, some massive engineering hurdles to overcome.

The first is the density of the interstellar medium. Although it’s almost completely empty in between the stars, there are the occasional dust particles. Normally harmless, the Starshots would be smashing into them at 20% the speed of light, which would be catastrophic.

The second problem is that this is a one-way trip. Once it’s going 20% the speed of light, there’s no way to slow the spacecraft down again (unless the Alpha Centaurans have a braking system in place). Just imagine the motion blur and targeting problems when you’re trying to take photos at relativistic speeds.

The third problem, and this is a big one, is that the miniaturization of the spacecraft means that you can’t have a big transmitter. Communicating across the light years takes a LOT of power. Maybe they’ll connect up into some kind of array and share the power requirement, or use lasers to communicate back. Maybe they’ll relay the data back like a Voltron daisy chain.

Even though the idea of traveling to another star might seem overly ambitious today, this technology actually makes a lot of sense for exploration in our own Solar System. We could bugzap little spacecraft to Venus, Mars, the outer planets and their moons – even deep into the Kuiper Belt and the totally unexplored Oort cloud. We could have this whole Solar System on exploration lockdown in just a few decades.

Even if a mission to Alpha Centauri is currently science fiction, this miniaturization is going to be the way we learn more about the Solar System we live in. Let’s get going!

Is Alpha Centauri The Best Place To Look For Aliens?

For generations, human beings have fantasized about the possibility of finding extra-terrestrial life. And with our ongoing research efforts to discover new and exciting extrasolar planets (aka. exoplanets) in distant star systems, the possibility of actually visiting one of these worlds has received a real shot in the arm. Unfortunately, given the astronomical distances involved, not to mention the cost of mounting an expedition, doing so presents numerous significant challenges.

However, Russian billionaire Yuri Milner and the Breakthrough Foundation – an international organization committed to exploration and scientific research –  is determined to mount an interstellar mission to Alpha Centauri, our closest stellar neighbor, in the coming years. With the backing of such big name sponsors as Mark Zuckerberg and Stephen Hawking, his latest initiative (named “Project Starshot“) aims to send a tiny spacecraft to the Alpha Centauri system to search for planets and signs of life.

Continue reading “Is Alpha Centauri The Best Place To Look For Aliens?”