Interstellar travel: reaching out to other worlds

INN International Editor Clifford Holt spoke to Breakthrough Starshot Executive Director Dr Pete Worden about his vision for interstellar travel and the ambitions of the Breakthrough Starshot initiative.

Interstellar travel has been the dream of many for perhaps as long as humans have looked up at the night sky. This dream became even more intriguing when, thanks to NASA’s Kepler mission, it was revealed that the sky is filled with billions of hidden planets – more planets even than stars – and that many of these planets may lie within the ‘habitable zone’ at just the right distance from their host star to be able to harbour the ingredients of life, at least as we currently understand them. The dream of interstellar travel thus became not only about the journey, but also about what might be found at the end of it.

The closest star system to Earth’s Solar System, Alpha Centauri, is 4.37 light years away. As such, it would take tens or hundreds of millennia to reach it using current rocket propulsion technology. Yet, despite this seemingly insurmountable challenge, work is underway to reach this system and, hopefully, send images of the recently-discovered planet Proxima b back to Earth.

This is the aim of the Breakthrough Starshot initiative, which was established by Yuri and Julia Milner, was supported by Professor Stephen Hawking, and continues to count Facebook’s Mark Zuckerberg as a member of its Board. Breakthrough Starshot intends to use a ground-based laser to propel ultra-light nanocrafts – miniature space probes attached to lightsails – to speeds of up to 100 million miles an hour, allowing them to flyby Alpha Centauri in just over 20 years from launch.

Dr Pete Worden, former director of NASA’s Ames Research Center and now Breakthrough Starshot’s Executive Director, spoke to International Editor Clifford Holt about his vision for interstellar travel, the ambitions of the initiative, and its development thus far.

Why did you become involved with the Breakthrough Starshot initiative? What stage has the project reached?

When I was five years old, my mother gave me two books. One was about the planets in our Solar System, and I was expecting to read about the people who lived on these other worlds. Of course, when I discovered that no such civilisations existed, I was quite disappointed. The second book was about the stars, at the end of which the author noted that there may be planets like the Earth orbiting other stars, and that was exciting! Since that time, interstellar travel has been an abiding interest of mine, and one which later manifested itself as an ambition to achieve.

Later in my career, I became the Director of NASA Ames, which was a great experience as the Ames Research Center is really at the heart of NASA’s activities when it comes to astrobiology. During my time there, I fought to keep the Kepler mission going by leveraging funding from the three partners. And in the end, this mission demonstrated that essentially every star in the Universe is orbited by planets and, moreover, that perhaps a quarter of these stars have Earth-sized planets which are potentially habitable.

I first began to discuss the Breakthrough Starshot initiative with Yuri Milner in 2014, and he persuaded me to come on board. He knew that I had been involved in the 100 Year Starship project while at NASA, and he told me that he could help to build my starship.

Of course, the first question we came up against was how to achieve it. My initial focus was on antimatter (which I had some military experience with) and whether we could make it in small quantities. We therefore established a study group to explore that further. However, we were informed by mathematical and theoretical physicist Professor Edward Witten at the Institute for Advanced Study that our calculations were inaccurate.

We therefore started looking for other methods, one of which was a concept around laser-driven lightsails which was originally developed by physicist Robert Forward in the 1970s.

At the time it was conceived by Forward, it seemed infeasible. However, since then we have seen significant developments in laser technologies – in line with Moore’s Law we have witnessed increasing power and decreasing costs. This, coupled with how we have similarly seen Moore’s Law applied to satellite technologies and their miniaturisation, has resulted in the potential to now create spacecraft small enough to be propelled by the laser conceived by Forward.

The key work in advancing this concept was done by Professor Philip Lubin at the University of California, Santa Barbara. We took it to Harvard’s Professor Avi Loeb who was heading up our team, and he agreed on its feasibility, which meant we were then able to take the idea to our sponsors. We then conducted a three-month study, and it was at this point that we involved Professor Stephen Hawking and a few other notable experts, who all agreed that while it may take a few decades for the technology to be developed to the required stage, the concept will work.

In April 2016, Milner arranged for Hawking to make his last trip to the United States and we announced the Starshot Initiative from the top of the One World Trade Center, with Milner committing $100m.

There are three main technological challenges that we now need to overcome. The first is that we need a laser with a power output in excess of 100 gigawatts. To achieve that, we will need to employ a square-kilometre array of lasers. While at the moment it would simply be too expensive to build this array with current technologies, the trends we are seeing in terms of cost, size, and power should mean that we will be able to achieve this in the future. Indeed, there are a number of very feasible approaches and we have recently entered into the second phase of our activities here, where we will develop some of the key technologies in the lab.

The second challenge is the development of the lightsail. This is essentially a materials challenge, in that it has to be both incredibly light and incredibly robust. We have therefore enlisted the help of Professor Harry Atwater at Caltech, and we have now almost completed the first phase of our work on the lightsail. Phase two will be to begin its construction and development in the lab.

The third challenge is perhaps the biggest, and it relates to how we can communicate back to the Earth from a number of light years away. There are a number of potential ways that this could be achieved, for instance by including a small laser on the nanocraft and then repurposing the lightsail as a focusing device. Theory says that this could enable us to send a signal back to the Earth from the Alpha Centauri star system, but we would need a very large optical system in the range of 50-100m to detect hundreds of bits per second. We have just begun phase one of our work in this area, and that is being led by Professor Philip Mauskopf at Arizona State University, and things are going very well.

We have also realised that we need to do two other things. One is the development of a systems model, which is being handled by Dr Kevin Parkin (who worked for me at NASA Ames). He has created a great model that helps guide our efforts.

The other is that we need to conduct an integrated experiment on lightsails and lasers. We have therefore recently begun to do some analysis and hope to build a CubeSat class mission.

One of the questions asked by the Breakthrough Initiatives Foundation is: ‘When we find the nearest exo-Earth, should we send a probe? Do we try to make contact with advanced civilisations? Who decides? Individuals, institutions, corporations, or states? Or can we as a species – as a planet – think together?’ Taking into account the pollical climate in many countries, what do you feel is the most likely answer to this?

Our foundation, of course, is committed to open scientific discourse, and the discovery would undoubtedly be controversial. As Carl Sagan said, extraordinary claims require extraordinary evidence, and the scientific process of refereed papers is superb. As such, we believe that if there were a putative detection of a signal, then the first thing that would happen would be a validation of the signal on multiple instruments by the SETI community.

Indeed, one of the biggest achievements to come from the Breakthrough Listen programme was a revitalisation of the international search for extra-terrestrial intelligence (SETI) community with numerous programmes now being set up in this area around the world by both governments and private enterprises. The Chinese, for example, have a major new study programme for their new 500-metre radio telescope, and we have signed an agreement to work with them. The Italians also have a programme with their new radio telescope in Sardinia. We are also working closely with Australia, which has begun funding some efforts in this area and, for the first time since the early 1990s, NASA also has related activities.

This demonstrates that there are robust SETI efforts taking place around the world, and so, if there were a putative detection of a signal, then I believe that the first thing to happen would be a validation by the SETI community.

It is worth mentioning the recent announcement of the discovery of phosphine in Venus’s atmosphere. This is an incredibly exciting discovery and we are working on a potential early mission to see if we can go to Venus to validate that.

Of course, we also have to take into account how excited both the public and governments would be, should we detect a signal. Some would undoubtedly be very excited. But polls have shown that many people already believe that aliens are visiting the Earth, so there is also a sense that if we were to announce the detection of a signal that originates light years away, then these same people wouldn’t be very surprised at all.

Governments, on the other hand, may react differently. We are working with governments closely on this, and we have been told that should a signal be detected then we are not to try to communicate.

How do you consider issues such as panspermia in the project?

This was the topic of a small conference that we held about 18 months ago, where we explored the idea of whether life is able to travel between stars and whether it really arose in our Solar System. The discussions at this event also raised the issue of what is known as ‘directed panspermia’, which suggests the possibility that life was intentionally planted on Earth billions of years ago.

One of the most interesting points made on this topic was by Professor George Church, a geneticist at Harvard, who said that it is perhaps more important to consider the possibility that the technology we are developing could mean that at some point later in the century we could plant life on potentially habitable or even as yet undiscovered life-bearing planets around nearby stars. That, of course, raises many ethical issues, and we had therefore planned a major conference at the University of Durham on these areas where we intended to invite theologians and philosophy experts. Unfortunately, the event did not go ahead because of the COVID-19 pandemic, but we do want to host the conference when we can.

Turning to the ERC 2020 Martian rover competition, why are such events important?

Such activities get young people excited about science, technology, and exploration, which is hugely important. The other half of our foundation, which I am also nominally in charge of, is the Breakthrough Prize, which was started by Milner, Sergei Brin, Mark Zuckerberg, and others. The question behind that was how do you inspire a young person to go into science and technology as a career? Milner, Brin, and Zuckerberg have, of course, become billionaires on the back of science that was done a century ago, and so the question was: who is going to do the science now for the next generation? The idea them emerged that, instead of having young people admire and look up to movie stars, singers, sports stars, or even politicians, they should look up to scientists.

We have made a good start in this with the Breakthrough Prize, and the Breakthrough Junior Challenge, which is for people between the ages of 13 and 18, is particularly exciting. Here, we asked the participants to make a three-minute video on a science principle. I am a member of the selection committee, and the videos that were submitted were very inspirational. Several of the winners and indeed other finalists from past challenges have gone on to study STEM subjects and I will often hear from them and lend assistance where I can. Many have also gone on to begin careers in science- or technology-related fields. This demonstrates that prizes and competitions such as these really do play a role in inspiring the next generation. It also enables them to begin to understand how competitive the business world can be, whilst also putting them face-to-face with both their peers and their competitors.

Dr Pete Worden
Former director, NASA’s Ames Research Center (ARC)
Executive Director, Breakthrough Starshot
Tweet @brkthroughprize

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