To Boldly Go…

by Nicholas Mee on July 14, 2017

Pioneer 10 during final preparations.

We Earthlings have long dreamed of visiting the stars. This fantasy may soon be realised – remotely at least.

The first artificial craft ever sent beyond the solar system was Pioneer 10, launched in March 1972. Its main mission was to study the planet Jupiter and it was the first probe to visit such a distant world. Pioneer 10’s stunning close-up images of the gas giant helped to transform our understanding of the solar system.

Swinging past Jupiter in December 1973, Pioneer 10 was propelled beyond the gravitational embrace of the sun and out of the solar system. The craft continues on its way in the direction of the star Aldebaran, the bright red eye of the angry bull that is the constellation Taurus. Travelling at around 40,000 kilometres per hour, it will take Pioneer 10 about two million years to cover the 65 light years separating us from Aldebaran.

The Pioneer 10 plaque designed by Carl Sagan and Frank Drake. (Judging by the probe’s size in the photograph above, NASA seems to have wanted the aliens to believe it was built by giants.)

Carl Sagan and Frank Drake, pioneers in the search for extraterrestrial intelligence, created a striking design that is engraved on a gold-plated plaque carried by Pioneer 10. The plaque will offer clues to the origin of the probe in the extremely unlikely event that it is ever found by an alien intelligence. The design shows the trajectory of the probe through the solar system and gives a key to find where the probe came from by mapping the directions from the sun to various pulsars. It was assumed that any civilization sophisticated enough to intercept an interstellar visitor would easily decipher the symbols.

The plaque shows the shape and size of the creatures that dispatched the spacecraft by comparison with the size of the probe. This also give us an idea of just how hefty a craft Pioneer 10 was. In the decades since Pioneer there have been incredible developments in technology. In particular, computer processors and other solid state devices have shrunk until chips of a few grammes in weight sit comfortably in the palm of one hand and contain far more processing power than any probe of the 1970s.

Breakthrough Starshot

In April 2016 an ambitious research project Breakthrough Starshot was launched with the aim of developing technologies that will enable us to visit the stars. The seriousness of the project can be gauged by the profile of its board members which include world renowned physicist Stephen Hawking, famous for his revolutionary ideas about black holes, and Freeman Dyson, one of the architects of the quantum theory of electromagnetism. Dyson was also a leading figure in Project Orion, a quite staggering secret project sponsored by the United States government in the early 1960s, whose goal was to build spaceships that would ride shock waves generated by trails of small nuclear weapons dispensed from their rear. Dyson was planning to send astronauts to Saturn well before Apollo reached the Moon. The board also includes tech billionaire Mark Zuckerberg founder of Facebook and Russian billionaire Yuri Milner who has donated $100 million of development funding to kick-start the project.

Breakthrough Starshot aims is to show the feasibility of sending a mission to our nearest stellar neighbour Alpha Centauri which lies at a distance of 4.37 light years or 40 trillion kilometres. Traversing such an immense void is anything but straight forward and there are many technological challenges that must be overcome if the project is to succeed, but the team are optimistic that the mission can be launched within about twenty years.

Stephen Hawking and Freeman Dyson launching Breakthrough Starshot.

Of course, there won’t be any people on board. The aim is to send a miniature nanocraft, essentially a silicon chip containing a computer, camera, laser communication system and a plutonium power source, attached to a large sail several metres across. The propulsion will come from an array of Earth-based lasers firing a 100 Gigawatt beam at the sails. Within a matter of minutes this will accelerate the craft to one fifth of the speed of light. It will cross Mars’ orbit within an hour and, whereas the recent New Horizons probe took nine years to reach Pluto, the nanoprobe will cross the orbit of Pluto the day after launch. Like the schooners of old that sailed the world’s oceans, these miniature ships will be blown to the stars across oceans of interstellar space.

A spaceship as envisaged by Breakthrough Starshot. Credit: Kevin Gill, Nashua, NH, USA.

Alpha Centauri is a multiple star system. It has two main components that orbit each other every 80 years. They are designated Alpha Centauri A and B and have 1.1 and 0.9 solar masses respectively. At their closest they are separated by a distance comparable to that between the sun and Saturn. A third star known as Proxima Centauri, because at 4.24 light years it is closest to us, orbits the two main stars every half a million years or so. Proxima is a very faint red dwarf with just one eighth the mass of the sun. In August 2016 the European Southern Observatory announced the discovery of a planet orbiting Proxima with a slightly greater mass than the Earth. This planet, which takes eleven days to orbit Proxima, and lies in its habitable zone will definitely put Proxima on the tourist route to the main stars of Alpha Centauri.

At one fifth the speed of light the journey to Alpha Centauri will take just over twenty years. The nanocraft will then send back images and information about the stars and planets in the system and it will take over four years for us to receive this data. There is no means of slowing down the nanocraft on arrival, so it will race past at ultrahigh speed. To overcome this constraint the plan is to release a fleet of hundreds of such craft at short intervals. A mothership containing the nanocraft will be launched into Earth orbit and then release the nanocraft on cue. Each nanocraft will use photon thrusters to position itself in the path of the ground-based laser system, then hoist the main brace and await a fair wind before being blasted to the stars. Twenty years or so later the nanocraft will race through the Alpha Centauri system in a single day, but if 100 nanocraft are launched at daily intervals, as one exits the star system the next will enter and a continuous stream of data will be beamed back to Earth for 100 days.

An artist’s impression of the laser array for Breakthrough Starshot situated at high altitude in a location such as the Atacama Desert in Chile.

Many enormous hurdles must be overcome before sailing to the stars becomes a reality, but the technological advances that will be made along the way should benefit us all.

Further Information

There is more information about Breakthrough Starshot here:


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