Big science requires big thinking. Thinking that extends across national borders, political schisms and generations. And big science does not come much bigger than sending a man or woman from the relative safety of our own solar system to that of another star.

Yet, humanity has already shown, largely driven by the scientific community’s insatiable curiosity, that it can come up with such big ideas and turn them into reality. Take the Large Hadron Collider (LHC) at the CERN particle physics laboratory in Geneva, Switzerland. The search for the Higgs boson at LHC involves almost 8,000 people from 685 institutes in 59 countries. It is hard to get more international than that.

While individual scientists still can and do push the boundaries of knowledge, many of the most exciting projects really need these sorts of international collaboration to drag them into the realms of affordability.

Making big science affordable is just one challenge that needs a coordinated, international response. You need the brightest minds to make them technically feasible. You also need time – lots of it. Just as inflation makes a debt more affordable over time, technological advances make impossible projects possible.

LHC was first conceived in the late 1970s and early 1980s and finally got the green light to be built in 1995; it was not switched on until 2008. It is not hard to see that with such a long timescale between conception and birth, what is eventually built bears just a rudimentary resemblance to the original idea.

Just think of the technological changes that have occurred over that 30-year timespan: we have seen the invention of personal computers, high-temperature superconductors and the World Wide Web in that period. This shows that you need a special sort of vision for big science, the sort of vision that allows you to plan to build something even though the technology to do so does not yet exist.

Our nearest star, other than the Sun, is Proxima Centauri, a red dwarf that is believed to make up a trinary system with Alpha Centauri A and B. Proxima Centauri is 4.24 light years away from Earth.

The light year is a devious fellow. It is what astronomers use to make the universe manageable but in doing so it hides the vastness of space. It is the distance light travels in one year and since light travels at 300,000 kilometres per second in a vacuum, it can travel a very long way in a year.

In units that we can actually grasp, those 4.24 light years are actually 40 trillion kilometres.

Of the hundreds of people who have ventured into space, most have just crept beyond the line that demarcates the definition of space - just 100 kilometres from Earth. Only the Apollo astronauts have travelled further, quarter of a million miles to the Moon and the same back, give or take the odd lunar orbit. 40 trillion kilometres (that’s one way, don’t forget) is a challenge several orders of magnitude more difficult.

We will clearly need to go fast. We have already shown we can make fast spacecraft. Helios 2 was launched in 1976 to study gamma ray bursts. The spacecraft was launched into a highly eccentric (elliptical) orbit which passed the Sun at 0.29 AU at its closest approach (perihelion), moving out to 1AU at its furthest point (aphelion). Helios 2 holds the speed record for a spacecraft, picking up its velocity from a gravity assist manoeuvre around Jupiter. At its fastest, the spacecraft was travelling at more than 240,000km per hour.

Even at this speed a ship would take a very long time to reach Proxima Centauri – around 133,000 years, not too much shorter than the time that Homo sapiens has been in the ascendancy on Earth.

We will have to travel faster – much, much faster. Scientists have already proposed technologies that might be able to do this.

Rocket-based systems seem unlikely since the spacecraft would have to carry its own fuel. Only nuclear-propelled rockets seem to offer the slim chance of providing long-lived propulsion in a small enough space.

Vast sails, powered by lasers rather than the wind of Earth-based vessels, seem to offer the best hope yet these have only been tested in small-scale experiments in the lab rather than in space.

We also need to think about the long mission times. If we are to believe in the universal limit of the speed of light then a return journey to Proxima Centauri would take at least 8.48 years (4.24 years there and the same back), far in excess of Valeri Polyakov’s 437 days on board the Mir space station. He was in the position of being supplied by regular visits from supply spacecraft too, a luxury that an interstellar mission would not have.

We also need to think about something else Einstein discovered – time dilation. As our proposed spacecraft gets closer and closer to the speed of light, the effects of time dilation become more apparent – not to those on the spacecraft itself but for those waiting at home, the basis of the so-called twins paradox. Those on the ship would only experience the years it took; those at home could experience tens, hundreds or thousands of years while waiting for the mission’s return.

Given the potential challenges involved, a robot may be the first explorer to reach our next nearest star, particularly if we think of the time dilation challenges.

Our exploration of Mars shows how this might happen. Robots have already been to Mars and operate on the surface today, furthering our knowledge of the planet. The biggest robot yet, Curiosity, was launched in November 2011 and will arrive at Mars in August 2012.

We are already dreaming of sending people to Mars. Last year, US president Barack Obama said “By the mid-2030s, I believe we can send humans to orbit Mars and return them safely to Earth. And a landing on Mars will follow. And I expect to be around to see it.”

One man, Elon Musk, the billionaire founder of PayPal and CEO and Chairman of SpaceX, believes it could happen even sooner – within 10 years in the best-case scenario and 20 years at the outside, using his company’s Falcon and Dragon rocket technology.

Musk, NASA and the US are not the only ones interested in Mars either: witness the recent attempt to launch Russian and Chinese missions to the planet, Phobos-Grunt and Yinghuo-1, unfortunately lost before they even left Earth orbit.

But let’s think bigger than just going to Mars.

The challenges of going to Proxima Centauri are mind-blowing but that does not mean we should not dream of it, as JFK dreamed of going to the Moon.

In 2006, 14 space agencies, including NASA, ESA, Roscosmos, ISRO and JAXA, came together to form the International Space Exploration Coordination Group (ISECG) with a goal of “elaborating a vision for peaceful robotic and human space exploration”.

It is a start. However, the group has our own backyard – “destinations within the Solar System where humans may one day live and work” - as its focus.

Others are looking further.

In 2009, a group of volunteers got together to launch Project Icarus, a five-year engineering study to design an interstellar spacecraft.

While the name of the project is rather ominous if you know your Greek mythology, its name derives from the fact that the study was spawned by Project Daedalus, another five-year study launched by the British Interplanetary Society in the 1970s to assess the feasibility of interstellar travel.

The earlier project demonstrated that it is possible, “by using current or credible extrapolations of existing technology, to launch an interstellar probe that could reach another solar system on timescales of a normal human lifetime”.

The project currently has 20 research teams. One of these teams is looking at which candidate star such a mission would go to. Proxima Centauri may be close by in galactic terms but it might be better to choose a star that has a confirmed exoplanet similar to Earth.

Another team is looking at potential propulsion systems for such a mission.

One promising propulsion system is considered to be inertial confinement fusion, in which small pellets containing the heavier hydrogen isotopes of deuterium and tritium are pulsed with high-energy lasers to cause nuclear fusion.

Others have proposed alternatives, including the use of powerful X-ray lasers to accelerate the spacecraft.

One NASA-funded team has been looking at the use of anti-matter to get to the stars. The big advantage of antimatter is that it can generate vast amounts of energy from a small amount of material. Plug a few numbers into Einstein’s E=mc2 which governs the amount of energy available from a matter-antimatter annihilation and you quickly see why it is much more efficient than a traditional rocket-type propulsion. That is not to say there are no problems with this approach, not least producing the large quantities of antimatter. CERN, which is one of the planet’s biggest antimatter factories, says that the amount required to propel a spacecraft would take millions of years to produce (http://press.web.cern.ch/livefromcern/antimatter/FAQ.html) using current production technology.

Solar sails are another contender. The concept is that sails made from ultra-thin but durable material would be extended out behind a spacecraft, getting gently pushed along by the pressure of photons from the Sun rather like the wind pushes a sailboat. Successful lab tests of 10 and 20 metre sails were carried out at NASA’s Marshall Space Flight Center six years ago but an interstellar mission would be likely to require considerably larger sails, perhaps as much as a kilometre across. Solar sails are also reliant on the Sun and the strength of the “wind” decreases dramatically as you move further beyond the solar system.

Propulsion systems are also being studied by scientists and engineers involved in the 100 Year Starship project. This project is funded by the US Defense Advanced Research Projects Agency (DARPA) and carried out under the aegis of NASA’s Ames Research Center.

The long-term goal of the project is to “identify the business model needed to develop and mature a technology portfolio that will enable long-distance manned space flight a century from now”. But DARPA’s interest has objectives in the shorter term – the development of technologies that can also be used by the US military in the hundred years before the (possible) launch of a mission.

Project participants are researching nuclear thermal propulsion, combined imaging, power generation and distribution, propulsion and communication subsystems.

These projects show that small groups of far-sighted people are starting to take interstellar travel seriously. We need these kind of visionaries. Building an international coalition of the brightest minds will take time. We need political will. Saving up to fund an international mission to a star other than the sun is going to take a long time and will face many barriers through political inexpediency.

Neil Armstrong thought that stepping onto the Moon was a giant leap for mankind. Just think what the future astronauts chosen for such an interstellar mission will have to say to a rapt, watching world.