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CHOCOLATE, marshmallows and basalt rock aren鈥檛 normally associated with interstellar travel. But all were involved in recent tests of DE-STAR, a laser technology that might, one day, propel spaceships bound for the stars.

It is just one of the ideas presented last week at in Dallas, Texas 鈥� the first public meeting of the group, which aims to pursue designs for interstellar craft. Others include a 10-kilogram craft, a 鈥淐ubeSat鈥�, and one that makes its own fuel from the hydrogen in the interstellar medium.

Dreams of interstellar travel are nothing new, and many still think that they will remain just that. But the non-profit group, formed in 2011 from the ashes of a similar 1970s effort, , say that several factors make such an ambitious goal worth reconsidering now.

Firstly, from SpaceX to Virgin Galactic, commercial firms are giving behemoths like NASA a run for their money, constructing spacecraft faster and for less cash and sparking a range of new ideas for what can be done in space 鈥� from tourism to mining asteroids. 鈥淣ow is a good time if you want to do things differently,鈥� says Marc Millis, a former NASA propulsion engineer and founder of the , which also promotes interstellar flight.

There鈥檚 also new interest in deep space thanks to NASA鈥檚 now-defunct, alien-planet hunting Kepler space telescope (see 鈥�NASA鈥檚 superstar planet-hunter can鈥檛 be saved鈥�), which may yet reveal the ultimate prize: an Earth twin. For Richard Obousy, president of Icarus Interstellar, such a find is a necessity, and we need to go there. 鈥淎ny single-planet species is doomed to extinction,鈥� he says. Given the re-engineering required to make even the most hospitable planet in our solar system, Mars, capable of hosting a lasting human colony, it might just be easier and cheaper to find an alien planet, adds wormhole physicist of the Institute for Advanced Studies in Austin, Texas.

鈥淎ny single planet species is doomed to extinction 鈥� so we need ways to escape the solar system鈥�

More immediately, short-term applications for several starship technologies are emerging that could provide the initial funding needed to get interstellar projects off the ground. 鈥淚 can鈥檛 think of any scientific endeavour involving more long-range, high-risk/high-reward challenges than this, many of which could enrich and transform present-day civilisation enormously,鈥� says , a physicist from the University of San Diego, who attended the conference.

DE-STAR, short for Directed Energy Solar Targeting of Asteroids and Exploration, is a case in point. As its name suggests, the initial goal is to put an array of infrared lasers in Earth orbit. The idea is to produce a beam that is both focused and powerful enough to annihilate asteroids and space debris 鈥� or at least vaporise sections of them to provide a thrust that pushes them out of the way of a collision with Earth, or precious satellites.

In recent lab tests, at the University of California at Santa Barbara and colleagues, used a high-power laser to vaporise various asteroid-like materials 鈥� for fun, the team also tried out some food.

Interstellar travel won鈥檛 use vaporisation, though. Instead, the lab-sized laser could be scaled up and launched into orbit as part of an array whose rays could then be beamed at an interstellar craft. Just as a solar sail is propelled by reflecting photons from the sun, a mirror on the starship would reflect the laser light and accelerate the craft.

The challenges are immense. At the meeting, Lubin presented his calculation that an orbiting laser array 10-kilometres wide would be needed to propel a tiny 100-kilogram craft to 2 per cent the speed of light, fast enough to escape the solar system鈥檚 gravitational pull. And that鈥檚 with the lasers all working together, a feat no one knows how to achieve.

Still, beam sails are regarded as the most promising tech for a starship, since solar sails have already reached space. And at the same meeting, Icarus Interstellar member proposed another interim technology 鈥� for a beam-powered sail, based on microwaves, that he is working on. Given the recent drive to put humans on Mars, he suggests a beam-sail-powered 鈥淢ars-FedEx鈥� that can get stuff 鈥� emergency vaccines say 鈥� to the Red Planet in a month, instead of a year or two.

Of course, an interstellar voyage would take a lot longer, so others are focused on a fast ride, including Michael Minovitch, who in the 1960s came up with the idea of trajectories, which use the gravity of planets to speed up planetary probes. He is now revisiting another idea from the time 鈥� an interstellar ramjet (see picture). The device would scoop up hydrogen gas from the interstellar medium using strong magnetic fields, ionise it and squeeze the charged particles into a fusion reactor that could accelerate the ship to near the speed of light. Like solar sails, you wouldn鈥檛 have to carry all your propulsive fuel with you. But the ramjet could go much faster. Assuming an acceleration of 0.7 g, a bit less than the gravitational acceleration of Earth, plus newly designed structures for the scoop, which he presented at the conference, Minovitch calculates that the ship could get to our nearest star, Alpha Centauri, and back in 8.8 years 鈥� and you would also have travelled in time, as 13 years would have passed on Earth.

As well as ignoring drag forces, the huge caveat is that all this requires a fusion propulsion system, which doesn鈥檛 exist 鈥� even experimental fusion systems on Earth don鈥檛 yet produce more energy than they consume. But it鈥檚 perhaps more likely than travel via a wormhole or warp drive (see)鈥� which aims to bend space-time itself to let a craft take a shortcut.

None of this need prevent a launch, though. Also present at the meeting was Andreas Tziolas, who leads , which aims to launch an interstellar mission by 2015. Tin Tin鈥檚 secret is to send a bunch of CubeSats, several of which have already been used for cheap missions to low Earth orbit, straight to Alpha Centauri, 4.3 light years away. True, they won鈥檛 arrive for 25,000 years, but then it would take Voyager 1 75,000 years to go the same distance, if it were headed in that direction. Hopefully, someone else will get there sooner, much sooner. Tziolasis鈥檚 goal is to prompt a game of catch-me-if-you-can. 鈥淚t鈥檚 our ambition to be the first spacecraft to be overtaken on the way,鈥� he says. 鈥淪omeone has to start.鈥�

鈥淚t鈥檚 our ambition to be the first spacecraft to be overtaken on the way to Alpha Centauri鈥�

The group still needs to attach a nuclear power source. CubeSats are currently powered by batteries and solar cells, but to exit the solar system they will need a radioisotope thermoelectric generator, the power source for the Voyager and Cassini missions. They used plutonium, but Tin Tin is likely to use americium, which is easier to obtain, though it has not been flight-tested.

For some, it鈥檚 all still pie-in-the sky. 鈥淚nterstellar projects require too many miracles to make it possible,鈥� says meeting attendee Doug Matzke from Dallas, who independently studies quantum computing, itself a futuristic field.

But the Icarus Interstellar team remains excited, particularly by projects like Tin Tin, which at least provide the prospect of an actual mission, in contrast with the slow pace of government agencies in tackling the interstellar challenge. 鈥淲e鈥檙e not prepared to wait,鈥� says Kelvin Long, a UK-based co-founder of Icarus Interstellar.

This article appeared in print under the headline 鈥淭ake me to Alpha Centauri, one day鈥�