Virtually all Hollywood science fiction – from Star Trek to Total Recall to the Alien franchise – agrees on one basic point: sometime in the near future, humanity will soup up its spaceships, stock them with silver jumpsuits, and get itself beyond the confines of our solar system.

So, in no time at all, humanity will reach other worlds, says Hollywood. We may meet new species, and someday, God willing, we’ll all get the chance to have aliens hatch out of us at breakfast.

To many of us, this vision is just a matter of time.

After all, it’s been about 40 years since the first manned space flight. Since then, we’ve put 12 men on the moon, built two space stations and sent probes to every planet but one. Indeed, with the advent of Virgin Galactic, Richard Branson’s company dedicated to space tourism, William Shatner himself is planning a space flight (for real this time).

With the captain of the Enterprise headed into orbit, can interstellar travel really be so far behind? Yes, say experts, it can.

Despite what the movies may say, travel to the stars remains far beyond our grasp. We have no idea how we are going to overcome the obstacles that stand in our way. Nothing we’ve tried so far comes close.

Scientists are faced with three basic problems. Put simply, our engines are far too slow, our ships are far too heavy, and long term exposure to space tends to kill us.

The Voyager space probes offer a good illustration of just how daunting the distances are. Sent skyward in the final days of disco, Voyagers I and II hurtled past the outer planets in the early 1990’s at a whopping 59,000 km per hour. At that speed, the probes will reach the nearest star in about 60,000 years — hardly the stuff of compelling cinema.

To speed the trip up would require a huge increase in fuel weight, which itself would create problems. The amount of fuel required to shorten the trip to the nearest star would be enormous. Even a nuclear fusion engine, one of the most powerful conceivable, would require (and this image is pilfered shamelessly from NASA’s Jet Propulsion Laboratories website) close to a billion super tankers full of fuel to make the journey in a reasonable time. That’s assuming you don’t want to do anything fancy like come back. Or do it in less than nine centuries. Or see something other than the nearest star.

Apart from all this, another major problem is keeping the occupants alive.

Living in space isn’t a problem close to Earth. But when you step out from the shelter of the planet’s magnetic field — about a fifth of the way to the moon — things start to get ugly. The level of radiation increases dramatically, with severe consequences for the health of astronauts.

So far, we don’t know how to shield vessels either. Metal itself becomes radioactive in the presence of this kind of radiation. More effective blockers, such as liquid hydrogen, would have to be about two metres thick to provide protection – hardly a practical solution.

The technology to solve the problems of speed and weight are even further away.

However, over the years a number of solutions to this problem have been proposed. These range from the sensational but environmentally unfriendly Project Orion — which called for detonating nuclear bombs behind a spacecraft during launch — to my personal favourite, Robert Forward’s interstellar laser sails.

Forward’s plan was simple: build a laser that would use 10,000 times the energy produced on Earth and fire it at a reflective space sail 1,000 km across. Although not lacking in pizzazz, the plan was ultimately cast aside when critics became convinced it might be impractical.

These have been more or less our best ideas to date.

In recent years, NASA has looked seriously at some wild ideas for making the movies come true. In 1996, NASA founded the Breakthrough Propulsion Physics Project (BPPP), whose stated purpose was to explore science’s most radical theories until they came up with something that worked.

The BPPP looked at everything from making wormholes to warping space-time to creating “negative mass.” Their progress was limited, though, and in 2002 the project was cancelled.

Without a giant leap in technology, humanity will be restricted to unglamorous exploits of sending probes to explore / crash into / lose power near our various next door neighbours.

For now, at least, Hollywood’s spaceships will have to remain in the movies.

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