If movies are to be believed, NASA interstellar flight capability is just around the corner. Unfortunately, the reality of the situation is a bit different. Most people seem to vastly underestimate the incredible distances between the stars, and for NASA to traverse these distances will require either remarkably advanced propulsion technologies or new ways of thinking about exploration.
The Challenge for NASA
Interstellar distances are so vast as the virtually beggar the imagination. The distance to the nearest star – Alpha Centauri – is over 25 trillion miles. That’s trillion with a T. And that’s just the nearest one.
At this moment, the fastest vehicles human beings have ever built are the Voyager unmanned spacecraft. These are traveling out of our solar system at 38,000 miles an hour.
But even if Voyager was traveling in the direction of Alpha Centauri – which it isn’t – it would take Voyager thousands of years to traverse the distance. So clearly, conventional rockets aren’t going to get the job done.
Fusion is the energy process that powers the sun and that always seems to be 20 or 30 years away from commercial use by human beings. As reported by Nature, a massive experimental fusion reactor is being built in France that – it is hoped – will achieve the breakeven point of producing more energy than it takes to run sometime in the 2030s.
In theory, at least, a functioning fusion reactor could cut the travel time to the nearest star – Alpha Centauri – to less than a single human lifetime. However, there are certain drawbacks to using fusion rockets for this purpose. One is that we don’t have them yet. Another problem is that this rocket would have to carry a large amount of fuel along with it – fuel that the rocket, in turn, would have to push along with the spacecraft. An alternative to this might be the Bussard Ramjet.
The Bussard Ramjet
A Bussard ramjet is essentially a fusion rocket that doesn’t carry its own fuel. Instead, it uses a scoop – which might be physical or more likely made up of magnetic fields – to gather up stray atoms of hydrogen isotopes as the rocket travels through space.
This would have the benefit of allowing this theoretical NASA interstellar spacecraft to be much lighter and less expensive. Again though, we don’t know how to do fusion yet. More than this, it’s uncertain whether we could build a fusion reactor that could operate on the specific types of hydrogen isotopes available in the vacuum of interstellar space.
Then there’s the old science-fiction standby, antimatter. In shows like Star Trek, antimatter seems to be as easily obtained as a cup of sugar – and is no more pricey. Unfortunately, real-world physics don’t quite work that way. Antimatter is the most rare, difficult to obtain, and expensive substance ever created.
As noted by Science ABC, all of the antimatter ever created in history would be insufficient to bring a cup of tea to a boil. Yes, antimatter completely destroys an equal amount of ordinary matter – releasing “vast” amounts of energy in the process.
But the quantities of antimatter we’ve manufactured in particle accelerators are so tiny – basically individual particles – that it would be useless for building a propulsion system for interstellar travel. A NASA interstellar spacecraft using antimatter for propulsion would literally cost trillions of dollars just for the fuel. So that’s clearly out.
The most realistic option at present for NASA achieving interstellar flight with currently existing technologies might just be the use of generation ships. These would be vast, rotating space colonies designed to provide an earthlike environment for the interstellar travelers as they made their way to another star system.
The ships would go at a snail’s pace compared to the previously mentioned options. This means that the people who reach Alpha Centauri – or whichever star system the spacecraft is aimed at – will be the descendants of those who originally set off from Earth. Depending on how long it takes the NASA interstellar generation ship to travel the enormous distance involved, centuries could have passed before the human colonists on board the ship reached their destination.
[Featured Image by Sean Gallup/Getty Images]