It is 45 years since the first Star Trek episode aired on television – on September 8th, 1966! Known for its portrayal of a future where a space-faring humanity boldly goes where no one has gone before – it has firmly placed some science fiction ideas into popular culture. We know and love warp drive and ion engines.
But how realistic are these? In Star Trek warp is used to provide faster than light travel – a necessity for any story line that needs a new planet to visit every week. In one of the prequel series, warp 4.5 is described as being the speed to get to Neptune and back in 6 minutes. Considering that Voyager 2 went past Neptune in 1989, having being launched from Earth in 1977 – being able to make that trip out in 3 minutes, slow down and come back in another 3 minutes would be quite an achievement!
With current technology this is what we can do: consider a trip to the nearest star, Proxima Centauri – just over 4 light years away (that’s 40 trillion km). The fastest spacecraft is Voyager 1, now travelling at over 60,000 km/h. If it were headed to Proxima Centauri, it would get there in 76,000 years. If we wanted to get there faster – say in 900 years – well, by firing the space shuttle engines continuously we would need more than the mass of the Universe in fuel. Warp does away with all of this, by using the idea of travelling faster than light – and theoretically some work has been done on this. As we understand the physics of it, objects can’t travel faster than light within space-time, but it seems that there is no restriction on how fast space-time itself can move. So warp travel suggests contracting space-time in front of the ship, expanding it behind the ship and the ship would rest in between the expanding and shrinking space-time, essentially surfing down the side of this bubble. This is not completely unheard of – in the “Inflationary Universe” models of the early universe, it is thought that space-time expanded faster than the speed of light during the early moments of the Big Bang. So if space-time can expand faster than the speed of light during the Big Bang, why not for a warp drive? Needless to say, more work needs to be done on this, with some calculations suggesting that to make a warp field by manipulating the 11th dimension requires the equivalent of the entire mass of Jupiter turned into energy via E=mc2! The author of that work does state “Warp drive isn’t doable now, and probably won’t be for the next several millennia!”
Ion engines are a bit less science fiction – having been used in one form or another since the late 1950s. The principle is simple- you take a gas and ionise it, which means giving it an electrical charge. The positively charged ions of gas can then be sped up by an electric field and pushed out of the engine, giving a thrust back in the opposite direction. Operating in the near vacuum of space, ion engines shoot out their propellant much faster than the jet of a chemical rocket – this delivers about ten times as much thrust per kilo of propellant used. Of course, the amount of fuel is much less, so these types of engines are used for more leisurely paced missions, where there is plenty of time available to reach the high speeds possible.
Ion engines have been used by the European Space Agency to send a spacecraft to the Moon. Smart1 reached speeds of nearly 10 000 kilometres an hour!- but did take one year, one month and two weeks to get to the Moon. NASA used ion engine technology to power Dawn on her voyage to the asteroids and they are an essential part of the Bepi Columbo mission being planned for Mercury. These engines have certainly come on a lot in the last 45 years!
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