This post is based on a research paper I wrote for my Introduction to Astronomy course at Rasmussen College earlier this month.
As the Klingon ship bears down on the Starship Enterprise, preparing to fire a barrage of photon torpedoes, Captain Picard shouts “Maximum warp!” and the Enterprise leaps away towards another star system, faster than the speed of light. Is this scene from Star Trek purely science fiction, or is there truth to the concept of interstellar starships? Although significant scientific progress has been made in the area of space travel, energy requirements, high costs, and the problem of time still present enormous challenges to the vision of interstellar travel as portrayed in Star Trek and other films.
The nearest star system, Alpha Centauri, is about 25 trillion miles away from Earth. At the speed of a typical spacecraft, it would take more than 900 thousand years to cover this distance (Millis, 2008a)! Clearly, one of the first major barriers to interstellar travel is finding a way to achieve the speeds necessary to reach neighboring stars within a reasonable timeframe. This would require traveling close to the speed of light, at the very least. However, the amount of energy required to accelerate a ship like Star Trek’s Enterprise to just half the speed of light would be “more than 2000 times the total annual energy use of the world today” (Bennett, Donahue, Schneider, & Voit, 2014, p. 715). Where would such vast amounts of energy come from? While many ideas have been proposed, perhaps the most feasible of these was Project Orion, a propulsion system experimented with from the 1950s to 1960s which involved continuously detonating nuclear bombs behind a spaceship to propel it forward. Unfortunately, not only would this approach make for an uncomfortable ride, but it would also expose the crew to dangerous levels of radiation (Dyson, 2002). In the words of Aerospace Engineer Marc G. Millis (2008a), “we need either a breakthrough where we can take advantage of the energy in the space vacuum, a breakthrough in energy production physics, or a breakthrough where the laws of kinetic energy don’t apply” (last paragraph).
Supposing that the energy problem were solved, and a ship could achieve constant acceleration over any distance, it would only take about five years (from Earth’s perspective) to reach the nearest star, and thirteen years to reach Sirius (White, 2002). However, as the distance, acceleration period, and corresponding velocity increase an interesting effect known as time dilation starts to become apparent. The greater the ship’s speed, the slower time will pass for those onboard. A trip which takes thirteen years from the perspective of earth would only take seven years for the travelers, and even less time at rates of acceleration greater than 1G (White, 2002). For really long trips, thousands of years could pass on Earth while the travelers only experience a few decades! While this may seem like a beneficial effect, since it would allow travelers to reach destinations much further than otherwise possible, it presents an enormous problem for interstellar travel. What would be the point of sending individuals to other stars if their work would be of no benefit to those living on Earth? Any trip to a distant destination would almost certainly be one-way.
This brings us to the speculative realm of wormholes and warp drives. The special theory of relativity forbids objects from moving faster than light within space-time, but with enough matter or energy it is known that space-time itself can be warped and distorted (Millis, 2008b). In theory, space could be warped or “folded” to connect two separate points (creating a wormhole). Unfortunately, creating the wormhole would require placing a giant ring (“the size of the Earth’s orbit around the Sun”) of super-dense matter at each end of the wormhole, charging them with enormous amounts of energy, and spinning them up to “near the speed of light” (Millis, 2008b). Even if there were some way to obtain the necessary energy and super-dense matter, how would it be placed at the destination end without first traveling there? While wormholes could hypothetically be useful for frequent travel between two interstellar destinations, they do not provide a viable solution to getting there in the first place.
What about warp drives like those used in Star Trek? While the concept may sound impossible, according to a physicist named Miguel Alcubierre space could theoretically be compressed ahead of the ship and expanded behind it, allowing a ship to travel faster than light without violating the theory of relativity (Peckham, 2012). In effect, it is space that moves, rather than the ship. Unfortunately, creating a warp drive like this would require generating a ring of “negative energy,” and whether it is possible for such energy to exist is still under debate (Millis, 2008b). Assuming it is possible, it seems like this would be the most practical method of interstellar travel. It does not require long periods of time to accelerate and decelerate, passengers would not be jolted from changes in acceleration or pelted with particles of interstellar gas, and best of all time would pass at the same rate for the cosmic travelers as well as those remaining on Earth. NASA is currently in the very early stages of investigating whether such a drive is feasible.
With all the talk surrounding the possibility of moving starships through space at faster-than-light speeds, it is easy to forget that getting the ships into space in the first place is also a problem. In an article published on Gizmodo earlier this year, it was estimated that the cost of constructing a spaceship like the Starship Enterprise using technology available today would be roughly $480 billion (Limer, 2013). Astoundingly, more than 95% of this cost is simply to transport the necessary materials to space! This illustrates the disproportionately high cost of space transportation technology as it currently exists – putting a starship into space simply does not make economic sense at this point, even if we could build one.
In short, the enormous energy requirements, high cost, and problem of time all present significant roadblocks for interstellar travel. The theories proposed for faster-than-light travel are speculative at best, and far from practicality. While a breakthrough in propulsion allowing affordable, safe, and sustained acceleration could potentially allow us to reach the nearest stars, the problem of time dilation would make it infeasible to go further. Without major scientific advances in the areas of negative energy and space-time manipulation, the possibility of visiting an alien home world appears highly unlikely in the foreseeable future.
Bennett, J., Donahue, M., Schneider, N., & Voit, M. (2014). The Cosmic Perspective (Seventh ed.). San Francisco, CA: Pearson Education, Inc.
Dyson, G. (2002, February). The story of Project Orion. Retrieved from TED: http://www.ted.com/talks/george_dyson_on_project_orion.html
Limer, E. (2013, May 17). How Much Would It Cost to Build the Starship Enterprise? Retrieved from Gizmodo: http://gizmodo.com/how-much-would-it-cost-to-build-the-starship-enterprise-506174071
Millis, M. (2008a, May 2). A Look at the Scaling. Retrieved from NASA: http://www.nasa.gov/centers/glenn/technology/warp/scales.html
Millis, M. (2008b, May 2). Ideas Based On What We’d Like To Achieve. Retrieved from NASA: http://www.nasa.gov/centers/glenn/technology/warp/ideachev.html
Peckham, M. (2012, September 19). NASA Actually Working on Faster-than-Light Warp Drive. Retrieved from TIME.com: http://techland.time.com/2012/09/19/nasa-actually-working-on-faster-than-light-warp-drive/
White, R. B. (2002, August). Space Travel and Commerce using STL technologies. Retrieved from http://www.whiteworld.com/technoland/stories-nonfic/2008-stories/STL-commerce-01.htm