Destination Universe:
Some Thoughts on Faster-Than-Light (FTL) Travel
Faster-than-light (FTL) travel is a staple of science fiction and it has been seriously
investigated by a number of physicists. Despite the challenges both theoretical and practical,
the idea of FTL travel is intriguing because if it can be achieved it offers the human race the
chance to travel to the stars within the lifetimes of the crew. Three of the principal FTL
concepts are discussed in this paper: (1) tachyons which are hypothetical FTL particles with
properties consistent with the special theory of relativity; (2) wormholes which offer a
window to distant star systems using general relativity; and (3) warp drives which employ
general relativity to modify space-time to get around the velocity of light speed limit. Issues
facing hypothetical FTL travellers are discussed.
In space there are countless constellations, suns and planets; we see only the suns because they give
light; the planets remain invisible, for they are small and dark. There are also numberless earths
circling around their suns, no worse and no less than this globe of ours. For no reasonable mind
can assume that heavenly bodies that may be far more magnificent than ours would not bear upon
them creatures similar or even superior to those upon our human earth.
---Giordano Bruno
(1548 – 1600)
Burned at the stake for heresy (17 February 1600)
1. Introduction
The stars have beckoned the human race since before the dawn of history. Sometimes thought to be deities,
other times guides, their apparent movements were studied by early “astronomers” in such places as China,
Mesopotamia and Egypt. The early speculations of Lucretius (c. 90s BCE to c. 50 BCE) and Giordano Bruno
(1548-1600) have come to pass – there are, as of 03 June 2016, 3,272 confirmed exoplanets.1
Can we travel to these planets? That is an age-old question, one that is of more than academic interest. There is
the undeniable urge to see firsthand what is “out there” (“over the next mountain”). One can argue that humans
share the same biological urge that has enticed creatures from the sea to the land to the air, now into near Earth
space and perhaps to Mars as Dr. Chris McKay has suggested.
2
Shall we carry it to the stars and, if so, how will we
travel across the vast interstellar distances?
Two methods of interstellar transportation immediately suggest themselves. One approach is to “upgrade” our
existing means of interplanetary travel by using “… very large star-ships moving at relatively low velocities and
therefore taking long periods to reach their stellar destinations”.3
“The second approach” astronomy writer John
Macvey suggested “is to think in terms of rapid interstellar travel”.3
Three such “rapid-travel” approaches will be
qualitatively discussed in this paper: (1) tachyons (hypothetical FTL particles); (2) wormholes; and (3) warp drives.
(To aid the reader a list of key acronyms used in this paper is presented in Appendix A at the end of the paper.)
* 5971 West Redbridge Drive; Boise, Idaho 83703-3431; Fellow
1
Propulsion and Energy Forum
July 25-27, 2016, Salt Lake City, UT
52nd AIAA/SAE/ASEE Joint Propulsion Conference
2
AIAA 2016-4918
1
This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.
2
2
American Institute of Aeronautics and Astronautics
The first method (low velocity star-ship) listed by John Macvey runs into an immediate problem: for example,
travelling at the speeds of the two Voyager spacecraft it would take almost 75,000 years to reach the Alpha Centauri
system (the nearest star system).4
If we try to speed up the spacecraft the problem becomes almost intractable. For
example, Robert Frisbee has calculated that to move a payload mass of 100 metric tons (approximately the mass of a
Space Shuttle Orbiter) at 50% the speed of light (0.5 c) would require an energy “… about 2.7 years worth of the
annual energy production of human civilisation”.4
Furthermore, Frisbee noted that “… adding the required
propulsion system to reach interstellar transportation speeds results in vehicle systems with dimensions on the order
of planetary diameters, masses of hundreds of billions of tons and power levels thousands of time that of human
civilisation”.4
Thus, we need to think “… in terms of rapid interstellar travel”.3
Speeds at or beyond the speed of light (c ≈ 2.998 x 108 m/s) for objects with mass have often been described as
impossible, as violations of the “laws of physics”. Fortunately for our descendants there may be some ways around
this “speed limit” which will be briefly discussed or listed in this paper
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