Inertialess drive

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The inertialess drive is a fictional means of accelerating to close to the speed of light or faster-than-light travel, originally used in Triplanetary and the Lensman series by E.E. "Doc" Smith, and later by Robert A. Heinlein, Larry Niven, and Alastair Reynolds.

The concept of inertia[edit]

Inertia is the measure of the resistance of a material body to a change in state of motion (acceleration) under the effect of an applied force. This resistance is proportional to the mass of the body, and is usually expressed (in simplest form) as F = ma.

For a body to be rendered inertialess, in principle, its mass should be reduced to zero. In classical special and general relativity, massless bodies are constrained to always move at exactly the speed of light[1] (the speed of photons in a vacuum), and the term relativity in this context in fact implies that light is always measured to move at the same speed by an observer, no matter how rapidly the observer is moving relative to any body defined as fixed. This aspect of inertialessness is explored by the more exacting authors who have adopted the term after Smith's groundbreaking use.

In classical special relativity, in order to move faster than the speed of light, a particle must have not zero mass—and inertia—but mathematically imaginary mass. This is, of course, as viewed by an external observer, and one can postulate that Smith's inertialess field is thus similar in form to a space warp that acts as a tachyon when viewed by an observer in the external universe[citation needed]. Whether this formulation can be expressed self-sufficiently in the context of Smith's fiction is, of course, irrelevant to the enjoyment of it.

Historical claims[edit]

In the late 1990s one Michael Pedler claimed to be developing an inertialess drive. His Inertialess Drive Corporation Limited was established in New Zealand in 1995, and obtained more than $6.8 million from 1,200 investors, mostly New Zealanders. However the company was placed into liquidation in 2001, and struck off the Companies Office register in 2004, without having produced a workable drive. Pedler also established Inertialess Drive Incorporation USA.[2]

Appearances in fiction[edit]

Triplanetary Universe[edit]

The possibility of inertialess travel was first suggested in Theoretical and Physical Chemistry,[3] published in 1912[4] by the Tellurian chemist Samuel Lawrence Bigelow, an alumnus of Harvard.[5] The first faster-than-light[6] drive, which achieved only partial neutralization of inertia,[7] was developed on the planet Nevia. Soon thereafter, two Tellurian scientists, Lyman Cleveland and Frederick Rodebush developed the one-hundred-percent inertialess Rodebush-Cleveland drive, which traveled (and decelerated) much faster.[8] (In contrast to accounts in later versions, there were no critical flaws with this drive, and no contribution by any scientist named Bergenholm or by Arisians.)

Physiological effects[edit]

  • The Nevian faster-than-light drive apparently had no noticeable physiological effects even to an observer as well-trained as Conway Costigan.[9] An alternative explanation is possible, however. There is no mention of the neutralization of inertia until the third installment;[8] the physics in the first two installments seems consistent with that of the Skylark universe, in which faster-than-light travel is possible without even partial neutralization of inertia. So it is possible that Dr. Smith did not come up with the inertialess drive until writing the third installment.
  • The Rodebush-Cleveland drive, in contrast, causes “a sensation akin to a tremendously intensified vertigo” which was completely incapacitating until Cleveland’s “indomitable force of will” overcame it.

Lensman Universe[edit]

Galactic Civilization developed for a long period using only the semi-inert drive, which was presumably similar to Nevian partially inertialess drive discussed above. The exact duration is not known, but even as late as the Third Galactic Survey it still “took years to cross the galaxy.”[10] Because the key piece of inertialess technology is known as the Bergenholm, it seems likely that an engineer by that name was responsible for a key advance, but little is known for certain. Dr. Bergenholm is referred to as the “late Dr. Bergenholm himself” in the original,[11] which suggests that he was a more recent figure than in the ret-con version, below.

Physiological effects[edit]

  • The fully inertialess drive in Galactic Patrol, even for Worsel, who had never experienced it before, apparently has no noteworthy ill effects.[12]

Triplanetary/Lensman Ret-con Universe[edit]

In the revised book versions of Triplanetary and the core Lensman novels, the partially inertialess drive was given by Arisia to Nevia, and the fully inertialess drive was initially developed by scientists Rodebush and Cleveland, but the early drive was considered to be a "man-killer." Progress was made when the Triplanetary scientist Nels Bergenholm, activated by the Arisian Drounli, came up with a "hunch" which solved the phasing problems of the original Rodebush-Cleveland drive. This made the drive safe and commercially practical, and in recognition of his achievement, the drive was thereafter called a Bergenholm.[13]

Other authors' universes[edit]

Inertialessness, though not for faster-than-light travel, is discussed in Robert A. Heinlein's Methuselah's Children, Isaac Asimov's short story The Billiard Ball, Larry Niven's Known Space universe, Orson Scott Card's Speaker for the Dead, Arthur C. Clarke's 3001: The Final Odyssey, and Alastair ReynoldsRedemption Ark. See the Lensman Technology article for details. Authors Ken Farmer and Buck Stienke have the Tyranians (Grays) utilizing the inertialess drive in their new SyFy series,[citation needed] "Aurora", beginning with "Legend of Aurora".

Inertialess drive was the means of FTL travel used by the Necron warships of the Warhammer 40,000 universe. Though assumed to have been retconned out of existence by the 5th edition codex description of sublight torchships used for Necron colonisation, the later Shield of Baal: Exterminatus confirmed the continued use of Inertialess FTL drives. Presumably the Necrons developed Inertialess drive technology some time after their initial colonisation waves.

See also[edit]


  1. ^ "Massless Particles Traveling at the Speed of Light". 2006-07-23. Retrieved 2008-03-16. 
  2. ^ "Securities Commission New Zealand. Warning. Inertialess Drive Corporation Limited & Inertialess Drive Incorporation USA". 
  3. ^ "The Epic of Space," page 84, in Of Worlds Beyond, 1947. Dr. Smith gives the title as Theoretical Chemistry–Fundamentals, and provides only a last name. Given the other errors in “The Epic of Space,” e.g., “Trweel” for “Tweel” on page 80, the misspelling of “Constantinescu” on page 84, and, arguably, E. E. Evan's analysis of Triplanetary on page 87, the error does not seem implausible.
  4. ^ AIP Niels Bohr Library
  5. ^ Harrison Genealogy
  6. ^ Triplanetary, Amazing February 1934, p. 84.
  7. ^ Amazing March 1934, p. 33.
  8. ^ a b Amazing March 1934, p. 28.
  9. ^ Amazing February 1934 p. 84.
  10. ^ Galactic Patrol, Astounding September 1937, p. 34.
  11. ^ Astounding November 1939, p. 40; omitted from p. 131 of the first edition.
  12. ^ Astounding October 1937, p. 62; book p. 51.
  13. ^ Triplanetary, by E.E. "Doc" Smith