The 1990 film “The Hunt for Red October” (based on Tom Clancy’s 1984 debut novel of the same name) featured actors like Sean Connery and Alec Baldwin, but the star of the movie for physicists was a revolutionary new magnetohydrodynamic (MHD) marine propulsion system. The so-called “caterpillar drive” worked with no moving parts, allowing a nuclear missile-armed Soviet submarine to approach the U.S. coast undetected. As the submarine captain (played by Connery) said, “Once the world trembled at the sound of our rockets … now they will tremble again—at the sound of our silence.

1.
In Clancy’s novel
, Red October’s propulsion system was not magnetohydrodynamic but based on a more conventional (but also unusually quiet) “pump-jet” system employed in the massive Typhoon-class Soviet submarines of the 1980s. Nevertheless, there was intense real-world suspicion during this period that the Soviets were developing MHD-driven attack submarines. As late as 1990, military analysts were convinced that strange “pods” mounted on the tails of new Soviet Victor III-class submarines were MHD thrusters [“
Evidence grows the ‘pod’ is a superconductive drive
,”
Navy News and Undersea Technol.
7
(
11
),
1
2
(
March
19,
1990
)]. Attempts to photograph these pods caused a collision with a U.S. Navy ship, the U.S.S. Drum, in 1981 
[
W. C.
Reed
,
Red November: Inside the Secret U.S.-Soviet Submarine War
(
William Morrow
,
2010
)].
2.
S.
Way
, “
Electromagnetic propulsion for cargo submarines
,”
J. Hydronautics
2
,
49
57
(
1968
).
3.
A.
Iwata
,
Y.
Saji
, and
S.
Sato
, “Construction of Model Ship ST-500 with Superconducting Electromagnetic Thrust System,” in
Proceedings of the 8ᵗʰ International Cryogenic Engineering Conference
,
ICEC
8
, edited by
C.
Rizzuto
(
IPC Science and Technology
,
1980
), pp.
775
784
.
4.
S.
Takezawa
 et al, “
Operation of the thruster for superconducting electromagnetohydrodynamic propulsion ship YAMATO-1
,”
Bull. Marine Eng. Soc. Japan
23
,
46
55
(
1995
); available online at http://www.jime.jp/e/publication/bulletin/english/pdf/mv23n011995p46.pdf, accessed April 25, 2017.
5.
G. I.
Font
and
S. C.
Dudley
, “
Magnetohydrodynamic propulsion for the classroom
,”
Phys. Teach.
42
,
410
417
(
Oct
.
2004
);
G. I.
Font
and
S. C.
Dudley
, “
Magnetohydrodynamic propulsion for the classroom
,”
Phys. Teach.
42
,
517
(
Dec
.
2004
);
6.
O. M.
Phillips
, “The prospects for magneto-hydrodynamic ship propulsion,”
J. Ship Res.
43
61
(
March
1962
).
7.
J. B.
Gilbert
and
T. F.
Lin
, “Studies of MHD propulsion for underwater vehicles and seawater conductivity enhancement,”
Pennsylvania State University Applied Research Laboratory Report AD-A231
623
,
1
114
(
Feb
.
1991
); online at http://www.dtic.mil/dtic/tr/fulltext/u2/a231623.pdf, accessed April 25, 2017.
8.
D.
Normile
, “
Superconductivity goes to sea
,”
Pop. Sci.
241
,
80
85
(
Nov
.
1992
).
9.
K. E.
Tempelmeyer
, “
Electrolysis bubble noise in small-scale tests of a seawater MHD thruster
,”
preprint DTRC-90/30
(
David Taylor Research Center
,
Bethesda, MD
,
Sept
.
1990
); online at http://www.dtic.mil/dtic/tr/fulltext/u2/a227548.pdf, accessed April 25, 2017.
10.
W. H.
Van den Berg
and
K. A.
Miller
, “
Moving water with no moving parts
,”
Phys. Teach.
35
,
531
(
Dec
.
1997
).
11.
J. D.
Wilson
,
A. J.
Buffa
and
B.
Lou
,
College Physics
(
Addison-Wesley
,
2002
), p.
667
.
12.
H.
Semat
and
R.
Katz
,
Physics
(
Rinehart
,
1958
), p.
526
; author edition available online at http://digitalcommons.unl.edu/physicskatz/188/. 
Neutron diffraction experiments reveal that these hydration shells contain, on average, five H2O molecules for Na+ and six for Cl , with “inner” and “outer radii” of about 200 pm and 300 pm respectively, regardless of concentration; see
R.
Mancinelli
 et al., “
Hydration of sodium, potassium, and chloride ions in solution and the concept of structure maker/breaker
,”
J. Phys. Chem. B
111
,
13570
13577
(
2007
).
13.
P. W.
Atkins
,
Physical Chemistry
, 4th ed. (
W. H.
Freeman
,
1990
), p.
755
.
14.
H.
Seo
, “
Measurement of the magnetic susceptibility of liquids
,”
University of Minnesota preprint
(
Spring
2013
); available online at https://sites.google.com/a/umn.edu/mxp/home/2013---spring/s13magneticsusceptibilityliquids, accessed April 25, 2017.
15.
B.
Franzluebbers
, “
Drag coefficients of inclined hollow cylinders: RANS versus LES
,”
Worcester Polytechnic Institute preprint
(
April
2013
); available online at https://web.wpi.edu/Pubs/E-project/Available/E-project-042313-161611/unrestricted/MQP.pdf, accessed April 25, 2017.
16.
C.-W.
Lin
,
S.
Percival
, and
E. H.
Gotimer
, “
Viscous drag calculations for ship hull geometry
,”
preprint, Naval Surface Warfare Center, Carderock Division
,
Bethesda, MD
, Ship Hydrodynamics Department (
1995
); available online at http://www.dtic.mil/get-tr-doc/pdf?AD=ADA323498, accessed April 25, 2017.
17.
M. H.
Sharqawy
,
J. H.
Lienhard
, and
S. M.
Zubair
, “
The thermophysical properties of seawater: A review of existing correlations and data
,”
Desalination and Water Treatment
16
,
354
380
(
2010
); online at http://web.mit.edu/seawater/, accessed April 25, 2017.
18.
G. K.
Batchelor
,
An Introduction to Fluid Dynamics
(
Cambridge University Press
,
2000
), pp.
233
,
335
.
19.
V.
Thomsen
, “
Estimating Reynolds number in the kitchen sink
,”
Phys. Teach.
31
,
410
(
Oct
.
1993
).
20.
See the appendix under the “Supplemental” tab at TPT Online, https://doi.org/10.1119/1.5008337 .
21.
Z. J.
Brophy
, “
The Dawn ion propulsion system
,”
Space Sci. Rev.
163
,
251
261
(
2011
).

Supplementary Material

AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.