Originally published in Volume 45 Issue 11 of Artificial Organs, 30 May 2021
Author Tom Clancy popularized the term magnetohydrodynamics in his 1984 techno-thriller novel, The Hunt for Red October.1–3 The Red October is a Soviet Typhoon Class stealth nuclear submarine that is propelled by a magnetohydrodynamic “caterpillar drive” silent engine (Figure 1). Years later, in 2003 in a series of novels, author Clive Cussler described the Oregon, a ship also propelled by a MHD drive.4
The term magnetohydrodynamics, or MHD, comes from the Greek. Magneto, means magnetic (M), hydro (H), means water, and dynamics (D), means movement. MHD is the study of how electrically conducting fluids behave in a magnetic field. Examples of electrically conducting fluids include liquid metals, salt water, and electrolyte rich blood.5 An MHD drive or accelerator has no moving parts and is a method for propelling vehicles using only electric and magnetic fields. The fluid is directed rearward which accelerates the vehicle forward.
In the 1990, the film version of The Hunt for Red October,3 the nearly undetectable “caterpillar silent drive”, is intended to achieve stealth in submarine warfare. The movies so-called MHD caterpillar drive functions like a jetboat. A jetboat, unlike a motorboat that uses a noisy propeller, draws water through an intake into a pump. The pump propels the craft by jetting out the water through a nozzle at the stern. In fact, the jetting of the water creates cavitation which is both noisy and detectable.
Perhaps author Clancy’s interest in MHD and its usage has an historical basis as magnetism has fascinated both lay and scientist groups for centuries.
In 1832, Michael Faraday conducted experiments using the brackish water from the river Thames flowing through the Earth’s magnetic field.6, 7 The Swedish physicist, Hannes Alfvén, who introduced the term magnetohydrodynamics, received the Nobel Prize in Physics in 1970 for fundamental work and discoveries in “magnetohydrodynamics”.8
In 1959, Richard Rosa9, 10 successfully developed an MHD power generator. In the 1960s, based on the Rosa generator’s potential to produce cheap power, MHD programs were initiated in many countries worldwide, including the United States and Soviet Union.
The Argonne National Laboratory, Lemont, IL., a U.S. DOE multidisciplinary science and engineering research center, was tasked with magnet design, program coordination, and cooperative efforts with the then, Soviet Union. Cooperation on MHD research was part of a broader Soviet-American scientific cooperation effort which ranged from heart transplant research and bird-banding, to earthquake forecasting and environmental protection.13–15
A major effort of this U.S. and Soviets “cold war” agreement was to develop an MHD submarine propulsion system15; hence, the fictional, Red October. This US/USSR collaborative effort included the herculean effort of flying the 40 plus ton 20 megawatt (MW), Argonne magnet to the USSR for collaborative studies.16 This magnet, the largest of its type in the world, could generate a magnetic field 250 000 times greater than earths.
During the 1980s, one of our research efforts was to fabricate a “gentle” blood pump. A small, portable pump with few, or no moving parts, that could effectively, propel blood. We had a number of projects that could benefit from a miniaturized, portable pump. These included our percutaneous cardiopulmonary bypass system,17, 18 a disposable heart-lung machine,19 and hemodynamic support without an oxygenator.20, 21
Ken Thornton, my coauthor, suggested we design and build a magnetohydrodynamic (MHD) blood pump. He noted that MHD accelerators can propel electrolyte rich fluids. For example, MHD accelerators or drives, are used to pump liquid sodium through heat exchanger cooling pipes that surround fast nuclear reactor tanks.22 In addition, MHD accelerators were being researched to substitute as boat engines by magnetically propelling sea water.23–25
As all research begins in the library, we investigated the transfer of MHD technology26 into a medical device. We built and tested an MHD accelerator, or “pump” (Figure 2A,B). We tested our MHD pump in a mock circulation loop both filled with normal saline and expired blood bank blood. Our mock circulation loops blood pressure was set to 50-mm Hg systolic and a cardiac output of 2 L/M. We never attempted to start the mock circulation from the resting state of zero flow and blood pressure. For both saline and blood, our MHD pump accelerated blood pressure the mock circulation flow from a “shock level” of 2L/M, a more physiological level of 4L/M (Figure 3). With this early success we designed a comprehensive protocol to study the effects of MHD on blood. These included, but were not limited to, heating effects of MHD on blood, hemolysis and red cell viability, coagulation, electrolyte injury, etc. Unfortunately, due to lack of funding we discontinued our MHD research, but published our initial results27
Figure 3 depicts our shoe-box sized MHD pump integrated into a mock circulation loop. Our MHD magnet was powered directly from a 120-volt wall plug.
When the scientists at the Argonne National Laboratory, who had been actively researching an MHD propulsion system28 learned of our MHD blood pump project, they invited us to meet with them. Physical access to Argonne National Laboratory is by invitation only but following a background check, we were flown to Lemont, IL., the location of the impressive Argonne National Laboratory campus. We were shown their magnet and huge saltwater tank. We were told that they had to coordinate the activation of their magnet with the O’Hare airport flight controllers as the magnet was so powerful it could interfere with an aircraft flying nearby! During the nearly all day meeting, the Argonne scientists revealed that despite of all of efforts, they were unable to adapt their MHD accelerator system to effectively pump salt water and asked how we achieved 4 L/M. During the discussion, I indicated that our system was a closed loop one, not an open tank. In addition, our MHD blood pump was designed to augment existing flow from a mock “shock” state and not initiate flow from a static state, as was Argonne’s goal. We emphasized that our mock circulation “shock model” was “jump started” as it was flowing at 2L/M prior to activating our MHD accelerator. Our MHD accelerator did not attempt initiate flow from a static state, but rather augmented or increased flow from a “shock” level to normal.
Though the Red October story1–3 is fictional, the MHD5, 10, 16 propulsion system is not. An example is the MHD experimental Japanese ship, the Yamato. The Yamato-1 is an MHD ship built in the early 1990s and could travel at 15 km/h, or 8 knots. It has two MHD thrusters, which have no moving parts, and was first successfully operated in Kobe harbor in June 1992.
Few large-scale working prototypes have been built, as marine MHD propulsion remains impractical due to its low efficiency, limited conductivity of sea water, the cost, size, and weight technological of the electromagnets, and the power available to feed them.
Development of non-medical MHD propulsion systems actively continues with active interests in developing MHD plasma propulsion engines for space travel29.
Advances in the biomedical applications of MHD research are ongoing.
These include laser beam scanning, nano-particle manipulation, imaging contrast enhancement, and targeted drug delivery. As the field of biomedical MHD usage continues to grow, advances towards micro-scale transitions will continue to be clinically driven.30 MHD effect is a physical phenomenon where an external magnetic field can set in motion a conducting fluid, such a blood. The authors are not aware of any ongoing research that uses MHD to pump blood. Our early MHD experiments verifies that potential but requires further aggressive research.