# Magnetic “Hydrojet”

## Demonstration Kit

### Introduction

In the Tom Clancy novel, The Hunt for Red October (1984), and movie of the same title (1990), a submarine was designed with a unique, silent-running propulsion system. The novel refers to this system as a hydrojet, whereas the movie calls it a magnetohydrodynamic drive, or “caterpillar” drive. Show your students the principles behind this propulsion system and discuss whether it would be powerful enough to push a submarine.

### Concepts

• Electric force
• Electrolysis
• Magnetic force
• Newton’s second and third laws of motion

### Background

The principle behind the revolutionary propulsion system used in The Hunt for Red October is based on the relationship between magnetic fields, electric fields and moving charged particles. A charged particle traveling in a magnetic field will be deflected by the magnetic field in a direction perpendicular to the particle’s initial motion (see Figure 1). The direction of the force that causes the deflection is determined by the “right hand rule.” Point the index finger of your right hand in the direction of motion of the particle, and face the palm in the direction of the magnetic field. Your thumb will point in the direction of the force produced by the magnetic field. The force on negative charges is in the opposite direction to the way the thumb points.

{12672_Background_Figure_1}
The amount of force on the moving charged particle depends on the particle’s speed and the strength of the magnetic field, according to Equation 1.
{12672_Background_Equation_1}

FM = force due to the magnetic field
q = charge on the particle
v = velocity of the charged particle
B = strength of the magnetic field

*Note that FM, v, and B are all vector quantities and the direction of FM is based on the “cross-product” of v and B (i.e., the “right hand rule”).

An electric field also produces a force on a charged particle according to Equation 2. The force produced by the electric field is in the same direction as the electric field for positive charges, and opposite to the electric field for negative charges.
{12672_Background_Equation_2}

FE = force due to the electric field
E = strength of the electric field

The basic principles behind the “magnetohydrodynamic drive” are electrolysis and electrodynamics. A giant electrolysis apparatus uses seawater (tap water) as the electrolytic solution to generate an electric field and to produce ions (charged particles). Strong magnets are used to deflect the moving charged particles out the back of the submarine, which generates thrust according to Newton’s third law of motion (action–reaction). See Figure 2 for a depiction of the forces and the motion of the charged particles. The magnitude and the direction of the force due to the electric field are constant, while the magnitude of the magnetic force is constant but its direction depends on the direction the particle is traveling (according to the “right-hand rule”). Once the charged particles are deflected due to the magnetic field, the particles remain on a path perpendicular to the electric field because the forces due to the electric field and magnetic field are now balanced. The charged particles must continue to move in order for the forces to remain balanced. If the charged particles stop moving (v = 0), then the magnetic field will no longer act on the charged particles.
{12672_Background_Figure_2}
This propulsion system created by the behavior of ions in an electric and magnetic field has advantages and disadvantages. Electrolysis generates oxygen and hydrogen gases which could be used to sustain life support and to run fuel cells, respectively. This unique submarine design also does not require the need to carry fuel for propulsion because it would use the surrounding water. However, the design would still require a nuclear reactor to generate enough electricity to produce the strong electric fields and electromagnets needed to create and deflect the ions (and water), respectively. As far as the submarine being “silent running” as the novel and movie claim, that would depend greatly on the power systems used to generate the high voltage and electromagnets. These systems would probably generate a great deal of “humming,” and if the oxygen and hydrogen gas bubbles are not collected, the resulting bubbles would create a noisy environment.

### Materials

Food coloring*
Batteries, 9-V, 5
Battery snap-on tab, female*
Battery snap-on tab, male*
Brass pins*†
Connector cord, with alligator clips, black*
Connector cord, with alligator clips, red*
Document camera (optional)
Electrophoresis chamber with power cords*
Electrophoresis chamber with two pre-drilled holes*†
Electrophoresis chamber cover (lid)*†
Hammer, small†
Neodymium magnets, 3*
Silicone rubber aquarium sealant, clear†
Tape, transparent
Water, tap
*Materials included in kit.
Electrophoresis chamber assembly.

### Safety Precautions

Electrical Hazard: Treat these units like any other electrical source—very carefully! Be sure to read and follow all electrical hazards associated with the electrophoresis apparatus and power supply used in this demonstration. Be sure all connecting wires, terminals and work surfaces are dry before using the electrophoresis units. Match the lead colors: red (anode) to red and black (cathode) to black. To view the moving dye, the lid of the electrophoresis chamber must remain off. Connect the power supply directly to the electrodes of the chamber. Do not touch the liquid or any of the cord connections when the unit is connected to the batteries. Wear safety glasses. Handle the food dye carefully. It will stain skin and clothing. Uncured silicone sealant causes irritation on contact. Avoid contact with eyes and skin. Flush eyes with water if contact occurs and call a physician. Remove any sealant from skin with dry cloth or paper towel and flush with water. Wash hands thoroughly with soap and water before leaving the laboratory.

### Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The resulting food dye solution may be disposed of down the drain with excess water according to Flinn Suggested Disposal Method #26b.

### Prelab Preparation

Electrophoresis Chamber for Magnetic “Hydrojet” Assembly

1. Check to be sure you have all the necessary materials.
2. Squeeze a small amount of silicone sealant compound inside the plastic chamber behind one of the pre-drilled holes in the side of the chamber. Squeeze additional silicone sealant in a thin line straight across the bottom of the chamber from the hole to the opposite side wall (see Figure 3).
{12672_PreLab_Figure_3_Assembled electrophoresis chamber}
3. Locate the predrilled hole in one of the copper electrodes (in the end of the electrode). With the hole in the electrode facing the hole in the chamber, gently lay the electrode in the bead of silicone sealant at the bottom of the chamber.
4. Take one of the brass pins and insert the pin (point first) from the outside through the hole in the chamber, through the silicone sealant, and into the hole in the end of the electrode.
5. While holding the electrode in place, gently tap the brass pin into the electrode with a small hammer. (Just enough to make sure you have a good contact.)
6. Gently press the electrode down into the silicone sealant. It will squish out the sides and around the electrode. Examine to be sure the silicone sealant has sealed completely around the brass pin at the hole. The chamber must be watertight. If not completely sealed, apply more silicone sealant.
7. Repeat steps 2–6 using the other copper electrode, brass pin and the other hole in the base of the chamber.
8. When this is complete, the two copper electrodes should be flat in the bottom of the chamber, imbedded in silicone sealant, parallel to each other, and sealed around their attached pins.
9. The silicone sealant will take 24 hours to cure and dry. Set the entire apparatus in a place where it will not be disturbed during the 24-hour period. Do not cover the apparatus during this 24-hour period.
10. Your chamber is now assembled. Do not use the electrophoresis chamber until the silicone sealant has cured (24 hours).

### Procedure

1. Obtain the assembled electrophoresis chamber, tape and three neodymium magnets.
2. Tape the neodymium magnets to the outside bottom of the electrophoresis chamber along the centerline, perpendicular to the direction the ions will travel (see Figure 4). Make sure the polarity of the magnets point in the same direction (i.e., the “north” poles of the magnets all point down).
{12672_Procedure_Figure_4}
3. Fill the electrophoresis chamber about halfway with tap water (do not used distilled or deionized water).
4. Stack the five 9-V batteries together as shown in Figure 5. Attach the appropriate battery snap-on tabs to the battery terminals.
{12672_Procedure_Figure_5}
5. Add a drop of food coloring near one of the magnets.
6. (Optional) Set up a Video Flex camera to conveniently display the demonstration on a TV or computer screen.
7. With the connector cords, connect the electrophoresis chamber directly to the snap-on tabs on the stack of batteries (do not place the lid on the electrophoresis chamber).
8. Have students observe the motion of the dye and record their observations in the worksheet.
9. Repeat the demonstration by adding more dye, a different color dye, reversing the polarity of the electric field (reversing the connecting leads) or by disconnecting the chamber from the power supply, emptying the chamber and filling with fresh tap water. Discuss the observations with students (what do students observe—bubbles, dye motion, swirling, etc.).

### Student Worksheet PDF

12672_Student1.pdf

### Teacher Tips

• Neodymium magnets and Mega-Magnets are strong and create very visible currents. Any strong magnets will work, however. Handle these magnets carefully. They can quickly snap together and pinch skin. They are also fragile and may shatter, crack or chip if dropped on the ground. They are difficult to pull apart. It is often better to slide them apart.
• (Optional) Perform a “control” experiment without the magnets attached to the bottom before creating the “hydrojet.” The dye will travel slowly toward the electrodes of the electrophoresis chamber.
• Change the orientation of the magnets to see how the ion currents are affected. Standing the cylindrical neodymium magnet on its edge generates a swirling ion current that appears to produce ion “containment.” For advanced classes, discuss fusion reactor designs and the possibilities of plasma containment.
• Keep neodymium magnets away from computer disks or other magnetic strips such as credit cards. They will quickly erase the magnetized data.

### Science & Engineering Practices

Developing and using models
Planning and carrying out investigations
Analyzing and interpreting data
Using mathematics and computational thinking
Constructing explanations and designing solutions

### Disciplinary Core Ideas

MS-PS2.A: Forces and Motion
MS-PS2.B: Types of Interactions
MS-ETS1.A: Defining and Delimiting Engineering Problems
HS-PS2.A: Forces and Motion

### Crosscutting Concepts

Patterns
Cause and effect
Systems and system models
Energy and matter
Structure and function
Stability and change

### Performance Expectations

MS-PS2-2: Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object
MS-ESS2-5: Collect data to provide evidence for how the motions and complex interactions of air masses results in changes in weather conditions.
MS-ETS1-1: Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.
HS-PS2-1: Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration.

### Sample Data

Observations

Sketch a diagram of the initial setup, including the location of the drop of food dye.

Sketch a diagram of the final result, including the direction of the motion of the dye, and explain what occurred.

1. Which of Newton’s three laws of motion provides the basis for a rocket propulsion-type engine. Define the law(s) chosen.

A rocket propulsion-type engine relies on Newton’s third law of motion, or for every action there is an equal and opposite reaction. It also relies on Newton’s second law of motion—a force causes a mass to accelerate.

2. Write the balanced chemical equation for the electrophoresis of water.

2H2O(l) → 2H2(g) + O2(g)

3. A negatively charged electron is traveling to the right, and a magnetic field is pointing towards the top of the page. Which direction does the particle rotate once it encounters the magnetic field?

The particle is forced down, into the page.

4. Do you believe this magnetohydrodynamic system could be used to push a submarine? Why or why not?

Student answers will vary. Most will agree that this type of system could be used as a propulsion system for a submarine, if it could generate enough power.

### References

Special thanks to John Fedors for the design and testing of this electrophoresis chamber.

Next Generation Science Standards and NGSS are registered trademarks of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.