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Plasma Thermal Gun
Your PPRO1 plasma gun utilizes the electro thermal
energy obtained from vaporizing a metallic material creating
a pressure wave of sufficient magnitude to cause a
projectile to accelerate to ballistic velocities. The system
shown on our data is a relatively low velocity device within
the building capability of most hobbyists. The project may
be scaled up for serious research with an obvious increase
in high voltage handling and ballistic hazards. The project
requires experience in the handling of high voltage, high-
energy devices.
Construction requires a working High Energy Pulser. It is
shown using energy storage capacitors currently available
on the surplus market. These values may be altered within
limits to allow use of available capacitors that the builder
may have on hand.
Theory of Operation
An energy storage capacitor is charged up from a programmable controlled current source to a selected high
voltage. This capacitor is now switched by a triggered spark gap dumping all the stored energy into and
vaporizing a thin aluminum wire placed inside a small volume explosion chamber. A pressure wave forces a
projectile out the barrel to a high velocity.
This project is suitable for a science class demonstration of the concept if properly supervised with qualified
personal.
Assembly Steps of the Thermal Gun
1. Fabricate barrel and breech plug as shown on fig 5-1 rounding off all edges and inner barrel ridges.
2. Fabricate breech tube as shown Fig 5-2. Note that the mating of the barrel and breech plug are precision-
drilled using fractional bits. Inner diameter should be .007 to .008 over the outer dimensions of barrel and
breech plug to allow for clearance of exploding wire as shown Fig 5-3.
If clearance is to tight, it will be difficult to insert barrel and breech plug without breaking wire.
If clearance is to loose improper contact will occur to exploding wire. Drill a bit at a time to establish proper
fitting action
3. Solder brass retaining washers as shown at points to allow proper gauging of barrel and breech plug
insertion depths into breech tube.
4. Fabricate projectiles from 1/2” pieces of 1/4” plastic, lexan or wooden dowels. Round off end to give a bullet
like shape. This gives a streamlined effect to air resistance. The final assembled gun should look like fig 5-3
and easily fit together for reloading of exploding wire and projectile. You will note the metal barrel and breech
plug are also the feed electrodes connecting to the exploding wire via a sandwiching action. The high powered
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current pulse is now applied to these electrodes generating an explosive super heated plasma vapor producing
a pressure wave forcing the projectile out of the barrel.
The next step is the scheme we used for our lab proto unit fig 5-4. It allows easy disassembly and provides
positive electrical contact to the gun electrode ends. You may have your own ideas to this approach but the
objective must be the same - good electrical contact, easy disassembly and reloading.
For smaller diameter breech plug, use the following sub steps in fabricating:
A. Precisely locate holes and center punch.
B. Drill a 1/8” pilot hole using a drill press.
C. Expand holes to final radius using successively larger drills.
D. Drill 1/16” hole for spring electrode sheet metal screw.
E. Drill (2) 1/16” holes for mounting blocks to base section.
F. Use a band saw to “ruff” cut out sections shown by dashed lines. File for final sizing and finishing.
6. Fabricate and shape spring electrodes as shown. Use pliers and a small vise to get the proper bends as
shown. These pieces must allow snapping in of the gun assembly and provide a positive contact.
7. Fabricate base section fig 5-5 from a piece of 3/4” finished plywood. Sand and varnish for appearance.
Mount components as shown and clamp wires in place using nylon clamps and 1/2” sheet metal screws.
Solder leads of feed wires to spring electrodes.
8. Connect up as shown fig 5-6. Use at least # 16 wire. Leads must be short and direct
9. Obtain a suitable target such as a small pillow. This will prevent projectile from ricocheting all over the
place making it hard to find for reloading
10. Prep gun with exploding wire as shown fig 5-3. Snap into holders and insert projectile to point as shown
It is assumed that the HEP pulser is properly operating and connected as per instructions and has a calibrated
voltmeter and set spark switch. Familiarize yourself with the pulser operation
11. Connect in HEP pulser and energy storage capacitors as shown. NOTE inductor L2 is not used in this
project.
12. Allow charging up to 2000 volts. Test fire unit. Note loud crack and projectile exiting barrel. Increase
voltage in steps of 500 and note increase in velocity. Experiment using different projectiles, targets etc.
DANGER: Verify that energy storage capacitors are fully discharged before touching any part of the gun
assembly. Always direct short at capacitor terminals until ready to operate.
SPECIAL NOTES
The system as shown was tested with (2) 32 mfd 4kv capacitors in parallel for a total energy of 500+ joules.
Projectile velocity was more than 100 m/s. It is suggested to use only one capacitor for the science project
approach.
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Serious experimenters should consider our HEP90 higher energy charger and additional energy storage
capacitors. The gun section must be “beefed” up for any significant increase in energy. Some suggestions
are the following if stored energy is to exceed 1000 joules:
A. Entire assembly must be placed inside of an explosion shield consisting of 1/2” lexan.
B. Retaining washers should be replaced with multiple washers or a sleeve all securely soldered in
place.
C. Breech tube must be sleeved into a secondary sleeve of equal wall thickness. Entire breech
assembly is now inserted into a steel tube or pipe for further reinforcement.
D. Mounting blocks should be reinforced with 1/4” angle aluminum or steel.
E. Mounting base should be fabricated from aluminum or steel.
When attempting to fire larger systems it is important to increase energy in small steps, always
rechecking the system integrity for any damage resulting from prior shots.
You will need the following parts to make this system:
1. Fabricated parts as shown Fig 1-5. These can be purchased thru the factory but will require final fitting.
Raw materials are available thru most hardware stores.
2. The energy storage caps are shown as 32 mfd/4500 volts and are available thru the factory. Other values
obtainable thru surplus sources may be used but we cannot guarantee performance.
3. The HEP3 CHARGER/PULSER/SPARK SWITCH is available thru the factory as a kit or as an assembled
unit. Our HEP9 higher-powered version intended for more serious experimental research is also available. It
can charge up banks of multiple capacitors to 5000 Joules.
DANGE R!! If system uses a PUSH ON / PUSH OFF charging switch, it will automatically recharge
capacitor bank after firing. Basic units use a “push on” switch for the charging switch as charging
always requires switch to be depressed providing safer operation at the cost of convenience.
Red lamp (LA1) indicates system in “on” state”
Green or yellow lamp (LA2) comes on but extinguishes in the charge cycle and comes on when preset
voltage level is reached indicating system is ready to “fire”
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PO Box 716, Amherst, NH 03031
Tel: 603 - 673 - 6493/4730 Fax: 603 - 672 - 5406 Web: http://www.amazing1.com ©2003
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Information Unlimited
EMAIL: riannini@metro2000.net
PO Box 716, Amherst, NH 03031
Tel: 603 - 673 - 6493/4730 Fax: 603 - 672 - 5406 Web: http://www.amazing1.com ©2003
5
Information Unlimited
EMAIL: riannini@metro2000.net
PO Box 716, Amherst, NH 03031
Tel: 603 - 673 - 6493/4730 Fax: 603 - 672 - 5406 Web: http://www.amazing1.com ©2003
6
Information Unlimited
EMAIL: riannini@metro2000.net
PO Box 716, Amherst, NH 03031
Tel: 603 - 673 - 6493/4730 Fax: 603 - 672 - 5406 Web: http://www.amazing1.com ©2003
7
Information Unlimited
EMAIL: riannini@metro2000.net
PO Box 716, Amherst, NH 03031
Tel: 603 - 673 - 6493/4730 Fax: 603 - 672 - 5406 Web: http://www.amazing1.com ©2003
8
Information Unlimited
EMAIL: riannini@metro2000.net
PO Box 716, Amherst, NH 03031
Tel: 603 - 673 - 6493/4730 Fax: 603 - 672 - 5406 Web: http://www.amazing1.com ©2003
9
Fig 5-6 Setupof plasma thermal gun
Attempt to keep all discharge wire as
short as possible to avoid inductance
CAPACITOR STORAGE
SAFETY DISCHARGE PROBE
FUSE CO1
+
+
+
+
A K
High energy pulser from chapter 3-3
F US E 2 A MP
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PO Box 716, Amherst, NH 03031
Tel: 603 - 673 - 6493/4730 Fax: 603 - 672 - 5406 Web: http://www.amazing1.com ©2003
