HOMEMADE STEAM ROCKETS
Several Models You Can Make
Adjustable Impulse, No Pollution and Cheap to Launch
A rocket nozzle is a complete thermodynamic engine. Random-direction
molecular motion due to extreme heat is changed into one-direction molecular
motion out the nozzle. Just like the random-motion explosion in your car's
engine pushes down on the piston and exploding gunpowder pushes a bullet out.
In these steam rockets, confined water is heated from 467 F to 545 F, in
which case the corresponding pressure is from 500 PSI to 1000 PSI.
When launched, the super-heated water enters the nozzle, not like gases in
pyrotechnic rockets. The water accelerates in the inlet cone, flash-boils in
the throat and then steam (gas) explodes out the exit cone. That action puts
a reaction force on the exit cone and accelerates the rocket's mass in the
opposite direction.
The Thunderbolt steam rocket motors made by Bob Truax (patent 3,029,704)
for drag racers put out 4,000 lb. of thrust for four seconds. Art Arfons
went 260 MPH in the 1/4-mile. (Do not try this at home.) But he hit the
emergency release in the time trap or else he could have gone even faster!
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The first full-pressure test of the basic plan.
When pressure reached 500 PSI, one cord pulled the burner away. To launch
the motor, another cord pulled the holddown yoke support away.
The 16 oz. paintball CO2 tank test-launched.
The first in-flight video frame.
The next frame 1/30 second later.
The actual motor is 9.5 in. long or .79 ft. and the frame image is 7/32".
It has gone 42/32" in 1/30 of a second or 4.746 ft. in 1/30 sec. That's 142
ft/s, or 97 MPH, in that interval.
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SCALDED DOG
Real rocket scientists, not just your average T-shirt-wearing variety, can
make a steam rocket. Only two small, simple items require (minimal) machining.
A paintball CO2 tank fill valve.
Paintball CO2 tanks make good motors. The thread is 5/8" x 18 TPI. A chain
Vise-Grip is used to hold the tank while removing the valve. The spring
retainer is removed with a 3/16" Allen wrench and the burst disk is removed
with a 7/16" wrench.
Sketch of the steam rocket nozzle core.
A 5/8" x 18 bolt is used to make the nozzle core. It requires a lathe to
make, or have a machine shop do it. Cut the bolt head off so the bolt shank
fits in the lathe. Cut again at the threads to match the threads inside the
tank, plus what will be the straight part (long enough to chuck in a lathe).
The throat must be dead-center-drilled 7/16" in a lathe. The straight part
needs to be turned to 9/16" outside diameter in a lathe.
The rest can be done by the builder. Saw the bolt off where the shank meets
the threads. Countersink the inlet (threaded) end. Some of the straight part
will be cut off and pipe-reamed after the hold plate is silver-soldered on.
The nozzle parts before assembly.
Sketch of a hold plate.
After silver-soldering the hold plate to the nozzle core, form the sheet
metal exit cone over a pipe reamer and silver-solder the overlapped seam.
Exit cone pattern.
Put a 5/8"-18 nut on the nozzle core and clamp the nut in Vise-Grips. Use a
clamp to anchor the Vise-Grips to the drill press table so the nozzle is dead
center. Put the exit cone loose over the straight part of the core. Put a
pipe reamer in the drill press and ream so that the nozzle core's taper
matches the exit cone's taper.
Silver-solder the nozzle core to the exit cone while both are aligned in the
drill press. (Have someone hold the feed down.)
This exit cone was shaped over the pipe reamer.
A 1/8" lip was left on both sides of the cone so it could be held closed
by sheet metal Vise Grips while being silver-soldered.
The TIG-welded nozzle used in SCALDED DOG.
This hold plate is 1/8" (10 ga.) steel and required reinforcing.
The silver-soldered nozzle used in SCALDED CAT.
This has a proper 3/16" hold plate. The 24-ga. stainless steel exit cone
was overlapped at the seam 1/8" and silver-soldered.
SCALDED DOG
The LED is on showing fuse ignitor continuity. In front of the LED is the
fuse ignition switch with the pull clip on it, but without the pull wire. The
chute cable, connected to the motor hook at bottom left, goes through the
bulkhead, out the side, under the nose cone and onto the chute bungee cord.
The chute piston.
Made from a cut-down baking pan that was shaped over the sauce warmer. It
is inserted cupped down and the sides are flared out to fit the body tube.
The nozzle plug without the O-ring.
The nozzle plug is the other machined part. It is a brass tire valve
fitting that had male 3/8" pipe threads. Where the threads were has been
machined to 7/16" wide and grooved 1/16" for the O-ring. It is drilled through
1/4" for the copper tubing, which will be silver-soldered in.
The nozzle plug, copper tubing and pipe stand.
The 3/8" pipe 4" long is in a pipe flange. The 1/4" copper pressure-gauge
line comes out a slot in the pipe.
A no-welding-required holddown.
Brass is costly, but the holddown tee can be galvanized.
The bare-bones steam-rocket base.
The torch burner swings over to the motor and away from it easily. A 4",
600 PSI pressure gauge is on the right. 1/4" copper tubing goes from the
nozzle plug to the pressure gauge compression ell fitting.
The motor hold-down yoke.
It is made of 3/16" x 3/4" x 16" steel. The yoke holds the motor down until
the bolt is pulled away. At 500 PSI, 75 lb. of hold-down force is required.
The battery/capacitor chute-delay section.
This is an ignition system first installed inside the rocket. It was later
moved out onto the base to reduce weight. A full toothpick is propping open
the launch switch. In use it would be a short piece. The LED is showing that
the ignitor has continuity. In use the ignitor would be on top of the disk.
The upper (+) ignitor hole is insulated. The ignitor clips are kept back, out
of the way of black-powder fouling.
The black-powder pouch, delay fuse and ignitor.
The chute charge is just under 1/4 tsp of black powder. The head of the
ignitor is on the fuse powder. The tape will hold it and also insulate the
bare ignitor wires from the metal disk. 2 & 1/2" of pyro fuse (7 sec.)
works well, or 2 & 1/4" of TNT fuse or 2 & 3/4" of Phantom fuse.
Wiring diagram of the fuse-ignition system.
The LED is the ultrabright type which can be seen from launch control.
Chute cable and bungee.
Bike cable with ferrules is used in several places. The ends of the bungee
are secured with nylon ties. But steel pig rings work better.
"All systems are go..."
The cords are laid out properly, the torch is on, the pressure is starting
to build up and there are no leaks. So "All systems are go..."
"Houston, we have lift-... What the...?"
"Hey guys. Ya ain't gonna believe this..."
Steam rockets don't do weenie liftoffs, they EXPLODEoff! In the first
two video frames printed out full page, the rocket has gone .413". At a scale
of 5/16 (.3125) in. image size equals 3 & 2/3 feet actual rocket length, in
1/30 second it has gone 4.4 ft. That's 132 ft in one second, or 90 MPH.
SPECIFICATIONS: Maximum rocket weight: 5 lb.
Volume (20-oz. tank): 3 cups
Empty wt.: 3.5 lb
Chute size: 54"
Impulse: 67.5 lb-sec (more than H)
Specific impulse: 45 sec
Nozzle throat: 7/16"
Exit nozzle dia.: 1 & 3/8"
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CHUTE CHARGES: We give the chute eject charges in teaspoons, since that is the
easy way to measure it. But be aware that one "1/4 tsp" held
12.3 grains of black powder and another held 11.1 grains. And
don't think you should err on the side of caution. That will
only burn holes in your chute unnecessarily.
Stuff to test chute charges.
This is a 3" mailing tube used as a mortar, a known weight, two cans that
can be cut down to fit nicely into the tube and one bean can that has been cut
down to form a piston. It goes in open-end-down over the chute charge.
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SCALDED CAT
SCALDED CAT
The nozzle has the same dimensions as SCALDED DOG and the motor hook for it
is similar. We put the fuse ignition circuit out on the base to keep the
flying weight down. The chute charge fuse comes out the side of the rocket.
The ignitor head is taped squarely over the fuse powder. The fuse was cut at
a shallow angle to better ensure that the ignitor lights the fuse powder.
The fuse with ignitor in place.
The tape will be folded over on top. You can also use black powder over
the ignitor as a smoke puff charge to see positively that the fuse was lit.
Ignitor with a smoke charge.
A bit over 1/8 teaspoon of Goex FFFFg black powder works well for the chute
deployment charge. A chute piston was formed over the bottom of a beer bottle.
The rest of the launch procedure is the same as for SCALDED DOG.
The base for SCALDED CAT.
Scalded Cat has a 16-oz. paintball tank.
SPECIFICATIONS: Maximum rocket weight: 3 lb.
Water (16-oz. CO2 tank): 2 cups
Min. wt.: 2 lb
Chute size: 36"
Impulse: 45 lb-sec (H)
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MR. ROCKET
In an attempt to make launching steam rockets as easy as brewing your
morning coffee in your MR. COFFEE, MR. ROCKET was designed. The rocket stays
seated on the nozzle plug while the tank is being heated by the torch.
MR. ROCKET
This uses a 16-oz. paintball tank. The upper section was later shortened.
Sketch of MR. ROCKET.
The steel rods securing the rocket motor to the upper chute section are
1/8" music wire through the bulkhead with the top 1/2" bent over and held by
J-bolts. Sheet metal strips are silver-soldered to the music wire rods for
fin mounts. The 1/8" model airplane plywood fins are bolted to the mounts.
The lower part of MR. ROCKET.
At the top is the bulkhead that will be epoxied into the 3" mailing tube.
The guide rod was moved.
The usual location of the guide rod for SCALDED CAT has been changed for
MR. ROCKET (arrow), which has three fins. The chute cable is inside, runs
down one side of the body tube and is secured below the bulkhead. The chute
piston is the same as in SCALDED CAT.
The chute delay fuse is lit first when the launch cord is pulled (the
continuity LED goes out) and then the holddown fork is pulled away to launch
the rocket. A bit of black powder can also be over the fuse ignitor to make a
visible smoke puff. The chute charge is 1/8 tsp of FFFFg black powder.
MR. ROCKET ready to percolate.
The fourth video frame.
MR. ROCKET is 3 feet long and shows up as 5/8" (20/32") in the video frames
printed out to 8 x 10 size. So each 1/32" equals .15 feet. From the video,
it is going 64 MPH from frame 1049 to 1050, 132 MPH during the next two frames
and 160 MPH during the next two frames.
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SOLDERING
Normal solder melts at 465 F and CANNOT be used for the nozzle plug
tubing or to make the nozzle. Neither can "silver-bearing" solder. Use ONLY
45% silver silver-braze rods for all metal joining required here. It melts at
1205 F and is extremely strong, used to make exotic racing bicycles.
Alpha Fry 45% silver-braze from Ace Hardware, $12
This alloy is excellent. The metal must first be sanded bare, solvent-
cleaned and fluxed. Use a propane or MAPP gas torch to heat the metal to
where the solder will flow, look shiny and be drawn into the joint. REMOVE
the torch as soon as it flows! Clean off the hardened flux with hot water.
Steel-wool and wire-brush the joint to check the bond. If necessary, re-flux,
reheat and add more silver-solder until it's right. Harris Safety-Silv45 is
similar, found in welding-supply stores. Use the Harris Safety-Silv flux made
for it. It can be moistened with water when it gets too dry.
O-RINGS: The O-rings used MUST be silicone. The size to seal the nozzle into
the paintball CO2 tank is Dash 016. It can be left in. The size on
the 7/16" nozzle plug is Dash 011. It will be blasted off after the
launch. www.msdirect.com, stock #06840169 and #06840110
PRESSURE GAUGE: Northern Tool #53689 (4", 0-600 PSI)
COST PER LAUNCH: $1.30. Estes igniter $.83, Goex black powder $.02, fuse
$.03 per inch, nozzle plug O-ring $.06, baking tin chute
protector $.32. Add the cost of the torch gas used.
FUSE BURN RATES
Pyro fuse burns at a rate of 2 & 3/4 seconds per inch. Phantom Fireworks
Chinese fuse burns at 2 & 1/2 seconds per inch. TNT Fireworks Chinese fuse
burns at of 3 seconds per sec. The length to use is the delay required
divided by the burn rate. TEST any fuse that you intend to rely on!
MAPP gas burns at 2100 F at a distance of 3/4" from the end of the burner.
Propane burns at 1900 F at that distance from the end of the burner.
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BOILING OVER
This rocket uses an aluminum tank from a 15-lb. CO2 fire extinguisher for
the motor. A 500,000 Btu propane torch heats the exposed tank. The guide rod
and chute anchor cable are opposite the 2000 F burner flame.
The propane torch in its stand.
A knob under the handle adjusts the burner flame. The adjuster is pulled
off the handle by a cord to shut the torch off after full pressure is reached.
The nozzle parts.
The 1/4" steel holddown plate had mill scale, so the O-ring seat was milled.
The 16-ga. exit cone is TIG-welded. It could also be silver-soldered, but
first grind off the zinc galvanizing at the joint and overlap the seam 1/8".
The nozzle has a thread of 1 & 1/8" x 12 TPI, a 3/4" throat and an exit cone
diameter of 2.5".
The first nozzle-and-fins unit.
This nozzle plus fins mount screws into the CO2 tank. The fins are bolted
to 1/8" steel mounts that are welded to 3/8" square steel bars welded to the
hold plate and to a 1/8" x 1" band around the tank.
The rocket body is clamped to the bottom of the motor after the rocket fuel
is in, it is seated on the launch base and then both are turned upright.
The launch base.
At 500 PSI, the hold-down force required is 221 lbs minus the 39 lbs dead
weight. The chute anchor cable is outside the rocket body and motor, opposite
the torch flame, secured down at the 1/4" hold plate.
The chute cable and drogue cord at the top.
The chute cable goes inside alongside the nose cone and connects to the
main chute inside. The drogue cord is outside, wound around the nose cone.
The red bow is a reminder to turn the altimeter on. A drogue in the nose cone
is deployed by the altimeter right after apogee. The main chute is deployed
at 500 feet. The chute charge is 1/2 tsp FFFFg black powder.
The altimeter in the nose cone.
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A DIRE WARNING ABOUT ALTIMETER CHUTE RELEASE USED WITH STEAM ROCKETS!
We had one good and one bad flight with this Co-Pilot V-2.0 altimeter from
Public Missiles. An email to Public Missiles explaining the faulty deployment
situation was never answered. An email to Jim Amos at Missleworks, the company
that makes the altimeter, resulted in two replies which gave MANY more VERY
DIRE warnings than the ONE warning supplied by Public Missiles!
All the altimeter makers hide behind the "sonic/subsonic transition"/
"Bernoulli-induced pressure"/"Mach" excuses to absolve themselves from their
responsibility. They can get away with it only because their devices are
presumed to be used with kit rockets using off-the-shelf motors and so the
flights can be simulated using public software. Then YOU are to set the delay
according to those software tables. BUYER BEWARE! We had to go back to our
old standby of pyro fuse delay. (It always works!)
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Modified rappel brake shock absorber.
The large eye has been cut off. A 15 pound friction force is put on the 6
ft. long rope on the anchor cable to prevent a too-hard jolt or bungee cord
rebound. The chute shrouds will be where the spring scale hook is shown.
The nozzle plug O-ring is Dash 016, the same one used for the paintball
CO2 tanks. The tank seal O-ring is Dash 216, MSC stock #06842165.
Various exotic rocket fuels were tested.
BOILING OVER takes 2 gallons of pure mountain spring rocket fuel.
BOILING OVER ready for its maiden flight.
One cord pulls the flame adjuster off the torch handle, shutting off the
burner, and then pulls the burner back so that the fin clears the wind guard.
A separate cord releases the hold fork to launch the rocket. The pressure is
monitored by a shooter's 20X spotting scope. The apogee on this the first
flight was 790 feet.
BOILING OVER under the chute.
The apogee was much less than expected according to our book on steam
rockets and so no drogue was used after this first trial.
BOILING OVER with the no-drogue nose cone.
The wind guard.
Because the torch must be 10" from the motor, a wind guard is essential.
BOILING OVER all set to go.
This is our present launch site, the Dan Griffin Sod Farm on Route 27 south
of South Bay, Florida at mile 66.
SPECIFICATIONS: Maximum rocket weight: 39 lb.
Water (15-lb. CO2 extinguisher): 2 gal. (16 lbs)
Min. wt.: 24 lb
Chute size: 8 ft.
Nozzle throat: 3/4"
Exit nozzle diameter: 2.5"
Impulse: 720 lb-sec (L)
Thrust duration: .93 sec (28 frames) at 500 PSI
One frame from the video.
BOILING OVER launch (don't blink).
Within the span of 6 frames, the rocket has gone 3 & 1/4 lengths of 4 feet
each (13 feet) in 5/30ths of a second. That is 78 feet per second or 53 MPH.
This second flight was only to 712 feet, due to a premature chute release.
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BOILING MAD
After setting up BOILING OVER several times, we made the process simpler.
The motor tank, nozzle and fins are the same, but the steel ring around the
tank was moved lower, out of the airflow.
The new fin support ring.
The black "hook" is for the guide rod. The guide rod is now at a right
angle from the motor to launch control so everything can be done from there.
The new nose cone circuitry.
The nose cone itself is essentially the same except no altimeter. A 9-volt
battery with a parallel 4700 mFd cap is used to burn the delay-fuse ignitor.
The delay fuse then lights the chute-eject charge. The LED is on indicating
ignitor continuity.
The chute cable and the leads to the chute charge are outside the body
for display here, but they will go inside.
A paper clip holds a switch open and is pulled out during the explode-off.
The closed switch then sends power to the delay-fuse ignitor.
The nose cone and heat cloth.
The nose cone cable goes through the heat cloth grommets and is snap-linked
to the END of the friction rope.
The chute cable exits the body tube, goes through the upper guide rod guide
loop and is secured into a chain link down on the hold plate.
A lighter rope-friction clamp.
The tension should be about 15 pounds when used with a 6 foot long rope.
The rope, clamp, link and chute ready to go inside.
The body tube being packed.
The upper guide rod loop is lower left. The heat cloth is ready to receive
the rope, friction clamp, chain link and the chute. No drogue is used because
the apogee was much less than a book about steam rockets led us to believe it
would be. The weights of BOILING OVER and BOILING MAD are the same, 24 pounds
empty. The motor/nozzle/fins unit alone weighs 20 pounds.
The midsection where the halves join.
The chute cable is held close to the motor, out of the high heat of the
weed-burner torch.
An Estes ignitor on the 4 & 1/2" pyro fuse delay.
No extra black powder is needed as long as the ignitor tip is squarely on
the black powder at the center of the fuse. The fuse was cut at an angle.
The chute charge is 1/2 tsp of FFFFg black powder.
Using a Phantom fuse ignitor for the delay fuse.
A small bit of black powder over the ignitor coil (not shown here) MUST be
used so that the flare-up of the coil will positively light the pyro fuse. Or
you can clamp Phantom remote electric fuse lighters onto their green fuse.
BOILING MAD ready for explode-off.
The altimeter is in the white part. The delay-fuse-lighting battery and
switch is in the blue part. The pressure went over 700 PSI unexpectedly and
the altitude was 1546 feet. With 500 PSI in BOILING OVER, the altitude was
only 790 feet. So the improvement in total impulse increases at an increasing
rate as opposed to a decreasing rate as our book about steam rockets stated.
The last two video frames indicate that the speed was 63 MPH.
BOILING MAD launch.
The landing.
The flight went perfectly. It arcs to the left here but wind pushes it to
vertical until out of sight. Chute deployment, as well as three people could
tell by the sound, was just after apogee.
Printer-friendly BOILING MAD version.
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THE RED DRAGON fire extinguisher tank rocket.
THE BLACK SKY paintball tank rocket.
A word about small camp stove and torch tanks used for steam rockets. The
highest expected pressure for these is 240 PSI, but the burst pressure is 960
PSI. So depending on the gauge you have, go over 250 but stay under 750 PSI.
THE GREEN MONSTER propane tank rocket.
THE LEPRECHAUN propane tank rocket.
THE YELLOW JACKET Mapp gas tank rocket.
Measuring rocket speed from a video.
An electronic chute-ejection timer.
Locating downed rockets.
See the HOMEMADE FIREWORKS page for making black powder from local materials.
Stainless water bottle steam rocket boiler.
This bottle has a brass plate silver-brazed to it and then a plumbing
fitting drilled 1/2" was silver-brazed to the plate. We pressure-tested it
just to see how much it would take, so it has no exit cone. It went as high
as 600 PSI and didn't fail, which was as high as the pressure gauge read.
Stainless water bottle boiler being tested.
A very light steam rocket with this boiler would have the highest
acceleration possible off the base. And after all the steam was out, the
rocket would weigh next to nothing and so could just tumble down. But paint
it some very visible color and keep a sharp eye on it!