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, unlike gases in
chemical rockets.  The water accelerates in the inlet cone, flash-boils in
the throat (sonic speed) and then steam (gas) expands to supersonic speeds in
the exit cone.  As the steam expands, it hits the exit cone and is forced
straight down.  That action puts a reaction force on the exit cone which
accelerates the rocket in the opposite direction.  Just like squeezing a wet
watermelon seed between your fingers.
   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.  But he hit the emergency release in the time
trap or he would have gone even faster!
   The Snake River rocket attempt by Evel Knievel aboard the Sky Cycle was a
steam rocket.  But the flap over the chute was sucked open by the high speed
and the chute deployed  prematurely.  Another attempt will be made aboard the
Skycycle X-2 which will have the water at 487F and 500 PSI and the thrust will
be 6,000 lbs.
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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 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 lever 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 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 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 a level 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. A 2 & 1/2" fuse equals 7 seconds.
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.
"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 (1/30 sec.) printed out full page, the rocket has gone .413".
At a scale of 5/16 (.3125) in. image size equals 3 & 2/3 feet rocket length.
So in 1/30 second it has gone 4.4 ft.  That's 132 ft per 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 (half of black powder)
                         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.  Test your charge.
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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                            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 next 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 Goex 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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                         SILVER-SOLDERING
                    (also called silver-brazing)
   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
56% 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 56% silver-braze from Ace Hardware, $20
   This alloy is superior. The metal must first be sanded bare, solvent-
cleaned and fluxed.  Use a 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 into the joint!  45% silver silver-braze requires 165 F more
degrees and in some cases two torches will be needed for that alloy.
The proper distance from the torch is crucial.
   The metal should be farther than the bright blue part of this MAPP gas
flame, which is the hottest point (about 2100 F), TOO HOT for proper brazing.
Clean off the hardened flux with boiling hot water.  Steel-wool and wire-brush
the joint to check the bond.  If it's not right, re-flux, reheat and re-braze
until it's right.
   Harris Safety-Silv 56 is the same alloy, found in welding-supply stores.
   Flux can be moistened with water if it gets too dry.
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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 in.  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 1/2" from the end of the burner.
Propane burns at 1900 F at that distance from the end of the burner.  But it
is best to keep the torch 3/4" away so as not to overheat the tank metal.
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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 roaring 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 clamps to the bottom of the motor after the "rocket fuel" is
in, it is seated on the launch base and then everything is 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 to 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 Goex 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 warnings,
not just 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 of any
responsibility.  BUYER BEWARE!  We had to go back to our old standby of pyro
fuse delay which 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.
  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 holddown 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 after first launch.
   The apogee was much less than expected according to our book on steam
rockets and so no drogue was used after this launch.
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: 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.
The BOILING OVER launch.
   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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                        OTHER STEAM ROCKETS
The BOILING MAD steam rocket (printable).
The BOILING MAD fire extinguisher tank launch.
The RED DRAGON fire extinguisher tank rocket.
The BLUE BULLET water bottle steam rocket.
   Highest-acceleration rocket on the planet!
NOTE: Using small propane and MAPP gas tanks for steam rockets requires the
right amount of water.  Leave an air space and don't underfill or the metal
will be overheated. The highest pressure normally is 240 PSI if left in the
hot sun, but burst pressure is 960 PSI.  So stay under 600 PSI.
The YELLOW JACKET MAPP gas tank rocket.
The GREEN MONSTER propane tank rocket.
The LEPRECHAUN propane tank rocket.
The four QUICKIE propane tank rockets.
The YELLOW BIRD MAPP gas tank rocket.
Locating downed rockets.