Black Powder Rockets

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Click = Here to see a QuickTime movie (File size 231kb) of a black = powder=20 rocket launch with reaction from some bystanders. (This video was = shot at=20 the 2000 WPA=20 Western Winter Blast. Free Quicktime player available here.)

This page deals with general info, mixing the=20 comp, the construction<= /A>=20 of a black powder rocket using your rocket tool set, as well as=20 'sticking' and fusing the rocket.

This web site is prepared for purposes of education = only.=20 If you want to read these pages for an understanding how rocket = propellant=20 systems are physically made and how they fly, then this should = suffice. We=20 assume no responsibility for the use of this material by any = person. If=20 you attempt to use any of these materials in order to make = devices, you=20 should be in compliance with all laws and regulations and observe = the=20 maximum possible safety precautions.

Why a Black Powder (BP) = Rocket?=20

Easy to obtain chemicals=20
BP is a well known and fairly predictable product=20
Easy to work with=20
Fairly forgiving ? given sensible safety issues.=20
It can be quite spectacular!

Considerations for BP:

BP rockets tend to lift off of the pad at a slower pace than = whistle=20 rockets.=20
Max altitudes tend to be lower. (Not all the time!)=20
Hand made BP burns at a much slower rate than commercial or = meal BP.=20 This is not a bad thing. (When using meal, it is recommended to = slow the=20 mixture down ? refer to formula table.)

How a BP Rocket Works

The comp is burned in a core-burning fashion ? from the = inside=20 to the outside - along the length of the hole (made by the = spindle) in=20 the fuel. Material then burns during the coast stage in an end = burning=20 fashion, releasing spark but not attributing too much to lift. = Ideally,=20 enough material is present to allow the rocket to coast to = apogee -=20 there fire is passed to your payload.

Tubes and Sticks

Tube size ration:

Tube ID =3D 1=20
Tube OD =3D 1.25 to 1.50 ID=20
Tube Length =3D 10 ID=20
Note all ratios deal with the = ID=20

The following table should help you decide what kind of sized = tooling=20 you will need.

Rocket Size ID OD Length Min Stick Length* Payload Weight*

8 oz. 5/8" (.60") 1" 6 1/4" (6.25") 30" 120 grams

1 lb. 3/4" (.75") 1 1/4" (1.25") 7 1/2" (7.50") 36" 180 grams

3 lb. 1" 1/5" (1.50") 10" 48" 500 = grams

*Stick lengths and payloads are general recommendations. = Longer=20 sticks will cause the rocket to be more stable, but detract from = the=20 payload weight. Sticks are around 1/4? to 3/8? wide ? stout = enough so=20 they don?t snap when you hold the rocket (with payload) up by = the end of=20 the stick. Cut sticks shortly before using them to avoid = warpage.

Tubes can be ordered from many sources. Check out our friends = at Skylighter.com for an up-to-date = list.

Nozzle Material

Can be many different materials. It must be able to withstand = the=20 abrasive effects of the gas jet, but easy to deal with and not = damage=20 your tooling.

Material Pluses Minuses

Bentonite Clay or Fire Clay - Cheap, easy to obtain
-=20 Effective
- = Subject to=20 erosion, esp. on larger rockets

Kitty litter (added to clay 50%) - Cheap, easy to obtain
- = More=20 effective than clay alone - Some prep work

Wax added to kitty litter/clay or = 'clumpless' kitty=20 litter - Makes clay 'stickier'
- = Much more=20 effective than clay alone - Requires = preparation

Durhams Water Putty
- = Excellent=20 erosion resistance

- = Requires=20 preparation before ramming and drying time after=20 ramming

MIXING THE = COMP=20

Chemicals

Sulfur=20
KNO3 - Potassium Nitrate (K-Power fertilizer)=20
Air float charcoal=20
Large grain charcoal (80, 36, 20 mesh - depending on your = taste)=20

Formulas

The three major components of Black Powder can be mixed and = used dry.=20 This method is somewhat dirty, but is quick and easy to do. The = mix can=20 also be wetted down or have a binding agent added to reduce the = amount=20 of dust. (This will slow the burn rate down.)

Although BP has been around for many years, there are still = quite a=20 few folks that have their own unique mix percentages. The = percentages=20 given here are for general purposes. BP is quite forgiving, and = volumes=20 don't have to be exact down to the very last gram. (But it = helps!) BP=20 Rocket fuel burns quite slowly. (If you use meal BP, you will = need to=20 slow it down!)

Note: All numbers are in = percentage of=20 total weight.

Separate Ingredients in % Range Typical

Potassium Nitrate (KNO3) 55-70 60

Charcoal (mixed) 25-35 30

Sulfur 5-15 10

Formulae (in %)

8 oz. 1-2 lb. 3-4 lb. Tom's 1 lb. Mix*

Potassium Nitrate 60 60 60 70

Sulfur 10 10 10 10

C - Air float 15 10 10 10

C-80 mesh 10 15 15

C-36 mesh 5 5

C-20 mesh 20

(* So it adds up to 110%. If the formula works, who says it = needs to=20 be 100%? Do you really want measurements to look like 63.6%? = Didn't=20 think so.)

[Webmaster note: I developed 'Tom's Mix' to give a tall = column of=20 spark. This formula results in a rocket with a slow takeoff, a = huge=20 pillow of spark on the ground, and a column of that will last, = so when=20 the rocket delivers it's payload you can follow the tail all the = way=20 back down to the ground. Depending on your taste, make your own=20 variants! This works best for 1lb rockets. Larger rockets may = need to=20 have the KNO3 backed down.)

The strength of the formula can be adjusted by changing the = ration of=20 air float (more =3D faster if you subtract larger charcoal), = meshed=20 charcoal (more =3D slower), and KNO3 (more =3D faster). You can = change many=20 variables, depending on your tastes. Start with a small batch to = verify=20 your mix is OK. And always write down your formula and note=20 results!

Pictured is some agricultural grade potassium = nitrate -=20 unmilled on the left, milled on the right. Note how the = nitrate=20 looks like salt on the left, and fine sugar on the right. = (Click=20 picture for larger view.)
The burn rate of the powder can be changed by altering = the=20 particle size. Ball milling the potassium nitrate helps to = speed=20 up the burn rate. Ball milling the sulfur is also a good = idea.=20 (Remember to thoroughly clean out your ball mill after = using it.)=20 Potassium nitrate comes under many different brand names. = K-Power=20 fertilizer i s one such name. It is agricultural grade=20 KNO₃ and is adequate for use in rocketry. = However, the=20 particle size is on the order of salt crystals, and must = be ball=20 milled before using. If you do not want to do this extra = step (or=20 do not *yet* have a ball mill), contact our friends at Skylighter.=20 They stock both milled and unmilled potassium nitrate. = (And a=20 plethora of other chemicals as = well.)

(Freebie tip: Ball mill the air float charcoal and sulfur = together=20 in a 1:1 ration. They are both fuels and safe mixed. The air = float will=20 keep the sulfur from clumping, and it is easier to measure = out!)

Screen the sulfur and air float charcoal together (assuming = you have=20 not already ball-milled them together) three times. Add in the = potassium=20 nitrate and screen 3 more times. Add in the course charcoal, and = screen=20 (using a very course mesh screen) three more times. This mix is = called=20 "green mix" and is not true black powder. However, it is more = than=20 adequate for a black powder rocket. Remember to clean your = screens after=20 each use.

(When screening, if you have properly ball-milled your = chemicals, it=20 is recommended to start with a 20 then 40 then 60 mesh screen. = By this=20 time, you have achieved a decent mixing.)
If you add 4 to 5% petroleum jelly to the mix, it will reduce = the=20 dust problem significantly. However, we have observed that this=20 significantly slows down the burn rate (of green mix). = (Comparison burn=20 rate - a line of untreated green mix took 8 seconds to burn off. = Treated=20 with petroleum jelly - 20 seconds.)

Variations

Meal Powder Plus (in %)

Brown (1878) Faber (1919) AFN (1983) Steyding (1991)

Meal Powder 13 15 80 70

KNO3 52 62 -- --

Charcoal 25 12.5 20 30

Sulfur 10 12.5 -- --

You could also add in 3-5% Titanium for a white spark tail. = (NOTE:=20 Any time you add metal to your comp you MUST press the rocket. = DO NOT=20 use a hammer.)

CONSTRUCTION

You will need your tool set, a scoop, tubes, nozzle = material,=20 hammer or press, and enough comp on hand for one rocket. = (It's a=20 good safety precaution to have enough comp on hand for one = rocket,=20 and leave the rest of the comp covered, away from your = work=20 area.)

Put a tube over the spindle and seat it at = the base.=20 Add one full scoop of nozzle mix. Using the longest drift, = compress it with either ramming or=20 pressing.

The longest drift has a beveled end, so that the gasses = exit=20 the rocket by being funneled into the nozzle. (The other = drifts=20 are squared on the ends.)

The drifts also have successively smaller holes to = accommodate=20 the spindle's taper.

Extract the drift, add one scoop of comp, = and=20 repeat. Change out the drifts when the next drift has = sufficient=20 clearance of the spindle.

It's usually a good idea to mark your drifts so that it = won't=20 'bottom out' on the spindle, and when to change to the = next size.=20 (I mark the danger spot with red and the change out spot = with=20 black.) Usually you count your scopes - the number depends = on the=20 size of the scope.

It's also a good idea NOT to change out the drifts too=20 quickly. If the drift gets close to bottoming out, you = could be=20 creating a friction point. Change out the drifts after it = is well=20 clear of the mark.
Make sure the solid drift will NOT come in contact with = the=20 spindle. The compression of the solid drift on the end of = the=20 spindle has been well documented as a cause of=20 accidents.

When you have reached the top of the = spindle, add=20 one full scoop of comp and use the solid drift. Now add = one half=20 scoop of nozzle mix and compress.

Remove the rocket motor from the spindle. = (This is=20 where you may need to use the strap wrench. I find that I = put the=20 strap around the base, hold the wrench against my leg and = use both=20 hands to loosen the engine.)

At this point, you can do a little test. Tap = the=20 nozzle end of the rocket against your table or ramming = station by=20 dropping it about an inch or so 3 or 4 times. You may see = some=20 dust come out on the first or second tap, but by the = fourth one it=20 should be clean. If comp continues to fall out (in small = bits or=20 dust), you may have a crack. Use this one with = caution.

Take a small drill bit (3/16" or 1/4") and = slowly=20 hand drill out a hole at the top of the clay cap to = pass fire=20 to your payload. (NOTE - If you have any added metal to = your BP,=20 this must be done with great caution. Take it = s-l-o-w.)

It is usually advised to add your payload before you add = the=20 stick your rocket. This will help you pick a proper weight = stick.=20 Add in a teaspoon of meal BP to the void at the top of the = rocket=20 to help pass fire and add your payload.
Using strapping tape, attach it to the top of the = rocket.=20 (There are many methods for this - usually a strip around = the=20 joint to help hold in the loose BP, and strips across the = top of=20 the heading down to the body of the=20 rocket.)

STICKING = AND FUSING=20 THE ROCKET

Sticking the = rocket

This is a "batch-o-rockets" I did at the 2000 = WWB. There=20 are 4 1lb rockets on the left, 6 3lb rockets on the right. = Payloads are attached, sticked and fused. The one on the = far left=20 has been trimmed for balance, the rest have yet to be=20 balanced. Put the stick about 1/2 to 3/4 up the side of the = rocket, and=20 secure using (minimum of) two strips of strapping tape.
AFTER you have applied the payload, trim the stick = until it=20 balances on your finger just below the nozzle. If the = stick is=20 longer, it will be more stable but be heavier. Shorter, = and it=20 will be lighter (faster/higher), but may be unpredictable. = Use=20 strapping tape to adhere the stick to the rocket in two=20 places.

This is a generally accepted rule, and works very well. = You may=20 hear terms like 'center of pressure' or 'center of = thrust', but=20 that is not covered here. Just know that if you balance = your=20 rocket as described above, it has an excellent chance of = flying in=20 a general upward direction. =

Fusing

Two methods of fusing. If you fuse from the nozzle end, the = rocket=20 will take more time to build up enough pressure for lift, but = will also=20 create a larger cloud of sparks and will have a gentle lift-off. = (The=20 rocket video at the top of the page was fused in this manner.) = If you=20 fuse from the deep inside of the cavity, it will light and lift = quicker.=20 Make sure the Visco has a sufficient side-spit to light the = composition.=20

Method 1:
Add a length of = Visco= =20 up into the ?business? end of the rocket about 2 inches = up. (It=20 must come in contact with the BP.)

Apply a strip of masking tape = across the=20 bottom to secure the fuse. Keep enough Visco exposed to = allow a=20 sufficient time to retreat to a safe distance.

Method 2:
Put the business = end up.=20 (Optionally add in a bit of meal or loose BP. You may try = and add=20 some NC lacquer to hold the loose BP inside of the = rocket.)

Add in a length of quic= kmatch=20 with approx. 1? exposed.

Stuff with tissue paper to = hold in loose=20 BP and match.

Tape/secure the nozzle and = quickmatch=20 with some masking tape. Add a couple of inches of Visco to = the=20 other end of the quick match, secure with masking tape.=20

These rockets are fun and relatively easy to build. They are = great for=20 the beginner manufacturer. And remember:=20

There are local, state, and federal laws that restrict or = prohibit the=20 use and/or manufacture of pyrotechnic devices. The tools sold in = this web=20 site are strictly for the use and manufacture of devices made = within legal=20 guidelines. We do not encourage, nor are we responsible for = individuals=20 who knowingly or ignorantly violate the law.