This page documents the progress of Jimmy, Joey, Ian, and company in their quest for rocket candy powered rockets and other r-candy experiments. R-candy is an approximately 65:35 oxidizer to fuel ratio by weight.

Rocket Candy Short FAQ

What is Rocket Candy?

Rocket Candy, also know as r-candy or caramel candy propellant, is a rocket fuel made out of an oxidizer, most commonly potassium nitrate (KNO3), and a fuel, most commonly sugar or corn syrup, traditionally mixed at a ratio of 65:35 (13:7) oxidizer to fuel. Called candy because of the mixtures high sugar content. This fuel is popular among model rocketry enthuseists because of its ease of manufacture and its stability once made.

Is it dangerous?

All chemistry presents danger. Rocket science in particular has a well-deserved reputation for difficulty and danger. R-candy is on the safer side of most fuels, being well known and well experimented with. We should note that the model rocketry community and the Food and Drug Administration consider r-candy to be non-toxic, although ingesting large quantities of potassium nitrate is discouraged. Like sidewalk chalk. Cooking and chemistry are along a continuum, the primary difference being how edible the result is supposed to be.

Is it legal?

Yes, R-candy is legal to manufacture in the United States, but not to transport or sell without a permit from the federal government. Also, no more than four ounces may be used in a rocket without additional permits and/or licenses. Disclaimer: This is not legal advice, consult legal counsel should you have any concerns.

How is it made?

The most common way is the "skillet" method: mixing the ingredients in a skillet or saucepan over heat until melted together. Rather like hard candy, the result should break cleanly once cooled, though several additives can adjust how soft the result can be.

Safety Considerations:

R-candy deflagrates rather than explodes, because the combustion front travels subsonically. Nevertheless, be aware of the following precautions when experimenting:

Personal Protective Equipment: Safety glasses, and gloves.
Mix and heat R-candy out of doors, away from flame source and other inflammable material. A concrete pad is useful for this.
Make certain to mix the correct ratio of potassium nitrate and sugar. Improper mixtures may have different (lower) ignition temperatures than intended.
Keep precursor ingredients (potassium nitrate, sugar) away from the heat source used to mix them.
Keep a fire blanket and fire extinguisher ready to hand. The fire blanket can be used to cover a flare-up in the mixing vessel, and the fire extinguisher to control accessory flames.
R-candy is a self-oxidizing mixture, which means it contains both fuel and oxygen, and cannot be extinguished by water or a conventional fire extinguisher. In case of an unintended ignition, the only option is to isolate the mixture and wait. See this video of self-oxidizing combustion underwater: https://insider.com/watch-mini-rocket-engine-burn-underwater-super-slow-motion-video-explosion-2017-7