Mayday

Well, the availability of potassium nitrate varies upon location (concerning legal matters), although it isn't your only option to make cheap, easy homemade rocket fuel. Potassium nitrate is an oxidising salt, a nitrate salt to be more specific. There are other nitrate salts, such as sodium nitrate and ammonium nitrate. Sodium nitrate can be bought in various forms. Ammonium nitrate is also easily attainable, as a fertilizer and in Instant Cold Paks (the outer pouch of small beady while balls). Both need purification, although Google and YouTube will help immensely with those matters. There are other oxidizing salts, such as potassium permanganate, potassium chlorate, sodium chlorate, sodium perchlorate, and potassium perchlorate. Potassium permagrate wouldn't work well in rocket fuel, and isn't very easy to obtain or synthesize, however both are possible. Potassium and sodium chlorate can be made easily in the home, by boiling bleach and filtering (for sodium chlorate) and letting the filtered solution to dry, or before the solution dries, you may add potassium chloride (salt substitute, bought easily at a grocery store) and stirring a lot. The leftover dried crystals that went through the filter are what you ate trying to get. An important note: both potassium and sodium chlorate are fairly unstable, and powerful. They might cause your rocket to melt or explode in misproportioned quantities. They are safe to handle without the fuel being mixed or bonded. Perchlorates, both potassium and sodium (and others, there are several) are nasty, and should only be used in explosive blasting caps ore novelty fireworks (flash powder). Nitrocellulose might work, I am not sure, and don't bet anything on it. You can add stuff to your fuel-oxidizer mixture, like powdered aluminum, iron oxide, and sulfur (in minute amounts, less that 30%) Try black powder, it does contain potassium nitrate, but it is sold in WalMart, Bi-Mart, and many other places as black powder for reloading black powdered guns. That's probably your best bet. Remember, fire hurts.