wats the stuff inside of those hobbie roket engins?(the powder)

Black powder

ummm... be careful though, the black powder that you make burns A LOT slower than the black powder you buy, I dont know if you plan on making rocket motors or just unloading them. If your planning on making a rocket, and you use commercial black powder it'll just blow up.

Depending on how you make it. If you use meal you'll probly get a CATO.

Well commercial black powder and homemade black powder are both made with the same material, but in factories they have an extra step they do when making the powder to make it faster burning. I'm not too good with most chemicals so I dont know what meals and CATO are, but I'm guessing you use the meals in the process of making the powder and you get a CATO that burns fast....

no meal powder is veryvery fine thus it burns fast.CATO stands for Catastrophe At Take Off its when a rocket endgine explodes dued to high pressure and not enough release.

so basically dont add a meal to your rocket propellant, otherwise you just get a funny looking pipe bomb

take the stuff inside out
(take a hammer)i no this is dum but ive dun it like 30 million tymes and have never been srewed! and pownd the cartrige and to colors of powdr will come out black and grey
mix them
and pressure them again after they have been mixed
(like into a toilet paper tube untill the top and then wik it and lite it
dont kill yourself
its really fun!!!