I didn't know aluminum burned, but pretty much anything burns under the right set of circumstances.
Depends on your definition of BURN. Oxygen is truly nasty stuff and combines chemically with many substances but there are many exceptions, like the Inert Gasses, gold, silver, platinum, and anything that has already reacted with it like water, carbon dioxide, ceramics, or ALUMINIUM OXIDE. Aluminium oxide like carbon dioxide and water have already reacted and will not react further.
Aluminum is a HIGHLY reactive metal. It is never found in its pure state in nature and ores of aluminum are very nonreactive making it very difficult to extract the pure aluminum. Napoleon III, the first President of the French Republic, served his state dinners on aluminum plates. Rank-and-file guests were served on dishes made with gold or silver. Aluminum reacts very readily with oxygen (albeit slowly) to form the oxide. That's why aluminum doors are a dull grayish color. That dull gray is aluminum oxide or corundum which is stronger and tougher than the aluminum itself. That tough oxide layer seals the rest of the aluminum preventing further oxidation.
Now in light of that consider Aluminum. It is invariably coated with the oxide. Burning the aluminum FIRST requires that you breach the oxide shell which occurs at 3680F. Once the oxide shell is breached the Aluminum reacts with oxygen (burns) and the temperature quickly soars to 6920F
As for rockets, I'm not sure why aluminum oxide would be used then unless it had to do with the fact that everything is mixed in.
You keep postulating that and I can only suggest that you revisit your source material. Aluminum oxide is not and cannot be a fuel.
Solid rocket fuel is the original rocket fuel, dating back to the early fireworks developed by the Chinese centuries ago. For the SLS (Space Launch System) boosters, aluminum powder serves as the fuel and a mineral salt, ammonium perchlorate, is the oxidizer.
The powerful aluminum-ammonium perchlorate reaction fuels the twin SLS solid rocket boosters.
Aluminum is the most abundant metal on Earth. It's also highly reactive. Aluminum is so reactive, in fact, that it's not found naturally in its pure form but only in combination with other minerals. It's this ability to readily combine with other elements (Oxygen) that makes aluminum so useful.
Ammonium perchlorate, the salt of perchloric acid and ammonia, is a powerful oxidizer (explosive). In the boosters, the aluminum powder and ammonium perchlorate are held together by a binder, polybutadiene acrylonitrile, or PBAN. The mixture, with the consistency of a rubber eraser, is then packed into a steel case.
When it burns, oxygen from the ammonium perchlorate combines with aluminum to produce aluminum oxide, aluminum chloride, water vapor and nitrogen gas – and lots of energy.
This reaction heats the inside of the solid rocket boosters to more than 5,000 degrees Fahrenheit, causing the water vapor and nitrogen to rapidly expand. Just like in the liquid engines, the nozzle funnels the expanding gases outward, creating thrust (Newtons Third Law – Action/Reaction Pairs) and lifting the rocket from the launch pad.
Compared to liquid engines, solid motors have a lower specific impulse – the measure rocket fuel efficiency that describes thrust per amount of fuel burned. However, the propellant is dense and burns quite quickly, generating a whole lot of thrust in a short time. And once they've burned their propellant and helped propel SLS into space, the boosters are discarded, lightening the load for the rest of the spaceflight.