If I may, I would like to help here. There are many attempts to get BP to burn at high altitudes (Read: "In a vacuum") some work, others are rather spectacular and heartbreaking when they fail. I watched a VERY experienced flyer's rocket come in rather hot from 30K ft when the BP charge did not burn enough to eject the nosecone. I first designed The Peregrine CO2 ejection system (followed by the RAPTOR CO2 ejection system) for this reason. It should be noted that I tested these devices in a vac chamber and pulled 28.5"Hg (Simulating about 80K ft) to make sure they can deploy at high altitudes.
I have tested other gas generation devices in a this vac chamber with a 1/2" plexiglass top so that I can see and video test results. All I can tell you is that it is absolutely FASCINATING to watch the vacuum "suck the burn right out" of some of these devices! Scientifically and intuitively we know what will happen but to watch it is another thing all together! So my advice, if you decide to try and get BP to work at high altitudes is to find someone near you with a vac chamber to test it before you fly it!
If you are interested in CO2 ejection devices that have been tested in such a vac chamber you may wish to consider either the Peregrine or The RAPTOR from Tinder Rocketry!
https://www.tinderrocketry.com/rocketry-co2-ejection-system
I have tested other gas generation devices in a this vac chamber with a 1/2" plexiglass top so that I can see and video test results. All I can tell you is that it is absolutely FASCINATING to watch the vacuum "suck the burn right out" of some of these devices! Scientifically and intuitively we know what will happen but to watch it is another thing all together! So my advice, if you decide to try and get BP to work at high altitudes is to find someone near you with a vac chamber to test it before you fly it!
If you are interested in CO2 ejection devices that have been tested in such a vac chamber you may wish to consider either the Peregrine or The RAPTOR from Tinder Rocketry!
https://www.tinderrocketry.com/rocketry-co2-ejection-system