Fuel Temperature

[SRP Crew]

Does anyone know the temperature at which an AP or BP motor burns at?

 

[marcs]

Last time I checked an AP propellant formulation in ProPep, it showed the temperature as 3850F or so.

This will vary with formulation and such, around 3,500F - 4,000F is probably a fair range to your question (for AP).

Marc

 

[bobkrech]

Do you mean at what temperature will a rocket propellant ignite. If so it's around 600F.

Bob

 

[SRP Crew]

I'm after nozzle erosion of different metal types. That's my goal ultimatlely. So the hotest possible heat thrown from the rocket fuel passing through the nozzle throat area is what I'm after. That's why my question was based on how hot AP & BP fuel get.

Yes I think the AP burns very hot, but have heard varying responses in the actual temperature ranges of both.

 

[FROB]

I'm after nozzle erosion of different metal types. That's my goal ultimatlely. So the hotest possible heat thrown from the rocket fuel passing through the nozzle throat area is what I'm after. That's why my question was based on how hot AP & BP fuel get.

Yes I think the AP burns very hot, but have heard varying responses in the actual temperature ranges of both.

In that case i think there are a lot of published research data you can find on NASA's site on the subject.
From what little i remember, there's more to it than temperature. the hot gas is extremely corrosive, depending on fuel/oxidizer and their ratio. Nozzel shape has an impact as well.

 

[bobkrech]

If you want to know the chamber and exhaust temperature of a rocket motor, you should be using the ProPEP code to calculate combustion conditions, but you also should be aware that heat flux, not gas temperature, determines the nozzle erosion rate.

No one should be using metal for a nozzle. Graphite is inexpensive, easy to machine, lighter in weight, and won't erode with amateur propellants in well designed motors.

You should be aware that at TRF we don't encourage anyone to make their own motors, nor do we permit detailed discussions of amateur propellant formulations. There are many safe commercial hobby rocket motors to chose from. Making your own motors safely is not cheaper than buying certified commercial hobby rocket motors, and if you don't understand rocket motor design engineering, you are more likely to hurt yourself or someone else than to make a decent rocket motor. If you want to roll your own, you should look for other forums dedicated to amateur motor fabrication.

Bob Krech, TRF Propulsion Moderator

 

[darkhelmet]

I'm after nozzle erosion of different metal types. That's my goal ultimatlely. So the hotest possible heat thrown from the rocket fuel passing through the nozzle throat area is what I'm after. That's why my question was based on how hot AP & BP fuel get.

Nozzle erosion not only depends on the melting point of the material and the exhaust gas temperature, but also on the heat transferred. Add to that the corrosive and abrasive characteristics of various formulas, it isn't easy to predict. It's an interesting academic problem, though.

For practical purposes, graphite is a better choice over metal. For high-volume, smaller motors, a molded high-temp plastic is a good choice; the grain geometry is designed to allow for the erosion.

If you are looking at adding a scale model nozzle extension to a model with a commercial motor, keep in mind that the exhaust gases cool significantly after leaving the throat region. A non-metallic scale-like extension will hold up to several launches if coated internally with JB Weld.

 

[SRP Crew]

Thanks for your deep insight Bob, but commercially bought motors are absolutely not cheaper where I am north of the 49th. We can get fleeced up to 300% the cost of Aerotech and Estes motors compared to what my friends in the States pay. It's very frustrating and unreasonable to do something we enjoy, at such a high cost.
Alternatives are getting more popular by the minute and we all should be prepared to keep it as safe as possible. I do agree with you strongly on this.

So, I will adjust my inquiries on this forum accordingly.

Thanks again.