Heating resistor for an electric burner?

[Jadeit]

I want to make electric burners for modeling tricks like igniting a rocket engine.
An SMD resistor is taken, the supply wires are connected and the whole thing is covered with an incendiary mixture with a high burning temperature.
When a large current passes through the resistor, the resistor heats up until it "burns" and this causes the mixture around the resistor to burn.
For 12V and above I use a 500m Ohm resistor, size 0402 or 0603.
From an electronics perspective
voltage source. NiMH or LiOn simply a rechargeable battery typically extracted from a used battery for models or hand tools.
Voltage theoretical 3.2 - 3,7 V , internal resistance, only god knows
Switching element: MOSFET in SOT23 ,RdsOn 40mOhm
The transistor controls the ultra-small MCU, for example the PIC10 in the role of a timer
Parasitic resistance, wires, switch u to 50mOhm.

now we come to the question, what resistance is optimal for a resistor for burners?

 

[betwixt]

Why use a resistor at all? It seems silly to sacrifice one each time you ignite. Why not use a nichrome wire that can be used many times?

Brian.

 

[barry]

I want to make electric burners for modeling tricks like igniting a rocket engine.
An SMD resistor is taken, the supply wires are connected and the whole thing is covered with an incendiary mixture with a high burning temperature.
When a large current passes through the resistor, the resistor heats up until it "burns" and this causes the mixture around the resistor to burn.
For 12V and above I use a 500m Ohm resistor, size 0402 or 0603.
From an electronics perspective
voltage source. NiMH or LiOn simply a rechargeable battery typically extracted from a used battery for models or hand tools.
Voltage theoretical 3.2 - 3,7 V , internal resistance, only god knows
Switching element: MOSFET in SOT23 ,RdsOn 40mOhm
The transistor controls the ultra-small MCU, for example the PIC10 in the role of a timer
Parasitic resistance, wires, switch u to 50mOhm.

now we come to the question, what resistance is optimal for a resistor for burners?

Seems like an awful lot of trouble for something you can already buy. They make devices specifically for your purpose in model rocketry. They’re called igniters.

STARTECH Starters - Estes Rockets

The new StarTech starters stay true to the design of the original, with one key addition. The small nichrome wire, the one that heats the propellant at launch, has been dipped in a specially crafted chemical compound that reacts with the heat of the wire to create a large burst of heat and...

estesrockets.com

 

[dick_freebird]

Model rocket companies like Estes sell (or used to) igniters along with
the engines. These are a NiCr wire with a bit of flammable charge coated
on. Model rocket ignition without that "charge" is even more unreliable
than with (in my youth, about 1 in 4 tries would light off).

A plain resistor is designed oppositely, to -not- flame out on overstress.

 

[D.A.(Tony)Stewart]

Model rocket companies like Estes sell (or used to) igniters along with
the engines. These are a NiCr wire with a bit of flammable charge coated
on. Model rocket ignition without that "charge" is even more unreliable
than with (in my youth, about 1 in 4 tries would light off).

A plain resistor is designed oppositely, to -not- flame out on overstress.

I guess you may not have used ignition plugs or tape to build up heat, pressure.

I used to be on the Black Brandt launch team in the late 70's when I designed Doppler instruments and antenna for them.

They used squids which do the same as Nichrome wire to heat the solid fuel in contact with the fuse wire, that gets up to temperature.1 watt on a 1/4 W piece of wire will easily exceed heat up but slow, so measure R and inject 2 W for faster ignition and cut power to save wire. SMT resistors will also get to 300'C but may crack before then.

If it doesn't get hot enough, it won't start. The auto ignition temperature is 282 'C typ. so which can be reached with promptly with Li Ion 3S2P or 10~11V.