Rocket Engine Control - Need some help.

Hey everyone. I was just curious to see what type of recommendations you would have for hardware and what cost range am I looking at?

The main goal here is to be able to adjust the mass flow rate of the liquid oxidizer and liquid fuel tanks into the gas generator (small chamber) and larger combustion chamber. This adjustment will be based on the chamber pressure and potentially temperature. There might be some additional valve adjustments, but this is the basic idea.

I'm trying to draw out a block diagram to figure the system out, I would assume it is wisest to make it a closed loop system entirely?

I have a few papers and text I'm reading but most are decades old so it's a little tough.

Any help is appreciated!

I did something similar too many years ago. I would never do it again as it is crazy dangerous.

From what I remember.

Hardware - You need really fast acting thermocouples. Standard are not good enough.

Lots of checking of the hardware to ensure all is safe.

You ideally need a remote watch dog timer to monitor 2 bits from your processor (one on, the other off and alternate every second) and shut it all down if the processor stops or errors (either bit stays high or low).

Monitor thermocouples and if temp too high, shut down.

Have a test for everything as it is easier to tune if it has not blown up.

Valves, you need skillful control of the fuel valves. Other valves are quite specialised as they need to slam shut in a fail safe.

Be careful. It is quite unforgiving.

Dave_vo:
I did something similar too many years ago. I would never do it again as it is crazy dangerous.

From what I remember.

Hardware - You need really fast acting thermocouples. Standard are not good enough.

Lots of checking of the hardware to ensure all is safe.

You ideally need a remote watch dog timer to monitor 2 bits from your processor (one on, the other off and alternate every second) and shut it all down if the processor stops or errors (either bit stays high or low).

Monitor thermocouples and if temp too high, shut down.

Have a test for everything as it is easier to tune if it has not blown up.

Valves, you need skillful control of the fuel valves. Other valves are quite specialised as they need to slam shut in a fail safe.

Be careful. It is quite unforgiving.

All of my groups test firing will be done on a test stand in the desert.

Would an arduino kit not be recommended then?

It is up to you to understand and manage your risk. This will help.

As for control.
You need fast thermocouples, then work our if control system is fast enough to read them.
You need quality control valves to manage fuel and O2 sources.
You need smart software to manage the risks - is everything working like analogs, digitals and PID loops? The classic being the program stops running / power off etc, what happens? Managing all possible scenarios.

Bottom line. Manage your risk by understanding those risks. Then choose your control system.

Dave_vo:
It is up to you to understand and manage your risk. This will help.

http://en.wikipedia.org/wiki/Hazard_and_operability_study

As for control.
You need fast thermocouples, then work our if control system is fast enough to read them.
You need quality control valves to manage fuel and O2 sources.
You need smart software to manage the risks - is everything working like analogs, digitals and PID loops? The classic being the program stops running / power off etc, what happens? Managing all possible scenarios.

Bottom line. Manage your risk by understanding those risks. Then choose your control system.

Thank you.

I was looking over Copenhagen Suborbitals and they used a modified version of the arduino due. I'm speaking to a company soon about pressure transducers and thermocouple requirements given our pressure/temperature environment inside the chamber.

My plan is to test mixture flow before hand in a non combustive environment. We will also be doing an initial test fire with just a pressure fed system before moving onto the gas generator design.