# How is chamber pressure determined for rocket engines?

I've been looking for this for quite some time now, and I can't find anything other than calculations where they already assume a chamber pressure. So my questions are two:

• What are the equations for calculating the chamber pressure for a bipropellant engine? In case it's the opposite, how do you find out the needed propellant flow rate so that you achieve the design chamber pressure?

• When you have a pressurized gas thruster, that is, with no combustion, what do you have to take into account in order to calculate the parameters of the injector?

• Your second question is already answered at space.stackexchange.com/questions/21577/… – Nathan Tuggy Jun 2 '17 at 15:10
• No, it's not. That's why I am asking again. Yes, you have a regulator that you can control, but you should be able to calculate before even running the engine how much feed pressure you need. And I doubt you would feed it with the chamber pressure you want, cause the chamber is open, therefore you won't achieve as much pressure. – mariohm1311 Jun 2 '17 at 19:16
• If you're not satisfied with the answer(s) because you think they're wrong, asking a new question isn't the way to handle it. With more rep you can add a bounty for better answers, or you can edit the question to be clearer. Otherwise, we're just going to give the same answers again, or nothing. – Nathan Tuggy Jun 2 '17 at 19:19
• What else can I do? It's not like I can add a bounty, and I don't really understand what's not clear about the question. – mariohm1311 Jun 2 '17 at 19:22
• Then just be patient and hope for a late answer some time, or for more rep elsewhere that allows you to put up a bounty. – Nathan Tuggy Jun 2 '17 at 19:26

$$\dot{m} = \frac{P_{c}A_{t}}{C^*}$$ where $$C^* = \frac{\sqrt{RT_{c}}}{\sqrt{\gamma}(\frac{2}{\gamma+1})^\frac{\gamma+1}{2(\gamma-1)}}$$