# What is the propellant consumption rate for Soyuz?

At what rate does a Soyuz propulsion system (KDTU-80) consume it's propellants? I am interested in the mass consumption rate of both the main engine (e.g. an s5.80) and a single DPO thruster.

Please specify if its the total propellant mass being consumed, or just that of the fuel or oxidizer (the ratios are readily available, but not the mass flow rate).

Estimating exact propellant consumption rate (mass flow rate) from easily available sources such as the Wikipedia page of KTDU-80 might be a bit imprecise, since we'll be using the thrust and Isp values to find mass flow rate, and in practice, it is done the other way around, as this answer by Russell Borogove suggests.

Now if rough figures are acceptable to you, we can find the mass flow rate from the definition of Specific Impulse:

$$F_{thrust} = g_0 . I_{sp} . \dot{m}$$ $$\therefore \dot{m} = \frac{F_{thrust}}{g_0 . I_{sp}}$$

For S5.80: $$\dot{m} = \frac{2950}{9.81×302} ≈ 0.9957~~kg/sec$$
For DPO-B: $$\dot{m} = \frac{129.16}{9.81×291} ≈ 0.0453~~kg/sec$$
And for DPO-M: $$\dot{m} = \frac{25}{9.81×285} ≈ 0.0089~~kg/sec$$