def isen_nozzle_mass_flow(A_t, p_t, T_t, gamma_var, R, M):
	"""
	Calculates mass flow through a nozzle which is isentropically expanding
	a given flow

	Input variables:
		A_t 		: 	nozzle throat area
		gamma_var 	: 	ratio of specific heats
		p_t 		: 	pressure at throat
		T_t 		: 	temperature at throat
		M 		: 	Mach number at throat
		R 		: 	Perfect gas constant
	"""

	m_dot = (A_t * p_t * (T_t**0.5)) * ((gamma_var / R)**0.5) * \
		M * ((1 + (((gamma_var - 1) / 2) * \
		(M**2)))**(-((gamma_var + 1) / (2 * (gamma_var - 1)))))

	return m_dot