Sergey Macheret

Sergey O. Macheret (born December 25, 1957) is an American physicist and aerospace engineer known for his contributions to plasma science and engineering. Macheret formulas for endothermic exchange reactions and Macheret-Fridman model of vibration-dissociation coupling are widely used for analysis of hypersonic and other chemically reacting flows. He is a former professor at Purdue University.

Career
Macheret graduated from Moscow Institute of Physics and Technology in 1980 and received his PhD from Kurchatov Institute in 1985. He worked at Ohio State University, Princeton University, and Lockheed Martin Aeronautics Company. He was a professor at Purdue University School of Aeronautics and Astronautics from 2014-2024.

In 2022, he was selected as a Fellow of the American Institute of Aeronautics and Astronautics (AIAA), a distinction given in recognition of notable contributions to the field.

Macheret also received AIAA Plasmadynamics and Lasers Award in 2022 "for pioneering work on novel plasma generation and control methods and on aerospace applications of plasmas."

Macheret formulas
The formulas are used for estimation of non-equilibrium rate coefficients of the simple-exchange endothermic reaction: $$XY(v)+Z \rightarrow X+YZ$$. Such reactions appear in low-temperature nonequilibrium plasmas where a substantial fraction of energy input goes into vibrational excitation of molecules. The formulas are obtained by applying classical mechanics methods for high temperatures and semi-classical approximation for moderate temperatures.

Assumptions:

1. Translational-vibrational non equilibrium: $$ T>T_v $$ or $$ T<T_v $$.

2. Collisions are collinear and rotational energy effects are negligible.

3. The duration of collision is much faster than the period of molecule vibration.

4. The vibrational energy obeys Boltzmann distribution.

Formulas and relations:

$$k(T,T_v)=Z(T,T_v) k^0(T)$$

Nonequilibrium factor in the high temperature case ($$T \geq \theta$$):

$$Z(T,T_v)=\exp\left[ -\frac{E_a-W}{\alpha_M T_v + (1-\alpha_M)T} - \frac{W}{T}+\frac{E_a}{T}\right] $$

$$\alpha_M=\frac{m_Y(m_X+m_Y+m_Z)}{(m_X+m_Y)(m_Y+m_Z)}, \quad W=E_a(1-\frac{f_v}{\alpha_M})$$

Nonequilibrium factor in the low temperature case ($$T<\theta$$):

$$Z(T,T_v)=\left[f_v\exp(-\frac{T_v}{\theta})+(1-f_v)\exp(-\frac{T}{\theta})\right]^{E_a/\theta}\exp\left(\frac{E_a}{T}\right)$$

Legal issues
On February 1, 2023, Macheret was taken into police custody under alleged preliminary charges of distributing and possessing methamphetamine and making an unlawful proposition for sexual favors to an undercover police officer. The methamphetamine-related charge was later dropped, and three unlawful proposition misdemeanor charges were filed. On February 28, 2024, Macheret pleaded guilty to one charge of unlawful proposition that involved an undercover police officer. Two more counts of unlawful proposition were dropped as part of a plea deal.