Study on the Manipulation of Plasma Density around a Cubesat Using Magnetohydrodynamics

During hypersonic flight regime or re-entry flights, a phenomenon known as radio blackout occurs, in which the high velocities attained lead to a significant increase in temperature surrounding the vehicle. This raise is so substantial that the molecules around the vehicle start to ionize, surrounding the vehicle in electrons. These electrons will prevent electromagnetic waves from leaving or reaching the aircraft, preventing all communications. Several blackout mitigation schemes have been proposed, among which is the magnetic window. In this scheme, a magnetic field is imposed near the nose of the aircraft, which will then prevent electron movement, generating a spectral window through which the electromagnetic waves can pass. In this work, the effectiveness of this method in affecting the plasma density is tested. The mesh is tested for grid independency, ensuring an accurate solution in a sensible ammount of time. The effect of different magnetic field intensities is then tested for a CubeSat flying in hypersonic flight regime, in order to determine the effect of the magnetic field in the electron number density. Keywords: Magnetohydrodynamics, Radio blackout, Magnetic window, CubeSat

Numerical Analysis of a Multi-Species MHD Model for Plasma Layer Control of Re-Entry Vehicles

Several critical aspects control the successful reentry of vehicles on the earth’s atmosphere: continuous communication, GPS signal reception and real-time telemetry. However, there are some common issues that can interfere with the instruments operation, the most typical being the radio blackout, in which the plasma layer frequency modifies the electromagnetic waves in a way that makes communications to and from the spacecraft impossible. So far, there have been several proposed techniques to mitigate radio blackout, one of which is the usage of electromagnetic fields. Previous studies have proven the effectiveness of the usage of an electric and/or magnetic fields to manipulate plasma layers. Experiments on plasma layer manipulation during hypersonic flight regime are extremely costly. Therefore, there has been a continuous interest in the development of cheaper solutions, that can guarantee a reliable degree of accuracy, such as the development of complex multiphysics computational models. These models are becoming increasingly realistic and accurate, as more and more physical aspects can be considered, greatly increasing the accuracy and range of models. However, those models need to be validated with recourse to experimental data. In this paper we propose a model that uses a Low Magnetic Reynolds number, and accounts for five common neutral species: N2, O2, NO, N and O, along with several of their respective reactions: dissociation of molecular nitrogen and oxygen, and exchange. The model chemistry is then validated based on experimental data gathered by several authors.

A STUDY OF RADIO FREQUENCY BLACKOUT FOR SPACE PROBE DURING ATMOSPHERIC REENTRY PHASE

During the re-entry flight, the radio signal will be interrupted, which is commonly referred to as the communications blackout. Once the plasma sheath forms in the stagnation region of a small space probe, the probe losses more than 70 percent of its downlink data. This shows that the attenuation of the radio signal is very high during the re-entry. When the probe enters the Earth’s atmosphere, the high velocity, high surface temperature and high plasma frequency cause a shock wave layer, which is the main cause of radio blackout. For other reason, the completely reflection of the electromagnetic wave at all communication lines. This study describes the theoretical and numerical study of radio communication during reentry. The paper defines an approach to end radio signal blackout occurring in the wake region and how to exactly solve the radio blackout problem using new methods as injection of coolants, the aerodynamic shaping reducing the concentration of electrons, using transceiver with high operating frequency or interaction of Static Magnetic Field (SMF). Data from OREX probe are used to prove the solution to the Radio Frequency (RF) blackout problem. The significance of the used SMF method is established by computing the reduction in plasma attenuation.

Numerical Computations of MHD Flow on Hypersonic and Re-Entry Vehicles

In hypersonic flight of reentry vehicles the radio blackout is a typical problem, in particular because it arises during a critical mission operation point. To mitigate this radio blackout the magnetic window concept is proposed. In this work a numerical model is presented to accurately simulate the effect of a magnetic field interacting with ionized plasma surrounding the vehicle. The numerical model is based on the MHD flow equations. Initially, the code is validated for pure hypersonic gas dynamics. Diverse high resolution spatial discretisation schemes, within a Finite Volume framework, are analyzed for robustness. Afterwards, the numerical code is further validated for MHD flows using the well-known Hartmann case. A very good comparison between numerical and analytical results is verified. This allows a proper validation of the method in terms of Lorentz force, in particular under low-magnetic Reynolds number conditions. A very tough test-case is finally computed, being typical of a reentry capsule geometry. The accuracy of the model is then verified for different applied magnetic fields.