Reflectometer plasma diagnostics on a 25,000 foot per second reentry experiment

Grantham, W. D.

doi:10.1109/aps.1970.1150814

Cited by 9 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While most of the laboratory work concentrated on simulating the thermal and chemical phenomena that occur near the surface of a re-entry vehicle for testing heat shields [1][2][3][4], not much work was done to simulate the actual plasma number densities present during atmospheric re-entry. The experiments done on re-entry vehicles consisted mostly of electrostatic probe and microwave interferometer tests and successfully measured plasma density and electron temperature as functions of altitude and distance away from the re-entry vehicle [5,6]. More recently, complex computer simulations have been developed to model the plasma that exists during atmospheric re-entry [7,8].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Using a helicon source to simulate atmospheric re-entry plasma densities and temperatures in a laboratory setting

Lemmer¹,

Gallimore²,

Smith³

2009

Plasma Sources Sci. Technol.

View full text Add to dashboard Cite

The purpose of this research is to develop a plasma system capable of reproducing plasma densities found during atmospheric re-entry of a capsule. We developed a 150 mm diameter helicon source at the University of Michigan Plasmadynamics and Electric Propulsion Laboratory (PEPL) and used a Langmuir probe to characterize plasma properties downstream. The helicon source was operated with argon gas at a background pressure of 0.6 mTorr. We used a commercial RF-compensated single Langmuir probe to measure ion number density and electron temperature in the region downstream of the helicon source where we want to create conditions similar to those found during hypersonic flight within the atmosphere. We measured these values with and without the presence of a large 450 mm wide by 550 mm long surface downstream in the horizontal plane to simulate a vehicle surrounded by plasma in order to determine how the downstream body affects plasma properties. We found that the presence of a surface downstream of the helicon source lowers the downstream plasma density range from between 1.7 × 10 17 and 3.3 × 10 17 m −3 down to 0.55 × 10 17 and 1.3 × 10 17 m −3. In addition, the peak plasma potential decreases from 65 to 55 V, but the electron temperature remains unchanged ranging between 1.5 and 6.5 eV.

show abstract

Section: Introductionmentioning

confidence: 99%

“…Figure 1 shows how the electron number density varied as a function of altitude during the RAM-C re-entry experiments. Electron temperatures were found to range from 0.17 up to 1.3 eV [5,6]. Since matching plasma number density is the main goal of this research, we are not concerned with whether the simulated plasma is flowing.…”

Section: Introductionmentioning

confidence: 99%

Using a helicon source to simulate atmospheric re-entry plasma densities and temperatures in a laboratory setting

Lemmer¹,

Gallimore²,

Smith³

2009

Plasma Sources Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…Figure A shows the distribution of the electron density based on the 2D model. Figure B compares the results of the 3D numerical simulation with the reflectometer measurements presented in Reference along with the 2D simulation result . The variable of N e, max at a y of −0.2 m indicates the maximal electron density at −0.2 m from the wall to the outer boundary of the plasma sheath.…”

Section: Resultsmentioning

confidence: 90%

“…The vehicle is a blunt‐cone with a nose‐cap radius of 15.24 cm, a half‐angle of 9°, and a length of 1.295 m . Seven components and eighteen chemical reactions are used in this model, the components are N 2 , O 2 , N, O, NO, NO + , and e (electron) .…”

Section: Model and Formulationsmentioning

confidence: 99%

Impact of angle of attack on plasma flow and electromagnetic wave propagation around hypersonic vehicles

Ouyang

Liu

Zhang

2020

Micro & Optical Tech Letters

View full text Add to dashboard Cite

The flow field around the RAMC-II vehicle at differenrt angles of attack (AOA) was numerically solved using a computational fluid dynamics technique with a threedimensional model. Electron density, pressure, temperature, and collision frequency, which is given great importance in this paper. The maximal electron density, total pressure, and temperature at the same position decreases with the angle of attack on the leeward side and increases with the angle of attack on the windward side. The collision frequency is almost unaffected by AOA on the leeward side, but increases significantly with AOA on the windward side. Based on the realistic plasma sheaths obtained by hypersonic fluid model, a multilayer transmission model was used to study the electromagnetic (EM) wave propagation in plasma sheath at different AOA. The attenuation value of EM wave on the leeward (windward) side decreases (increases) with the AOA. So the influence of the AOA on the EM wave transmission must be considered in the communication of vehicle reentry. In addition, the EM wave attenuation on the leeward at the same angle of attack is always smaller than the windward side, especially at a large AOA. Therefore, the leeward side can be considered as one end of the communication to improve the communication quality. The conclusions of this paper have both theoretical and practical significance to better understand the communication"blackout" problem for the reentry of hypersonic vehicles. K E Y W O R D S angle of attack, electromagnetic wave attenuation, electron density, flow field, plasma sheath 1 | INTRODUCTIONDuring the hypersonic reentry stage of the RAMC-II mission, the surface temperature of the vehicle rises sharply due to the formation of shock waves in front of the vehicle. High temperatures cause more intense chemical reactions, such as ionization and the dissociation of gases, and results in a weakly ionized plasma layer that forms around the vehicle, such plasma layer is the so-called "plasma sheath". 1 The plasma sheath that covers hypersonic vehicles causes the communication "blackout". To avoid this communication "blackout", many studies have been conducted, such as simulation of plasma flow, 2 techniques to reduce the electron plasma density, 3-5 and the mechanism of utilizing the propagation of electromagnetic waves. [6][7][8] In the actual reentry process, the vehicle has a certain angle of attack. The influence of different angles of attack (AOA) on the flow field around hypersonic vehicles has attracted significant attention. Lin et al studied the structure of the near wake flow of a hypersonic reentry vehicle and the resulting base pressure and heat transfer. 9 Torrez et al developed a control-oriented scramjet engine model that was exercised to predict the sensitivity of the thrust with variations in the Mach number and angle of attack. 10 Salmasi et al studied the influence of the existence of a plasma actuator on the passing flow at poststall AOA through numerical simulation and experiments. 11 Huang et al investigated ...

show abstract

“…As indicated in the technical note Ref. [26], at the rear of the vehicle, where the telemetry and navigation antennas are located, the variations in electron density distributions normal to the vehicle surface are considerably larger than the variation transverse to the surface. Thus, the normal component is critical for the present study.…”

Section: Reentry Plasma Sheath Conditionsmentioning

confidence: 98%

Influence of Plasma Pressure Fluctuation on RF Wave Propagation

Liu

Bao

et al. 2016

Plasma Sci. Technol.

View full text Add to dashboard Cite

Pressure fluctuations in the plasma sheath from spacecraft reentry affect radiofrequency (RF) wave propagation. The influence of these fluctuations on wave propagation and wave properties is studied using methods derived by synthesizing the compressible turbulent flow theory, plasma theory, and electromagnetic wave theory. We study these influences on wave propagation at GPS and Ka frequencies during typical reentry by adopting stratified modeling. We analyzed the variations in reflection and transmission properties induced by pressure fluctuations. Our results show that, at the GPS frequency, if the waves are not totally reflected then the pressure fluctuations can remarkably affect reflection, transmission, and absorption properties. In extreme situations, the fluctuations can even cause blackout. At the Ka frequency, the influences are obvious when the waves are not totally transmitted. The influences are more pronounced at the GPS frequency than at the Ka frequency. This suggests that the latter can mitigate blackout by reducing both the reflection and the absorption of waves, as well as the influences of plasma fluctuations on wave propagation. Given that communication links with the reentry vehicles are susceptible to plasma pressure fluctuations, the influences on link budgets should be taken into consideration.

show abstract

Reflectometer plasma diagnostics on a 25,000 foot per second reentry experiment

Cited by 9 publications

References 0 publications

Using a helicon source to simulate atmospheric re-entry plasma densities and temperatures in a laboratory setting

Using a helicon source to simulate atmospheric re-entry plasma densities and temperatures in a laboratory setting

Impact of angle of attack on plasma flow and electromagnetic wave propagation around hypersonic vehicles

Influence of Plasma Pressure Fluctuation on RF Wave Propagation

Contact Info

Product

Resources

About