Physical Sciences Inc. 20 New England Business Center Andover, MA 01810

VG06-206

Plasma Sheathing Control Using Boundary Layer Stabilization and Additives

Hartmut H. Legner, John F. Cronin and W. Terry RawlinsPhysical Sciences, Inc., Andover, MA

Substitute Speaker: Dr. Robert F. Weiss, Physical Sciences Inc.

Paper Presented atAFOSR Workshop on Communications Through Plasma

During Hypersonic Flight

29 August 2006, Boston, MA

Acknowledgement of Support and DisclaimerThis material is based upon work supported by the United States Air Force under Contract Number FA8718-05-C-0054. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the United States Air Force.

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VG06-206-1

Acknowledgment and Note

• This Phase I SBIR effort was sponsored by two AFRL organizations: SNHE and VAAC, with additional interest from a third organization: VSBXT

• The technical monitor is Dr. James Ernstmeyer of AFRL/SNHE at Hanscom AFB, MA

• Special note: This presentation provides a general overview of potential sheathing solutions. Specific results and designs have SBIR rights and ITAR restrictions. The detailed report can be obtained from Dr. Ernstmeyer.

VG06-206-2

Outline

• Plasma sheathing control objectives

• Three techniques– Boundary layer stabilization by extreme cooling– Liquid injection into boundary layer flow– Electrophilic material in heat shield material

• Application to hypersonic vehicles

• Summary

VG06-206-3

Plasma Sheathing Control Objectives

• Control sheathing via temperature and chemistry

• Reduce electron density, ne

• Reduce boundary layer thickness, δ

ShockWave

. .... .. . ..

.....

. .. .Heatshield Dust

Injection

Boundary Layer

HydrideMaterial

Antenna• Reduce ne• Reduce δ

H-9935

VG06-206-4

Plasma Sheath Attenuation ReductionBRV, 50 kft, ne = 1.8 x 1012/cm3, 0.130 atm, νc = 1.3x1010 S-1

Boundary Layer Thickness Reduction7x101

Frequency, ghz

delta=1.4 cm

delta=1.2 cm

delta=1.0 cmdelta=0.8 cm

delta=0.6 cm

Atte

nuat

ion,

db

6x101

5x101

4x101

3x101

2x101

1x101

00 1 2 3 4 5 6 7 8 9 10

G-9836a

L S Band X Band

VG06-206-5

Plasma Sheath Attenuation ReductionBRV, 50 kft, Delta = 1.4 cm, 0.130 atm, νc = 1.3x1010 S-1

Electron Density Reduction

0.001

0.010

0.100

1.000

10.000

100.000

0 2 4 6 8 10 12Frequency, ghz

Atte

nuat

ion,

db

1.80E+121.00E+111.00E+101.00E+09

H-9940

L S Band X Band

ne (cm-3)

VG06-206-6

Extreme Surface Cooling Using Hydride Materials

• Extreme cooling stabilizes hypersonic boundary layer– Secondary mode unstable at high edge mach number– Remain below Me2nd mode for laminar flow

• Hydride cooling works over a large range of heating conditions– Amount of hydride (material thickness) controls “cool time”

• Hydrogen gas released during low-temperature ablation process– 15-20 kJ/gm H2 , heat of desorption (and adsorption)

Hydride cooling works over wide range of trans-atmospheric flight conditions

VG06-206-7

Hydride Cooling for Typical Surface Heating Flux50 W/cm2

Computations performed using PSI’svalidated thermal response code

VG06-206-8

Cooling Stabilization Boundary forTrans-atmospheric Trajectory Points

Hypersonic VehicleTrajectory

Hypersonic VehicleTrajectory with5 Deg Change

Me2

Second Mode(No Cooling Stabilization)

Cooling Stabilization

104 105 106 107 108 109

8

7

6

5

4

3

2

1

Edge

Mac

hN

umbe

r,M

e

Location-based Reynolds Number, Rex H-7446a

VG06-206-9

Liquid Injection

• NASA RAM C-III Flight Experiment 1973– ne(cm-3) at boundary layer standoff distance 4 cm, 71-72 km altitude

• No injection: 3.9x1010

• Water: 4.8x109

• Freon-3: 3.8x108

– Blunt vehicle, Teflon frustum, 5000 ppm alkali impurities, pulsed injection

• Employed Non-equilibrum Boundary Layer (NEBL) code to compute effects of injectant on downstream electron density– Same trans-atmospheric flight conditions as hydride– Instantaneous vaporization– 50 ppm alkali in carbon phenolic heatshield– Wall cooling effects

Water injection showed insignificant effects, but Freon-3 resulted in orders of magnitude ne reduction depending on boundary layer cooling

VG06-206-10

Freon Injection Cases

Freon Injection, 1,0.8,0.55 PRAE 8

1.0000E+00

1.0000E+01

1.0000E+02

1.0000E+03

1.0000E+04

1.0000E+05

1.0000E+06

1.0000E+07

1.0000E+08

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18Y, cm

Ne,

e/cc

No InjectionFreonTwall*0.8Twall*0.55

H-7298

ne(cm-3) T(ok)

Freon Injection, 1,0.8,0.55 PRAE 8

1000

1500

2000

2500

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18Y, cm

T,K

No InjectionFreonTwall*0.8"Twall*0.55

H-7299

VG06-206-11

Heatshield Electrophilic Scavenging Computations

• Electrophilic particles take up electrons efficiently by the reaction

P + e- P-

• Applied heterogeneous chemistry model, Caledonia (1986)– Electrophilic specie concentration (ppm)– Particle size (Å)– Work function (eV)– Temperature (K)

ka

kd

VG06-206-12

Electron Density Reduction

20 Å, 5eV

1.00E+05

1.00E+06

1.00E+07

1.00E+08

1.00E+09

1.00E+10

1.00E+11

1.00E+12

0 20 40 60 80 100 120 140X, cm

Ne,

e/cc

Base 1 ppm 10 ppm 20 ppm 30 ppm

H-8603

Large potential sheathing reduction usinglow concentration of electrophilic material

VG06-206-13

Vehicle Application

None, small if injectedSmallVery small• Power Impact

Very smallModestSmall• Weight Impact

Very smallModestSmall• Volume Impact

Design

Compatible, distributed in heatshield or injected

CompatibleCompatible

Compatible, distributed in heatshield or injected

CompatibleCompatible• Waverider

• Bi-conic

Configuration

Some velocity dependenceContinuous or pulsed

Some velocity dependence5-20 s, pulse

Velocity dependent5-20 s

• Velocity• Time

Altitude History

ContinuousMultiple control applicationsMultiple applications

ContinuousMultiple control applicationsOne-time control• Weapon

• Surveillance

Missions

Incorporation ofElectrophilic SpeciesAdditive Injection

Boundary LayerTransition Control

Plasma Sheathing Control Techniques

Requirements

VG06-206-14

Summary

• Three general techniques to control plasma sheathing have been identified.

• All three schemes are potentially viable for application to hypersonic cruise vehicles.

• Experimental validation and multi-phase modeling simulations are needed to pursue this promising technology further.

Backup Charts

VG06-206-16

Metallic Hydrides

Heats of Desorption (and Adsorption)

• High energy, low temperature ablators

H2 Flow as a Function of Heating Rate for LaNi5H6

H2 Pressure Above LaNi5H6 (—) and (V0.89Ti0.11 )0.95Fe0.05Hx(•–•)

• Transition metal hydrides– AxBl-XHy type compounds– decompose rapidly and endothermically

to produce H2

AxBl-x Hy → AxBl-x + y/2 H2

LaNi5H6 = LaNi5 + 3 H2 ∆H = 15.1 kJ/gm H2

and(V0.89Ti0.11)0.95Fe0.05Hx, = (V0.89Ti0.11)0.95Fe0.05Hx-1 + 1/2H2 ∆H = 21.5 kJ/gm H2

140

120

100

80

60

40

20

00 20 40 60 80 100 120 140 160 180 200

Heating Rate (watts/cm2) D-1302

H2

Flow

Rat

e(s

ccm

/cm

2 /se

c)

1000

100

10

1

0.1

0.01

0.001

0.0001200 220 240 260 280 300 320 340 360 380 400

D-1303Temperature (K)

Pre

ssur

e(a

tm)

VG06-206-17

Boundary Layer Models

• Non-Equilibrium BL (NEBL) Code– implicit, fully-coupled model– unique chemistry models

• TURBL– 8 equation turbulence model– temperature fluctuations mirror plasma

behavior• REACH (developed by SAIC)

– 3D BL Code

F-

NO+COF+

ElectrostaticProbe Data

NA+

NA+

eNEBLSolution

NO+

COF+F-

105

104

103

102

100 0.2 0.4 0.6 0.8 1.0

X/L

Pea

kE

lect

ron

Den

sity

(Arb

itrar

yU

nits

)

A-7921

InviscidFlow Field(2IT/3IS)

CaseInputs StreamtubeShock Layer

p

B.L.Code

(NEBL)

Inviscid ShockLayer Species

Electron ProfilesCaseInputs

CaseInputs Ablation

(CMA)

m, TwQ

A-368

NEBL Calculation

NEBL Methodology

REACH Simulation1014

1013

1012

1011

1010

109

1080 10 20 30 40

Time (s)

Elec

tron

Den

sity

(#/c

m3 )

D-4163b

Windward

Leeward

α ~ 4 deg~

TeflonRMV-340131 kft

VG06-206-18

Water Injection Cases

ne(cm-3) T(ok)

Water Injection, PRAE 8

1.0000E+05

1.0000E+06

1.0000E+07

1.0000E+08

1.0000E+09

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16

Y, cm

Ne,

e/cc

No InjectionWaterWater, Twall*0.8Water, Twall*0.55

H-7296

Water Injection, PRAE 8

1000

1500

2000

2500

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16Y, cm

T,K

No InjectionWaterWater, Twall*0.8Water, Twall*0.55

H-7297

VG06-206-19

Freon InjectionSynergistic Effects: Hydride Cooling and Injection

0

500

1000

1500

2000

2500

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18Y, cm

T,K

No InjectionFreonFreon, Twall*0.8Freon, Twall*0.55Freon, Twall*0.1

H-9974

1.0000E-02

1.0000E-01

1.0000E+00

1.0000E+01

1.0000E+02

1.0000E+03

1.0000E+04

1.0000E+05

1.0000E+06

1.0000E+07

1.0000E+08

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18Y, cm

Ne,

e/cc

No InjectionFreonFreon, Twall*0.8Freon, Twall*0.55Freon, Twall*0.1

H-9973

ne(cm-3) T(ok)