9. Birkan - Space Propulsion and Power

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AFOSR

AFOSR Spring Review17 March 2011

Program Manager

AFOSR/RSA

Air Force Research LaboratoryDistribution A: Approved for public release; distribution is unlimited. 88ABW-2011-0802



Space Propulsion and Power

Chemical propulsion

Non-Chemical

propulsion(field, plasma, beamed,

electroma netic

: rus , pec c mpu se, ens y spec c mpu se, o a mpu se

What is new?

- -

2

, ,Physics, Chemistry, etc), multi-physics, multi-scale approach to complex

propulsion problems



Space Propulsion and Power Examples of Past Technology Transfer

Rocketdyne, NASA Marshall: jet spreading rates for subcritical and supercritical conditions in a form

amenable for use in liquid engine design codes, resulted from the fundamental studies of Talley/AFRL,

Yang/PSU, Williams/UCSD (2006)

AFRL Space Vehicles: 200 W first US designed, US build Hall Thruster launched on board the TacSat2 onDec 16, 2006 , design based on the fundamental studies of Sanchez (MIT), Cappelli (Stanford), and AFRL

Propulsion Directorate (Hargus)

N

S E

B

Propellant

J e

N

Ions

Cathode -neutralizer

Anode

+ -

+

-

Electrolytic Ignition of Monopropellants (Yetter, Penn State)

3

Propulsion Technology (IHPRT) Phase III - (2005)




Examples of Potential Technology Transfer / Transformational Capabilities

HAN

FGS

•(2010) observed electrolytic decomposition of ionic monopropellant in

microchannel by adding dispersed nano-catalyst (.1% weight graphene

sheets) that will eliminate structural catalyst (Yetter / Penn State)•NASA

•(2010) achieved electrostatic acceleration of the ionic chemical

propellants (AF315A), to be used as dual-mode propulsion

HAN: hydroxil ammonium nitrade

,•IHPRPT, AFSC, SMC

•(2010) Nano-Aluminum Encapsulated with Ammonium Perchlorate

•DTRA, Pharmaceuticals, Cosmetics

• 2009 AFOSR and NASA Launch First-Ever Test

Rocket Fueled by green, Safe Aluminum-IcePropellant

Son (Purdue), Yetter(PennState), Yang(Georgia

Tech

4




most challenging and exciting scientific opportunities acceleration concepts using electric and beamed energy to provide high efficiency,

variable thrust / exhaust velocities (throttleable) , and lifetime

•Understand secondary e lect ron emiss ion at p lasma-w al l inter faces in order acc urate ly model

p asm a s eat s e ec t on t e s eat pot ent a , an t e r e ec t on t e sc arge

charac ter is t i cs , des ign mat er ia ls a t mic ro leve l to opt im ize d ischarge behav ior

•i n a t rans ient , chemic a l ly -react ive , h igh ly magnet ized p lasmas o f po ly-a tom ic prope l lants

understand and red ic t lasma format ion losses, neut ra l ent ra inment to increase thrust

mit igate chemic a l ox idat ion, opt ic a l rad ia t ion, and/or deposi t ion o f conduct ive layer

Understand and Predict flux and energy distributions of natural and propulsion generated

species, and their interaction with the spacecraft surface materials:

-

•i den t i f y absorp t i on charac te r i s t i cs a t nano sca les to p red ic t mate r ia l response , i den t i f y

w ays to cont ro l absorpt ion, sense cont aminat ion, and mi t iga te charge acc umula t ion

, ,

•to c ont ro l com bust ion instab i l i ty th rough nano-sca le des ign o f the prope l lants

•el iminate s t ruc tura l c a ta lyst fo r monoprope l lants , use same prope l lant in chemic a l and

e lec t r i c ro u ls ion dua l-mode

5

AFOSR workshop on “Materials and Processes Far From Equilibrium” 3-5 Nov 2010

Birkan, Sayir, Luginsland, and Harrison



Design m ater ia ls a t m ic ro leve l to opt im ize d ischarge

behav ior and m i t igate eros ion in thr us t ers v ia m odel ing

secondary e lec t ron em ission a t p lasma-w al l i nt e r fac es

Debye Sheath: interface between a plasma to a solid surface or another plasma with different characteristics

(double layer), properties depends on the plasma characteristics and wall material

•As the secondary electron emission (δ) increases, the potentialx=Lx=0

rop across e s ea ecreases, over a w e range o e ec ron

temperatures

-50

0

[ V ]

i

Ie

Transmitted Electron current-150

-100

S h e a t h P o t e n t i a l

SEE PresentNo SEE

Onset of space-charge-saturatedsheath,

Reduced sheathpotential due to SEE

Reflected Electrons

P asma

Φwall<0

Wa

-

403020100

Electron Temperature [eV]

δ is secondary Electron yield coefficient

Φ=0λ =δIe

cu r ren t

Φ=Φwall

No secondary electron emission

secondary electron emission

,

• increase thruster lifetime through reduced sheath

energies, and increase ionization efficiency through

regulation of electron temperature

•reduce thruster efficiency by allowing higher electron

6

Gridless Electrospray Thrusters : use

sheath as ‘virtual electrode’ to extract liquid spray

power losses to the walls and enhancing electron leakage

current to anode



Single Shot Electrodeless Lorentz Force Thruster Operation

Successfully DemonstratedSlough / Kirtley/ Milroy (MSNW/ University of Washington), Rovey (YIP-Univ. of Missouri)

Cambier, Haas, Brown (AFRL/ RZSS)

•Field Reverse Configuration used to create Plasmoids in fusion community, combined with Rotating

Magnetic Fields, promise a breakthrough in high power (1 kW and up) variable thrust space propulsion

Antenna

Field Coil

npu ower = - s ea y s a e

Propellant = Air, Argon, Xenon, Nitrous Oxide

Measured Thrust impulse = 1mN-s per plasmoid ejection

Measured Specific Impulse = 1,000-6,000 s

• -

Goal: optimize this concept to obtain high performance with accepted lifetime

through understanding of the fundamental physical processes and their

7New Collaborators: AFRL/RZSS, NASA, DARPA



Fundamentals of the Electrodeless Lorentz Force Accelerator

Wire current

I I -

2B

I

(out of the

page)

B B B

Surfacecurrents(into thepage)

Ideal conductor (B=0)

Increased B field region

8





Fundamentals of the Electrodeless Lorentz Force Accelerator RF antenna produces oscillating transverse m=1 mode where electrons

couple to the component rotating in the electron drift direction

Duration < 1 s

B

V0sin(t)

B

V cos t

10



Fundamentals of the Electrodeless Lorentz Force Accelerator Rotating magnetic field induces large azimuthal current (10s of kA) and

mirror surface current in opposite direction at wall•J induced in opposite direction on the conducting walls (“flux straps”)

•B-fields outside of FRC add up (increased magnetic pressure)

•B-field inside plasma is in reverse direction ( = Field Reversed Configuration)

B Bbias

B+

+

+ + ++

e-

J-FRC (due to rotating magnetic field)

e-e-

e-

e-e-

J wall (mirror current)

FUNDAMENTAL ISSUES:

11

•Ionization, and energy stored in the excited states, subsequent optical radiation from the excited states

•Is there any ion impingement to the walls, any potential sheath formation near the walls, if it is, what arethe characteristic time scales of each event including ion drift ?



Fundamentals of the Electrodeless Lorentz Force Accelerator

The result is a well confined, closed field plasmoid (FRC) in equilibrium with an

external field now many times larger than the initial bias field

RMF generated

plasma current

from synchronous

electrons

Duration < 15 s

rz B jF J

Steady magnetic

field due to

solenoid +transient

Net

Acc.

Force

magnetic field due

to FRCLarge Plasma Azimuthal

Current

Total Field Gradient

Expanding section converts some

thermal energy into kinetic energy

•Ohmic and Turbulent (MHD) heating, and its effect on optical radiation

•Radiation losses: time-dependent distribution of atomic states and ionization stages

12

• What is the critical residence time of plasmoid in the thruster to convert thermal

energy to axial kinetic energy (optimal expansion)?



Neutral Entrainment

Can we Increase thrust to power ratio by entraining and accelerating

neutrals without ionization and plasma formation losses ?

. orm an w

2. Add more neutral propellant in front of it3. Entrain the propellant through mostly charge

exchange collisions

. ne c energy w pu se magne c e s

•Can dramatically (x10) increase T/P,

not the whole mass

•The concept could potentially be

used for air-breathing

neutral

FUNDAMENTAL ISSUES:

•

13

,

• What is magnitude of additional losses when entraining neutrals?



Space Propulsion and Power gearing up/winding down

acceleration concepts using electric and beamed energy to provide high efficiency, variable thrust / exhaust velocities (throttleable)

, and lifetime

•Understand secondary electron emission at plasma-wall interfaces in order accurately model plasma sheaths (effect on the sheath potential), and their effect on the discharge characteristics, design materials at micro level to optimize discharge behavior

Understand and Predict flux and energy distributions of natural and propulsion generated species, and their interaction with the

•in a transient, chemically-reactive, highly magnetized plasmas of poly-atomic propellants

understand and predict plasma formation losses, neutral entrainment to increase thrust mitigate chemical oxidation, optical radiation, and/or deposition of conductive layer

novel energetic materials based on nanoscale particles, energetic additives, and dispersed nano-catalysts

spacecra sur ace ma er a s:

•identify absorption characteristics at micro scales to predict material response, identify ways to control absorption, sense contamination, and mitigate charge accumulation

•to control combustion instability through nano-scale design of the propellants

•to discover chemical and electrolytic pathways that will eliminate structural catalyst for monopropellants, use same propellant in chemical and electric propulsion (dual-mode)

Plume signature: rarified flows with chemistry, radiation

Laser Pro ulsion and Electroma netic launchers: MURI ended

14Thank You for your Attention !!





Quantitative prediction of injector jet spreading rates for

subcritical and supercritical conditions used to validate codes,

such as the Rocketdyne engine design code for SSME Block-II

Experimental shear layer structureSingle element injector simulation

Subcritical Transition Super-critical

bg >> bg = bg <<

0 27 [ ( /( )) ( / )0 5

]

characteristic turbulent bulge formation time

0.27 [ (b/(b+ g)) + (g/l)0.5

]

characteristic gasification time

16

Talley/AFRL, Yang/PSU, Williams/UCSD



Simulate full scale effects at small scales

A HYBRID (Experimental + Theoretical ) Approach for elucidating

complex combustor dynamics (closed-loop actively controlled)

Boundary conditions=f(r,t)

Experimental domain

Control signal to theactuator that determines the

velocity of the actuator’s

CONTROLLER: Uses an a roximate anal tical solutionRD-0110 Injector Layout

MeasuredMeasured

Pressure oscillationPressure oscillation

p’(t)p’(t)

to compute the effects of acoustics and oscillatory

combustion in the “remainder/computational” domain

91 swirl coaxial

injectors

17Computational domain=“Remainder” of engineComputational domain=“Remainder” of engine



OSR Funded MIT Hybrid Particle-In-Cell model (1996-

2000) helped to resolve 200 W Hall Thruster erosion and

efficiency problems, flew on TacSat-2 (2006)

•Hybrid Particle-In-Cell simulation tracks ions as particles, electrons as fluid

Outer

Exit

Ring

Near Field

Nose

Cone

Axis

R

Ion flux to walls high at nose cone, causing high losses, erosion

18

•Discharge zone moved to downstream through improved magnetic topology including magnetic shunt

•Result is 200W Thruster with 43% efficiency, 1375 sec specific impulse, estimated 1800 hr lifetime

Szabo, Fife, Sanchez (MIT), and Busek Co



It may be possible to eliminate structural catalyst

through the use of dispersed nano-catalyst

• Functionalized graphene sheets (FGS) have been dispersed in HAN+H2O mixture (0.1% weight),

• Thermal gravimetric analysis and differential scanning calorimeter show onset of reaction lowered by

o

HAN+H2O HAN+H2O+0.1% (weight) FGS

TG

1002.5

3

1005

6

TG

40

60

1

1.5

2

40

60

80

2

3

4

DSC0

20

-0.5

0

0.5

20 30 40 50 60 70 80 90 100

Temperature / oC

0

20

-1

0

1

20 30 40 50 60 70 80 90 100

DSC

Tem erature / o

C

HYPOTHESIS:

NH3OH+NO3-(liq) NH2OH(g)+HNO3(g) (Ea~15kcal/mol and Hr = +38kcal/mol)

replaced with the desorption reactions

Curser for thermal decomposition reaction

HAN

19

6NH3OH+NO3- 3N2(g) + 2NO(g) + 10H2O(g) + 4HNO3(g) (Hr = -28 kcal/mol)

•Needs molecular dynamics and quantum chemical calculations to

understand FGS surface dynamics

FGS



Propulsive performance measurements of HAN+HEEN

from time-of-flight experiment is very promising at near

purely ionic regime

AccelerationElectrode

charged

ExtractionElectrode

ions

par c es

Conductive

Liquid

e n t

Tip OD ≈ 100 m

Taylor Cone

v e c o l l e c t e d c u r

b u t i o n ,

I c ( t ) [ n A ]

emitter-tip voltagerelative to extractor=1756 V

Parameter No post-acceleration 10 kV post-acceleration

Mass Flow Rate, ṁ [10-12 kg/s] 0.58 0.58

Thrust, T [nN] 19.5 46.5

C u m u l a t

d i s

t r

Emitted spray current =250 ± 10 nA

Pressuredifferential=25 Torr

Specific Impulse, Isp [s] 3425 8172

Propulsive Efficiency, [%] 74.6 74.6

20

,

•Ethyl ammonium nitrate is better choice for electrosprays, because it is in liquid state, however harder to ignite in

chemical propulsion and lower performance, mix with methyl ammonium nitrate ?



Nano-Aluminum Encapsulated in

Ammonium Perchlorate via crystallization

•approach is to use a surfactant that coats the nanoparticles and creates more

effective nucleation sites for the crystalization

•the method of capture of a nanoparticle in a polymer micelle

a dis ersion b ca ture c cr stallization

•Schematic of final micelle-based crystal

•Enca sulated nano aluminum in AP

21



Encapsulated Al particles may eliminate

Slag Problem

• We hypothesize that encapsulated Al particles will release more readily from the surface that

ignite and burn in a more oxygen rich environment

– This would result in fewer coalesced articles at the surface leadin to smaller

agglomerates, improved combustion efficiency, and less slag

Classsical nano/micro Al burning Encapsulated nano/micro Al burning

Al burning

Encapsulated Al

22



Al and Water reactions have been studied for decades, why was

it unsuccessful then, what may make it successful now ?

Answer: Nano-Aluminum Particles

Al203 , Tmelt 2300 K

Tmelt 1000 K

•Ignition was a problem with previous liquid water and aluminum

propellants using micron sized particles (Tign~ 2300 K).

• ˜˜

as 1000 K) and lower ignition energies.

•Since the aluminum water reaction is generally considered a heterogeneous reaction,

the alumina product size scales with initial particle size, and slag accumulation was a

•Previous s stems were non- remixed leadin to article in ection mixin and flame

problem.

•Nano particles lead to smaller sized final product alumina particles (implying

lower drag and less two-phase flow losses).stability problems (used particle injectors, vortex, and linear chambers, all failed )

•Composite quasi-homogeneous mixtures of nano-aluminum and water (ice)

eliminate these issues.

•In order to maintain high reaction rates, the combustors were operated close tostoichiometric and even fuel-rich (needed to inject extra water that quench the flame).

•Nano particles have higher burning rates and high conversion efficiency in

23

References:

•T.G. Hughes, R.B. Smith, and D.H. Kiely, Journal of Energy 1983, vol.7 no.2 (128-133);

•Kiely, D. H., AIAA 94-2837;•J.P. Foote, J.T. Lineberry, B.R. Thompson, Winkleman, AIAA 96-3086•T.F. Miller, T.F., J.D. Herr, AIAA 2004-4037



Multiscale Approaches to Controlling Surface

Absorption and Contamination

25% cells lost due

to hydrazine

residue deposits(1) predict and measure

above the surface (kinetic)

order of mm-meters! At/below the surface(molecular):

order of nanometers! Provide sticking

probabilities, residence

Provide ion and neutralvelocity distribution

functions

times, erosion rates

as a func. of T,

composition, velocity

10-9 mDensity functional theory calculation (quantum )

order of angstroms! Re-adjust potential field based

on energy distribution of electrons

Use atom probe tomography to determine role of neutral and ion

24

10-10m





BACK-UP VIEWGRAPHS

26



Annular Supersonic Air Inlet in Hypersonic Air-breathing Mode of Combined-Cycle LP Engine

Transition to Hypersonic Regime:

con ca ow s oc orms over e

nose, which functions as an external

compression airbreathing inlet, driving

compressed air into the annular inlet.

In the hypersonic regime, air enters the

annular inlet slit at supersonic speeds,

refreshing the annular laser absorptionc am er.

Cross-section of Lightcraft

engine showing supersonic

27

propulsion mode.



Laser Pulsed Detonation Engine CycleAFRL/PR(Mead), RPI(Myrabo), DLR (Schall), NASA (Wang)

Refill ~ Scavenging(190 - 1000 sec)

Annular focus in shroud>107 watts/cm2 air breakdown

(0.4 – 1.2 sec ) for 10.6 m laser

0.5-1.0 mm

shroud

at subsonicspeed Pulsed Laser beam

(18 sec)

Laser-Supported Detonation

(12-18 sec)

(1 – 12 sec)

Blast Wave Ejection(18 - 190 sec)

Laser-Supported Deflagration

Mmax = 2.8

28



Flow Regimes for Laser Propulsion Experimental Flow Regimes for Laser Propulsion Experimental Research Research (Mach No. vs. Altitude)(Mach No. vs. Altitude)

•LP experimental research is conducted in three airbreathing flow regimes:

- Hypersonic LP Experiments at the Henry T. Nagamatsu Laboratory of -

- Subsonic , and Supersonic (Mach 2 to 3+) LP Experiments at RPI.

•H ypersonics research will identify Mach # for transition to laser rocket mode.

401.2

Laser Launch Initial Trajectory (with Mach 0.6 “pop-up” to 12.5 km)

Hypersonic

(Brazil)Supersonic

(RPI)

Subsonic

(RPI)

25

30

( k m )0.8

1

[Rocket ModeTransition @

n s i t y ( k g / m 3 )

10

15

20

A l t i t u

d

Density

0.4

0.6 ac - D e

290

5

0 1 2 3 4 5 6 7 8 9 10Mach #

Altitude

0

0.2



Instability is one of the most complex

phenomena in liquid rocket engines

•In a High Pressure/Temperature, Two-Phase, Turbulent, Acoustically – Excited Environment, investigate

Amplification

•High amplitude and high frequency acoustic instabilities can lead to local burnout of the combustion chamber walls and

injector platesnjector plates

Subcritical Processes:

Jet Break-up

Atomization

Vaporization

Combustion (effect of chemistry?)

High pressure combustion (supercritical regime) is a two-edged sword:

•Performance and Thrust/Weight advantages•Higher energy density increases risk of combustion instability

Supercritical regime gas-like processes offers new opportunities

30

•Simulate High Pressure supercritical combustion using gas-gas simulants

•Injector damping made possible by gas-like behavior of supercritical processes



Stabilize the liquid engines using energetic additives and nano-particles

Cryogenic H2 –fueled engines are more stable than storable

hydrocarbon-fueled rocket engines, WHY?

•Faster Reaction rates (Flame Speeds) stabilize the engine

Average heat release rate

Experimental (Anderson / Purdue) numerical (Merkle / Purdue)

‘Fast’ CombustionFlame anchored

on the splitter plate

H2/LOX

Finite-rate

Combustion

Flame anchored on

Methane

/LOX

recirculation zone

RESEARCH:

31

•Can a practical hydrogen carrier be developed for use as an additive to hydrocarbon fuels to increase combustion

rate (flame speed)?

•How can chemistry and fluid mechanics (mode shape and mixing) be combined to result in a heat release

distribution that is steady and resistant to pressure oscillations in the chamber?"

Liquid Engine Combustion Instability




An example of Individual Scientific Problem: Injector Dynamics

Waves Generated by a Swirling Oxygen Jet

breakup lengthkerosene

Russian RD-0110 engine (SOYUZ third stage

liquid engine) swirl coaxial injector • Model is based on full conservation laws and accommodates real-fluid

thermodynamics and transport phenomena over the entire range of

fluid states from subcritical to supercritical

liquid oxygen

swirl

cone

angle

gas core

• ur u ence c osure roug arge e y mu a on, u -gr -sca e

motions treated by Smagorinsky eddy viscosity model

• Axisymmetric, flow variations in the azimuthal direction neglected

Tangential 02 inj.

Tinj= 120 KT

= 300 K

= 10 MPa

recirculating flow near the injector exit

Seven Different Wave Motions Identified (Yang / Georgia Tech)

5 mm

gaseous core

hydrodynamic waves

surface

instability

recirculating

32

w n m

Kelvin-Helmholtz instabilityTemperature Field





An example of Individual Scientific Problem: Injector Dynamics

Data Analysis

. a

30Probe 9

Spectral analysis: provides the frequency content at a single point, does not provide the spatial structure, or

driving mechanism of an instability mode.

a20

300.55 Probe 1

p ' ,

k

0 5 10 15 200

103.9

1.04

Frequency, kHzHydrodynamic wave speed 10 m/s

p ' ,

k

0 5 10 15 20

0

10 3.151.04

14.0

Travel time 2 ms

hydrodynamic waves within LOX film0.5 KHz

1/4 wave resonator natural frequency

f = c/4L + l

acoustic waves

3.2 KHz

Corresponds to the

Kelvin-Helmholtz

interfacial

Frequency, kHz

Proper Orthogonal Decomposition technique: determine the spectral (frequency) content and spatial

structure of each instability mode over a given spatial domain and the driving mechanism of each instability mode.

ow proper y

9

9

33

:

•One must account for the Kelvin-Helmholtz wave motion and the acoustic waves as the boundary

conditions for the chamber dynamics simulation •One must account for the hydrodynamic waves in LOX film in the injector design



L dd Si l ti Di t



Large eddy Simulation vs Direct

Numerical Simulation

• Jet injection in supercritical-pressure turbulent flows exhibit ‘finger-

like’ features absent at subcritical pressures

‘ ’

LESmodeling

- ,

production/damping

may requ reto account

specificphysics

(Talley/RZSA) Sub-Grid Model: new termsin equations are needed todescribe the observationsO 500,000 rid oints

DIRECT NUMERICALSIMULATION

O(20 million) grid points

35

Bellan / Caltech funded by AFOSR(Birkan), RZSA(Talley), RZTG (Edwards), and

RZAS(Carter)

Li id E i C b ti I t bilit bl



Liquid Engine Combustion Instability problem:

to obtain approximate solutions are the key to real-time control

P= P(mean)+ P’(small perturbation) ),,( / ' / ')'( 22222 NLQ M f xPC t PP L

~’

Nonlinear partial differential equations

application of Perturbations and Galerkin techniques:

i iix1 Known Eigen-

functions (acoustic

modes of chamber)Unknown time

dependent amplitudes

0)(),(0

L x

x idx xt x L

EE orthogonal condition

,

)],,(),(

~

([ NLQ M f t xP L E Error

, ,

• Condition that the error E be orthogonal to all the N chosen eigenfunctions yields a system of N nonlinear

ordinary differential equations which is much faster to solve analytically and/or computationally

Inhomogeneous part = f (mean flow, combustion oscillations, non-linear terms like convection)

If M<<1, mean flow

effects are negligible

Iterate Process to Increase accurac

Q’ is a second order effectlike Mp’, or Mu’

Nonlinear terms is a secondorder effect like (u’)2

First Iteration(f=0)First Iteration(f=0)Consider the effect of

acoustics only in

computational domain

Second Iteration f = f(Q’ only)Second Iteration f = f(Q’ only)Add the effects of “uniform” propellants

injection/combustion in the

computational domain

Third Iteration f = f(Q’, NL)Third Iteration f = f(Q’, NL)Add the effects of “non-uniform”

propellants injection/combustion and

nonlinearities in the computational domain

36

Developed a smart fuel injector to actively



Developed a smart fuel injector to activelycontrol instabilities in liquid rocket engine

Controlled

spray pattern

Outer

swirler

var

Inner

swirler

Demonstrated the excitation of 5000 Hz. Tan ential

Liquid fuel

instabilities in an atmospheric pressures

1.20

1.30

1.40

LLID: 101207_01_T73

r a t i o

Diverter

control

valve Air 0.90

1.00

1.10Stable

operation1T1T

i v a l e n c

37

ZINN / GEORGIATECH0.70

0.80

40 50 60 70 80K = PINR /POUTR

E q

Are the baffles in the liquid engines



Are the baffles in the liquid engines

overdesigned?

•A very short, L=.1D “asymmetric” baffle completely damped thetangential instability

F1 engine injector head with baffles

No Baffle: Spinningtangential Instability

Short Baffle (L=.1D):stable operation

38

•Changing the length of the baffle changes the amplitude, frequency andmode (i.e., standing vs. spinning) of the instability

Dual-mode operation (Space Situational Awareness)



p ( p )

Microchemical Propulsion with Ionic Monopropellants

(Electrospray thruster will run on the same propellant)

•Fabrication of micro, 3-dimensional, uni-body thrusters from ceramics using stereolithography techniques

• Combustion of AF315 and nitromethane from 1 – 40 atm

•electrolytic Ignition (Yetter / Penn State)

• Chemical efficiencies over 99%

5 mm

WhiteDecomposition

GasTeflon

Seal/Isolator

Feedthrough

AssemblyDecomposedGas

Ignition of AF315

GasOutlet

Liquid PropellantInlet

oElectrodeCasing

500mGap Spacing

Liquid Propellant

oElectrodeIgniter

CasingGas

Outlet

O.D.: 1.59 mmI.D. : 1.0 mm

Gas ExitGas Exit

Transferred to the AFRL / RZ to beused for Monopropellant Thrusters(IHPRIT roadmap)

•CH3NH2+-NO3

- Methylammonium Nitrate is one

of the energetic ionic propellant candidate

39

Payoff to Air Force: development of high performance thrusters for microsatellites with minimal power requirements

and “green” monopropellants

Center of Excellence-Univ. of Michigan

G idl El t Th t f l ‘ i l



Gridless Electrospray Thrusters : use surface plasma as ‘virtual electrode’ to extract liquid spray

King / Michigan Tech – Levin/PennState

Current State-of-the-artHypothesis : When a gaseous plasma contacts a solid surface a thin

layer of charge imbalance forms in a ‘sheath’ next to the surface.

•Can the electric field in the sheath be made strong enough to

Electrode surface

CHALLENGES:

• Delicate microfabrication is required

• Difficult to align a million holes with a million tips

• , ,

RESEARCH:

40

• ompu a ona an exper men a s u y o un ers an :

•Coupling between plasma sheath strength and

electrospray production

Documents

9. Birkan - Space Propulsion and Power