Polzin, K. A.

Sankaran, K.

NASA Technical Reports Server

Inductive Pulsed Plasma Thruster Model with Time-
E l ti f E d St t P tivo u on o  nergy an  a e roper es
19th Advanced Space Propulsion Workshop
K t P l iur  o z n
NASA-Marshall Space Flight Center
Kamesh Sankaran
Whitworth University
https://ntrs.nasa.gov/search.jsp?R=20130001785 2019-08-30T23:40:22+00:00Z
Inductive Pulsed Plasma Thrusters
• Energy stored in capacitor banks
• High current switch(es) permit discharge through an 
inductive coil
• Fast-rising current ionizes/electromagnetically 
accelerates gas
• Pulsed Inductive Thruster (planar IPPT)
• Since 1980 1 m diameter Exclusively  – -   ,  
pulsed gas injection
• Since 1990s – Marx generator spiral     
configuration, current IPPT SOA 
2
Model / Motivation
&
• No self-consistent, time-dependent Te
3
Lovberg  Dailey, PIT Primer, 1994.• No gas-dependent properties
Modified Model
Circuit Equations (No Change)
Continuity (No Change)
Momentum
4
Adding Energy Equation
Energy
Net electrical power into plasma
Voltage across plasma
    
Plasma inductance evolution
5
Adding Energy Equation (cont)
Energy
1 2 3 4 5
1
2
Electromagnetic work
Oh i H ti
3
4
m c ea ng
Rate of change of electromagnetic field energy
Power lost accelerating newly-entrained gas
5
    
Net internal power convecting into the current sheet + 
work performed by ambient pressure against the current sheet face
6
Plasma Model
Ionization (Equilibrium – Saha)
Transport (resistivity & collisionality)
7
Plasma Model
Non-Ideal Equation of State Specific Heat Ratio
Sheet Thickness
Plasma Resistance
8
Results I
From top to bottom
• Kinetic and thermal energy increase 
early and level off (decoupling)
e
 
m
a
t
c
h
i
n
g
• Magnetic field energy oscillates, 
returning to zero at the end of the first 
half-cycle
m
i
c
 
i
m
p
e
d
a
n
c
e
• Shorter half-cycle in the poorer-
matched case
o
o
r
e
r
 
d
y
n
a
m
• Energy shifts from kinetic to 
thermal/internal mode as mass bit 
P
9
increases
Results II
• Temperature, plasma density, and pressure
• Increase early (Ohmic heating, multiple 
i i ti t i t fon za on, en ra nmen  o  gas
• Temperature & plasma density
St bili i l t ti (d l d)• a ze n a e- me ecoup e
• Pressure 
D i l t ti ( h t• ecreases n a e- me s ee  
expansion)
• Current decreases in peak value increases    ,  
in ‘half-cycle’ duration
• Asymmetric nature consistent with 
greater electromagnetic work
10
  
Results III
• Isp – good quantitative agreement
• ηt – good agreement in form, magnitude difference 
suspected due to modeling assumptions
• New model
• Shifts optimum α, lowers max achievable ηt 
l ti t E / l d l i l ti
11
re a ve o no -eqn  p asma mo e  s mu a on
Conclusions
• Efficiency has a maximum value as a function of α, consistent with 
previous, more simplified IPPT modeling 
• For same E0, higher efficiency achieved when the peak coil current was 
lower and more asymmetric, leading to significantly more energy being 
deposited in directed kinetic energy
• For argon, the plasma properties vary early in the discharge.  As the 
h d l d i d h i ls eet ecoup es, ens ty an  temperature reac  approx mate y constant 
values while the pressure decreases through thermal sheet expansion
Qualitatively and quantitatively the results from the model generally•          
compare favorably with performance measurements. Disagreements can 
be attributed to the simplifying assumptions 
12
Acknowledgements
• We acknowledge the contributions to this work of Mr. A.G. Ritchie and Mr. 
J.P. Reneau.
• We acknowledge Dr. Michael LaPointe for providing several helpful 
comments as we conducted this work.
• K. Polzin appreciates and acknowledges the continued MSFC support of 
Mr. James Martin and Mr. J. Boise Pearson.
• K. Sankaran acknowledges the support of the Washington NASA Space 
Grant Consortium.
• This work presently under review for publication in Journal of Applied 
Ph i
13
ys cs


Inductive Pulsed Plasma Thruster Model with Time-Evolution of Energy and State Properties

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server