The Environment Power System Analysis Tool (EPSAT) is being developed to provide space power system design engineers with an analysis tool for determining system performance of power systems in both naturally occurring and self-induced environments. The program is producing an easy to use computer aided engineering (CAE) tool general enough to provide a vehicle for technology transfer from space scientists and engineers to power system design engineers. The results of the project after two years of a three year development program are given. The EPSAT approach separates the CAE tool into three distinct functional units: a modern user interface to present information, a data dictionary interpreter to coordinate analysis; and a data base for storing system designs and results of analysis

Jongeward, Gary A.

Kennedy, Eric M.

Kuharski, Robert A.

Putnam, Rand M.

Roche, James C.

Stevens, N. John

Wilcox, Katherine G.

English

NASA Technical Reports Server

N91-17734
fP
The Environment Power System Analysis Tool
Development Program
Gary A. Jongeward, Robert A. Kuharski,
Eric M. Kennedy, Katherine G. Wilcox
S-CUBED / Maxwell Laboratories
N. John Stevens, Rand M. Putnam
TRW
James C. Roche
NASA/LeRC
Introduction
The Environment Power _3,stem Analysis Tool (F.PSAT) is being developed to provide
space power system design engineers with an analysis tool for determining system
performance of power systems in both naturally occurring and self-induced environments.
The program, which is funded by SDI/SLKT and directed by NASA/LeRC, is producing
an easy to use CAE tool general enough to provide a vehicle for technology transfer from
space scientists and engineers to power system design engineers. This paper presents the
results of the project after two years of a three year development program.
The Strategic Defense Initiative (SDI) systems require the generation of very large power
levels in space for defense applications. These power levels must be available, on demand,
anytime in the 10 year mission life of the system requiting the power system to survive
prolonged exposure to the space environment and then be fully functional. The space
environment interacts with power systems in many ways including: ionization and bulk
breakdown, plasma-induced surface flashover, oxygen erosion, meteor and debris damage,
and radiation effects. Previously, engineers needing to assess the system impact of these
interactions were forced to perform separate calculations and analysis for each interaction
and then attempt to piece the intermediate results together. This made system analysis time
consuming and unreliable and made extensive system tradeoff studies nearly impossible.
EPSAT is being developed to provide engineers of space power systems with system
analysis capabilities. The program consists of four major areas. These are:
(1) Identify the relevant power systems envisioned for SDI applications and determine
which environment-power system interactions are most likely to be important in the
operation of the space systems.
352
https://ntrs.nasa.gov/search.jsp?R=19910008421 2020-03-19T19:37:43+00:00Z
(2) Develop a modem robust CAE tool to provide a natural framework to integrate
newly developed or existing modeling software into a comprehensive analysis tool with
a modem user interface.
(3) Identify existing modeling codes and start development on new codes needed for
modeling environment power system interactions. A separate detailed analysis phase
will follow to determine the accuracy of the analysis codes and relevance of the
interactions to the design of high power systems for the space environment.
(4) Determine deficiencies in modeling capabilities, material properties, etc. relevant
to environment-power system interactions and recommend corrective steps.
EPSAT
A useful CAE tool provides engineers with the necessary design information for the
systems under consideration. While this seems obvious, it places severe requirements on
software design. SDI configurations are still in the conceptual design phase, hence power
system designs, requirements, and planned applications evolve with time. A power system
environment interactions CAE tool must be capable of absorbing changes and extensions
quickly and reliably. To meet this need, EPSAT has been designed for change. The
interface is user friendly and easily modified. The code is highly structured with
calculational modules which can be altered or replaced. New modules can be added to give
new results or build on results from other modules. All facets of the CAE tool, from the
way information is presented to the user to the physical models used in the calculations, are
easily changed. A unique architecture has been used to provide this capability and is
shown in Figure 1.
The EPSAT approach separates the CAE tool into three distinct functional units: a modern
user interface to present information, a data dictionary interpreter to coordinate analysis;
and a data base for storing system designs and results of analysis
353
Screens R tt_at
o.. ..
, •
:! _.._lnterpr,t; t >
.j I'ol  at.
Boreen Definition Data Dlollonery Data Base
Form.Sheath "
x.1 y,,1 v:plsden 1
get@2:gat@3
x-3 y-1 v..athrad 2
x-.1 y.10 v,,athour $
Forn_Ozygen Degre
x-1 y.1 v.den .oxy
x=l y-5 v.vel_oxy
x.S y=20 v,,ersn_rle
Form-Breakdown
Pladen: Orbit Time
sail Envlro(Orbfl..)
Orbit: Time In!vel
ceil Orb{Tlme.lnlvei...)
Sthrad: Plsdan Volt Obj..
oatl Sthrad (Plsden...)
4.26.88.0100 P|aden 1.a10 J
4-28-118-0101 Time 2802 |
4.28-88.0010 Sthrad 3.4 J
4-28-18-O059 Orbit 360 I
.4-28-18.005S. Volt 130000 I
Figure 1. The modern design of EPSAT allows for extension and
change. The user interface presents data to the design engineer through
menus, screens, and graphics. Screen definition files tell the screen
handler which data items are to be displayed on the screens.The data
dictionary interpreter receives data requests from the screen handler and
uses a rule book, the data dictionary, to find recipes to construct the
desired data
The user interface is externally programmable through ASCII data files, which contain the
location and type of information to be displayed on the screen. The information being
displayed to the user can be changed while EPSAT is running. Besides aiding in
development, this approach provides great flexibility in tailoring the look and feel of the
code to meet individual user's needs. The user interface has utilities for table generation,
line plotting, contour plotting, and perspective plotting as shown below in Figure 2.
To use the CAE tool, the user makes menu selections to display screens of information.
These contain information such as the ambient plasma density. Table generation facilities
provide a means to vary one variable and examine its effect on other variables. For
example the ambient plasma density as a function of altitude or mission time could be
generated using this utility. Tables can be viewed directly, saved as an ASCII file,
displayed as a plot, or saved as a Postcript plot file. A similar utility generates contour
plots for slices of data. If the user modifies a value on a screen the change is recorded and
the screen is updated to reflect this change and any other changes in displayed quantities
354
which are dependent on the modified variable. This is the typical mode of interaction
between the user and EPSAT; change a paran_ter (or vary it over a range for a plot or
table) and examine the effect on dependent quantities. This ability of being able to vary
any quantity and watch its effect on any other quantity is the power of the data dictionary
approach used in EPSAT.
P Ial_o ) HELP<
Do Toble IRI86 I
Figure 2. The EPSAT user interface presents information to the user
through screens, line plots, perspective plots, contour plots and tables.
The data dictionary interpreter coordinates the analysis. It provides data requested by the
user interface and insures that it is up to date with respect to all of the data on which it
depends. This is accomplished by examining an ASCII file, the data dictionary, for
recipes listing dependencies of data items and how to compute new values if required. If
data needs to be computed then the appropriate analysis modules are called and their results
stored in the data base. In this way complex multi-step calculations are reduced to a series
of independent recipes each building on results determined by other recipes. Similarly,
incorporation of new analysis modules is reduced to adding a recipe in the DDI containing
the information on how the module is to be used. This increases both the speed of module
incorporation and reliability.
is
OF POOR
355
Environment And Power System Interaction Models
Plasma
High Energy Radiation
Meteoroid/Debris
Neutrals
Electromagnetic
Solar Radiation
Self-Generated
Polar & Auroral Charging
Ram/Wake Effects
Turbulence
Radiation Damage
Single Event Upsets
Punctures & Surface damage
Sensor Erosion
Atmospheric Drag
Oxygen Erosion
Vehicle Glow
Forces,Torques,Stresses
Solar Degradation
Thermal Effects
Nuclear Radiation
Outgassing Contamination
Effluents
High Voltage Interactions
High Current Interactions
Table 1. Environment categories and power system interactions.
Table 1 shows the categories of environments and their corresponding effects on power
systems. The size of this list reflects the many interactions a power system will experience.
For each environment and interaction an appropriate simulation model must be identified,
coded (unless one already exists) and incorporated into EPSAT. Calculational speed is an
important factor in these modeling codes. EPSAT is intended for use in performing
complex system tradeoff studies. Hence, large numbers of calculations consisting of
parameter studies must be possible in a reasonable amount of time using a workstation.
This restricts the models to engineering level approximations in which modeling fidelity is
exchanged for the capability to model entire complex systems.
Table 2 shows the models currently in EPSAT along with additional models to be
incorporated during the final year of the project.
?
356
Present Capabilities
Simplified Object Generation
Environment Models
Neutral
Plasma
Earth's Magnetic Field
Meteor
Debris
Orbit Generator
Interaction Models
Meteor/Debris Damage
Space Charge Sheaths
Sheath Ionization
Floating Potentials
Oxygen Erosion
Outgasslng
Nozzle Plume Expansion
Plume Shadowing
Column Densities
Scattering
Under Development
System Generation Module
Breakdown
Surface Flashover
Paschen
Plasma Induced
Neutral Interactions
Ionization
Radiation Environment
Surface Effects
Magnetic Field Interactions
Table 2 Power system-environment simulation models in EPSAT.
Summary
The high power systems envisioned for SDI applications will interaction with their ambient
and self generated environments more severely than the low power low voltage systems
used to date. SDI power systems must be designed to survive many years in these
environments and then operate in the environments on demand. The SDIO Space Power-
Space Environment Effects Program is addressing this through the Environment Power
_,stem Analysis Tool, EPSAT, program. EPSAT will provide the design engineer with
the capability to perform complex system tradeoff studies quickly and reliably. The unique
design of EPSAT guarantees it will meet the evolving needs of space power system design
engineers.
357


The environment power system analysis tool development program

The environment power system analysis tool development program

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server