Flight Simulation and Design
Drawing on decades of
engineering experience with designs and simulations of spacecraft
and flight vehicles, Triton Systems employs (as well as developed)
a suite of computer programs for modeling vehicles in flight or
making engineering trades to establish the basis for their design.
While the developed programs are unique to Triton, others
such as
MATLAB
Toolboxes and
ALIBRE computer aided
design (CAD) package are used industry wide. As expected, in
the analysis and design process, many of these computer programs
interact with each other and the programs listed below is more of a
sampling than a complete list.
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Internally
Developed Trajectory Programs
1.
LAUNCH5:
Used as a basis to
evaluate liquid rocket stage alternatives for Space Shuttle and
other launchers, this program converges on ascent targets within
several iterations based on a minimum Hamiltonian optimization and
guidance algorithm. For design studies, the program includes
modules for propellant selections, tank volume estimates, engine
performance calculations based on propellant selections, mixture
ratios, combustion chamber pressures and nozzle expansion ratios. These
models are derived from the NASA Lewis Chemical Equilibrium and
Application program CEA described below, calibrated with existing
rocket engines.
As a result, for design studies, partial derivatives for a host of
design parameters can be obtained and applied to a mission, a stage
or an overall launch vehicle configuration.
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2.
AEXTRAP:
On orbit simulations of
finite burns, relative motion, upper stage ascents or re-entries are
provided by this program. A low thrust maneuver targeting
algorithm provides predictions of first and second burn cutoffs for
milli-g maneuvers for precision orbit raising.
The method is based on
forward and backward integration of the first and second burn to
determine eccentricity matches for the coast condition.
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3.
JETFJ2:
Derived from LAUNCH5, this program addresses performance of
horizontal takeoff launch vehicles with wings and air-breathing
(jet) engines. The Stellar-J family of launch vehicles has been
simulated with this program, creating an increasingly larger library
of default property files for engine selections, upper stages, gross
liftoff weights and other parameters. The upper stage
optimization and guidance subroutine employs the same min-H
algorithm as LAUNCH5. As the vehicle configuration is
developed a pre-processor tracks mass properties for inertias of
loaded and dry weights including locations; a post processor
provides estimates of control moment loads.
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4. BISTAR:
Developed to determine
stability of planetary motion around binary star systems, this
program models the restricted elliptic three-body problem by
advancing the two primaries with Keplerian motion about a barycenter
with two ellipses of given eccentricity with semi-major axes
inversely proportional to their mass ratios. The third body is
integrated inertially with its orbital parameters calculated about
one or the other primary from the resulting state vector updates.
Program defaults initiate the planetary orbit in near circular
motion about one or the other star based on input position in Astronomical Units or
a thermal flux condition. A data base of known binary stars plus
many recently discovered stars with brown dwarf or Jovian planet
companions is provided.
For additional
background see (hyperlinked)
ACROBAT file:
ASTRO97.pdf
Power Point Slide Show:
Lunar&Extrasolar_3BodyProblems111706.pdf
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5.
SUNANG:
An on-orbit six degree
of freedom simulation, this program models spacecraft environmental
and control torques based on inertial properties, drag cross
sections, gravity gradient forces and upper atmosphere (or
exosphere) drag models. Magnetic field and damper models are
included.
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6.
JACOBEM:
Derivative of BISTAR and
AEXTRAP, this program simulates third body motion in the restricted
elliptic 3-body problem with Earth, Moon and a spacecraft as the 3
bodies. Default cases examine Earth departure and Earth return
trajectories, plus stability or motions near the five Lagrangian
points. The program can be used to assess lunar mission design
requirements based on trajectory analyses. Features under
development are finite burn simulations and means to conduct
parametric investigations for varied system true anomalies.
For additional
application background see
PDF file:
Lunar&ExtraSolar_3BodyProblems111706.pdf
Power Point Slide Show:
Lunar&ExtraSolar_3BodyProblems.
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7.
DAYPLOT:
Provides orbital decay
histories based on drag-weight parameters and high altitude
atmospheric density (>80 kilometers) based on solar extreme ultra
violet flux and terrestrial magnetism parameters. The program
provides quick estimates of orbital lifetimes for low orbiting
satellites.
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8.
PROXIM:
Launch vehicles at
staging or spacecraft in orbit rely on jet thrusters to rotate or
maintain attitude control. The thruster installations require a jet
selection logic for translational, rotational and failure modes, a
phase plane logic for evaluating errors and a dynamic models for
environmental effects and rotational schemes. This program
focuses on evaluating jet thruster configurations for a given
rigid body spacecraft. Typical use evaluates angular
accelerations provided, thruster "chatter", phase plane stability,
motions in rotational maneuver corridors, cross-coupling and
propellant consumption
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External Trajectory
and Celestial Mechanics Programs
1.
GMAT:
The General Mission Analysis Tool under development by the Goddard
Spaceflight Center provides means to generate powered or coasting
trajectories. GMAT employs an open architecture to generate new
technology through an innovative an open collaboration of NASA,
universities, businesses such as Triton and private citizens.
To
participate in its development or obtain more information, contact
http:/gmat.gsfc.nasa.gov.
2.
ALCYONE* Ephemeris:
an accurate and fast astronomical ephemeris calculator. Covering the
period from 3000 BC to AD 3000, it calculates heliocentric,
geocentric and topocentric positions of the Sun (Earth), Moon,
planets, minor planets and comets in ecliptic, equatorial and
horizontal coordinates with optional corrections for parallax and
refraction; rectangular coordinates, velocity, apparent
diameter, magnitude phase and orbital elements...JPL and other
ephemeris tables are provided.
For additional
information, contact: www.alcyone-ephemeris.info
*Named
for η
Tauri, the brightest star in the
Pleiades
open
cluster.
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Industry Tools
1.
ALIBRE:
Design Standard is a fully featured 3D CAD
application, allowing designers to create 3D mechanical designs and
generate and detail associative 2D drawings. Along with a full set
of advanced modeling tools and parametric modeling functionality,
Standard comes with the capability to create interactive 3D PDFs and
import & export designs in industry standard formats.
For more information visit
http://www.alibre.com/products/
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2.
CEA:
the chemical equilibrium and application program is
combustion and compressible flow analysis tool in steady development
at the NASA Glen Research Center since the 1950s. As described
in NASA RP-1311, the program obtains chemical equilibrium for
assigned thermodynamics states; calculates theoretical rocket
performance for specified combustion chambers; calculates Chapman-Jouguet
detonation effects or calculates shock tube parameters for both
incident and reflected shocks.
For more information visit
http://www.cea.grc.nasa.gov/
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3.
DATCOM:
provides aerodynamic coefficients and stability derivatives
for subsonic, transonic and supersonic aircraft flight based on
overall vehicle configurations or via component (wing, body,
stabilizer, flap...) analyses. The coefficients for classical
perturbation equations of motion, both lateral and longitudinal, are
parameters of these coefficients, based on wind tunnel, flight test
or computed evaluations with DATCOM methods as one means of
obtaining the values in the early design phase.
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4.
MATHCAD:
provides both symbolic
and numerical calculation capabilities with a large library of
engineering and mathematical functions and operators. The software
employs conventional mathematical notation for clarity, importing
and exporting product files to other applications such as MATLAB and
spreadsheets. It is capable of compiling FORTRAN or C output.
For more information visit
http://www.integratedpdg.com/
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5.
MATLAB:
a high performance
language for technical computing, the package integrates
computation, visualization and programming in an easy-to use
environment for mathematics and computation, algorithm development,
data acquisition, modeling, simulation and prototyping, plus
scientific and engineering graphics. Currently, Triton Systems
is exploiting three of the MatLab "Toolboxes":
Aerospace Toolbox:
extends the MATLAB technical computing environment by providing
reference standards, environment models and aerodynamic coefficient
importing (e.g., from DATCOM) for performing advanced design
aerospace analysis on the Stellar-J variants or other study
vehicles.
Control Systems Toolbox:
Detailed modeling beyond 3 degree of freedom simulation of flight
vehicles requires subsystem design and control based on classical
and modern control system algorithms. This toolbox provides an
extensive array of linear time-invariant analysis packages for both
single and multiple input and output (SISO & MIMO) systems drawing
both from classical and modern control methods.
Optimization Toolbox:
A set of algorithms or software functions capable of performing
minimization or maximization on general non-linear multi-variable
functions. This includes non-linear equation solving and least
square (data fitting) problems. This toolbox is used to
support GMAT trajectory analysis problems involving searches for
minimum time, change in velocity or expenditure of propellant.
For further information on MATLAB,
contact www.mathworks.com.
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