ASTOS® Model Library
ASTOS - An elaborate object oriented vehicle library completely written in Ada 95
The ASTOS Model Library consists of many classes of which the following are important to understand the possibilities of this libraries. Note, that each class can be used as often as you wish and can be combined which each other class in any manner as long as physical rules are not violated.
Vehicle Components
Complete set of possible vehicle component classes from a simple vehicle mass up to dual tank stages with optimzeable filling ratio. Additional models with vehicle tank sizing, stage sizing, etc. can be used to do some "neighboring vehicle design" around a nominal configuration.
Aerodynamic Configurations
Different descriptions of the aerodynamics. like
- axisymmetric and nonsymmetric aerodynamics for conventional launchers depending on the angle of attack
- Mach-Alpha aerodynamics for winged vehicles up to 6-DOF which depend on the Mach number, the angle of attack and an optional altitude
- optional reduced drag coefficients
- each aerodynamic can be defined in the body-fixed or aerodynamic frame
Propulsion Systems
A great variety of propulsive systems with the possibility of optimizeable controls and parameters and the consideration of unburned propellant:
- fixed profile rocket propulsion where the trust can be modelled by table input of either the vacuum thrust or the mass flow as a function of the time
- variable specific impulse rocket propulsion, where ISP depends either on time or on altitude or on ambient pressure; additional the mass flow depends on time.
- throttleable and restartable rockets defined by a constant ISP and maximum mass flow
- basic design rocket derived from the throttleable rocket
- variable mixture rocket with two mass flows
- various air breathing engine types which can depend on altitude, dynamic pressure, angle of attack and ambient pressure.
- completely user defined propulsions are possible
Dynamics
Six different sets of equations of motion, one of them for fully six-degree-of-freedom motion (6DOF). Each phase can handle another dynamic system.
- inertial velocity with earth-fixed position vector
- flight-path velocity with earth-fixed position vector
- 6-DOF flight-path velocity with rotational equations of motion
- perturbed and non perturbed Keplerian orbit elements
- equinoctial orbit elements
Attitude Controls
Three different options to control the vehicle. Each phase can handle another attitude control.
- reduced and full Euler angle control
- reduced and full aerodynamic angle control
- load factor control
Many control laws to create initial guesses for launch and reentry trajectories in a varying manner
Cost Functions
Several objective functions for launch and reentry missions are available:
- maximum payload
- maximum final mass
- maximum final value
- minimum fuel consumption
- dual payload objectives for maximum inclination change and maximum ascending node change
- minimum integrated heatload
- maximum cross- and downrange
- Chebychev objective
- ...
Constraints
Models for altogether over 90 typical mission and vehicle constraints. Each constraint can be defined by the user multiple times. Model specific constraints are defined automatically to make the mission definition easier.
Planet Models
All parameters which are necessary to define the planet properties can be defined by the user including the relationship between the inertial and planeto-fixed frame. This way planet earth is not the only possible environment.
Atmospheric Models
Atmospheres for a variety of launch sites derived from the GRAM atmospheric model and a set of US Standard atmospheres. Input tables describe density, pressure and speed of sound as a function of the altitude. For more flexibility a dll-interface may be used to define own atmospheres.
Wind Models
No-wind as well as windfields as a function of the altitude can be considered in cylindrical or cartesian coordinates.
Various Utilities
A wide range of utilities simplifies a lot of work, e.g.
- automatic unit conversion between over 100 different units
- transformation routines between various flight mechanics coordinate systems
- import of table data from external files or defined in Viola syntax
- several interpolation methods: linear, spline and Akima spline; together with SOCS multidimensional least square fit interpolation.