A Distributed Mission Programming and Evaluation Environment for Rapid
Access to Space Vehicles
Donghui WANG 1, Fei XIAO1, Min CHEN1, Weihua ZHANG1
1
College of Aerospace and Materials Engineering, National University of Defense Technology, 410073, Changsha, Hunan Province, P. R. China, 0731-84576482, [email protected]
ABSTRACT
Rapid Access to Space Vehicle(RASV), with the purpose of breakthrough and validation of the capabilities of rapid access to space and application of space, resolution for emergency space issues, proves to be technology-intensity and system-complexity, and it turns out to be complacated system engineering to organize a RASV space mission.
For the design and mission programming and evaluation of RASV, a computer-assisted distributed environment is established in this paper, the new environment has been developed to allow decision makers to perform an overall design and assessment of RASV. The Mission Programming and Evaluation Environment for RASV is both distributed and collaborative, and it facilitates integration of the vehicle performance simulation disciplines including weights and sizing, aerodynamics, trajectories, propulsion and CAD-based geometries, which servers as supports for the RASV mission programming and evaluation. The environment constructed in this papaer has been tailored to serve as an easy-accessed agency-wide source for all of our RASV systems engineering functions. Thus, it is configured to facilitate data management, automated tool/process integration and execution, and data presentation.
1. Introduction
In the world of conventional aircraft, to organize and run a space mission proves to be an extremely complex system engineering with the characteristics of technology-intensity and system-complexity, the commanders must pre-plan and do quite a few coordination arrangements detailedly and repeatedly, which is quite time-consuming, and the space mission is often completed with high risks. These difficulties are significantly magnified when it turns out to be RASV[1], which serves as a resolution for rapid access to space, utilization of space, and space emergency issues. With the basic characteristics of celerity, the mode of RASV mission analysis requires much improved.
The current Mission Programming and Evaluation Environment(MPEE) described herein is the product of an agency-wide effort to improve the engineering analysis capabilities for RASV, and the effort has focused on the integration of improved multi-discipline tools into a distributed environment，which is tailored to assist commanders to progarm the RASV mission、perform vehicle design, simulate the RASV mission and run mission evaluation automatically or semi-automatically in sequence.
The environment architecture of MPEE is one of the key problems, the scope of this document is also to contribute to the analysis of RASV mission process, and some key technologies in building up the generic MPEE framwork.
2. Motivations for Developing MPEE
2.1 Description of the Problem
RASV system is made up of spacecraft, launch vehicle, launch site, TT&C network and application system, etc. and running a RASV mission proves to be a complicated system engineering. The RASV mission life-cycle includes mission programming, vehicle design, mission simulation and assessment，as is shown in Figure 1. The RASV mission is so comlicated that it is difficult to contrive a RASV scheme that satisfies all the needs of commanders directly, the mission process usually contains several loops to refine the scheme, as is illustrated in Figure 2.
Mission Programming Vehicle Design Mission Simulation Mission Assessment Downstream Impact Downstream Impact Downstream Impact Upstream Feedback Upstream Feedback Upstream Feedback Upstream Feedback
Figure 1 The RASV mission life-cycle Figure 2 The RASV mission process
2.1.1 RASV Mission Programming
According to the technical characteristics of the special space mission, commanders map out the mission
scheme. RASV mission programming[2][3] includes orbit designning, launch window planning, TT&C
network programming, Mission schedule design, Trajectory programming and so on. 2.1.2 Vehicle Design Overall Design Scheme Design Data Warhead Design Propulsion Design GNC Design Aerodynamics /Thermal Protection Structure Design Design Data Design Data CAX Simulation 3DOF/6DOF Trajectory Simulation Simulation Data Simulation Data Design Cycle
Figure 3 The RASV Design Cycle
According to the results of mission programming, RASV is designed. The design process contains warhead design, propulsion selection, GNC(guidence, navigation and control) design, airframe layout, aerodynamics/thermal protection design and vehicle configuration，etc. A design-cycle comes into being when vehicle design process associates with the process of mission simulation, just as is illustrated in Figure
3. To satisfy the request of celerity, the sub-systems of RASV are all modularized and sequential, what the designers need to do is to pick up the appropriate sub-systems according to the design results to sewn them together to assemble the RASV for launching.
2.1.3 Mission Simulation
According to the results of mission programming and vehicle design, the running process is simulated. 3DOF or 6DOF trajectory simulation are carried out and Monte Carlo analysis has also been incorporated. Outputs from trajectory simulation, as inputs for 1D bending loads anaysis or 3D FEA(Finite Element Analysis) is used to generate loads analysis cases for structural sizing and will be used for sizing the thermal protection system and airframe using 3D CFD based methods.
2.1.4 Mission Assessment
The performance and efficiency of RASV is evaluated based on the simulation run-time data, and at the same time, a comparison between schemes is carried out based on the assessment results.Comprehensive assessment index system includes but not is limited to the categories including Observing capacity, Data transfer capability and Orbit control accuracy .
Assessment algorithms library containing AHP, BP neural network and FCE (Fuzzy Comprehensive Evaluation), etc. has been established to evaluate the reliability and safety of a RASV scheme.
2.2 The Motivations
As highlighted by the characteristics of RASV mission process, there has been recognition among us that there is a strong need for the development of an advanced integrated analysis environment. The primary
motivations[4] behind the MPEE is summarized below:
A) Many currently used analysis and design tools have never been integrated turly, thus, an integration standardization process must be contrived to arrive at the common framework for handling the input formatting, execution and output parsing of existing self-developing or commercial ones tools and the manual data exchange between tools will be eliminated.
B) No single person has the critical mass to individually analyze and design RASV. Thus, the researchers from multiple departments need the ability to participate collaboratively in the RASV studies.An easy and seamless access to distributed databases, distributed analysis capability and distributed analysis and design processes is the key to facilitating the agency-wide participation.
C) There exists iterations in RASV mission process. Usually, a one-time plan could not achieve the mission objective, as a result, a coordinated and process-controlled approach to run the analysis is strongly needed, specifically, there is necessity to: 1) archive all analyses and processes to faciliate data traceability and accessibility both between tools and for reporting; 2) have an convenient, flexible data presentation, visualization and report generation capability.
D) To provide the commanders the support for decision making capability is the main motivation for MPEE. Characteristics of good decision making process include: 1) to facilitate the accuracy of life-cycle analysis tools (i.e. operations,reliability, maintainability, etc) through their integration into complete
system-level analysis processes to yield believable consequences; 2) valuing heritage data, risks and synergies in addition to quantified metrics to compare candidate choices; 3) providing multiple ways of representing comparisions between choices.
3. Mission Programming and Evaluation Environment for RASV
The MPEE is a distributed environment that enables RASV mission analysis process to be defined and executed in use of existing various disciplinary tools. It is an archival and retrieval system for analysis models, documentation, results and processes. Current MPEE offers the infrastructure for applications
integration, process contro[5], data management, user interface, visualization, and collaboration.
3.1 MPEE System Architecture
The MPEE system design is illustrated in Figure 4, and the principal functions of MPEE subsystems are: Analysis Tool Layer: to provide an access to the distributed set of programming, simulation, assessment and requirements/technology tracking goals. The capabilities in this layer are enabled by encapsulating analysis tools into resuable modules and a customized XML-format “wrapper” for encapsulating is established. A common data dictionary including multiple disciplines serves as the MPEE data model among tools.
Data Layer: to provode automated capture, storage and retrieval of data, models, modules, and customized processes. This satisfies the capability that enables duplication and verification of previous analysis results.
Figure 4 MPEE System Design
User Layer: to provide users an access to the system, enabling the input and display of large quantities of data at high human-computer communication bandwidths.
Infrastructure Layer: to provide network and communication among distributed subsystems.
3.2 Key Tecnologies of MPEE
3.2.1 Flexible Process and Tool Execution Management
A process is an assembly of multiple modules whose order of execution and responsible analysist are flexibly controlled by the environment. A module is one of the
wrapped tools. A tool is an analytical entity that is to perform a discipline specific task. Generally each RASV mission is designed for a unique target, which leads to the varity of tasks composing the space mission. A flexible architecture is established based on workflow technology, in which way a customer may define any number of different processes using different modules, and processes can be redifined and customized, as soon as the space mission changes, as is illustrated in Figure 5.
Therefore, the aim of process management component is to
provide process modeling, scheduling and monitoring tools, in which way users can define and control their own RASV mission process.
3.2.2 Automated Data Management
MPEE provides the ability to perform data capture, control and presentation. It enables a secure access to the distributed data and offers a platform for researchers form different departments or offices to retrieve tasks and data, perform analysis, and publish results.
An important element of MPEE data management component is the data dictionary among multiple disciplines including Aerodynamics, Geometry, Propulsion, Structures, Trajectory, and Sizing, etc. The advantages of utilizing the data dictionary are as follows:
Anslysis A Anslysis E Anslysis D Anslysis C Anslysis B Anslysis F Data Dictionary Anslysis A Anslysis B Anslysis C Anslysis E Anslysis F Anslysis D
Figure 6 Traditional N2 Integration Strategy Figure 7 Current 2N Integration Strategy
A) The data dictionary supplies a common interface to every tool integtated into the environment, the common interface implies that each two-way interface with a new tool is independent of all other toos interfaced with data dictionary. Compare Figure 6 and Figure 7, where the traditional approach of developing
an independent interface between each new tool pair is compared with use of the data dictionary. The former
has to develop O(N2) interfaces[4],while the latter only O(2N) interfaces, where N is the number of tools.
B) The application of the dictionary makes it possible that the data flow along with the control flow of RASV mission processes is on the automatic move. The modules assembling the mission processes will match their inputs from the data dictionary database and place their outputs into it for other modules automatically through the Automatic Matching Algorithms(AMA).
4. Conclusions
A considerable amount of effort has been spended in the development of Mission Programming and Evaluation Environment for RASV. MPEE is currently a collaborative and distributed system which provides a platform for RASV mission programming, vehicle design, mission simulation and assessment, which can help engineers reducing the design costs and risks greatly. This environment enables the integration of both performance analysis and life cycle-related tools or disciplines. Additionally, this environment is extensible to higher fidelity tools to support a maturing technology base.
MPEE has been run successfully for RASV, completing 21 cases within a week period. MPEE is able to provide a list of candidate schemes and campare these choices to give the commanders the support for decision making.
Finally, this effort is just a beginning. A lot of work can be done in order to improve the performance and productivity of the system, and further studies on data management, integration methodology, process controll as well as assessment methodology and virtual demonstration technology will be summarized in our next study.
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