RESPONSIVE SMALL SATELLITE AND LAUNCH VEHICLE CONCEPTUAL DESIGN TRADE/COST MODELING

Transcription

1 AIAA SPACE 2007 Conference & Exposition September 2007, Long Beach, California AIAA RESPONSIVE SMALL SATELLITE AND LAUNCH VEHICLE CONCEPTUAL DESIGN TRADE/COST MODELING Presented at the AIAA Space 2007 Conference Sep 2007 BY Brent Hamilton Air Force Research Laboratory John Carsten, Deganit Armon, Dana Sherrell, Michael Paisner, Mark Sutton, Steve Mysko Advatech Pacific Inc. Al Milton, John Trevillion, Darren Elliott Tecolote Research Inc. Roy Smoker, Daniel Feldman MCR Inc. This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. 1

2 TABLE OF CONTENTS TABLE OF CONTENTS Overview Architecture SMAD ACEIT IPAT ACM Trade Studies Application

3 ABSTRACT The SmallSat Conceptual Design Trade and Cost Modeling Tool will determine the costs to design, develop, demonstrate and operationalize small satellite technology by providing conceptual technical and cost design trade analyses for the responsive space mission. Technical sizing and technology trade algorithms are integrated with spacecraft and launch vehicle parametric cost modeling tools to provide an end-to-end performance/cost modeling capability for space technology demonstration programs. The integrated tool will facilitate the development and evaluation of smallsat systems concepts using various launch platforms, by rapidly estimating and evaluating technologies, their associated performance improvements, and program cost sensitivity to performance and size technical parameters. Goal: Provide an integrated responsive space system design analysis tool to facilitate the optimization of mission performance within budget and cost constraints and provide space vehicle, launch vehicle & costing environment for space mission planning for end to end simulation, including launch and cost estimation. 3

4 1. Overview Small satellite cost modeling is difficult to achieve. Several models exist or are under development. However, results are inconsistent. There is a lack of detailed historical cost data for small satellite demonstrations and experiments, and there is no effective process to capture this cost information (SmallSat program CDRLs). Also, since the programs are largely experimental, it is difficult to extrapolate from single item demonstration to operational, multi-satellite functionality. Finally, there is no integrated systems engineering approach that captures cost information. Our objective was to create a tool that will effectively determine the costs to design, develop, demonstrate and operationalize small satellite technology. The goals of the integrated design tool was to provide an integrated space vehicle, launch vehicle & costing environment for space mission planning with end-to-end simulation functionality (launch through orbit and what it costs). This was accomplished by integrating four modules: The Space Mission Analysis & Design (SMAD) tool from TSTI to provide space vehicle modeling The Automated Cost Estimating Integrated Tools (ACEIT) from Tecolote to provide space vehicle cost and risk modeling The Integrated Propulsion Analysis Tool (IPAT) from Advatech to provide launch vehicle modeling The Advanced Cost Modeling (ACM) tool from Advatech to provide launch vehicle cost and risk modeling Having such a tool would directly support the ability to design and evaluate responsive space concepts, space superiority concepts and ISR concepts. 4

5 2. Architecture The SmallSat Conceptual Design Trade and Cost Modeling Tool was developed for the Air Force Research Laboratory s Space Vehicles Directorate, Kirtland Air Force Base, N.M. under the Advanced Computational Engineering Simulator-Integrated Space Engineering Tool (ACES-ISET) program by Advatech Pacific, with support from Tecolote Research and MCR Technologies. Figure 1 shows a conceptual view of the tool and the key players involved. Figure 1: Conceptual view of the components of the design tool The tool has four separate modules that are integrated within a common framework that defines the user interface and automatically passes parameters between the modules. Figure 2 shows the four modules and their interaction. When evaluating a space vehicle concept, the user first models the design of the satellite (top left). This design drives the cost of the satellite (top right), and also the selection of launch vehicle, which can be modeled for design (bottom left) and cost (bottom right). 5

6 SV Design (SMAD) SV Weights, Power & KPP SV Cost (ACEIT) LV Payload LV Design (IPAT) LV Figure 2: Architecture of the Modeling Tool LV Cost (ACM) In order to have a complete space mission costing analysis tool, the different analysis codes had to be tightly integrated. These analysis codes included the SMAD space vehicle sizing tool, the ACEIT small space vehicle costing software with intermediate Microsoft Excel interface, the IPAT launch vehicle modeling software complete with the OTS enhancements, as well as the ACM launch vehicle costing software. In addition to these main codes to be integrated, other supporting routines had to be created in order to assist in the integration and execution of the tool. The four modules are integrated within a framework called the Adaptive Modeling Language (AML). AML defines the Graphical User Interface (GUI) of the tool, giving the four modules a common interface. This makes it easy for users unfamiliar with the intricacies of the individual tools wrapped within the modules to operate the tool. The GUI exposes the relevant variables within each module. While developing the tool, we added some enhancements to the modules beyond their original capabilities. These will be discussed in the following sections. Figure 3 shows the layout of the GUI. The screen has three common sections: the Model Tree Area on the left, the Work Area in the center, and the Graphics Display Area located on the right side. 6

7 Figure 3: AML layout example The Model Tree Area is an interface that allows the user to navigate through the numerous sections of the trade study tool, with interactivity much like that of a Microsoft Windows file browser. The Work Area is an interface that allows the user to enter and retrieve information about the currently activated node in the Model Tree Area. Fields in the Work Area are color coded for ease of use, with different colors for input, output and optional input fields. The Graphics Display Area is an interface that allows the user to view any drawable objects from the model. Currently, the only drawable objects are within the IPAT section, for launch vehicle design. Options available to drawable objects include shading, panning, zooming, and rotating. Other output options include pop-up screens for display of data that can be called from within the Work Area. The following sections will discuss each of the modules in detail. 3. SMAD For the modeling of space vehicles, the SMAD tool was chosen based on widespread industry use and customer recommendations. The SMAD tool is a Microsoft Excel workbook comprised of multiple worksheets that focus on certain aspects of space 7

8 vehicle design on a conceptual level. While the SMAD tool has the capability to perform a cost analysis on the designed space vehicle, the operations and costing portions of the SMAD spreadsheet were not integrated into the ACES/ISET tool. Instead, the sizing logic for space vehicles was tightly integrated within the AML environment. Figure 4 shows a top-level flow chart of the many input worksheets within the SMAD tool. Prelim. Sizing Higher Fidelity S/C Sizing Orbits - Dynamics Attitude Control - Torques Propulsion - Sizing Orbits - Geometry Orbits - Maneuvers Orbits Patched Conic Orbits Budgets Subject EM Spectrum Obs Payload - Optics Obs Payload - Sizing Attitude Control - Sizing Comm - Uplink Comm - Downlink Power Solar Arrays Power Secondary Batteries Power Other Primary Sources Propulsion - Thermodynamics Propulsion Storage & Feed Structure - Monocoque Structure Semi- Monocoque Thermal Control - Spherical Thermal Control Solar Array SC Bus Preliminary Sizing System Sizing Summary Figure 4: SMAD process flow 8

9 The different worksheets were integrated into the tool with the input, output and default values for each sheet appearing in the corresponding work areas within the AML interface. To perform the sizing of a space vehicle using the SMAD tool, the user first has to fill out the necessary inputs for the preliminary sizing step. This includes describing the orbit of interest, with items such as orbit type (elliptical, circular), altitude, inclination angle, etc. Once the orbit has been defined, the next step in the sizing process is to describe the space vehicle payload. With the baseline SMAD tool, the only payload available was the earth-imaging sensor. The user enters information about the target of interest, as well as an existing earth-imaging sensor, and SMAD uses this information to size a new imager. Once this step is complete, the baseline SMAD tool uses a historical average of space vehicles to make a guess at the sub-system masses and power, to provide a first guess at the new space vehicle being designed. At this point in the sizing process of SMAD, the user would then input information on each of the various sub-systems (ACS, power, propulsion, etc.) to refine the preliminary guess of the mass and power for the space vehicle. Once all of the input spreadsheets have been filled out, a detailed system sizing summary displaying all of the mass and power requirements for the sized space vehicle can be viewed. For the ACES/ISET project, the baseline version of the SMAD tool was not sufficient to handle all of the requirements that were necessary to handle a more generic class of space vehicles. The first modification that was necessary was the historical sub-system mass distribution. For the baseline tool, one averaged historical mass distribution was used. This averaged distribution was taken from the SMAD book, in which case multiple classes of satellites were all grouped together, and their sub-system mass distributions were averaged. For the ACES/ISET tool, the option of choosing a more specific class of satellite, and also the ability for the user to enter the sub-system mass distributions was added to the SMAD tool. The second modification that was necessary to the baseline version of the SMAD tool was the space vehicle payload enhancement. In order to handle a broader range of space vehicles, the ability to model space-to-space imaging sensors and payload communications systems was added to the SMAD tool. In addition to these types of primary payloads, the ability to book-keep multiple secondary payloads was added to the baseline SMAD tool as well. Secondary payload types were not sized using logic, but were described with basic inputs such as mass, peak and average power, and data rate. The third modification to the baseline SMAD tool that was necessary was the capability to overwrite the mass and power values for a subsystem, rather than allowing the SMAD tool to size it. This added the capability to define a known subsystem, as in the case of a plug and play satellite, where the mass and power requirements would be known before hand. 9

10 Other modifications to the baseline SMAD tool were minor fixes to ensure proper modeling of space vehicles within the integrated environment. One such modification was the way in which the SMAD tool handled the mission duration value. Another modification to the original SMAD tool that was necessary was in the earth imaging sizing section, adjusting for an elliptical as well as a circular orbit. 4. ACEIT ACEIT (Automated Cost Estimating Integrated Tools) is a family of applications developed by Tecolote Research that support program managers and cost/financial analysts during all phases of a program's life-cycle. ACEIT is a government funded automated architecture and framework for cost estimating cost analysis, cost research, cost data collections, financial analysis, business case analysis, cost uncertainty analysis, and other cost analysis tasks. For inclusion in our tool, we selected the ACEIT module that is used for cost estimating of space vehicles. The module was fine-tuned specifically to small satellite design, by creating Cost Estimating Relationships (CERs) that were tailored towards this class of satellites. The module uses several industry standard tools to arrive at its cost estimates. Payload costs, as a function of weight and power, were derived from NASA/Air Force Cost Model (NAFCOM), Unmanned Space Vehicle Cost Model vers. 8 (USCM8), and Small Satellite Cost Model (SSCM). Software costs were derived by running SEER. Other costs, generally classified as Other Government Costs (OGC) and all its subcategories, were calculated within the model. Figure 5 is a graphical display of the components that go into the ACEIT small satellite module. 10

11 Excel interface NAFCOM Derived payload cost = f(weight, power) USCM USCM payload cost = f(weight, power) SEER Derived software cost = f(sloc) Figure 5: Architecture of the ACEIT Module OGC Costs = Program Office costs + OGC tax As with SMAD, the ACEIT module was wrapped into AML, providing, instead of the ACEIT Excel interface, the same user interface that exposes the relevant input fields. Figure 6 is a screenshot of the top level space vehicle cost interface. Yellow fields are input, and green are output. 11

12 Figure 6: Space vehicle cost interface 12

13 The user further has ability to enter mass estimates, physical estimates, power estimates, data about the payload, information about project schedule, such as project milestones and buy scenarios, risk, data about software line of code (SLOC), and specific categories of OGC. Outputs are correlation of cost and risk, in both tabular and graphical formats (S-curve), in either base-year or then-year dollars. One additional capability of the tool is the ability to model Plug-and-Play (PnP) technologies. This is an emerging field of great interest to the Space Vehicles Directorate and there are still a lot of unknowns about this technology. Nevertheless, the tool has built into it the capability to handle PnP technology, with the understanding that the costing methodology for PnP technology has not been validated. As this field grows and more data becomes available, the CERs will improve and the cost methodology will become more reliable. 5. IPAT The design and weight of the space vehicle drive the choice of launch vehicle needed to put it in orbit. The tool selected for modeling the launch vehicle is Advatech Pacific s Integrated Propulsion Analysis Tool (IPAT). IPAT can model systems and sub-systems for a variety of vehicle concepts such as Expendable Launch Vehicles (ELVs) and fully or partially Reusable Launch Vehicles (RLVs), and has an extensive database of solid, liquid and hybrid rocket motors, subsystems and components. IPAT is an established conceptual design tool for launch vehicles that integrates the most advanced vehicle analysis toolsets for conceptual design, with the ability to optimize a vehicle for a particular mission. IPAT is also written within the AML framework. A detailed description of IPAT is beyond the scope of this paper. For the purpose of modeling a satellite mission, the user can select a launch vehicle from the IPAT database, or size and design a new launch vehicle. 6. ACM The Advanced Cost Model (ACM) for launch vehicle costing was developed by MCR Technologies for commercial launch systems composed of both liquid and solid rockets. The cost model can estimate the cost of development and procurement of a launch vehicle, taking into account the Technical Readiness Level (TRL) of the system under development. ACM requires several steps to build, apply, and validate its application to alternative designs of multiple future systems. These steps include building CERs for both solid stages and liquid stages, establishing a development and production milestone schedule, performing an initial estimate of a new system, applying technical maturity cost factors (TMCF) to bring the initial estimate up to technology readiness level eight or nine quality, and showing the treatment of risk in all facets of the program. 13

14 CERs were developed from data on existing launch vehicles. Cost growth factors were derived from Selected Acquisition Reports (SARs) for the EELV program, by observing how program plans were initially scheduled and then how those schedules changed as the program matured. These cost growth factors account for the expected cost growth caused by maturing a technology from one level to another level. They can be used to adjust costs from the initial estimate at the start of a program to a point estimate when the program reaches operational capability. Risk is applied to this point estimate to cover a band of uncertainty on cost and schedule. Risk is applied using the Formal Risk Assessment of System Cost Estimates (FRISK) tool, an analytical tool also used in NAFCOM. As a program moves from milestone to milestone across time, cost estimates are redone at each milestone phase. Utilizing the cost growth factors at each milestone, those estimates can be modeled for the development effort. As the estimates are updated at each major milestone, the estimate is adjusted to that phase of the program. This is shown in Figure 7. Estimate Updates at Major Milestones - Development ATP 0.6 PDR CDR 0.3 FCA % $3,500 $4,000 $4,500 $5,000 $5,500 $6,000 $6,500 $7,000 $7,500 $8,000 $8,500 C o st ( M illio ns$) Figure 7: S-Curve Estimates at Major Milestones ACM uses a top-level Work Breakdown Structure (WBS) for the launch vehicle, allowing the user to see the allocation of costs to the LV components, and thus to forecast the cost breakdown for a new launch system. Given this WBS, ACM can also allocate risk dollars to specific WBS elements. Like the other three modules, ACM is also wrapped into the AML interface, presenting the user with a familiar GUI. 14

15 7. Trade Studies The goal of the integrated tool is to enable the user to perform rapid trade studies, comparing vehicle concepts based on design, performances and cost. Having modeled a mission, the user is presented with a mission summary screen, as shown in Figure 8. Figure 8: Mission summary interface 15

16 8. Application The integrated design tool was used earlier this year to assist in the evaluation process of proposed concepts for a new tactical satellite. A joint team used the tool to analyze and evaluate the proposals and provide significant input towards the down selection of the satellite concepts. This tool holds promise of becoming a standard evaluation tool for space missions in the years to come. 16