Chimera- a Low Cost Solution to Small Satellite Space Access
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Chimera- A Low Cost Solution to Small Satellite Space Access John Crowley, Virgil Hutchinson, Alex Keisner, Dave Young Mike Curry, Jonathan Jackson, John Maatsch, Pavel Piletsky Faculty Advisor: Dr. John Olds Georgia Institute of Technology Atlanta, GA 30332 Abstract Introduction The Chimera rocket was designed to enter the The small satellite market has been growing in small satellite market by offering an affordable and recent years. Interest ranges from the DoD to flexible alternative to the Pegasus launch vehicle. A universities wishing to launch scientific payloads. number of design concepts were evaluated, and one Current launch vehicles can provide services for was selected to undergo detailed analysis. This these organizations, but at a high cost. The Pegasus included disciplinary analyses in aerodynamics, launch vehicle, made by Orbital Sciences, can cost propulsion, trajectory, aeroheating, structures, $12M or higher1. weights, operations, and cost. The baseline vehicle, In many cases, universities cannot afford to pay consisting of a Minuteman 2-2 first stage, a PAM-S for a launch if it costs more than twice the cost of the second stage, and a new third stage carries a 100 and satellite that they built. Therefore they have sent out 50 kg payload to a 700 km altitude, at inclinations of an RFP to build a new low cost launcher that is 60° and 110° respectively. At this point a Monte particularly suited for their tastes. Launch altitudes Carlo Simulation was performed to determine how and inclinations are based on a survey of all the well the system met its price goals. The baseline previous launches made by universities. vehicle fails to meet the desired launch price of $5 The RFP details a business case. The item of million to a reasonable confidence level. However, interest is the price per launch paid for by the either the implementation of a cost reduction in the universities. The RFP calls for the launch costs to be cost of the first stage, or the infusion of appropriate $5M. Additionally, the notional start up company structural and propellant technologies in the design of must be able to show an internal rate of return of the third stage, help to make the desired launch price 10%. The company is also granted a loan from the viable. DoD of $500M to cover non-recurring costs. The company may use any US launch facility for a Nomenclature nominal fee of $50,000 per launch. Two design reference missions were detailed APAS Aerodynamic Preliminary Analysis within the RFP. The first was to send a 100 kg System payload to a 700 km, 60° orbit. The second mission DoD Department of Defense was to send a 50 kg payload to a 700 km, 110° orbit. DDT&E Design, Development, The constraints for the payloads were a 6 g axial load Testing & Evaluation and 2 g lateral load, and the payload could not be HABP Hypersonic Arbitrary Body exposed to a dynamic pressure of greater than 30 Pa. Program As a final note, the RFP said that US or foreign NPV Net Present Value parts could be utilized in the construction of the POST Program to Optimize launch vehicle. It was decided early in the project to Simulated Trajectories purchase most parts in order to reduce costs. RCS Reaction Control System RFP Request for Proposal Design Methodology ROSETTA Reduced Order Simulation for Evaluating Technologies The design team chose a methodology to explore and Transportation as many concepts as possible while maintaining Architectures creativity and technical feasibility. A brainstorming TFU Theoretical First Unit technique, known as a morphological matrix, was UDP Unified Distributed Panel used to look at all the possible characteristics of the vehicle. The first matrix was created to look at the 1 subsystem components and all the possible parts that Monte Carlo simulation. This is detailed in the final could fulfill them. The second matrix then combined, section of the report. through a structured selection process, these sub Config systems into eleven different concepts. Table 1 shows Virgil Aerodynamics the different types of concepts that were created John Propulsion through the morphological matrix. Dav Trajectory Mike Weights Table 1- System Concepts. & Sizing Pavel Aero- Type Number heating Balloon Assist 2 Alex Operations Alex Air Assist 3 Reliability John Cannon Assist 1 Economics MagLev Assist 1 Figure 1. Design Structure Matrix. Ground Launch 4 Disciplinary Analyses The design team then evaluated each of these qualitatively using TOPSIS. TOPSIS is an evaluation Aerodynamics method used to show how close a design is to the The stability and modicum of lift required during ideal solution. The higher the closeness value of a the atmospheric flight of the vehicle was provided by design, the better it is. The team evaluated these 11 four fins attached to the first stage of the vehicle. concepts using 19 criteria, each with a weight. These Due to the rocket’s release from the air-assist vehicle criteria and weights were developed through the use at a high flight path angle, it was assumed that the of a QFD. use of a wing to provide lift for pull-up was not The QFD maps the customer requirements and required. Each of the four fins is 1.38 meters in engineering characteristics through a relationship length, has an area of 0.679 m2, and is arranged at 35 matrix. In this matrix each of the requirements and degrees from the center neutral axis. This characteristics are rated as to how each affects the asymmetric arrangement of the fins allowed for a other based on a 1-3-9 scale. If they have a strong small increment of lift to be provided to the rocket affect on each other (i.e. cost and weight), they are along with providing stability through the first stage given a 9. The QFD then multiplies these numbers of flight. with the customer requirement importance values and The Aerodynamic Preliminary Analysis System determines a relative importance value. This (APAS), a combination of three individual programs, importance value was used as the weighting, and the was utilized in performing the aerodynamic analysis engineering characteristics were used as the criterion. of the vehicle. APAS was used to define the vehicle The TOPSIS analysis determined the ranking of geometry at each stage of flight and initialize the each of these concepts. The top two designs were a 4- analysis runs, which were based on altitude, velocity, stage ground launch vehicle and a 3-stage air assist and angle of attack. After defining the geometry and launch. analyses, the Unified Distributed Panel (UDP) These vehicles were then designed and sized program performed the subsonic and supersonic using the appropriate disciplines as seen in Figure 1. aerodynamic analysis and the Hypersonic Arbitrary The data obtained from this analysis was then fed Body Program (HABP) was used to conduct the back into TOPSIS so the final two designs could be hypersonic analysis. UDP’s analysis is based on evaluated quantitatively. The initial cost estimate of slender body theory and source and vortex panel the air assist launch was found to be approximately methods while HABP’s analysis is based on impact $9.5M and the ground launch cost estimate was theory. Aerodynamic analysis was only performed approximately $10.9M. TOPSIS ranked the air assist on the vehicle configuration from launch to payload launch as the best vehicle to use. This was confirmed fairing separation because all aerodynamic by the launch price and an evaluation by the team of coefficients were constant above an altitude of 100 the designs. The air assist launch was chosen to be km3. designed at a higher level of fidelity. The following The resulting data from the aerodynamic sections outline the results of the disciplinary analyses showed that during subsonic and sonic analyses. These analyses were performed as the flight, the fins have a lift coefficient of 0.175, which following Design Structure Matrix indicates. indicates their provision of a small increment of lift A probabilistic study was then performed on the to aid in the pull-up of the rocket. The variation of design with the help of a ROSETTA model and a zero-lift drag coefficient with Mach number for the 2 aerodynamic performance of the vehicle provided by above, both the first two stages as well as the air APAS is shown in Figure 2. launch aircraft will be existing flight hardware to 1.8 limit costs. 1.6 Table 2 – Specification of Third Stage Motor. 1.4 Stage 1 Thrust 2669 N 1.2 Isp 295 sec 1 Stage 2 d,0 C 0.8 Burn Time 33.4 sec 0.6 Exit Area 0.152 m2 0.4 Expansion Ratio 50 0.2 Propellant Mass 30.8 kg 0 Motor Mass 6.63 kg 0 1 2 3 4 5 6 7 8 9 10 Mach Number Motor Volume 0.0195 m3 Figure 2. Variation of zero-lift drag coefficient with Mach number. A list of nine possible aircraft was compiled with the flight envelope of each aircraft. From this list Propulsion three separate aircraft were chosen that seemed to Even so, buying pre-existing stages and cover the entire flight regime that is to be developing as little as possible is the surest way to investigated. These aircraft are compiled in Table 3. reduce costs and uncertainty, and thus increase the From these three and an initial investigation of chances of reaching the price goals set forth in the trajectories in POST it was determined that the B-52 RFP. Therefore, the first two stages were set as resulted in an appropriately sized rocket (to fit existing solid rocket motor stages, and only the third beneath the aircraft).