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Daniel Guggenheim School of Aerospace Engineering
Daniel Guggenheim School of Aerospace Engineering
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ItemDevelopment of SAMURAI - Simulation and Animation Model Used for Rockets with Adjustable Isp.(Georgia Institute of Technology, 2005-01) Sakai, Tadashi ; Olds, John R. ; Alemany, KristinaAn interplanetary trajectory calculation application SAMURAI - Simulation and Animation Model Used for Rockets with Adjustable Isp - has been developed. SAMURAI is written in C++ and calculates transfer trajectories with variable thrust, variable Isp (VASIMR type) engines as well as conventional constant low thrust, constant Isp engines and high thrust engines. SAMURAI utilizes a calculus of variations algorithm to evaluate the thrust history that minimizes the fuel consumption from one planet to another. A trajectory with a planetary swing-by can also be calculated. After calculation, a 3D animation of the resulting transfer trajectory is created and can be viewed with a web browser using VRML. In this paper, equations and methods used in SAMURAI, and the capabilities of this application are presented. A few examples including a round trip from Earth to Mars have been analyzed, and trajectories with variable Isp engines, constant Isp, engines, and high thrust engines are compared.
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ItemCenturion: A Heavy-Lift Launch Vehicle Family for Cis-Lunar Exploration(Georgia Institute of Technology, 2004-07) Young, David Anthony ; Olds, John R. ; Hutchinson, Virgil L., Jr. ; Krevor, Zachary C. ; Pimentel, Janssen ; Reeves, John Daniel ; Sakai, Tadashi ; Young, James J.Centurion is an expendable heavy lift launch vehicle (HLLV) family for launching lunar exploration missions. Each vehicle in the family is built around a common two-stage core. The first stage of the core uses kerosene (RP-1) fuel and utilizes four staged-combustion RD-180 rocket engines. The upper stages consist of liquid oxygen (LOX)/liquid hydrogen (LH2) propellant with three 220,000 lb thrust-class expander rocket engines. The larger variants in the Centurion family will also use either one or two pairs of five-segment solid rocket motors which are now being developed by ATK Thiokol. The Centurion family consists of three vehicles denoted as C-1, C-2, and C-3. The first vehicle (C-1) is a four RD-180 core with a LOX/LH2 upper stage. The C-1 is designed to deliver a 35 metric ton (MT) CEV to a 300 km x 1000 km highly elliptical orbit (HEO). This HEO allows the CEV to more easily transfer to a lunar trajectory, while still having the ability to abort after one revolution. The C-1 also is designed to meet mission requirements with a failure of both one RD-180 and one upper stage engine. The C-2 and C-3 Centurions are both cargo carrying variants which carry 100 MT and 142 MT of cargo to a 407 km low earth orbit (LEO) respectively. The C-2 utilizes two five-segment solid rocket boosters (SRB), while the C-3 uses four SRBs. Details of the conceptual design process used for Centurion are included in this paper. The disciplines used in the design include configuration, aerodynamics, propulsion design and selection, trajectory, mass properties, structural design, aeroheating and thermal protection systems (TPS), cost, operations, and reliability and safety. Each of these disciplines was computed using a conceptual design tool similar to that used in industry. These disciplines were then combined into an integrated design team process and used to minimize the gross weight of the C-1 variant. The C-2 and C-3 variants were simulated using the C-1 optimized core with different configurations of SRBs. Each of the variants recurring and non-recurring costs were computed. The total development cost including the design, development, testing and evaluation (DDT&E) cost and a new launch pad at Kennedy Space Center (KSC), was 7.98 B FY04 dollars. The theoretical first unit (TFU) cost for the C-2 variant was 532 M FY04 dollars. A summary of design disciplines as well as the economic results are included.
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ItemDevelopment of a Multipurpose Low Thrust Interplanetary Trajectory Calculation Code(Georgia Institute of Technology, 2003-08) Sakai, Tadashi ; Olds, John R.A multipurpose low thrust interplanetary trajectory calculation code has been developed. This code integrates the equations of motion along the trajectory assuming that the spacecraft is subject to a single attracting body and a constant thrust during both heliocentric and planetocentric phases. The histories of pitch and yaw angles for the heliocentric phase are calculated using the calculus of variations so that the spacecraft arrives at the destination planet with input heliocentric time of flight. For the planetocentric trajectory calculation, six equinoctial orbital elements are used in the vicinity of a planet with thrust direction fixed to be tangent to the path. For the heliocentric trajectory calculation, the components of position and velocity vectors are used. The output of the trajectory simulation is used as an input to mass estimating relationships that size the spacecraft. A VRML trajectory viewer helps to visualize how the spacecraft reaches its target.
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ItemSolar Electric Propulsion Module Concept for the BiFrost Architecture(Georgia Institute of Technology, 2002-10) Rohrschneider, Reuben R. ; Sakai, Tadashi ; Steffes, Stephen R. ; Grillmayer, Georg ; St. Germain, Brad David ; Olds, John R.This paper describes the design of a solar electric propulsion module for the Bifrost architecture. Bifrost consists of a magnetic levitation launch tube with the exit end elevated to 20 km. A 35,000 kg hybrid logistics module (HLM) is designed to attach to an array of propulsion modules that accommodate different missions. The solar electric propulsion (SEP) module is designed to circularize a payload in Geosynchronous Earth orbit (GEO) from a highly elliptic transfer orbit. A configuration consisting of a central spacecraft body propelling itself with electric thrusters and gathering solar power from two inflatable concentrating reflectors was chosen. Concentrating reflectors were chosen over thin film arrays due to the large mass savings. Details of the conceptual design process are presented. Disciplines include trajectory, power system, propulsion, and weights & sizing. A computational framework was used to wrap the disciplinary analysis to speed the design process, and optimization was performed to minimize the initial mass of the vehicle from within the design framework. The resulting vehicle has an initial mass in orbit of 40,780 kg. A demonstration model was then designed and constructed from the conceptual design. The manufacturing process for the inflatable reflector and the spacecraft body are described in detail. The demonstration model shows that an inflatable reflector is a feasible method of generating large amounts of power in space.
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ItemTechnology Assessment for Manned Mars Exploration Using a ROSETTA Model of a Bimodal Nuclear Thermal Rocket (BNTR)(Georgia Institute of Technology, 2001-08) Way, David Wesley ; Medlin, Matt ; Sakai, Tadashi ; McIntire, James ; Olds, John R.This paper investigates a new method of measuring the affordability of aerospace technologies. First, a new bimodal NTR Mars mission architecture was defined. Starting with brainstorming on the different ways to get to Mars, several different trade studies were investigated, the results of which defined the architecture. A Reduced-Order Simulation for Evaluating Technologies and Transportation Architectures (ROSETTA) models has been created from this architecture. This model is an Excel workbook of interconnected worksheets that represented the different disciplines used in creating the architecture. Each worksheet is based on the results of higher fidelity codes such as the Program to Optimize Simulated Trajectories (POST) and the Aerodynamic Preliminary Analysis System (APAS). These results were then reduced to simpler, parametric relations, giving rise to the 'Reduced Order' in ROSETTA. The BNTR ROSETTA model is capable of rapidly resizing the Mars transfer vehicle and landers and estimating the key cost and mass metrics as the input technology assumptions change. Future technology assessment will be done probabilistically, by assigning a distribution to each input parameter that the technology affects, then running a Monte Carlo analysis in order to generate an output distribution for each metric. Benefit-to-cost ratios and top-level uncertainties can be determined from this data.