ENGINE SYSTEM LOADS DEVELOPMENT FOR THE FASTRAC 60K FLIGHT ENGINE

Greg Frady* and Eric R. Christensen t, Ph.D.Sverdrup Technology MSFC GroupHuntsville, AlabamaKatherine Mims *, Don Harris §, Russell Parks I, Joseph Brunty #, Ph.D.NASA George C. Marshall Space Flight CenterHuntsville, AlabamaAbstractEarly implementation of structural dynamics finiteelement analyses for calculation of design loads isconsidered common design practice for high volumemanufacturing industries such as automotive andaeronautical industries. However, with the rarity ofrocket engine development programs starts, thesetools are relatively new to the design of rocketengines. In the new Fastrac engine program, the focushas been to reduce the cost to weight ratio; currentstructural dynamics analysis practices were tailored inorder to meet both production and structural designgoals. Perturbation of rocket engine designparameters resulted in a number of Fastrac loadcycles necessary to characterize the impact due tomass and stiffness changes. Evolution of loads andload extraction methodologies, parametricconsiderations and a discussion of load pathsensitivities are discussed.1.0 IntroductionThe Fastrac engine is a 60,000 pound thrust liquidoxygen/kerosene (LOX/RP-I) engine being designedand developed at the NASA Marshall SpaceflightCenter (MSFC). The Fastrac (Figure 1) is a single-stage, gas-generator cycle engine that utilizes oneturbopump, a single-use combustion chamber andobjective of the X-34 is flight demonstration of keyreusable launch vehicle operations and technologiesdirected at the RLV goal of low-cost space access.Key technologies include composite primary and........ airframe structures, composite reusablepropellant tanks, cryogenic insulation and propulsionsystem elements, advanced thermal protectionsystems and materials, low-cost avionics, integratedvehicle health monitoring systems, and flush air datasystems. The X-34 vehicle will be a winged vehiclewith a wing span of 27.7 feet and a length of 58.3feet. In a typical X-34 flight, the testbed vehicle willbe dropped from an L-1011 aircraft, the engine willstart and accelerate the vehicle to Mach 8. Thevehicle will climb up to 250,000 feet, followed by acoast phase, re-entry and horizontal landing on aconventional runway.This paper describes the work done at MSFC tosimulate the structural dynamic response of theFastrac engine system. The primary purpose of thisanalysis is to calculate the predicted dynamic loadson engine components and interfaces for use incomponent stress analysis and design. Enginecomponents and interfaces include items such asducts, brackets, gimbals, gimbal actuators, etc. Theanalysis utilizes a finite element model (FEM) of theengine system including all major components andvehicle interfaces. The engine is being tested inbell-shaped nozzle. The nozzle uses an ablative liner various configurations, allwithin a graphite composite overwrap. The firstplanned use of the Fastrac is in the X-34 vehicle.The X-34 technology testbed demonstration vehicle(Figure 2) is a NASA program intended todemonstrate key technologies applicable to theReusable Launch Vehicle (RLV) Program 1. Theof which have beenmodeled by the Fastrac FEM. The configurationsanalyzed include the X-34 flight configuration, thePropulsion Test Article (PTA) ground testconfigurations, and the Horizontal Test Facility(HTF) ground test configurations. Each configurationmay include several different sized nozzles and eachhas different support boundary conditions and*Senior Engineer I, Engineering DirectoratetEngineering Specialist, Associate Fellow AIAA_Dynamics Engineer, Structural Dynamics/Loads Group ED21, AIAA Member_Dynamics Engineer, Structural Dynamics/Loads Group ED21IDynamics Test Engineer ED73'Dynamics Engineer, Structural Dynamics/Loads Group ED21"Copyright © 2000 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved."