Ares-I-X is the designation given to the flight test version of the Ares-I rocket (also known as the Crew Launch Vehicle -CLV) being developed by NASA. As part of the preliminary flight plan approval process for the test vehicle, a range safety malfunction turn analysis was performed to support the launch area risk assessment and vehicle destruct criteria development processes. Several vehicle failure scenarios were identified which could cause the vehicle trajectory to deviate from its normal flight path, and the effects of these failures were evaluated with an Ares-I-X 6 degrees-of-freedom (6-DOF) digital simulation, using the Program to Optimize Simulated Trajectories Version 2 (POST2) simulation framework. The Ares-I-X simulation analysis provides output files containing vehicle state information, which are used by other risk assessment and vehicle debris trajectory simulation tools to determine the risk to personnel and facilities in the vicinity of the launch area at Kennedy Space Center (KSC), and to develop the vehicle destruct criteria used by the flight test range safety officer. The simulation analysis approach used for this study is described, including descriptions of the failure modes which were considered and the underlying assumptions and ground rules of the study, and preliminary results are presented, determined by analysis of the trajectory deviation of the failure cases, compared with the expected vehicle trajectory.
Nomenclature
ATK= Alliant TechSystems (a division of ATK Thiokol, Inc.). 6-DOF = six degrees-of-freedom POST2 = Program to Optimize Simulated Trajectories, Version 2 q-α = Product of vehicle dynamic pressure, pounds per square foot (q) and its angle of attack, deg (α) q-β = Product of vehicle dynamic pressure, pounds per square foot (q) and its sideslip angle, deg (β) RoCS = Roll control system RSRM = Reusable solid rocket motor TVC = Thrust vector control
The evaluation of the risk to the public from Space Shuttle launches requires simulation and analysis of ascent trajectories for various failure scenarios. The failure modes of particular interest are ones that result in an uncontrolled trajectory deviation, referred to as a malfunction turn. Once these malfunction turn failures are identified, the failure mode effects are modeled and incorporated into a Shuttle ascent simulation. The simulation results are then analyzed to determine the impact of the failure on the ascent trajectory and vehicle integrity. The results serve as initial conditions for free-flying Solid Rocket Booster (SRB) and vehicle debris trajectory simulations, which are utilized in conjunction with probabilistic methods to obtain casualty expectation estimates. The methods for simulating malfunction turn trajectories are discussed along with the corresponding ascent trajectory results.
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