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Computational Model of Heat Transfer on the ISS

SCRAM Lite (“SCRAM” signifies “Station Compact Radiator Analysis Model”) is a computer program for analyzing convective and radiative heat transfer and heat-rejection performance of coolant loops and radiators, respectively, in the active thermal-control systems of the International Space Station (ISS). SCRAM Lite is a derivative of prior versions of SCRAM but is more robust.

Posted in: Briefs, TSP

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Optimization of Angular-Momentum Biases of Reaction Wheels

RBOT [RWA Bias Optimization Tool (wherein “RWA” signifies “Reaction Wheel Assembly”)] is a computer program designed for computing angular momentum biases for reaction wheels used for providing spacecraft pointing in various directions as required for scientific observations. RBOT is currently deployed to support the Cassini mission to prevent operation of reaction wheels at unsafely high speeds while minimizing time in undesirable low-speed range, where elasto-hydrodynamic lubrication films in bearings become ineffective, leading to premature bearing failure. The problem is formulated as a constrained optimization problem in which maximum wheel speed limit is a hard constraint and a cost functional that increases as speed decreases below a low-speed threshold.

Posted in: Briefs, TSP

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Short- and Long-Term Propagation of Spacecraft Orbits

The Planetary Observer Planning Software (POPS) comprises four computer programs for use in designing orbits of spacecraft about planets. These programs are the Planetary Observer High Precision Orbit Propagator (POHOP), the Planetary Observer Long-Term Orbit Predictor (POLOP), the Planetary Observer Post Processor (POPP), and the Planetary Observer Plotting (POPLOT) program.

Posted in: Briefs

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Monte Carlo Simulation To Estimate Likelihood of Direct Lightning Strikes

A software tool has been designed to quantify the lightning exposure at launch sites of the stack at the pads under different configurations. In order to predict lightning strikes to generic structures, this model uses leaders whose origins (in the x–y plane) are obtained from a 2D random, normal distribution. The striking distance is a function of the stroke peak current, which is obtained from a random state machine that extracts the stroke peak current from a lognormal distribution. The height in which the leaders are originated is fixed and chosen to be several “strike distances” greater than the tallest object under study.

Posted in: Briefs

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Adaptive MGS Phase Retrieval

Adaptive MGS Phase Retrieval software uses the Modified Gerchberg-Saxton (MGS) algorithm, an image-based sensing method that can turn any focal plane science instrument into a wavefront sensor, avoiding the need to use external metrology equipment. Knowledge of the wavefront enables intelligent control of active optical systems.

Posted in: Briefs, TSP

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Predicting Boundary-Layer Transition on Space-Shuttle Re-Entry

The BLT Prediction Tool (“BLT” signifies “Boundary Layer Transition”) is provided as part of the Damage Assessment Team analysis package, which is utilized for analyzing local aerothermodynamics environments of damaged or repaired space-shuttle thermal protection tiles. Such analyses are helpful in deciding whether to repair launch-induced damage before re-entering the terrestrial atmosphere. Given inputs that include re-entry trajectory and attitude parameters, air density, air temperature, and details of each damage or repair site, the BLT Prediction Tool calculates expected times of laminar-to-turbulent transition onset of the boundary-layer flow during re-entry. (These times help to define the proper aerothermodynamic environment to use in subsequent thermal and stress analyses of local structural components.)

Posted in: Briefs

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Calculations for Calibration of a Mass Spectrometer

A computer program performs calculations to calibrate a quadrupole mass spectrometer in an instrumentation system for identifying trace amounts of organic chemicals in air. In the operation of the mass spectrometer, the massto- charge ratio (m/z) of ions being counted at a given instant of time is a function of the instantaneous value of a repeating ramp voltage waveform applied to electrodes. The count rate as a function of time can be converted to an m/z spectrum (equivalent to a mass spectrum for singly charged ions), provided that a calibration of m/z is available.

Posted in: Briefs

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