Effect of inert propellant injection on Mars ascent vehicle performance

A Mars ascent vehicle is limited in performance by the propellant which can be brought from Earth. In some cases the vehicle performance can be improved by injecting inert gas into the engine, if the inert gas is available as an in-situ resource and does not have to be brought from Earth. Carbon dioxide, nitrogen, and argon are constituents of the Martian atmosphere which could be separated by compressing the atmosphere, without any chemical processing step. The effect of inert gas injection on rocket engine performance was analyzed with a numerical combustion code that calculated chemical equilibrium for engines of varying combustion chamber pressure, expansion ratio, oxidizer/fuel ratio, and inert injection fraction. Results of this analysis were applied to several candidate missions to determine how the required mass of return propellant needed in low Earth orbit could be decreased using inert propellant injection

Rotor response for transient unbalance changes in a nonlinear simulation

Transient unbalance shifts were determined not to excite a rotor instability in the high pressure turbomachinery of the Space Shuttle Main Engine using the current rotor dynamic models. Sudden unbalance changes of relatively small magnitudes during fast-speed ramps showed stable nonsynchronous motion depending on the resultant unbalance distribution at subsequent high speed dwells. Transient moment unbalance may initiate a limit cycle subsynchronous response that shortly decays, but a persistent subsynchronous with large amplitudes was never achieved. These limit cycle subsynchronous amplitudes appear to be minimized with lower unbalance magnitudes, which indicates improved rotor balancing would sustain synchronous motion only. The transient unbalance phenomenon was determined to be an explanation for synchronous response shifts often observed during engine tests

An assessment of various side-stick controller/stability and control augmentation systems for night nap-of-Earth flight using piloted simulation

Several night nap-of-the-earth mission tasks were evaluated using a helmet-mounted display which provided a limited field-of-view image with superimposed flight control symbology. A wide range of stability and control augmentation designs was investigated. Variations in controller force-deflection characteristics and the number of axes controlled through an integrated side-stick controller were studied. In general, a small displacement controller is preferred over a stiffstick controller particularly for maneuvering flight. Higher levels of stability augmentation were required for IMC tasks to provide handling qualities comparable to those achieved for the same tasks conducted under simulated visual flight conditions

Survey of users of earth resources remote sensing data

A user survey was conducted to determine current earth resources survey (ERS) data use/user status and recommendations for strengthening use. Only high-altitude aircraft and satellite (primarily LANDSAT) data were included. Emphasis was placed on the private sector/industrial user. Objectives of the survey included: who is using ERS data, how they are using the data, the relative value of current data use as well as obtaining user views as to possible ways of strengthening future ERS data use. The survey results are documented and should provide relevant decision making information for developing future programs of maximum benefit to all end users of satellite ERS data

Records recovery and terrorism

A recent disaster at Oregon State University did not occur the day after Christmas, on a Sunday, or even on campus. It was not the result ofa water pipe accidentally breaking, an earthquake, or a fire. Instead, it was caused by an act ofterrorism. Early in the morning of Monday, June 10, members ofthe Animal liberation Front (ALF), a radical animal- rights group, vandalized the University's mink research farm. A storage barn was completely destroyed by fire, graffiti was spray-painted on the farm's office and laboratory walls, research records in the office were dumped on the floor, and color slides were stolen. An unidentified chemical agent was poured on a small amount of record material, and a nearby bathroom fixture was broken, flooding the office and the strewn records. What faced the disaster recovery team at the mink research facility was not the usual disaster situation, as we have come to think of it in the archival and library community

Detection of Prolonged Diapause of Northern Corn Rootworm in Michigan (Coleoptera: Chrysomelidae)

Prolonged diapause of northern corn rootworm, while known from other Midwestern states, has not previously been reported in Michigan. Populations of northern corn rootworm, (Diabrotica barberi) from two first-year corn fields in Genesee County, Michigan were examined for prolonged egg diapause. Pro- longed diapause was suspected in these populations due to an unusually high proportion of northern versus western corn rootworms in these fields. Eggs obtained from females collected at these sites were reared in the laboratory for two years. The presence of the prolonged diapause trait was confirmed in one population by eggs which hatched following two simulated winters (7.3%). None of the eggs m the second population hatched following the second chill period, however, some eggs in this population remained in apparent diapause at the end of two years. The potential for using observed population shifts in favor of D. barberi as an early warning of the expansion of prolonged diapause in a population is discussed

Production and use of metals and oxygen for lunar propulsion

Production, power, and propulsion technologies for using oxygen and metals derived from lunar resources are discussed. The production process is described, and several of the more developed processes are discussed. Power requirements for chemical, thermal, and electrical production methods are compared. The discussion includes potential impact of ongoing power technology programs on lunar production requirements. The performance potential of several possible metal fuels including aluminum, silicon, iron, and titanium are compared. Space propulsion technology in the area of metal/oxygen rocket engines is discussed

Kalman Filtering of Angular-Momentum-Based Attitude Parameters

This paper presents an extended Kalman filter using an attitude parameterization that is advantageous for attitude estimation of spinning spacecraft. The parameters are the angular momentum components in an inertial reference frame, the angular momentum components in the body frame, and a rotation angle. To avoid the singularity of the 7x7 covariance of this state vector arising from the constraint that the magnitude of the angular momentum vector is the same in the inertial and body frames, the Kalman filter employs the nonsingular 6x6 covariance of a reduced error state. Three of the components of this six-component error state are the usual infinitesimal attitude error angles, so the usual 3x3 attitude covariance matrix is a submatrix of the 6x6 covariance. The performance of the resulting filter is compared with that of a quaternion-based filter

How should thyroid replacement be initiated?

Levothyroxine (LT4) should be used alone as initial replacement for patients with hypothyroidism (strength of recommendation [SOR]: A). The optimal initial dose is 1.6 μg/kg/d for healthy people aged 60 years or younger (SOR: B). Patients aged more than 60 years may require less levothyroxine to achieve therapeutic serum thyroid hormone replacement, so initial replacement should be decreased to 25 to 50 μg daily (SOR: C). Since patients with known heart disease may develop dysrhythmias, angina, and myocardial infarctions when started on full replacement doses, experts recommend starting 12.5 to 25 μg daily for this population (SOR: C). Brand-name (Synthroid, Levoxyl, etc) and generic LT4 are bioequivalent (SOR: B), although the US Food and Drug Administration (FDA) does not consider these products to be interchangeable until proven therapeutically equivalent