Method of damping nutation motion with minimum spin axis attitude disturbance

In a method of and apparatus for damping nutation of a spinning spacecraft, spin axis attitude disturbances are substantially reduced by controlling at least one nutation damping gas thruster to fire with nonuniform gas pulses. During the beginning of a nutation control sequence, the duration of successive gas pulses is gradually increased (up pulsed) from zero to a predetermined maximum duration. The duration of successive pulses is then maintained constant for a time period. Finally, at the end of the nutation control sequence, the duration of successive gas pulses is gradually reduced to zero (down pulsed). Up pulsing of the gas thruster is initiated in response to a predetermined maximum nutation angle measured by an accelerometer. Down pulsing of the thruster is initiated in response to a predetermined minimum nutation angle

Active nutation controller

An apparatus is described for controlling nutation motion in a spinning body, comprised of an angular accelerometer with its input axis perpendicular to the spin axis of the body, a flywheel with an axis of rotation perpendicular to the axis of the accelerometer and to the spin axis of the body, and a motor for driving the flywheel to attenuate or build nutation. The motor is controlled by circuitry that monitors the output of the angular accelerometer and drives the motor clockwise or counterclockwise during predetermined nutation angles synchronized to the zero crossover points of the accelerometer signal centered about the nutation peaks. The motor drive is phased to damp nutation motion to zero for stabilization. To increase the noise immunity of the system, when the output of the accelerometer falls below a threshold level, the circuitry operates in an open loop, beat mode where data representing the last accelerometer signal that exceeded that threshold level is stored, and the motor drive is controlled by the stored data. In a second version, the motor is controlled to supply a predetermined amount of nutation motion to a body undergoing testing on a spin table for energy dissipation evaluation. In each version, the use of an angular accelerometer rather than a linear accelerometer or gyro to monitor nutation enables placement of the nutation control apparatus at any location relative to the spin axis of the body requiring only crude orientation and no calibration

Ion mass spectrometer experiment for ISIS-2 spacecraft

The International Satellite for Ionospheric Studies (ISIS) program of NASA was the longest duration program in NASA history. A number of satellites were flown under this program, the last being called ISIS-2, which was launched on April 1, 1971 and operated successfully for over 13 years. An experiment called the Ion Mass Spectrometer (IMS) was flown on the ISIS-2 spacecraft. It operated for 10 years providing a large data base of positive ion composition and ion flow velocities along the orbit of the satellite, the latter being circular at 1400 km with a 90 degree inclination. The data were processed and reside in the National Space Sciences Data Center

Molecular wake shield gas analyzer

Techniques for measuring and characterizing the ultrahigh vacuum in the wake of an orbiting spacecraft are studied. A high sensitivity mass spectrometer that contains a double mass analyzer consisting of an open source miniature magnetic sector field neutral gas analyzer and an identical ion analyzer is proposed. These are configured to detect and identify gas and ion species of hydrogen, helium, nitrogen, oxygen, nitric oxide, and carbon dioxide and any other gas or ion species in the 1 to 46 amu mass range. This range covers the normal atmospheric constituents. The sensitivity of the instrument is sufficient to measure ambient gases and ion with a particle density of the order of one per cc. A chemical pump, or getter, is mounted near the entrance aperture of the neutral gas analyzer which integrates the absorption of ambient gases for a selectable period of time for subsequent release and analysis. The sensitivity is realizable for all but rare gases using this technique

Development of a miniature mass analyzer and associated instrumentation for improved capabilities in the analysis of low energy plasmas from a rocket or satellite platform

The University of Texas at Dallas (UTD) Center for Space Sciences (CSS) has designed, developed, and fabricated three miniature mass spectrometers and their associated instrumentation in fulfillment of a NASA contract. The ion mass spectrometer analyzers furnished under this contract were modeled after a unit developed during a previous NASA grant. Three assemblies are described: (1) the magnetic sector; (2) the ion detector; and (3) the amplifier and power supply

Analysis of data from the Pioneer Venus Sounder Probe mass spectrometer

The composition of the lower atmosphere of the planet Venus from 62 km to the surface was measured by a neutral gas mass spectrometer onboard of the Pioneer Venus Sounder Probe. Fifty-one mass spectra were obtained with an average altitude resolution of approximately 1 km. The instrument measured the composition of the gases relative to CO2, the dominant gas, that is sampled from the Venus atmosphere through a special leak. The mass range extended from 1 to 208 amu with a sensitivity of the order of 1 ppm relative to CO2, but for the noble gases it was nearly 100 times better. A description of the instrument and the initial results are reported

Continuation of data analysis from the ion mass spectrometer on the ISIS-2 spacecraft

The spectrometer measures the composition and number density of the positive ion species in the ionosphere as well as the ion flux normal to the spacecraft trajectory. The measurement of high latitude ionospheric dynamics is reported. Plans for an empirical composition model of the polar ionosphere at 1400 km altitude consisting of maps of the major constituent are also reported

Spaceflight performance of silver coated FEP Teflon as a thermal control surface on the IMP-1 spacecraft

A second surface mirror type coating, vapor deposited silver on FEP Teflon, was used as a thermal control surface for one of the experiments aboard the Imp-I spacecraft. This coating was selected to obtain the low operating temperature required for this experiment. Initial flight temperature of this thermal control surface was -70.5 C, very close to the predicted value of -73 C and at a very satisfactory level. Since temperatures within the spacecraft interior are not at this desired low level, the detectors had to be mounted exterior to the spacecraft with a good view of space, preferably in an area shaded from sunlight. When this latter preference proved unobtainable, the detectors were mounted on an aluminum plate located on the exterior of the spacecraft, parallel to the spin axis but rotating about the solar vector. The mounting plate was approximately 6.5 inches by 7.5 inches by 0.125 inches thick. To achieve the desired temperature level with the mounting plate in such a location, the thermal design had to minimize not only the effects of the relatively warm spacecraft environment but also the effects of the incident solar energy

German banks as financial department stores

Germany ; Banks and banking - Germany