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Total aerodynamic forces and moments of free flying body in wind tunnel determined from accelerations measured and telemetered by onboard instruments
A test program was conducted involving forty-five drops of liquid propellant in instrumented tanks. Biaxial, low-g accelerations were applied to the model propellant tanks during free-fall testing, and forces exerted during liquid reorientation were measured and recorded. High speed photographic records of the liquid reorientation were also made. The test data was used to verify a mechanical analog which portrays the liquid as a point mass moving on an ellipsoidal constraint surface. The mechanical analog was coded into two FORTRAN 4 digital computer programs. Results showed excellent correlation between test data and analytical predictions of reorientation forces and liquid center of mass motion, verifying the basic analytical approach.
Gravity gradiometry is recognized to be a very difficult instrumentation problem because extremely small differential acceleration levels have to be measured, 0.1 EU corresponds to an acceleration of 10 to the minus 11th power g at two points 1 meter apart. A feasibility model of a gravity gradiometer is being developed for airborne applications using four modified versions of the proven Model VII accelerometers mounted on a slowly rotating fixture. Gravity gradients are being measured to 1.07 EU in a vertical rotation axis orientation. Equally significant are the outstanding operational characteristics such as fast reaction time, low temperature coefficients and high degree of bias stability over long periods of time. The rotating accelerometer gravity gradiometer approach and its present status is discussed and it is the foundation for the orbital gravity gradiometer analyzed. The performance levels achieved in a 1 g environment of the earth and under relatively high seismic disturbances, lend the orbital gravity gradiometer a high confidence level of success.
Structural dynamic environmental test levels were developed for the thematic mapper instrument, components of the Tandberg-Hanssen instrument, and components of the International Ultraviolet Explorer spacecraft using NASTRAN structural models and test data. Both static and dynamic NASTRAN analyses were used. The model size required could be as small as 300 degrees of freedom for the static analysis and as large as 4000 degrees of freedom or more for the high frequency dynamic analysis. An important step in the development of the levels is model verification by test. The launch environments that generally dictate many important features of the design of an instrument or component are steady state acceleration, sinusoidal vibration, and random vibration.
Electron and ion plasma measurements on Solar Probe are important, especially to elucidate the role of coronal holes as sources of the solar wind and to resolve the long debated question of the importance of wave heating within 20 solar radii to the acceleration of the solar wind. Adaptable instruments are required to cover the large dynamic range of parameters between 1 AU and 4 solar radii. The baseline mission would be improved, in some respects, by the addition of a second spacecraft, following the first by a distance of several solar radii. A spinning spacecraft would be satisfactory, but not essential, for the present objectives. Attention should be paid to having the heat shield electrically conducting. An instrument for ion and electron (but no composition) measurements would have a mass of approximately 10 kg, require 8 w of power, and generate data at a maximum rate of approximately 2 kbits/sec.
The spectrum of cosmic-ray electrons has been measured with an instrument that combines a transition-radiation detector with a shower detector. The transition-radiation detector provides unique identification of individual electrons and good discrimination against protons. At the same time, it allows the construction of a large-area instrument (0.48 sq m ? ster) and consequently makes possible a measurement of improved statistical accuracy. The instrument has been calibrated with electron beams of 5-300 GeV at Fermilab, thus eliminating energy-dependent biases. A first balloon flight yielded 30 hours of data at an altitude of 5 g/sq cm. The design of the instrument is described, along with the accelerator calibrations and the analysis of the balloon flight data. The spectrum of electrons is found to be significantly steeper than that of protons over the whole energy range.
Ion acceleration is a well known phenomenon at both interplanetary shocks, while there have been only a few reports concerning an acceleration of electrons at interplanetary shocks. The considered investigation reports that electron acceleration occurs at many shocks. The instrumentation used is discussed, taking into account the ISEE 3 (International Sun Earth Explorer) spacecraft and the electrostatic analyzer employed for the measurement of electrons. Changes in the electron distribution function caused by shocks are found to be quite varied. Some events show a simple step to a higher flux level, some show fluctuations as the flux rises, and some have one or more pulses at the time of the shock. Attention is given to data obtained on July 26, 1979, December 25, 1978, and November 12, 1978. A calculation of shock geometries is also reported.
A mass spectrometer which can be used to measure relative ion concentrations in a multiion component plasma has been designed for use in a strong (1-4-kG) uniform magnetic field. The spectrometer features an acceleration region which accelerates thermal ions through a series of three tantalum electrodes at a 30 deg angle to the B field, and a collection region in which ions are selectively collected, depending on the size of their gyroradii, by a cylindrical collector. Relative ion concentrations are determined from measurements of the collector current as a function of accelerating voltage. Results obtained using this instrument in a Q-machine device operated with a two-ion (Cs+/K+) component plasma are presented.
The Pinhole/Occulter Facility (P/OF) consists of state-of-the-art instruments for the study of particle acceleration in the solar corona, and uses a large structure to obtain very high angular resolution. P/OF has been studied in the past as an attached payload for the Space Shuttle, and has been the subject of study by a NASA Science Working Group (P/OFSWG). Appendix A lists various technical studies and reports carried out under the auspices of P/OFSWG and the Program Development Office of NASA Marshall Space Flight Center. Under the rationalization of NASA flight opportunities following the Challenger disaster, and the beginning of the Space Station Freedom program, the sortie-mode deployment of P/OF seemed less efficient and desirable. Thus, NASA decided to reconsider P/OF for deployment on the Space Station Freedom. The technical studies for this deployment continue at the present and will evolve as our knowledge of Space Station architecture and capabilities increase. MSFC contracted with Teledyne Brown Engineering for these technical studies.
The Microgravity Science and Applications Div. (MSAD) of the NASA Office of Space Science and Applications (OSSA) is responsible for encouraging and directing the research of a wide range of physical phenomena in reduced gravity. Under MSAD's direction, NASA-Lewis is presently developing the concept of a multiuser facility which will perform combustion science experiments in space. This facility, the Combustion Experiment Module (CEM), will be located in either the Shuttle Spacelab or the Space Station Freedom lab and will be operational by mid-1997. In addition to standard instrumentation to measure temperature, pressure, and acceleration, CEM shall use a variety of imaging and optical diagnostic techniques. Images shall be the primary source of experimental data. These images create an enormous amount of data which must be archived on orbit for later analysis. Also, ground based investigators will require enough data from the orbiting facility to determine if the experimental parameters need to be changed before proceeding with the next run. The storage and transmission of this data present a major challenge to the CEM design. Data compression will play a major role in the design of the CEM diagnostics system.
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Disclosed is an impaction densitometer having a chamber configured to receive a particle; a beam generator configured to emit a beam; a detector configured to receive the beam and convert a change in intensity of the received beam into an electrical signal corresponding to a particle volume; an impact sensor positioned a known distance from the beam and configured to measure a particle momentum as a function of an impact energy transferred from the particle to the impact sensor; a velocity calculator configured to calculate a particle velocity based on a time it takes the particle to pass through the beam and strike the impact sensor; a mass calculator configured to calculate a particle mass as a function of the particle momentum and velocity; and a density calculator configured to calculate a particle density as a function of the particle mass and volume.
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