It's not...wait, it IS rocket science!

A new faculty member faces challenges associated with meeting and balancing various teaching, research, and citizenship demands. This includes managing students as part of developing a research program. Despite the vital importance of this skill, effective employee management is not something a student inherently learns in graduate school nor does it often receive attention as part of new faculty development workshops. This paper discusses lessons learned regarding research student management at an institution with an active student-based acoustics research group. These include setting a scholarly goal at the outset with specific result-driven milestones and clear expectations of the "end game," adopting a management style that is best suited to each student's personality, adapting the project where possible to student strengths, and helping them learn to write as early as possible. Graduate students can be trained to become effective peer mentors of undergraduate students, increasing both a sense of teamwork and overall productivity. New faculty members will benefit from actively seeking mentoring from more experienced colleagues who have successfully built student-based research programs.

Near-field characterization of the acoustical environment near rockets has often involved extrapolating far-field measurements. However, because far-field amplitude data reveals only limited information about source characteristics, a vector intensity measurement system and analysis package has been developed to examine source features more directly. This paper describes the development of this measurement and analysis capability and its application to a horizontal firing of a GEM-60 solid propellant rocket motor firing conducted at ATK Space Systems near Promontory, Utah. An analysis of near-field intensity data provides insight both into the spatial extent and principal radiation lobe as a function of frequency. For the far-field peak frequencies in this lobe, the dominant source region derived from tracing the near-field intensity vectors is centered at 25 diameters downstream of the nozzle and spans approximately 15 diameters, with peak radiation at ~68 degrees. At high frequencies, the radiation results from a more contracted region that occurs farther upstream and is directed at about ~85 degrees. These results point to the potential utility of near-field vector intensity measurements, in part because do not agree completely with historical far-field models.

A theoretical model for the ground reflection from a correlated, extended source and including atmospheric turbulence [K. L. Gee et al., Proc. Mtgs. Acoust. 22, 040001 (2014)] is used to correct spectra measured over snow-covered terrain during a horizontal solid rocket motor firing. A sensitivity analysis reveals that at moderate distances, the relative sound pressure level changes are more sensitive to ground effective flow resistivity and microphone height, whereas at long range, the turbulence parameters and ground impedance have greater impact

The effects of nonlinearity on the power spectrum of jet noise can be directly compared with those of atmospheric
absorption and geometric spreading through an ensemble-averaged, frequency-domain version of the generalized Burgers
equation (GBE) [B. O. Reichman et al., J. Acoust. Soc. Am. 136, 2102 (2014)]. The rate of change in the sound pressure level
due to the nonlinearity, in decibels per jet nozzle diameter, is calculated using a dimensionless form of the quadspectrum of the
pressure and the squared-pressure waveforms. In this paper, this formulation is applied to atmospheric propagation of a
spherically spreading, initial sinusoid and unheated model-scale supersonic (Mach 2.0) jet data. The rate of change in level due to
nonlinearity is calculated and compared with estimated effects due to absorption and geometric spreading. Comparing these
losses with the change predicted due to nonlinearity shows that absorption and nonlinearity are of similar magnitude in the
geometric far field, where shocks are present, which causes the high-frequency spectral shape to remain unchanged.

The spatial variation in vector acoustic intensity has been calculated between 100 and 3000 Hz near a high-performance military aircraft. With one engine of a tethered F-22A Raptor operating at military power, a tetrahedral intensity probe was moved to 27 locations in the geometric near and mid-fields to obtain the frequency-dependent intensity vector field. The angles of the maximum intensity region rotate from aft to sideline with increasing frequency, becoming less directional above 800 Hz. Between 100 and 400 Hz, which are principal radiation frequencies, the ray-traced dominant source region rapidly contracts and moves upstream, approaching nearly constant behavior by 1000 Hz.

Measurements of the sound field near an F-35B during vertical landing operations are reported. Data are presented and discussed from the approach, hover, and descent of the aircraft, and compared with ground run-up measurements. Overall levels are comparable to published values for the F-35A at 50% engine thrust ratio during ground run-ups. One-third-octave spectra are also presented, and spectra from various stages of the approach and landing are compared. Changes in the spectral shape during the landing process are discussed and impingement is presented as a possible cause of these changes. The azimuthal directivity of the sound field during hover and descent are shown for the purpose of environmental modeling, showing slight directivity during the hover process and little to no directivity during the descent. An analysis of nonlinear propagation metrics gives values again consistent with those found for the F-35A operating at 50% engine thrust ratio during ground run-up.