Launch Noise Research Articles

Electromagnetic Railguns and Coil Guns: Comprehensive Analysis of Physical Principles and Applications and Experimental Improvements

This research is mainly to provides a report and summary of the production and experimental principle of our last electromagnetic gun Electromagnetic guns use the basic principle in physics that moving charges or current-carrying conductors are subjected to the electromagnetic force (i.e., the Lorentz force) in a magnetic field to accelerate projectiles. According to the acceleration method, electromagnetic guns can be divided into rail guns and coil guns . An electromagnetic railgun accelerates projectiles using the fundamental principles of physics involving moving charges and current-carrying conductors interacting with a magnetic field, known as the Lorentz force. Electromagnetic Railguns accelerate projectiles to very high speeds using Lorentz force generated by strong electric pulses through parallel conductive rails . A coilgun is a device that uses electromagnetic fields to accelerate metallic projectiles. Its working principle is based on Faraday's law of electromagnetic induction. By passing current through a coil, a strong magnetic field is generated, which propels the projectile along the guide rail. Coilguns offer several advantages over traditional gunpowder-based propulsion methods, including higher initial velocities, extended ranges, reduced recoil, and lower launch noise. However, despite these potential benefits, our experimental setup revealed several limitations.This report summarizes the challenges encountered and Outlines suggested strategies for improving the design and addressing the identified deficiencies, analyzing the problem through a qualitative perspective. To provide readers with effective information

Starship super heavy acoustics: Far-field noise measurements during launch and the first-ever booster catch.

Far-field (9.7-35.5 km) noise measurements were made during the fifth flight test of SpaceX's Starship Super Heavy, which included the first-ever booster catch. Key results involving launch and flyback sonic boom sound levels include (a) A-weighted sound exposure levels during launch are 18 dB less than predicted at 35 km; (b) the flyback sonic boom exceeds 10 psf at 10 km; and (c) comparing Starship launch noise to Space Launch System and Falcon 9 shows that Starship is substantially louder; the far-field noise produced during a Starship launch is at least ten times that of Falcon 9.

Measurements of rocket landing sonic booms from three SpaceX Falcon-9 booster landings

As commercial rocket companies reduce costs, a common strategy is to design reusable rockets. The recovery typically includes propulsively landing the first stage booster near the launch site or on an ocean platform. Because the booster returns at supersonic speeds, a sonic boom is produced. This paper analyzes measurements made of three SpaceX Falcon-9 booster landings at Vandenberg Space Force Base. Each measurement uses multiple microphones surrounding the launch and landing pads at distances varying between 300–25 000 m. The Falcon-9 sonic boom waveforms have three shocks, and all three are consistently measured at every single measurement location. Although the rise times increase with distance, the duration between the shocks shows a more complicated trend, with the farthest measurements sometimes having the same duration as the nearest measurements. Farther than 1 km, the sonic boom peak overpressure can exceed the peak launch noise overpressures. Farther than a few kilometers, the sound exposure level from the sonic booms can be comparable to the exposure during the entire 12 dB-down period for the launch noise. [Research funded in part by the Oak Ridge Institute for Science and Education and Vandenberg Space Force Base.]

Overview of BYU’s acoustical measurements of the Falcon-9 SARah-1 launch, reentry sonic boom, and landing

More rockets are launching than ever before, exposing structures, environments, and communities to intense sounds and vibrations. This increased launch cadence brings about a greater need to understand the noise radiated during these launches. This paper summarizes BYU’s acoustical measurement and analysis of the Falcon 9 SARah-1 launch from Vandenberg Space Force Base in June 2022. In total, nine measurement stations were set up at locations between 400 m and 15 km from the launch pad. Additionally, this launch featured a booster landing back near the launch pad, resulting in a sonic boom about eight minutes after the launch. Each station successfully recorded the launch noise, sonic boom, and landing noise. Waveforms and spectra from the launch are discussed and compared across stations at different distances from the launch pad. The overall sound power level and other noise metrics are also discussed. [Work supported in part by NSF.]

Artemis I launch noise spectra: Effects of variable weather profiles over short- and long-range propagation paths

NASA’s Space Launch System (SLS) launched the Artemis I mission at 1:47 am local time on November 16, 2022. The timing of the night launch offered a multitude of interesting weather effects over the propagation paths to measurement locations ranging from 1.5 km to 60 km. This presentation discusses spectra at different distances from Launch Complex 39B, both inside and outside the Kennedy Space Center perimeter. Preliminary analysis of the SLS sound pressure levels and spectra suggests many propagation phenomena are at play. In addition to geometric spreading, atmospheric absorption, and nonlinear propagation, complex weather profiles and ground effects are discussed. Initial results of a single-frequency Greens-function parabolic equation model, with estimated weather profiles along the propagation paths, will be offered with approximate source and receiver height to compare levels at several locations.

Analysis of sonic booms from Falcon 9 booster landings

One drawback to the ability to land boosters of orbital launch vehicles, such as the Falcon 9, is the associated reentry sonic boom. Because of the Falcon 9 booster shape and landing orientation, the observed waveform at the ground contains three shocks (a triple boom), rather than the two associated with a traditional N-wave. To assess the impact of these sonic booms, acoustic data from a Falcon-9 booster landing at Vandenberg Space Force Base are analyzed. The data were collected in Lompoc, CA, at locations 7-14 km away from the landing site. Waveform and spectral characteristics are examined and various metrics, including A-weighted Sound Exposure Levels (ASEL), are calculated. These metrics from the reentry sonic booms are compared with metrics calculated from the launch noise.

Spectral analysis of Firefly Alpha launch noise

On 2 September 2021, the first Firefly Alpha rocket launched from Vandenberg Space Force Base in California, USA. Acoustic data were collected at two locations 30 m and 60 m away from the launch pad, at another eight locations located on an arc with a radius of about 300 m, as well as an additional location roughly 8 km away. Around 14 s into the launch, an anomaly occurred, resulting in the premature shutdown of one of the four first-stage engines. By analyzing the overall levels and spectral characteristics of the rocket throughout the different phases of its flight, the effects of the engine shutdown on overall level and spectral peak frequency are discussed. Based on estimated engine parameters, the measured effects are compared to models for clustered nozzles.

Insights into heated, supersonic jet noise gained from writing a review article on launch vehicle noise

At the time of writing this abstract, a review article is being finalized for publication in JASA entitled a “Supersonic jet noise from launch vehicles: 50 years since NASA SP-8072,” it describes the current state-of-the-art in rocket and launch vehicle noise research, including how highly heated, supersonic rocket plumes differ from other jets, the origin and nature of the radiated sound from both free and impinging rocket plumes, and techniques for pad noise mitigation during rocket launches. Existing and candidate methods (both empirical and numerical) for modeling rocket launch noise are reviewed, including the ubiquitous NASA SP-8072 methodology, which has formed the cornerstone of many rocket launch noise prediction models over the past half century. This talk will briefly discuss some of the insights gained as a result of writing this review and show how they led to the inevitable conclusion that an entirely new approach to rocket plume noise modeling—one that incorporates the underlying physics of the noise generation mechanisms—must be pursued.

Overall sound pressure levels and peak directivity of the NROL-82 Delta IV Heavy Launch

Rocket launch noise has historically been analyzed for directivity and sound power. To compare against previous findings, this study uses data acquired from the NROL-82 Delta IV Heavy launch from Vandenberg Space Force Base, CA, USA. Rocket trajectory data are used to calculate the 3D angle between the plume and several measurement stations in the near and far fields. Overall sound pressure level, directivity, and sound power level are calculated, and the results compared across stations.

Simulations of rocket launch noise suppression with water injection from impingement pad

The focus of this work is on understanding the effect of water injection from the launch pad on the noise generated during rocket’s lift-off. To simplify the problem, we consider a supersonic jet impinging on a flat plate with water injection from the impingement plate. The Volume of Fluid model is adopted in this work to simulate the two-phase flow. A Hybrid Large Eddy Simulation – Unsteady Reynolds Averaged Simulation approach is employed to model turbulence, wherein Unsteady Reynolds Averaged Simulation is used near the walls, and Large Eddy Simulation is used elsewhere in the computational domain. The numerical issues associated with simulating the noise of two-phase supersonic flow are addressed. The pressure fluctuations on the impingement plate obtained from numerical simulations agree well with the experimental data. Furthermore, the predicted effect of water injection on the far-field broadband noise is consistent with that of the experiment. The possible mechanisms for noise reduction by water injection are discussed.

Comparative analysis of three falcon 9 launches

This study investigates the noise from three separate Falcon 9 vehicle launches from Vandenberg Air Force Base, as measured within the community of Lompoc, CA. Although one focus of these tests was to test a variety of acoustical and weather instrumentation systems and configurations, the launches also provides an opportunity to study and compare the launch noise measured under potentially different weather conditions. An analysis of the levels and spectra is shown for different time periods. The prevalence of acoustic shocks is examined in the context of environmental conditions and recording locations.

Far-field acoustic modeling of rocket noise to determine community impacts

The emerging commercial space market is generating interest in commercial launch site (“spaceport”) development around the United States. FAA regulations require all new spaceports to acquire a launch site operator’s license, which is considered a Federal action subject to environmental review. Potential noise impacts are evaluated based on FAA Order 1050.1E, Change 1, Environmental Impacts: Policies and procedures, which include the assessment of DNL and may be supplemented with additional acoustical metrics. These supplemental metrics may range from speech interference to structural damage impacts. Extensive studies and research have examined the appropriateness of these metrics in relation to aircraft operations. However, the differences between these acoustic sources and operational modes stress the need for computer models and impact criteria specific to launch vehicles. Further measurements and research are needed to improve rocket source characterization, long-range sound propagation of high amplitude waveforms through complex atmosphere, and environmental and community impacts. The evolving nature of the regulatory environment surrounding rocket noise warrants a renewed focus on appropriate noise modeling and impact criteria to determine potential conflicts with launch noise.

Semi-Empirical Methods Prediction Noise from Free Supersonic Jets

It is important to assess the effects of missile and rocket launching on the launcher health and surrounding structures. Since an accurate measurement of the launch noise environment is time consuming and extremely cost prohibitive. And nowadays, there is no reliable theoretical method. in order to calculate the sound field generated by high-speed high temperature jets. Therefore, engineering approaches are widely used in practice. In this paper considers semi-empirical jet noise models and their development and application. Listing of some the open questions and future directions concerning supersonic jet noise predictions using semi-empirical methods concludes the survey.

Perspective on launch noise: Measurement, prediction, and characterization.

The noise generated by launch vehicles is examined in terms of the key source, radiation, instrumentation, and estimation issues. Basic source and acoustic radiation characteristics of un-deflected rocket exhausts are compared and contrasted with those of supersonic jets. Next, the instrumentation demands of, and unique characterization methods applied to, rocket noise sound pressure measurements are discussed. Finally, on vehicle sound pressure measurements during the launch from a covered pad are presented. Contradictions between these loads and those predicted using traditional lift-off loads methods are highlighted. This paper concludes with a brief outline of research and instrumentation needed to improve agreement between the physics of the prediction model and the actual measured lift-off loads.

Acoustic-Seismic Detection of Ballistic-Missile Launches for Cooperative Early Warning of Nuclear Attack

In order to fill gaps in Russian early-warning systems, sensors can be deployed cooperatively near the silos of intercontinental ballistic missiles (ICBMs) that would sense a launch and would transmit continuously the information that no launch has occurred. The extremely loud launch noise propagates to kilometers and can be detected passively in all weather conditions by the induced ground motion. Buried seismic sensors minimize the intrusion and disturbance above the ground. Considerations of the propagation and acoustic-seismic transfer, as well as potential other sources of strong sound or ground motion, lead to the recommendation that acceleration sensors should be deployed at 0.1–1 km from each silo. Arrays of three sensors allow to estimate the azimuth and elevation of the source, improving discrimination from, e.g., overflying jet aircraft. The time course of signal amplitude, its maximum, and spectral characteristics provide additional characteristics to recognize a launch and other source types. One station would cost below $50,000 so that all 800 ICBM silos of the USA and Russia can be covered at around $40 million. Deployment can start after a development and testing phase of one to two years. Extension to mobile ICBMs and other nuclear states is possible.

Progress toward a ‘‘smart acoustic blanket.’’

This paper presents recent progress we have made toward the goal of developing what we call ‘‘smart acoustic blankets.’’ Such technology would have application in many acoustic areas including aeroacoustics, architectural acoustics, and traffic sound barriers in addition to our principal focus which is the reduction of launch noise sound transmission through satellite payload fairings. These smart blankets would be configured with sound actuation layers, acoustic pressure and velocity sensors, and electronic controller modules. The status of the development of each of these components as well as the overall concept will be discussed. [Work supported by ONR.]

Behavioral and hearing responses of pinnipeds to rocket launch noise and sonic boom

Loud launch noise and sonic booms from some military space vehicle launches from Vandenberg Air Force Base impact pinnipeds on the mainland and at San Miguel Island, California, and may cause stampedes, temporary threshold shift or, less likely, permanent hearing damage. Maximum fast A-weighted (MFXA) sound levels approximately 4.8 miles downrange during the launch of three Titan IV rockets were 93.2, 92.7, and 93.0 dB; average sound exposure levels were between 98.9 and 101 dB. Harbor seals fled into the water in response but many returned to land within several hours. A sonic boom was recorded at San Miguel Island during one launch. Its peak flat sound-pressure level was 129.5 dB and maximum fast A-weighted sound level was 86.2 dB; virtually all of the energy was below 500 Hz. Pinniped behavioral responses were mild and brief. Predicted overpressures for focused sonic booms from the Titan IV rocket are substantially greater (≥150 dB). Noninvasive hearing tests using ABR and OAE techniques are being used to determine if pinnipeds suffer temporary threshold shifts or permanent hearing damage from exposure to those sonic booms.

Noise criteria methodology for site selection of the proposed Hokkaido Space Center in Japan

The U. S. space program has produced an enormous amount of data useful to environmental studies. Much of the launch noise data, however, is lacking correlation with such propagation influences as meteorological conditions and terrain effects. Thus, otherwise identical noise sources, such as the Space Shuttle, yield wide variations in measured and predicted launch noise. In addition, adequate criteria for assessing launch noise impacts remain an elusive issue within the several agencies and departments responsible for the evaluation of proposed new generation launch vehicles and possible locations for future space launch facilities. In order to develop a site selection criterion based on launch noise for the proposed Hokkaido Space Center, the limited acoustic, meteorological, and terrestrial information available from launches in Florida and California was evaluated, correlated, and scaled to designated launch vehicles and potential sites. The resulting launch noise site selection methodology was used in locating an acceptable site for both equatorial and polar orbit launches while providing consideration for facility support buildings and the surrounding region of potential acoustic impact.