Our client required a solution to enable air-breathing rocket motor testing at an existing test facility located and operated within an urban environment.
The facility is situated approximately 400-600 meters from nearby residential areas, with strict local limits on instantaneous daytime noise levels.
To support future growth of the test programme, effective noise mitigation was essential, both to protect the surrounding environment and to maintain a safe and comfortable working environment on site.
Our client commissioned an acoustic concept design to identify a practical, compliant, and flexible noise mitigation solution that would allow their testing programme to expand.
Key Acoustic Challenges: Extremely High Noise Levels from Rocket Testing – air-breathing rocket motors generate very high sound power levels, particularly at low frequencies, making effective attenuation technically challenging.
Proximity to Residential Areas – the facility’s location within a populated area meant even short-duration tests could result in noise complaints even if noise limits were not exceeded.
Tight Site and Structural Constraints – limited space between the test hall and external blast deflector, sloping concrete yard and fixed building interfaces, restrictions on drilling depths due to services embedded in the building structure.
Operational Flexibility Requirements – the acoustic solution needed to be removable and re-deployable, allowing occasional solid rocket testing and future site reconfiguration without major civil works or specialist lifting equipment.
Limited Measured Data for Higher-Power Rockets – measured acoustic data existed only for lower-power tests, requiring reliable extrapolation to ensure compliance for rockets up to 12 MW. Acoustic Solution &
How Challenges Were Overcome:
Advanced Acoustic Modelling & Validation – a validated 3D acoustic model was developed using industry-leading software, with existing measured data conservatively extrapolated to represent higher-power rocket tests.
Background Noise Surveys – detailed background noise measurements were undertaken at multiple site boundaries.
Bespoke Detuner System Design – a purpose-designed, air-cooled rocket exhaust detuner system was developed, drawing on proven principles used in military aircraft test facilities, featuring an acoustic door sealing the test hall opening, multi-stage silencers, internally lined ductwork and external insulation, and flow mixing to reduce exhaust temperature.
Space-Efficient & Removable Design – the system was mounted on a skid frame with adjustable wheels, allowing it to be positioned, removed, and stored using existing on-site forklift equipment.
Noise reduction: Predicted noise levels demonstrated that the mitigated facility would reduce the noise by approximately 30 dB(A) with overall community impact estimated at only 0.5-4 dB above background noise.
Outcome: Significant reduction of noise during testing, minimal acoustic impact on surrounding community, flexible future-proof solution, operational rocket testing enabled with reduced risk of noise complaints.
This project demonstrates how detailed measurement, advanced modelling, and practical acoustic engineering can successfully resolve highly challenging noise problems, even in sensitive urban environments.
