Multiresolution non-stationary techniques for the characterization of transient pressure signals embedded in broadband plume noise

Abstract

The acoustic environment generated by the Space Shuttle propulsion system historically was considered one of the most complex rocket noise environments to predict of NASA’s heritage rockets. After the Space Shuttle was retired in 2011, the Space Launch System (SLS) architecture chosen to succeed the shuttle will generate an even more complex acoustic environment than Space Shuttle. Both Space Shuttle and SLS have dual first stage propulsion systems consisting of two Solid Rocket Boosters (SRBs) and three (Space Shuttle) or four (SLS) RS-25 LH2/LOX engines. The additional complexity for the SLS acoustic environment arises due to the in-line propulsion configuration (as opposed to the offset configuration for Space Shuttle) firing both SRB and liquid engine plume into the same exhaust duct at liftoff. For Space Shuttle, the offset configuration meant each acoustic phenomena was separable and could be predicted and analyzed individually. For SLS, the in-line configuration means the IOP waves (one per SRB) are injected directly into the steady state plume meaning the events can no longer be assumed separable. This paper discusses data from a scaled down configuration and applies wavelet analysis in attempt to extract and characterize an injected transient blast wave from steady state plume noise.