Speakers
Description
When simulating space debris during atmospheric entry, the thermal environment is often modelled using heat flux correlations, with the resultant thermal loads being averaged over simplified representations of spacecraft (complex compound shapes composed of geometric primitives). Although this procedure is computationally efficient, the application of averaged heat fluxes to such compound shapes can lead to what is known as the multiscale heating problem, where an inappropriate length scale is used to assess the magnitude of a given heat flux. This can potentially result in significant inaccuracies being introduced in debris temperature history, demise altitude, and ground casualty risk projections.
CRITIC, a new tool that wraps the SESAM code included in ESA's DRAMA debris simulation suite, has been developed in order to demonstrate a solution to this issue. CRITIC is designed to address the multiscale heating problem by intervening in a standard SESAM analysis at breakup and demise events in order to calculate thermal scaling factors based upon the overall size of a compound shape. These factors are then generated for and applied to any "new" compound shapes that result from breakup events, and the SESAM analysis is continued until the next such event.
CRITIC is found to perform well when run on simplified test cases, achieving excellent agreement in thermal history between compound shapes and geometrically similar single-component shapes. A significant difference in ground risk assessment is also found between cases run with and without CRITIC scaling. Although the work performed here provides a good proof of concept, significant effort would still be required to generally apply this methodology, both in terms of gathering the required data from CFD and experiments as well as in determination of appropriate lengthscales for more complex shapes.
