Aerothermal Heating Methodology in the Spacecraft Aerothermal Model (SAM)

Spacecraft are typified by complex geometries meaning that predictive tools designed to assess entry, break up and ground casualty risk are not naturally suited to high fidelity modelling treatments (e.g. the CFD and FE analysis which are prevalent in the assessment of entry vehicle design and performance). Simplifying assumptions are inevitable and the consequences of these simplifying assumptions need to be investigated and quantified.

The present paper is concerned with the effect of these simplifying assumptions on ground casualty risk. Specifically we report on work concerning: (i) a discussion and appraisal of some current aeroheating models as implemented in well-known tools (ii) proposed potential improvements to existing models and (iii) novel approaches to aeroheating engineering modelling.

These topics are investigated in the framework of the recently developed Spacecraft Aerothermal Model tool (SAM) which can be configured to calculate ground casualty risk using varying degrees of aerothermal and break up model complexity. This allows us to investigate the sensitivity of ground casualty risk to simplifying assumptions. Parameter studies performed so far have highlighted the sensitivity of ground casualty risk to the treatment of fragment aeroheating. SAM has the option to calculate the aeroheating to fragments taking the component size, orientation and shape into account. This goes beyond simple panel inclination methodologies in common use, but is nonetheless based on established engineering correlations. As far as the authors are aware, such a methodology is not currently used by any of the well-known spacecraft breakup tools. The consequence of this novel treatment of fragment heating is the main topic of the current paper.