A passive CMC/Nano-insulation thermal protection system (TPS) for the protection of hypersonic antennas
Creators: name: Karkasinas, Vasileios
Publisher: name: University of Surrey
Year: 2023

description: The target of this present MPhil thesis is to define a thermal protection system (TPS) for the protection
description: of antennas found in hypersonic applications. The term hypersonics is referred to the new generation
description: hypersonic cruise missiles (HCM) or hypersonic glide vehicles (HGV) whose aim is to glide within the
description: earth’s atmosphere while travelling at velocities above Mach 5.<br>
description: <br>
description: The study started with a literature review whose aim was to understand the current advancements in
description: hypersonic technology, their operational environment, the materials used for their TPS design and the
description: current testing trends. The literature review concluded that although there is no publicly available
description: data relating to HCM and HGV, due to their low technology readiness level (TRL) and security
description: restrictions, some knowledge can be transferred by looking at either space re-entry applications or
description: University publications.<br>
description: <br>
description: The first challenge to overcome was relating to the operational requirements of such vehicles and
description: specifically the aerothermal environment. To understand which materials are appropriate for such
description: applications, the thermal loads should be quantified. This is addressed in the second chapter of the
description: report by using aerothermal simulations based on computational fluid dynamics (CFD) and finite
description: element analysis (FEA). The reference mission for this analysis was provided by DSTL and it is based
description: on a generic HGV mission profile. The analysis was able to quantify the temperatures, thermal shock,
description: pressure, and stress levels experienced in such missions. The confidence in those results was also
description: evaluated using some validation cases. Some analysis uncertainties were also assessed and the
description: simulations were implemented based on pessimistic assumptions to make sure that aerothermal loads
description: are not underpredicted.<br>
description: <br>
description: Using the aerothermal analysis, a large number of TPS architectures were evaluated. It concluded that
description: an oxide CMC-nanoporousinsulation sandwich panel was the most promising solution. This was based
description: mainly on thermal, dielectric, damage tolerance, and oxidation resistance considerations. A 15mm
description: thick TPS consisting of an oxide CMC skin and silica or alumina-based nanoporous insulation was able
description: to sustain aerothermal loads up to approximately 1600 Kelvin for duration times up to 15 mins. It was
description: also able to insulate the rear face of the TPS so the antenna does not reach temperatures above its
description: operational limit. Those theoretical calculations were also backed by simple thermal experiments
description: using a Quartz IR lamp and a butane torch. The conclusions from the tests and the aerothermal
description: analysis were in-line and that gave confidence that the proposed architecture can operate in hightemperature environments.
description: Some fractography analyses using OM, SEM and EDS were undertaken to evaluate the material
description: damage after the thermal exposure. It was also used to assess the formation of elements that can limit
description: the TPS RF transmission, such as carbon formation. The suggested TPS did not show any indication of
description: RF performance degradation in that sense but to validate such a conclusion, dielectric measurements
description: should be taken. A purely theoretical assessment of how the dielectric strength degrades with
description: increased radome thickness was also presented. According to that, the 15mm thickness is still within
description: acceptable limits.<br>
description: <br>
description: The work concludes that the proposed TPS architecture of oxide CMC-mica-nanoporous insulation is
description: promising for its use in hypervelocity missiles and its operational limits were defined. This statement
description: is backed up by low TRL testing and theoretical assessments. For more in-depth conclusions, higher
description: TRL assessments are required in a representative working environment.<br>