The Ablation Workshop provides a single meeting point for integration and advancement of a multi-disciplinary research community of scientists and engineers working on aerothermodynamic ablation. This research community has members representing government agencies, the private sector and university systems across the world. The workshop usually attracts more than 150 participants across these institutions from all over the world. The primary objectives of the workshop are to:
- foster improved communication across national boundaries;
- expose the aerothermodynamic ablation modeling community to new ideas and techniques from adjacent disciplines;
- bring new experimental techniques to bear on the problem;
- discuss challenges faced in adapting existing techniques to address new applications.
The topic area encompasses the physics and chemistry relevant to the surface of objects traveling at high speed inside planetary atmospheres, such as re-entry spacecraft, Inter-Continental Ballistic Missiles (ICBM) or inertial projectiles. At hypersonic speeds, strong shock waves form in front of the object, and the boundary layer is typically highly turbulent, leading to complex compressible fluid dynamics. Such conditions are further characterized by dissociation, ionization, and excitation of the gaseous species behind the hypersonic shock wave. At sufficiently high velocity, the hot gas begins radiating due to atomic and molecular excitation. This radiation can become strong enough that it is a significant source of heat transfer to the spacecraft. At the higher entry velocities, the heat generated at the vehicle surface is large enough that no material can withstand it without degrading. Therefore, a vehicle design typically relies on ablating thermal protection materials, which are intended to pyrolize and char in response to the incident heat. These materials thus efficiently cool the vehicle via: (1) energy absorption due to endothermic breakdown of the polymeric constituents; (2) transpiration cooling as the pyrolysis gases percolate from the interior of the material toward the surface; and (3) re-radiation from the hot char layer that forms on the surface. At high altitude conditions typical of atmospheric entry, many or all of these processes can be in non-equilibrium, which greatly complicates the required physical models that must be employed in their simulation. Finally, all of these phenomena, including the fluid dynamics, molecular chemistry, radiation emission and transport, and ablative material response, can be coupled, requiring the development and validation of complex multi-physics models. Such models exist today at varying levels of fidelity and validation.
Although a significant impediment to properly validating the models has been inability to conduct truly flight-like experiments in ground-based laboratories, collaborative activities such as the Ablation Workshop can advance the current state of the art by bringing new ideas and methodologies to bear on the problem.