A team of researchers at the University of Texas, USA, is developing a new type of reentry heat shield that sweats to reduce temperature and protect spacecraft.
According to the website Inovação Tecnológica, the shield will release a cooling liquid, emitted through a special material filled with microchannels, which the team is building using 3D printing. When the fluid exits the microchannels and meets the heat wave, it vaporizes into gas, creating a cooling “cushion” that prevents damage to the shield itself.
The team believes this technology could give a major boost to the use of reusable spacecraft. Traditional spacecraft rely on ablative heat shields, which burn away completely, or ceramic tiles, which often need to be replaced between flights. A spacecraft capable of sweating could potentially eliminate the need for traditional shields entirely, using a method the team calls transpiration cooling.
“We must consider that the surface of the material is cooler at hypersonic speeds when a coolant flow is introduced, compared to the baseline when there is no coolant,” said William Matthews, a member of the team.
Since the gas released by the sweat insulates the vehicle, disposable heat shields (which NASA has been trying to develop for decades) would no longer be necessary. This could reduce the turnaround time between flights from months, as was the case with the old space shuttles, to just a few hours — more like the turnaround time of a commercial jet.
The idea of making a spacecraft sweat is not new, but the team believes the tools are finally available to make it a reality — especially in terms of available materials, computing power for simulations and optimization, and laboratories to test prototypes.
For transpiration cooling in spaceflight to succeed, the spacecraft’s outer material must be strong enough to withstand extreme pressure but porous enough to allow the coolant to escape through its pores. The material chosen is silicon carbide, and the team is using additive manufacturing to precisely build the internal channels. The first set of prototypes is already being tested in a high-speed wind tunnel.
“We must consider that the surface of the material is cooler at hypersonic speeds when a coolant flow is introduced, compared to the baseline when there is no coolant,” said Matthews. “Depending on how the gas penetrates the material, there are many potential uses for this technology, and these tests should help us decide which direction to pursue.”
The research is being conducted in collaboration with Canopy Aerospace, a company specialized in thermal protection systems, which is expected to fund an actual test mission involving spaceflight and atmospheric reentry.
Source: Diário Económico
