Barely six million kilometers from the solar surface, radiation is almost five hundred times more intense than in Earth's orbit. Into this space inferno NASA's Parker Solar Probe periodically ventures, having also become the fastest human-built object in history by grazing 700,000 kilometers per hour. The great engineering question was obvious: how to prevent the scientific instruments on board from evaporating in a matter of seconds?
The answer lies in its Thermal Protection System (TPS), a circular front shield 2.4 meters in diameter and just 11.4 centimeters thick. Far from being a solid block of heavy metal, the shield weighs just 73 kilograms. Its secret is a structure composed of a carbon foam core—made up of 97% microscopic empty space—sandwiched between two sheets of high-density reinforced carbon fiber.
The face exposed to the Sun features an ultra-reflective white ceramic coating based on aluminum oxide, designed to bounce off most of the heat before it penetrates the structure. Thanks to this insulating architecture:
- The front surface unflinchingly withstands extreme temperatures of up to 1,400 °C, glowing red-hot in front of the solar flare.
- Just eleven centimeters behind, in the protective shadow cast by the disk, the circuits, computers, and sensors stay at a comfortable 25 °C to 30 °C.
To power the spacecraft without incinerating its photovoltaic panels, the probe gradually retracts them into the shield's shadow as it approaches perihelion, leaving exposed only a small strip internally cooled with pressurized deionized water.
Source: NASA / Johns Hopkins University Applied Physics Laboratory (JHUAPL) - Parker Solar Probe Science Operations
