What Kind of Heat Shield Will the Dragon 2 and Starliner Spacecraft Use? Silica Tiles vs. Ablative Materials
The Dragon 2 and Starliner spacecraft, developed by SpaceX and Boeing respectively, employ different heat shield technologies compared to the Space Shuttle. Instead of using silica tiles, these newer spacecraft utilize ablative materials, a development that is transforming reusability and efficiency in space exploration.
Dragon 2 Crew Dragon Heat Shield: PICA-X Ablative Material
The heat shield of Crew Dragon is made from a material called PICA-X, which stands for Phenolic Impregnated Carbon Ablator. This technology is derived from NASA’s own applications, specifically from the AVCOAT material used in the Apollo program. PICA-X is engineered to withstand intense re-entry temperatures and pressures, yet it allows for some degree of reuse after each mission. However, it is not designed for as many cycles as the silica tiles used in the Space Shuttle, making it a more cost-effective and efficient solution for modern space missions.
Starliner Heat Shield: Avcoat and Proprietary Ablative Materials
The Starliner spacecraft developed by Boeing also uses ablative materials for its heat shield. Specifically, it employs a material known as Avcoat, which is similar to the ablative materials used in the Apollo program. Avcoat is engineered to erode during re-entry, effectively dissipating heat away from the spacecraft. This process is crucial for protecting the integrity of the Starliner during high-speed re-entry.
Differences in Heat Shield Technologies
Both Crew Dragon and Starliner utilize ablative heat shield technologies, albeit with some key differences. SpaceX’s PICA-X is described as a nominally ablative material, meaning it sheds small amounts of material to dissipate heat. However, the description is nuanced: PICA-X is designed to be reusable in a different manner than the traditional ablative materials of the Apollo era. It starts with a lighter weight than the AVCOAT and undergoes a process known as pyrolysis during re-entry, which forms a heat-resistant char layer. This char layer, while still possessing some ablative properties, is more akin to the shuttle tile’s black leading edge tiles in terms of its resistance to heat and its ability to heal minor defects through the growth of new char layers.
Interestingly, while PICA-X does shed material, its primary function is more insulative than ablative. It can be classified as a reusable ablative, as it can withstand multiple re-entries before needing replacement or repair. In contrast, traditional ablative materials are typically used once and discarded.
Furthermore, Starliner employs a proprietary blunt-end ablative material as well as proprietary thermal protection tiles used on the Space Shuttle. These materials are designed to withstand the extreme conditions of re-entry while providing additional protection and ensuring the spacecraft’s integrity.
Conclusion
Both the Dragon 2 and Starliner spacecraft have developed innovative heat shield technologies that balance between ablation and reusability. PICA-X and Avcoat represent significant advancements in material science, offering a bridge between the traditional ablative materials used in the Apollo era and the more sophisticated thermal protection systems of modern spacecraft. These technologies not only enhance the efficiency and cost-effectiveness of space missions but also pave the way for more ambitious and sustained exploration of outer space.
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