Trinesium was an element that could be used in the construction of starship hulls. It had properties which enabled such vessels to withstand temperatures up till 18,000° Celsius and therefore enter the photosphere of most G-type stars.
The Vissians started using trinesium to construct starship hulls in the first half of the 21st century and still used it by 2153. Their shuttles could withstand twice the temperatures their ship. (ENT: "Cogenitor")