Samarangana Sutradhara

The most plausible interpretation is that the Samarangana Sutradhara represents the pinnacle of mechanical philosophy in medieval India. Bhoja likely built working models of the automata (several temple records mention such robots in 11th-century Malwa). Regarding the Vimana, it is entirely possible that Bhoja built a heavier-than-air glider or a hot-air balloon using mercury as a ballast, but not a spacecraft.

Samarangana Sutradhara is a 11th-century Sanskrit treatise traditionally attributed to King Bhoja of Dhar (r. c. 1010–1055 CE). The title literally means “the charioteer (sutradhara) of the battlefield (samarangana),” but the work is best known as a compendium on architecture (vastu), town planning, sculpture, mechanical devices, and related arts. It survives in multiple manuscript traditions and has been studied by historians of architecture, art historians, and scholars of medieval Indian technology. samarangana sutradhara

The most controversial and exciting passage in the Samarangana Sutradhara describes the propulsion system: The most plausible interpretation is that the Samarangana

"Strong and durable must the body of the Vimana be made, like a great bird of light material. Inside, place the mercury engine with its iron heating apparatus. Beneath the mercury, set the fire. By the power of the latent heat, the mercury generates the driving force of the thunderstorm. The pilot, seated inside, can travel through the sky from one continent to another, or from one world to another." "Strong and durable must the body of the

Bhoja claims that using a sealed iron vessel containing mercury, heated by a controlled fire, produces a "roaring thrust." Modern readers immediately recognize an attempt at creating a thermal expansion engine or a vortex turbine. While mercury has a high coefficient of thermal expansion, it cannot produce lift on its own. However, historians of science note that Bhoja was describing a ducted fan principle—where the expanding mercury vapor drives turbines that spin external rotors.