circular orbit

““Mardán-i-Ghayb” (Pers.), a “class of people mounted on clouds,” invisible, but moving in a circular orbit round the world, and suggesting the Hindu “Lokapálas.””

The Book of The Thousand Nights And A Night

“This was the classical method of transferring from one circular orbit to another circular orbit with the greatest efficiency, as suggested by German engineer Walter Hohmann (1880–1945) in his 1925 book Die Erreichbarkeit der Himmelskörper (The Attainability of Celestial Bodies).”

Simon & Schuster: First Man