Conrad Haas (1509–1576) was a military engineer for the Kingdom of Hungary and Principality of Transilvania, who is often cited as the first person to describe a multistage rocket in writing, although some historians attribute that distinction to Jiao Yu in 14th Century China.
Haas was perhaps born in Dornbach (now part of Vienna). As the Zeugwart (equipment manager) and arsenal master of the Imperial Austrian army under Ferdinand I. Stephen Báthory, the grand prince of Transylvania invited Haas to Hermannstadt, Siebenbürgen (now Sibiu, Transylvania, Romania) in 1551, where he was the engineer of the weaponry and also he started to teach at Klausenburg (now Cluj-Napoca).
Between 1529 and 1556, he wrote a book in German language in which he described rocket technology, involving the combination of fireworks and weapons technologies. This manuscript was discovered in 1961, in the Sibiu public records (Sibiu public records Varia II 374).
In this work Haas dealt with the technical details of rocket construction, explaining the working principles of a rocket. He described many rocket types, including the multi-stage rocket, bundled rockets, and the idea of modern spacecraft. His work also dealt with the theory of motion of multi-stage rockets, different fuel mixtures using liquid fuel, and introduced delta-shape fins and bell-shaped nozzles.
In the last paragraph of his chapter on the military use of rockets, he wrote (translated):
"But my advice is for more peace and no war, leaving the rifles calmly in storage, so the bullet is not fired, the gunpowder is not burned or wet, so the prince keeps his money, the arsenal master his life; that is the advice Conrad Haas gives."
Before discovery of Haas' manuscript, the first description of the three-stage rocket was in Poland credited to the Polish artillery specialist Kazimierz Siemienowicz in his 1650 work, Artis Magnae Artilleriae Pars Prima ("Great Art of Artillery, Part One").
Johann Schmidlap, a German fireworks maker, is believed to have experimented with staging in 1590, using a design he called "step rockets."
- (German) "Erstlich schöne Racketten mancherley Art" (article by Richard Friebe)
- (German) Conrad Haas: Raketenpionier in Siebenbürgen
- Conrad Haas in: Austrian Space and Rocket Pioneers Text by B. Besser and painting by G.Deutsch
- "Conrad Haas oder Das Spiel mit dem Feuer" a film by Frieder Schuller 1984
- Burrows, William E. (1998). This New Ocean: The Story of the First Space Age. ISBN 0-679-44521-8.
- Doru Todericiu: Preistoria Rachetei Moderne. Manuscrisul de la Sibiu 1529 - 1569, Editura Academiei RSR, Bucuresti, 1969
- Doru Todericiu: Preistoria Rachetei Moderne. Manuscrisul de la Sibiu 1529 - 1569, Editura Academiei, Bucuresti, 2008