Conrad Haas was a military engineer

Military engineer

In military science, engineering refers to the practice of designing, building, maintaining and dismantling military works, including offensive, defensive and logistical structures, to shape the physical operating environment in war...

 of the Holy Roman Empire

Holy Roman Empire

The Holy Roman Empire was a realm that existed from 962 to 1806 in Central Europe.It was ruled by the Holy Roman Emperor. Its character changed during the Middle Ages and the Early Modern period, when the power of the emperor gradually weakened in favour of the princes...

, who is believed to be the first person to describe a multistage rocket

Multistage rocket

A multistage rocket is a rocket that usestwo or more stages, each of which contains its own engines and propellant. A tandem or serial stage is mounted on top of another stage; a parallel stage is attached alongside another stage. The result is effectively two or more rockets stacked on top of or...

 in writing.

Haas was perhaps born in Dornbach (now part of Vienna

Vienna

Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...

). As the Zeugwart (equipment manager) and arsenal

Arsenal

An arsenal is a place where arms and ammunition are made, maintained and repaired, stored, issued to authorized users, or any combination of those...

 master of the Imperial Austrian army under Ferdinand I

Ferdinand I, Holy Roman Emperor

Ferdinand I was Holy Roman Emperor from 1558 and king of Bohemia and Hungary from 1526 until his death. Before his accession, he ruled the Austrian hereditary lands of the Habsburgs in the name of his elder brother, Charles V, Holy Roman Emperor.The key events during his reign were the contest...

, he went to NAGYSZEBEN, ERDÉLY (Hungarian Kingdom-Transylvania) (now Sibiu/Nagyszeben, Romania

Romania

Romania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...

) in 1551, where he oversaw operation of the arsenal.

Between 1529 and 1556, he wrote a book in German language in which he described rocket technology, involving the combination of fireworks

Fireworks

Fireworks are a class of explosive pyrotechnic devices used for aesthetic and entertainment purposes. The most common use of a firework is as part of a fireworks display. A fireworks event is a display of the effects produced by firework devices...

 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

Spacecraft

A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....

. His work also dealt with the theory of motion of multi-stage rockets, different fuel mixtures using liquid fuel, and introduced delta

Delta (letter)

Delta is the fourth letter of the Greek alphabet. In the system of Greek numerals it has a value of 4. It was derived from the Phoenician letter Dalet...

-shape fin

Fin

A fin is a surface used for stability and/or to produce lift and thrust or to steer while traveling in water, air, or other fluid media, . The first use of the word was for the limbs of fish, but has been extended to include other animal limbs and man-made devices...

s and bell-shaped nozzle

Nozzle

A nozzle is a device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice....

s.

In the last paragraph of his work, 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

Poland

Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

 artillery specialist Kazimierz Siemienowicz

Kazimierz Siemienowicz

Kazimierz Siemienowicz , was a Polish-Lithuanian general of artillery, gunsmith, military engineer, artillery specialist and pioneer of rocketry. Born in the Grand Duchy of Lithuania, he served the armies of the Polish-Lithuanian Commonwealth, a federation of Poland and the Grand Duchy, and in the...

 in his 1650 work, Artis Magnae Artilleriae Pars Prima ("Great Art of Artillery, Part One").

Haas, who remained and died in Nagyszeben, present day Sibiu

Sibiu

Sibiu is a city in Transylvania, Romania with a population of 154,548. Located some 282 km north-west of Bucharest, the city straddles the Cibin River, a tributary of the river Olt...

, Romania, was known as Siebenbürger Sachse.