ECAUSE of their relative simplicity, solid-propellant rockets came intouselongbeforeliquid-propellantrockets.Evenifthe initial uses of solid propellants in the form of blackpowder might have been in peaceful e reworks, history quickly mentioned them in connection with guns, e re arrows, and other types of armaments. This characteristic of being an “ old technology” and the connectionwith military devices probablypartially explains why, centuries later, thevisionariesofspacetraveltended to look to liquid systems, leavingthesolidrocketintheroleofanordnancedevice.Infacttheir strong orientation toward liquids was probably a consequence of a lack of vision of the future technology. And, in fact, during the e rst thousand years there was very limited progress in solid propellants, and this, of course, led to small hopes of achieving the high impulses of big rocket motors. The invention of composite propellants removed the impulse limitations in the middle of the 20th century. Ed Price 1 wrote that “ the history of solid rockets is very special for its spirit of people making things to happen.” We will see how the key people in the development of modern solid propellants had morethananyotherqualitythatofentrepreneurs.(Typicalexamples like the creation of Aerojet and the development of Thiokol will be describedlater.)Also,inmanyaspectsthepeopledealingwithsolids have often been inventors and self-made men, whereas the people involved in liquids were or considered themselves to be scientists and members of the academia. Of course, science always followed, butthischaracteristicofbeing asortofinvention,andsometimesthe characters of the inventors, might have contributed to some lower considerationforsolid-propellanttechnology,whichwassometimes considered a black art. Theinitialdevelopmentofcontemporarysolidpropellantsismore or less an American story, but the rest of the world followed, and some innovations in the technology came from outside the United States. Prehistory, inventions, inventors, science, technology, uses and applications, and development in the world should be covered inthispaper.Wehope thatthereaderwillexcuse theauthorforallof the imperfections and omissions: lack of information— mainly related to cone dentiality, either for security reasons or for proprietary reasons, extension of the task, limitation of space, loss of historical traces and archives, should be generally responsible. 2 Finally,it might be useful to remember a few points that are often forgotten by people not directly involved in solid-propellants technology and which justie es a high level of consideration for it. In a solid rocket