---
title: "Jack Parsons"
chunk: 1/16
source: "https://en.wikipedia.org/wiki/Jack_Parsons"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T04:32:07.745794+00:00"
instance: "kb-cron"
---

John Whiteside Parsons (born Marvel Whiteside Parsons; October 2, 1914 – June 17, 1952) was an American rocket engineer, chemist, and Thelemite occultist. Parsons was one of the principal founders of both the Jet Propulsion Laboratory (JPL) and Aerojet. He invented the first rocket engine to use a castable, composite rocket propellant, and pioneered the advancement of both liquid-fuel and solid-fuel rockets.
Parsons was raised in Pasadena, California. He began amateur rocket experiments with school friend Edward Forman in 1928. Parsons was admitted to Stanford University but left before graduating due to financial hardship during the Great Depression. In 1934, Parsons, Forman, and Frank Malina formed the Caltech-affiliated Guggenheim Aeronautical Laboratory (GALCIT) Rocket Research Group, with support by GALCIT chairman Theodore von Kármán. The group worked on Jet-Assisted Take Off (JATO) for the U.S. military, and founded Aerojet in 1942 to develop and sell JATO technology during World War II. The GALCIT Rocket Research Group became JPL in 1943.
In 1939, Parsons converted to Thelema, a religious movement founded by English occultist Aleister Crowley. Parsons and his first wife, Helen Northrup, joined Crowley's Ordo Templi Orientis (O.T.O.); he became the California O.T.O. branch leader in 1942. Historians of Western esotericism cite him as a prominent figure in propagating Thelema in North America. Parsons was dismissed from JPL and Aerojet in 1944, due to his involvement with O.T.O. and his hazardous laboratory practices. In 1945, he and Helen divorced. In 1946, he married Marjorie Cameron. Shortly afterward, L. Ron Hubbard defrauded Parsons of his life savings.
Parsons worked as an explosives expert during the late 1940s, but his career in rocketry ended due to accusations of espionage and the increasing trend of McCarthyism. Parsons died at the age of 37 in a home laboratory explosion in 1952; his death was officially ruled an accident but many of his associates suspected suicide or murder. Although publicly unknown during his lifetime, Parsons is now recognized for his innovations in rocket engineering, advocacy of space exploration and human spaceflight, and as an important figure in the history of the U.S. space program. He has been the subject of several biographies and fictionalized portrayals.

== Biography ==