The Draper engineThe Draper engine

U.S. Propulsion Leader Ursa Major Announces Storable Liquid Rocket Engine for Hypersonics Defense

|Press Release

“Draper” is a 4,000-Pound-Thrust Hydrogen Peroxide and Kerosene Engine Inspired by the Character Bobbie Draper of “The Expanse."

DENVER - May 18, 2023 - Ursa Major, America's leading privately funded company that focuses solely on rocket propulsion, is excited to introduce Draper, a revolutionary new engine designed to defend against hypersonic weapons.

Draper is a storable, 4,000-pound-thrust closed catalyst cycle engine that uses storable hydrogen-peroxide/kerosene propellant, making it ideal for small hypersonic defense vehicles that need to launch on demand. Draper contains architectural and manufacturing heritage from the Hadley engine, of which more than 100 have been built.

“Draper combines the reliability and portability benefits of a solid rocket motor with the higher performance and maneuverability of a liquid engine. Those qualities allow Draper to better simulate hypersonic threats as a target vehicle,” said Joe Laurienti, founder and CEO of Ursa Major. “Draper will allow America to leap ahead in hypersonic defense.” 

Solid rocket motors have traditionally powered the vehicles used for testing missile defense systems, but they cannot change thrust in real-time to actively throttle and respond to changing conditions. With adversarial hypersonic weapons becoming increasingly complex and erratic, a liquid rocket engine such as Draper provides active throttle control and throttle range, giving it the maneuverability and flexibility needed for hypersonic defense.  

Advantages of a Closed-Cycle Hydrogen Peroxide Engine  

  • Engine cycle maximizes performance and draws on the testing heritage of Ursa Major’s Hadley engine. 

  • Can be stored at room temperature for years to support on-demand launch.  

  • High propellant density fits more capability into space-constrained hypersonic vehicles. 

  • Hydrogen peroxide is a “green” storable propellant, which improves safety and reduces risk of environmental harm compared to the toxicity of traditional hydrazine systems. 

  • Autoignition supports many restarts without a dedicated ignition system. 

  • Hydrogen peroxide can be used for attitude control systems (ACS) eliminating the need for additional ACS propellants. 

Like all Ursa Major engines, Draper’s components are largely 3D printed, which allows for rapid iteration during the development process and scaling of production to meet market demand. Ursa Major expects to fire the full Draper engine within 12 months. 

In addition to Draper and Hadley, Ursa Major recently hotfired the 50,000-pound thrust LOX/kerosene “Ripley” engine and is developing the 200,000-pound thrust LOX/Methane “Arroway” engine.  

Ursa Major’s facility houses engineering, manufacturing, and testing in one campus. The co-location shortens development cycles and lower costs, creating an efficient propulsion innovation and production ecosystem. 

About Ursa Major

Ursa Major is America's leading privately funded company focusing solely on rocket propulsion, bringing high-performance, staged combustion engines to market for space launch and hypersonic applications. Ursa Major customers, ranging from "New Space" startups to enterprise-level aerospace leaders and the U.S. government, get to flight faster, more reliably, and cost-effectively. The company employs the most sought-after engineers from top space programs and universities. Headquartered in Berthoud, Colorado, Ursa Major was named one of the best places to work by Built in Colorado three years in a row. For more information, visit For downloadable images and videos, visit

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