The Draper engineThe Draper engine

Meet Draper, Ursa Major’s newest engine


Introducing Draper, a storable liquid engine in development under an Air Force Research Laboratory contract.

Ursa Major is excited to introduce Draper, a revolutionary new engine designed for hypersonics defense, in-space propulsion, and rapid launch.

Draper is a 4,000-pound-thrust closed catalyst cycle engine that uses storable hydrogen-peroxide/kerosene propellant, making it ideal for vehicles that need to launch on demand. Draper contains architectural and manufacturing heritage from the Hadley engine, but unlike Hadley, it doesn’t require cryogenic conditions for its fuel.

Draper bears the storable characteristics of a solid motor with the higher performance and maneuverability of a liquid engine. Those qualities allow it to better simulate hypersonic threats as a target vehicle, which is a critical gap in America’s hypersonics capabilities today.

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, liquid rocket engines provide active throttle control and throttle range, giving them 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 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.

The Air Force Research Laboratory (AFRL) is funding Draper’s development. Under the newly announced contract, Ursa Major will build and test a prototype of Draper, build a fourth, Draper-specific test stand at its Berthoud, Colorado, headquarters, and further develop the 200,000-pound thrust Arroway engine. Arroway debuted in 2022 and is one of the few commercially available engines that, when clustered together, can displace the Russian-made RD-180 and RD-181, which are no longer available to U.S. launch companies.

Like Ursa Major’s other engine programs, Draper is named after a female character in science fiction: Bobbie Draper from the SYFY Network/Amazon series "The Expanse."

Roberta “Bobbie” Draper in “The Expanse.” 
Roberta “Bobbie” Draper in “The Expanse.” Credit: RAFY/SYFY

Ursa Major Staff - Launch-Ready Propulsion for every sector of aerospace

Seeing aerospace advancement as a technological imperative, we’re accelerating the industry as the leading source of world-class propulsion systems.


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