Ursa Major eyes ‘Iron Dome’ applications for its mid-size rocket engine 

WASHINGTON — Rocket propulsion startup Ursa Major is accelerating development and testing of its Draper liquid rocket engine in collaboration with U.S. defense agencies and military contractors. The goal: to position the engine for potential use in next-generation missiles that would be part of the Trump administration’s Iron Dome missile-defense initiative.

Ursa Major last year completed ground tests of the Draper engine, developed with U.S. Air Force funding. These hot-fire tests took place at the company’s facilities in Berthoud, Colorado. Now, the company is planning a flight-testing campaign to further mature the design and explore military applications as well as commercial uses in space tugs and in-space transportation. 

“We believe Draper fills a gap that the United States has in its armaments and targets,” said Christopher Spagnoletti, chief product officer at Ursa Major. 

Propulsion challenges

The Pentagon’s push for a new missile defense shield highlights the need for better propulsion technology as the Iron Dome calls for high-performance interceptor missiles that can operate from the ground or from space, Spagnoletti noted.

Many current propulsion systems struggle to meet the size and weight requirements of tactical missiles while maintaining necessary performance levels, he said. Draper was designed to offer a liquid-propulsion alternative that provides more flexibility compared to traditional solid rocket motors and air-breathing scramjets.

“Draper has the form factor of a solid rocket motor,” Spagnoletti told SpaceNews. 

The engine’s non-cryogenic kerosene peroxide fuel combination would offer a simplified storage solution compared to engines using liquid oxygen. Because these propellants remain liquid at room temperature, he explained, they eliminate the need for complex cooling systems, allowing for long-term storage without special equipment and enabling immediate use when needed. 

Missile defense program

The Pentagon’s Iron Dome initiative proposes the use of “proliferated space-based interceptors capable of boost-phase intercept.” This means a large number of these weapons would be deployed in orbit around Earth to intercept and destroy incoming missiles during their boost phase, or the initial stage of a missile’s flight when its engines are still burning. 

Spagnoletti said the 4,000-pound-thrust Draper engine would be suitable for space-based interceptors as it was designed for both atmospheric and in-space propulsion.

Today’s missile defense systems primarily rely on solid rocket motors for storage efficiency and rapid deployment. Hypersonic weapons often utilize scramjets, which take in atmospheric oxygen as an oxidizer. Meanwhile, Draper is “agnostic to the environment,” he added.

Development and scaling

A 2023 Congressional Budget Office report highlighted the propulsion challenges in U.S. hypersonic missile development, noting that sustaining engine performance throughout flight is a significant hurdle. The report compared the challenge to “keeping a match lit in a hurricane.” 

Spagnoletti said Ursa Major is working with multiple defense agencies. Its main partner is the Air Force Research Laboratory which co-funded the development of Draper. The company is now also working with the Army’s Space and Missile Defense Command (SMDC), and the Missile Defense Agency (MDA), and is in discussions with major defense contractors although Ursa Major is not yet disclosing specific partnerships.

A potential application for Draper is hypersonic glide vehicles, which can maneuver mid-flight to hit moving targets. This class of weapons requires propulsion systems that can handle extreme conditions while providing sustained thrust, said Spagnoletti. “We’ve spent a lot of time with SMDC and MDA, focusing on very specific targets and hypersonic targets.” 

If flight tests are successful, the next challenge for Ursa Major will be scaling production, which requires government support, he said. While startups have emerged to meet the Pentagon’s demand for new propulsion technologies, many struggle to scale manufacturing capabilities.

Spagnoletti said the Iron Dome executive order could reshape priorities in the defense industrial base. “There’s been a lot of increased activity, and we expect this to continue,” he said. Defense agencies are working to better understand the tools at their disposal and to help transition promising technologies from the development phase to full-scale production.

“That’s really the dividing line between a ‘great idea’ and the ability to scale these complex machines,” he said.

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