Firefly Aerospace Takes a Giant Leap Forward with Successful Hot Fire Test of Miranda Rocket Engine

The test marks a significant milestone for Firefly Aerospace as they work towards their mid-2025 launch target for the new rocket.

Firefly Aerospace, a private aerospace company, made headlines this week with the announcement of their first successful hot fire test of the Miranda rocket engine. This engine will serve as the first stage for Northrop Grumman’s Antares 330 and Firefly Aerospace’s own Medium Lift Vehicle (MLV). The test signifies a major step forward for the company as they strive to meet their ambitious launch target in the coming years.

The Powerhouse Behind the MLV and Antares 330

The MLV and Antares 330 rockets will be powered by seven Miranda engines on their first stage, boasting an impressive 1.6 million pounds of thrust. The Antares 330 will have the capability to deliver up to 10,000 kg of payload to the International Space Station. Meanwhile, the MLV, equipped with the Miranda vacuum engine, will have a payload capacity of up to 16,000 kg to low Earth orbit. Initially, the Antares 330 will use a Castor 30XL solid-fueled rocket motor for its first launches before transitioning to the Miranda vacuum engine.

The Green Flash and Cutting-Edge Technology

The Miranda engine utilizes liquid oxygen, rocket propellant-1 (RP-1), and triethylaluminium-triethylborane to ignite the engine. This unique combination produces a distinctive green flash during engine ignition, as captured in the photo released by Firefly Aerospace. The company’s vertically integrated approach and rapid development culture have allowed them to quickly scale up the flight-proven engine architecture from their small launch vehicle, Alpha, to the more powerful MLV.

CEO’s Perspective and Future Plans

Bill Weber, CEO of Firefly Aerospace, expressed his excitement about the progress made with the Miranda engines, stating that they have set a new standard in the industry. Weber highlighted the company’s achievement in designing, building, and testing the engines in-house within just over a year. He also emphasized Firefly’s rapid, iterative culture and vertically integrated approach as key factors in their success. The next step for Firefly Aerospace will be a full-duration hot-fire test of the Miranda engine, which is expected to last approximately 206 seconds.

Looking ahead, Firefly Aerospace has set their sights on a December launch for Flight 004 of their Alpha rocket. This mission will carry a Lockheed Martin electronically steerable antenna payload demonstrator to low Earth orbit, showcasing the versatility and capabilities of their rockets.


Firefly Aerospace’s successful hot fire test of the Miranda rocket engine marks a significant achievement for the company as they work towards their mid-2025 launch target. The powerful Miranda engine, with its unique propellant combination and impressive thrust capabilities, will propel the MLV and Antares 330 rockets into space. With a strong focus on rapid development and vertical integration, Firefly Aerospace is poised to make a significant impact in the commercial space industry. As they continue to push boundaries and expand their capabilities, the future looks bright for this innovative aerospace company.






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