Sierra Space, based in Colorado, has achieved a milestone by successfully completing a test campaign of its new liquid oxygen and liquid hydrogen-fuelled upper stage engine at a US Air Force Base in California. The test, conducted in collaboration with the Air Force Research Laboratory (AFRL), aimed at advancing upper stage engine technology for National Security Space Launch (NSSL) missions. The engine, named VR35K-A, utilizes a fuel-rich staged combustion cycle and Sierra Space's patented VORTEX combustion chamber technology to generate 35,000 lbf of thrust. This achievement follows a previous test campaign in Wisconsin in 2024, showcasing stable and efficient thrust operation. Dan Polis, Vice-President of Engineering Solutions and Propulsion Systems at Sierra Space, highlighted the engine's high performance, reduced complexity, and significant cost savings, enabling customers to transport up to 30% more payload mass to orbit. The article emphasizes the long-standing use of liquid hydrogen in space missions, dating back to NASA's adoption in the 1960s. Despite past challenges like liquid hydrogen leaks affecting launches, the article underscores the critical role hydrogen plays in achieving high performance in rocket propulsion. The space industry's focus on hydrogen's potential is mirrored in the training modules offered by H2 View's Class of H2, addressing the skills gap in the hydrogen sector. This comprehensive training covers a range of topics from basic hydrogen fundamentals to different production methods like green hydrogen and ammonia. The article concludes by highlighting the importance of hydrogen in space exploration, despite challenges, as it remains a key component for efficient rocket propulsion and future space missions.