A humble ring that changed how we share rides to space

Moog Inc. and the U.S. Air Force Research Lab are celebrating the 25th anniversary of the Evolved Secondary Payload Adapter (ESPA) ring's Critical Design Review in 2001. This unassuming piece of hardware—essentially a structural ring with standardized attachment points—was developed to solve a simple but expensive problem: the wasted space beneath a rocket's primary satellite payload. By letting multiple smaller satellites hitch a ride as secondary payloads, ESPA dramatically cut launch costs and opened orbital access to a much wider range of missions.

For engineers and space startups, ESPA became a game-changing enabler. Its modular, flight-proven design allowed commercial satellite constellations, university experiments, and defense technology demos to reach orbit without needing their own dedicated, prohibitively expensive rockets. The platform's legacy lives on in evolved configurations like ESPA Heavy and ESPA Grande, which continue to support NASA, government, and commercial missions worldwide. The takeaway: sometimes the most impactful innovations aren't flashy rockets, but the simple, reliable adapters that make space travel more affordable and accessible for everyone.