Even though the theoretical concepts have been around for nearly 90 years, #RDEs are still in their early days. βWe really donβt know what an optimized RDE even would look like yet,β #NASAβs Perkins says. βI can count the people with significant expertise in this area on 10 fingers.β Nevertheless, rising excitement is spurring #RDE startup launches. https://www.scientificamerican.com/article/ring-of-fire-rocket-engines-put-a-new-spin-on-spaceflight/