Sea Dragon

The Sea Dragon, a massive 1960s rocket concept, was projected to deliver 550 metric tons to low Earth orbit with estimated launch costs between $59 and $600 per kilogram in 1963 dollars (equivalent to $500–$5,060 per kilogram today).

These cost estimates were validated by TRW Inc., a major aerospace contractor known for its work on Apollo and missile propulsion systems.

TRW’s analysis confirmed the feasibility of the Sea Dragon’s design, but the project was never built due to shifting space exploration priorities and funding constraints.