The Lambda rocket family was a series of Japanese carrier rockets developed by the Institute of Space and Aeronautical Science (ISAS) at the University of Tokyo, in collaboration with Prince Motor Company, which later merged with Nissan. These rockets were primarily designed for scientific missions, including atmospheric research and satellite launches.
Every stage—from the early Lambda 2 sounding rockets to the orbital Lambda 4S—used solid propellant, which made the rockets simpler, more reliable, and easier to store compared with liquid-fuel rockets. The solid-fuel design was ideal for small payloads like the Ōsumi satellite, but it limited flexibility for very large payloads or complex missions.
The Lambda series laid the foundation for Japan’s future space endeavors. The success of the Lambda 4S and the Ōsumi satellite demonstrated Japan’s capability in space technology and paved the way for subsequent missions, including the development of the Mu and H-II rocket families.
Lambda 4S: Japan's First Orbital Launch Vehicle
The Lambda 4S, first launched September 26, 1966, was a significant milestone in Japan’s space program. On February 11, 1970, the Lambda 4S successfully launched the Ōsumi satellite, making Japan the fourth country to independently place a satellite into orbit. Lambda 4S launched five times and had four failures.
- Payload Capacity: Approximately 26 kg to Low Earth Orbit (LEO)
Launch Site: Kagoshima Space Center, Japan
Key Variants
Lambda 2: A three-stage sounding rocket used for ionospheric studies.
Lambda 3: An enhanced version of Lambda 2, capable of reaching higher altitudes for more extensive atmospheric research.
Lambda 3H: A variant with improved performance for high-altitude missions.
Lambda 4S: A four-stage rocket developed to place satellites into orbit. It was the first Japanese rocket to achieve this feat.
Lambda 4SC: A derivative of Lambda 4S, used for testing technologies for future launch vehicles.
Lambda 4T: A variant with modifications for specific mission requirements.
The Ōsumi Satellite
The Ōsumi satellite, launched aboard the Lambda 4S on February 11, 1970, was Japan’s first artificial satellite. Although its operational life ended within hours due to power loss, Ōsumi remained in orbit for over 33 years before re-entering the atmosphere on August 2, 2003.
- Mission: To gather data on the ionosphere and test satellite technologies.
Orbit: Achieved an elliptical orbit with an apogee of approximately 5,150 km and a perigee of 335 km.
Technical Specifications of Lambda 4S
- Height: 16.5 meters
- Diameter: 0.74 meters
- Mass: 9,400 kg
- Stages: 4
- Stage 1: L735
- Stage 2: L735(1/3)
- Stage 3: L500
- Stage 4: L480S
- Boosters: 2 × SB-310 solid-fuel boosters
- Propellant: All stages used solid propellant
