TOKYO — Development has begun on Japan’s next-generation small rocket, the three-stage, solid-fueled Epsilon, which is currently slated for its first outing in 2013. While the rocket’s cost and flexibility will be a significant improvement on its predecessor, the Epsilon’s development schedule is being split into two stages so that the rocket will only achieve its full potential in 2017, according to the program’s project manager.
The Epsilon is being developed as a lower-cost replacement for Japan’s M-5 solid-propellant rocket, which, while technologically advanced, was deemed too expensive to build and launch and retired in 2006 after seven outings, Yasuhiro Morita, Epsilon project manager at the Japan Aerospace Exploration Agency (JAXA), said April 4.
Designed to launch 1,200 kilograms into low Earth orbit, the 24-meter-tall Epsilon rocket will be capable of carrying only about two-thirds as much payload as the M-5 rocket it is replacing.
But at a projected 3.8 billion yen ($44.5 million) per vehicle, Epsilon will cost only about half as much per launch, Morita said.
To achieve this, the initial version of Epsilon will use an SRB-A solid strap-on booster from Japan’s H-2A mainstay medium launch vehicle as its first stage, and use improved versions of the third and fourth stages of the M-5 rocket for its second and third stages. The cost reduction for the initial version will be achieved by use of an improved, simpler production process for the SRB-A, Morita said.
In addition, software will automate Epsilon launch checkout procedures, reducing the necessary work force from the 100 people needed for the M-5 to five or six people working from laptop computers; the checkout period, meanwhile, will be reduced from 47 days for the M-5 to under a week for the Epsilon, Morita said. Further, by using a tiny boost-stage motor placed between the second and third stage motors, the Epsilon will have a vastly improved apogee insertion accuracy: plus or minus 20 kilometers, compared with around 100 kilometers for the M-5.
During Phase 2 of the Epsilon project, a more advanced version of the rocket will be developed for a 2017 debut that will take advantage of two further improvements; a new avionics system that will be built from off-the-shelf parts, and a new molding process for the booster casing. These measures should reduce the launch cost for subsequent flights to about 3 billion yen per launch, Morita said.
“The primary purpose of Phase 1 is to automate and simplify the launch checkout phase and the primary purpose of Phase 2 is to cheapen the launch cost further,” Morita said. The development budget for Phase 1 will be “around $200 million.”
The cost for Phase 2 has not been worked out fully, but should be “between $100 million and $150 million,” he said.
Epsilon’s primary role will be to provide a cheaper, more flexible alternative to the H-2A rocket to launch two new families of 400-500 kilogram-class satellites, said Keiichi Tabuchi, unit chief of the Space Development and Utilization Division of the Ministry of Education, Culture, Sports, Science and Technology, which currently has oversight of JAXA. One such family of spacecraft is the Advanced Satellite with New system Architecture for Observation (ASNARO) series satellites being developed by NEC Corp. as part of a project funded by the Ministry of Economy Trade and Industry. These satellites will be for Earth observation duties, he said April 5.
The other family is the series of Platform for Rapid Investigation and Test (SPRINT) spacecraft being developed by JAXA for space science missions, said Shujiro Sawai, manager of the Small Scientific Satellite Project at JAXA. Both ASNARO and SPRINT share the same basic frame that will allow different users to swap in different payloads, he said.
Epsilon’s first mission will be to launch the 370-kilogram SPRINT-A scientific satellite that will observe the atmosphere of Venus, Mars and Jupiter in extreme ultraviolet from Earth orbit, Sawai said April 5. The Epsilon also will use a microsatellite dispenser system that will further add to its utility, especially for dozens of university groups and other potential users developing experimental and other satellites, he said.
Beyond 2017, JAXA is hoping to develop an “Epsilon Phase 3” Morita said. If funding is approved at a later date, the nozzle and fuel composition of the SRB-A will be redeveloped to increase thrust while retaining the same propellant mass. Morita also envisages swapping in a new second and third stage configuration. This would involve using the old M-5’s second stage for the Epsilon’s second stage, and moving the second stage motor of the Phase 1 and 2 versions of the Epsilon to become the third stage engine of the Epsilon Phase 3 rocket.
“These efforts would raise the launch capacity to beyond that of the M-5,” Morita said.