After phasing out the M-5 (or M-V) launch vehicle in 2006, the Japan Aerospace Exploration Agency (JAXA) began development of a smaller solid propellant launch vehicle named “Epsilon” that it hoped would cost less to fly than M-5 had cost. Epsilon would continue the long-running tradition of smaller, lower cost “Mu” series orbital launchers that the Institute of Space and Astronautical Sciences (ISAS) had managed. Formerly independant ISAS became the Space Science Research Disvision of JAXA on October 1,2003.
Epsilon will use three solid motors and an optional “Compact Liquid Propulsion System” (CLPS) fourth stage. The first stage will be a modified SRB-A motor, weighing 74.4 tonnes and similar to the 230 tonne thrust monolithic boosters used by JAXA’s H-2A and H-2B launch vehicles.
The second stage will be an 11.6 tonne M-34c motor, a modified version of the M-5 rocket’s third stage that uses an extendible nozzle. A small KM-V-2b solid motor, derived from the M-5 fourth stage motor and weighing 3 tonnes will serve as the third stage. The three motors will burn for 120, 104.7 and 91.1 seconds, respectfully.
Also read:
–Rocket Lab Electron – Space Launch Report
–Atlas 5 – Space Launch Report
A 2.5 meter diameter payload fairing will enclose the payload and the third and fourth (CLPS) stages (when used). CLPS will provide orbit trimming and raising manuevers on some missions. With CLPS, Epsilon will be able to lift 700 kg to a 500 km x 30 deg orbit, or 450 km to a 500 km sun synchronous orbit. Without CLPS, Epsilon will be able to boost 1.2 tonnes into a 250 x 500 km x 30 deg orbit.
Epsilon is designed to simplify launch check out procedures. The rocket will perform its own self-tests using its on-board computer, which will be able to be monitored and controlled via. standard network connections from anywhere, making the launch control system independant of launch site.
Use of the monolithic SRB-A first stage motor eliminates the need to stack motor segments, as was required for the M-5 first stage. Epsilon will weigh only 91 tonnes at liftoff, compared to 140 tonnes for M-5. It will also be less capable, but smaller payloads should mean smaller budgets.
Epsilon was meant to cost one-third as much as M-5. The 2006 goal was to cut costs from $60 million to $20 million per flight.
Vehicle Configurations
| LEO Payload (metric tons) [1] 250 x 500km x 30 deg [2] 500 km x 30 deg [3] 500 km x 98.6 deg | Earth Escape Payload (metric tons) | Configuration | LIftoff Height (meters) | Liftoff Mass (metric tons) | |
| Epsilon (3-stg) | 1.20 t [1] | SRB-A + M-34c + KM-V2b + PLF | 24 m | 91 t | |
| Epsilon (4-stg) | 0.70 t [2] 0.45 t [3] | SRB-A + M-34c + KM-V2b + CLPS + PLF | 24 m | 91 t |
Vehicle Components
| Stg 1 (SRB-A) | Stg 2 (M-34c) | Stg 3 (KM-V2b) | Stg 4 Compact Liquid Propulsion System (CLPS) | Payload Fairing | |
| Diameter (m) | 2.5 m | 2.2 m | m | m | 2.5 m |
| Length (m) | 15.1 m | 3.6 m | m | m | m |
| Propellant Mass (tonnes) | 66 t | 10.8 t | 2.5 t | 0.1 t | |
| Empty Mass (tonnes) | 8.7 t | 0.8 t | 0.5 t | 0.2 t | |
| Total Mass (tonnes) | 74.7 t | 11.6 t | 3.0 t | 0.3 t | t |
| Engine | SRB-A | M-34c | KM-V2b | ||
| Engine Mfgr | Nissan | ||||
| Fuel | Solid | Solid | Solid | Liquid | |
| Oxidizer | |||||
| Thrust (SL tons) | |||||
| Thrust (Vac tons) | 161.12 t | 38.46 t | 8.29 t | t | |
| ISP (SL sec) | s | ||||
| ISP (Vac sec) | 283.6 s | 299.9 s | 301.7 s | 202 s | |
| Burn Time (sec) | 120 s | 104.7 s | 91.1 s | s | |
| No. Engines | 1 | 1 | 1 | 1 |
