LE-7A
LE-7, Nagoya City Science Museum, 2006
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| Country of origin | Japan |
|---|---|
| Designer | JAXA |
| Manufacturer | Mitsubishi Heavy Industries |
| Application | Booster |
| Status | Succeeded by LE-7A upgrade |
| Liquid-fuel engine | |
| Propellant | LOX / LH2 |
| Cycle | Staged combustion |
| Configuration | |
| Chamber | 1 |
| Nozzle ratio | 52:1 |
| Performance | |
| Thrust (vac.) | 1,078 kN (242,000 lbf) |
| Thrust (SL) | 843.5 kN (189,600 lbf) |
| Thrust-to-weight ratio | 64.13 |
| Chamber pressure | 12.7 MPa (1,840 psi) |
| Isp (vac.) | 446 seconds (4.37 km/s) |
| Isp (SL) | 349 seconds (3.42 km/s) |
| Dimensions | |
| Length | 3.4 m |
| Dry weight | 1,714 kg (3,779 lb) |
| Used in | |
| H-II first stage | |
The LE-7 and its succeeding upgrade model the LE-7A are staged combustion cycle LH2/LOX liquid rocket engines produced in Japan for the H-II series of launch vehicles. Design and production work was all done domestically in Japan, the first major (main/first-stage) liquid rocket engine with that claim, in a collaborative effort from the National Space Development Agency (NASDA), Aerospace Engineering Laboratory (NAL), Mitsubishi Heavy Industries, and Ishikawajima-Harima. NASDA and NAL have since been integrated into JAXA. However, a large part of the work was contracted to Mitsubishi, with Ishikawajima-Harima providing turbomachinery, and the engine is often referred to as the Mitsubishi LE-7(A).
The original LE-7 was designed to be a high efficiency, medium-sized motor with sufficient thrust for use on the H-II, and classified as expendable since the engine was non-recoverable after launch.
The fuel turbopump had an issue using the originally designed inducer (a propeller-like axial pump used to raise the inlet pressure of the propellant ahead of the main turbopumps to prevent cavitation) where the inducer would itself begin to cavitate and cause an imbalance resulting in excessive vibration. A comprehensive post-flight analysis of the unsuccessful 8th H-II launch, including a deep ocean retrieval of the wreckage, determined that fatigue due to this vibration was the cause of premature engine failure.
The LE-7A is an upgraded model from the LE-7 rocket engine. Basic design is unchanged from the original model. The 7A had additional engineering effort placed on cost cutting, reliability, and performance developments. The renovation was undertaken to mate it with the likewise improved H-IIA launch vehicle, with the common goal being a more reliable, more powerful and flexible, and more cost effective launch system.
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