propulsion unit

基本解释

The MMU was replaced with the SAFER backpack propulsion unit.
目前，载人机动装置已被更安全的背包式推进器所取代。
Causes for damage of main parts of Z---type marine propulsion unit are introduced in this pa- per. it also gives the making of plan. design principle and repair methods.
介绍船用Z型推进装置主要零备件的损坏原因以及在进行零备件国产化过程中的方案制定、设计原则和修理方法。
Once you are on the surface, the main unit for propulsion are your arms, so it is very important that your draw the right pattern underwater, and that is a hourglass pattern.
身体浮到水面后，最大的推进力量就来自手臂。因此正确的水下划水路线非常重要，也就是沙漏状划水。