By employing the gaseous oxygen as oxidizer and gaseous hydrogen as fuel, hot-firing tests were performed for aerospike nozzle and dual-bell nozzle test engines with altitude compensating features.
采用气氧作氧化剂、气氢作燃料，对具有高度补偿特性的塞式喷管和双钟型喷管进行了点火热试。
2
Whether in an individual coal pit, oil, or gas field, a nation or the planet as a whole, fossil fuel reserves and production tend to follow a bell curve over time.