Unfortunately, the solid propellants—usually aluminum fuel and ammonium perchlorate oxidizer—burn fairly inefficiently, are toxic to the environment, and are difficult to fabricate and handle safely.
Unfortunately, the solid propellants—usually aluminum fuel and ammonium perchlorate oxidizer—burn fairly inefficiently, are toxic to the environment, and are difficult to fabricate and handle safely.
然而固体推进剂（通常是铝燃料和过氯酸铵氧化剂）燃烧效率颇低、对环境有害，而且很难安全地制造和操作。