Sentence:  The two main problems of <WSD>metachemistry</WSD> as related to the field of propellants are the stabilization of metastable states in macroscopic bulk and the exploitation of the freely available excited particles in the upper atmosphere for the generation of HAL discharges especially blue starters, blue jets and red sprites is calculated. 
Meaning of the word marked with <WSD> tags:  The study of substances that can release large amounts of energy relative to their mass, such as molecules in metastable excited states.