['they', 'find', 'thruster', 'EmptyParameter', 'EmptyParameter']
['<PRP>', 'discover-84', "Synset('jet_engine.n.01')", 'EmptyParameter', 'EmptyParameter']
They find a chemically-fueled maneuvering thruster, powered by oxygen and liquid hydrogen.
<PRP> find a chemically-fueled maneuvering thruster, powered by Synset('substance.n.01') and Synset('melted.a.01') Synset('substance.n.01').