Abstract: Hypergolic liquid or gel fuel mixtures utilized in bipropellant propulsion systems are disclosed as replacements for fuels containing toxic mono-methylhydrazine. The fuel mixtures include one or more amine azides mixed with one or more tertiary diamine, tri-amine or tetra-amine compounds. The fuel mixtures include N,N,N?,N?-tetramethylethylenediamine (TMEDA) mixed with 2-N,N-dimethylaminoethylazide (DMAZ), TMEDA mixed with tris(2-azidoethyl)amine (TAEA), and TMEDA mixed with one or more cyclic amine azides. Each hypergolic fuel mixture provides a reduced ignition delay for combining with an oxidant in fuel propellant systems. The fuel mixtures have advantages in reduced ignition delay times compared to ignition delay times for each unmixed component, providing a synergistic effect which was not predictable from review of each component's composition.