Recent Mars soft-landing studies show that a propulsion system is required to accomplish the terminal landing sequence. Relatively high thrust levels and throttling ratios are required and engine weight is extremely significant since it comprises nearly one-third of the propulsion system weight due to the relatively small total impulse which is required. To overcome potential problems with scaling conventional catalytic thrusters, a pilot-chamberinitiated, thermal decomposition reactor concept has been studied. The pilot chamber operates catalytically on 5% to 15% of the total flow. The remainder reacts thermally in the main chamber which is void of catalyst. The characteristics of such a chamber have been experimentally studied and it shows high potential for further development. Operation at design values of L* = 150 in and G = 0.1 lbm/in.-sec appears completely feasible if a suitable heat sink "flame holder" is utilized.