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A pulse detonation combustor (PDC) includes a combustion tube, an inlet located on an upstream end of the combustion tube which receives a flow of a fuel/air mixture, an enhanced DDT region located within the tube downstream of the inlet, a nozzle disposed on a downstream end of the tube and a forti

A pulse detonation combustor (PDC) includes a combustion tube, an inlet located on an upstream end of the combustion tube which receives a flow of a fuel/air mixture, an enhanced DDT region located within the tube downstream of the inlet, a nozzle disposed on a downstream end of the tube and a fortified region disposed downstream of the enhanced DDT region and upstream of the nozzle. A combustion initiation system that provides multiple initiation locations at different axial stations along the length of the tube are positioned downstream of the inlet and upstream of the fortified region. The initiator system is operable to initiate combustion of a fuel-air mixture within the tube at a selected one of the initiation locations.

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1. A method of operating a pulse detonation combustor (PDC) having a combustion tube, an inlet disposed on an upstream end of the combustion tube, an enhanced deflagration-to-detonation (DDT) region located within the combustion tube downstream of the inlet, a nozzle disposed on a downstream end of

1. A method of operating a pulse detonation combustor (PDC) having a combustion tube, an inlet disposed on an upstream end of the combustion tube, an enhanced deflagration-to-detonation (DDT) region located within the combustion tube downstream of the inlet, a nozzle disposed on a downstream end of the combustion tube, a fortified region disposed downstream of the enhanced DDT region and upstream of the nozzle, and a combustion initiation system providing a plurality of initiation locations along an axial length of the combustion tube, the method comprising: providing a flow of a fuel/air mixture to the combustion tube via the inlet;activating the combustion initiation system at a selected initiation location of the plurality of initiation locations along the length of the combustion tube to ignite the fuel/air mixture within the combustion tube at the selected initiation location, in order to select a detonation region at which combustion of the fuel/air mixture transitions to a detonation, wherein the detonation region is the fortified region of the combustion tube;detecting a location of a transition to detonation of a previous combustion;adjusting the selected initiation location at which to activate the combustion initiation system based on the detected location of the transition to detonation of the previous combustion; and exhausting combustion products from the combustion tube through the nozzle. 2. The method of claim 1, wherein the combustion initiation system comprises a plurality of initiators, at least one which is disposed at each of the plurality of initiation locations, and activating the combustion initiation system comprises using the at least one initiator located at the selected initiation location. 3. The method of claim 2, wherein at least one of the plurality of initiators is disposed upstream of the enhanced DDT region and at least one of the plurality of initiators is disposed within the enhanced DDT region. 4. The method of claim 1 wherein the combustion initiation system comprises a first electrode disposed within the combustion tube and extending at least from a furthest upstream initiation location of the plurality of initiation locations to the a furthest downstream initiation location of the plurality of initiation locations, and a second electrode disposed adjacent to the combustion tube, and activating the combustion initiation system comprises charging the first and second electrodes to opposite electrical polarities and selectively charging at least one of the first and second electrodes only in the selected initiation location. 5. The method of claim 1, wherein detection of the location of the transition to detonation of the previous combustion comprises measuring a strain in the combustion tube at multiple locations along the length of the combustion tube. 6. The method of claim 1, further comprising: varying the selected initiation location based on at least one of a pressure of the fuel air mixture and a temperature of the fuel air mixture. 7. The method of claim 1, further comprising: varying the selected initiation location based on a commanded throttle setting for the PDC. 8. The method of claim 1, wherein no detonation of the fuel/air mixture occurs within the combustion tube. 9. The method of claim 1, further comprising: adjusting the selected initiation location at which to activate the combustion initiation system in order to compensate for a peak stress or thermal load. 10. The method of claim 9, wherein the peak stress or thermal load results in reduced effectiveness of the enhanced DDT region in accelerating combustion of the fuel/air mixture. 11. The method of claim 1, further comprising: flowing a cooling fluid through a cooling fluid path of a cooling system, wherein the cooling system is disposed along at least a portion of the length of the combustion tube that includes the fortified region, and the cooling fluid path is in contact with an outer wall of the combustion tube. 12. The method of claim 11, wherein the cooling fluid path has a smaller cross section at the fortified region compared to the a cross section of the fluid cooling path both upstream and downstream of the fortified region. 13. The method of claim 11, wherein a mass flow of cooling fluid passing through the cooling fluid path at the fortified region is greater compared to a mass flow of cooling fluid passing through the cooling fluid path both upstream and downstream of the fortified region. 14. The method of claim 11, wherein surface features are disposed within the cooling fluid path at the fortified region. 15. The method of claim 14, wherein the surface features are fins disposed upon the outer wall of the combustion tube. 16. The method of claim 14, wherein the surface features are ribs disposed upon the outer wall of the combustion tube.