The combustion needs some time and enough heat to be complete, at least 99 or 99.9 %. The high temperature should be given before the combustion of N2O4 and hydrazin is started and should be hold some time after the end of combusting the hyergolics.

So you need at hot hydrogen and oxygen flame with a long and hot exhaust pipe. When the combustion chamber and exhaust pipe is well preheated, injection of the hypergolics is started. After all the hydrazine is burnt, let the hydrogen and oxygen alone burn for some additional minutes.

But you need a water cooled chamber and exhaust pipe to resist the high temperatures. Too much water cooling is bad, the hot gases should stay hot for enough time.

So this method is applicable for a waste combustion plant on ground but not for a space capsule. But making combustion complete enough for a rocket engine is hard as shown above. Using a longer nozzle does not help at engine start and stop.

The combustion needs some time and enough heat to be complete, at least 99 or 99.9 %. The high temperature should be given before the combustion of N2O4 and hydrazin is started and should be hold some time after the end of combusting the hyergolics. A turbulent flow and a high pressure may enhance a complete combustion.

So you need at hot hydrogen and oxygen flame with a long and hot exhaust pipe. When the combustion chamber and exhaust pipe is well preheated, injection of the hypergolics is started. After all the hydrazine is burnt, let the hydrogen and oxygen alone burn for some additional minutes.

But you need a water cooled chamber and exhaust pipe to resist the high temperatures. Too much water cooling is bad, the hot gases should stay hot for enough time.

So this method is applicable for a waste combustion plant on ground but not for a space capsule. But making combustion complete enough for a rocket engine is hard as shown above. Using a longer nozzle does not help at engine start and stop.

The combustion needs some time and enough heat to be complete, at least 99 or 99.9 %. The high temperature should be given before the combustion of N2O4 and hydrazin is started and should be hold some time after the end of combusting the hyergolics.

So you need at hot hydrogen and oxygen flame with a long and hot exhaust pipe. When the combustion chamber and exhaust pipe is well preheated, injection of the hypergolics is started. After all the hydrazine is burnt, let the hydrogen and oxygen alone burn for some additional minutes.

But you need a water cooled chamber and exhaust pipe to resist the high temperatures. Too much water cooling is bad, the hot gases should stay hot for enough time.

The combustion needs some time and enough heat to be complete, at least 99 or 99.9 %. The high temperature should be given before the combustion of N2O4 and hydrazin is started and should be hold some time after the end of combusting the hyergolics.

So you need at hot hydrogen and oxygen flame with a long and hot exhaust pipe. When the combustion chamber and exhaust pipe is well preheated, injection of the hypergolics is started. After all the hydrazine is burnt, let the hydrogen and oxygen alone burn for some additional minutes.

But you need a water cooled chamber and exhaust pipe to resist the high temperatures. Too much water cooling is bad, the hot gases should stay hot for enough time.

So this method is applicable for a waste combustion plant on ground but not for a space capsule. But making combustion complete enough for a rocket engine is hard as shown above. Using a longer nozzle does not help at engine start and stop.