Furthermore the internal combustion engine is provided with an ignition device which extends into the combustion chamber for igniting the combustion gas.

并且还具有伸入到该燃烧室中的点火装置，用于点燃燃气。

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In this configuration, the HTP is passed over a catalyst pack to decompose it into steam and oxygen, but instead of igniting a fuel grain, this superhot gas is allowed simply to vent through the chamber nozzle.

BBC: Science & Environment