Method of operating a closed-cycle hydrogen engine with an oxidizer gas composed of oxygen and an inert gas uninvolved in the combustion, cycling of a gas mixture and removal of a water combustion product by condensation, characterized in that - the oxygen required for the combustion is obtained directly from the air surrounding the closed-cycle hydrogen engine, - by alternately operating each of at least two reactors (4, 5) filled with oxygen storage material in two phases, wherein in each case - in a first phase the reactors (4, 5) are filled with air, such that the oxygen present in the air is intercalated into the oxygen storage material, - in a second phase the reactors that have been enriched with the oxygen in the oxygen storage material are purged with the gas mixture discharged as a result of the combustion, such that the gas mixture is enriched with the oxygen intercalated in the oxygen storage material, and - after the second phase the resultant gas mixture is fed to the closed cycle, wherein subsequently the water is removed by condensation, such that the gas mixture is fed to the closed-cycle hydrogen engine as oxidizer gas comprising the oxygen and the inert gas. - the oxygen required for the combustion is obtained directly from the air surrounding the closed-cycle hydrogen engine, - by alternately operating each of at least two reactors (4, 5) filled with oxygen storage material in two phases, wherein in each case - in a first phase the reactors (4, 5) are filled with air, such that the oxygen present in the air is intercalated into the oxygen storage material, - in a second phase the reactors that have been enriched with the oxygen in the oxygen storage material are purged with the gas mixture discharged as a result of the combustion, such that the gas mixture is enriched with the oxygen intercalated in the oxygen storage material, and - after the second phase the resultant gas mixture is fed to the closed cycle, wherein subsequently the water is removed by condensation, such that the gas mixture is fed to the closed-cycle hydrogen engine as oxidizer gas comprising the oxygen and the inert gas. - by alternately operating each of at least two reactors (4, 5) filled with oxygen storage material in two phases, wherein in each case - in a first phase the reactors (4, 5) are filled with air, such that the oxygen present in the air is intercalated into the oxygen storage material, - in a second phase the reactors that have been enriched with the oxygen in the oxygen storage material are purged with the gas mixture discharged as a result of the combustion, such that the gas mixture is enriched with the oxygen intercalated in the oxygen storage material, and - after the second phase the resultant gas mixture is fed to the closed cycle, wherein subsequently the water is removed by condensation, such that the gas mixture is fed to the closed-cycle hydrogen engine as oxidizer gas comprising the oxygen and the inert gas. - in a first phase the reactors (4, 5) are filled with air, such that the oxygen present in the air is intercalated into the oxygen storage material, - in a second phase the reactors that have been enriched with the oxygen in the oxygen storage material are purged with the gas mixture discharged as a result of the combustion, such that the gas mixture is enriched with the oxygen intercalated in the oxygen storage material, and - after the second phase the resultant gas mixture is fed to the closed cycle, wherein subsequently the water is removed by condensation, such that the gas mixture is fed to the closed-cycle hydrogen engine as oxidizer gas comprising the oxygen and the inert gas.