Abstract: The present space experiments have been conducted aboard the China recoverable satellite SJ-8 to investigate the smoldering characteristics of flexible polyurethane foam with a forced oxidizer flow velocity of 3.1 mm/s. They are unique in that a combination of mixed flow opposed and forward smolder was investigated at specific ambient pressure. The results show that in the 21% O2 case, the microgravity opposed flow smolder reaction is not strong enough to progress through the foam sample and eventually extinguishes, whereas the forward smolder propagates along the entire sample length. In the 35% O2 case, both two types of smolder reaction exhibit a self-sustained propagation. Particular important is the discovery that, there is a transition from smoldering to flaming near the sample end in the opposed smolder, and it seems to be caused by the strong acceleration of smoldering reaction. This transition serves to initiate a vigorous, forward-propagating, oxidation reaction in the char left behind by the smolder reaction. The secondary char oxidation reaction propagates through the sample and consumes most of the remaining char. The study provides additional information of %practical interest in fire safety for manned spacecraft. At the same time, the data obtained in microgravity experiments can be used for the verification and development of smolder theory.