Complex sentence: These alloy fins on the launch lower when launching as to not interfere with the train during launch, then to slow the train in case of a short shot, they raise section by section after the train has passed them.
Split into simpler sentences: These alloy fins on the launch lower when launching so as to not interfere with the train during launch. To slow the train in case of a short shot, they raise section by section after the train has passed them.