Hydrogen Bottle
From Space Engineers Wiki
The Hydrogen bottle is an item used for storing and transporting hydrogen. It was added to the game in Update 01.105, along with other hydrogen related objects.
This item is primarily used for sypplying the player with hydrogen, which is needed for the jetpack to work. It should also be noted that more hydrogen is consumed by the jetpack in higher-gravity environments.
The bottle can be refilled in an Oxygen Generator, just like an Oxygen Bottle.