Final answer:
When space is an issue, fuel and oxygen must be separated by a barrier to prevent combustion. In space vehicles, liquid hydrogen and liquid oxygen are stored separately until launch.
Step-by-step explanation:
When space is an issue, fuel and oxygen must be separated by a barrier to prevent combustion and ensure safety. This is crucial because oxygen is required for combustion, while fuel, such as hydrogen, is highly flammable and can be a potent energy source.
For example, in space vehicles like the space shuttle, liquid hydrogen and liquid oxygen are stored in separate compartments until the shuttle is launched.