Ram-jet propulsion and Rocket propulsion

Rocket propulsion and ram-jet propulsion are semantically related in propulsion by jet discharge topic. In some cases you can use "Rocket propulsion" instead a noun phrase "Ram-jet propulsion".

Rocket propulsion noun - Reaction propulsion using stored oxygen for combustion; used where there is insufficient atmospheric oxygen.

Ram-jet propulsion and rocket propulsion are semantically related in propulsion by jet discharge topic. You can use "Ram-jet propulsion" instead a noun phrase "Rocket propulsion".