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ramjet vs. scramjet

[ram-jet] / ˈræmˌdʒɛt /

noun

  1. a jet engine operated by the injection of fuel into a stream of air compressed by the forward speed of the aircraft.

[skram-jet] / ˈskræmˌdʒɛt /

noun

Aeronautics.
  1. a ramjet engine in which the flow through the combustor itself is supersonic.