"A scramjet is a type of jet engine designed to operate at the speeds of rockets. Its main difference from a rocket is that it collects air from the atmosphere

"A scramjet is a type of jet engine designed to operate at the speeds of rockets. Its main difference from a rocket is that it collects air from the atmosphere to burn its fuel rather than carrying an oxidizing substance on board. More conventional jets (turbojets, turbofans, and ramjets) share this characteristic but are unsuitable for the high speeds at which scramjets can operate." http://en.wikipedia.org/wiki/Scramjet#Simple_description http://en.wikipedia.org/wiki/Scramjet#Simple_description So there is a difference between a scramjet and a rocket, beyond the speed that it travels.