| A | B |
|---|
| X-43 A | hydrogen scramjet crashed last spring |
| X-43 C | Jet fuel propelled, scheduled to fly in ' 06 |
| X-43 B | Will be used to begin proving multicycle engine technology |
| X-43 D/Large Scale Demonstrator | Will push the limits of Scramjet to speeds of Mach 10-15 |
| Piston Engine | Automotive type engine still used to power private aircraft, speeds from Mach 0~0.6. |
| Turboprop | A jet like engine, speeds up from Mach 0~0.7. |
| Turbo Jet | A pure jet engine,all air flows through engine core, speeds from Mach 0~3+. |
| Low Bypass Ratio Turbojet | powers fighter type aircraft F-15/16, from Mach 0~2.5. |
| High Bypass Ratio Turbofans | Used in commercial transport at speeds Mach 0 to 0.9. |
| Ramjet | No rotating machinery is used.Speed up to Mach 6. |
| Scram Jet | an improvement on the ramjet technology, Mach 5~15 |
| Rocket Engine | Speeds from Mach 0 to near the exit velocity of the nozzle. |
| Pegasus | Used to launch orbital payloads and the X-43A&C vehicles. |
| Combined cycle | Speeds of Mach 2~6. |
| Cryogenic insulation | insulation around the hydrogen&oxygen that keeps these fuels cold enough to remain liquid. |
| TPS | Thermal Protection System-protects the vehicle from extreme environments. |
| Technical Readiness Level-TRL | scale from 1-9 that ranks the maturity of technology. |
| Health Monitoring | designed to monitor the "health" of the craft like a computer in a vehicle. |
| Kistler Rocket | a conventional two stage orbit rocket, which is completely reusable, landing with parachute/air bag system. |
| Demonstration of Autonomous Rendezvous Technology(Dart) | an orbiting computer controlled maneuvering spacecraft used to stimulate docking with cooperative vehicles. |
| High Speed Air Breathing Vehicle(ABV) | a vehicle, which travels at high speed using air as part of its fuel. |
| Fly by Light Engine | No projected availability date this concept uses a laser to disassociate gas to power a vehicle. |
