Mars Global Surveyor, 2001 Mars Odyssey, and Mars Reconnaissance Orbiter, and at least one Venus mission, Magellan. Aerocapture is a much more aggressive manoeuver, converting an incoming hyperbolic orbit to an elliptical orbit in one pass. This requires a heat shield and much trickier navigation, because it must be completed in one pass through the atmosphere, and unlike aerobraking no preview of the atmosphere is possible. If the intent is to remain in orbit, then at least one more propulsive maneuver is required after aerocapture—otherwise the low point of the resulting orbit will remain in the atmosphere, resulting in eventual re-entry. Aerocapture has not yet been tried on a planetary mission, but the re-entry skip by Zond 6 and Zond 7 upon lunar return were aerocapture maneuvers, because they turned a hyperbolic orbit into an elliptical orbit. On these missions, because there was no attempt to raise the perigee after the aerocapture, the resulting orbit still intersected the atmosphere, and re-entry occurred at the next perigee. A ballute is an inflatable drag device. Parachutes can land a probe on a planet or moon with an atmosphere, usually after the atmosphere has scrubbed off most of the velocity, using a heat shield. Airbags can soften the final landing. Lithobraking, or stopping by impacting the surface, is usually done by accident. However, it may be done deliberately with the probe expected to survive (see, for example, Deep Impact (spacecraft)), in which case very sturdy probes are required. In fiction In science fiction, space ships use various means to travel, some of them scientifically plausible (like solar sails or ramjets), others, mostly or entirely fictitious (like anti-gravity, warp drive, spindizzy or hyperspace travel). See also References External links NASA Breakthrough Propulsion Physics project Different Rockets Earth-to-Orbit Transportation Bibliography Spaceflight Propulsion – a detailed survey by Greg Goebel, in the public domain Johns Hopkins University, Chemical Propulsion Information Analysis Center Tool for Liquid Rocket Engine Thermodynamic Analysis Smithsonian National Air and Space Museum's How Things Fly website Fullerton, Richard K. "Advanced EVA Roadmaps and Requirements." Proceedings of the 31st International Conference on Environmental Systems. 2001. Atomic Rocket – Engines: A site listing and detailing real, theoretical and fantasy space engines. Spacecraft propulsion Spacecraft components Spaceflight technology NASA programs Glenn Research Center Discovery and exploration of the Solar System