Symptoms of Age-Related Macular Degeneration (AMD) An early symptom of wet AMD is that straight lines appear wavy. An Amsler Grid chart can help spot this early distortion of vision. You may also notice a small blind spot, resulting in a loss of central vision.
Traveling at approximately 29,000 km/h (18,000 mph) the shuttle orbits Earth every 90 minutes. By using current technology and a spacecraft powered by chemical rocket engines, a trip to Mars could take between six to nine months.
Space Shuttle Main Engines The three Space Shuttle Main Engines, in conjunction with the Solid Rocket Boosters, provide the thrust to lift the Orbiter off the ground for the initial ascent. The main engines continue to operate for 8.5 minutes after launch, the duration of the Shuttle's powered flight.