Starhopper was a low-altitude prototype of the Starship system that looked more like a flying tank than an aerodynamic rocket. SpaceX did two "static fire" tests of the system at its facility in Boca Chica, Texas, to evaluate the performance of the engine in 2019, and then followed that up with four short test flights that same year. The Starship's first 1-foot (0.3 meter) tethered hop lasted 3 seconds. "Starhopper just lifted off & hit tether limits!" Musk said April 6, 2019, tweeting a dramatic fiery video of the first static fire test. The stubby vehicle made four test flights in total: two on a tether for safety reasons and two fully unleashed. On the first free flight, on July 25, 2019, the prototype soared to an expected altitude of 65 feet (20 m). Its last flight before retiring on Aug. 27, 2019, was expected to go as high as 500 feet (150 m), in line with a limit imposed by the U.S. Federal Aviation Administration (FAA). Two hops before flying high Starship's program tested several ground prototypes before attempting flight. The list of major prototypes in 2019 to 2020 included MK1 (destroyed during a tank pressure test), MK2 (abandoned for a newer design), MK3/SN1 (destroyed during a pressurization test), SN2 (pressure tested successfully), SN3 (destroyed during a test of its pressure tank) and SN4 (destroyed during a static fire test, following several successful tests). Starship's SN5 and SN6 prototypes conducted low-altitude test hops. SN5 reached an altitude of about 500 feet on Aug. 4, 2020, and moved sideways in the sky to reach its landing area. SN6 also made a 500-foot jaunt on Sept. 3, 2020. "Turns out, you can make anything fly haha," Musk tweeted about the SN6 flight, with a video showing a tank-like structure wobbling through the air. SpaceX deliberately destroyed SN7 during a ground test to gather data for future flights. SN8, which took to the air on Dec. 23, 2020, performed complex aerial maneuvers and flips during the program's first high-altitude launch. It flew to 7.8 miles (12.5 kilometers) but failed to stick the landing, according to a video shot from the landing pad that showed it exploding in a fireball on the ground due to lower-than-expected pressure in the fuel tank header. Crash and crash again SpaceX's Starship SN10 rocket prototype explodes after a successful liftoff and soft landing at the company's Boca Chica, Texas launch site on March 3. This view was provided by SPadre.com.