Despite the provisional preservation plans, SpaceX totally discarded the wreckage of the first high-altitude starship prototype, cleaning up the landing zone that impacted the imminent launch of its successor.
Known as serial number 8 or SN8, the starship prototype was the first of any kind to fly beyond 150 meters (~ 500 feet), reaching an altitude of 12.5 km (~ 7.8 mi) on 9 December during its breathtaking launch debut. In an unexpected turn, SpaceX kept the Starship SN8 thrust-to-weight ratio as low as possible, extending what could have been a two or three minute test in an almost seven-minute ordeal with three consecutive Raptor engine cuts during the climb.
At its height, SN8 used cold gas thrusters to turn in a belly-down, free-fall orientation ~ 95% of the way back to Earth before firing two of its three Raptor engines, making a wild jump back into position vertical landing and almost guaranteeing a smooth landing. Unfortunately, about 10-20 seconds before the planned landing, what Musk later described as low pressure in the methane collection tank left the starship’s engines out of fuel and more or less cut off all appreciable thrust, making the SN8 reached its landing zone by traveling about 40 m / s (~ 90 mph) very fast. The rocket hit the concrete block, crushed it and exploded.
By all accounts, success was one of the least likely results that SpaceX expected from the SN8 debut at high altitude, with Musk himself estimating the chances of total success at just 33%. In addition, the SN8 starship effectively achieved a low-speed landing regime that the SN5 and SN6 ships demonstrated perfectly with consecutive 150m jumps and landings in August and September 2020.
In other words, despite the explosive ending, the high-altitude SN8 debut was a spectacular success for SpaceX’s Starship program – possibly even preferable for a perfect landing, as it discovered an unexpected problem with the pressurization of the fuel tank. In addition to the landing failure, the starship checked each box on the SpaceX test flight list, successfully debuting several Raptors, demonstrating various in-flight engine shutdowns and engine reclosures; proving that an unprecedented ‘skydiving style’ landing maneuver is possible and feasible; and successfully test the starship’s ability to control itself in that belly-down orientation with thrusters and four massive flaps.
Speaking in a recent interview with Ars Technica, in the words of SpaceX’s pragmatic COO and President Gwynne Shotwell, the SN8 launch debut “lessened the risk [the Starship] program very massively. ”According to Musk, SpaceX engineers were able to quickly determine why the Starship SN8 methane collection tank was unable to maintain the fuel (pressure) flow required for Raptor’s landing flare and quickly implemented a solution .
Instead of autogenously pressurizing with methane, Starship SN9 will use helium to pressurize its fuel collection tank, serving as a temporary fix while SpaceX determines what changes need to be made to get rid of that helium crutch. The landing pad now free from the starship’s remnants and the more or less repaired SN8 impact crater, the only thing between the SN9 starship and its own 12.5 km launch debut is a Raptor triple static fire test. . Initially expected for January 4, SpaceX never managed to spend more than a few minutes of trying, while a backup window on January 5 was canceled later that night. The test could now take place before (NET) Wednesday, January 6.
Fortunately, although SpaceX was unable to save the entire shattered nose section of Starship SN8, the company managed to extract a nose flap that was largely intact. The rest of the remains were discarded on the spot and transported by truck, but it is possible that certain significant components of the SN8 – particularly the recovered flap – end up being exposed in one or more SpaceX installations.