Featured Image Source: @BocaChicaGal via Twitter
SpaceX is rapidly working towards the development of their next-generation spacecraft, Starship. The ultimate goal is to develop a fully reusable craft that will help humanity establish a permanent colony on Mars by 2050. The rocket company is running 24/7 operations dedicated to building many Starship prototypes to test out, at their South Texas facility located in Boca Chica Beach. SpaceX aims to initiate a production factory capable of manufacturing a Starship per week, eventually one every 72 hours. This year, they expect to manufacture at least 20 Starship vehicles, that will be used to test out different features. Engineers have conducted several tests with scaled-down Starship prototypes in Texas. On February 28, SpaceX conducted a cryogenic pressurization test on the Starship SN1 vehicle, that was expected to conduct a 20 kilometer test flight above Boca Chica, but during the test the prototype was destroyed. Read: SpaceX conducted a pressurization test on Starship SN1 -the prototype exploded! [Video]
The founder and Chief Engineer at SpaceX, Elon Musk, said the SN1 vehicle had an issue on a "puck" at the bottom of the tank that took all the thrust load. The "thrust puck" is the structure where Starship's Raptor engines are mounted. So, the tank design and welding needed to be improved. Engineers must make sure the structure can withstand flight pressures and the thrust-load power of a Raptor engine. Teams quickly focused on resolving the "thrust puck" issue as they moved on to manufacture the second tank, prototype SN2. They conducted another series of pressure tests over the weekend on an improved SN2 stainless-steel dome tank.
Boca Chica residents shared video of the test (shown below).
First, the Starship SN2 test tank was filled out with water to see if it was welded properly. Then on Sunday, teams performed another cryogenic pressurization test using inert liquid nitrogen. Musk said the prototype passed the test.
"SN2 (with thrust puck) passed cryo pressure & engine thrust load tests late last night."
He did not give any specifics as to what bar strength the test tank structure endured. Though, a couple of weeks ago, he stated that the stainless-steel structure and welds needed to withstand a pressure strength of 8.5 bar. And explained that a 7.1 bar "is pretty good as ~6 bar is needed for orbital flight" but that an ~8.5 bar "is the 1.4 factor of safety needed for crewed flight." So, its likely that the SN2 test tank made it to a bar within 6 - 8.5 bar (equivalent to about 90 - 125 PSI), the range needed for flight.
The successful SN2 tank dome pressurization test takes the company closer towards developing better prototypes that will take flight soon. Musk said the third and fourth prototype in the SN series could be used to conduct test flights this year.
"Static fire & short flights with SN3, longer flights with SN4, but spooling up the whole Starship/Raptor production line is really what matters."
Static fire & short flights with SN3, longer flights with SN4, but spooling up the whole Starship/Raptor production line is really what matters— Elon Musk (@elonmusk) March 9, 2020
He previously explained that manufacturing many Starships is a crucial move towards developing rapid iterations, "A high production rate solves many ills. If you have a high production rate, you have a high iteration rate. For pretty much any technology whatsoever, the progress is a function of how many iterations do you have, and how much progress do you make between each iteration. If you have a high production rate then you have many iterations. You can make progress from one to the next." That is one of the reasons why SpaceX aims to ramp-up the manufacturing speed, to test out and see - what works? what fails? - in order to quickly modify the vehicles' design. It is likely teams will begin building SN3 simultaneously as Starship SN2 parts are being tested this month.