According to Elon Musk, SpaceX has successfully completed its latest Starship prototype test in a uniquely uneventful fashion, great news for the next-generation rocket’s next steps and first flight tests.
The SpaceX CEO revealed the news some 12 hours after the company wrapped up the Starship tank test at its Boca Chica, Texas facilities. Another excellent example of SpaceX’s preferred process of agile development, the test followed just nine days after the Starship SN01 prototype’s first cryogenic test unexpectedly unearthed a design flaw. SpaceX analyzed the results of Starship SN01’s unintentional launch debut and drew up plans to rapidly repurpose a Starship tank initially destined for the SN02 prototype.
By using existing hardware to test an upgraded iteration of the part that destroyed Starship SN01, SpaceX has now effectively retired the risk posed by that prior failure less than two weeks after it occurred. Elon Musk specifically noted that the former SN02 engine section “passed cryo pressure & engine thrust loads,” confirming that there was more to the exceptionally uneventful evening of March 8th than met the eye. While putting on much less of a show for local observers, this particular boring test is a great sign for the next few steps of SpaceX’s Starship development program.
SN2 (with thrust puck) passed cryo pressure & engine thrust load tests late last night
— Elon Musk (@elonmusk) March 9, 2020
Simply put, despite successfully demonstrating that Starship’s improved “thrust puck” and engine section can survive flight-level tank pressures and the thrust of a Raptor engine, one would be hard-pressed to determine as much by inspecting the prototype that managed the feat. Such a visually uneventful test is a first for SpaceX’s post-Starhopper Starship testing, where “before” and “after” photos typically start with a shiny tank and finish with a well-distributed field of steel shrapnel.
Musk’s description of the test suggests that SpaceX’s intention with the SN02 test tank – built in just two weeks – was to stress it up to (and likely beyond) the pressures and mechanical stresses Starship engine sections will need to survive in flight. In simpler terms, they likely tried to burst the tank by pressurizing it with liquid nitrogen, a supercool cryogenic fluid. It’s unclear exactly how far SpaceX pushed the tank, but it’s safe to say that it went at least as high as past test tanks, meaning 7-8.5 bar or 100-125 psi. At a bare minimum, a test that failed to reach Starship’s minimum flight pressure of 6 bar (90 psi) would be of dubious value for the actual orbital ship.
A step further, SpaceX installed a hydraulic jack underneath the test tank in a bid to simulate the stresses it would experience with a single Raptor engine. Capable of producing approximately 150-200 tons (1500-2000 kN) of thrust, even Raptor is relatively minor compared to the Starship tank’s likely ~500 metric ton (1.1 million lb) mass. Still, the fact that the SN02 test tank survived the combination of a highly pressurized tank and the simulated thrust of a Raptor engine suggests that SpaceX is now ready for a more successful repeat of Starship SN01 testing.
Confirming those suspicions, Musk subsequently revealed that the Starship prototype integrated immediately after the SN02 test tank will likely attempt the first Raptor static fire tests and may even perform short flights further down the road. As always, SpaceX’s testing programs are fluid and likely to change as new results continuously shape the path forward, meaning that Starship SN03 could easily be destroyed during testing. Starship SN04, said by Musk to be the hopeful candidate for “longer [test] flights,” would thus be repurposed to continue SN03’s test campaign — and so on with SN05, SN06, and beyond.
Regardless, as the CEO notes, perhaps the most important aspect of all these rapid-fire tests is that SpaceX is quickly building up an impressive Starship production line. Before, during, and after SN02’s test campaign, SpaceX’s South Texas team has been simultaneously fabricating and stacking new steel rings, bulkheads, and noses for the next few Starship prototypes. As a result, Starship SN03’s tank section could be just a week or two away from complete integration, after which SpaceX will likely transport it to the launch pad to prepare for Raptor static fire testing.
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