CEO Elon Musk says that a new ‘test tank’ with a thin skin Starship has just passed its first test run and has taken full advantage of the delays regarding Starship SN9’s planned launch debut.
Delayed by a lack of FAA approval for unknown reasons, Starship SN9’s launch debut of 12.5 kilometers (7.8 miles) (virtually identical to SN8’s 12.5 km launch last month) is in limbo pending a ” FAA Review ” according to Musk. SpaceX thus found at least 24 hours of guaranteed inactivity for Starship SN9, the time the company quickly chose to complete crane transport and, more importantly, Starship’s first stress test ‘test tank’ in months.
SpaceX’s latest ‘test tank’, known as Starship SN7.2, is the third to carry the SN7 moniker, and was apparently built primarily to test refinements to the structural design of the rocket. Following test tanks SN7.0 and SN7.1, both of which are used to qualify the use of a new steel alloy in an otherwise unchanged design, SN7.2 – probably built from the same alloy – was instead used to determine or SpaceX can start pruning. the margin of an increasingly mature technology.
Oddly enough, SN7.2 is a kind of fusion of its predecessors: the combination of the sturdy shape of SN7.0 with the use of a rear bumper of SN7.1, but without SN7.1’s Starship dress (the three rings at the bottom). It was welded directly to its black test standard and it is unclear why SpaceX chose to give SN7.2 a boost dome, as the thrust of Raptor engines can only be simulated with hydraulic rams if the tank is on one of the two Starship launches are mounted.
Whether or not SpaceX actually tests that aspect of SN7.2, the tank’s main task is to determine if future Starships (and perhaps Super Heavy boosters) can be built from thinner, lighter steel rings. The domes appear to be identical to the previous ships, but the writing on the outside of the tank strongly implies that the three rings were constructed of 3 mm steel, rather than the 4 mm plates that each Starship has used in the last twelve months. made.
SpaceX started charging the thin sheet tank with liquid nitrogen (which is used to simulate cryogenic propellant without the risk of an explosion) around 09:00 CST. It is unclear what the test involved, but it probably involved increasing the tank’s internal pressure to levels reached by SN7.0 and SN7.1. Musk said earlier that 6 bar was the minimum required for a flight in the runway, which translates to 7.5-8.5 bar to reach an operating standard of 25-40%.
That SN7.2 survived the initial pressure test is good for the significant mass reduction that SpaceX needs to optimize Starships for an efficient orbital flight, which can shave 5-10 tons from the dry mass of future ships. For rotating rocket stages, each kilogram of mass reduction translates to an extra kilogram of cargo capacity, while boost stages (ie Super Heavy) offer much lighter ratios in the order of 10: 1, which means that the addition of 5-10 kilograms of rocket hardware reduces the maximum load capacity by net ~ 1 kg.
Depending on when SpaceX is allowed to launch Starship SN9, the company’s next test may involve pushing SN7.2 until it bursts, to determine if the tank’s thinner skin significantly affects performance as a pressure vessel.