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Home / Science / After the Raptor static shooting was over, the “burst disk” saved SpaceX Starship

After the Raptor static shooting was over, the “burst disk” saved SpaceX Starship



At around 7:15 p.m. local time, the SpaceX Starship prototype SN8 activated one or several Raptor engines for the third time in a row, which aroused the surprise of onlookers. They were just looking forward to the rehearsal. An hour later, CEO Elon Musk revealed that SpaceX had actually lost control of the rocket.

Unfortunately, this is not the first time for SpaceX that a fire has caused a starship to lose control. As early as May 2020, Starship serial number 4 (SN4)-the first full-scale prototype with Raptor installed-completed its third successful static shooting test. After a while, the exhaust pipe near the engine caught fire and burned for a minute or two. In the end, most likely due to wiring or pipeline damage, SpaceX seems to have lost control of SN4 and had to wait two full days for the cryogenic propellant to boil and evaporate before the convoy can approach the rocket for inspection, repair and regain control.

Now, Starship SN8 is likely to suffer a similar but not identical failure, reducing a certain degree of control. About an hour after the rocket’s third Raptor static shot, Elon Musk tweeted that SpaceX had lost control of the starship’s pneumatics, referring to the hydraulic system required to operate most rocket valves . For SN8, this only means bad news.

As cryogenic liquids (and everything) heat up, they expand and occupy more volume. In order to counteract the endless process of low-temperature propellant heating, boiling and transforming into gas, fresh propellant is almost constantly loaded when hot gas is discharged, thereby maintaining a safe fuel tank pressure. If the ability to discharge these gases is lost, then the ability to maintain a safe pressure will follow.

As Musk mentioned above, thankfully-unexpectedly-Starship SN8 is equipped with one or more rupture discs, which are disposable mechanical valves designed to open (ie, burst) above a certain pressure. SN8’s Nosecone rupture disc does just that. Its blasting creates an outlet for the pressure inside the rocket, thereby preventing the explosion of a small nose-based liquid oxygen (LOx) tank.

After the seemingly successful static fire, a large amount of molten metal poured out from the engine part of the starship SN8. (NASASpaceflight-Bocachicagal)

Unfortunately, the harbinger of “Starship” losing control is a less positive story. According to Musk, one of the SN8 ignited Raptor engines may have been severely damaged, melting one or more key engine components. It is not clear how the seemingly uncontrollable engine failure completely evolved into the starship hydraulic system, but it is safe to say that redundancy will be added and the updated design will be implemented to ensure that similar failures will not occur again.

It’s worth noting that the unofficial LabPadre and NASASpaceflight.com live broadcasts clearly show the starship literally Dripping molten metal After the fire is quiet, it lasts for more than two minutes. Regardless of the cause of this extremely hot fire, anything that can continue to melt the metal for a few minutes will almost certainly damage the stern of the Starship SN8 and the Raptor engine installed in it. The SN8’s main LOx tank was not destroyed, which is simply a miracle.

About 80 minutes after ignition and causing the Raptor to catch fire, the nose cone “bursting disc” of Starship SN8 worked according to design requirements, thereby reducing construction pressure and avoiding more destructive failures. (NASASpaceflight-Bocachicagal)

Eventually, the SN8 may require extensive repairs, including one, two or even three replacement engines, before it can safely restart testing and proceed with its first launch of 15 kilometers (about 9.5 miles). In addition, SpaceX’s lack of valve control may mean that the company will have to wait at least 24 hours or more before workers can safely return to the launch pad and begin these inspections and repairs.

Update: The roadblock was demolished at around 11 pm local time, and SpaceX staff appeared to have returned to the ground, indicating that the Starship SN8 has been completely removed and can be approached safely. Inspection and maintenance will likely begin as soon as possible.




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