If you don't succeed at first, try, try again
On the 22nd of December, SpaceX's 165 feet (50 meters) tall Starship SN9 was once again put through its paces after some speedy repairs. Coming only a few weeks after it suffered a significant handling or production accident that saw it tip several degrees and impact the walls of its production facility.
The accident caused the craft to impact its four pre-installed flaps, damaging them, seemingly beyond repair. By all accounts, the strong design of the flap's structural connecting mechanisms was unharmed -- much to the relief of engineers.
WOW! Amazing RCS testing on Starship SN9. She's alive for the first time! Some sweet cold gas thruster action there! Seemed much more powerful than we've ever seen before (no clue!)— Chris B - NSF (@NASASpaceflight) December 29, 2020
Replacement of the damaged control surfaces was carried out in earnest, taking only a few days to complete.
A few days ago, with Starship SN9 in position on its launchpad, ambient temperature pressure tests were conducted. These involved filling the Starship's propellent tanks with benign air-temperate nitrogen gas.
Used to check for leaks, verify basic vehicle valve and plumbing performance, and ensure a basic level of structural integrity, SN9 appeared to pass with flying colors.
These tests were then followed by the more dramatic cryogenic proof testing of the craft. The craft began to develop a frosty coating after loading its oxygen and methane tanks with liquid nitrogen at around 2:30 pm CST on Tuesday this week.
This "cryo proof" testing is used to check the craft's reaction to thermal stresses to make sure that SN9 can safely load, hold, and offload supercooled liquids.
SN9 is capable of holding somewhere in the region of 1,200 metric tons of liquid nitrogen when fully loaded, and keen observers believe that the test did not include it's liquid oxygen "header" tank as the nose of SN9 appeared frost-free.
More tests might be on the way very soon
Some believe this implies a further test later this week or early next week. Or they are confident that the header tank and transfer tube do not require further testing.
According to NASASpaceflight, the test on Monday and Tuesday were uneventful and seemed successful. This means that SpaceX may now move directly on to the triple-Raptor static fire preparations.
The recent testing is also interesting as, in a first, Starship SN9 was transported to the launch pad with two of three central Raptor engines already installed. The third "missing" engine was later installed within a few days of arrival.
SN9 is also the first Starship to attempt its first proof tests with a single Raptor, let alone three of them.
There are rumblings that such testing may occur between the 4th, 5th, and 6th of January 2021 following a series of 8 am to 5 pm CST road closure requests made by the company. According to this Twitter user, an open road closure request for the 30th of December has been canceled.
According to NASASpaceflight, SpaceX will likely attempt a 7.8 miles (12.5 km) launch similar or identical to SN8’s as early as a few days after that static fire.