A Mostly Successful Flight Test 6

I have yet to see an authoritative explanation for why the attempt to recover Booster 13 with the chopsticks was called off, but with the exception of not getting the dramatic, semi-addictive video of the chopsticks catching the Booster it looked to be quite a successful flight test.  (I've probably watched videos of capturing the booster on flight test 5 over 30 times)

Last night, Igor commented that,“Unconfirmed rumor has it there was a malfunction on the tower. Stay tuned.” I watched a video that Scott Manley released early this morning and while not very specific, he puts up some information that agrees with that synopsis.  I expect we'll get a more thorough answer in a day or two. 

The emphasis in this mission was on the Starship, that had been extensively modified, especially in the heat shield. During the SpaceX video stream, one of the Engineering Managers who often narrates those presentations gave some impressive details.

Kate Tice, a SpaceX engineer hosting the company's live broadcast of the mission, said teams at Starbase removed 2,100 heat shield tiles from Starship ahead of Tuesday's launch. Their removal exposed wider swaths of the ship's stainless steel skin to super-heated plasma, and SpaceX teams were eager to see how well the spacecraft held up during reentry. In the language of flight testing, this approach is called exploring the corners of the envelope, where engineers evaluate how a new airplane or rocket performs in extreme conditions.

2,100 heat shield tiles?  It wasn't so much to reduce weight (every tile takes up some of the payload capacity of the ship) but to check how specific areas of the Starship's skin handle the searing heat of reentry. In that Scott Manley video, he shows some areas of the exposed skin and how the few thousands of degrees the reentry brought had some of the steel apparently buckling. Yet another reason to use stainless steel instead of aluminum or carbon fiber.  As the heat eased, the stainless just shrugged it off and returned to the original shape.

Many of the removed tiles came from the sides of Starship where SpaceX plans to place catch fittings on future vehicles. These are the hardware protuberances that will catch on the top side of the launch tower's mechanical arms, similar to fittings used on the Super Heavy booster.

"The next flight, we want to better understand where we can install catch hardware, not necessarily to actually do the catch but to see how that hardware holds up in those spots," Tice said. "Today's flight will help inform 'does the stainless steel hold up like we think it may, based on experiments that we conducted on Flight 5?'"

The Space Shuttles had lots of issues with tiles and had a problem that certain tiles could only be used in some places. I've read they practically had only one tile that worked for any specific spot on the shuttle complicating repairs and refurbishment between missions.  SpaceX uses identical hexagonal tiles as a general rule, although it seems to me they must have some tiles that only work in a specific place, or families of tiles for specific places.  

Integrated Flight Test 6, seconds after launch.  Image credit: SpaceX

You might have seen some photos of Elon Musk with a group of VIPs he hosted for the launch, including President-Elect Trump, Ted Cruz, RFK Jr., Donald Trump Jr. and more. A person I didn't recognize was General Chance Saltzman, the U.S. Space Force’s chief of space operations. This is being taken as a sign that Space Force is interested in what the world's biggest and most powerful rocket could do for them.

The important tests on Starship have all been reported as passing successfully.  Proving the Raptor engines can re-ignite in orbit was an important milestone in Starship development. After the mission, Musk said they'd do one more Starship landing in water and would try to catch the ship with a launch tower on the 8th flight. It's debatable when IFT-7 will be but I think it could be before the end of this year.  IFT-8 then, figures to be in the first quarter of '25.