Not totally sure, to be honest. Some of it is entrained exhaust gases. Some is probably sublimating water ice. Maybe some is venting from the tanks. Hard to be sure of the overall mix, though.
Mach diamond and shock diamonds are different names for the same thing. You can read LSLGuy’s link for more info. In the pic I posted, it’s the equilateral triangle shape at the bottom. It would look more like a diamond if the image extended down further, and there would be further (less distinct) diamonds further down.
It’s not easy to explain, but they show up in supersonic exhaust, like from rockets and afterburning jet engines. The cleaner the exhaust flow, the more distinct they tend to be.
You can see at least 4, maybe even 6 distinct mach diamonds in this pic:
The diamonds are the whiter part of the exhaust, as compared to the more pink portions. The first two are pretty distinct, while the two below don’t look much like diamonds but are clearly high-density zones vs. the rest of the plume, and below that I can see similar variation but it may be partly in my imagination. They’re pretty close to evenly spaced.
Around 190 pounds of steel can be ablated from the platform each launch.
The very ballpark density of steel is ~0.28 lbs/in^3. So 190 lbs is ~53 in^3. Across a (total WAG representative) 10’x10’ surface, that represents ablating ~4 thousandths of an inch of steel. The total pad (or vehicle) structure is vastly larger than a tiny 10’x10’ area.
IOW, not much damage really, unless it’s concentrated in a very small area. Which seems highly unlikely.
Will somebody need to keep an eye out to see that ablation isn’t concentrated someplace? Sure. Will this be a major life-limiting aspect of either the vehicle or the pad? Not even remotely.
Ugh, can we get a better media? The old one is broken.
Next up: airplane tires have to be replaced occasionally. Boeing abandons reusable aircraft!
Never mind that we’re actually talking about the pad here, not the rocket.
IFT-3 2024 confirmed 
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John Kraus: From a technical readiness standpoint, what’s a feasible timeline for Flight 3?
It would be amazing if they could squeeze a third flight into 2023… but it seems a liiiiiitle unlikely.
This is a real picture:
Finally, the 21st century we were promised.
Awesome slo-mo video of the hot staging:
Read the tweet and look closely at the business end of Starship.
ETA: The quality of the embedded version sucks. Click through the link to see the high-quality version, and make it full-screen.
Moderating
This isn’t just a news aggregation thread. There is still a lot of factual information being discussed here.
But since the thread has also become a news aggregation thread, and it seems like a topic where people want to express their opinions about various things, I think overall that the thread will do better in MPSIMS.
And given the optic, any factual information is of course still very much welcome.
Moving from FQ to MPSIMS.
No, the “not fully reusable” part from the article refers to the ring between the two stages.
Ahh, gotcha. I thought the 190 lbs you mentioned was referring to the title. I didn’t read the article since I try to avoid clickbait.
Yes–they do have some tentative plans to basically do a coin flip with the hot staging ring just after separation. It’s not required, but may give a small performance boost under some conditions, since it weighs about 20,000 lbs and otherwise has to be boosted back.
I suspect they’ll do it only for a limited timeframe. Not during the test flight phase since it’s just extra complication and they’re not trying to maximize performance yet. And not in the long term once they drive down all other costs (and do other weight optimization). But it may make sense in the mid-term; for example, for filling the propellant depot for Artemis.
It’s a dumb hunk of stainless steel, and probably doesn’t cost much. Might only be a few tens of thousands of dollars, even with fabrication. So it’s possible that the numbers will work out that it’s always a savings to discard it, especially since their launch tower makes it so trivial to put things on the stack. Or they may do it selectively, depending on the payload performance requirements. We’ll have to see.
Either way, I still rate the title as clickbait since even at 20,000 lbs, it’s still a trivial part of the rocket.
Yeah, it’s almost as bad as saying the rocket isn’t fully reusable because it needs to be restacked and fueled between trips.
Well, they eventually plan on generating methane and oxygen by combining water with atmospheric CO2 via the Sabatier reaction, so even the propellant will be reusable in a sense .
It’s possible that the hot staging ring is viewed as basically ablative. I’m not sure how well the structure stands up to the “heat treatment” it gets, but it’s possible that it loses enough strength that it needs to be remanufactured anyway. If so, then all they’re losing is the raw material cost, which is <$1/lb.
Eric Berger, known war criminal, fires back at the haters:
In short, Berger says that Starship is now as successful as SLS. But wait: SLS made it to orbit and Starship didn’t, right? Yes, but the upper stage flown on the SLS was literally just the one from the Delta 3/4 rockets. You don’t get to take credit for a stage that first flew in 1998. So the only new part was the booster, which worked fine in both cases. And while Starship’s booster didn’t survive much past separation, neither did SLS’s.
I’m a super fan of Starship, but agree it sucks less than SLS; And I’m an idiot space enthustist so thimgs may be less on SX’s side.
Did you mean to say “I’m not a super fan of Starship?” I’m having a hard time parsing your post otherwise.
I mean I’m a currently superfan that’s disappointed and frustrated in Starsship. SLS sucks, but Starship’s cadence has been crap. Not entirely their fault. I was a superfan on SpaceX because of Falcon and Falcon Heavy, but the big stuff has hit a wall.
Where do we see this improving? Another incremental, partially successful launch in April, that pushes the ball very incrementally? Or May, July? Where are we a year from now, still blowing shit up and calling that kool?
Ahh, gotcha. Well, I certainly can’t be certain, but I expect the iteration rate to improve significantly. SpaceX reconstructed the pad, made numerous improvements to the booster, and made it though a challenging licensing process. Next time, there are few to no pad changes, and the licensing should be dramatically easier.
SpaceX already has a few craft hanging around ready to go, including an improved upper stage (the upper stage from IFT-1 to IFT-2 was not improved very much). They aren’t really hardware limited, and I think Musk is probably right that the vehicle will be ready in a few weeks. When that translates to another flight test, I dunno, but I think April would be extremely pessimistic. Feb is probably likeliest and Jan isn’t too much of a stretch. I’m not quite counting out Dec, either…
A semi-educated guess, but I would suspect the next launch is in January. With March/April as the next launch window. WAG is that one of those two will achieve orbital velocity with Starship. Neither will produce a successful landing of either stage, but both will get closer to that goal.
FYI, I’m still doubtful they will get to a successful booster landing in the next 2-3 years. I think the ullage/fuel hammer issues will be very difficult to overcome reliably.
In short, I think the cadence will increase from here out, but Starship is such a giant leap forward that the technical issues are an order of magnitude greater than they faced with Falcon/Falcon Heavy - with a significant increase in timeframe to solve. Moon by 2028 would be a resounding success (relatively speaking) for the overall program.
But they’ve surprised me before. SpaceX is the best of the best when it comes to spaceflight.