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1 minute ago, mikegarrison said:

I remember when people on this forum were complaining that the FAA was moving too slowly because they didn't approve this orbital test flight back in the spring.

I mean, technically it still hasn't happened - the environmental assestment is out, but not the launch license which the FAA also approves

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Not all of the work that's been done since the spring has been absolutely necessary. If the mitigated FONSI had been ready earlier I'm sure SpaceX would have MacGyvered a launch opportunity for B4/S20.

The launch license is actually a fairly minor thing in comparison to the environmental assessment. It'll come through when SpaceX are ready to declare the launch vehicle is tested to a state of launch readiness.

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4 hours ago, mikegarrison said:

I remember when people on this forum were complaining that the FAA was moving too slowly because they didn't approve this orbital test flight back in the spring.

If I remember correctly SpaceX was nearly ready for first launch, but the approval process started dragging out a lot so they decided to implement changes they had in pipeline whilst waiting for the approval. And since they haven't been sitting still all this time but actually working I'd say there was a lot of modifications and upgrades to be made and there's no point in stopping mid way.

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Problems with the heat tiles discussed here:

 

 

 Perhaps they should try the metallic heat tiles developed for the X-33? About same weight and thermal protection as ceramics , but were screwed on with bolts, and have superior impact and rain resistance.

 

  Robert Clark

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2 hours ago, Exoscientist said:

Problems with the heat tiles discussed here:

I saw a couple of his videos and turned them off after a few minutes each time. Hot garbage.

1. There has been zero test yet on the current TPS, and there will not be until the orbital flight test—that's what it's for.

2. Loss of tiles in the test stand is not useful, nothing about a Starship static fire in the low test stand maps to actual flight stresses. Too close to the ground, so much worse acoustic environment. FOD a real issue, etc. Even so the number of lost tiles has decreased significantly per test.

 

2 hours ago, Exoscientist said:

 Perhaps they should try the metallic heat tiles developed for the X-33? About same weight and thermal protection as ceramics , but were screwed on with bolts, and have superior impact and rain resistance.

The X-33 never flew. Not actually tested—the only real test is EDL.

SpaceX will iterate the tiles as needed with actual data from reentry. They've already done loads of computer simulations, and ground testing of tiles I am sure, but the real test is the real world. Or I suppose they could spend billions and decades coming up with a perfect theoretical TPS system, then "get it right the first time" in 20-30 years?

Edited by tater
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1 hour ago, tater said:

I saw a couple of his videos and turned them off after a few minutes each time. Hot garbage.

1. There has been zero test yet on the current TPS, and there will not be until the orbital flight test—that's what it's for.

2. Loss of tiles in the test stand is not useful, nothing about a Starship static fire in the low test stand maps to actual flight stresses. Too close to the ground, so much worse acoustic environment. FOD a real issue, etc. Even so the number of lost tiles has decreased significantly per test.

The X-33 never flew. Not actually tested—the only real test is EDL.

SpaceX will iterate the tiles as needed with actual data from reentry. They've already done loads of computer simulations, and ground testing of tiles I am sure, but the real test is the real world. Or I suppose they could spend billions and decades coming up with a perfect theoretical TPS system, then "get it right the first time" in 20-30 years?

This the acoustic doing static fire of starship on an low stand is irrelevant, now it will be plenty of vibration during an superheavy launch but also ways to dampen them. 
The first starships will be disposed anyway, nowhere to land there you can economically recover as far as I know. 

On the other hand that the X-33 newer flew is a bit irrelevant if the tiles was good, on the other hand that project was part of the star wars project. An brilliant copy the Soviet strategy of scary paper projects but with much better special effects. 
Made sense Soviet Union copied the space shuttle because they thought it was important. Well let them try to copy something we can not build in 30 years even if dumping Apollo program money at it but still plausible enough and its obvious the US trying lots of stuff looking for stuff who works. 

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59 minutes ago, magnemoe said:

This the acoustic doing static fire of starship on an low stand is irrelevant, now it will be plenty of vibration during an superheavy launch but also ways to dampen them. 

The environment is worse for static fire than launch. Tile loses have been greater lower on SS, and SS will be farther from the SH engines by a lot—and it has a high launch stand, etc.

 

59 minutes ago, magnemoe said:

The first starships will be disposed anyway, nowhere to land there you can economically recover as far as I know. 

They don't have to recover to know if the TPS worked, they have to see the vehicle after peak heating intact, not as a cloud of debris. That tells you the TPS works at some level. Future vehicle recovery helps from there.

 

59 minutes ago, magnemoe said:

On the other hand that the X-33 newer flew is a bit irrelevant if the tiles was good, on the other hand that project was part of the star wars project.

It's not irrelevant at all. There are many plausible TPS strategies for rapidly reusable vehicles. All were tested and simulated short of flight at some level—but the proof of actual efficacy requires reentering. Suggesting one never actually used TPS concept instead of another never actually used TPS concept can certainly be argued, but neither can be said to be better, as neither has any real world data. Also, I'm pretty sure the TPS guys at SpaceX are not idiots. They may be barking up the wrong tree, but they are not brain dead, their concept must have some decent data behind it.

 

59 minutes ago, magnemoe said:

An brilliant copy the Soviet strategy of scary paper projects but with much better special effects. 
Made sense Soviet Union copied the space shuttle because they thought it was important. Well let them try to copy something we can not build in 30 years even if dumping Apollo program money at it but still plausible enough and its obvious the US trying lots of stuff looking for stuff who works. 

A copy of something show to be effective is fine—you know it can work. Starship TPS will very likely iterate as it's something from this project that has literally never been done before (zero refurb reuse).

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15 hours ago, mikegarrison said:

The reason it is called "stainless" steel is because it is resistant to oxidation.

Nuanced thing but there are also many grades of stainless and some are more corrosion resistant than others. The first few SN testbeds used 301, which is a widely used and relatively inexpensive alloy. There was talk about them switching to 304L or perhaps their own formulation in more recent models. Anyone know where they landed on that? I know 304L is easier to weld so that might be a factor. I've used both 304 (though not 304L) and 316 for architecture components and the former absolutely will rust within a few years in coastal environments. 

Edited by Pthigrivi
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3 minutes ago, Pthigrivi said:

Nuanced thing but there are also many grades of stainless and some are more corrosion resistant than others. The first few SN testbeds used 301, which is a widely used and relatively inexpensive alloy. There was talk about them switching to 304L or perhaps their own formulation in more recent models. Anyone know where they landed on that? I know 304L is easier to weld so that might be a factor. I've used both 304 (though not 304L) and 316 for architecture components and the former absolutely will rust within a few years in coastal environments. 

They went to some form of 304 (unsure if L for sure), and there was still talk of a special alloy just for them, nothing specific unless some label on a steel roll has been shown on NSF.

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22 hours ago, tater said:

...

The X-33 never flew. Not actually tested—the only real test is EDL.

SpaceX will iterate the tiles as needed with actual data from reentry. They've already done loads of computer simulations, and ground testing of tiles I am sure, but the real test is the real world. Or I suppose they could spend billions and decades coming up with a perfect theoretical TPS system, then "get it right the first time" in 20-30 years?

  The X-33 tiles were well tested, as well were as the Starship tiles:

REUSABLE METALLIC THERMAL PROTECTION SYSTEMS DEVELOPMENT
Max L. Blosser*, Carl J. Martin*, Kamran Daryabeigi*, Carl C. Poteet **
*NASA Langley Research Center, Hampton, VA, USA
** JIAFS, The George Washington University, Hampton, VA, USA
https://ntrs.nasa.gov/api/citations/20040095922/downloads/20040095922.pdf

The metallic tiles had better resistance to impact and rain than the ceramics at about the same weight, and would not require water proofing. They also would have closer thermal expansion properties to the steel Starship.

Fig.3 Layered metallic sheeting separated by insulation.04-A5-BF90-A019-4278-A5-CC-C3-F33-E7-AFF

 

Fig.21 Metallic TPS at same weight of ceramic tiles, ~10kg/m^209-E4-AEC5-8-B96-424-E-A117-AC5-A11-E2-F

 
Edited by Exoscientist
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34 minutes ago, Exoscientist said:

  The X-33 tiles were well tested, as well were as the Starship tiles:

I know they have been tested in a lab, and simulated as well.

I was precise by what I meant by testing—actual reentry.

Saying one is substantially better when NEITHER has been demonstrated makes no sense to me. Orion EFT-1 was to test their heat shield, which was a legacy design. From one of their engineers regarding EFT-1:

Quote

“We’re interested in seeing the performance of the heat shield,” Bray said. “We have arc jet test facilities where we test the heat shield for the thermal environments, but we can’t do it at the same time as we do thermal and pressure, and it’s really one of the most critical systems that we’ve got.

“It’s about 80 percent the velocity of what we’ll have on the other missions, but we’ll get a pretty good test of its maximum capability with temperature and pressure,” Bray said. “We can’t quite get that using modeling on the ground.”

 

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