SpaceX Starship : Texas Prototype(s) Thread 12 : Discussion

[Chris Bergin]

New thread for discussion of the Starship prototype being built in Boca Chica, Texas.  Previous posts on these prototypes can be found in these threads:

Discussion 1

Discussion 2

Discussion 3

Discussion 4

Discussion 5

Discussion 6

Discussion 7

Discussion 8

Discussion 9

Discussion 10

Discussion 11

SpaceX BFS : Phase 2 - Starship Orbital Prototype(s) - Photos and Updates -1

SpaceX BFS : Phase 2 - Starship Orbital Prototype(s) - Photos and Updates -2 (Latest)

SpaceX Texas launch site Discussion and Updates - Thread 9

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L2 Boca Chica (intense level updates)
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[Chris Bergin]

Here, this will kick things off for you

I've put together an update article on SpaceX Boca Chica, per where things stand as they move through hop tests... all the way to preparations for Super Heavy!

As always, the amazing photojournalism from Mary (@BocaChicaGal) really helps!

https://www.nasaspaceflight.com/2020/08/sn6-campaign-future-starships-hatch-next-leap/

https://twitter.com/NASASpaceflight/status/1295181239809388545

[russianhalo117]

Pics taken this evening at the build site.

S/N on the test barrel says 00309 something so 309 Stainless anyone?? 304 test barrel had similar serial number.

[baking]

Pics taken this evening at the build site.

S/N on the test barrel says 00309 something so 309 Stainless anyone?? 304 test barrel had similar serial number.

It most likely means it came after SN 00308.

[Coastal Ron]

Pics taken this evening at the build site.

S/N on the test barrel says 00309 something so 309 Stainless anyone?? 304 test barrel had similar serial number.

I was looking at barrels serial numbers earlier and they seem to be in the mid-to-high 300 range right now, so maybe this is a fairly recent, but not really recent, barrel section?

Look at this image bocachicagal posted from today:
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=51332.0;attach=1964538;image

It has two barrel sections, one S/N00371 and the other S/N00382

I wouldn't think they would use serial numbers to denote material type - usually serial numbers are not meaningful.

[penguin44]

Is it me or does there seems to be a large dent in the side of sn6?

[Alvian@IDN]

Is it me or does there seems to be a large dent in the side of sn6?

Many of us had heard this 1000 times

Ofc as you might expect, no rupture on SN6 today because of that dents. SN5 also had dents

[kkattula]

Is it me or does there seems to be a large dent in the side of sn6?

Many of us had heard this 1000 times

Ofc as you might expect, no rupture on SN6 today because of that dents. SN5 also had dents

IIRC, it seems like the larger dents on recent SN have been near the square inspections hatches. Maybe due to material expansion or contraction from welding reinforcement around those holes.

SN8, with its round hatch a 304L steel, seems to have avoided that, so far.

[Vonbraun]

The welded hatches have always been source for dents because of the material contraction from heat concentration, but those are giving way to oval servicable hatches starting from SN8. Only the robotic welding can avoid the noticable shrinkage as the parameters can be fine tuned and kept.

[Ruct Cohle]

New bulkhead looks much better. Overwhelming majority of welds seem was made by robot. there is no deformation of conical shell. Considering other updates (welding stringers, fixing tiles), we can say that Starsip one step closer to orbit every day.

[DusanC]

Deformation of vessel is a consequence of mistakes in WPS and design and has nothing to do with robotic vs human welder.

[Thunderscreech]

Is there a realistic chance that the ambient deformation in the prototypes so far might be related to rings being welded (either as hoops or stacked together) at different times of the day with different temperatures that lead to some slight deformation at different temperatures in a way that might not happen in a climate controlled welding environment?

Like, if rings were always expanded to the same degree when welded because they're always 70F or something, would the same little dents show up?  As far as I know there aren't any real structural problems with them, just curious about the cosmetics I guess.

[alang]

I'm guessing that deformation is more likely to be visible under compression than tension.
Are there any views how much deformation under tension is acceptable apart from what is designed to be spread evenly under pressure? Are the welds likely to more or less brittle or plastic than the sheet stainless steel?

[FutureSpaceTourist]

https://twitter.com/neopork85/status/1295385086041493504

Ya'll, I am not convinced that the Starship forward flaps have changed much. They appear to be very similar to the last ones. The inner and outer edges are not parallel in my opinion. See illustration. Thoughts? Photo credit @RGVaerialphotos

[OTV Booster]

Is there a realistic chance that the ambient deformation in the prototypes so far might be related to rings being welded (either as hoops or stacked together) at different times of the day with different temperatures that lead to some slight deformation at different temperatures in a way that might not happen in a climate controlled welding environment?

Like, if rings were always expanded to the same degree when welded because they're always 70F or something, would the same little dents show up?  As far as I know there aren't any real structural problems with them, just curious about the cosmetics I guess.

If you look the data tags along with the ring SN is top and bottom dimensions. These used to be a raw number but they started to show up with a tag line of 20deg C. So these days they're measuring them and normalizing to 20C.

[OTV Booster]

Deformation of vessel is a consequence of mistakes in WPS and design and has nothing to do with robotic vs human welder.

All things being equal this is true. The welding is the great dis-equalizer. Too hot in one place means shrinkage over a larger area. Dead on robot welding does away with this.

[DusanC]

Deformation of vessel is a consequence of mistakes in WPS and design and has nothing to do with robotic vs human welder.

All things being equal this is true. The welding is the great dis-equalizer. Too hot in one place means shrinkage over a larger area. Dead on robot welding does away with this.

These are pressure vessel welds. If you have a welder that makes that much difference in heat input deformation would be the least of your concerns.
Pressure vessel welders for alloyed steels are masters of their trade, their welds look like machine made them and these Starship welds should be no problem for them, they weld dissimilar steels for steam pipelines at 25MPa and 800K everyday with less than 1% of RT rejects.

Also Starship ring segments were machine welded and still got distorted, they just welded them too fast to stop puckering but they induced more thermal stress.

[Ruct Cohle]

The main reason of deformation is  martensite to austenite transformation. Cold-work increases UTS and YTS. This makes the steel hard. But this is reason of appear martensite. Crystals of martensite have a larger volume than crystals of austenite with the same number of atom of metal. At 500 ° C +, martensite converts back to austenite and the steel shrinks. Welding temperature 1500 ° C + and there is a zone of temperature influence of the weld next to one. It doesn't matter what the ambient temperature is, whether a human or a robot is welding, etc. Steel will shrink.
In support of my words, I can cite links to Russian-language research article. http://www.rusnauka.com/2_ANR_2010/Phisica/1_57820.doc.htm

[Paul_G]

Deformation of vessel is a consequence of mistakes in WPS and design and has nothing to do with robotic vs human welder.

All things being equal this is true. The welding is the great dis-equalizer. Too hot in one place means shrinkage over a larger area. Dead on robot welding does away with this.

But aren't the dents caused when the segments are welded together in the mid bay (by hand) or when the hand weld the access port closed. I'm hoping that now that SN8 has a proper access hatch, these dents go away - even if they are just a cosmetic concern.

[Giggleplex7]

The main reason of deformation is  martensite to austenite transformation. Cold-work increases UTS and YTS. This makes the steel hard. But this is reason of appear martensite. Crystals of martensite have a larger volume than crystals of austenite with the same number of atom of metal. At 500 ° C +, martensite converts back to austenite and the steel shrinks. Welding temperature 1500 ° C + and there is a zone of temperature influence of the weld next to one. It doesn't matter what the ambient temperature is, whether a human or a robot is welding, etc. Steel will shrink.
In support of my words, I can cite links to Russian-language research article. http://www.rusnauka.com/2_ANR_2010/Phisica/1_57820.doc.htm

Aren't 300-series stainless steels austenitic? There shouldn't be any martensite forming as it should be in the austenite phase even at room temperature iirc.