[QUOTE=Uncwilly;600706]...SpaceX went with stainless steel (vs) for Starship for strength at various temps (both cryogenic and heated). The external tank for the space shuttle, the center tank for SLS, and the Falcon 9 use a very lightweight version of Aluminum-Lithium alloy...[/QUOTE]

My eldest brother was in the USAF during the Vietnam War era. After his return, he often mentioned Titanium as the lightweight metal of choice at the time. It is not an alloy. I suspect the technology to create an alloy like Al-Li did not exist at the time.

BTW, the large burnt-orange section of the SLS, is that a single stage, or two?

By analogy to 1D polyaramids, melting point would be >500C. Chemical 2D bonding may increase that.
This stuff might make a great ablative heat shield. Or load bearing thermal insulation system for moderate heat to cryogenic, especially if it self orients when foamed and can be coaxed into bonding fractally.
It took some digging, but I finally found a URL with quantitative values for properties, not ratios to other materials.

(Paywalled Nature article, [URL="https://www.nature.com/articles/s41586-021-04296-3"]abstract[/URL] freely available gives ~13. GPa 2d elastic modulus, ~490. MPa yield strength. I estimate density ~1.3 g/cc from steel/6.)

Comparing strength to steel is very problematic, as steels have such a wide range of composition and properties. Contrast for example [URL="https://material-properties.org/what-is-strength-of-carbon-steel-definition/"]cheap[/URL] structural steel with [URL="https://material-properties.org/tool-steel-density-strength-hardness-melting-point/"]tool[/URL] [URL="https://www.techsteel.net/alloy/tool-steel/h11"]steels[/URL] (~500MPa vs. 1.8GPa ultimate tensile strength, ~250MPa vs ~1.5GPa yield strength). Densities vary a bit too. Elastic modulus of steel varies a bit, but typically ~200. GPa, ~16. times higher than for the new 2D plastic.

The 2DPA1 plastic or future formulations to follow might be interesting as a component in a composite face sheet in honeycomb constructions:

thin outer coat of plastic as corrosion inhibitor, strain hardened metal foil, plastic spacer, second metal foil, thin coat as corrosion inhibitor composing one face sheet of a honeycomb layup, to get lots of face sheet buckling resistance and strength at low weight.
Honeycomb materials fail in a variety of ways:
face sheet buckling
sheet/core bond delamination
core crush
corrosion
compressive or tensile yield
(more?)
In high performance high weight penalty applications such as aerospace, one could even consider a compound honeycomb, where the plastic spacer in the sandwich described above is a low core height honeycomb geometry.

This may be like the discovery of the first high temperature superconductor. Decades later we still don't have practical room temperature superconductors, but the floodgates opened on HTSC research and considerable [URL="https://en.wikipedia.org/wiki/High-temperature_superconductivity"]advance[/URL] has been achieved.
Now imagine long needle shaped, thick-walled relative to bore diameter, pressure vessels made of steel or other high strength material, corrosion proofed with something impervious to 270+ MPa of CH[SUB]4[/SUB] and H[SUB]2[/SUB]S (superconductive to +14C), with copper terminations/connections, in an ice bath, or in [URL="https://oceanexplorer.noaa.gov/facts/temp-vary.html"]cold deep ocean[/URL] or deep [URL="https://seatemperature.info/great-lakes-water-temperature.html"]great-lakes [/URL]water, for long distance power transmission at low loss.

[QUOTE=storm5510;600727]he often mentioned Titanium as the lightweight metal of choice at the time. It is not an alloy. I suspect the technology to create an alloy like Al-Li did not exist at the time.[/QUOTE]Titanium is a chemical element. It is commonly used in [URL="https://www.refractorymetal.org/how-is-titanium-used-in-aerospaceaeronautics-applications/"]alloy[/URL] form, such as [URL="https://continentalsteel.com/blog/aerospace-titanium/"]Ti6Al4V[/URL]. Many commercially useful metals have useful strength properties in alloy form and are quite weak in pure form. Aluminum is an example; I've used fairly pure 99.5% aluminum or purer in small wire form as a metal deformable gasket between stainless steel flanges, far more economical than using gold wire and equally effective up to ~150C or higher, 10[SUP]-11[/SUP] Torr vacuum system internal pressure, 1 atmosphere external. Aluminum "Mott" seals are used in very high pressure service such as the oil industry. Under the high localized stresses when crushed between flanges, aluminum wire will cold weld and seal if simply crossed. Iron is another example; [URL="https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.1967.0004"]pure iron[/URL] is weak, while alloyed with a bit of carbon or other elements can be quite strong.

[QUOTE=kriesel;600728]Many commercially useful metals have useful strength properties in alloy form and are quite weak in pure form. Aluminum is an example.[/QUOTE]Tungsten is another. ure tungsten is as malleable as copper. Add <= 1% oxygen, as is found in almost all commercial samples, and at room temperature it is about as brittle as glass. Heat commercial W red-hot and it is also as brittle. A little below that temperature and it is again as easily worked as is Cu. One of my (almost) completely useless skills is to know how to heat tungsten wire so that it can be bent into furnace-heating elements. People either have the skill or they do not. The lab glass-blowing chappie said it was almost impossible to teach it.

[QUOTE=storm5510;600727]BTW, the large burnt-orange section of the SLS, is that a single stage, or two?[/QUOTE]With the Shuttle that was just a pair of tanks. With SLS it is complicated. Block 1 will have a the tanks and an adapter to the stage above that. The adapter cone is orange, but the second stage is white. The later Block 1B will have a larger diameter second stage that is orange (the colour of the insulation). Block 2 is the same as Block 1B, except the boosters are upgraded.

Boeing's Starliner capsule successfully launched at 6:54 EDT (2254 GMT) May 19.

Starliner is scheduled to dock with the ISS around 7 p.m. EDT (2300 GMT) on Friday, May 20.

[QUOTE=Dr Sardonicus;606140]Boeing's Starliner capsule successfully launched at 6:54 EDT (2254 GMT) May 19.[/QUOTE]

Yup... I watched it live.

Boeing *needs* this to work. Let us hope they figured out their software issues.

Separately... [URL="https://www.youtube.com/watch?v=3Ux6B3bvO0w"]Musk is working a bit deeper...[/URL]

Don't celebrate too quickly.
[url]https://twitter.com/StephenClark1/status/1527457462240137229[/url]

[QUOTE=Uncwilly;606143]Don't celebrate too quickly.
[url]https://twitter.com/StephenClark1/status/1527457462240137229[/url][/QUOTE]
So, the best Boeing can deliver given enough time and money, is a product where two key systems fail on the qualifying flight. That low ceiling should preclude human-rating, IMO. I'd like to think the ability to produce a 100% functional product needs to be proven. But then again, it is a gov't project, so who knows what and how the key capabilities and performance benchmarks are defined in the contract. Maybe avoidance of RUD prior to docking is enough to pass. Hope there are reserve parachutes aboard for the return trip.

Frustrating that Boeing has fallen so far.

[QUOTE=sdbardwick;606148]Frustrating that Boeing has fallen so far.[/QUOTE]

Boeing is used to "cost plus" contracts for its rocketry work.

Politicians love these because the contractor makes sure to spread the work across all the various states so everyone can point to the employment opportunities provided.

[URL="https://en.wikipedia.org/wiki/Space_Launch_System"]SLS[/URL] is a perfect example of this. In the false economy of these types of projects, wasted money is actually a good thing. Actually getting the job done is secondary.

[QUOTE=chalsall;606176][URL="https://en.wikipedia.org/wiki/Space_Launch_System"]SLS[/URL] is a perfect example of this. In the false economy of these types of projects, wasted money is actually a good thing. Actually getting the job done is secondary.[/QUOTE]SLS is a jobs program designed to look like a space program. It is doing its job perfectly.

[QUOTE=chalsall;606176]Boeing is used to "cost plus" contracts for its rocketry work.
<snip>[/QUOTE]Boeing's contract for this project [Starliner] is fixed-price. The company has lost hundreds of millions of dollars due to the delays in meeting objectives.

Even so, I haven't heard of any Boeing execs being reduced to picking crusts out of the gutter...