NASA tests shrinking metals to help it find more exoplanets NASA is exploring the properties of a metal alloy that shrinks as it is heated, as boffins in its Astrophysics Division think it may be needed if the planned Habitable Worlds Observatory (HWO) is to succeed. Readers doubtless know that metals expand when heated. As explained in a NASA blog post that’s a problem for space …
The ghost of Brian Aldiss would like a quiet word about going the all-natural route to arboreal orbiters.
Can somebody shush those norn? No, Skuld, Yggdrasil isn't in orbit, that's why. Yes, yes, you can climb it to reach the heavens. Look, I think we may be getting off topic here, just go and stop Ratatoskr burying another asteroid, please.
and how about
https://www.amazon.co.uk/Crucible-Time-John-Brunner-ebook/dp/B007PR3224?crid=1TJX3H6PD41XY&dib=eyJ2IjoiMSJ9.g1CBtj6FRNEJi4tMs5hRTxJbr0erWXdJwRi8CnAdPvk.WhZyMQozwpkbah1Y0CwG_NT8HlSD1G9YPpDb3XZ_OE4&dib_tag=se&keywords=The+Crucible+Of+Time+-+John+Brunner&qid=1751527538&sprefix=the+crucible+of+time+-+john+brunner%2Caps%2C79&sr=8-1
Yeah, I was surprised to see the pendulum wall clock here speed up some during this heatwave that is so hot French folks are cooking eggs unassisted, in 30 minutes flat, in schoolyards (80+ degrees C), breaking the previous record from 2022 when it took 2 hours on a park bench (with T = 57 C) ... (good thing they closed the Eiffel Tower!)
It seems the wooden pendulum rod helps a bit. Interestingly, "As wood experiences an increase in temperature, it may experience some thermal expansion, but there is also a loss of [Moisture Content ...] the net result is shrinkage", which would explain the slight speedup.
The Allvar name looks to be a riff on Invar, an alloy with an unusually low, but still slightly positive coefficient of thermal expansion that has been around since the 19th century. Often used in situations where making something temperature insensitive is important. Though not as important as in an exoplanet hunting space telescope.
The compression ratio is the (usually) fixed ratio between the maximum and minimum volume of a combustion chamber. Dimensionally stable components will have little to no effect on compression ratio. I was thinking more about rod-bolt stretch, crank thrust bearing preloads, and various bits in the valve train, all of which have a big say in the maximum RPM of a given motor (you don't want the thing rattling itself into oblivion ...).
Piston rings are multi-function beasties. They serve to transfer heat from the piston to the cylinder, to keep the proper oil film between piston and cylinder (both for lubrication, and scraping excess to prevent oil consumption by burning), and to minimize blow-by.
As such, they need to change size as the engine cycles through heat ranges in order to minimize over-all wear and tear. There is no one-size-fits-all for a typical start/run/stop cycle, rather they change dynamically during the run.
Also, I seriously doubt that a titanium alloy such as ALLVAR would have the mechanical characteristics required of a piston ring.
Edit: Also, I just discovered that ALLVAR's thermal transfer capability is quite low (it is a titanium alloy, after all ... ), and its maximum operating temperature is only 100C (212F), making it completely unsuitable for most internal engine components. See this spec sheet:
https://allvaralloys.com/what-is-negative-thermal-expansion/
This is cute. We spent hundreds of thousands of years learning how to sharpen rocks, then a few short decades later we’re inventing metal that shrinks when heated so we can squint at distant planets through billion-to-one contrast ratios… all just to realise we’re still trapped on a glorified space prison with no exit strategy.
Even if we do manage to escape Terra, where exactly are we going? Another rock with a thinner atmosphere and no coffee? And let’s be honest: if we ever get close to leaving, the people in charge will simply bolt the hatch and remind us that the shareholders prefer us firmly grounded.
Still, neat washers.
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