Can We Throw Satellites to Space? - SpinLaunch

This is another overly long video that is filled with a massive amount of science in all sorts of disciplines: physics, material science, chemistry, engineering, mechanics.

The video sees the Real Engineering host, Brian McManus, visit SpinLaunch's centrifuge being built to launch satellites into space primarily via kinetic energy rather than through rocket fuel combustion...which sounds totally bonkers but might work out.

One of the main technologies here involves a carbon fiber-reinforced polymer tether. At 3:00 that concept is explored with a laminated carbon fiber reinforcement mock-up of the thickness that they need the tether to be to hold the millions of pounds of force that would be necessary.

Then - 8:00 - they look at the need to spin up that tether in a vacuum chamber so that it doesn't melt the carbon fiber from the friction due to air resistance. They also describe how truly low pressure vacuum chamber pumps work and why the SpinLaunch people don't need a vacuum chamber with quite that low a pressure. The idea of outgassing from the metallic parts - 10:25 - was amazing to me. It makes sense to me that there would be small amounts of oxygen gas 'dissolved' in any steel parts, but I had certainly never thought about it before. It's an equilibrium problem, I guess, as oxygen is removed from the atmosphere around the part.

At 16:20 they take a look at the challenges of opening a low pressure chamber at near vacuum to the atmospheric pressure outside without destroying the chamber inside when the air rushes in. They've used a pairing of mylar layers that are broken through and two incredibly quick closing doors.

From 21:30 they explain how they address and minimize vibrations - especially once the payload is let go, leaving a highly unbalanced weight on the arm.

The next section - from 26:45 - they look into the ballistic coefficient of the projectile and why a heavier vehicle might be better for their launch process - something that is very well against the traditional method of launch's goals. With rockets, lighter is better. With the SpinLaunch, heavier and denser is somewhat better because it allows the projectile to gain more momentum without corresponding drag and heating due to friction with the lower atmosphere.

The whole process is fascinating, and I'm hopeful that it turns out to be feasible because I would love to see a full scale SpinLaunch facility built and functioning - for the science and novelty if for nothing else.

Inside the world's largest crystal 'cave' – BBC REEL

But wait...

This is NOT another post about Naica's crystal cave in Mexico. I've already posted a few of those.

This post is about the Pulpí Geode, supposedly the world's largest geode, found near the town of Pulpí, Spain.

The crystals are - like those in Naica's cave - gypsum, and they're admittedly not as large as those in Naica's cave. In the above video, they refer to the Naica crystals as being up to 15m in length and those in the Pulpí Geode as being up to 2m in length. In the video, however, they state - without much explanation - that the Pulpí Geode is a geode - a cavity in rock completely covered with crystals - and the Naica cave as not a geode. 

I don't know if that means the Naica cave just has some un-covered surfaces or what, but the video above doesn't go into that detail, admittedly.

But this cave is available for people to walk through - for now, anyway - whereas Naica is flooded again. You just need to get to Pulpí.

Check out more about the Pulpí Geode...

• Spain's crystal cave, the giant gypsum geode of Pulpí
• These human-sized crystals formed in especially strange ways (requires registration - but you can use a made-up email address as of 8/14/22)
• The world's largest crystal cave

Young Inventor Makes Bricks From Plastic Trash | World Wide Waste

"So far her factory has recycled 50 metric tons of waste this year.

"But Nairobi produces six times that amount of plastic trash every single day."

...

"So I cannot say this is 'the' solution in terms of like it has the biggest impact and all that stuff, no. Does it have an impact? Yes."

...

Start playing my broken record - we make too much plastic / polymer waste. It's bad for us, for the environment, for the planet.

But at least some people are doing something to reuse the plastics that we already have.

Today's video shows a young woman in Nairobi, Kenya making paving bricks from recycled plastics and sand. 

Is this 'the' solution? Probably not.

Does it have an impact? Yes.

Only A Few Families Know The Secret To Making This Perfect Mirror | Still Standing

Every time I watch any of the Business Insider videos (and I know I've been posting a lot of them of late - blame the YouTube algorithm for recommending them and BI for making them fascinating), I'm tempted to buy one of the item. It's not that I need an aranmula kannadi in any way. It's just that I find the process fascinating and want to reward the craftspeople who still make things by hand.

There's not a ton of material science here, but it does show a far less industrial version of casting an alloy. 

Interestingly they don't seem to mix the alloy components (mainly tin and copper but a trade secret as to the proportions and actual ingredients) other than in turning the molten metal upside down into the mold. I would be very curious to see if the mirror had a homogeneous composition throughout. 

It's also fascinating to me to think of this process being developed bit by bit over centuries. Small steps like the cooling of the mold with mud, the covering of the mold in carbon to fill in microscopic pores, and onward must have been done at some point by trial and error and kept in the process when they worked - assumedly discarded from the process when they didn't work - and I wonder how much of the process is like cooking a turkey.