Leftovers #002 - New Job, Oceans, Space

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Holy cow it’s been a minute since I last wrote. Not an excuse but the big news is that earlier this year I left my cushy remote job at Lyft to join a local Vermont startup, Beta Technologies, that is building electric vertical takeoff and landing (eVTOL) airplanes! So you may see more about sustainable aviation and energy in this newsletter going forward. I wrote a post about why I joined Beta here.

My other fun news is that I started an AngelList syndicate to invest in Vermont startups. It’s called Minnow Ventures, if you’re interested in learning more please contact me directly. We’ve already completed two deals and aim to fund 4-6 companies per year going forward.

Ocean stuff

🎇 The old refrain is that we know more about the surface of the moon than we do about the bottom of the ocean. One reason for this is that we rely on slow ships and submarines to do ocean floor mapping, instead of aircraft. This is because using sound waves, or sonar, is the only reasonable way to do this. Light and radio waves don’t travel well through water. The problem with using an aircraft is that sonar doesn’t deal with transitions well, so when sonar from an aircraft hits the air/water barrier, the wave’s strength decreases by 1,000,000x. But researchers at Stanford are working on a new approach: they’ve found a way to fire a laser from a helicopter at the water’s surface, which heats the water and causes rapid expansion, which generates a soundwave. Another new device on the helicopter can detect the soundwave as it returns off the ocean floor and use it for mapping. The team is pretty sure they’ll be able to scale the system down so that it will fit on small drones for shallow river and coastal mapping.

📡 Another issue with radar not traveling well through water is that it’s hard to communicate. Messages sent through the ocean, such as from sensors on the ocean floor, have to rely on sonar too. Power is an issue here - it’s hard to change the batteries 10,000 feet down. Researchers at MIT have come up with a device called a broadband resonator that absorbs acoustic energy from noise in the ocean and converts it into power using piezoelectric ceramics (piezoelectricity is when you get an electric charge from applying stress to a solid material). Even cooler, they’ve found that they can also transmit data between these resonators, at about the same data rate as current acoustic modems. By attaching these resonators to temperature, acidity, and salinity sensors, they may be able to build an oceanwide measurement network, or tags for tracking sea creatures.

Space stuff

🔫 Getting to space is hard. Rocket fuel is the only stuff that’s energy dense enough to do the job, and until SpaceX came along rockets were not reusable. Even today, on SpaceX’s Falcon 9 still costs $2,700 per kilogram to put stuff into space. So there area few cool ideas for how to get stuff into space on the cheap. One that was recently tested was a big space gun, which has the more media-friendly name SpinLaunch. They use a big vacuum-sealed centrifuge to accelerate a rocket up to several thousands miles an hour before releasing it. Their 1/3 scale model (already bigger than the Statue of Liberty) just launched a 10 foot test projectile at 20% power. The full-size system should eventually be able to launch 200kg payloads into orbit. The’ve got a lot to figure out as building a giant vacuum-sealed thing spinning at hundreds of rpms is very hard, but very cool concept. (link)

🪂 This reminded me of a very wild concept from Neil Stephenson’s Seveneves novel. High recommend Stephenson if you haven’t come across him before. Anyway, this concept, called the Skyhook or tether, has already been tested and can work with materials that are available today. You have a big counterweight rotating in orbit above the earth, and a very long cable that reaches down into the lower atmosphere. Spacecraft would grab onto the end of the tether as it passed relatively slowly through the atmosphere, and then the rotational velocity of the skyhook would fling the spacecraft into space towards its destination. The tip of the tether would still be moving super fast, but not nearly as fast as we have to accelerate a rocket to escape earth’s gravity today. The tether can also be used to catch incoming spacecraft and return them to earth, and this has the added value of helping add rotational energy to the tether, so we could save tons of fuel costs. We could eventually have a network of Skyhooks throughout the solar system to fling spaceships around. This is hard to visualize so check out this awesome video by Kurzgesagt: Link (highly recommend all their stuff)

🌳 In the world of satellites, there’s a Japanese firm that is playing around with the idea of making satellites out of wood! Wood is great for few reasons: radio waves can penetrate it (so antennas could be placed inside satellites), and wood would burn up completely on reentry, making disposal cleaner. The same firm is also considering making the world’s tallest wooden skyscraper in Tokyo. (link)

🌌 Finally, here’s a cool view of earth’s rotation when you keep the keep the night sky fixed (link)

Finale

🙏 If you enjoyed this, how about forwarding to a friend or two? I aim to make this one of the few newsletters you truly enjoy opening every week. And if you find anything interesting you think I should include next week, let me know!