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Comment by westurner | Hacker News Reader

"This new idea could reduce steel’s carbon emissions by 90%" https://www.freethink.com/energy/decarbonizing-steel

Why is steel necessary for ships?

From "Plant-based epoxy enables recyclable carbon fiber" (2022) https://news.ycombinator.com/item?id=30138954 :

> And once it’s completed you have an insanely strong material that makes steel look weak and brittle. It’s reported to be as much as ten times stronger than steel, yet is lighter than fiberglass

Make it out of hemp aerogel and you could carry the boat.

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Carbon fiber materials have excellent tensile strengths, especially under steady-ish loads.

The front of an icebreaker's hull mostly faces compressive loads, with lots of shocks from hitting ice.

Try searching for "OceanGate Titan" if you want to read more about the performance of carbon fiber composites under large compressive loads in a marine environment.

Reading further from that thread about hemp on an article about carbon fiber: https://news.ycombinator.com/item?id=30147414

> Have you here contested claims that hemp - biocomposite with resin - has greater Tensile Strength and Compressive Strength than steel and aluminum (and carbon fiber with sustainable binder)?

"Stronger than steel" is a common materials science catchphrase, but it usually carries more than enough asterisks, daggers, and double-daggers to skewer practical applications.

The problem with carbon fiber and epoxy composites. Once it cracks, you cannot repair it, easily. It relies on a continuous composite structure. You can't patch it because that patchwork joint will just be a weak spot.

So you are talking about writing off tens of millions of dollars of a boat just because someone lost control and hit something too hard.

Steel is infinitely repairable, cut out the damaged section and weld in new steel.

Damage will and does occur to boats.

The other big drawback is that damaged composites attend to violently fall to pieces, where metal would bend.

Steel - it doesn't lose strength when you bend it a little. Most other materials suffer fatigue and fail when you bend them repeatedly. This makes steel ideal for many things.

You need mass to break ice.

Well there's always reinforced ice: https://en.m.wikipedia.org/wiki/Project_Habakkuk

;-)

> You need mass to break ice.

this is one of the narrow cases where pounds comes off the bench to say, "actually, you need weight"

(icebreakers slide/ride up on top of the ice and the weight of the ship breaks breaks it ice downward)

On Earth's surface, it's not like gravity is optional.

To get real technical about it, gravity is inconstant at constant altitudes when varying latitude and longitude.

9.8m/s^2 at sea level, and it decreases with altitude all the way out to Lagrangian points where the gravitational attraction of the sun (and other local masses) is equal to that of earth; but solar pressure presumably displaces objects at zero-gravity rest.

Gravity is 'optional' with quantum locking. Gravity is a weak force.

Gravity is maybe the least lossy form of potential energy storage?

A key feature of ice-breakers is that they operate at sea level, and in fact rely on gravity.

They are also surrounded by fluid that as ballast affects the density/volume/buoyancy/displacement(?) of the hull (and the inertia of the craft), which could be steel-plated [3d printed and/or pressure molded] biocomposite that lasts for spec years in seawater.

That's because pounds use force as a base unit, mass is kind of incorporated into it the notion of a pound, whereas the metric system generally handles the units for force and mass separately.

The imperial system actually does have a rather obscure unit called a slug which is equivalent to the kilogram (in terms of being purely a mass quantity) in the metric system, but since the pound already incorporates that term ( bundled together with the gravitational acceleration factor) it seldom sees action.

Would water be enough ballast for a cutter built with organic biocomposites that weather sea air and water?

A boat you could carry couldn’t break ice.

depends how hard you throw it

If you are a human you cannot break significant ice by throwing. Sure you can break 1cm of ice, but so any any other boat. We need ice breakers because there are cases where the ice is probably strong enough to support a the heaviest truck, but it doesn't quite have enough margin of safety on that probably to actually drive a truck so if you want to get through you need to send a boat through water.

you cannot break significant ice by throwing.

Don't skip boat throwing day!

+1. How do mass density of the craft and thrust limit the energy necessary to solve problem?

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