Last week I had an odd conversation… why shouldn’t you just melt ice instead of simply breaking it.

The way a typical icebreaker works is that it rides up on top of the ice then uses its weight to bear down on the underlying ice to shatter it. What this does is to create lanes for other, less armored, ships to pass.

His idea was to simply melt the ice.

So, let us look at this problem.

For a fuel source I’m going to assume gasoline. It’s not critically important as you’ll see, but I chose it because most of us have experience with it. Gas has an energy content of 35.8MJ/l. There are similar liquid fuels that are similar as well.

Normally, when using a fuel, you have energy loss when converting that to useful work. Let’s say that you have no such issues; 100% of the chemical energy will be used to melt ice.

Further, let’s assume that we have ice at 0ºC. The funny thing about ice is that it has an abnormally high enthalpy of fusion — the amount of energy used to melt or reform ice. It happens to be 333.5 KJ/l.

Basically, if you do the math of 35.8/333.5 you get 107.3. A liter of gasoline can melt 107.3 liters of water ice. (Ok, almost, the density of water ice is slightly less than liquid water by ~ 4%.) I’m going to round this to 100, we’ve already made plenty of allowances with the 100% efficiency… but you can add 7% if you really want.

Now let’s consider an ice-melting ship. It needs to melt a path at least as wide as itself, otherwise, it won’t move forward.

So, you have a 100:1 ratio of melting ice to fuel.

If you have an ice sheet 1m thick, you would need 1cm worth of fuel to melt a ship’s-length area of ice. This, of course, assumes a perfectly rectangular ship that needs no fuel to propel itself.

If the ship is 100m long, roughly the length of a football field, that had 10m of draft, you could melt 100 (length of ship) * 10 (depth of ship in meters) * 100 (m/cm of fuel ice ratio) m of ice.

With 100,000l of fuel, you could only melt 100km of ice. That’s 100l/km to do the work, or 0.024 mpg.

That is why just just break the ice.

And this is the best case scenario with no losses, no propulsion, no friction, nothing. Hell, this doesn’t even include a ship that holds the fuel or melting apperatus.