Cargo Cost

A fun but no doubt inappropriate comparison with ocean container shipping

A Panamax cargo freighter is 52,500 deadweight tonnes, or 5000 twenty-foot-equivalent (TEU) intermodal shipping containers. A TEU container weighs 2.2 tonnes and can carry 28.2 tonnes.

Assume that 20% of the deadweight is fuel, crew, water, etc, leaving 42,000 metric tonnes for cargo in containers. That could be 5000 2.2 tonne containers with an average of 6.2 tonnes of cargo in each, or 1400 2.2 tonne containers with 27.8 tonnes of cargo in each. So, the net cargo capacity of a Panamax freighter might be around 40,000 metric tonnes.

If a container ship averages 20 knots, including dock operations, moorage, and maintenance, it will travel 8766*20 nautical miles per year, or 175,000 kilometers. times 40,000 metric tonnes, that is 7 billion tonne-km per year.

If the average shipping cost is 7 cents per tonne-km, that is 50 million dollars of shipping revenue per year.

Comparison with a Launch Loop

The Moon is 384,000 kilometers away. A 400 tonne-per-hour (gross weight) launch loop might expend 6 GW launching payload to that distance. Assuming 50% net weight to the lunar surface (including container and landing fuel), that is 1.8 million tonnes per year, and 700 billion tonne-kilometers per year. The incremental cost of launch is about $2/kg; the burdened cost might be $5/kg with debt service (WAG, mostly for the power plant, though space solar power might change that).

$5000/tonne divided by 384,000 kilometers is 1.3 cents per tonne-km, 20% of the cost of ocean shipping.

This is a ridiculous comparison, of course; the long journey to the Moon is "free" only after the expensive 2000 kilometer trip down the launch path, and the container ship delivering the container to the launch loop port.

But if you think that is ridiculous, with a little extra delta V, a 14 km/s exit speed launch loop can send vehicles into a gravity assist loop around Venus, then Jupiter, and into interstellar space. That would REALLY rack up the tonne-kilometers ...

Journeys to single destinations like the Moon only happen over a narrow window once a day. Gravity assist trajectories past Venus to Jupiter occur perhaps once per decade. The real opportunities will be to closer destinations, sending megatonnes to server sky and space solar power operations, or assembling fleets of Aldrin cyclers to Mars, and connecting with them frequently.