It’s the power supply, dummy.

I do think that ultimately, absent something like anti-matter, or perhaps fusion, beamed power is the solution to opening the solar system. It could either push sails, or provide power for electric propulsion.

Are we really running out of it?

The problem lies in the type of sand we are using. Desert sand is largely useless to us. The overwhelming bulk of the sand we harvest goes to make concrete, and for that purpose, desert sand grains are the wrong shape. Eroded by wind rather than water, they are too smooth and rounded to lock together to form stable concrete.

We cannot extract 50 billion tonnes per year of any material without leading to massive impacts on the planet and thus on people’s lives – Pascal Peduzzi The sand we need is the more angular stuff found in the beds, banks, and floodplains of rivers, as well as in lakes and on the seashore. The demand for that material is so intense that around the world, riverbeds and beaches are being stripped bare, and farmlands and forests torn up to get at the precious grains. And in a growing number of countries, criminal gangs have moved in to the trade, spawning an often lethal black market in sand.

Ironically, as we discussed at the Space Settlement Summit last week, lunar regolith dust has ideal properties in that regard, which is why it’s such nasty stuff to deal with. Probably not worth the cost of importing it to earth, though.

[Update a while later]

For some reason, this reminds me of the old joke about what would happen if socialists took over the Sahara Desert.