Asteroids, Asteroids, How Many Are There to Mine?

Radhika Dirks Uncategorized Leave a Comment


“You recognize true innovation because doubt, fear and excitement are part of its entourage. It should make you a tad-bit uncomfortable, skeptical, and at the same time raise your hopes.”

So reads a line from my post on innovation Red Queen of Technology, written just a few days ago. And Planetary Resources, a startup backed by some big shots including Google’s Page and Schmidt, X-Prize’s Diamandis, and even James Cameron of Titanic fame (alright, I could have picked a different movie, but I wanted to evoke hope, excitement and skepticism – in that order), couldn’t fit the bill better. Their goal is freaking awesome: to cost-effectively mine asteroids.

In order for their goals to make sense, Planetary Resources needs sufficient resource-rich asteroids that are close to Earth. The resources they are targeting are the shiny, high-dollar value, platinum-group metals – to make the adventure profitable –  and  water, which by breaking down to liquid oxygen and liquid hydrogen can propel the rockets.  Sounds awesomer and awesomer.

But it appears, Elvis might be jeopardizing their plans. Astrophysicist Martin Elvis at the Harvard-Smithsonian Center in Cambridge, that is. He recently formulated the Elvis Equation to answer how many commercially minable  asteroids are there, close to Earth.

The answer turns out to be a disappointingly low 10. Just 10 accessible asteroids are predicted to have ores rich enough in platinum group metals. While Elvis is the first to point out that a better formalism is needed to really pin down these numbers, his approach mimics the super cool Drake equation used to estimate the number of advanced civilizations in the galaxy. Similar to a top-down market size estimation, Elvis starts out with the (known) number of near Earth objects big enough to make any mining venture make sense. Then he calculates the odds that an asteroid is ore bearing using a series of probabilities for whether it is:

  1. A resource bearing type? Probability = 4%
  2. Sufficiently rich in the resource? Probability = 50%
  3. In an accessible orbit ? Probability = 2.5%
  4. Profitable to extract resources from? To simplify, he assumes this Probability = 100%.

The dominating reason for the dramatically small number of minable asteroids is because there are simply not enough of them that are accessible (bullet 3 above) – only 2.5%   out of ~20,000. But there is hope! Accessibility is determined primarily by the amount of energy transfer needed to go out to the asteroid and return with the ore. Basically, it is the energy required to get in and out of the asteroid’s orbit and is controlled by delta-v, the change in velocity needed to transfer  between orbits. We would like to minimize this – because the cost of energy is high – and Elvis chooses a a rather tight constraint of delta-v = 4.5 km s-1. But – and here is the hope – accessibility is a highly non-linear function of delta-v; if we can tolerate increasing delta-v to 5.7 km s-1, we can get a whooping 1000% accessibility improvement!

The second reason is that, according to our current models, there aren’t enough resource bearing types of asteroids (bullet 1) – just 4 %. Since this is what Nature gave us to play with, there is nothing much we can do about this, but better data and models might help.

Elvis’s approach is quite clever, rather admirable, and extremely useful. But really, the accessibility cost needs to be compared with the commercial value of the ore available. Elvis does account for this while calculating a size threshold to determine whether the ore available will cover mission costs. But cost needs to be an indirect dependent parameter in the number equation for it to make more sense. The minimum asteroid size needed, by the way, is a 100-meter diameter asteroid, which can bring in about $1.2 billion at current platinum prices.

Elvis’s approach serves as a great start. With better data and a bit more sophisticated model, we might get numbers that show asteroid mining makes commercial sense. Perhaps the $10 million telescopes Planetary Resources plans to launch soon can give us better data for a better estimation.

Go Planetary Resources!

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