Shotgun mini-probes for asteroid mining

I've often wondered at the vast mineral richness of space, possibly thanks to playing Elite back in my "formative years".

A key challenge faced by modern asteroid miners, like Planetary Resources, is just how to discover and classify substantial mineral-bearing rocks in the vast relative emptiness of space.

The current approach uses a combination of radiometric scans to discover the larger possible candidates then sending specifically targeted probes to the potential candidate.

This approach - while thorough and accurate - is nonetheless quite painfully slow and due to the distances involved relies on objects being visible to our scanners which requires expensive highly sensitive equipment.

So, what's my bright idea?

If the goal was to be faster and cheaper at the expense of accuracy, one could adopt a "shotgun" or "scattershot" approach to sending out probes.

The process is simple: shower the entire asteroid belt with tiny devices only a couple of millimeters across. Make them sticky on the outside and once they stick to something start pulsing an LED. Whether it's a chemical reagent in the sticky pads or something as basic as the resistance between them, based on the modulation of the LED pulses the underlying material can be guessed at.

As for power? A tiny solar panel coupled with a capacitor could keep the LED pulsing indefinitely.

Even at low power emissions, I assume it's quite feasible that Earth-based radio telescopes which are more at home spotting galaxies millions of light years away could easily pinpoint, track and catalogue found objects.

The issue of spectral noise in astronomical surveys could easily be mitigated by ensuring the LEDs occupy a specific bandwidth and also by engineering a reasonable end-of-life into the probes.

Given the simplicity, these should be incredibly cheap to manufacture. If only a couple of millimeters in size, about 500k would fit in 1m^2. Given the volume of space to map, the more we can deploy the better.

Deployment is another issue.

How will we get them there?

On a big rocket. More specifically, a rocket that is capable of sending a couple of tonnes on an intercept path with the asteroid belt between Mars and Jupiter.

The rocket doesn't have to make the full journey of course. In fact once it's reached an optimum trajectory, a mechanism (likely consisting of compressed gas releasing in an ordered pattern) could eject the tiny microprobes in a spreading swarm that - given the correct pattern of ejection - could occupy the full diameter of the belt.

Then we just sit back and wait for the lights to go on.

How much would this cost?

Probes that are 2x2mm in volume could be squeezed together into a crate at up to 500,000 per square meter. Of course they are coated by sticky gel and will need to be separated by vanes that are coated to resist the adhesion (with a substance like liquiglide), so we'll say the probes need 3x3 mm. Also, the release mechanism will likely eat up space and is the biggest engineering challenge for a project like this, so I'll leave that one as a big question mark for now.

Let's just say for now that we'd be able to pack 300,000 probes per m^2 and revise the estimate later when some actual engineering gets done. Keep in mind this is just a rough outline of an idea.

Per unit, the pulsing LED with switching and modulation circuitry should cost mere cents. Let's say 50 cents per probe to be conservative. The sticky conductive gel should be easy to source and shouldn't cost more than a few cents per unit, lets say 10c per unit to keep the calculations nice and round. About 10c for the tiny amount of plastic used to house the components and we're at 70c per unit. The liquiglide coated plastic sheets keeping everything separate shouldn't cost more than a few cents per unit either, let's say 30c. Conveniently, these little mini-probes might only cost about $1 each or $300,000 per cubic meter.

R&D-wise, the actual circuitry and design would be a college-level electronics and physics project. Tweaking the LED modulator to represent the properties of the surface it's stuck to might be a Honors-level project (resistance and capacitance may both be represented by varying the pulse-width or something). Fabricating lab prototypes and testing them on terrestrial materials should be a walk in the park. Expect to pay a couple of hundred thousand dollars at this stage for time and materials.

I envision that the most difficult challenge would be in packing and release mechanisms. Just how will the probes be packed most efficiently then be released into space to form the trailing swarm necessary to encompass the entire belt, or at least a large portion of it? This could occupy several PhD-level physicists for some time and would require repeated testing as it's the most mission-critical feature. Failure to deploy correctly could result in blobs of probes heading in the wrong direction & stuck together in a big mess. I'd say it's worth $6 million and a year or two of testing just to get this part right as the insights from this process would be recovered in future missions (each subsequent mission painting a clearer picture of the belt).

The software needed to process and track the probes once they start emitting light shouldn't be too difficult. If each modulated its signal with a unique ID code it should be simple to track individual units and the properties of the materials they have found. Basic trigonometry could triangulate their position and velocity vectors. Once the raw data is easily available through an accessible API, developers worldwide could write their own algorithms for various tasks, like detecting anomalous movement which could indicate the presence of non-belt objects and their properties. I'd imagine the first iteration to be somewhere in the realm of 1 year of a senior software developer with even a slight physics background, or about 100k, plus let's give the senior some help in the form of a couple of junior-level developers and make it $200k total for the software.

Run-time at terrestrial radio telescopes can be hired on an hourly basis, so consultation with astronomers would be necessary to devise the best algorithms to scan the belt with a large enough baseline for trigonometric measurements, identify the probes, and feed this information into the software. I guess this could cost anywhere up to $2 million, but I'd need to ask an astronomer to be sure.

With all the ongoing costs, there needs to be a business model for the data. Who needs it, and how much are they willing to pay to access it, and under what terms? Will the API simply be a subscriber service, with some free use allowed to encourage innovative uses of the data? Developing a business model could take time and money, perhaps up to $1m, maybe more but it should be able to bootstrap itself somewhat.

Finally, the launch... I have no idea what that will cost but I'd imagine reaching a point of release for the spreader capsule might cost in the realm of $500 million due to the sheer volume of propellant required. I'll send some emails out to respective space launch companies to ask them what their standard rates are for a mission to the asteroid belt :)

Significant cost reductions could therefore be envisioned by simply targeting near Earth asteroids instead, at least in the short term.

In total to get this thing off the ground I'd say we'd need about $10 million plus a 20% contingency, so let's say $12 million, on top of the launch costs. For each subsequent mission the probes and their release capsule should cost between $1 and $2 million per mission.

In return, we may get a fuller picture of the asteroids in our solar system than our current missions are able to provide from near-Earth orbits.

I'd say it's worth a shot.

Todo list

1. Work out how to pack hundreds of thousands of mini-probes around an accelerant that can spray them in an arc on a collision course with an asteroid belt.
2. Work out a launch trajectory to deliver the payload to the release point.
3. Work out the details of the circuitry involved in switching on the LED pulses, modulating the pulses and encoding information about the surface the probe stuck to.
4. Find someone with money who's willing to fund this.