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Comment by saalweachter | Hacker News Reader

Do we have anything rated for a few millennia of interstellar radiation besides etched gold plates?

Microsoft's project Silica [0] may hopefully provide really long term, large capacity archive grade storage on earth. I wonder what effects interstellar radiation has on them.

[0] https://www.theverge.com/2019/11/4/20942040/microsoft-projec...

Glass is pretty inert, full stop. It would depend on the voxel size but I imagine as long as you have more than a few hundered atoms per voxel/bit you will have survivability on the order of millenia, even in high radiation environments. Someone would have to do the nuclear cross section calculations to get a real bit error rate but glass is very tough stuff.

Glass: https://news.microsoft.com/innovation-stories/ignite-project..., https://en.wikipedia.org/wiki/5D_optical_data_storage

I think millipede memory[0] could have managed that, too bad the technology got shelved.

[0]: https://en.wikipedia.org/wiki/Millipede_memory

whats wrong with etched gold disks?

I wonder if that's actually feasible for this application.

Microdots managed about 32MiB / square centimeter (from the "you could fit the Bible 50 times in a square inch") measure. That's a completely arbitrary density to achieve, since it was photographs which were enlarged and shrunk, and you could hypothetically use any encoding for your gold etchings, and it also leaves out the question of "how fine can you etch gold plates while still having the engraving be 'robust'".

But in any case, that gives you a target area of ~325 square meters for a 100TiB archive.

That's a lot, but not like a crazy obviously impossible number like a million square km or something.

Assuming you can cut the etching down to 1m squares and stack them on top of one another that should be no problem at all. Assuming each layer is 1.2mm thick (same as a CD) that's a volume of 1m x 1m x .390m, it would fit easily in a payload fairing of any rocket that can get it into orbit.

The volume isn't a real problem, but nearly half a cubic meter of gold should also have a mass of ~7500 kilograms. You're also looking at a cost of ~$350 million, US.

(Which isn't necessarily impossible, but still a lot, especially for an interstellar probe.)

7.5 metric tons is well within the weight limit for a Falcon 9, so add about $57m for the launch costs for a total project cost of probably around $500m.

That puts it in the realm of the Voyager probes for total cost.

7.5 metric tons is also over ten times the mass of each Voyager probe.

Thank SpaceX for slashing launch costs and me for not factoring in much of a second stage to boost that mass out of orbit.

But I was also extremely generous with the thickness in the first post. In real life they would almost certainly be closer to .05mm than 1.2mm, and probably not made out of solid gold.

The point was to show that even with some rather pessimistic assumptions the project was within human scale and even had some precedent.

Yeah, it's all within the realm of possibility, with too many unknowns (eg, what is a realistic information density) to really easily say how easy or hard it is.

Re: Falcon 9's, Voyager was lifted on a Titan IIIE, which had a LEO payload of 15,300 kg, compared to 22,800 kg for the Falcon 9 to LEO. Assuming Voyager was near the capacity of what could be ejected from the Solar System by a Titan IIIE, you'd need to send up ~7 Falcon 9's to Voltron together in orbit.

I would argue that at this point, actually building Voltron might be more wortwhile.

Then they could be double-sided. And aluminum is cheap ... just hope it doesnt hit a rock

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