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nhnifong

How would you design a satellite to last 5 billion years?

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Let's say we wanted to leave a record of ourselves that would outlast the sun, recording events periodically in the solar system as it went.

The design criteria you must try to meet are:

The satellite must contain 100 petabytes of cold storage, containing compressed records of human history.

The satellite must contain 15 additional petabytes of writable memory used for taking a yearly picture of the sun, picture of the earth, and other measurements.

The data must be recoverable with as much accuracy as possible by a human-level civilization 5 billion years from now, after the death of the sun.

How would you go about designing such an impossible thing? What compromises would you make?

How heavy would it have to be? what would you use as a power source?

Correction: petabytes. That's what I did my math based on. WHoops!

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How I would do it:

100 petabytes of cold storage will fit on 16666 Holographic Versitile Disks which, if they have a mass of around 10 grams each, is a mass of 166.6 kg. This cold storage will also be redundantly stored in about 50 kg of DNA.

The additional 15 exabytes of writable storage will be triply redundantly stored on HVD discs, 15 kg of radiation hardened flash memory chips, and encoded in DNA.

The total memory weight is 363 kilograms, it will all be placed inside a 200 kg shield to protect it from radiation and cosmic rays. Error checking systems and supporting machinery may total 100 more kg.

For power, I'd use an extremely low power RTG with Uranium-238. no attitude needs to be maintained, and no transmissions need to be made. The spacecraft is expected to be physically recovered. The only thing drawing power is the sensors once a year and the error correction mechanisms.

I'd put this is a highly inclined circular orbit around the sun with a periapsis of about 2 AU.

Edited by nhnifong

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As Moon is also a satellite, I would certainly situate it on the near side of the Moon, perfect for taking pictures too. As for the hardware, there would have to be intelligent or at least semi-intelligent robots capable of self repair taking care of it. Or magic.

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Let's say we wanted to leave a record of ourselves that would outlast the sun, recording events periodically in the solar system as it went.

The design criteria you must try to meet are:

The satellite must contain 100 exabytes of cold storage, containing compressed records of human history.

Umm... that's about 10^8 terabytes. That's a lot of hard drives, not to mention the fact that all of human history wouldn't take up that much space, unless you want every single video, photo, painting, other media ever made ever, and even then I doubt it's that much.

The satellite must contain 15 additional exabytes of writable memory used for taking a yearly picture of the sun, picture of the earth, and other measurements.

The data must be recoverable with as much accuracy as possible by a human-level civilization 5 billion years from now, after the death of the sun.

I don't think you realize just how big an exabyte is. 15 exabytes is way more than you need to take pictures of the Sun, and other bodies.

How would you go about designing such an impossible thing? What compromises would you make?

How heavy would it have to be? what would you use as a power source?

I'm pretty sure there isn't a power system out there that is reliable enough, and will last long enough to be used for five billion years with out human assistance.

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Data storage should be in the form of optical disc. Assuming they aren't physically damaged, they'll outlast hard disk drives and are write only. I think the safest option would be to place it in Lunar orbit where it can observe the earth and sun without the problem of earth's exosphere. Definitely ion propulsion for minor corrections. I'll keep thinking.

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Building a single machine for this purpose is flat out impossible.

No current or future storage medium can last that long, except perhaps carved stone tablets and no man mechanism could ever last that long without maintenance.

Fortunately, nature has a solution, which is self replication. They only need to last long enough to gather the materials to build a copy of themselves. The data would be passed on and shared between all the satellites that are alive at any given moment, with a whole bunch of back ups spread out across the population for to minimize the chance of data loss.

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I support theend3r's moon idea, not our moon though, if we want it to survive the Sun then we'd need to shunt it out into a much higher orbit, or possibly use a comet.

I'd also omit any hardware or moving parts, and have all the data etched on solid state storage (rock).

Yes it'd be big but a moon can support it :)

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I think the safest option would be to place it in Lunar orbit where it can observe the earth and sun without the problem of earth's exosphere.
Fortunately, nature has a solution, which is self replication. They only need to last long enough to gather the materials to build a copy of themselves.

Basically what I wrote. Intelligent machines capable of self repair/uprgrade/replication situated on the Moon.

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Whatever I would make, I wouldn't put it on, or anywhere near the moon. The Sun is supposed to turn into a red giant and expand hugely, possibly even out to Earth's orbit. Maybe out in a solar orbit around Saturn/Neptune, using huge solar panels to cool any components to superconducting speeds.

Even still, 5 billion years is an immense amount of time...

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No current or future storage medium can last that long, except perhaps carved stone tablets and no man mechanism could ever last that long without maintenance.

Stone tablets are man made... Seriously, stone tablets rely on artificially produced grooves to convey information - and those grooves are themselves subject to physical wear and degradation. Those grooves can endure a *LOT* of physical degradation before the information begins to degrade, but the amount they can endure is not infinite.

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If underground on an airless, tectonically stable body, they could last a very long time....

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Okay, since we are now talking about petabytes, then I can see this in the realm of reasonable volume requirements.

You still have to worry about power though. Irregardless of where it is, solar panels will decay/get damaged, RTGs will run out, anything with moving parts will fail eventually, and with billions of years at stake, the possibility is near 100%.

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no static system can last that long on its own. self repair and continuous production of redundant copies ( aka reproduction ) is the only thing that can preserve information for that long. But hey, we are already doing that already. So our "satellite" that can last 5e9 years and record all our history can, and should be simply us ourselves.

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Etching it microscopically on gold leaf would be an idea as it wouldn't react with anything.

This. Imprint it on gold on the shadowy side of a large slab of something massive enough to neutralise any thermal influence from the sun, deep in space. Only about 3K to drive reactions or creep, non-reactive medium, no mechanical stresses, should last plenty long.

As for the writable memory, I have no idea. 5 billion years is a hell of a long time for any machine with dynamic parts to last. I'm gonna say "can't be done".

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This. Imprint it on gold on the shadowy side of a large slab of something massive enough to neutralise any thermal influence from the sun, deep in space. Only about 3K to drive reactions or creep, non-reactive medium, no mechanical stresses, should last plenty long.

Micrometeorite impacts and cosmic ray irradiation would erode it after a couple of million years. not mentioning things like a solar superflare or a direct hit of a bigger piece of rock.

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So do away with moving parts and the need for power.

How do you do away with the need for power if you are going to be actively adding data to it?

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If underground on an airless, tectonically stable body, they could last a very long time....

dont forget neutron shielding.

Micrometeorite impacts and cosmic ray irradiation would erode it after a couple of million years. not mentioning things like a solar superflare or a direct hit of a bigger piece of rock.

shielding shielding shielding. to prevent data loss to collisions, have more than one. you can also reduce the data resolution to compensate for any high energy ray damage that you cant shield against.

Edited by Nuke

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23 words: Death Star Sized Computer In orbit around Jupiter with shuttles for collecting hydrogen for a fusion reactor with 10000000000000000000000000000 tons of lead shielding

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I would recommend two satellites. One for data storage, one for data collection. The satellite for data collection simply can't last as long as the satellite for data storage because collection requires moving parts, power consumption, and a certain type of mobility. These things prohibit you from making perfect hard shells and protecting internal contents.

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There's no real way to do this with current technology that isn't overly complicated for the task.

At least, not if you want a renewable record, ie, yearly records of the sun, Earth, moon, etc. A record up to the day of launch, if contained in the proper vessel (it have to be micro-etched on something obviously, and contained in several inches of I'd say steel and lead to protect it from any outside influence other than that of someone who wants to open it up) could theoretically last up to 5 billion years.

However, if you want something thats going to continually record things up to that point, then you'll need something well beyond our technological capabilities at the moment.

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I'd store it all on some inexpensive 1 Terabyte hard disks. It would take a lot and wouldn't be stable for more than a few decades, but it doesn't need to be. What I'm putting on the face of every planet, asteroid, and moon I can get a probe to, is a symbolic message detailing two things, using the Milky Way galaxy as reference: when to find the hard disks, and where. They could undoubtedly carbon-date the probe that inscribed it, and use that to figure out where to go. These inscriptions would be massive, kilometers wide and deep, to ensure that they will likely survive the coming years. In orbit around each of these celestial bodies, at the geostationary (if possible) orbit above the site where the engravings are, is a probe, much smaller, but with the exact same information inscribed within.

You really don't need to store the data, but how, where, and when to access it.

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Satellite? 5 billion years? Impossible. The orbit would decay and the satellite, wrecked by micrometeoroids, would end up crashing somewhere.

The only way to preserve information for such a long period of time would be to use several artificial caves (in case one or more of them get hit by a large object) beneath lunar surface. Earth is not a safe place because the surface gets recycled and there's atmosphere.

Moon has vacuum and geological stability that would ensure preservation for aeons. Data storage would have to be without moving or creeping parts. In fact, without parts whatsoever would be the best. Something written in the matrix of a synthetic, durable material would be the best. No magnetic storage. No electric charge storage. It has to be completely passive.

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