Good point. There are already amateur radio satellites in the orbit.  If they ever start broadcasting blockchain, I suggest we rename the network: Orbitcoin.

Sure it is.  The idea isn't particularly useful if mining, because mining requires as little a delay as possible.  Regular clients, however, can tolerate transmission delays just fine.  It's useful for getting the blockchain to parts of the world that Internet access is sparse or prohibitively expensive.

It now only costs 1,000,000 BTC!

Looks like someone is going to attempt this:

https://www.outernet.is/

Unfortunately, I can see some very real technical and legal issues with trying to do this as described.

First off, Wifi is possible in only two bands.  Since the higher N band is very new, and many smartphones still don't support it, I'm going to assume that the older B,G band is what they plan to use.  But there was a technical reason that this band was chosen at the time of development; namely that the B,G band was license free worldwide.  But why was that, since such license free technologies didn't really exist before Wifi itself?  Because the B,G band is the resonate frequency of hydrogen.  Thus, energy transmitted in this band is heavily attenuated by any water or hydrocarbons found in it's path, and was considered useless for distance communications.  This is still true, and has much to do with why Wifi is so poor at clear range.  It's also why this band is shared by every retail microwave that I know of, since food is pretty much all hydrocarbons and water.  While there wouldn't likely be much risk of hydrocarbons in the line of sight from low earth orbit, there would be much water.  On average, the Earth's atmosphere has enough water from space to sea level to equate to a 32 foot deep dive under the ocean's surface.  The amount of power that would be required to push through this and be receivable by common wifi hardware on the Earth's surface would be rediculous.

Second, there are also sound techincal reasons as to why wifi multicasting is not commonly used.  Mostly because wifi is a time-sharing technology that (generally) permits more than one unrelated connection to coexist on the same channel.  This is permitted because normal mode wifi requires that the hotspot 'listen' to it's own channel several times per second for other broadcasters trying to share the channel space.  This doesn't always work well, but it does work more often than most people realize.  However, a hotspot in space couldn't coordinate timesharing of all the hotspots in it's radio shadow even if it were possible for it to hear them.  In this case, the sat based signal would effectively 'jam' the chosen channel across the whole of it's radio shadow, and also be a violation of international communications treaties as a result.

Third, the licesne free broadcasting nature of the B,G band is limited to 'terrestrial' transmitters, and therefore doesn't apply to satillites at all.  A new treaty would be required to even permit such a license, since every country has max transmitter powers in the B,G band that would be WAY below what a sat would require.

While using the new N band would reduce the power requirements considerablely, the other two issues would still apply.  Perhaps a lower frequency license free band would work with modified FM band recievers, but I can't see a way around the international communications treaties regarding this.  Perhaps a broadcast stream that can switch around frequencies in the higher frequency shortwave bands would work, but the sat would have to be able to respond to the reflectivity of the ionosphere and changes in the critical frequency.  Most Shortwave broadcasters have to stay below the critical frequency so that their Earth bound transmitters can reflect their signal off of the F layer of the ionosphere, but what about a broadcaster in teh shortwave bands that deliberately stays above the critical frequency so that his signal is not reflected back into space?  Regardless, the data throughput woudl be low due to a narrow usable bandwidth and a particularly 'noisey' radio environment in those bands.

You know more about it than I do, but perhaps this is relevant:



http://www.reddit.com/r/technology/comments/1wqgmh/outernet_wifi_for_the_world_from_outer_space/cf4nshr

Actually, now that I look, someone also asked this question on their forum.  The response seems dubious:

https://discuss.outernet.is/t/can-2-4ghz-even-penetrate-the-atmosphere-efficiently/34

Well, it's either misinformed or deliberately false.  I've had my kids look at this site and another site (waterstep.org) to compare the tech claims of one charity asking for money compared to another, and we've largely come to the conclusion that this outer.in site is a scam designed to illicit donations from well intended.  As my son noted, the first clue is the "for free" claim.  That can never happen.  While it might be free to receive, there would still need be advertisments and such.  And it's not false that low earth orbit sats have used the S band, but that particular section of the S band is where the attenuation from water is greatest.

EDIT:  By "that particular" section of the S band, I mean the sliver of unlicensed bandwidth that B/G wifi occupies.  The S band is very wide, but only that portion is unlicensed, and because it's an ISM band (Insustrial, Scientific & Medical) that is used primarily for purposes besides communication.  There are other ISM bands, but none that are so wide as the one that B/G wifi (and Bluetooth, and several other short range techs) utilizes.  It's that wide because microwave ovens (in particular) use that band due to the fact that the high attenuation of radio waves by hydrogen is useful for heating with radio waves, and microwaves are so paowerful that they produce a lot of 'splatter'.  Until wifi came out, it was largely believed that  the band was useless for communications due to both the high attenuation and the likelyhood of interfereance from microwaves.  Wifi protocols are designed with the likelyhood of occasional interference in mind, however.  So is Bluetooth.  The rest of the S band experiences attentuation due to water in much the same way that radio does in general, in that the higher the frequency the greater the attenuation from water.  Both the US and Russia have massive ultra-low-frequency transmitters, with enormouse power ratings, in order to communicate with submerged submarines via morse code.  There are ham radio geeks called "lowfers" who try to communicate in this range as well, but it's hard to do anything when the wavelength of the signal is hundreds of kilometers long.  So while there are useful frequencies outside of the wifi band on the S band, they generally require more power for the same task than a lower frequency band such as the L band, and less than higher frequency bands such as the K band.  So most of the S band is particularly good for a low power downlink to consumer class receivers, just not within the B/G wifi band.

Another issue that I can see with using the small 10-cube type sats for broadcasting a wifi signal, even using the 5 Ghz N band, is that wifi channels are normally 20 Mhz wide, which is a particularly broadband signal to produce.  With wifi, this is a good thing, as your signal can cover the office without much interference and signals produced by nearby offices are strongly attenuated before they get into your office, and permits a high data rate.  However, all things being equal, a signal that is twice as broad requires twice the power to be recieved at the same distance under the same conditions.  The wifi standards permit quarter width band signals, but almost no one uses them because they don't help under normal hotspot ranges and conditions.  So, at a minimum, a wifi datacast would have to be 5 Mhz wide.  However, the DRM standard is a digital sound & data standard that uses the bandwidth of the old fashioned shortwave & AM channel standards; which is 9 Kilohertz wide in Europe and 10 Kiloherts wide in the rest of the world.  However, DRM also permits doubled or halved channel widths.  So if we compare the double DRM channel for data throughput versus the quarter width wifi for reduced power requirements and the wifi broadcast would still require roughly 250 times as much power to acheive the same signal quality on the ground versus a double wide DRM broadcast, using the same frequency, sat quality, etc.

And again, the common shortwave receiver is a far better receiver than the common wifi phone chip, so the DRM signal would be much more likely to be clearly received than the wifi signal even if the 10 cube sats could actually produce the 250 times power level.  I'd be surprised if those cube sats can produce a 50 watt RMS output on a continuous basis, and (off the top of my head) I'd say that a DRM transmission would require around 3Kilowatts to properly blanket a 600 mile circle footprint to a clear & receivable degree.  Even a half channel width DRM broadcast (4.5 Khtz wide, minimum) would require at least 1000 watts on an ongoing basis.  Keep in mind, DRM is the digital version of an AM talk radio broadcast.  A local AM broadcaster generally uses between 3 Kilowatts (at night, when the D layer doesn't attentuate the middle wave band) and 20 kilowatts just to cover a major metro area and the surrounding countryside, with a practical coverage radius of 100 to 150 miles.

Why is the response dubious.  Remember this isn't a two way system.  It is more like broadcast sat TV but for information.

2.4 Ghz is fine for sat downlink (remember one direction only).

For example one sat radio system runs on L brand which is 1 to 2 Ghz.
http://en.wikipedia.org/wiki/WorldSpace

In the US Sirius XM radio operates at 2.3 Ghz.
http://en.wikipedia.org/wiki/S_band