

Project Loon details from the Christchurch event today - mkl

Pictures: http:&#x2F;&#x2F;imgur.com&#x2F;a&#x2F;IrZFq<p>I went to the Project Loon event today (Sunday June 16) at the Air Force Museum in Wigram, Christchurch, New Zealand.  Here&#x27;s what I learned.  (Some of this may be misunderstood or misremembered, so don&#x27;t take it as absolute truth, and this is all early prototype stuff anyway.)<p>It was quite a big museum-style exhibit with lots of people (it had been on the news), and several members of the team were there answering questions.<p>Currently there are four balloons up.  Several have recently been successfully been brought down and recovered from the ocean (land landings are easier to recover but there is no nearby land east of here).  The main reasons for testing here are that the stratospheric winds are &quot;boring&quot; (basically all west-east) and this latitude has few countries to coordinate with (they&#x27;re working with Chile and Argentina).<p>The project involves a &quot;couple of dozen&quot; people and has taken two years to go from &quot;ideas on a chalkboard&quot; to this.<p>One of the balloons was there, inflated to its maximum size (launch size is smaller because of pressure differences, but it&#x27;s a superpressure balloon with a maximum size).  It was roughly 5m high and 12m in diameter.  It has an upper portion with helium and a lower portion with air, with an impeller that can change the pressure in the air part, and thus control the height.  The height control is used to navigate, by moving to layers with different wind directions and speeds, and can take it right down to the ground (though that sounds a bit untested).  They are aiming for flights of &quot;hundreds of days&quot;.<p>(continued in comments)
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mkl
Clickable: [http://imgur.com/a/IrZFq](http://imgur.com/a/IrZFq)

Edit: that should have said 8m high

There are multiple control and networking systems connected together with a
CAN bus (for controller area network, used in cars). It sounds like 4-5 ARM
cores total: two Linux systems ("unfortunately" two) and one realtime
controller in the main payload, and a failsafe controller up on top of the
balloon (which controls helium release and parachute deployment). The
controllers are designed to recover from being reset very quickly, since
resetting is used as a kind of universal problem solver (sensor issues, cosmic
rays flipping bits, etc.).

The stratospheric daily temperature swing (30°C down to -80°C) causes
difficulties, so the electronics are in styrofoam boxes about 3cm thick, and a
heating system keeps the electronics warm and the batteries warmer. The rough
altitude is 20km, but it sounds like they cover about a 5km height range, I
think connected to the daily cycle somehow too.

The solar panel provides 100W in full sunlight. It is mounted directly under
the transparent balloon (which reduces the amount of energy by 20-25%). The
batteries hold about "ten laptop" batteries' worth.

There are three vertically mounted omnidirectional antennas for balloon-to-
balloon communication, and one downward facing antenna. The downward one has a
90° cone angle, and is designed so that the signal strength is even across the
40km diameter ground area. 2.4GHz and 5.8GHz, one for balloon-to-balloon and
one for ground (I think 2.4GHz is ground).

The communication protocol is custom, to account for the large distances and
to coordinate the ground systems so they don't transmit at the same time
(since they can't see each other). The system basically acts as a VPN between
end users and the ground station (upstream ISP), and traffic inside the VPN is
encrypted separately as well. Currently upload and download speeds are
symmetric (they don't really know what the speed will end up being, but
roughly the same as 3G).

The eventual goal is commercial internet access to parts of the world that
can't get it other ways, but there are no concrete plans for how that will
work yet, since they expect to go through many more iterations of prototypes
first. Commercial use will necessarily involve large fleets of balloons to
provide continuous coverage (even if they end up covering more are each),
since they move quite a lot. The balloons measure atmospheric conditions
themselves and are coordinated from the ground.

Edit: I forgot to mention that there is a standard aircraft transponder
(yellow and black cables in first picture), and the corners of the ~1.7m
square solar panel have strobe lights to meet air codes.

~~~
aunty_helen
The protocol uses time division multiplexing to solve the hidden node problem
([https://en.wikipedia.org/wiki/Hidden_node_problem](https://en.wikipedia.org/wiki/Hidden_node_problem))
where two nodes can be transmitting at the same time causing a collision.

They also mentioned that they didn't tilt the solar panel to follow the sun
for reduced complexity, cost, weight and the risk of failure of a servo
system.

They don't know what the speeds will be but 'as fast as 3G' was the marketing
line.

To me it seemed like this project still had some large hurdles to viability
but it was cool none the less.

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chad_oliver
I was chatting with some of the Google people at the event, and they said that
the balloons have been responsible for a few UFO sightings. In fact, when one
of the balloons' transponders failed in flight, they were able to track the
balloon by the UFO reports online! This happened while they were testing the
balloons in California's Central Valley.

They said the balloons are expected to take two weeks to circle the globe.
Given that they said they'll eventually stay afloat for 100 days, that gives
them plenty of opportunities to bring the balloons down in a specific location
in order to make reuse easy.

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mappu
I went as well - i don't have much to add and my questions were certainly not
as insightful as yours - but i will add that i was told that six balloons had
launched, and the real balloons are larger than the demonstration as it's
pushed down to fit into the demonstration hall. They didn't have a
demonstration of the building antennas.

Multiple balloons in the air form a mesh network, allowing you to put your
uplink only where it's convenient for you - which i guess is the key to making
this a viable solution somewhere inbetween 3G towers and satellite internet.

It was a fun event, i hadn't been to the airforce museum before - lots of kids
with helium balloons, poster giveaways and folded balloon animals. Someone was
wearing the first Google Glass i've seen and lending it to people to try (that
must get old pretty quickly).

~~~
mkl
Most of those facts weren't from my questions :-D I asked a few, but there
were lots of others asking questions too, so I did a lot of listening.

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TezzellEnt
Do you think that project loon has anything to do with the recently acquired
Makani Power? [http://cleantechnica.com/2013/05/24/google-buys-makani-
wind-...](http://cleantechnica.com/2013/05/24/google-buys-makani-wind-power-
kite-power-company/).

It would be interesting if they were to merge these two projects.

~~~
mkl
It seems pretty unlikely, if only because of the very different altitudes the
projects operate at (the kites can't be high because of tether weight, and the
balloons can't be low because of weather and aircraft).

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davidjohnstone
Apart from the commercial model that these will use (what they'll cost to make
use of, etc.), the thing I'm wondering about is how visible they'll be at
sunrise/sunset.

Google is saying that they'll be barely visible to the naked eye, but just
after sunset/before sunrise, they will be illuminated by the sun when the rest
of the earth is still dark, which should make them more visible than they
would be during daylight hours. In my mind, I'm imaging a dark sky that's full
of little orange dots. I have no idea whether or not it would happen like this
though.

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carrot
Thank you for sharing! This technology is definitely interesting. I will be
following news about it closely and would appreciate it if you could post more
updates in the future.

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Luyt
I think certain countries will suspect that these balloons are used as spying
devices, and probably shoot them when they enter their airspace.

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barryhunter
Are they going to add downward facing camera(s) to capture close to real time
Aerial imagery?

