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34C3 preroll music
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Herald Angel: The next talks – actually
two talks – will be about, somehow about,
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saving the world and saving the
environment. We will have two different
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ways of saving them and the first talk is
"Saving the World with Space Solar Power".
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It's held by Stefan and Anja and they work
as space engineers in Berlin at the
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Technical University. That talk will be
followed by another approach which is
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introduced to you by Christoph. He has a
PhD in theoretical physics and his former
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work was he was working with higher loop
perturbation theory and supersymmetric
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yang-mills theories and now he is doing
airborne wind energy and that will be his
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talk also. Please give the three of them a
warm applause!
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Applause
Anja Kohfeldt: Yeah hello! As you have
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heard today we are trying to save the
world with introducing you to two very
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different approaches of sustainable energy
generation. We are three, the three of us,
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and we start with Stefan.
Stefan Junk: Yeah hello everyone. Thanks
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for having us here!
Anja: And me with our talk about space
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solar power. Of course we have an outline
and I will start the introduction with
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showing you this very nice picture. Here
you see the earth at night also known as
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the black marble. It's a very interesting
picture because it illuminates you or
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shows you where people live or at least
where people have electric energy. But
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there is more information in this picture:
When you start comparing these pictures
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from different years, you also can see how
certain regions are developing. And you
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also see where suddenly it gets dark,
where there has been a catastrophe or a
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war or something like that. So the
availability of electricity is an
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indicator for human development. We still
have an increasing amount of power. This
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is also something we can see with that
picture. But, unfortunately, currently
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this power demand is largely covered by
fossil resources. So yes, we need
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definitely renewable sustainable energy
such as solar power, wind parks, water
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plants or even other solutions. The thing
with terrestrial bound energy plans is
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that they are bound to a certain location
on earth, normally, so you either need to
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decentralize them having a lot everywhere
or you need a lot of the transfer
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infrastructure. The other thing is –
especially when thinking about a wind or a
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solar power – that the availability is
very varying and bound to certain
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conditions. So you need to store the
energy. When coming, when talking about
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solar energy of course I mean we have the
day/night cycle, we have the atmosphere,
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so we have weather interferences. So why
not go into space? There are some selling
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arguments – or some really selling
arguments – about space solar power: As I
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already said it's sustainable, because
it's sun powered. Space generally is very
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very large, so we can build quite big
structures without covering any space, any
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area on earth. We are, it is possible to
have some sunlight on our satellites up
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there all around the clock. And we don't
have an atmosphere, so there is no
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weather. So space solar power promises to
have an unlimited, constant and
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predictable energy source. That's cool!
Good! In addition, we don't need that much
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infrastructure to distribute the power on
earth. For example if you could compare
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that to a huge solar theater for example
in the Sahara, you would need a lot of
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cables in order to get the power for
example to Europe. This comes with some
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problems. But also if solving the problem
of power transmission, you can get energy
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to very very remote locations on earth and
you also can get the energy there quite
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quickly. And of course the intervention in
the landscape is … let's call it minimized
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to a certain way. This concept of space
solar power actually isn't that young.
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It's there's a pattern from Peter Glaser
from the 70s who already proposed a method
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and apparatus for converting solar
radiation to electrical power. And here
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you see – you yes there's a small red
spot, I'm not sure whether you can see
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that – but you already see that he
introduces all the components that are in
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need: Of course we need the earth, we need
some large area for solar, for sun
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collection and we need some some antenna
in order to transmit this power. Since the
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70s these concepts were actually discussed
all along. Since then they where
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discussed. And the state of the art
approach for that is called SPS Alpha
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which stands for "Solar Power Satellite by
means of Arbitrarily Large Phased Array".
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It's the best-documented approach in that
area which comes with a phase one study
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financed by NASA in 2011 and 12, and they
suggest a satellite structure based on the
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geostationary orbit which is non moving
gravity gradient stabilized. It's
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collecting the sun with a very very large
mirror array and a transmitter power with
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a microwave beam. It looks like that for
example – or it could look like that, like
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a whine glass. It could look like a
puddle, but there is three main components
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here: So we have the Sun Reflector Mirror
– this is this very very large shape –
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these sun reflecting mirrors are made of
actually solar sail material so extremely
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lightweight although they are so big. The
core piece of this installation are the so
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called hex modules which you see here and
they host both the solar array, the solar
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panels and the wireless power transmission
modules. We come to that later. And then
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of course you also need the structure
which holds everything together. In
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addition to that you need some support
structures like little robots combining,
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fixing, exchanging modules and so on, but
they are not further discussed yet. But
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the NASA approach isn't the only one.
There's also an approach from from JAXA.
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This is a Japanese Space Agency. They call
their approach tethered SPS. It's also a
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gravity ground stabilized approach which
you can see here. The idea is basically
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the same but they don't have the mirrors.
Their selling argument is: You know our
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system is so simple, we're sure it will
work somehow. But they also say that it's
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not as efficient as the other approaches.
In addition there are Japanese scientists
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involved in the SPS Alpha study. But what
I think is most interesting there are also
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a lot of Japanese approaches driving
forwards the wireless power transmission.
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Then there's a new – quite new – approach.
This is from the Chinese space agency of
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CAST and they suggest a Multi-Rotary
joints SPS, which you can see here. So
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here in this the yellow spot over here
also is the transmission antenna. But they
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have their solar arrays bound in this
structure which is approximately 10
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kilometers wide and they adjust the
position of their solar panels according
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to the sun position. So this is how they
try to increase the efficiency. There's
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also a paper from Europe which is quite
old but I'm not aware of a current work on
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European ground here. If we summarize some
of the core parameters of these three
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documented or still discussed approaches,
we come to this nice table. So we are
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talking about a power transmission between
1 and 2 gigawatts. These entire structures
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have a mass of about 10,000 tons – metric
tons – or even more. Yes the Japanese
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approach the antennas are quite big. We'll
come to that later. This comes with a
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certain energy density, but the total
efficiency of this of these approaches are
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calculated – and there's also a little bit
of like a small wish list included. This
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total energy is in the range of more or
less 20%. I put a question mark behind
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this 25% of the JAXA approach, because
they even said that they won't be as
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efficient as the others are. So don't take
this number too serious. Maybe we must
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calculate it. Yes. With that with these
three approaches, I would say problem
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solved, isn't it? Applause
Stefan: .......concepts. But there are some major
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challenges we want to point out here. At
first this is the attitude in orbit
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control so this station is in the
geostationary orbit. There are several of
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the TV satellites doing the same and it's
working quite well, but these TV
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satellites are about 1.8 metric tons and
this station we're talking about is about
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10,000 tons or 9 to 25 thousand tons, so
this is a huge difference. In the
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geostationary orbit it's not a big deal to
rotate. It's very slow. So we just need to
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point to watch the earth to hit the
designated point on earth we want to
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transfer the energy to. And then we have a
phased array antenna, so these are these
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little modules you saw before to form a
beam which points exactly to the receiving
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point at the earth for the energy. Another
point is the the orbit control. This means
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the distance from Earth and the speed the
station is traveling with. This is another
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point. This is already for TV satellites a
little bit difficult to do. And now we
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have, as I said, this one thousand metric
tons station to lift up to the right
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distance or to accelerate. There are
several forces trying to push us out of
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the exact orbit and we would lose the
exact spot we want to point at. And there
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is the lunar gravity, the sun gravity or
solar gravity, and the flattened poles of
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the earth. You know the earth is not a
perfect sphere, is more imperfect, is more
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like a donut. You have flattened points at
the poles which disturb the gravity field.
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There are solar winds and radiation
pressure. Solar wind comes from the Sun.
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These are particles hitting the station
and pushing it out of the orbit. And there
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is radiation pressure, the same that comes
from deep space. This station is huge. So
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you have a huge surface. This is different
from the most TV satellites. So we have to
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overcome this. Luckily, we have nearly
unlimited energy with this station, and we
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can use electrical thruster. So we don't
need any fuel or propellant. Maybe a
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little bit propellant to bring up to the
station. Another point is the power
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transmission. I think this is the most
critical point. As I said, it's in a
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geostationary orbit and I have an example
here. I chose the MR SPS because the
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numbers are so round, but most of the
concepts are similar, as you saw before.
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So I think about a 1GW output station. And
in the picture on the right and chopped
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you can see the yellow point is the
standing antenna. This would be about
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1.000 meter in diameter. So this is about
110 soccer fields placed in space. This
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antenna is sending a microwave beam with
2.45 GHz or 5.8 GH. These frequencies are
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chosen because of the low attenuation or
damping in the atmosphere. We want to
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transfer the most energy. And this beam
hits at the receiving antenna, or in the
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literature called the Rectenna. And this
Rectenna is going to be about 5.000 meters
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in diameter. This is 2.750 soccer fields,
or about 20 times the Messe Leipzig area.
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So you can imagine this is a big deal. If
you think about wind parks are ugly, then
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maybe you think about this area. OK, so
you can read more about if you like in the
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references. We have a link to this. Now, I
guess you wonder about the efficiency of
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this. Anja talked about it already a
little bit. I have the subsystems here
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including, and I think the most important
part is this microwave beam. This is the
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third position, and this is actually not
tested. So this is just a calculated
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number. These 85% or 90% to 95% is just
from the studies we read. Current tests
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are more in the area of 1% or a few
percent. And most studies are not really
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certain about the total efficiency. So we
have 18% to 24% with these numbers. And
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from other studies we have 13% to 25%. So
this is most calculated. So now you would
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wonder if wouldn't laser work for this? Or
microwave beep sounds nice and you have
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this nice receiving antenna. But a laser
would be much smaller, I guess. So, yes,
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basically you could use laser for this.
And it would have a much higher energy
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density. So you could hit a really smaller
spot on the earth to receive the energy.
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You don't have this 5 kilometers receiving
antenna. But most of the research
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institutes don't want to talk about
lasers. I think it's just a little bit too
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obvious that you have some …
Laughter
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Stefan: OK, so this is the most technical
things, I think.
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Anja: The other question is, who is gonna
pay for that? And if we talk about this
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extremely large structures that have to be
built, and since they're also are meant to
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be in the geostationary orbit where we
have a certain radiation force, and we
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want these components to operate for quite
a long time, they are usually quite
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expensive and geting all the certification
for sending them up there is also very
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expensive. Somehow the SPS Alpha approach
has thought about that, and they are
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aiming at, although the numbers are
varying very much, at a material cost of $
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250 per kilogram, which still is some
billion dollars. And it is also a wish
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list. So they are aiming for this number
in their third approach where they think
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that they already have the mass
production, and have the certification,
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and the engineering and development cost
all covered up already. There's another
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thing and this is the launch cost. So we
are talking about a structure which is
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maybe 10 thousand tonnes large, or heavy.
Again, the SPS Alpha guys, they hope that
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they could launch a kilo for $600 into the
low-earth orbit, and continue from the
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low-earth orbit into the geostationary
orbit with electrical truck trusters. OK,
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maybe if the BFR rocket will be available
for the price of the Falcon 9, maybe. But
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this also would take some time. Just a
reality check right now, for the prices
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the SpaceX provides on their site, the
Falcon Heavy which was erected today, I
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don't know whether you have heard that, so
also the Falcon Heavy has not flown yet.
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But SpaceX hopes that they could sell the
the Falcon Heavy for 90 million dollars in
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order to lift 26 tons into geostationary
orbit. But that would be approximately 400
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launches for such a structure as the SPS
Alpha, and also would cost some tens of
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billion dollars. Additioned to that, there
are some other costs like the initial
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orbit installation cost which comes with
11 billion dollars, and an operation of a
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100 million a year. So it's quite
expensive and probably this is also one of
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the reasons why we don't have space solar
power, yet. But still, I mean, we have
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technical problems, this is just money,
maybe it's also solvable, isn't it?
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Stefan: Yeah, so you know about the
concept, you know about the challenges,
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and let's assume we can overcome these
challenges, and someone is funding this
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big station. I think, there are some
considerations about if we want to do
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this. And at first, so this beam is, you
need a precision of about one 10.000ths of
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a degree plus minus to hit the spot at the
earth. So this is like you want to hit a
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hazelnut of a 100 meters from a station
flying with 3 kilometers per second. If
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there's something goes wrong and the beam
is hitting the wrong spot, maybe, you
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know, it's not a good idea. Or if some of
the antennas are not working well, the
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beam is not forming right, and it's
straying somewhere. So this is one point.
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Let's assume everything works well, and
the beam is still going through the space,
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and it's going through the atmosphere. And
there are some other satellites going.
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Maybe, for an accident, they go through
the beam. What happens then? Or, if you
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can't, or by accident, and the airplane
goes through the beam. So it's not even
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allowed to turn on your phone on the
airplane. You can imagine what happens if
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this beam with 50 watts per square meter
hits the airplane. I don't want to sit in
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this. And then you can't avoid the
animals, birds, insects, whatever go
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through the beam. And maybe you have a
same imagination like I have, or we have.
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Soft laughter
Stefan: And it looks a little bit like
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this maybe.
Laughter
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Stefan: It sounds pretty scary, I think.
Doesn't it a little bit sound like an
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energy weapon? So we thought about: OK 50
watts per square meter; it's not like a
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nuclear weapon, but still it could harm a
lot. There is a high energy density, and
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you can really fast readjust this beam. So
you can point it in 1 second to the
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receiving antenna, and the next second,
you can just point it to some city, and a
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second later, you point it just back. It's
really fast to change. It's not really
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defendable. I mean, you can sit in the
bunker and try to hide, and maybe put your
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aluminum hat on. After all it's useful.
Applause
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Stefan: But still, this thing is 24/7 on,
so it could hit your bunker all the time.
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And last year, there's a lot of interest
from military institutions. So this is, I
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think it's a bit scary. OK. And then you
would ask: But it's legal to install this
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kind of application? So basically, yeah.
You see, there is already the United
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Nations Outer Space Treaty. It was first
signed from the Russian Federation, and
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the United Kingdom, and the United States.
And now it's in the United Nations
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treaties and most of the other countries
signed it, too. It's about all the
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activities of States in the space. What
does it say about this case here? And it
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says, there are no nuclear weapons or
other weapons of mass destruction allowed
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in outer space. As always, there's a
backdoor. If you install a military object
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in outer space with a scientific reason,
then it's allowed again. So another point
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is in this treaty you must not influence
the earth environment at all. There are no
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real studies about this. I have a feeling
it's going to influence somehow the
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environment, but I'm not sure about this –
I'm not a lawyer. So finally this all this
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funding and this technology and the
knowledge is necessary, so it's only
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possible by some few states to build
this. And how do you prevent that certain
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leaders of states or whoever's want to
build this is misuse this technology. So I
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can't give you an answer on that, but I
think there are some who shouldn't have
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this. Yeah and you maybe you can think
about this after the talk. And now we have
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some take-home words for you from Anja.
Anja: So yes, the concepts are existing
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and we don't say that they should not be
discussed and that they are entirely evil.
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They it's technologically feasible – at
least that that's proposed some studies –,
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but I mean it's still challenging: The
technology is not there yet, but the moral
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questions are still open. So yes it's
still pretty science-fiction and as I said
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we don't say it's we should not do that at
all, but at least we should think about it
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and be critical with this kind or also
with other new technologies. So but right
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now, maybe, we should think about: Is
there another solution to this energy
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problem? Maybe a more realistic, maybe a
less problematic one I mean?
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Interrupted?
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