

Solar planes are not the future of flight - aatishb
http://www.empiricalzeal.com/2013/04/06/solar-planes-are-cool-but-theyre-not-the-future-of-flight/

======
jared314
Passenger aircraft is a no, but a stable UAV platform is a possibility.

What happened to the idea of a stable airborne cell tower? The only response I
can find is "unlikely" or "unreliable" without any data.

------
emeraldd
Something really bugs me about this. Unless I'm mistaken, Bernoulli's
principle doesn't say anything about throwing air down ....

[http://en.wikipedia.org/wiki/Bernoullis_principle#Applicatio...](http://en.wikipedia.org/wiki/Bernoullis_principle#Applications)

<http://warp.povusers.org/grrr/airfoilmyth.html>

What am I missing here?

~~~
Someone
Read that second page, specifically the "Overall air direction is changed to
go down" in the last two pictures.

You can also see this from conservation of momentum; it requires that, if
something goes up, something else must come down. With an entire airplane
going up, there isn't much else than air to come down (exhaust gases are
another option, but then, you are talking rocket, not airplane).

And yes, gravity means the (airplane plus surrounding air) system isn't
closed, but its effects only make matters worse; airplanes have to throw down
air even to maintain level flight.

------
mistercow
>The plane isn’t going to run out of juice, unless it meets some clouds or
some serious tailwind.

Why would a tailwind matter? That would cause it to go faster relative to the
ground, but it shouldn't matter in terms of lift, right?

~~~
RobertHoudin
An airfoil (wing) creates lift when air flows from the leading edge to the
trailing edge, and the speed of this airflow is one of the factors which
determine how much lift is generated. A strong tailwind will interrupt the
airflow, induce turbulence and decrease lift. Thus, an airfoil moving into a
headwind will generate greater lift than one moving through a tailwind.

~~~
mistercow
Ah, so it's just the transition to a tailwind that causes problems? That makes
sense.

------
coderzach
Question: Is the energy per square meter greater at higher altitudes, due to
less atmosphere to reflect light?

------
EthanHeilman
Why not fill the wings with helium or other lighter than air solid. ~Lift
increases by the cube, weight by the square.

I'm waiting for someone to invent an extremely cheap lighter than air solid
which can act like a battery.

~~~
hayksaakian
> Lighter than air solid

Is this even possible at normal temperature? I can't imagine this at 1 atm.
and room temperature...

after some googl-ing:

<http://en.wikipedia.org/wiki/Aerogel>

------
curiousDog
Just to understand the terminology better, if we invent more energy dense,
lighter batteries in the future that can be charged via solar power, will the
planes powered by them still be considered solar powered?

~~~
saidajigumi
Yes. The batteries don't generate any power, they just store it. The Solar
Impulse has batteries -- that's what lets it fly at night for example. See [1]
for a bit more detail on how energy is managed at night.

[1] <http://solarimpulse.com/timeline/view/6437>

------
brianbreslin
Question: why have commercial airlines not added solar panels to the wings to
power things like the a/c systems or other auxiliary power requirements? Could
that not reduce fuel consumption?

~~~
evgen
Solar panels add weight, offer no structural support, complicate maintenance,
and would need to to have their transparent cover hardened somewhat to deal
with the sort of beating that an airplane skin takes. Not impossible, but you
would probably see it first on the top of the fuselage rather than the wings
and they would still only offer a small boost to the onboard APU. It is
possible that by covering the skin the panels would also make it harder to
inspect the pressure envelope that is the real skin of the plane underneath
the panels for wear and fatigue. The engines are already some very efficient
generators, so the panels would have to be very good to justify their added
weight.

