RE: Decaying Orbits.
There is no such thing as a decaying orbit! Well, unless you are
inside the atmosphere of the body you are orbiting. In that sense, we
might say that the earth is in a decaying orbit since it is inside the
solar wind. But it will take longer than the sun will last for the
Earth's orbit to decay by a measurable amount. Well, when the sun
swells up to red giant status then Earth's orbit will probably be
inside the photosphere, so then the orbit would "decay". But that's
quibbling.
This is a huge misconception that I blame Star Trek for. The ships
always lose power and start to crash into the planets. But that won't
happen if you are in orbit! It requires no energy to stay in orbit,
you are already falling into the planet, it's just that you keep
missing. There is no orbit that describes a spiral. Orbits are always
parabolic, hyperbolic, or elliptical (with circular being an elliptical
orbit with zero eccentricity). Alberto, help me out here!
OK, here's what happens if you try to shoot a rocket into the sun.
First, you have to lift that puppy out of the earth's gravity well.
OK, we can do that, we've sent probes out of earth's gravity. But you
still have the giant angular momentum of Earth's orbit around the sun
to kill. You can't just point at the sun and set thrusters on full.
That won't work. You hit the sun by aiming your rockets in the
opposite direction that the earth is traveling and killing your
sideways velocity. The more momentum you kill, the more elliptical you
make your orbit. We would need an elliptical orbit with enough
eccentricity that perihelion is inside the sun's photosphere. Well, at
that point it wouldn't take much more to just kill everything and have
an ellipse collapsed into a straight line.
This is not a trivial problem. The big advance that enables us to send
probes to various outer or inner planets is the slingshot. We can make
use of the planets to add or subtract angular momentum. But, in order
for us to do this with nuclear waste, we'd probably have to use the
Earth. I can't imagine that would exactly be politically popular.
Given the failure rate of our space probes, I can't see trusting a
rocket stuffed full of radionuclides. The absolutely *most* dangerous
possible thing one could do with these things is to vaporize them and
have people breathe them in. Trips in rocket ships are very likely to
eventually vaporize the cargo.
If the amount of waste is small enough that we could send it into the
sun, it would still be much easier simply to crash it on the moon. But
it would still be much much much much much much cheaper simply to
vitrify it in glass bricks and stack it in some old mineshaft or salt
dome.
The biggest problem with nuclear waste is not long term storage, but
short term temporary storage. That's when you get these corroding
barrels of radioactive liquids spilling into the drinking water. That
is the biggest concern, that radionuclides are inhaled or ingested.
But if it was handled properly it would be absolutely safe, or at least
orders of magnitude more safe than going down into coal mines or
driving a car or climbing up on the roof every year to do maintenence
on your solar water heater. The earth's crust is full of radioactive
materials. This is not considered dangerous because it is dispersed
and far away from people.
I don't care how cheap space travel becomes. It could become as cheap
and easy as a trip to Europe. And it still wouldn't make sense to dump
nuclear waste into the sun.
=====
Darryl
Think Galactically -- Act Terrestrially
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