# Curious , why not send spent nuclear rods to the sun ?

Discussion in 'General Science & Technology' started by river, Jan 10, 2014.

1. ### SarkusHippomonstrosesquippedalo phobeValued Senior Member

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All agreed, and seems we were talking cross-purposes here: I was talking relatively (or was at least thinking that way even if I didn't word as such) rather than absolutely, since we're talking about leaving the Earth and heading to either the Mars or Sun.
I.e. the motion of an object on the moon, relative to the moon, is influenced more by the Earth than the Sun.
So apologies for that - me being muddled in my thinking and writing.

Anyhoo - I think we're agreed it's significantly more to drop something into the Sun than to get to Mars.

3. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Main force of an object on the moon is the moon is the moon's own gravity. The second strongest force is from the sun, not the earth.

The moon's gravitational force is small enough that if it is setting on a scale, the indicated weight will vary - is least when the moon (seen from earth) is "full" and it is in "high noon" sunlight. When it is the greatest is more complex (if it remains at that one spot) and I'm too lazy to compute that, but would not be surprised to find the weigh varies by 1%

5. ### SarkusHippomonstrosesquippedalo phobeValued Senior Member

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Yep - again, all agreed, and it seems I'm struggling with putting what I mean into words that don't actually mean something else.
Brain-fugue or some such.
Anyhoo - I'll give up trying to explain, lest I dig further holes for myself.

But yes, you are correct, and thanks for the explanation.

7. ### NMSquirrelOCD ADHD THC IMO UR12Valued Senior Member

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I don't know the math behind rail guns, I understand there must be limits otherwise they would be implemented by now..

so obviously I am only an amateur, I submitted this as an alternate option, being only an amateur scientist (armchair scientist?) (not qualified to be 'the' goto source of science)(dunno if I even qualify for amateur)
I left it open for discussion not insults.

billy T you have been here forever and should know not to insult.
(specially when you don't do the math , leaving yourself open for argument.)
all you had to do is explain why it wont work.

8. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Please quote back to me what part of my text was "insulting." None was intended to be.

And no, I don't need to calculate to express my considered and reasonably well founded opinion. I hold a Ph.D. in physics, and have worked with super-sonic missiles to a small extent; know a little about shock wave dissipation, but not enough to calculate such an extreme one* as projectile traveling thru atmospheric pressure at Earth escape velocity. - That is a much more complex problem than I think anyone has accurate calculation ability for as surely, not only is there extreme heating the air, but ionizing of it too and radiative transfer of energy to consider also. Conceptually that extreme shock may even generate secondary optically driven shocks in the air by the optical "blast wave" the primary shock radiates!

I am reminded of some wisdom I heard once and hope you don't find it insulting too: One does not need to eat all of a rotten egg to know it is rotten.

* As I expressed in first reply, I am also much to lazy to mathematically destroy your "rotten egg" idea. I simply referred to some of the major and obvious reasons why it is a "non-starter" in my first reply. If pushed hard enough, I can get insulting if you want.

9. ### EnmosRegistered Senior Member

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Dark side of the sun? Ahem...

Anyway, you don't have to decellerate the rocket if isn't going fast in the first place.
Just bring all the nuclear waste into orbit, then 'nudge' it 'directly' into the sun.
Make sure to avoid coming too close to the other planets

I like Billy T's idea; drop it near a subduction zone.
One thing though, you better hope no vulcanoes will form there.

10. ### Mathers2013BannedBanned

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The radiation from the spent rods will reach Earth and kill all life on the planet. You're sending nothing into Solaris!

11. ### Janus58Valued Senior Member

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The point is that anything we launch from Earth is already "going fast" relative to the Sun because the Earth is moving ~30 km/sec as it orbits the Sun. Anything we launch will share this velocity. To "nudge" it so that it will hit the Sun you have to get rid of most of that speed, otherwise it just goes into orbit around the Sun like the Earth does.

12. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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There is no hot magma near surface at a subduction zone. That is found near or at the surface where mass is rising from the interior, like along the mid Atlantic ridge or the Hawaiian island chain. etc. I. e. it takes a long time for the surface temperature material moving ever deeper into the Earth to become even red hot. Think of them as "cold fingers or ridges" falling down and getting much deeper than the average solid crust thickness before they melt.

BTW, Janus58 is fully correct. In these things he always is. I have learned from him. Initially I argued with him when he stated the moon is ALWAYS curving towards the sun as it moves. I falsely thought that could not be true when moon is in the new moon phase, but it is.

13. ### EnmosRegistered Senior Member

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43,184
Well, isn't that velocity perpendicular to the imaginary line between the earth and the sun?
I mean, the rocket (or perhaps container is a better word to use here) won't be rushing off towards the sun because of the earths orbital speed.

14. ### EnmosRegistered Senior Member

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Ah ok. Thanks

15. ### billvonValued Senior Member

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Doesn't work.

A lot of people have this image that the Sun is a huge gravity well that will "suck" anything nearby into it. Doesn't work like that. That's why comets very rarely hit the Sun, and that's why planets/asteroids/ring materiala don't fall into the Sun over billions of years. It really is harder to reach the Sun than to escape the solar system completely.

I think you hope for volcanoes. Dilute the waste in a million tons of magma, and when it solidifies it's just rock. A billion years from now Earth's next civilization will mine the rock for uranium ore.

16. ### Janus58Valued Senior Member

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That's kind of the point. Since this velocity is perpendicular to the orbital radial, you have to get rid of almost all of it before you can fall into the Sun. The Earth doesn't fall into the Sun due to this orbital velocity. Anything we launch from the Earth also starts with this same orbital velocity.

17. ### EnmosRegistered Senior Member

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I see. I feel stupid now..

18. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Don't. You learned, unlike several posting here who don't, but remain ignorant and stupid.

I'm not sure I can speak for Janus58, but types like you are my main reason for posting science here. So I thank you for rewarding me.

19. ### NMSquirrelOCD ADHD THC IMO UR12Valued Senior Member

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"Obviously your just blowing smoke without any facts. "
ok, accepted it wasn't meant for an insult. sorry.

so you are saying it is easier to send a multi ton rocket into space than a 55 gallon drum? (55 gallon drum just an example of potential package size(with magnetic rail gun))
this example you give is just to get it in orbit?

I wont argue the math, I will accept your interpretation since anyone is better at the math than I,(and you seem to be in the field) but to me it seems it would be easier(more cost effective?) to send a 55 gallon drum than a multi ton rocket.. shape the drum like a rocket and the same forces that act on it should be the same as a multi-ton rocket except less so.
(notice, I do not say it is)

one does not know the egg is rotten until one cracks it open.

20. ### exchemistValued Senior Member

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I think the point is that with a rail gun all the impulse to the projectile must be given to it before it reaches the end of the gun. So what he's saying is you would have to end up giving it a full Earth escape velocity while it was still in the atmosphere. Clearly this is impractical, as atmospheric drag, at the speeds required, would be ginormous.

Whereas with a rocket, you give your projectile the impulse progressively over quite a long period, rather than all at once, and even more importantly a lot of the acceleration to achieve escape velocity can be done in space, i.e.once it is out of the horrendous drag imposed by the atmosphere.

21. ### NMSquirrelOCD ADHD THC IMO UR12Valued Senior Member

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ok..i think I get this..

say a rocket requires X amount of force to travel, say 1 mile, then to achieve orbit the rocket would require Y miles to achieve orbit (dunno how many) so it would require X times Y force to get into orbit,
when a rocket carries its fuel with it, that energy can be dispersed over the period of the flight time rather than all at once as a magnetic rail gun.(im thinking baseball bat vs balloon rocket)

are they any closer to building a space elevator yet?

then a rail gun would work if it was in orbit correct?
(you just said that....)

22. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Not very well or cost effective as momentum is conserved. I.e. the momentum given to the waste projectile to send it away from earth smashes the rail gun back into the earth. - A one shot system with a very costly gun and energy system to "re-build" and lift back up into orbit. Conceptually this problem could be solved with two identical waste packages fired in opposite directions from the central part of the rail gun, but only one of them could lose the Earth's speed about the sun to fall into the sun. The other goes into an earth crossing elliptical orbit, but what the hell, probably will not hit earth for a million years.

If you could build a rail gun from material already on the moon, that would probably be the best, re-useable launcher to throw things off the moon as no fuel needs be ejected from rear end of the rocket - only energy required. It has been suggested and studied long ago for this use.

23. ### billvonValued Senior Member

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And if you could get the waste there. And power the rail gun somehow. And have rockets (or other railguns) firing the opposite direction to deal with the reaction.