But it does affect the type and volatility of the chemical compounds which contain the radioactive elements. Uranium tetrachloride for example has a boiling point of 148.5 °C. That’s not a gas that you’d want to have bubbling out of your lava flows.
Heh heh … and if I recall correctly, the title of the essay he proposed this in was “Yet Another Modest Proposal: The Roentgen Standard,” which gives an indication about his seriousness.
If you launch a spacecraft at a slow speed relative to the earth, it’ll still have most of earth’s orbital speed, close to 30 km/s. It will get pulled by the sun, but the spacecraft is moving fast enough that centrifugal force keeps it away from the sun. If you want the spacecraft to fall into the sun, you have to kill the orbital speed and let the gravity win.
That’s one way, but it’s not the only way. I think you’re stuck in the “deorbit” mindset.
Read Squink’s post. If you can fire the rocket fast enough towards the sun, the amount of lateral drift (I guess that’s what I’d call it) won’t be significant enough to matter.
Now of course, this requires that the “towards the sun” velocity has to be VERY large with respect to earth’s orbital velocity. This in turn makes this approach completely impratical. That’s cool, I understand and accept that. What I don’t agree with is the idea that there’s some kind of physical law requiring us to kill all of earth’s orbital velocity. That’s a practical constraint, not a fundamental physics one.
-Ben
I’m just not in the mood to argue with anyone on a personal level today, so I’ll just make a general statement to the thread that will be obvious to all but a few of us, you’ll know who you are.
There is no such thing as centrifugal force.
Buy a physics book. Look up tangential acceleration. Read. Learn. This thread will be so much more relevant to you then, and your answers will seem so much less intelligent. Your condescending tone will be revealed to you as the misguided thought that it is.
Once again, most of you are well above the level of this comment. The rest of you are making my head hurt worse than it does already.
I can’t wait until my GF takes physics this summer, and I have to explain all this shit again.
Another thought in a remotely related topic:
The Mercury MESSENGER mission will take five years to achieve orbit, after two Mercury flybys and two Venus flybys.
It doesn’t take nearly that long to send a probe to Mars.
I’m going to have to nitpick here. I’m pretty sure that temperature doesn’t affect radioactivity, period. If it did, we’d just throw it all in the fridge. A very cold, very secure fridge.
Dropping straight in requires killing off all orbital velocity. Merely lowering the orbital velocity gets you a spiral orbit that ends in the Sun. The more you brake, the faster you close in the on the Sun and the sooner your rocket gets there. More braking=faster fall=impact sooner. If you don’t care how long it takes, you just brake it a little and let it take a couple of hundred years to hit. Of course, you could just dump the stuff into a permanent orbit, instead. It would work out the same for all practical purposes.
To hit the Sun in the shortest time from the Earth, you have to brake laterally (against the Earth’s orbit) and accelerate towards the Sun. If you simply point at the Sun and accelerate, your motion in the direction of the Earth’s orbit will carry you right on past.
PS:
You tell 'em, Metalhead.
Send it into Venus instead…much easier. 
Seems like, if time wasn’t a factor, your best bet would be a slingshot trajectory to get it into the sun…
-XT
Oh sure , and in the year 1999 the moon will suffer a calamity and fly off into the ether taking the small band of humans with it.
Declan
Why don’t we put the waste in that vehicle that goes to the center of the Earth? It also helps restart our magnetic field. 
As Dr. Matrix already implied, without friction, or constant acceleration, there is no such thing as a spiral orbit.
Nope, all you have to do is get your rocket going fast enough towards the sun that the lateral velocity does not carry it past the disk by the time you get there. That turns out to be very fast (~7.4 million mph), but it could be done without lateral braking.
Since the earths orbit is ~circular, and the orbital vector always lies on the tangent to the circle, the problem of hitting the sun directly is always (at any point in earth’s orbit) equivalent to the problem of hitting an object which you are passing in straight line movement, by throwing at the exact instant of closest approach.
The point of a slingshot is to get you there faster. A slingshot involves setting your trajectory to loop around another planet in order to gain velocity from the gravity field of that planet.
Thats not always true. You can use a slingshot and aerobraking to slow down as well as speed up. Its all in your angle of attack to the gravity well you are approaching. Even speeding up you can still change your trajectory to hit the sun though with a slingshot. I’ve seen various trajectories (its been a LONG time since I took aerospace engineering in college so don’t quote me on any of this) for getting things to various places…including the sun. If I’ve not lost too many brain cells over the years, I seem to recall that the easiest way to hit the sun from the earth was a slingshot involving several of the planets. It wouldn’t be the fastest way, but it was the easiest…again, as I recall.
I still say send it to Venus…its a lot easier to get there.
-XT
As has been said, getting directly to the sun requires a lot of energy. It takes less energy to go out to Saturn and slingshot back towards the Sun.
I could see how the prospect of throwing something at the sun could be difficult, but with a rocket it should be no problem.
Point it at the sun, set the rocket to “slow and steady” and it will make it there eventually along a spiral path.
Without a rocket that can apply force throughout the entire journey, you’d just have to angle your shot to compensate for the earth’s tangential momentum. It’s not as easy as firing off in a general direction, but I don’t think it would be that difficult either. Basically you’re just trying to make the eliptical orbit path that you’re sending the garbage down as thin as possible. So thin that the path passes through the outside of the Sun.
Read the freaking thread man. i hate it when people keep repeating the same misinformation which was just debunked in the thread. Or am I being whooshed here?
Here is I think the real explanation, gathered from a textbook of mine. It discusses a mission to Venus, but the only difference between that and the sun is the size of the orbit.
Think about it - all you really need to do is to set the garbage ship in an elliptical orbit around the sun, with a peri-sol (closest point to the sun) of less than the radius of the sun. It doesn’t have to hit dead-on.
From the book, “Going to Venus is like going to Mars except that Venus’s orbit lies inside Earth’s orbit. Therefore, the vehicle must be accelerated to escape velocity on a hyperbolic trajectory from Earth, but in the direction opposite to the direction of Earth’s motion. Its speed with respect to the Sun is then less than Earth’s speed and it moves into a smaller transfer orbit toward the inner planets.”
So this should be a pretty simple calculation for NASA types. Since the radius of the sun is about 700,000 km, all you do is pretend there’s a planet orbiting at some distance less than that and pretend you’re trying to get into orbit around it. Then the garbage ship will hit the sun.
Yes, it would still take a lot of energy to get to escape velocity, but it could be done, depending on how much garbage you’re sending up. Note that you do not have to cancel the forward speed of the Earth either, just get to escape velocity in the direction opposite of the Earth’s direction of travel.
This is wrong on so many levels.
First of all, as has been stated before, there is NO SUCH THING as a spiral orbit. Nope. Physically impossible. You canna change tha laws o’ physics, man! All orbits are conic sections. That means they are ellipses (circles being a special case of ellipse), parabolas, or hyperbolas. An ellipse describes the motion of the earth. A parabola describes the motion of a baseball thrown up in the air. And a hyperbola describes the motion of an object that enters the solar system, is affected by the suns gravity, but has so much velocity that it leaves the solar system anyway.
I think we have a fundamental lack of understanding about how orbits work. Lets take the example of the earth around the sun. The earth is affected by the sun’s gravitational field. We are constantly falling towards the sun. In fact, we are screaming towards the sun, at a very high velocity. So why don’t we fall into the sun? Well, we also have a sideways velocity relative to the sun. We keep falling towards the sun, but the sideways velocity keeps making us miss. In fact, the two speeds are exactly matched. That’s what keeps us in a circular orbit. But what if we slowed down the earth’s velocity? Would the earth fall into the sun then? No. It would fall towards the sun, but STILL miss. It would be in an elliptical orbit (or precisely, a more elliptical orbit). The orbit would look like the orbit of a comet…it would have one end where the orbit of the earth is now, the other end would be closer to the sun. But it would never hit the sun, unless you killed the velocity so much that the close end of the orbit was inside the corona of the sun. That would essentially mean killing all of the orbital velocity of the earth.
You would have to kill ALL of earth’s orbital velocity to hit the sun. Killing part of it just means you are in an elliptical orbit.
Now, why can’t you just turn on your rocket, and start accelerating? Because rockets require fuel. Rockets can’t just thrust forever. Rockets require reaction mass. Rockets work by throwing very hot gasses at very high speeds out the back of the rocket. For every molecule of Hydrogen you throw out the back, your rocket flies a little faster in the exact opposite direction.
But why can’t you just thrust forever? Because once you’ve thrown your last molecule of hydrogen overboard, you’re finished. You can’t accelerate anymore. Well, why can’t you just get a bigger fuel tank? Because that fuel tank will make your rocket heavier. And that means it will take a lot more fuel to move your rocket. You would be expending most of your fuel simply to move around your giant fuel tank. Think of the Saturn V rocket. The whole thing is filled with rocket fuel, and all it can do is lift the Apollo modules out of Earth orbit.
The rocket itself has mass. The fuel has mass. The speed of the reaction mass is constant. Therefore, every rocket has a fixed amount of delta-v, or change in velocity. This is given by those three numbers. To increase delta-v you have to change one of the numbers. You get the highest thrust engines you can find. You get the lightest rocket you can find. You pack it with as much fuel as you can. And that’s that. You can’t change your velocity past that number, barring gravitational slingshot tricks.
Our current rockets don’t have the delta-v to cancel their solar orbital velocity and fall into the sun. You can’t add more fuel in space. You can’t “spiral” into the sun. You could do some fancy tricks, like launch the craft into an elliptical orbit that brings it back to earth a few years later, at the exact spot that will kill it’s solar orbital velocity. They did the same trick with Cassini (only in reverse) a few years ago, and there were massive protests, since Cassini was using plutonium to power its electrical systems.
The bottom line, when you are traveling around the solar system, you can’t just point your rocket at the target, put the engines on full, and blast till you get where you’re going. Your target is moving, your ship is moving, you have limited fuel always. You have to use your limited fuel to change your current orbit into a new orbit that will intersect where your target is going to be when you eventually arrive there. And ironically, the center of the Sun is the most difficult place in the Solar System to get to. It would be easier to head for interstellar space, like Pioneer is doing.
The sun is very small compared to the orbit of the earth. Grazing the sun’s surface and hitting it dead on aren’t very different in terms of required energy. The minimum delta-V (change in velocity) required to get to the sun is still very close to 30 km/s. By the way, nobody is saying it’s impossible. It’s just insanely expensive.
If you point a rocket at the sun and launched at a very fast speed, yes it would hit the sun. But the delta V required for that is far greater than 30 km/s, by an order of magnitude or more. The most efficient way to get to the sun is the “deorbit” mentality, i.e. killing the orbital speed and dropping to the sun.
And someone said there is no such thing as centrifugal or centripital force. Nonsense. They are virtual forces, true, but in certain circumstances it makes sense to treat them as actual forces. Magnetism isn’t a real force either, it’s simply electrical foce that behaves differently because of Lorentz contraction, but nobody uses relativity to calculate the force between two magnets. You treat magnetism as an actual force. It’s simple snobbery to say “it’s not real!” every time someone mentions centrifugal or centripital force.
Lemur866 and sailor - please work on your reading comprehension.
If you could make a rocket that can apply some amount of constant accelerative force to our garbage scow for the entire length of the journey to the sun, then you CAN easily send something down a spiral path to the sun. I thought I made that clear by saying “set the rocket to slow and steady” and then right after that I said “Without a rocket that can apply force throughout the entire journey” but I guess you somehow didn’t understand that. I said nothing about spiral orbits and I did read the freaking thread.