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

[billvon]

So your saying that a trajectory of a rocket could not be made that the gravity of the sun , on the side of the sun away from us , would not draw this rocket in ?

No. Basic orbital mechanics. It's like saying the Moon should crash into the Earth any day now because the Earth's gravity will inevitably "draw the moon in."

I find that hard to believe

Do the math.

So are you saying that we could not compensate for the torque ?

Sure we could. It would take a huge rocket carrying tons of fuel to take even a little nuclear waste, but you could do it.

We can send satellites , space craft , the shuttle , etc. But could not send a rocket to the sun , on the opposite side of the sun which we don't see !!

?? What does whether you can see it or not have to do with anything?

 

[river]

Originally Posted by river
So your saying that a trajectory of a rocket could not be made that the gravity of the sun , on the side of the sun away from us , would not draw this rocket in ?

No. Basic orbital mechanics. It's like saying the Moon should crash into the Earth any day now because the Earth's gravity will inevitably "draw the moon in."

This makes no sense

Your comparing the moon to a rocket fired in the direction of the sun that is away from us , with the trajectory of eventually entering the suns corona

Hmmmm....

 

[billvon]

Your comparing the moon to a rocket fired in the direction of the sun that is away from us , with the trajectory of eventually entering the suns corona

Both will follow their own trajectories based on the laws of orbital mechanics - unless you change them. The Earth will not "draw" the moon in any more than the sun will "draw" a rocket in.

If you want to hit the Sun you have to kill enough orbital velocity to make it possible to reach the surface. That's about 30 km/sec from low Earth orbit. By comparison you need about 4.3 km/sec to reach Mars orbit from low Earth orbit.

That means that it is way, way easier to reach the surface of Mars than to reach the Sun. You'd need a Saturn-V sized launcher to send even a few hundred pounds of waste into the Sun. If you had the output of one reactor to deal with for a year you'd have 20 tons of waste. So you'd be looking at 200 launches of a Saturn V a year - almost one per day - to deal with the waste of just ONE nuclear power plant.

Of course we don't have that kind of money. But let's say we did. I'd much rather launch it all towards Mars and send along some tiny bits of additional cargo, like say people, habitats, food and water, tractors, tents, solar power systems, reactors, Sabatier units etc etc. Overall it would be a lot cheaper since it takes much less delta-V to get to Mars; you could launch twice the waste per launch and STILL have plenty of room for people and equipment.

And with four supply runs a week, you could support a colony of thousands. I bet they'd even bury that waste for you.

 

[river]

Both will follow their own trajectories based on the laws of orbital mechanics - unless you change them. The Earth will not "draw" the moon in any more than the sun will "draw" a rocket in.

If you want to hit the Sun you have to kill enough orbital velocity to make it possible to reach the surface. That's about 30 km/sec from low Earth orbit. By comparison you need about 4.3 km/sec to reach Mars orbit from low Earth orbit

.

You don't have to reach the sun's surface

Just the corona

 

[queeg]

Both will follow their own trajectories based on the laws of orbital mechanics - unless you change them. The Earth will not "draw" the moon in any more than the sun will "draw" a rocket in.

If you want to hit the Sun you have to kill enough orbital velocity to make it possible to reach the surface. That's about 30 km/sec from low Earth orbit. By comparison you need about 4.3 km/sec to reach Mars orbit from low Earth orbit.

That means that it is way, way easier to reach the surface of Mars than to reach the Sun. You'd need a Saturn-V sized launcher to send even a few hundred pounds of waste into the Sun. If you had the output of one reactor to deal with for a year you'd have 20 tons of waste. So you'd be looking at 200 launches of a Saturn V a year - almost one per day - to deal with the waste of just ONE nuclear power plant.

Of course we don't have that kind of money. But let's say we did. I'd much rather launch it all towards Mars and send along some tiny bits of additional cargo, like say people, habitats, food and water, tractors, tents, solar power systems, reactors, Sabatier units etc etc. Overall it would be a lot cheaper since it takes much less delta-V to get to Mars; you could launch twice the waste per launch and STILL have plenty of room for people and equipment.

And with four supply runs a week, you could support a colony of thousands. I bet they'd even bury that waste for you.

ehhh what are you on about? the sun is the easiest target to hit! in fact when we sent out space probes we try not to hit it by means of planetary slingshots. there is no law or orbital mechanics that says an object automatically goes into orbit when fired at a body. we are in an elliptical orbit, the same direction the solar system was spinning when it formed, as is the moon orbiting as it accreted in orbit, it wasnt shot straight at us.

 

[billvon]

You don't have to reach the sun's surface . . .Just the corona

Almost the same energy. And the last thing you want is to vaporize the stuff - and then have it return on its trajectory to the orbit of Earth.

 

[billvon]

ehhh what are you on about? the sun is the easiest target to hit! in fact when we sent out space probes we try not to hit it by means of planetary slingshots.

No, we don't. No one has ever come close to "accidentally" hitting the Sun, nor is it a realistic threat to any of our spacecraft. During the Messenger mission we tried to get close to the Sun (i.e. the orbit of Mercury.) To get there directly via a simple orbit would have taken 22 km/s delta-V, close to what we would need to get to the Sun. By doing a very large number of flybys (one of Earth, two of Venus, and three of Mercury) they managed to get it down to 13 km/s.

there is no law or orbital mechanics that says an object automatically goes into orbit when fired at a body.

Correct. Nor is there a law that says "things just fall into the Sun really easily." The laws of orbital mechanics, however, do prevent you from just going wherever you want without regard for required delta-V.

 

[river]

Almost the same energy. And the last thing you want is to vaporize the stuff - and then have it return on its trajectory to the orbit of Earth.

So your telling me that there is no way to fire a rocket to the darkside of the sun and have it vaporize so that it won't return to the Earth ?

Then we had better get better at our understanding of why not and then get to the point of we can

 

[exchemist]

No, we don't. No one has ever come close to "accidentally" hitting the Sun, nor is it a realistic threat to any of our spacecraft. During the Messenger mission we tried to get close to the Sun (i.e. the orbit of Mercury.) To get there directly via a simple orbit would have taken 22 km/s delta-V, close to what we would need to get to the Sun. By doing a very large number of flybys (one of Earth, two of Venus, and three of Mercury) they managed to get it down to 13 km/s.



Correct. Nor is there a law that says "things just fall into the Sun really easily." The laws of orbital mechanics, however, do prevent you from just going wherever you want without regard for required delta-V.

Deleted

 

[exchemist]

So your telling me that there is no way to fire a rocket to the darkside of the sun and have it vaporize so that it won't return to the Earth ?

Then we had better get better at our understanding of why not and then get to the point of we can

Billvon,

you're making a noble effort, but you're being suckered. River is doing what he habitually does, which is to play deliberately obtuse, to get a rise out of the science community. The crack about the "dark side of the sun" is a typical example. He would have been laughing up his sleeve as he typed that.

As you point out out each of his "misunderstandings", he will introduce new ones, each more egregiously stupid than the last. You will never get to the end of it, as he does not give a fuck about helping people understand anything but just wants to keep an argument going for its own sake, no matter how idiotic - in fact, the more idiotic the better.

 

[Billy T]

So are you saying that we could not compensate for the torque ?

Net torque is required. If you like you can think of the reduction of angular momentum as reduction of the Kinetic Energy you have with respect to referece frame of the fixed stars while sitting in your chair, to that of an object in a highly elliptic orbit at its 1AU apogee. I.e. give the nuclear waste rocket an orbit with apogee of 1 AU and perigee equal to the sun's radius, not the nearly circular 1AU orbit is has when sitting on the launch pad. If it is easy to do, I'll compute how much work is required and edit this post.
By Edit: Must essentially stop all its forward orbit speed:

Following is my “stream of thought” approach to problem of computing how much work must be done to send each unit of mass into the sun. Answer, I think correct, is you must remove essentially 100% of the kinetic energy the Nuclear Waste Rocket had just sitting on the launch pad.

Taking Earth to be in a 1 AU circular orbit the KE = 0.5|PE| and in some strange, but convenient “Billy T scale (BT units) is: 0.5M[2pi(1AU)/365]^2 which I then “normalize” per BT unit of mass to have the PE = -2 and earth's KE =1.

The radius of the sun, is: 0.00464913034 AU (Ain't Google wonderful) but I'll call it 0.00465 and note gravitational potential is inverse linear. Thus the PE falls from -2 down to -2 / 0.00465 = -430. (in TBs units, normalized of course) from what the slowed down nuclear waste rocket, NWR, had at 1 AU apogee and it gains 238 units of KE in the “fall” down to perigee.

Now since PE is always defined wrt some arbitary zero point, and I have the KE at perigee known to be increased from the tiny value it had at 1AU apogee (after slowed down form Earth's orbit speed) which I'll guess was 0.3, so I can redefine the PE at 0.00465Au to be zero (and must add 430 units of energy to all previous values given.)

Thus the PE at apogee of the elliptical orbit NWR's unit of mass with new zero at 1 AU is -2 + 430 = 428 and by guess of 0.3 for the KE there, the total energy there is 428.3, but it is constant (until drag in the solar corona takes effect). Thus the work done, W, per unit mass to slow each unit of mass of the NWR down from Earth's orbital speed, to the elliptical orbit apogee's speed is W = 428.3 – 428 = 0.3, my guess returning. I. e. 70% of the KE it had on Earth must be removed by work slowing it down, but this is only a guess.

To do it more correctly we need to calculate the KE the “slowed down” NWR had at 1AU. This can be done by noting the elliptical orbit sweeps out equal areas each micro second everywhere in it orbit.It had KE = ~428 at perigee. I. e. the travel distance in a micro second at 0.00465AU is 430 greater (by faster speed) than at 1AU and the KE at perigee is 430^2 = 184,900 times greater. Thus instead of having KE of 1 when on the launch pad, The NWR must have essentially all it KE removed by the work done! Not my guess of only 70%

 

[billvon]

So your telling me that there is no way to fire a rocket to the darkside of the sun and have it vaporize so that it won't return to the Earth ?

Yes, there is. As I mentioned, it would take a Saturn 5 sized launcher to get a few hundred pounds to the Sun. We'd need almost a launch a day for every nuclear power plant on Earth. There are currently about 400 operating nuclear reactors on the planet, so we'd need about 200 launches a day, or one Saturn 5 launch every 7 minutes. In today's dollars a launch cost $7 billion - so that would be $560 trillion dollars a year for the launches. As a comparison, the GDP of the world (i.e. the total economic output of everyone on the planet) is about $70 trillion.

Now let's say those launchers were 99.99% reliable (in other words, way more reliable than any modern launcher.) That means that eight payloads of nuclear waste a year would come crashing back to Earth at a fairly random location. Are you sure you want eight dirty bombs a year falling on the planet?

 

[Russ_Watters]

Dark side of the sun...?

Anyway, there is a simple way to explain this:
Earth's orbital speed is about 30km/s, so in order to fire an object toward the sun, it has to leave earth with a velocity of 30 km/sec in the other direction (as viewed from earth). That's a lot of speed.

 

[Billy T]

... Earth's orbital speed is about 30km/s, so in order to fire an object toward the sun, it has to leave earth with a velocity of 30 km/sec in the other direction (as viewed from earth). That's a lot of speed.

Yes that will certainly work. Then the Nuclear Waste Rocket, NWR, can fall straight line radially into the sun, but one only needs to remove almost all of the earth's orbital speed and that takes less energy than 100% removal. It let it keep the orbital speed of a very elliptical orbit, one with apogee of 1 AU and perigee of 0.00465AU. My quick and crude evaluation of this OK residual speed was surprisingly small, meaning , if correct there is little energy saving for the simple direct radial fall to the sun.

Earth is not in a perfectly circular orbit, so when you launch seems to be more important than whether sun eats it on side visible at launch or on the exact opposite side. I.e. for least energy required, the launch is at local "high noon" on earth Apogee day for a collisions with the then current far side of the sun.

But again, for about 100,000 less energy and 100 times less life cycle cost and much greater safety do what I suggested 5+ years ago and repeated in first half of post 34 of this thread.

 

[Russ_Watters]

Yes that will certainly work. Then the Nuclear Waste Rocket, NWR, can fall straight line radially into the sun, but one only needs to remove almost all of the earth's orbital speed and that takes less energy than 100% removal. It let it keep the orbital speed of a very elliptical orbit, one with apogee of 1 AU and perigee of 0.00465AU. My quick and crude evaluation of this OK residual speed was surprisingly small, meaning , if correct there is little energy saving for the simple direct radial fall to the sun.

Yes, of course it needn't fall directly into the sun, just almost directly -- passing within the radius by the time it reaches perihelion. It was just an easy to explain illustration and I figured 99% accuracy was close enough.

I do think some of the criticism of the OP's idea is misguided, since it assumes that a failure of the rocket would result in dispersion of the radioactive material and that such an event would have significant negative consequences, neither of which are likely. We already send nuclear material into space and encapsulate it in such a way as to virtually guarantee it surviving re-entry. So that would just require making the rocket a lot heavier, further increasing the cost.

 

[queeg]

No, we don't. No one has ever come close to "accidentally" hitting the Sun, nor is it a realistic threat to any of our spacecraft. During the Messenger mission we tried to get close to the Sun (i.e. the orbit of Mercury.) To get there directly via a simple orbit would have taken 22 km/s delta-V, close to what we would need to get to the Sun. By doing a very large number of flybys (one of Earth, two of Venus, and three of Mercury) they managed to get it down to 13 km/s.

.

What i meant by this was that we require a lot of rocket power to get our probes to escape the suns pull, using slingshots as well as fuel. whether it hits it or not, if we don't have the velocity, then the sun will eventually pull it back. i didn't mean we have to dodge the sun

If the operation went ahead to send all this waste to the sun, it would most certainly work. they would disintegrate a long way before reaching the sun, but hypothetically it had to strike the suns surface to be destroyed, it would still work, we've proven with space probes that we can crash into other spacial bodies.

 

[billvon]

What i meant by this was that we require a lot of rocket power to get our probes to escape the suns pull, using slingshots as well as fuel. whether it hits it or not, if we don't have the velocity, then the sun will eventually pull it back.

Correct. Ironically, it takes far more fuel to actually hit the sun than to escape it forever.

If the operation went ahead to send all this waste to the sun, it would most certainly work. they would disintegrate a long way before reaching the sun, but hypothetically it had to strike the suns surface to be destroyed, it would still work, we've proven with space probes that we can crash into other spacial bodies.

Yes, we could make it work. As mentioned before, though, it would cost half a quadrillion dollars a year. It would make as much sense as solving our sewage problems by building a big pipe between the Earth and the Moon and pumping it all there.

 

[NMSquirrel]

um guys.. Rail guns.. not rockets

waste would only be in container and shot into space, only weight is container.

 

[Billy T]

um guys.. Rail guns.. not rockets - waste would only be in container and shot into space, only weight is container.

Too lazy to try to compute the atmospheric energy loss due to shock wave from a Mach > 50 projectile, but there is a reason why rail guns are not used - not even to resupply the low earth orbit manned space station much less even send robot to Mars which energetically must be (guessing) at least 20 times less energy required than to go to the sun per Kg sent. All that energy must be in the waste package when it leaves the end of the rail gun, probably at more than Mach = 100 ! (I'm falsely assuming it does not just totally vaporize before leaving the Earth's atmosphere but think that is highly probable. The leading edges of fighter wings that go Mach = 3 are titanium* as aluminum would melt.)

Also, a rail gun (guessing) 20 miles long with 90+ % of the travel distance super sonic pointing up at least for the last few miles, I'll bet exceeds NASA's total annual budget in cost. Obviously your just blowing smoke without any facts.

*BTW the old USSR learned how to work titanium for wings before the US did; Why in the Korean war, the Migs could just run away from the more highly trained / skilled pilots of US fighters. Their better / more advanced technology was sort of embarrassing to the US so few knew that - just calling them "commee cowards" was better PR. The Chinese pilots of those Russian Migs were under strict orders: Fly higher than US jets could, and when seeing US jet dive on it firing all you can then turn tail and run for the Yalow river border with China. Not much training was required for that.

Heating wings, not jet thrust, has long been the limit of fighter speed (but of course little need to include a rocket jet than can melt your wings off in level flight. Full after-burner thrust is used for no more than quick maneuver of a few seconds duration.) Most Chinese pilots did obey their strict orders, but a few did not. They dropped down without a shot fired to level, wing-wagging flight below the US jets and were escorted to a US controlled air field - how US learned about their superior technology and more importantly about some of their flight limitations of the Migs that let the kill ratio turn sharply in the US's favor. They were well paid in gold. More than enough to buy a small business in San Francisco's "China town" with their new US created IDs etc.

 

[Arne Saknussemm]

How about this: we sit on nuclear waste until interstellar travel becomes commonplace. Then responsible parties gradually dispose of miniscule portions of it every time a ship leaves the Solar system. Wouldn't there be La Grange points between stars where small portions could be left? No one ship would ever have to transport more than a 'handful' - securely contained of course. Eventually all the waste would be gone. I'm assuming we won't be producing even more nuclear waste in the interstellar age.