> To reach the Sun you need to subtract 100 percent of Earth’s orbital velocity; to reach solar escape velocity you need only add 41 percent to it.
You could send the waste with near solar escape velocity to travel on a really long ellipsis trajectory, at the furthest point you can get rid of the remaining kinetic energy with minimal fuel and let the waste fall back straight into the Sun. Subtracting Earth's orbital velocity is by far not the optimal method to reach the Sun.
A straight Hohmann transfer requires ~0.5-1% more dV than a bi-elliptic transfer. Calling this "by far" not optimal is by far not correct. So instead of 32 km/s you need 31.68 km/s. This changes nothing.
To what end? To spend literally decades, perhaps centuries, with nuclear waste floating around the solar system? Why not just leave it in deep space to start with? Why bother sending it into space in the first place?
Meanwhile, if you succeed in sending nuclear waste into the Sun what do you think happens to it? It doesn't go away, it just gets vaporized and then scattered into the solar wind.
Your "trick" doesn't change any of the conservation of angular momentum considerations in the article.
To "get rid of the remaining kinetic energy" would only result in the object getting escape velocity relative to earth. The object would never have "stopped" relative to it's orbit around the sun but even at it's further point would be traveling with fairly close to the same angular velocity as the earth (as described in the article etc).
I always thought the biggest reason was that if a rocket carrying nuclear waste exploded in our atmosphere, it would be catastrophic. It's a lot less risky to just bury it underground and pray it never leaks.
The author acknowledges the existence of that argument, but then insists that the "real objection" is difficulties in orbital trajectories. I'll believe that's the real objection if we start considering sending nuclear waste on a comparably simple orbital journey into outer space.
Or bury the nuclear waste in oceanic trenches. It is out of the way and future generations won't stumble upon it when humans forget where they buried all this stuff.
In particular, pyroprocessing (http://www.cse.anl.gov/pdfs/pyroprocessing_brochure.pdf), which can separate out all actinides forming the bulk of nuclear waste. The actinides can continue to be used as fuel in an appropriate reactor, leaving just small amounts of short-lived (<1000 years), highly-radioactive "ash" as nuclear waste. Importantly, non-fissile isotopes such as U-238 are continually recycled so that no energy is left unextracted.
This was nearing completion in the form of the Integral Fast Reactor (http://en.wikipedia.org/wiki/Integral_fast_reactor) at the Argonne National Laboratory, until it was cancelled in 1994 at the behest of President Clinton and John Kerry.
The reason for its cancellation? The belief that any nuclear reprocessing is bad for "nuclear proliferation". I cannot even comprehend the mental gymnastics required to justify shutting down vital research which didn't even produce isolated plutonium when the country possessed thousands of nuclear weapons and tonnes of weapons-grade plutonium. How the fuck would this have any affect at all on "nuclear proliferation"?
That Wikipedia table is interesting, but it is hard to understand who is currently doing what from it. I think Japan is mostly sending their spent fuel to France.
One of the downsides of reprocessing is that it makes plutonium easy to separate out in a form that is good for making nuclear bombs. Therefore it represents a nuclear proliferation risk.
What would happen, if you managed to make sure all this stuff got escape velocity, is you would wind-up with a bunch of junk (literally) in an orbit around the sun that would inherently pass through Earth's orbit - as long as it doesn't have solar escape velocity, once a thing is moving on pure momentum, it is in orbit and since the orbit fairly closely an ellipse so the object will return. As the article mentions, probably not when the earth return to the point. But if you keep throwing stuff "out there", the chances of a return are naturally going to increase.
The biggest problem with the cannon idea is that things traveling at that speed in the atmosphere tend to burn up before getting anywhere. And you get to start in the hardest part of the atmosphere to move in.
Given that the past years have "proven" that it's "perfectly safe" to set off hydrogen bombs in the desert; I think it'd be reasonable to assume that it's quite possible to launch a container of junk into space. Not sur why one would care if it hits the sun or not...
Iff one can make a container that can survive the blast/lift-off -- one wouldn't need to worry about the launch vehicle exploding in-atmosphere: there'd be no rocket fuel. Added bonus: find a way to use existing war heads, and combine with nuclear disarmament...
Even if it were actually difficult to get to the sun, there are other options that are nearly as effective.
Jupiter would be just as good of a dump or we could just launch on an extra solar trajectory. Hell, we could just put it on a large, non-equatorial orbit around the Earth and it would be effectively gone with the added benefit of being able to recover it should we find a reason to. Space is a big enough place to dump an Earth's worth of trash.
The only problems are cost and the risk of explosion during launch.
Ehhh, orbit's not a great idea, especially lower-earth orbit. There's already enough space junk in our orbit right now that we're running the risk of an orbital chain-reaction. The chain reaction could take out most of our satellites. I'm sure radioactive waste in our upper atmosphere wouldn't be a good thing, either.
It could be much lower than that if you take roundabout trajectories with gravity assists from Earth, Venus and Mercury. Not having to establish orbit is definitely a plus.
Besides, nuclear waste is still mostly unburned fuel which could be reprocessed and burned for power in special reactors.
Back in high school I wrote a program that would let you pilot your ship in orbit around the earth and try to dock with things. I discovered just how annoying the physics of spaceflight can be!
Given the magnetic field of the Sun, one wonders if you could use a terminator tether [1] to get the remaining delta-v.
We can make it to Mercury. In fact, putting a spacecraft in orbit around Mercury is made more difficult because of the need to decelerate against the Sun's gravity.
If you look at the Wikipedia page for the MESSENGER mission, you'll see they tackled that problem by using gravity assists from Earth, Venus, and Mercury to reduce MESSENGER's relative velocity with Mercury and allow it to go into orbit. These gravity assists greatly reduced the propulsion requirements.
This is why you'd use gravity braking to do the work for you...
You just have to change direction, not slow yourself down, as long as your path intersects the sun you're done... we have sent spacecraft to the sun... it's not beyond our technical capabilities.
Basically, it's like flying into a banked curve... as long as you're pointed at the Sun when you exit the curve you're going to hit the sun with out needing to bleed 30km/s.
The fundamental reason why it doesn't work is because it's really expensive get stuff into space...
If it was difficult to hit things with large gravitational forces we wouldn't see very many comets in the night sky...
> Basically, it's like flying into a banked curve... as long as you're pointed at the Sun when you exit the curve you're going to hit the sun with out needing to bleed 30km/s.
That's not how it works. You're in the planet's reference frame so you inherit its orbital velocity. Exiting a slingshot in the direction of planet's retrograde (not in the direction to the Sun) you can kill off some velocity, but nowhere near enough to just drop yourself into the sun. You do need to bleed out that 30km/s to actually hit the sun.
> "If it was difficult to hit things with large gravitational forces we wouldn't see very many comets in the night sky..."
The difficulty does not come from the mass of the Sun. It comes from Earth's velocity around it. The waste starts out with that velocity as well. Basically the waste is already in a stable orbit around the sun, and getting it out of that is difficult.
That's not how sailing works. The only reason you can sail upwind in a sailboat on the water is because you have a keel pushing against the water to prevent you from blowing downwind. Essentially, a sailboat sits on the interface between two fluids (air and water) that are moving relative to each other, and abuses that fact to go wherever it wants to. If you couldn't push against the water, or in the extremely unlikely case that the water and wind had identical velocities, you wouldn't be able to sail upwind. (Actually, if the water and wind had identical velocities, you wouldn't be able to sail at all. It would feel like no wind.)
To tie this back to solar sailing, there's obviously no fluid interface in space, so to the extent that solar sailing is possible, solar sailing "upwind" toward the sun is not.
From my understanding, solar wind can only push the payload further away from the sun and there is no noticeable drag in space or the earth wouldn't orbit for very long.
You are probably thinking that you can sail upwind on a sail boat but it isn't the same in space. The boat's keel [1] and general shape keep it going straight which is necessary to sail upwind. That doesn't work in space.
Another factor is that a sail works much like an airplane's wing and isn't really 'pushed' by the wind. This allows the force to be perpendicular to the sail in some cases. To my knowledge (take this part with a grain of salt), solar sails works by receiving momentum as the photons hit. This could only push it away from the sun.
The easiest way to use it might be to apply it in the direction perpendicular to the dumptruck - Sun axis. That way, you don't pick up radial speed, but you do lose orbital speed.
Assuming, that is, that i've understood how a magnetic sail works.
I'm not rocket scientist, but it seems like the author is calculating a decreasing spiral into the sun rather than an impact. Why not slingshot around a planet and barrel into the sun with all of the orbital velocity still intact.
The ~30km/s figure is what you'd need to drop it straight into the sun, no spiraling involved.
Gravitational assists can help, but they can also help you get other places. Getting to the sun would still be ridiculously hard compared to the alternatives.
So, getting to the sun is actually really hard, the earth is moving around the sun at ~30km/sec. For comparison, a satelite in low earth orbit is only moving about 8km sec.
30km/sec is a LOT of velocity change, and you'd need to cancel practically all of it to actually fall into the Sun.
Because if the orbital velocity is intact you will perputally miss hitting the sun. The only way you can hit a thing you are orbiting is to remove all the orbital velocity (well, remove enough of the orbital velocity such that your orbit drops low enough to scrape the surface anyway).
he is describing making it fall into the sun directly (if the 'burn' is instantaneous), or if you like, starting to spiral but then just falling in a straight line.
a slingshot changes orbital velocity... thats the whole point. you are right that it is possible to slingshot into an ellipse intersecting the sun... although setting up that manoeuvre itself would be pretty expensive.
I've been curious about his last paragraph for a while - send trash out into nowhere - and unless I'm being an idiot, it looks like we'd still be paying (at the author's implied Saturn-V costs) ~48 million USD per short ton of waste.
Compare this to Yucca Mountain's current cost of $9b for ~77k short tons of storage (~$117k/sh tn) and it's still pretty awful.
We do get the ongoing benefit of no upkeep and happy NIMBYs for spacebound waste, but there are always the downsides of making a mess in our space-backyard (what will the aliens think when they come to visit? How embarrassing. Almost as bad, what if it comes back a la Futurama or gets in the way of future endeavors) and losing access to that waste if we figure out a means of making use of waste in the future.
It's not that I don't believe the author is correct, but I'm having a hard time picturing why it is true. Imagine a rocket pointed in the exact opposite direction the earth is orbiting. So the rocket starts to orbit the sun slightly slower than the Earth, and so the Sun's gravity would pull it closer and closer every year.
Ok, continuing the argument from the article and not discussing practical methods of waste disposal...
Instead of using chemical rockets for the entire dV how about using a rocket to get into orbit and then using an ion engine driven by solar energy to lose the additional 20km/s? It seems the "fuel" weight required would be significantly less.
Offshoot topic but noting how things we launch from earth already have all the energy they need to orbit the sun, why isn't it really easy to get to earth sun Lagrange points? It seems like we could kind of just float over there since we don't need any additional speed to orbit the sun.
[+] [-] leni536|11 years ago|reply
You could send the waste with near solar escape velocity to travel on a really long ellipsis trajectory, at the furthest point you can get rid of the remaining kinetic energy with minimal fuel and let the waste fall back straight into the Sun. Subtracting Earth's orbital velocity is by far not the optimal method to reach the Sun.
[+] [-] kllrnohj|11 years ago|reply
[+] [-] InclinedPlane|11 years ago|reply
Meanwhile, if you succeed in sending nuclear waste into the Sun what do you think happens to it? It doesn't go away, it just gets vaporized and then scattered into the solar wind.
[+] [-] joe_the_user|11 years ago|reply
To "get rid of the remaining kinetic energy" would only result in the object getting escape velocity relative to earth. The object would never have "stopped" relative to it's orbit around the sun but even at it's further point would be traveling with fairly close to the same angular velocity as the earth (as described in the article etc).
[+] [-] aqme28|11 years ago|reply
[+] [-] notahacker|11 years ago|reply
The author acknowledges the existence of that argument, but then insists that the "real objection" is difficulties in orbital trajectories. I'll believe that's the real objection if we start considering sending nuclear waste on a comparably simple orbital journey into outer space.
[+] [-] cpeterso|11 years ago|reply
[+] [-] tbrownaw|11 years ago|reply
Or we could get over our stupid fear of recycling. The stuff's only hazardous because we haven't taken all the energy out of it yet.
Nuclear fuel reprocessing is performed routinely in Europe, Russia and Japan. http://en.wikipedia.org/wiki/Nuclear_reprocessing
[+] [-] dkbrk|11 years ago|reply
This was nearing completion in the form of the Integral Fast Reactor (http://en.wikipedia.org/wiki/Integral_fast_reactor) at the Argonne National Laboratory, until it was cancelled in 1994 at the behest of President Clinton and John Kerry.
The reason for its cancellation? The belief that any nuclear reprocessing is bad for "nuclear proliferation". I cannot even comprehend the mental gymnastics required to justify shutting down vital research which didn't even produce isolated plutonium when the country possessed thousands of nuclear weapons and tonnes of weapons-grade plutonium. How the fuck would this have any affect at all on "nuclear proliferation"?
[+] [-] maxerickson|11 years ago|reply
La Hague apparently has 1/2 of the global light water reprocessing capacity:
http://en.wikipedia.org/wiki/COGEMA_La_Hague_site
That Wikipedia table is interesting, but it is hard to understand who is currently doing what from it. I think Japan is mostly sending their spent fuel to France.
[+] [-] btilly|11 years ago|reply
[+] [-] kavalec|11 years ago|reply
A solar powered mass-driver could sling a steady stream of pellets from Earth orbit into Solar non-orbit using existing technology.
That being said, burying it deep near the the start of a plate subduction zone makes at least as much sense.
[+] [-] kzrdude|11 years ago|reply
[+] [-] joe_the_user|11 years ago|reply
What would happen, if you managed to make sure all this stuff got escape velocity, is you would wind-up with a bunch of junk (literally) in an orbit around the sun that would inherently pass through Earth's orbit - as long as it doesn't have solar escape velocity, once a thing is moving on pure momentum, it is in orbit and since the orbit fairly closely an ellipse so the object will return. As the article mentions, probably not when the earth return to the point. But if you keep throwing stuff "out there", the chances of a return are naturally going to increase.
[+] [-] btilly|11 years ago|reply
[+] [-] e12e|11 years ago|reply
Iff one can make a container that can survive the blast/lift-off -- one wouldn't need to worry about the launch vehicle exploding in-atmosphere: there'd be no rocket fuel. Added bonus: find a way to use existing war heads, and combine with nuclear disarmament...
[+] [-] parineum|11 years ago|reply
Jupiter would be just as good of a dump or we could just launch on an extra solar trajectory. Hell, we could just put it on a large, non-equatorial orbit around the Earth and it would be effectively gone with the added benefit of being able to recover it should we find a reason to. Space is a big enough place to dump an Earth's worth of trash.
The only problems are cost and the risk of explosion during launch.
[+] [-] ignostic|11 years ago|reply
http://en.wikipedia.org/wiki/Kessler_syndrome
[+] [-] kitd|11 years ago|reply
Sling yer 'ook and take your spent matchsticks with you!
[+] [-] iwwr|11 years ago|reply
Besides, nuclear waste is still mostly unburned fuel which could be reprocessed and burned for power in special reactors.
[+] [-] tsotha|11 years ago|reply
That was my reaction. Future generations will want to use that stuff for fuel. There's no reason to launch it into space.
[+] [-] _ak|11 years ago|reply
[+] [-] ChuckMcM|11 years ago|reply
Given the magnetic field of the Sun, one wonders if you could use a terminator tether [1] to get the remaining delta-v.
[1] http://arc.aiaa.org/doi/abs/10.2514/2.3565
[+] [-] rrss1122|11 years ago|reply
If you look at the Wikipedia page for the MESSENGER mission, you'll see they tackled that problem by using gravity assists from Earth, Venus, and Mercury to reduce MESSENGER's relative velocity with Mercury and allow it to go into orbit. These gravity assists greatly reduced the propulsion requirements.
[+] [-] fleitz|11 years ago|reply
You just have to change direction, not slow yourself down, as long as your path intersects the sun you're done... we have sent spacecraft to the sun... it's not beyond our technical capabilities.
Basically, it's like flying into a banked curve... as long as you're pointed at the Sun when you exit the curve you're going to hit the sun with out needing to bleed 30km/s.
The fundamental reason why it doesn't work is because it's really expensive get stuff into space...
If it was difficult to hit things with large gravitational forces we wouldn't see very many comets in the night sky...
[+] [-] civilian|11 years ago|reply
[+] [-] TeMPOraL|11 years ago|reply
That's not how it works. You're in the planet's reference frame so you inherit its orbital velocity. Exiting a slingshot in the direction of planet's retrograde (not in the direction to the Sun) you can kill off some velocity, but nowhere near enough to just drop yourself into the sun. You do need to bleed out that 30km/s to actually hit the sun.
[+] [-] Crito|11 years ago|reply
The difficulty does not come from the mass of the Sun. It comes from Earth's velocity around it. The waste starts out with that velocity as well. Basically the waste is already in a stable orbit around the sun, and getting it out of that is difficult.
[+] [-] jbert|11 years ago|reply
The solar wind is blowing past, is it possible to "sail" against that at an angle and - over time - dump orbital velocity and so end up in the sun?
[+] [-] rcthompson|11 years ago|reply
To tie this back to solar sailing, there's obviously no fluid interface in space, so to the extent that solar sailing is possible, solar sailing "upwind" toward the sun is not.
[+] [-] fleitz|11 years ago|reply
http://en.wikipedia.org/wiki/Gravity_assist
Basically you loop in front of a planet, and then it slingshots you back to the Sun.
Voila... done.
[+] [-] green7ea|11 years ago|reply
You are probably thinking that you can sail upwind on a sail boat but it isn't the same in space. The boat's keel [1] and general shape keep it going straight which is necessary to sail upwind. That doesn't work in space.
Another factor is that a sail works much like an airplane's wing and isn't really 'pushed' by the wind. This allows the force to be perpendicular to the sail in some cases. To my knowledge (take this part with a grain of salt), solar sails works by receiving momentum as the photons hit. This could only push it away from the sun.
http://www.real-world-physics-problems.com/images/physics_sa...
[+] [-] twic|11 years ago|reply
http://en.wikipedia.org/wiki/Magnetic_sail
The easiest way to use it might be to apply it in the direction perpendicular to the dumptruck - Sun axis. That way, you don't pick up radial speed, but you do lose orbital speed.
Assuming, that is, that i've understood how a magnetic sail works.
[+] [-] foreigner|11 years ago|reply
[+] [-] wcoenen|11 years ago|reply
http://en.wikipedia.org/wiki/Poynting–Robertson_effect
[+] [-] johngalt|11 years ago|reply
[+] [-] Crito|11 years ago|reply
Gravitational assists can help, but they can also help you get other places. Getting to the sun would still be ridiculously hard compared to the alternatives.
[+] [-] TylerE|11 years ago|reply
30km/sec is a LOT of velocity change, and you'd need to cancel practically all of it to actually fall into the Sun.
Way harder than getting to any of the planets.
[+] [-] kllrnohj|11 years ago|reply
[+] [-] jheriko|11 years ago|reply
a slingshot changes orbital velocity... thats the whole point. you are right that it is possible to slingshot into an ellipse intersecting the sun... although setting up that manoeuvre itself would be pretty expensive.
[+] [-] everettForth|11 years ago|reply
tldr; it costs a lot of money to launch mass into space.
Sending 1 pound of water into space costs $50,000. This is more than the price of gold on earth. A space elevator changes the economics dramatically.
[+] [-] bbcbasic|11 years ago|reply
(Assuming gravity assist is used)
[+] [-] WaxProlix|11 years ago|reply
Compare this to Yucca Mountain's current cost of $9b for ~77k short tons of storage (~$117k/sh tn) and it's still pretty awful.
We do get the ongoing benefit of no upkeep and happy NIMBYs for spacebound waste, but there are always the downsides of making a mess in our space-backyard (what will the aliens think when they come to visit? How embarrassing. Almost as bad, what if it comes back a la Futurama or gets in the way of future endeavors) and losing access to that waste if we figure out a means of making use of waste in the future.
[+] [-] Houshalter|11 years ago|reply
[+] [-] kenj0418|11 years ago|reply
[+] [-] CHY872|11 years ago|reply
[+] [-] fleitz|11 years ago|reply
[+] [-] WayneS|11 years ago|reply
Instead of using chemical rockets for the entire dV how about using a rocket to get into orbit and then using an ion engine driven by solar energy to lose the additional 20km/s? It seems the "fuel" weight required would be significantly less.
[+] [-] tim333|11 years ago|reply
http://en.wikipedia.org/wiki/Ulysses_(spacecraft)#Jupiter_sw...
[+] [-] mrfusion|11 years ago|reply