I think I must be suffering from a little too much cheap science-fiction. I’ve seen/read too many stories about the earth’s orbit being altered, one way or another, so that it gets progressively closer to the
sun. I don’t think I’ve ever heard anyone point out that it would simply (perhaps simply is the wrong word) adopt a new orbit.
BTW, thanks to all who point out that this is a prohibitively expensive way to dispose of nuclear waste. I knew that. I was simply wondering about the astrophysics.
I understand the “new” orbit I mentioned in the previous post could be eliptical, and that the Earth could, in fact get closer to the sun (for awhile anyway).
Back to the original question.
It’s not. You may have missed the author’s point. It’s not more difficult to send a rocket toward the sun than into deep space, but is more difficult to send a rocket to the sun. By this, he means INTO the sun. As Jdv’s jokesters realized, the structure encasing a nuclear payload would disintegrate from the heat, spewing fallout into space where the earth could possibly encounter it later.
If NASA can slingshot all manner of vehicles into close encounters with relatively puny bodies such as Callisto or Io, calculating a trajectory for a collision course with the sun would be a child’s play. I guess the question should be: could we get a rocket close enough before it disintegrates to be sure the payload would be consumed as well?
Did we not send a craft on a Mercury drive-by?
Dammit, Nickrz. Just when I thought I had this figured out, you had to go and throw the Mercury flyby into it.
As far as the rest of your post, the article I read didn’t even mention anything about the disintegration of the vessel. So, the basis of my original question remains, though it is an excellent point.
Nickrz sez: It’s not more difficult to send a rocket toward the sun than into deep space, but is more difficult to send a rocket to the sun. By this, he means INTO the sun. As Jdv’s jokesters realized, the structure encasing a nuclear payload would disintegrate from the heat, spewing fallout into space where the earth could possibly encounter it later.
Umm, no. Firstly, it is more difficult to send a rocket to the sun than to deep space, as we’ve exhaustively deomnstrated. Secondly, it doesn’t matter if the rocket melts when it’s close to the sun. It still has mass & will still keep moving on its original trajectory until an outside force acts upon it. Even if it explodes violently, it will be going so fast when it nears the sun that the explosion-induced accelerations won’t be enough to allow the nuke waste to escape.
***Did we not send a craft on a Mercury drive-by? ***
Mariner 10, in 1974-75.
They say I got the power, because I got the monkeys.
They are WRONG! I got the power because I am not afraid to let the monkeys loose.
“Exhaustively demonstrated”? You’ve demonstrated nothing but a bunch of mumbo-jumbo about orbits. Nobody was talking about putting anything into orbit around anything. (I might add, facetiously, that if NASA wanted to put a craft into orbit around the sun, all they would have to do is not launch the damned thing). It’s a simple matter to plot a trajectory which will allow the sun’s gravitational field to capture a spacecraft, and not in any kind of orbit, but a balls-to-the-wall freefall into oblivion. You can’t tell me it’s less difficult to use a smaller gravity source to slingshot a craft into outer space. Someone’s been studying too much rocket science.
And that is the crux of the issue. We’re already going around the sun pretty fast. If we go a little faster, we can escape it. If we go a lot slower, we’ll hit it.
Terminology may be a problem here. Anytime the gravity of one body acts on another, it’s an orbit. Even if you just shoot something in a straight line toward the sun, it’s an orbit, called a “degenerate conic”. And, in order to get that “freefall into oblivion”, you have to overcome almost all of Earth’s orbital velocity, which takes a lot more energy than just boosting the waste into a parabolic escape orbit.
I’m beginning to see that…
And someone should study a bit more. I think I’ve gone into pretty good detail about why I believe my answer to be correct. It may not be intuitive, but it’s true: because of the Earth’s orbital velocity around the sun, it takes less energy to put a craft into an escape orbit than it does to put it in any orbit that intersects the sun.
They say I got the power, because I got the monkeys.
They are WRONG! I got the power because I am not afraid to let the monkeys loose.
Darkfox: “And that is the crux of the issue. We’re already going around the sun pretty fast. If we go a little faster, we can escape it. If we go a lot slower, we’ll hit it.”
Why a “little faster” and “a lot slower”? If that’s true, the Earth is about to go flying off into space. In fact, the opposite is true: the Earth is slowly getting closer.
Furthermore, I’ve thought about the whole thing of using the Earth’s rotation to boost velocity and I still don’t get that either. Maybe I’m just thick. (Skulled, silly.) Couldn’t the Earth’s rotation be used equally as well to slow velocity in relation to the speed around the sun?
The terms “a little faster” and “a lot slower” are relative. You still have to get up quite a bit of speed to hit that parabolic escape velocity (42000 miles per hour!). It’s just a lower amount than the 53000 mph you need to drop down. So therefore, the scientific distinction between a “lot” and a “little” is 11000 mph.
Yep. Also, it’s not the Earth’s rotation that we’re talking about. We’re talking about using a first stage to get to a low-earth parking orbit, and then firing our upper stage at the optimal time. Simply put, you fire your upper stage when you’re headed the direction you want to go. If you want to go faster, you do it when your parking-orbital velocity is in the same direction as the earth’s motion around the sun. To slow down, you do it when the two velocities are opposite each other.
I dunno about your terminology - but when a skydiver’s chute fails to open, I wouldn’t use the term “orbital decay” to describe the cause of death. If and when a big asteroid comes along and obliterates us, will we say “Hey! That great big chunk of rock is in orbit around the earth! Uh… wait a minute, that’s a degenerative conic…”? What you are telling us is, “the escape velocity for the planet earth is greater if you shoot an object toward the sun than if you shoot it away from the sun?”
Where you get the idea we have to reduce the speed of an object (relative to the earth’s’ orbital speed) to send it into the sun I cannot fathom, unless you don’t think we can calculate a trajectory which will result in a collision rather than an orbit. I’ll say that again: COLLISION, not orbit. Maybe the concept of firing a bullet from a gun might help you. Fire a bullet fast enough to escape the earth. Now point the gun (very accurately) alternately at the sun’s disc and at deep space; being the good shot that you are, you’ll hit both the small(er) target and the large one - and don’t forget you’re firing at a very large gravity well in the first instance. I dunno what else to say.
Why is it difficult to send things into the sun? The above discussion made my little head hurt. It’s not like they want it to orbit Venus, just simply put it in a trajectory where it intersects the suns surface.
Why do you need to send it to Sol anyway, just get it out of the Earth-Moon system. Might as well have fallen into the sun then.
Think of it this way: you’re riding on the back of a pick-up truck on the highway and decide you want to get off. The truck bed is not that high off the ground, so jumping off should be no problem, right? While the height won’t be a problem, you’re going to end up skidding along the road at 60 mph because that’s how fast you were going relative to the ground. If you want to land on the ground straight down, you’d have to jump horizontally off the truck backwards at 60 mph, so you’d cancel out the horizontal component of your velocity (to visualize this you have to look at it from the point of view of someone on the side of the road, not a point of view moving with the truck).
That’s basically what we’d have to do to launch something into the Sun. The Earth is moving horizontally over the Sun at 67,000 mph. If we want to drop something from Earth straight down onto the Sun, we’d basically have to launch it backwards off the Earth at 67,000 mph, which would take a lot of fuel and energy.
Heh, has anyone tried to launch things into the sun in Kerbal Space Program? Unlike in 1999, we now have a waste to test these concepts in a way that anyone can visualize.
Yep, I even managed to do it without turning infinite fuel on once. This is counterintuitive, but you should actually start by accelerating so that your orbit is incredibly elongated, one end of the orbit being VERY far from the sun. I think mine went out at least 150 gigameters, which was probably overdoing it.
The reason to do that is that when you get to the point that’s farthest from the sun, you’ll be travelling really slowly. It won’t take much to kill off nearly all your velocity and end up in a path that intersects the sun. I think it took me about 100 years of game time to hit the sun.
You know what’s annoying about this thread? I’m not even sure if I’ve posted in it already. I was reading it through, and a few of those posts sounded like they might have been mine, except then they had a different signature or something.
The “number of rockets” isn’t strictly germane to the question; if there were more demand and a worthwhile reason to launch waste material into space building and operating more launch vehicles would be plausible (and would probably drive toward a launch and range safety infrastructure which would automate many of the labor-intensive operations that contribute to the high launch costs we experience currently). The real showstopper would be the potential for hazard of dispersing radioactive materials in a launch failure; even the most reliable of current launch vehicles have a predicted reliability of 97% to 98%, which means you can expect roughly 2 or 3 failures in any 100 launch attempts. It als bears noting that the “waste” of expended fuel elements in today’s “once through” nuclear fuel cycle may be the wealth of energy for future element recovery and full burnup fuel cycles.
As for the reason it is so difficult to fly a payload to the Sun, the explanation provided by Yumblie is essentially correct, but it may be intuitively easier to understand that an object in orbit is going forward at such speed that it is literally falling above the horizon. In order to hit the ground (fall below the horizon) it has to slow down to almost zero velocity. The Earth is falling around the Sun at over four hundred thousand miles an hour, which is a ridiculous speed. It would actually be easier to fly material out of the solar system than into the Sun, and the lowest energy trajectory to the Sun is to fly a planetary swing-by around Jupiter or Saturn to cancel out most of the orbital speed and let the payload fall into the Sun. Even this is challenging with existing launch systems, often requiring swing-by of Venus to get enough radial velocity in the desired conjunction.
I think it’s also worth noting that there’s a lot more waste than people realize, and most of it isn’t spent fuel.
Perform maintenance work on something, and you’ve (maybe) just created some gloves and wrenches that are now waste. Run a cyclotron for a while, and the concrete walls of the room become waste (activation).
I shut down a facility once and found a large storage closet off of a lab full of various HPLC parts, all radioactive. Over 20 years of running tests on radioactive materials meant all these valves, tubing, etc. used in the HPLCs had accumulated, and the fellow who ran the lab hated dealing with with the paperwork, so he just stockpiled them. Sort of an Alice’s Restaurant situation. And yes, that was not considered an acceptable waste management practice.
My point is that (in addition to what Stranger said) it really would be incredibly impractical. We’d really be much better off with some sort of Yucca Mountain type facility.