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Kebsis
2007-Feb-17, 03:40 AM
I vaguely remember reading a thread here where it was stated that it is extremely difficult to get something from here to the sun; something to do with having to cancel out the centrifical force of the Earth along with the terminal velocity of the earth. Is this true? If it is, how did we get probes to inner planets like Venus and Mercury? And if it is possible to get something to the sun, how would it be done?

Thanks.

Romanus
2007-Feb-17, 04:14 AM
The difficulty of launching something into the Sun is twofold:

1.) Escape from Earth's gravity.
2.) Cancelling the Earth's angular momentum, such that a direct "dive" into the Sun is possible.

IIRC, there is no booster in existence that could do this for even a "regular-sized" space probe. Getting to Venus though, is much easier; as for Mercury, we use gravity assists to slow probes down without using precious fuel (and hence, without adding launch mass).

I think the easiest way to get a significant payload into the Sun was discussed some time ago with a proposed Solar Probe; launch the payload *outward* to Jupiter, and then use its massive gravity to slingshot it back into a collision course with the Sun.

01101001
2007-Feb-17, 04:36 AM
If it is, how did we get probes to inner planets like Venus and Mercury?

To Mercury, with great effort.

Look at the Messenger mission flight plan (http://messenger.jhuapl.edu/the_mission/trajectory.html), for instance. On its way to Mercury orbit, it performs one Earth flyby, two Venus flybys, and 3 Mercury flybys, over 6-1/2 years, before approaching Mercury for an orbit insertion.

Nowhere Man
2007-Feb-17, 04:37 AM
Romanus is correct. The Messenger probe to Mercury (http://en.wikipedia.org/wiki/MESSENGER) is making several fly-bys: Earth, Venus twice, and Mercury thrice in order to slow down enough for its engines to put it into Mercury orbit.

As for the Jupiter fly-by to send stuff to the sun, this is exactly what Ulysses (http://en.wikipedia.org/wiki/Ulysses_probe) did to change its orbit so as to observe the north and south poles of the sun. I don't know if the technique could be used to make the orbit intersect the sun, but I bet it could be done.

Fred

Ronald Brak
2007-Feb-17, 05:31 AM
I thought I should be able to work out the delta V to launch something into the sun with a little effort. Unfortunately a little effort was too much for me.

cjl
2007-Feb-17, 06:33 AM
It's actually quite simple, for a straight in trajectory. You simply cancel all of the earth's orbital velocity, 29.8 km/s, and it will fall right in. That's quite a bit of velocity to cancel though. IIRC, it takes less delta v to eject it completely from the system.

Ronald Brak
2007-Feb-17, 06:50 AM
It's actually quite simple, for a straight in trajectory. You simply cancel all of the earth's orbital velocity, 29.8 km/s, and it will fall right in. That's quite a bit of velocity to cancel though. IIRC, it takes less delta v to eject it completely from the system.

I thought it might be that simple, but I didn't want to say because people think someone who says nothing is smarter than someone who says something and gets it wrong, despite the fact that a person who often makes mistakes is a person who often has opportunities to learn. (Or perhaps just an idiot.)

cjl
2007-Feb-17, 06:58 AM
You could definitely do it with less delta v through various trajectories, but that is the most direct way. Now, calculating the minimum delta v path is more complicated...

JohnD
2007-Feb-17, 11:24 PM
If you cancel ANY of the Earth's orbital velocity, why won't the probe spiral in, eventually?
John

StupendousMan
2007-Feb-18, 12:26 AM
If you cancel ANY of the Earth's orbital velocity, why won't the probe spiral in, eventually?
John

Conservation of angular momentum. You could look it up.

grant hutchison
2007-Feb-18, 12:27 AM
If you cancel ANY of the Earth's orbital velocity, why won't the probe spiral in, eventually?Cancel a small amount of orbital velocity, and the spacecraft will fall towards the sun, pick up speed, and come back out to the original distance. Then the cycle repeats: it just enters an elliptical orbit.

Grant Hutchison

Delvo
2007-Feb-18, 03:16 AM
If cancelling a fraction of the speed causes a more-elliptical orbit that still extends at least as far out as the original less-elliptical one did, then how would you create an equally, or less, elliptical orbit at a shorter distance from the sun, one that does not extend out to the original orbit's distance? (This is what I would have expected to happen, but now it sounds like you're saying this would require a second "burn" after the initial decrease in distance, or perhaps a long continuation of the first "burn" to counter the slingshot acceleration you mentioned.)

cjl
2007-Feb-18, 04:57 AM
You would do a short burn to get it into the elliptical orbit. Then, when it was at the perigee (closest point to the sun), you would do another burn to slow it down again. This would circularize the orbit closer to the sun than it started.

satori
2007-Feb-18, 07:55 PM
it must be an easy task, as the atomic industry has ( I remember well ) promised to dump all their mess in the sun one day

StupendousMan
2007-Feb-18, 11:00 PM
it must be an easy task, as the atomic industry has ( I remember well ) promised to dump all their mess in the sun one day

I disbelieve you. Could you please provide a reference for this claim?

It is _not_ an easy task. I just gave my physics students a homework question which involves the amount of fuel required to launch 1 kg of material into the Sun ... and it's not a small number.

cjl
2007-Feb-18, 11:47 PM
it must be an easy task, as the atomic industry has ( I remember well ) promised to dump all their mess in the sun one day


1) It is absolutely not an easy task
2) References? There are about a million easier ways to dispose of nuclear waste.

satori
2007-Feb-19, 10:44 AM
I just wanted to discredit the atomic industry !

You are of course perfectly right cjl with your pointing to our orbital velocity of 30km/sec. Add another 10km/sec (?) or so to get rid of Earth's gravitational embrace and you schould have quite a good estimation of the amount of energy you would need to reach Sun.

( yes i begin to realize, in this artifical posting world you must use explicite means to mark irony as what it was meant for. sorry my fault ! )
-------------------------------------------
all will end in tears....I just know it

satori
2007-Feb-19, 10:53 AM
cjl,
"There are about a million easier ways to dispose of nuclear waste.".....But is there one Good one ?!

We will live to see the day, when the enemy will dispose of atomic waste in a dirty bomb kind of fashion. That will be the day, when those stupid Sun-disposal-plans will finaly have their day after all and they will set up Huge rocket factories all over...

crosscountry
2007-Feb-19, 12:17 PM
It's actually quite simple, for a straight in trajectory. You simply cancel all of the earth's orbital velocity, 29.8 km/s, and it will fall right in. That's quite a bit of velocity to cancel though. IIRC, it takes less delta v to eject it completely from the system.


that is fast, only 2.5x faster that we can go now. but we could manage it maybe if we weren't trying to have it drop straight down onto the sun. Have it do a flyby of venus during a time of good alignment, and with good calculations it will go directly into the sun.

WaxRubiks
2007-Feb-19, 12:42 PM
cjl,
"There are about a million easier ways to dispose of nuclear waste.".....But is there one Good one ?!


well, you can put it on the bus Gus,
Put it on the plane Elaine...............
.................

BigDon
2007-Feb-19, 02:08 PM
*WARNING LAYMAN ABOUT TO ASK QUESTION*

So all of you are saying that taking something like a Saturn V set up, leading the Sun a little bit, and firing at the right time won't send a payload the wieght of an Apollo mission to a fiery doom? I thought it was downhill from here to the Sun. Especially if you are just trying to hit it and not orbit it.

satori
2007-Feb-19, 02:30 PM
i once climed at night on a balustrade and looked up.... after a while i got the strange feeling, that when i jumped now, i would fall among all those stars....that's about as wrong an impression of course as the one you harbour about us and the sun...

cjl will certainly straight it out for you better than i could

grant hutchison
2007-Feb-19, 02:52 PM
So all of you are saying that taking something like a Saturn V set up, leading the Sun a little bit, and firing at the right time won't send a payload the wieght of an Apollo mission to a fiery doom?That's right.
If you do that, you'll send your payload into an elliptical orbit. You essentially need to remove all of the Earth's speed around the sun to make your elliptical orbit fall far enough in to even graze the sun. And if it doesn't graze the sun, it'll just loop back up out of the sun's gravity-well under its own momentum.

Think of sitting on a train, and trying to lob a tennis ball at a fencepost, as it whips past at 100mph. You just can't do it when you're level with the post, because the speed of the train carries your lob past the post.
Ah-ha, you say, I just need to throw the ball before I'm level with the post, and let the speed of the train slam my ball into it sideways. Trouble is, when you're in a circular orbit, you're always level with the post. :)

Grant Hutchison

crosscountry
2007-Feb-19, 03:07 PM
That's right.
If you do that, you'll send your payload into an elliptical orbit. You essentially need to remove all of the Earth's speed around the sun to make your elliptical orbit fall far enough in to even graze the sun. And if it doesn't graze the sun, it'll just loop back up out of the sun's gravity-well under its own momentum.

Think of sitting on a train, and trying to lob a tennis ball at a fencepost, as it whips past at 100mph. You just can't do it when you're level with the post, because the speed of the train carries your lob past the post.
Ah-ha, you say, I just need to throw the ball before I'm level with the post, and let the speed of the train slam my ball into it sideways. Trouble is, when you're in a circular orbit, you're always level with the post. :)

Grant Hutchison


:clap: couldn't have said it better

BigDon
2007-Feb-19, 03:30 PM
But...but..but.. I saw on TV where....




Thanks guys, seems there's an education in every bowl of BAUT flakes.

Delvo
2007-Feb-19, 04:05 PM
I thought it was downhill from here to the Sun. Especially if you are just trying to hit it and not orbit it.It's downhill on a slope that's shaped like the inside of a bowl, where you're always moving so fast that your momentum tends to cause you to drift outward, which is uphill.

Argos
2007-Feb-19, 04:11 PM
We discussed this issue a while back (http://www.bautforum.com/showthread.php?t=51224&highlight=space+elevator+nuclear+dump+sun). The idea was to use a space elevator to dump nuclear waste into the Sun.

hhEb09'1
2007-Feb-19, 04:15 PM
Think of sitting on a train, and trying to lob a tennis ball at a fencepost, as it whips past at 100mph. You just can't do it when you're level with the post, because the speed of the train carries your lob past the post.You could do it if you could throw it faster than 100mph. But that's your point, I know, not many people would be capable of doing that. :)

It takes a lot of effort.

George
2007-Feb-19, 04:31 PM
Trouble is, when you're in a circular orbit, you're always level with the post. :)
For those on this side of the Atlantic, his "level" refers to being "even" with the post, or along side of it. Over here, "level" is associated with a horizontal grade normally, unless we stipulate otherwise.

[Added: I assume the 100mph is not of a narrow-gage train. :)]

grant hutchison
2007-Feb-19, 04:32 PM
You could do it if you could throw it faster than 100mph. But that's your point, I know ...Exactly. The only way to do it is to stand a baseball pitcher on the caboose, and have him pitch almost straight backwards to effectively cancel the train's speed. Which is analogous to the fact that you have to largely cancel the Earth's orbital speed to drop something into the sun.

Grant Hutchison

grant hutchison
2007-Feb-19, 04:35 PM
For those on this side of the Atlantic, his "level" refers to being "even" with the post, or along side of it. Over here, "level" is associated with a horizontal grade normally unless we stipulate otherwise.Thanks for the translation, George. :)
(If someone had written "even with the post" I'd have had no idea what was meant.)

Grant Hutchison

satori
2007-Feb-19, 04:57 PM
if you have got time, you could wait for the sun to come to you

crosscountry
2007-Feb-19, 05:04 PM
if you have got time, you could wait for the sun to come to you


think in terms of half life.

Fazor
2007-Feb-19, 08:13 PM
But...but..but.. I saw on TV where....

Thanks guys, seems there's an education in every bowl of BAUT flakes.

Yeah! On the simpsons the rocket launched and they all rode leisurely into the sun. No problems. :)

Yes, Lots of education on BAUT. Perhaps too much. Ignorance is bliss! Stop filling my head with these "facts!" *freaks out!* :)

And thanks for the Train/fencepost analogy Grant. I couldn't figure out what you guys were talking about, but I guess it makes sense.

George
2007-Feb-19, 08:45 PM
And thanks for the Train/fencepost analogy Grant. I couldn't figure out what you guys were talking about, but I guess it makes sense.
He is saying that if you are traveling very fast, such as being aboard a 100mph train, you can not ever throw something out the window and hit a fence post once you are already along side of it. Your rock, or whatever, will always go behind it. That is what Grant meant by being "level" with the post. The Earth is traveling very fast relative to the Sun and you can't "throw" anything at it and hit it as you will always miss it, though the Sun will pull it back into an elliptical orbit.

George
2007-Feb-19, 08:52 PM
I am curious how the new Sunshine movie will handle this. [I sent a heliochromological statement to their science advisor (actually complimenting them for the white sun in their trailer). Any response will come as surprise, however. :)]

Fazor
2007-Feb-19, 09:02 PM
He is saying that if you are traveling very fast, such as being aboard a 100mph train, you can not ever throw something out the window and hit a fence post once you are already along side of it. Your rock, or whatever, will always go behind it. That is what Grant meant by being "level" with the post. The Earth is traveling very fast relative to the Sun and you can't "throw" anything at it and hit it as you will always miss it, though the Sun will pull it back into an elliptical orbit.

Sorry, mistype, i meant "I didn't know what you guys were talking about until he gave that analogy." So in order to hit the sun, you'd have to aim "behind" it, which I'm assuming is what you mean when saying enough force to overcome angular momentum. I never thought shooting a rocket into the sun would be so complicated, but I guess that's why I don't work for NASA plotting flight trajectories ;)

grant hutchison
2007-Feb-19, 09:02 PM
He is saying that if you are traveling very fast, such as being aboard a 100mph train, you can not ever throw something out the window and hit a fence post once you are already along side of it. Your rock, or whatever, will always go behind it.Given the natural limit to the velocity that can be imparted by an unaided human arm, as hhEb09'1 clarified; that limit was intended to be analogous to our own current (rather limited) ability to impart velocity to objects launched from the surface of the Earth.
Of course you could hit the fencepost with a rifle bullet, if you laid off a little. Which would be analogous to some potential future launch capability in which we could command velocity-changes of the order of a hundred kilometres per second.

Grant Hutchison

grant hutchison
2007-Feb-19, 09:08 PM
So in order to hit the sun, you'd have to aim "behind" it ...And because we can't currently launch payloads at anything approaching Earth's speed around the sun, it doesn't matter how far we lay off with our aim, our payload will still end up travelling around the sun; just as a lobbed tennis ball will end up moving in more or less the same direction as the train, no matter which way we aim it.

Grant Hutchison

George
2007-Feb-19, 10:19 PM
Given the natural limit to the velocity that can be imparted by an unaided human arm, as hhEb09'1 clarified; that limit was intended to be analogous to our own current (rather limited) ability to impart velocity to objects launched from the surface of the Earth. Yes, I like your analogy, though if it were the train I took from Plymouth, I would have jumped off before the 100mph (or is it meters/hour ;)). At normal speed, it was an enjoyable ride. :)

Using the simple 2 pi r equation for circumference (circular orbit), I obtain an orbital velocity for the Earth of about 107,700 km/hr. Extending your analogy, it would be far easier to ride a motorcycle in reverse at 100 mph on top of the train and try and hit the fence post than to try and hit the sun.

crosscountry
2007-Feb-19, 11:52 PM
29.8 km/sec is the accepted value. it's fast, over 2x our fastest on record.

cjl
2007-Feb-20, 05:18 AM
Yes. Not only that, but the solar escape velocity here is around 42.1km/s. So, if you give something 12.3 km/s, you can eject it from the system entirely, making it an incredible waste of energy to lob stuff into the sun.

hhEb09'1
2007-Feb-20, 05:39 AM
Yes. Not only that, but the solar escape velocity here is around 42.1km/s. So, if you give something 12.3 km/s, you can eject it from the system entirely, making it an incredible waste of energy to lob stuff into the sun.The escape velocity is, rule of thumb, 40% greater than the orbital velocity (square root of 2, minus 1). However, with a little ingenuity, we can get things to impact the sun with less than that investment of 40%.

cjl
2007-Feb-20, 05:57 AM
You can also get stuff out of the solar system with less energy than that, with a bit of ingenuity. I believe that the minimum energy to eject something from the solar system is less than the minimum to drop something into the sun, but I may be wrong...

A gravity assist from Jupiter can significantly boost the velocity.

crosscountry
2007-Feb-20, 08:16 AM
I know mathematically how all that works - I've solved the equations before, but it's still hard in my head to imagine that it would take less energy to send something all the way out of the solar system than down to the sun.


Maybe there's a child stuck in my brain somewhere.

BigDon
2007-Feb-20, 09:50 AM
For God's sake give me a hand over here! This man has a child stuck in his brain!

Kebsis
2007-Feb-20, 10:46 AM
Well, let me see if I've got this straight, correct me if I'm wrong:

The Earth going around the sun is kinda like a bucket being swung around on a tether. If an object is attached to the bucket, it can be ejected from the orbit of the bucket easily by cutting whatever is holding it to the bucket (in Earth's case, gravity would be holding the rocket), and it will fly off easily.

However, to get the same object from the bucket to the center of its orbit would require a much greater application of energy, to cancel out the outward force that it had acquired.

Is that an accurate analogy?

crosscountry
2007-Feb-20, 11:21 AM
there is no outward force. only angular momentum is the problem. You basically need zero angular momentum to make it to the sun. We're moving over 100,000 km/hr so even a very small object has lots of it.


The trick it to stop that bucket in mid air. Then the object will fall into the sn. The energy required to do that is greater than man can currently produce (without tricks of gravity assist)

Even if we shoot a bullet directly backwards in orbit it will still have too much angular momentum to be stopped relatively to the sun and will continue in some new orbit closer to the sun than the earth, but not much.

crosscountry
2007-Feb-20, 11:21 AM
there is no outward force. only angular momentum is the problem. You basically need zero angular momentum to make it to the sun. We're moving over 100,000 km/hr so even a very small object has lots of it.


The trick it to stop that bucket in mid air. Then the object will fall into the sn. The energy required to do that is greater than man can currently produce (without tricks of gravity assist)

Even if we shoot a bullet directly backwards in orbit it will still have too much angular momentum to be stopped relatively to the sun and will continue in some new orbit closer to the sun than the earth, but not much.

Michael Noonan
2007-Feb-20, 12:24 PM
I know this will sound silly but what if you turned outwards some time before you reached apogee ( the point furthest away I think ) and let the ever growing elipse reduce the rotation effect?

Is this any more fuel efficient although it requires a raft of minor course corrections.
Cheers

George
2007-Feb-20, 01:51 PM
I wonder just how tough it really would be? New Horizons headed-out at 57,600 km/h and is now, with the Jupiter boost, at >70,000 km/h. It is a lightweight craft. Could a couple of booster rockets be taken up into orbit and assembled on a solar probe to achieve the necessary speed?

How much less rocket power would be required using Venus and Mercury as gravity brakes?

Am I right that Jupiter could not help us in any way?

satori
2007-Feb-20, 02:18 PM
you could maneuver your space ship into a very excentric ellipse (somehow) with your original angular momentum conserved....if you would further change to very, very excentric, you would finaly touch the sun...and bingo

SolusLupus
2007-Feb-20, 02:25 PM
Here's a question:

Why does it matter if you can't send the trash INTO the sun? Can't you just send it "as close as we can get cheaply"? Even if it won't eventually go into the sun, I somehow don't see it as being all that polluting. Space is big.

hhEb09'1
2007-Feb-20, 02:27 PM
Here's a question:

Why does it matter if you can't send the trash INTO the sun? Can't you just send it "as close as we can get cheaply"? Even if it won't eventually go into the sun, I somehow don't see it as being all that polluting. Space is big.It's kinda like a ball that you fhrow at a hole in the floor--if you don't hit the hole, it bounces back to your hand. :)

SolusLupus
2007-Feb-20, 02:31 PM
It's kinda like a ball that you fhrow at a hole in the floor--if you don't hit the hole, it bounces back to your hand. :)

No it doesn't. Maybe if I threw it at the wall, but not the floor. If I threw it at the floor and missed, it would bounce in the opposite direction, more than likely. There needs to be an angle or a wall facing me to bounce off towards me.

But I don't think that it would be *that* easy to ram right back into Earth. We're a pretty hard target.

hhEb09'1
2007-Feb-20, 02:38 PM
No it doesn't.Just watched someone perform this "experiment" and their ball returned to the hand 98.7% of the time. They also had a double double, and three steals. :)

SolusLupus
2007-Feb-20, 02:39 PM
Just watched someone perform this "experiment" It did, 98.7% of the time. They also had a double double, and three steals. :)

But then you're throwing it straight down.

I was thinking more of an angle.

hhEb09'1
2007-Feb-20, 02:43 PM
But then you're throwing it straight down.

I was thinking more of an angle.The point is, it'll return to about the same height. In the case of the earth/sun, it would return to near earth's orbit.

crosscountry
2007-Feb-20, 02:57 PM
and eventually coincide with our own path.


But it would be much easier to dump it on Mars. Isn't that the American way anyway, give someone else our problems?

We've got craters on the moon big enough to hold a lot of waste, and they're on the backside where we can't see them anyway.

grant hutchison
2007-Feb-20, 03:02 PM
Am I right that Jupiter could not help us in any way?Jupiter can, because we can use the slingshot to reduce our payload's kinetic energy, if we shoot it ahead of Jupiter rather than behind.

In fact, going outwards before you come in is the way to go with this, providing you have a rocket motor aboard your payload.
It takes less delta-v to hit the sun if you first push yourself into an ellipse with a very high aphelion, and then decelerate to a near-standstill at aphelion. At the limit, you accelerate to solar escape velocity (1.414 times Earth's orbital velocity), and then an infinite time later apply an infinitesimal deceleration, which drops the payload into the sun a further infinite time later.
So you achieve the effect with a delta-v of only 0.4 times Earth's orbital velocity, rather than reversing the whole amount.
In practice, you find a family of smaller ellipses that will still give you the final effect with a lower delta-v than removing all the Earth's orbital velocity in a single burn.

Grant Hutchison

eburacum45
2007-Feb-20, 03:10 PM
How about using the Moon for a slingshot manoeuvre? I notice that is rarely used, so presumably it is no advantage.

hhEb09'1
2007-Feb-20, 03:13 PM
So you achieve the effect with a delta-v of only 0.4 times Earth's orbital velocity, rather than reversing the whole amount.And you could get 4% of that by launching at midnight. Sideways. :)

crosscountry
2007-Feb-20, 03:14 PM
the moon is moving the same speed as us so there is very little advantage



we could however do repeated passes past the earth and moon each time giving the payload more energy (or less depending on how you look at it) and finally when there is enough give it a little boost to set it backwards at the right speed.

of course then we have nuclear waste floating above our heads for months.

crosscountry
2007-Feb-20, 03:15 PM
And you could get 4% of that by launching at midnight. Sideways. :)


cool idea, we could also use that to lose energy at noon.

Argos
2007-Feb-20, 03:50 PM
An ion engine approach like this one (http://space.newscientist.com/article.ns?id=dn8599) could do the trick, methinks.

satori
2007-Feb-20, 05:27 PM
Here's a question:

Why does it matter if you can't send the trash INTO the sun? Can't you just send it "as close as we can get cheaply"? Even if it won't eventually go into the sun, I somehow don't see it as being all that polluting. Space is big. (Lone Wolfe)

I find that a perfectly reasonable argument and the answers given so far less than satisfying
In the same spirit of the arguments brought against the possibility to reach the sun for cheap one had to argue consequently also in the situation given here that an arbitrary impuls of say 10km/sec(*massX) must suffice to distance us from this object effectifly (just by the same angular momentum and orbit energy argument given so far)
could one even use some canon to provide this impuls ?
radioactive waste is just dump matter, easily withstanding any accelaration factor imaginable

NEOWatcher
2007-Feb-20, 05:33 PM
...I find that a perfectly reasonable argument and the answers given so far less than satisfying...
Launching to any orbit that is slower than the earth will do (within reason). The issue is that you will still need to impart the same impulse at the other end of orbit to keep it at that orbit, or the "stuff" will come right back into Earths orbit.

crosscountry
2007-Feb-20, 06:10 PM
what if we leave it up there in some safe orbit? instead of burning it all up in the sun maybe one day we can use it as a refuelling station on longer space missions when the technology is far enough advanced to handle the waste more appropriately. It's not useless just needs more refining.

George
2007-Feb-20, 06:38 PM
Jupiter can, because we can use the slingshot to reduce our payload's kinetic energy, if we shoot it ahead of Jupiter rather than behind.
Ah, I see, if the trajectory is into Jupiter's orbital path, then the delta V would be a deduct. Of course.

I would think there is a trajectory that would allow Venus to sling-shot a probe directly into the Sun. Even if it were a small window, is it not possible?

hhEb09'1
2007-Feb-20, 07:11 PM
I would think there is a trajectory that would allow Venus to sling-shot a probe directly into the Sun. Even if it were a small window, is it not possible?The "window" might be inside Venus :)

satori
2007-Feb-20, 07:36 PM
Venus is hell anyway..... could anyone call the dumping of waste there environmentaly irresponsable

crosscountry
2007-Feb-20, 07:46 PM
Ah, I see, if the trajectory is into Jupiter's orbital path, then the delta V would be a deduct. Of course.

I would think there is a trajectory that would allow Venus to sling-shot a probe directly into the Sun. Even if it were a small window, is it not possible?

yes, but it still requires a lot of energy, not quite as much as the sun, but a lot.

Delvo
2007-Feb-20, 08:10 PM
If we were to use Venus or Jupiter for slingshot maneuvers, we might just as well drop it into Venus's or Jupiter's atmosphere instead of the sun.

George
2007-Feb-20, 08:33 PM
The "window" might be inside Venus :) That would slow down. :D

But, you are bound to be right (in the rhetorical sense). In that case, wouldn't several passes, along with a trip or two at Mercury perhaps, do the trick? Is there a video game about this? :)

neilzero
2007-Feb-20, 09:03 PM
We likely do not want high level nuclear waste in the atmosphere of Venus, as we may have balloon supported stations or colonies in the upper atmosphere of Venus. At the optimum altitude, the temperature is about 55 degrees f.
Colonies are less likely for Jupiter as the gravity is about 2.75g.
Saturn and Venus have about one g gravity in the cloud tops. Neil

01101001
2007-Feb-20, 10:30 PM
Is there a video game about this? :)

NASA JPL: The Gravity Assist Mechanical Simulator (http://www2.jpl.nasa.gov/basics/grav/)

http://www2.jpl.nasa.gov/basics/grav/thumbnail.gif (http://www2.jpl.nasa.gov/basics/grav/)

George
2007-Feb-21, 03:43 AM
NASA JPL: The Gravity Assist Mechanical Simulator (http://www2.jpl.nasa.gov/basics/grav/)
Perfect. :clap:

DaveC426913
2007-Feb-21, 04:40 AM
The escape velocity is, rule of thumb, 40% greater than the orbital velocity (square root of 2, minus 1). However, with a little ingenuity, we can get things to impact the sun with less than that investment of 40%.
I had not thought of solar system escape v in terms of orbital v.

So, Earth is orbiting at ~29km/s, and escape v from our ss at this point is ~41km/s, right?

How does that compare to other places in the SS? Mercury is deep in the Sun's g-well, but it also has a lot more orbital v. Pluto OTOH...

I'd be interested in seeing this graphed.

DaveC426913
2007-Feb-21, 05:24 AM
I'd be interested in seeing this graphed.Oh. That wasn't as hard as all that...


So, from Mercury's orbit, you'd need to gain 18km/s to escape the SS, whereas from Neptune's you'd need to gain a mere 2.3km/s. (Alas, I had no orbital v. for Pluto - and so it begins its long slide into obscurity).

crosscountry
2007-Feb-21, 09:49 AM
Oh. That wasn't as hard as all that...


So, from Mercury's orbit, you'd need to gain 18km/s to escape the SS, whereas from Neptune's you'd need to gain a mere 2.3km/s. (Alas, I had no orbital v. for Pluto - and so it begins its long slide into obscurity).

nice work, but your graph has the wrong slope.

hhEb09'1
2007-Feb-21, 02:21 PM
nice work, but your graph has the wrong slope.There are no bad slopes, only misunderstood slopes :)

Pluto is on the left

crosscountry
2007-Feb-21, 03:32 PM
you know what? I was doing run over rise and confusing the two numbers.


DOH, silly me. It wasn't about Pluto but rather drawing line downward from the wrong number.

Kaptain K
2007-Feb-21, 05:14 PM
I had not thought of solar system escape v in terms of orbital v.

So, Earth is orbiting at ~29km/s, and escape v from our ss at this point is ~41km/s, right?

How does that compare to other places in the SS? Mercury is deep in the Sun's g-well, but it also has a lot more orbital v. Pluto OTOH...

I'd be interested in seeing this graphed.
The escape velocity for any object is 1.414 (square root of 2) times orbital velocity.

crosscountry
2007-Feb-21, 06:37 PM
The escape velocity for any object is 1.414 (square root of 2) times orbital velocity.

for circular orbits right? what about elliptical?

grant hutchison
2007-Feb-21, 07:08 PM
for circular orbits right? what about elliptical?Escape velocity is always root two times the circular velocity for a given distance from the centre of mass.

Circular velocity is given by:

vc2 = GM/R

Parabolic (escape) velocity is:

vp2 = 2GM/R

So if you're at apocentre, you'll need a larger proportional change in velocity to get you up to escape velocity than you will if you're at pericentre.

Grant Hutchison

grant hutchison
2007-Feb-21, 09:33 PM
In fact, going outwards before you come in is the way to go with this, providing you have a rocket motor aboard your payload.
It takes less delta-v to hit the sun if you first push yourself into an ellipse with a very high aphelion, and then decelerate to a near-standstill at aphelion. At the limit, you accelerate to solar escape velocity (1.414 times Earth's orbital velocity), and then an infinite time later apply an infinitesimal deceleration, which drops the payload into the sun a further infinite time later.
So you achieve the effect with a delta-v of only 0.4 times Earth's orbital velocity, rather than reversing the whole amount.
In practice, you find a family of smaller ellipses that will still give you the final effect with a lower delta-v than removing all the Earth's orbital velocity in a single burn.Further to this, I ran some numbers out of interest. Here's how it pans out for a range of delta-v's between 1 and 0.42 times the Earth's orbital velocity. A delta-v ratio of 1 corresponds to the straight drop into the sun; lesser delta-v's come in two stages, with one delta-v initially to speed the payload into an elliptical orbit, and then another at aphelion to institute a straight drop sunwards.

Δv/vc Aphelion (AU) Time (yr)
1.0 1.0 0.2
0.9 1.2 0.8
0.8 1.6 1.1
0.7 2.2 1.6
0.6 3.6 2.9
0.5 7.9 8.7
0.45 19.3 31.2
0.42 113.0 426.7
Buying the last little bit of efficiency requires a long wait before the payload reaches the sun.

Grant Hutchison

Van Rijn
2007-Feb-22, 12:31 AM
We likely do not want high level nuclear waste in the atmosphere of Venus, as we may have balloon supported stations or colonies in the upper atmosphere of Venus. At the optimum altitude, the temperature is about 55 degrees f.
Colonies are less likely for Jupiter as the gravity is about 2.75g.
Saturn and Venus have about one g gravity in the cloud tops. Neil

This stuff is heavy, so high level waste sent to Venus would settle on the surface. Not that there would be that much of it anyway, and you would have sealed environments if anyone actually was in habitats floating high in the atmosphere.

But there's no point in doing it. The "shooting stuff into the sun" discussion is technically interesting, but there just isn't any point in sending nuclear waste in space. It would be safer and easier to put high level waste deep underground. The rocket flights would be more dangerous, waste or no waste.

DaveC426913
2007-Feb-22, 02:07 AM
The escape velocity for any object is 1.414 (square root of 2) times orbital velocity.sunuvagun. Can't believe I didn't make that last leap of understanding

satori
2007-Feb-22, 02:13 PM
Van Rijn,

The rocket flights would be more dangerous, waste or no waste.
i remember well the environmentalists protests agaist the use of plutonium batteries in space probes

that was about the only time i could understand those who hate them eco-freaks

SolusLupus
2007-Feb-22, 08:46 PM
that was about the only time i could understand those who hate them eco-freaks

Only time?

I tend to hate eco-freaks a lot of the time. In fact, most of the time.

Don't get me wrong, I understand some of environmentalism. But most of the ones I hear of distort facts and just don't seem to understand modern industry. There's this concept that all of industry has a goal to destroy the Earth, and never adopt new measures. The way business runs now is exactly as it ran, say, 50 years ago, only now it's worse. I mean, they actually think that nuclear power plants are useful! OMG!

satori
2007-Feb-22, 08:59 PM
Lone Wolfe,
( this is of course totaly off course, I mean off topic ,off thread...but)
your (American ) breed of environmentalists thinks nuclear power as something good and friendly .......?!?!
That is a totaly outlandish notion for me !

SolusLupus
2007-Feb-22, 09:07 PM
Lone Wolfe,
( this is of course totaly off course, I mean off topic ,off thread...but)
your (American ) breed of environmentalists thinks nuclear power as something good and friendly .......?!?!

By "they", I meant the businesses. Not the environmentalists. My bad. I was mocking Environment's views about the businesses.


That is a totaly outlandish notion for me !

What, environmentalists think that nuclear power is good and friendly, or the idea of nuclear power being good and friendly? But yeah, this is pretty off topic.

satori
2007-Feb-22, 09:18 PM
sorry, LW, my limited grasp of the english vernacular...
.... for a second i was led to believe that the American devision of the (I know globaly organized !) environmentalists could in fact have come to embrace nuc tech ('cause GlobWarm)....that was what would have struck me as queer...!

Van Rijn
2007-Feb-22, 09:42 PM
sorry, LW, my limited grasp of the english vernacular...
.... for a second i was led to believe that the American devision of the (I know globaly organized !) environmentalists could in fact have come to embrace nuc tech ('cause GlobWarm)....
that was what would have struck me as queer...!

Since you are having language problems, I won't take that comment the wrong way. Take this to another thread if you want to discuss it. Nuclear is an excellent energy option.

satori
2007-Feb-22, 09:56 PM
It is a minor topic, Van Rijn, but you are treating me unfairly!
If you were more familiar with your very own language, you would have easily read thru the few short posts prior to this one and you would have found it totaly unnecessary to remind me of the deviation sin...... repeat :Totaly Unnecessery !!!
if the topic on hand is so touchy for you, you can't resist the urge to respond.... Then please play fair ....and don't take your personal convictions on the subject as a selfunderstood given...

bytheby : i have zero affiliations to any environmental organisation nor to any gun club were i would practice this sort of from the hip shooting routine of your's

crosscountry
2007-Feb-22, 10:31 PM
If I could kill 10,000 SUVs to save one speckled owl I'd do it.

satori
2007-Feb-22, 10:40 PM
hey crosscountry you are biking on dangerous lands here !

SolusLupus
2007-Feb-22, 10:43 PM
If I could kill 10,000 SUVs to save one speckled owl I'd do it.

If I could kill 10,000 speckled owls to keep my SUV, I'd do it. ;)

Unless you're willing to pay for a new vehicle for me? I need something that can hold a lot of space, though, and go long distances. Without it, I pretty much can't do what I need to do.

satori
2007-Feb-22, 10:44 PM
crosscountry,
if it should come to some ugly turf war here (highly likely), you can't count on me to assist you, as i mmuuuust go sleep.....

SolusLupus
2007-Feb-22, 10:45 PM
crosscountry,
if it should come to some ugly turf war here (highly likely), you can't count on me to assist you, as i mmuuuust go sleep.....

Good night, don't let the speckled owls bite.

Van Rijn
2007-Feb-22, 11:05 PM
It is a minor topic, Van Rijn, but you are treating me unfairly!


I am? Perhaps you misunderstood the intent of my comment.



if the topic on hand is so touchy for you, you can't resist the urge to respond.... Then please play fair ....and don't take your personal convictions on the subject as a selfunderstood given...


Let's see, I said I wouldn't take your comment the wrong way, said nuclear was an excellent energy option, and suggested that you take this to another thread if you wanted to discuss it. (And that's because nuclear power, as others have noted, is not the topic of this thread.)

You'll have to explain why that is in any way unfair. I don't get it - and you seem to be far more touchy about my comments than I am of yours.

Kaptain K
2007-Feb-23, 12:14 AM
If I could kill 10,000 speckled owls to keep my SUV, I'd do it. ;)

Unless you're willing to pay for a new vehicle for me? I need something that can hold a lot of space, though, and go long distances. Without it, I pretty much can't do what I need to do.
There is a big difference between people, such as yourself, who buy SUVs because they need them for what only they can do and those buy them as status symbols. Parking a Hummer on the grass at the golf course is not off-roading!

SolusLupus
2007-Feb-23, 03:51 AM
There is a big difference between people, such as yourself, who buy SUVs because they need them for what only they can do and those buy them as status symbols. Parking a Hummer on the grass at the golf course is not off-roading!

I don't think that Crosscountry was being specific as to who's SUV he intended on taking away. ;)

crosscountry
2007-Feb-23, 04:20 AM
nope, not specific. funny the replies though.


It was probably a poor example but I'm just saying your status symbol shouldn't infringe on nature just because you want it to.

cjl
2007-Feb-23, 05:40 AM
SUV's should not be looked at as a status symbol. They should be looked at as a practical transportation device for those who need to carry a lot of stuff through less than optimum travel routes. If you're a soccer mom driving your kid around on public roads, you don't need one. If you're ANYONE who does not need an SUV, you should not have one. I don't have a problem with those who actually need one. It's the vast majority of SUV owners who do NOT need one, but instead have one for the sole purpose of having one that I don't like.

On a side note, one of my favorite cars is the subaru outback. Mine gets 26mpg combined, and has plenty of room to cart stuff around (I carry a lot of junk around). It also is decently capable on dirt roads, snow, in the mountains, etc. It's a great choice for those who need some SUV-like characteristics without having to go all the way (some people really do need a full SUV - again, I have nothing against them).

satori
2007-Feb-23, 09:17 AM
(And that's because nuclear power, as others have noted, is not the topic of this thread.)

You'll have to explain why that is in any way unfair. I don't get it - and you seem to be far more touchy about my comments than I am of yours. (your qoute Van Rijn (with my highlighting))

Let me first observe, Van Rijn, that from your (relatively) mild response to my somewhat hysterical post (I grant that) I gather that you might be a decent character after all....

As much as I would like, I can't spare you the reproach of having treated me unfairly though and even continuing to do so !
If you study the previous posts with due scruteny you will easily find, that it was me, yes me and nobody other, who made the initial attempt to keep this thread "clean", quote (satori) :

Lone Wolfe,
( this is of course totaly off course, I mean off topic ,off thread...but)

upon this statement follow two lines of condensed prose (plus a short threeliner to correct some misunderstanding on the part of my interlocutor) and............................................... ...............nothing more .........period.

now am i realy accusing you unfairly of unfairness.....?



and stop that OT-Babbling on SUV s all of you for the Mods sake

Argos
2007-Feb-23, 02:00 PM
My bad introducing nuke into this thread. I was only talking of the space elevator commments we´ve discussed in another thread, involving sending the stuff to the Sun. A Space Elevator launch at noon could cancel out some 15% of the Earth´s orbital speed, and combined with chemical/ion thrusters could allow for a highly elliptical, sun-intercepting orbit. It was designed as a thought experiment, since space elevators are beyond our tech horizon. This is all it had in common with this thread, and discussing nuclear here is off-topic.

bnesheim
2017-Apr-08, 10:57 AM
Looking at this tread it "hit" me that if you you should try this it would be much like trowing something against the wind. It will move into the sun for some time then it will avaporate, and the solar wind will blow the gas out again.

Nowhere Man
2017-Apr-09, 12:34 PM
Thread necromancy alert, 10 years.

Fred

Jens
2017-Apr-10, 01:43 AM
Looking at this tread it "hit" me that if you you should try this it would be much like trowing something against the wind. It will move into the sun for some time then it will avaporate, and the solar wind will blow the gas out again.

It's an interesting question, albeit a bit unrelated to the original question. I imagine that if you launched a probe directly into the sun, it would gradually evaporate, and I wonder what would happen to the gas particles. It might well be that the lighter atoms will be cast away, but that the heavier ones will may their way into the interior of the sun. I'd be happy to hear other views though.

ronin
2017-Apr-10, 05:34 AM
How does the material that forms a new star overcome angular momentum as the nebula if forms from begins to collapse and spin?

Noclevername
2017-Apr-10, 05:40 AM
How does the material that forms a new star overcome angular momentum as the nebula if forms from begins to collapse and spin?

A tornado or toilet flush don't have to worry about angular momentum, do they?

profloater
2017-Apr-10, 08:33 AM
How does the material that forms a new star overcome angular momentum as the nebula if forms from begins to collapse and spin?

in terms of the OP angular momentum and linear momentum are linked. In the case of fluids there are pressures so that the centre of a vortex is at lower pressure than the surrounding fluid and that pressure difference causes centripetal movement. But as density goes down the link between particles is less clear if they don't hit each other. Eventually the mean free path is so long that you need another explanation which is gravity. If you imagine a "free" particle with momentum experiencing a net gravity sideways force its path changes to a curve. This effect clearly tends to focus a group of particles increasing density. However it is true for all particles and they are not all travelling the same paths so impacts start to occur. The net momentum and the net angular momentum begin the take over from long mean free paths. A travelling probe in free fall can use large masses to swingshot its own trajectory, thereby achieving a large change in momentum vector by a smaller navigational correction. Once free of Earth, a probe aimed at say the moon should be able to find a trajectory that would set it on course for the sun, hopefully the reaction on the moon is then too small to force it out of its orbit.

Jens
2017-Apr-10, 08:54 AM
A tornado or toilet flush don't have to worry about angular momentum, do they?

You seem to be dismissing it, but it is a real issue in the mainstream field of star formation, called the angular momentum problem (https://en.wikipedia.org/wiki/Angular_momentum_problem). In fact it just happens that I wrote a press release (http://www.riken.jp/en/pr/press/2017/20170210_1/) for a researcher who is doing research in that very area. She hypothesizes that a sort of shock wave develops and that some particles are case either upward or downward (our of the plane of the disk) so that that momentum takes the energy that allows the particles to slow down. But it's not a simple issue. It is likely related to the fact that the sun, while having 99% of the mass of the solar system, only has 3% of the angular momentum.

ngc3314
2017-Apr-12, 01:53 PM
A tornado or toilet flush don't have to worry about angular momentum, do they?

AIUI (and IANA Meteorologist), a tornado happens precisely because the angular momentum gets trapped in material in a small volume and takes time to dissipate to nonthreatening levels. In the aftermath of an EF-4 around here, I was struck to see that the broken-off trees had not been really snapped off, the crowns had been twisted off. That much wind shear betrays a lot of angular momentum.

ronin
2017-Apr-13, 06:11 PM
You seem to be dismissing it, but it is a real issue in the mainstream field of star formation, called the angular momentum problem (https://en.wikipedia.org/wiki/Angular_momentum_problem). In fact it just happens that I wrote a press release (http://www.riken.jp/en/pr/press/2017/20170210_1/) for a researcher who is doing research in that very area. She hypothesizes that a sort of shock wave develops and that some particles are case either upward or downward (our of the plane of the disk) so that that momentum takes the energy that allows the particles to slow down. But it's not a simple issue. It is likely related to the fact that the sun, while having 99% of the mass of the solar system, only has 3% of the angular momentum.

Thanks.

Hornblower
2017-Apr-13, 06:44 PM
It's an interesting question, albeit a bit unrelated to the original question. I imagine that if you launched a probe directly into the sun, it would gradually evaporate, and I wonder what would happen to the gas particles. It might well be that the lighter atoms will be cast away, but that the heavier ones will may their way into the interior of the sun. I'd be happy to hear other views though.

Suppose a load of nuclear waste was inbound on a course that would take it to the photosphere if it did not evaporate first. I would expect evaporating material to be pushed back like the tail of a comet, and that it would be so widely dispersed that it would be no threat to us on Planet Earth. It would be interesting to get an engineering estimate of how deep a steel container would penetrate before evaporating completely.

Jens
2017-Apr-13, 10:50 PM
Suppose a load of nuclear waste was inbound on a course that would take it to the photosphere if it did not evaporate first. I would expect evaporating material to be pushed back like the tail of a comet, and that it would be so widely dispersed that it would be no threat to us on Planet Earth. It would be interesting to get an engineering estimate of how deep a steel container would penetrate before evaporating completely.

I don't think they would be pushed back out but I could be wrong. Even if they were it would be a very diffuse cloud, so I don't see why it would pose a threat. There is already 4 billion tons of uranium in the oceans.

DaveC426913
2017-Apr-13, 11:42 PM
There is the question of how much a given mass of material would have to disintegrate for the solar wind to be able to affect it.

I doubt any object - altered for the purpose dropping into the sun - would vaporize much before it made starfall.

Consider best/worst case of a chunk of uranium - each atom 238 times more massive than hydrogen - as a 50kg ball of metal. How much could vaporize in the fall to the surface?

Especially if it contained in an ablative casing that protects its integrity all the way down.


I'm not even entirely sure that atomic uranium as a gas is light enough to get blown away by the wind.

After all - that is why the rocky planets are near the sun, and the gaseous planets are farther out. It can blow gasses, but not iron and nickel not so much.



Besides, you could always set its trajectory to make impact on the side of the sun such that it dissipates over a year while Earth orbits.