What-If 0146: "Stop Jupiter"

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What-If 0146: "Stop Jupiter"

Postby Soupspoon » Wed Feb 17, 2016 1:12 pm UTC

Stop Jupiter

Dillon wrote:I understand that the New Horizons craft used gravity assist from Jupiter to increase its speed on the way to Pluto. I also understand that by doing this, Jupiter slowed down very slightly. How many flyby runs would it take to stop Jupiter completely?

xkcd wrote:More than we can afford.


Image

For a long time, I misunderstood this list, and thought I was supposed to worry about the things on it in reverse order.


Although I wonder if, in the second picture's titletext, Randall meant to write "IPV6"?
...I also couldn't find popupnote #5, it skips to #6,
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Re: What-If 0146: "Stop Jupiter"

Postby BioTronic » Wed Feb 17, 2016 1:20 pm UTC

Soupspoon wrote:(Although I wonder if, in the second picture's titletext, Randall meant to write "IPV6"?)


I wonder where footnote 5 ran off to.

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Re: What-If 0146: "Stop Jupiter"

Postby Minstrel » Wed Feb 17, 2016 1:53 pm UTC

If you want to stop a truck with tennis balls, the tennis balls need more momentum than the truck, which means they need to be extremely heavy, fast, or both.


I notice he didn't address the extremely fast aspect though. Is there a way we could get New Horizons going really fast? Putting aside little issues like surviving impact with space dust, could we speed up the craft to relativistic speeds where its mass would increase? I know it takes exponentially more energy to go faster as mass increases, so again we'd probably run into the issue of using up earth's resources just trying to speed the damn thing up, but what if we used something like solar sails and kept swinging it around the sun/Jupiter over and over, adding on speed each time?

Disclaimer: I'm not a physics person so I'm sure this wouldn't work conceptually, but I'd be interested in exactly why: whether it's a non-starter due to my misunderstanding of physics, or something more specific like needing too big a sail or needing more time to get up to speed than the solar system has left.

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Re: What-If 0146: "Stop Jupiter"

Postby cellocgw » Wed Feb 17, 2016 2:38 pm UTC

Minstrel wrote:
If you want to stop a truck with tennis balls, the tennis balls need more momentum than the truck, which means they need to be extremely heavy, fast, or both.


I notice he didn't address the extremely fast aspect though. Is there a way we could get New Horizons going really fast? Putting aside little issues like surviving impact with space dust, could we speed up the craft to relativistic speeds where its mass would increase? I know it takes exponentially more energy to go faster as mass increases, so again we'd probably run into the issue of using up earth's resources just trying to speed the damn thing up, but what if we used something like solar sails and kept swinging it around the sun/Jupiter over and over, adding on speed each time?

Disclaimer: I'm not a physics person so I'm sure this wouldn't work conceptually, but I'd be interested in exactly why: whether it's a non-starter due to my misunderstanding of physics, or something more specific like needing too big a sail or needing more time to get up to speed than the solar system has left.


I think the main problem is that the "slingshot" maneuver works only on hyperbolic paths, i.e. if you try to set up an elliptical path so you can do multiple passbys, you'll get bigger and bigger elliptical orbits but not escape. So possibly you could plan things so the [actual number of orbits required left as a homework exercise]-th orbit will intersect Jupiter and slingshot the crap out of that gasbag.
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Re: What-If 0146: "Stop Jupiter"

Postby hamjudo » Wed Feb 17, 2016 3:00 pm UTC

I still want to know the answer to the original what if question.

Assume that some alien civilisation wants to cause Jupiter to impact our sun. These distant aliens have developed a mass driver that can launch an insane number of payloads that will reach our solar system with a trajectory such that each one alters Jupiter's orbit just as much as the New Horizons mission did.

We don't need a justification for a What If, just a scenario. The payloads are entering our solar system from far away. They will have a much higher velocity than an Earth launched payload. Does this mean the scenario is much more plausible, because it uses much less mass?

The answer will vary a lot based on details that haven't been specified. I assume it would take much less energy, and therefore fewer payloads to make Jupiter's orbit so highly elliptical that it impacts the sun with more kinetic energy than if it was "just" a Jupiter mass object dropped into the Sun from the same distance as Jupiter's current position in orbit. Also, it will take less energy if they wait until the Sun becomes a red giant. I am not sure if spreading the operation over a billion years will save any energy. It would make the payload launch rate more plausible. In any case, any answer is good for me, just describe the conditions you use and give answer in terms of quantity of New Horizon equivalents.

Note that the aliens were not influenced by human society at all. Given the distances and velocities involved, the payloads flight time vastly exceeds the length of human civilization.

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Re: What-If 0146: "Stop Jupiter"

Postby ramblinjd » Wed Feb 17, 2016 5:13 pm UTC

Did anybody else notice the tennis ball says Pen 15 (penis)?

Image

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Re: What-If 0146: "Stop Jupiter"

Postby Kyorinrin » Wed Feb 17, 2016 5:43 pm UTC

Would it not make more sense to use jupiter to speed up a launch to any of the other three gas giants, the use gravity breaking to loop back to jupiter? Slowing down jupiter and speeding up saturn? Or the reverse if you wanted a collision.

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Re: What-If 0146: "Stop Jupiter"

Postby SDK » Wed Feb 17, 2016 6:13 pm UTC

hamjudo wrote:I still want to know the answer to the original what if question.

Answering that would have been long and boring. He probably just didn't want to dive into the complex math and change the entire content of the article.

New Horizons slowed Jupiter by 10-21 m/s, right? Jupiter is moving at 13.07 km/s. Therefore, you need 1.3x1025 (13 septillion) New Horizons to stop it. Right?

No, you need quite a few more than that. This is all based on how much energy New Horizons is able to take away while it gains that 4000 m/s. But as Jupiter slows (particularly once it gets below 4000 m/s itself), the probes will be extracting less and less... until eventually their own speed would match Jupiter's and nothing much happens (in an absolute sense, at least). To finish it off, you'd need to start in on angles of approach, the probe's initial speed and all that other crap that no one really wants to talk or read about.

Now take your several septillion spacecraft and be happy that he didn't give us more.
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Re: What-If 0146: "Stop Jupiter"

Postby Various Varieties » Wed Feb 17, 2016 8:31 pm UTC

Things to worry about

6. Velociraptors

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Re: What-If 0146: "Stop Jupiter"

Postby Yablo » Wed Feb 17, 2016 9:01 pm UTC

ramblinjd wrote:Did anybody else notice the tennis ball says Pen 15 (penis)?

That's what I popped in to mention. Thanks for taking the wind out my sail and raining on my parade.
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Re: What-If 0146: "Stop Jupiter"

Postby Gan_HOPE326 » Wed Feb 17, 2016 9:29 pm UTC

I love imagining that this would be an actual issue environmental activists would protest about in an hypothetical far future scenario in which the Sol System is the main trade hub at the core of the powerful Terran Galactic Empire, with thousands of freighters and war frigates using Jupiter daily to get flung out of the internal system in order to enter the area where it's safe to go warp speed. Though of course you could counter-balance that by also using Jupiter to slow down starships *entering* the system, if you carefully plan the speed vectors.

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Re: What-If 0146: "Stop Jupiter"

Postby leafar » Wed Feb 17, 2016 10:08 pm UTC

Earth weighs almost exactly pi milliJupiters

Am I the only one who read that, went straight to Wolfram Alpha, and was quite amazed at that result?

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Re: What-If 0146: "Stop Jupiter"

Postby Sableagle » Wed Feb 17, 2016 10:08 pm UTC

Various Varieties wrote:Things to worry about

6. Velociraptors



That was number 0 on the list. We're still lookign into why the list is only shown from 1 onwards.

Gan_HOPE326 wrote:I love imagining that this would be an actual issue environmental activists would protest about in an hypothetical far future scenario in which the Sol System is the main trade hub at the core of the powerful Terran Galactic Empire, with thousands of freighters and war frigates using Jupiter daily to get flung out of the internal system in order to enter the area where it's safe to go warp speed. Though of course you could counter-balance that by also using Jupiter to slow down starships *entering* the system, if you carefully plan the speed vectors.

That brings up a "near-miss" scenario and a half, doesn't it? Incoming and outgoing ships doing 20 km/s at right angles wouldn't have much time to see each other and do something about it.

So ... that giant tennis ball? Let's tone the speed down a little from world record service speeds and call it 150mph, and assume the truck's saving fuel by doing 50mph, so the maths get easier and the ball simple has to weigh one third as much as the truck. That makes it maybe a 10t ball. That makes it about 172,414 times a standard tennis ball, so 55.66 times the size, or 3.729m in diameter (assuming wall thickness scales with diameter). Okay, so it's not going to roll right over a truck, but just how much damage would that thing do to the truck in the process of stopping it?

What were the alternatives to making it bigger? Oh, yeah, density and velocity. So, er, a 10t tennis ball 6.6cm wide doing 241.4 km/h? I suspect that'd just punch right through a truck. 66,431 g/cm^3 is a bit ott. I doubt the road surface would support it after it stopped, either. Velocity, then. 57.7g tennis ball versus 30t truck, 1:521739 mass ratio so equal momentum if the ball's going 521,739 times as fast as the truck. 11,621,490.470 m/s, to get all scientific with the units, or 0.038765c. Heh. "Dear Randall, what would happen in a baseball batter driving an articulated lorry tried to hit a tennis ball pitched at 3.9% the speed of light?" Well, er, 4,053,590,770,300J of kinetic energy, equivalent to 968.8t TNT, so I think we can be fairly sure the truck would not survive that.
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Re: What-If 0146: "Stop Jupiter"

Postby ucim » Wed Feb 17, 2016 10:19 pm UTC

hamjudo wrote:I still want to know the answer to the original what if question.
Well, to zeroth order, as many spacecraft as the mass of Jupiter itself.

The spaceship is going to approach Jupiter with some orbital direction speed (ODS)
Spoiler:
the component of velocity parallel to the direction of Jupiter's orbit). Slower is better - faster and we will slingshot Jupiter instead of the other way around. Negative is a possibility, but the numbers are still pretty big)
Consider the (symmetric) case where we send one Jupter-mass spacecraft (JMC) in an orbit that is almost exactly opposite Jupiter (negative one ODS). When they meet and either slingshot each other, or crash into each other, ODS will be zero, and two Jupitermass will plummet into the sun.
Spoiler:
If we do the slingshot thing instead of the crash thing, we'd arrange Jupiter to be slingshot 90 degrees towards the sun, and the JMC to be slinshot tau/4 radians away from the sun, where it will eventually (not having escape velocity) fall back into the sun umpteen years later. Exercise for the reader: Would it reach the edge of the solar system?
Now, instead of one JMC, we could send 1000 milli-JMCs to accomplish the same effect. The number of NHs that we'd need to accomplish the same effect would be gotten by dividing one JMC mass by one NH mass, an exercise I'll leave to the reader. Hint - it's not a small number.

This isn't, of course, the only solution, but it will give you an idea of the order of magnitude involved. The trick is conserving momentum as well as energy, while leaving one body (Jupiter) with zero ODS.

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Re: What-If 0146: "Stop Jupiter"

Postby nowhereman » Wed Feb 17, 2016 11:54 pm UTC

hamjudo wrote:I still want to know the answer to the original what if question.

Assume that some alien civilisation wants to cause Jupiter to impact our sun. These distant aliens have developed a mass driver that can launch an insane number of payloads that will reach our solar system with a trajectory such that each one alters Jupiter's orbit just as much as the New Horizons mission did.

We don't need a justification for a What If, just a scenario. The payloads are entering our solar system from far away. They will have a much higher velocity than an Earth launched payload. Does this mean the scenario is much more plausible, because it uses much less mass?

The answer will vary a lot based on details that haven't been specified. I assume it would take much less energy, and therefore fewer payloads to make Jupiter's orbit so highly elliptical that it impacts the sun with more kinetic energy than if it was "just" a Jupiter mass object dropped into the Sun from the same distance as Jupiter's current position in orbit. Also, it will take less energy if they wait until the Sun becomes a red giant. I am not sure if spreading the operation over a billion years will save any energy. It would make the payload launch rate more plausible. In any case, any answer is good for me, just describe the conditions you use and give answer in terms of quantity of New Horizon equivalents.

Note that the aliens were not influenced by human society at all. Given the distances and velocities involved, the payloads flight time vastly exceeds the length of human civilization.


To understand what is going on when a gravity assist maneuver is performed, it is useful to think about the three body problem. Jupiter has a linear velocity around the Sun of about 13.1 km/s. If a stationary object were sitting in front of Jupiter when Jupiter moves into its path, we would find that the object would fall in (but likely wouldn't collide with Jupiter unless the object were RIGHT in Jupiter's path). If we restrict our observations to the stationary object and Jupiter alone, we would see the object enter Jupiter's influence, orbit around Jupiter and then leave the way it came. When we look at this motion relative to the third body (the Sun) we would see the smaller body rotate around and quickly leave Jupiter behind at a speed around 2*Jupiter's linear velocity. This is obviously simplified heavily. The actual velocity change would depend upon relative mass of the two objects, and the angle of entry.

The important things to gather from this is that the velocity gained by the horizon's probes (or the velocity lost by Jupiter) is dependent upon the momentum of the two objects (which must be conserved) and the velocity of Jupiter. As probes pass by Jupiter, its momentum is lost and it slows down. This means that each probe will take a little less momentum than the previous probe. The number of probes required would probably be equal to the mass of Jupiter, or even greater. (Actually, my logic seems to indicate that you could never truly stop Jupiter using this method unless you simply mean slowing it down enough to impact the Sun. This seems improbable, so while this simplification works for awhile, I am sure it breaks down for large enough numbers of probes.)

However, since these hypothetical aliens only care about stopping Jupiter (and presumably don't care if we continue to exist afterwards), they could try actually hitting Jupiter with the new horizons probe. Given that Jupiter out weighs the probe by 26 orders of magnitude, it is clear that this probe would have to be traveling very close to the speed of light. If you try to use non-relativistic equations for momentum, you will find that the probe would have to travel millions of times the speed of light. So ultimately we need the relativistic equations to solve this problem.

The problem is that Wolfram Alpha helpfully gives up while trying to calculate this velocity. We ultimately need a gamma value around 10^18. This value is so ridiculously large, that the probe would be traveling much, much faster than the Oh My God particle. In fact, the closest I could massage Wolfram Alpha to was .99 999 999 999 999 999. The energy in the probe would probably exceed the gravitational binding energy of Jupiter. If not, I would wager it is within an order of magnitude.

A weird possibility (though I am not sure as I am too lazy to break out the big guns calculator-wise) is that the collision would be enough to vaporize Jupiter and perhaps some of its closer neighbors. I remember solving this problem on a lark once. The question was how large an explosion would the Earth need to have to destroy the Sun. The answer was around the size of 500 supernovas. It is that large because 1: The Sun is huge [citation needed] 2: The Earth is far away 3: Energy deposited into the Sun would be proportional to the solid angle of the Sun relative to the Earth. Since this explosion is so completely ridiculous that I cannot get answers out (let alone sensible ones), it occurs to me that the aliens might destroy the solar system in their insane desire to stop Jupiter. Regardless of the outcome of this explosion, the resultant high energy gas cloud that used to be Jupiter would have a relative velocity to the Sun of zero.
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Re: What-If 0146: "Stop Jupiter"

Postby Soupspoon » Thu Feb 18, 2016 1:10 am UTC

The effect is surely in line with both the proximity of the 'slingshotter' and 'slingshottee' (proportional to the inverse square of the centre-to-centre distance?) and the amount of time at that proximity (proportional?1).

An extremely energetic pass-by has less 'nearby time', and so I'm not sure if sending such a projectile at a more significant (relative/sun-relative?) velocity is going to help, if it passes the point of greatest influence2 so much quicker. To overcome that, you need to aim your projectile closer. And then you have the problem of atmosphere-skimming, because Jupiter isn't a point-mass that can be passed arbitrarily close.

At the very least, you need to consider the trade-offs that come from the Jovian aerobraking manoeuvre itself, when you do that. Which seems to send us into the territory of Could we speed up Earth's rotation, and of course sending in projectiles to directly impart velocity upon the planet (each below the limit of any significant 'exfoliation' of the atmosphere... another problem!) and changes the scenario. So we'd ideally want to avoid that and restrict our flybys to only so close as to stay beyond all but the most tenuous atmosphere. Or at least configure the probe to be more aerodynamic (c.f. "Night Glider" orientation modes, and other variations on this, for the ISS solar panels) so it remains an insignificant aspect of the calculations.

So (and, even assuming I've been on the money so far, I'll let someone else do the exact maths) there's probably a maximum fly-by speed that would actually be useful in the momentum-bleeding of Jupiter, for any given fly-by path by any given mass/cross-section of object. Which sounds like a complicated optimum to work out, if you're not just going to send a Pinto-sized probe at near-'c' velocity straight in against Jupiter and count it as a success when the average accumulated momentum of the resulting rapidly (and, in parts, relativistically) expanding debris cloud is calculated as now having effectively zero orbital velocity... ;)


1 If 'held' in position, but as there's an approach/pass/withdraw curve, it probably ends up being an integration of the changing centre-to-centre (multiplied by the effective of the operating angle at dt?) force, as each body's trajectory changes the exact interaction.

2 The trajectory line-segment where all points have above-mean mutual gravitational attraction, compared with the whole path?

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Re: What-If 0146: "Stop Jupiter"

Postby rmsgrey » Thu Feb 18, 2016 3:48 am UTC

nowhereman wrote:The problem is that Wolfram Alpha helpfully gives up while trying to calculate this velocity. We ultimately need a gamma value around 10^18. This value is so ridiculously large, that the probe would be traveling much, much faster than the Oh My God particle. In fact, the closest I could massage Wolfram Alpha to was .99 999 999 999 999 999. The energy in the probe would probably exceed the gravitational binding energy of Jupiter. If not, I would wager it is within an order of magnitude.


How much of the energy would transfer into Jupiter's bulk, and how much would just punch through?

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Re: What-If 0146: "Stop Jupiter"

Postby Dr What » Thu Feb 18, 2016 5:58 am UTC

by the time the Sun goes supernova


WAT?
The sun doesn't go supernova. It doesn't have enough mass.

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Re: What-If 0146: "Stop Jupiter"

Postby Pfhorrest » Thu Feb 18, 2016 7:15 am UTC

i was wondering about that
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Re: What-If 0146: "Stop Jupiter"

Postby Kyorinrin » Thu Feb 18, 2016 7:19 am UTC

Now I'm curious could you tap Jupiter's magneto sphere for power and it's atmosphere for fuel and make an orbital thruster of sorts.

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Re: What-If 0146: "Stop Jupiter"

Postby wayne » Thu Feb 18, 2016 9:36 am UTC

Sableagle wrote: Let's tone the speed down a little from world record service speeds and call it 150mph, and assume the truck's saving fuel by doing 50mph, so the maths get easier and the ball simple has to weigh one third as much as the truck.


Actually, energy goes up by the square of the speed. At 1/3 the weight (mass) of the truck, and three times the speed, your ball would have three times the energy of the truck.

(energy = (speed)^2 x mass / 2)

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Re: What-If 0146: "Stop Jupiter"

Postby Neil_Boekend » Thu Feb 18, 2016 10:14 am UTC

Kyorinrin wrote:Now I'm curious could you tap Jupiter's magneto sphere for power and it's atmosphere for fuel and make an orbital thruster of sorts.

Well, Jupiter's atmosphere is mainly hydrogen. 0.0115% of that is deuterium. Deuterium is a fusion fuel (assuming you would be able to solve that pesky momentum issue with D-D fusion) so you could, presumably, use Jupiter's upper atmosphere as a fuel source. You could use an electrodynamic tether to stay in orbit despite atmospheric drag (seems quite feasible with Jupiter's massive massive magnetic field). That fuel could either be used to generate electricity to power a huge ion drive or you could use it to build nuclear bombs for a big ass Orion class spaceship.
In a future civilization this may be used as a fuel station, launching tanks to passing interstellar craft. Or as a pit-stop, where the interstellar spaceship docks to refuel (that would require it to be outside of the Van Allen belts though).
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Re: What-If 0146: "Stop Jupiter"

Postby dtilque » Thu Feb 18, 2016 10:27 am UTC

It should be noted that New Horizons is not the first time we've stolen momentum from Jupiter. In fact, it's the 7th. Pioneer 10 and 11, Voyager 1 & 2, Ulysses, and Cassini all pulled that maneuver at Jupiter as well. So we're well on our way to tossing old Jove into the Sun. Just give us a few more billion years...

And that's not all. There've been missions that stole momentum from Mars, Venus, and even the Earth. Pioneer 10 & 11 and Voyager 1 stole some from Saturn too. Voyager 2 stole some from Saturn, Uranus and maybe Neptune (not sure about that -- I think it may have lost momentum at Neptune). I think Cassini and Galileo also pulled it off within the satellite systems of Saturn and Jupiter, respectively. If we keep this up, we're going to totally ruin the Solar System.
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Re: What-If 0146: "Stop Jupiter"

Postby Jeff_UK » Thu Feb 18, 2016 11:21 am UTC

The situation is similar to the one in the tennis ball analogy from earlier


Am I being thick, what tennis ball analogy is this referring to?
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Re: What-If 0146: "Stop Jupiter"

Postby Sableagle » Thu Feb 18, 2016 11:24 am UTC

wayne wrote:
Sableagle wrote: Let's tone the speed down a little from world record service speeds and call it 150mph, and assume the truck's saving fuel by doing 50mph, so the maths get easier and the ball simple has to weigh one third as much as the truck.


Actually, energy goes up by the square of the speed. At 1/3 the weight (mass) of the truck, and three times the speed, your ball would have three times the energy of the truck.

(energy = (speed)^2 x mass / 2)


Well, yes, but to stop the truck we need the same momentum, don't we? Kinetic energy goes off in other forms, but momentum is conserved. That's why 10 .45ACP and 10 5.56x45mm hitting steel plates on skateboards will each shove it back at the same speed but the 5.56 will make more of a mess of the skateboard below the front of the plate with all the little metal splinters that fly off.
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Re: What-If 0146: "Stop Jupiter"

Postby Echo244 » Thu Feb 18, 2016 11:25 am UTC

Jeff_UK wrote:
The situation is similar to the one in the tennis ball analogy from earlier


Am I being thick, what tennis ball analogy is this referring to?


Stopping a truck/lorry with a tennis ball.

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Re: What-If 0146: "Stop Jupiter"

Postby Jeff_UK » Thu Feb 18, 2016 11:37 am UTC

Echo244 wrote:
Jeff_UK wrote:
The situation is similar to the one in the tennis ball analogy from earlier


Am I being thick, what tennis ball analogy is this referring to?


Stopping a truck/lorry with a tennis ball.

ramblinjd wrote:Image


That's later, not earlier, I think I answered it myself though, I think he's referring to https://what-if.xkcd.com/38/ (Voyager)

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Re: What-If 0146: "Stop Jupiter"

Postby TheMasonX » Thu Feb 18, 2016 1:30 pm UTC

Soupspoon wrote:Although I wonder if, in the second picture's titletext, Randall meant to write "IPV6"?


I'm almost certain of it. Just to be sure, I even checked the numbers, and samsclass.info/ipv6/exhaustion.htm (spam blocked 'cause I'm new) puts the estimate around then too.

leafar wrote:
Earth weighs almost exactly pi milliJupiters

Am I the only one who read that, went straight to Wolfram Alpha, and was quite amazed at that result?

No, I did that before continuing as well.

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Re: What-If 0146: "Stop Jupiter"

Postby nowhereman » Thu Feb 18, 2016 3:30 pm UTC

rmsgrey wrote:
nowhereman wrote:The problem is that Wolfram Alpha helpfully gives up while trying to calculate this velocity. We ultimately need a gamma value around 10^18. This value is so ridiculously large, that the probe would be traveling much, much faster than the Oh My God particle. In fact, the closest I could massage Wolfram Alpha to was .99 999 999 999 999 999. The energy in the probe would probably exceed the gravitational binding energy of Jupiter. If not, I would wager it is within an order of magnitude.


How much of the energy would transfer into Jupiter's bulk, and how much would just punch through?


Newton is useful in this case. As demonstrated centuries ago, impact depth is not proportional to velocity, but instead to the relative densities and lengths of the objects colliding. This tells us that the probe must give up all of its momentum before exiting Jupiter (and likely before it reaches the "surface" of Jupiter). The energy would spread conically in Jupiter until either a) Jupiter has most (if not all) of itself blown up. Imagine a large jet of superheated gasses being ejected from the other end of Jupiter. I do not understand the effects of high energy impacts on planetary geology well enough to determine how much of the planet will absorb energy, but I imagine it would be most of it. b) Jupiter absorbs all of the energy and heats up greatly (and falls into the Sun of course).

In this case, Jupiter will explode. Now that I am not lazy, I sat down and calculated the relativistic energy of the probe and got the answer 3.622×10^36 joules. Wolfram Alpha helpfully tells me this is the energy of solar output for 300 years (God I love Wolfram Alpha). The gravitational binding energy of Jupiter is 2.086×10^36 joules. So the probe would have approximately 150% of the required energy to blow up Jupiter! I am very excited at the prospect of blowing up planets. Never give me dangerous equipment.

The energy released however would not be enough to destroy the solar system. However, I cannot imagine that having bits of Jupiter rain on us would be good for the environment.

Neil_Boekend wrote:
Kyorinrin wrote:Now I'm curious could you tap Jupiter's magneto sphere for power and it's atmosphere for fuel and make an orbital thruster of sorts.

Well, Jupiter's atmosphere is mainly hydrogen. 0.0115% of that is deuterium. Deuterium is a fusion fuel (assuming you would be able to solve that pesky momentum issue with D-D fusion) so you could, presumably, use Jupiter's upper atmosphere as a fuel source. You could use an electrodynamic tether to stay in orbit despite atmospheric drag (seems quite feasible with Jupiter's massive massive magnetic field). That fuel could either be used to generate electricity to power a huge ion drive or you could use it to build nuclear bombs for a big ass Orion class spaceship.
In a future civilization this may be used as a fuel station, launching tanks to passing interstellar craft. Or as a pit-stop, where the interstellar spaceship docks to refuel (that would require it to be outside of the Van Allen belts though).


This would be insanely hard. First, fusion requires either extreme temperatures, or pressures (or both). Unless you can manipulate the core of Jupiter, you will need to use extreme temperatures. Since you cannot use lasers to penetrate the atmosphere of Jupiter so as to create fusion on the surface, you will need to transfer the gasses to a separate reaction area. Then you would have to launch these gasses out. Your idea of using the magnetic field is a good one, but I am not sure how much energy you would need to power this Jupiter rocket. Ultimately you are taking energy from Jupiter's rotational momentum about its axis, and transferring it to the rotational momentum about the sun. Jupiter has 4.057×10^38 joule seconds of angular momentum though, so I think you can do it this way (even without accounting for extra left over energy from fusion). Note that I do not approve of this idea though. It doesn't explode enough.
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Re: What-If 0146: "Stop Jupiter"

Postby Shadowman615 » Thu Feb 18, 2016 3:44 pm UTC

Wait, wait, so a spacecraft that travelled to pluto was powered by plutonium!? There's a bit of awesomeness in there somewhere...

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Re: What-If 0146: "Stop Jupiter"

Postby Neil_Boekend » Thu Feb 18, 2016 4:04 pm UTC

nowhereman wrote:
Neil_Boekend wrote:
Kyorinrin wrote:Now I'm curious could you tap Jupiter's magneto sphere for power and it's atmosphere for fuel and make an orbital thruster of sorts.

Well, Jupiter's atmosphere is mainly hydrogen. 0.0115% of that is deuterium. Deuterium is a fusion fuel (assuming you would be able to solve that pesky momentum issue with D-D fusion) so you could, presumably, use Jupiter's upper atmosphere as a fuel source. You could use an electrodynamic tether to stay in orbit despite atmospheric drag (seems quite feasible with Jupiter's massive massive magnetic field). That fuel could either be used to generate electricity to power a huge ion drive or you could use it to build nuclear bombs for a big ass Orion class spaceship.
In a future civilization this may be used as a fuel station, launching tanks to passing interstellar craft. Or as a pit-stop, where the interstellar spaceship docks to refuel (that would require it to be outside of the Van Allen belts though).


This would be insanely hard. First, fusion requires either extreme temperatures, or pressures (or both). Unless you can manipulate the core of Jupiter, you will need to use extreme temperatures. Since you cannot use lasers to penetrate the atmosphere of Jupiter so as to create fusion on the surface, you will need to transfer the gasses to a separate reaction area. Then you would have to launch these gasses out. Your idea of using the magnetic field is a good one, but I am not sure how much energy you would need to power this Jupiter rocket. Ultimately you are taking energy from Jupiter's rotational momentum about its axis, and transferring it to the rotational momentum about the sun. Jupiter has 4.057×10^38 joule seconds of angular momentum though, so I think you can do it this way (even without accounting for extra left over energy from fusion). Note that I do not approve of this idea though. It doesn't explode enough.

First off: An Orion class spaceship with hydrogen bombs instead of fission bombs doesn't explode enough for you? You, Sir, are hard to appease.
Second: Kyorinrin's remark caused me to muse a bit and go off a tangent. I was thinking of using the energy to do something useful, as in leave our solar system.
Third: a big spaceship would be able to use a fusion reactor. I am not talking about ships the size of the current crop. I am talking about 100m diameter built-in-orbit generation ships that are meant to accelerate to significant fractions of light speed by having a drive they can just leave "on". 1G acceleration for a year gives you a significant fraction of light speed. I am also not proposing to do this this century.
Fourth: You can de-orbit Jupiter by employing a fusion candle. That is a huge pillar with a fusion powered super engine at each end. One sticks into the Jupiter atmosphere and keeps it from falling. The other accelerates gasses to far beyond escape speed. The Jupiter atmosphere is both the fusion fuel and the reaction mass.
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Re: What-If 0146: "Stop Jupiter"

Postby ps.02 » Thu Feb 18, 2016 5:35 pm UTC

Kyorinrin wrote:Now I'm curious could you tap Jupiter's magneto sphere for power and it's atmosphere for fuel and make an orbital thruster of sorts.

I liked Howard Tayler's explanation (text note below the comic) of how to move a gas giant.

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Re: What-If 0146: "Stop Jupiter"

Postby rmsgrey » Thu Feb 18, 2016 6:05 pm UTC

nowhereman wrote:
rmsgrey wrote:
nowhereman wrote:The problem is that Wolfram Alpha helpfully gives up while trying to calculate this velocity. We ultimately need a gamma value around 10^18. This value is so ridiculously large, that the probe would be traveling much, much faster than the Oh My God particle. In fact, the closest I could massage Wolfram Alpha to was .99 999 999 999 999 999. The energy in the probe would probably exceed the gravitational binding energy of Jupiter. If not, I would wager it is within an order of magnitude.


How much of the energy would transfer into Jupiter's bulk, and how much would just punch through?


Newton is useful in this case. As demonstrated centuries ago, impact depth is not proportional to velocity, but instead to the relative densities and lengths of the objects colliding. This tells us that the probe must give up all of its momentum before exiting Jupiter (and likely before it reaches the "surface" of Jupiter). The energy would spread conically in Jupiter until either a) Jupiter has most (if not all) of itself blown up. Imagine a large jet of superheated gasses being ejected from the other end of Jupiter. I do not understand the effects of high energy impacts on planetary geology well enough to determine how much of the planet will absorb energy, but I imagine it would be most of it. b) Jupiter absorbs all of the energy and heats up greatly (and falls into the Sun of course).


I'm not convinced that Newton's approximation remains valid for arbitrarily high initial momentum, but I am lazy, so I'm not going to bother trying to figure out a more detailed model to run numbers for...

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Re: What-If 0146: "Stop Jupiter"

Postby Pfhorrest » Thu Feb 18, 2016 6:40 pm UTC

nowhereman wrote:The energy released however would not be enough to destroy the solar system. However, I cannot imagine that having bits of Jupiter rain on us would be good for the environment.

Would the mass of Jupiter not just scatter out in a huge ring out at Jupiter's orbital distance? (And if so, would it not eventually coalesce back into a Jupiter again, and if so, how does that reconcile with having overcome the gravitational binding energy of that mass if it eventually falls back together again under gravity?)
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Re: What-If 0146: "Stop Jupiter"

Postby SuicideJunkie » Thu Feb 18, 2016 7:09 pm UTC

The gas would emit lots and lots of heat before, during, and after it coalesces back into Jupiter II: Red Spottier

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Re: What-If 0146: "Stop Jupiter"

Postby nowhereman » Thu Feb 18, 2016 8:03 pm UTC

Pfhorrest wrote:
nowhereman wrote:The energy released however would not be enough to destroy the solar system. However, I cannot imagine that having bits of Jupiter rain on us would be good for the environment.

Would the mass of Jupiter not just scatter out in a huge ring out at Jupiter's orbital distance? (And if so, would it not eventually coalesce back into a Jupiter again, and if so, how does that reconcile with having overcome the gravitational binding energy of that mass if it eventually falls back together again under gravity?)


The gravitational binding energy is the amount of energy required to take every single bit of a uniform spherical object (a decent approximation for a planet) and remove it to infinity (every piece has a hyperbolic trajectory). In other words, you blow up a planet with this much energy and it will never come back. Even if there weren't planets, and other astronomical bodies to prevent the gasses from reforming as Jupiter, Jupiter would never reform again. As for what would happen to the rest of Jupiter, I am not certain. While this is enough energy to destory Jupiter for certain, it might not be enough to leave the solar system. Given that the escape velocity from Jupiter is 55m/s, and the Solar escape velocity at that distance is 18m/s it might create a shell of heated gases surrounding our solar system (like what you would see with a supernova... but smaller). Some quantity of that would collide with the Earth and do who knows what to our environment. I seriously don't know the answer to that. We would heat up slightly from the gasses and the composition of our atmosphere might be affected slightly. I doubt it would be a large effect though. We are really far away from Jupiter.

rmsgrey wrote:
nowhereman wrote:
rmsgrey wrote:
nowhereman wrote:The problem is that Wolfram Alpha helpfully gives up while trying to calculate this velocity. We ultimately need a gamma value around 10^18. This value is so ridiculously large, that the probe would be traveling much, much faster than the Oh My God particle. In fact, the closest I could massage Wolfram Alpha to was .99 999 999 999 999 999. The energy in the probe would probably exceed the gravitational binding energy of Jupiter. If not, I would wager it is within an order of magnitude.


How much of the energy would transfer into Jupiter's bulk, and how much would just punch through?


Newton is useful in this case. As demonstrated centuries ago, impact depth is not proportional to velocity, but instead to the relative densities and lengths of the objects colliding. This tells us that the probe must give up all of its momentum before exiting Jupiter (and likely before it reaches the "surface" of Jupiter). The energy would spread conically in Jupiter until either a) Jupiter has most (if not all) of itself blown up. Imagine a large jet of superheated gasses being ejected from the other end of Jupiter. I do not understand the effects of high energy impacts on planetary geology well enough to determine how much of the planet will absorb energy, but I imagine it would be most of it. b) Jupiter absorbs all of the energy and heats up greatly (and falls into the Sun of course).


I'm not convinced that Newton's approximation remains valid for arbitrarily high initial momentum, but I am lazy, so I'm not going to bother trying to figure out a more detailed model to run numbers for...


I don't blame you for thinking that. His equations assumed a solid object impacting another solid object. It works for most substances when traveling a supersonic speeds. However, most objects stop reacting like rigid sheets when subjected to hyper-velocity impacts. This impact would be even worse, as the closest thing I can think of that approximates this type of impact is fundamental particle collisions. You know, like the ones in the LHC. Those collisions happen with matter that is traveling a lot slower, and that is far less dense. The modeling systems involved here ask questions like "what is the average distance in between collisions". In the near vacuum of the LHC, that is a high number. In the planet Jupiter, it is very low. So basically there would be a series of high energy collisions between an innumerable number of particles (and collisions between the particles that were created from that, and so on). I don't know how many particles are in the New Horizons probe, but taking the dry mass of the probe and dividing it by the mass of Aluminum, I found that we could expect an energy content per particle of 3.653×10^9 joules (about 1.9 times the Planck energy). I imagine that something stringy would happen (Randall's words), but personally I'm not sure. From what little I know about this, the closest analogue I can think of is an explosion. In essence, the probe hits the planet, and then the planet explodes. I also imagine that when this happens, the aliens (having shown their dominance) would begin playing something by Wagner over all our radio broadcasts.
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Re: What-If 0146: "Stop Jupiter"

Postby Kyorinrin » Thu Feb 18, 2016 8:18 pm UTC

Aha, that's what it was from, i remember reading that book a long time ago and this question tickled my brain in to remembering that part.

Although it seems like it would be more useful to use the torch to maintain altitude and launch a jet of ionized gas in an "almost" perfect escape velocity to make a gas halo that you could put orbital factories in. or maybye kust enough of a push to reach europas orbit.

Or on the other hand, could you use the torches like brushes to pump energy into jupiters magnetic field in an attempt to increase its spin.
(so torch statellites in the atmosphere pump energy into the field, while much higher orbiting units tap jupiters field for microwave transmission, i wonder what the efficiency would be.....)

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Re: What-If 0146: "Stop Jupiter"

Postby rmsgrey » Thu Feb 18, 2016 8:28 pm UTC

nowhereman wrote:
Pfhorrest wrote:
nowhereman wrote:The energy released however would not be enough to destroy the solar system. However, I cannot imagine that having bits of Jupiter rain on us would be good for the environment.

Would the mass of Jupiter not just scatter out in a huge ring out at Jupiter's orbital distance? (And if so, would it not eventually coalesce back into a Jupiter again, and if so, how does that reconcile with having overcome the gravitational binding energy of that mass if it eventually falls back together again under gravity?)


The gravitational binding energy is the amount of energy required to take every single bit of a uniform spherical object (a decent approximation for a planet) and remove it to infinity (every piece has a hyperbolic trajectory). In other words, you blow up a planet with this much energy and it will never come back. Even if there weren't planets, and other astronomical bodies to prevent the gasses from reforming as Jupiter, Jupiter would never reform again. As for what would happen to the rest of Jupiter, I am not certain. While this is enough energy to destory Jupiter for certain, it might not be enough to leave the solar system. Given that the escape velocity from Jupiter is 55m/s, and the Solar escape velocity at that distance is 18m/s it might create a shell of heated gases surrounding our solar system (like what you would see with a supernova... but smaller). Some quantity of that would collide with the Earth and do who knows what to our environment. I seriously don't know the answer to that. We would heat up slightly from the gasses and the composition of our atmosphere might be affected slightly. I doubt it would be a large effect though. We are really far away from Jupiter.


I think the point Pfhorrest was making is that the gravitational binding energy is just the energy that would be required to scatter the planet if it were isolated - for a small enough body in close enough orbit around a larger body, the gravitational binding energy is much less than the object's orbital binding energy, and giving it enough energy to disintegrate if it were in deep space will still disintegrate it, but all the pieces will still be in almost the same orbit as before, and will tend to accrete back into a similar body...

With Jupiter being large and distant from the Sun, disintegrating it will scatter the pieces rather than leaving them in a shared orbit.

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Re: What-If 0146: "Stop Jupiter"

Postby nowhereman » Thu Feb 18, 2016 9:48 pm UTC

rmsgrey wrote:
I think the point Pfhorrest was making is that the gravitational binding energy is just the energy that would be required to scatter the planet if it were isolated - for a small enough body in close enough orbit around a larger body, the gravitational binding energy is much less than the object's orbital binding energy, and giving it enough energy to disintegrate if it were in deep space will still disintegrate it, but all the pieces will still be in almost the same orbit as before, and will tend to accrete back into a similar body...

With Jupiter being large and distant from the Sun, disintegrating it will scatter the pieces rather than leaving them in a shared orbit.


When the collision occurs, the exploding Jupiter would have no angular momentum (on average). This means that the gasses would spread spherically and not in an orbit. You could imagine this as a big balloon of gas spreading and being vacuumed up by the Sun and the surrounding planets. There would also be a thin gas cloud throughout the entire system (until solar wind blows it out of our system). It would not recollect.
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Re: What-If 0146: "Stop Jupiter"

Postby Pfhorrest » Thu Feb 18, 2016 10:21 pm UTC

Ok so does this same principle apply to all other objects? If you were to blow up Titan (pump enough more energy than its gravitational binding energy into it), would Titan-dust scatter far and wide (getting sucked in by other nearby massive objects of course), or would Saturn just get another ring?
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