New efforts!

[pinballdave]

Basic conservation of energy would require the mechanical energy of any explosion to be equal to the detonation energy of the explosion, but part of the problem here is that separate from the energy transfer involved is the momentum delta produced which is a different thing.  And its non-trivial to translate nuclear blast effects into a vacuum because so much of them involve actual atmospheric effects.  In fact, detonating a nuclear bomb in a near vacuum above the surface of the moon would likely generate far more momentum from the reaction of vaporizing rock ejecting from the surface than the actual initial detonation wave of the explosion. (1). Would that work better if the bomb was buried?  Well, on the one hand more of the radiation energy would be intercepted by the moon but on the other hand with nowhere to go that energy would go into heating the moon and not moving it or any of its parts.  Optimal placement might actually be inside a small crater.

These are two non-sequitor statements. (2)  Yes, if you accelerate an object from lunar orbit in such a way that its net velocity relative to Earth increases, then you either get an increasingly elliptical orbit around the Earth, or eventually you escape Earth orbit and enter orbit around the Sun.  The Sun's escape velocity at about the distance the Earth-moon system orbits the Sun is a lot higher than Earth's escape velocity at about the Moon's relative orbital distance, so the object then begins to orbit the Sun.  But you said "dropped."  If you accelerate an object from lunar orbit in such a way that its net velocity relative to the Earth drops, then it enters into a different elliptical orbit where the mean distance to the Earth drops, and for high enough delta-v that object's "orbit" intersects the surface of the Earth.  Which is another way of saying it crashes into the Earth.

You can't easily (3) *drop* net velocity of a lunar rock and have it end up orbiting the Sun independently of the Earth-moon system.  Orbital mechanics don't work that way.  Anything near Earth with less than Earth's escape velocity ends up in an elliptical orbit around Earth, to a first degree approximation.  Incidentally, there's another option you haven't mentioned.  You could end up in orbit around the moon.  You could end up in orbit around the Earth.(3)  You could escape the Earth moon system and end up in orbit around the Sun.  You could escape the Solar system entirely.  But you could also find yourself in a resonance orbit locked within the Earth-Moon-Sun system.  Essentially, you could end up in a Lagrange point.  These are "orbits" but not classical Keplerian orbits: they are a consequence of the complex interaction between more than two-body gravity.

There are meteorites discovered on Earth determined to be of lunar origin.  They land here when they are ejected from the surface of the moon due to asteroid and meteoroid impacts.  When stuff gets blasted off the surface of the moon, the likelihood that some of it will eventually hit the Earth is actually not bad, given that such objects are either gravitationally coupled to the Earth-moon system or end up in Solar orbits that generally intersect Earth's orbit.  In 20 million years, say, they have about 20 million chances to hit us.  Most don't, a few do.

Keep in mind, we have discovered meteorites on Earth of confirmed Martian origin: rocks which were blasted off the surface of Mars through asteroid impact that eventually found their way to Earth.  That's not easy, but there have been millions of chances for it to happen across a billion years (Earth's been around longer than that, but go too far back into the past and it becomes likely that the rock isn't near the surface of the Earth to be discoverable anymore).

Also, we have a few astronauts still alive which owe their current terrestrial residence to the fact you can just throw an object off the moon and directly to Earth.

1. I was attempting to convey a method of shearing off a big piece of the moon to place in a decaying earth orbit. The idea of flooding the earth with moon objects possibly even microscopic to burn up in the atmosphere is an intriguing idea.

2. These contrasting statements were to convey the opposites of escaping the moon-earth binary to a higher, closer (marginally) towards Mars or nearer the sun (marginally) closer to Venus.

3. With enough deceleration the moon bits possibly would orbit the sun closer to Venus. We do this with probes to the inner planets, accelerating from earth, but decelerating from the earth's orbital path.

4. My point about rocketing to the earth was intended to convey that you can't point the rocket at the earth, you have to aim where it's going to be.

[Azrael]

Well, while we're 'shooting for the moon...'

https://en.wikipedia.org/wiki/List_of_highest_funded_crowdfunding_projects

I can't help but wonder why CoH isn't on that list.  It's better than a good many of those titles.

Ask NC Soft to name their price to give the game back to the community and open source it. 

I'd happily chip into a crowd fund like that to 'give the game back.'

Azrael.

[Arcana]

3. With enough deceleration the moon bits possibly would orbit the sun closer to Venus. We do this with probes to the inner planets, accelerating from earth, but decelerating from the earth's orbital path.

You can't do that from the orbit of the moon.  The moon itself is orbiting the Earth at a particular velocity that is roughly the same for a roughly circular orbit.  If you decrease that velocity relative to the frame of reference frame of the Earth, you will alter the orbit of that chunk of the moon so that it becomes a new orbit around the Earth that is elliptical with maximum altitude (aphelion) lunar orbit and minimum altitude (perihelion) some lower number.  When that lower number reaches the radius of the Earth, it crashes to the Earth.  You cannot, in one step, "drop" to the Sun.

Technically speaking, you can't do that from the Earth's surface either.  Try "decelerating" while on the surface of the Earth.  You just fall down.  You have to *increase* your velocity relative to the Earth enough to escape Earth's gravity well.  If that *simultaneously* drops your velocity relative to the Sun, you will then drop into an orbit around the Sun with aphelion Earth's orbit and perihelion some lower number.  But that can only happen by *increasing* your velocity relative to the frame of reference of the Earth.

[rezulin]

I was thinking of a continuous thrust mechanism for dislodging large orbital bodies.  Set up a large array of mirrors, maybe a thousand square miles or so in the L4 or L5 points.  Then aim the reflected light of the sun from the mirrors onto the surface of the orbital body you are trying to move.  The massive and continuous heat would (should, and if it doesn't, use more mirrors) cause the surface of your target to rise into the millions of degrees range.  This in turn, should cause a thruster like effect on the surface in one direction relative to its original orbit.  In several thousand years you should see an effect in its orbit.  Please note, do not use on inhabited worlds, as the average temperature of said world will rise to uninhabitable levels rather quickly. 

Personally I think Mars and Venus should be pushed into an orbit about 1 AU and be forced to merge into one planet, preferably on the opposite side of the Sun from Earth, as the collision will likely be messy.  This would give both planets a benefit.  Mars needs an atmosphere, Venus has too much of one.  They both need a new molten iron core which the merging should help with.  The new planet (I think should be named Genesis) will take a few million years or so to settle, and then we will have the great fun of terraforming it. 

Can't wait to get started!

Fuegocito

[LaughingAlex]

If only physics was one of my strong points.  Though if the moon was reduced to a ring, then they wouldn't reform into the moon.  They'd crash into earth and we'd, besides losing way to much crap on this planet from just the loss of the moon, end up with uninhabitable sections of planet for millions of years.  You also have to account for atmospheric changes from the lack of ocean tides, which would drastically change the overall nature of what it'd take for an impact.  It could be worst, better(for the planet, humans would be fubar by this point), but truthfully no one can really say, wholly, how much of a change the loss of the moon would be.

But heres something people never think of often; what if we were to ADD another super sized object to our orbit?  Even say, 10% of the size of the moon I'd wager would likely be enough to "nudge" the planet out of the usual solar orbit.

[Zombie Hustler]

From Wikipedia:
"Abian gained a degree of international notoriety for his claim that blowing up the Moon would solve virtually every problem of human existence. He made this claim in 1991 in a campus newspaper.  Stating that a Moonless Earth wouldn't wobble, eliminating both the seasons and its associated events like heat waves, snowstorms and hurricanes. Refutations were given toward that idea by NASA saying that part of the exploded Moon would come back as a meteorite impacting the Earth and causing sufficient damage to extinguish all life, while restoring the seasons in the process."

So... was that ever disproven?  ;)

[darkgob]

So... was that ever disproven?  ;)

I know you're joking, but the onus of proof is on the person making the claim.

[Arcana]

I was thinking of a continuous thrust mechanism for dislodging large orbital bodies.  Set up a large array of mirrors, maybe a thousand square miles or so in the L4 or L5 points.  Then aim the reflected light of the sun from the mirrors onto the surface of the orbital body you are trying to move.  The massive and continuous heat would (should, and if it doesn't, use more mirrors) cause the surface of your target to rise into the millions of degrees range.  This in turn, should cause a thruster like effect on the surface in one direction relative to its original orbit.  In several thousand years you should see an effect in its orbit.  Please note, do not use on inhabited worlds, as the average temperature of said world will rise to uninhabitable levels rather quickly. 

Actually, there's a principle of physics that basically limits the maximum temperature of a system like this.  Essentially, the maximum temperature you can induce into a surface with this kind of set up is basically the same as the temperature of the surface of the Sun (more technically, the temperature of a black body that emitted the net spectrum the Sun emits).  Basically, about 6000 degrees.  Still hot enough to vaporize the surface, but you can't heat the surface to millions of degrees no matter how many mirrors and/or focusing elements you use.

Think about it this way: you can only heat something with radiation if you sent it more radiation than it emits naturally.  When the surface reaches 6000 degrees it will be emitting radiation of the same temperature as the radiation you're sending to it.  And the radiation you're sending to it won't heat it any further, because those photons will be "cooler" than the matter they are striking.  They'd actually *gain* energy from that matter and reflect away with even more energy.


Separately, there's something called the "rocket equation."  The rocket equation basically takes the law of conservation of momentum and says that, in effect, the total momentum that all your rocket exhaust generates must equal the momentum of the spacecraft going the opposite direction.  It expresses this with what's known as an impulse equation: dV = Ve ln(M/m) where dV is the delta-V of the rocket (how much faster it ends up moving after all the propellant is used up), Ve is the speed of the exhaust, M is the total weight of the rocket and m is the rocket mass minus the propellant (so basically M-m is the mass of the fuel).  So the rocket starts off weighing M, burns up all its fuel and ends up weighing m, all the fuel goes that-a-way and the rocket goes this-a-way.  We can rewrite the rocket equation as (dV/Ve) = ln (M/m).  So the ratio of how fast you want to go and how fast your exhaust is, is equal to the natural logarithm of the ratio of the full rocket to the empty rocket.

Just making up numbers, suppose you want to change the velocity of the moon by half, from about 1 km/sec to 0.5 km/sec.  And suppose that the stuff blasting off the surface with your space mirror thingy is moving at about 700 miles per hour, or about 0.3 km/sec.  That means 0.5/0.3 = ln (M/m).  M/m becomes about 5.3.  That means m/M is about 0.19, or about 20%.  So you'd have to vaporize about 80% of the moon to do that.  I don't know what the real exhaust velocity would be (for something like the space shuttle boosters it was about 2.5 km/sec) and it would not be exhausting efficiently (without a rocket nozzle the stuff would be flying in all directions, not just in the opposite direction) but I suspect actually trying to significantly alter the orbit of the moon would require destroying a high percentage of it in some fashion.

How long it would take to actually vaporize a substantial percentage of the moon as rocket exhaust with a bunch of mirrors is a separate question.  Even if you could basically vaporize a one mile wide spot on the moon constantly, ripping a meter per second into vaporized ejecta, it would take about 160,000 years to vaporize about half the moon.

[Arcana]

But heres something people never think of often; what if we were to ADD another super sized object to our orbit?  Even say, 10% of the size of the moon I'd wager would likely be enough to "nudge" the planet out of the usual solar orbit.

To a first order approximation, as far as the Sun is concerned there's an object called "Earth-moon" that orbits it.  The interactions between the Earth and the moon affect Earth's orbit around the Sun basically not at all, at least on time scales of millions of years.  Adding another object in orbit about 10% the size of the moon wouldn't do much of anything to the Earth or its Solar orbit.

More important would be the chaotic interactions between the Earth, the moon, and the third object.  Its likely that after enough time the third object would either find itself in a resonance point (a Lagrange point, basically) or ejected out of the Earth-moon system.

Think about it this way.  In effect, the Earth, the moon, and the Sun are all bound to obey some pretty stringent conservation laws.  In this case, conservation of angular momentum is the most important.  Picture the Earth and the Moon orbiting their mutual center of gravity (which is close enough to Earth's center that its basically inside the Earth, but noteworthy is that its several thousand miles from Earth's center).  That mutual center of gravity, like a point on an asymmetrical dumbbell spinning in space is itself orbiting the Sun (actually, its also orbiting the center of the Sun-Earth system, but that's so close to the center of the Sun its practically orbiting the Sun's center).  The Sun, the Earth, the Moon, all have angular momentum.  The net of the entire system has to remain constant.  So when you throw a new body in there like a new moon, it can't just cause the Earth to go willy-nilly flying off into space.  The Earth would have radically different angular momentum, and that has to come from somewhere.  It can't come from the new moon, because its too small to have been packing all that momentum.  When the system starts wobbling, its not likely that somehow the new moon settles down and the Earth catapults away.  There's no way for the momentum to come out right.  Instead, its more likely that when the Earth and the new moon exchange momentum the Earth's will change a little and the new moon will change by a lot (because the Earth is far more massive) and the new moon will get thrown out of the system like an old refrigerator you forgot to tie down in the truck bed.

If you've ever heard of gravity assist, basically that's when a spacecraft exploits orbital mechanics to slingshot past a planet, like Jupiter.  The net result is that the spacecraft picks up a megaton of angular momentum.  The planet loses some.  But because the planet is so much more massive than the spacecraft, the spacecraft can pick up hundreds or even thousands of miles per hour in linear speed while the planet ends up slowing down by a couple of millimeters per century.  Usually, the big guys throw the small guys around, not vice versa, because of conservation of momentum and angular momentum.

[Todogut]

... what if we were to ADD another super sized object to our orbit?

Reminded me of Larry Niven's Ringworld, which described a habitable technological structure built in the shape of a ring around a star.

https://upload.wikimedia.org/wikipedia/en/7/71/Ringworld%281stEd%29.jpg

[pinballdave]

Actually, there's a principle of physics that basically limits the maximum temperature of a system like this.  Essentially, the maximum temperature you can induce into a surface with this kind of set up is basically the same as the temperature of the surface of the Sun (more technically, the temperature of a black body that emitted the net spectrum the Sun emits).  Basically, about 6000 degrees.  Still hot enough to vaporize the surface, but you can't heat the surface to millions of degrees no matter how many mirrors and/or focusing elements you use.

Think about it this way: you can only heat something with radiation if you sent it more radiation than it emits naturally.  When the surface reaches 6000 degrees it will be emitting radiation of the same temperature as the radiation you're sending to it.  And the radiation you're sending to it won't heat it any further, because those photons will be "cooler" than the matter they are striking.  They'd actually *gain* energy from that matter and reflect away with even more energy.


Separately, there's something called the "rocket equation."  The rocket equation basically takes the law of conservation of momentum and says that, in effect, the total momentum that all your rocket exhaust generates must equal the momentum of the spacecraft going the opposite direction.  It expresses this with what's known as an impulse equation: dV = Ve ln(M/m) where dV is the delta-V of the rocket (how much faster it ends up moving after all the propellant is used up), Ve is the speed of the exhaust, M is the total weight of the rocket and m is the rocket mass minus the propellant (so basically M-m is the mass of the fuel).  So the rocket starts off weighing M, burns up all its fuel and ends up weighing m, all the fuel goes that-a-way and the rocket goes this-a-way.  We can rewrite the rocket equation as (dV/Ve) = ln (M/m).  So the ratio of how fast you want to go and how fast your exhaust is, is equal to the natural logarithm of the ratio of the full rocket to the empty rocket.

Just making up numbers, suppose you want to change the velocity of the moon by half, from about 1 km/sec to 0.5 km/sec.  And suppose that the stuff blasting off the surface with your space mirror thingy is moving at about 700 miles per hour, or about 0.3 km/sec.  That means 0.5/0.3 = ln (M/m).  M/m becomes about 5.3.  That means m/M is about 0.19, or about 20%.  So you'd have to vaporize about 80% of the moon to do that.  I don't know what the real exhaust velocity would be (for something like the space shuttle boosters it was about 2.5 km/sec) and it would not be exhausting efficiently (without a rocket nozzle the stuff would be flying in all directions, not just in the opposite direction) but I suspect actually trying to significantly alter the orbit of the moon would require destroying a high percentage of it in some fashion.

How long it would take to actually vaporize a substantial percentage of the moon as rocket exhaust with a bunch of mirrors is a separate question.  Even if you could basically vaporize a one mile wide spot on the moon constantly, ripping a meter per second into vaporized ejecta, it would take about 160,000 years to vaporize about half the moon.

semi-spoiler... Did Disney consult you about the big weapon in the new Star Wars movie?

[Arcana]

semi-spoiler... Did Disney consult you about the big weapon in the new Star Wars movie?

No, I believe they consulted John Crichton.

[Thunder Glove]

Not at this time of year.  Brrrrr...

I went pantless this time of year and got a trophy for it.  It had "Look Ma, No Pants!" engraved on it.

[Biz]

No, I believe they consulted John Crichton.

I heard a rumor that Winona also had some input

[Azrael]

semi-spoiler... Did Disney consult you about the big weapon in the new Star Wars movie?

A pity they didn't consult George Lucas on their random, barren story telling desert with its empty, soulless, cynical re-enactment and yes, patronising miss-mash, creation by committee, 'Star Wars Ticklist' borefest.  *Lots of heavy breathing in teh 'fan' made movie with its 'explosions' and 'woo-ey' vertigo inducing shots.  Corporate arrogance at its 'finance', cough, I meant to say, 'finest.'

'Disney.'  Or should I say, 'disgusting.'

Azrael.

[CrimsonCapacitor]

And now, for my next trick, I'm going to merge the destruction of the moon with COH.

Nothin' up my sleeve.... 

PRESTO!

Moonbase....  Boy, do I wish we could've seen that.

[HorseManDemon]

I went pantless this time of year and got a trophy for it.  It had "Look Ma, No Pants!" engraved on it.

Huh... Something about that seems familiar. I simply loath that I cannot remember it. Augh! My kingdom for a hint... I swear it's right on the tip of my Wand of Nagamar ... Er... Tongue... I meant tongue.  ;)


P.S. Tongue is a very strange looking word.

[Azrael]

And now, for my next trick, I'm going to merge the destruction of the moon with COH.

Nothin' up my sleeve.... 

PRESTO!

Moonbase....  Boy, do I wish we could've seen that.

Just a shame we never got that 'Moon Base.'  Coh cut down a handful of issues too soon.

One day, who knows what will be possible.

Time is our friend.

Azrael.

[Vee]

A pity they didn't consult George Lucas on their random, barren story telling desert with its empty, soulless, cynical re-enactment and yes, patronising miss-mash, creation by committee, 'Star Wars Ticklist' borefest.  *Lots of heavy breathing in teh 'fan' made movie with its 'explosions' and 'woo-ey' vertigo inducing shots.  Corporate arrogance at its 'finance', cough, I meant to say, 'finest.'

'Disney.'  Or should I say, 'disgusting.'

Azrael.

https://images.weserv.nl/?url=oi66.tinypic.com%2F2dbp4co.jpg

[hurple]

A pity they didn't consult George Lucas on their random, barren story telling desert with its empty, soulless, cynical re-enactment and yes, patronising miss-mash, creation by committee, 'Star Wars Ticklist' borefest.  *Lots of heavy breathing in teh 'fan' made movie with its 'explosions' and 'woo-ey' vertigo inducing shots.  Corporate arrogance at its 'finance', cough, I meant to say, 'finest.'

'Disney.'  Or should I say, 'disgusting.'

Azrael.

Yeah, we could have gotten 2 1/2 hours of disgusting racist caricatures and people sitting around have boring and confusing political discussions, instead. 

Oh, with a break in the middle for some speeder race that has absolutely no fu**ing thing to do with any of the rest of the movie or story-arc whatsoever, just so there'd be some action scene in the movie.

Yep, much better.