OT?: Goodbye to an era

I did the conversions of kinetic energy to momentum as a function of a for-sake-of-argument mass of the grain of sand and a zero-elasticity collision.

I will repeat my latest for-sake-of-argument figures: Grain of sand has mass of .1 milligram. The 4-foot-diameter ball has mass of 2.5 metric tons.

When floating in a vacuum, if hit with a dead-center hit, the above big ball has velocity changed by close enough to 1/25,000,000,000 of the velocity of the grain of sand. (At least in terms of vector subtraction result's magnitude, where the vector subtraction is between the big ball's velocity before the collision and the big ball's velocity after the colision - regardless of direction that the big ball was shot from.) Between that much velocity change and twice that if the grain of sand bounces back. Add to this if a crater is created, due to expelling the mass of what was where the crater afterwards is (as in mass that was expelled. Net momentum of mass expelled from the big ball means a similar magnitude opposite direction momentum was added to the big ball, in addition to that which the bullet had, minus any [by vector subtraction] that the bullet ricochets with if it does). For that matter, rubber bullets actually kick harder than do clay ones of same mass and velocity and similar size and density. The rubber ones continue their "kick" by pushing off their targets for ricocheting, in addition to the impulse required to stop them.

I do agree that extremely little of the energy expended by using a high velocity particle or an energetic vaporizing explosive detonation becomes increase of kinetic energy of a massive target. However, I think the problem here is more one of changing the target's momentum than one of changing its kinetic energy. It appears to me that it gets down to energy-efficient (or more like cost-efficient) ways of hitting a massive target with an "impulse" - which is product of force and time, or more exactly integral of force(as_function_of_t)*dt over the period covering the t / time when the force is applied.

Can you cite when and how the silk was replaced?

Please keep in mind that I live within 1.5 hours and work about 1 hour away from an Iowa class battleship that currently invites the public into it as a museum.

Please don't merely cite how this practice started during or even a bit before WWII, or how Iowa class battleships were WWII products. I am asking you to cite how early such WWII practices were taken out of commission. I can cite their use in actual warfare as recently as 1991.

Furthermore, even if you can do so, these big guns of battleships did work as John Larkin said they do, including the silk bags of propellant as well as accelerating a projectile of mass greater than a metric ton by around a kilometer/second in milliseconds! (2,690 ft/sec or / 820 m/sec maximum for 1900-2700 pound / .85 to 1.2 metric ton pojectiles, depending on choice of projectile option and how many of what size of bags of propellant to feed into the gun behind the projectile.)

And after one year that movement would total what... 2 mm?

How much forewarning do you think we'll get, and then how long do you think it will take us to deliver payload for a rendezvous?

I do not think there will be much time at all. I think any movement applied will need to be a LOT just to effect even a .01 second change.

There are a lot of seconds in a circle.

We would have a hard time making it miss if the deflection needed was any great amount at all.

Does that not have significant "impulse", as defined by change in momentum? Especiallty if the explosion accomplishes a "blowback" that results in a crater?

Hilarious, and "sidereal" makes it even better.

Imagine attaching a rocket to a pile of gravel.

John

Of course it only takes changing the orbital path a slight bit from a far distance away.

I also said that SRBs would be the best. HUGE SRBs.

Long, sustained push for a net move that would be bigger than the flash in the pan variety.

I'd bet that a bottle rocket could move a target farther than a nearby firecracker or even M-80 detonation.

The nature of a rocket is a directed 'thrust'. The nature of a detonation is omnidirectional and a lot of juice is lost is the fireball itself. A lot less ends up pushing in any one direction against any nearby object.

Replaced?

They do not simply "replace the silk". They cycle new, fresh powder bags in and cycle the old out to go back to the factory.

They have expiry dates. I'll bet that there are none in service that are over ten years of age.

I never said it didn't.

I merely said that it would not be significant, nor would it be enough.

If it is large enough to have conglomerated gravitationally to begin with, then it is large enough to tug everything along, even if you segregate it a bit. If it is more solid than that... then... it is more solid than that, and you lose again.

That's a lot easier than attaching a brain to 'always wrong'.

If the 2.5 metric ton rock is at rest in vacuum (which I suspect you snipped out since I remember saying "in vacuum"), and gets shot dead-on-center, it will gain something like 99.99999-plus percent of the linear momentum of "bullet", more if the collision has above-zero elasticity or the impact causes a "cratering process" where the target's "cratering-prcess" expels debris whose net momentum is directed to a direction within 90 degrees of where the bullet came from.

I seem to think that your physics teacher would laugh at you more than the targeted rock would. It appears to me that a physics teacher would accept a correct or "ballpark-correct" small number with work shown and issue a zero on such a quiz or test question for stating zero.

It does not matter. With these quantities of material and energy. Suspended in air from a string would allow for the same measurement. The air doesn't start pushing back until high velocities are reached, and I don't think that hanging from a sting is moving very fast.

So, in a vacuum or not, you would still be able to make the determinations of force applied and the response of the ball will be the same as well. Shoot a bb at a marble on a string and in space or in air the movement would be the same until the velocities start getting up there.

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It doesn't sound hard until you get into the hard mechanics of actually doing it. Ask Alderson.

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Which is a bit of a pity, because it is politically a meganightmare for all those nationalists. (not to mention the terrorist implications). Quis custudiot ipso custudios.

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And it was working with an atmosphere to hold the bang in place.

At a minimum it would take re-engineering the bombs for maximum heat and improved blast. Much of current weapons are oriented around flash x-ray yield. Not terribly useful for propellant properties.

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A very damaging rock would be at least 1 cubic kilometer of rock, 2.5 billion tons. You want to vaporize 1%, 25 million tons in a vacuum. Try using about 150 Mt of bang. Bigger rocks will take correspondingly more.

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That may do the job if we can get to it a distance of 50 million kilometers away (about halfway to the orbit of Mars). If we cannot reach it until 5 million km (20 times the distance to the moon) away we need rather more delta V.

I bet Werner did. Certainly the designers of modern rockets (like since the shuttle) do. I'll bet they even do it for the friction heated air during takeoff, they have always had to do it for re-entry.