Gravity Tractor discussion ...

[Urwumpe]

Are you sure you want dispersed plutonium floating in the upper atmosphere? Please check its LD50 to see what it can do.

RTGs are especially designed to never release plutonium to the outside before the energies are so huge that the plutonium would be evaporated into fine dust. You likely already accumulated the equivalent of 5 or 6 critical RTG launch accidents in your lungs, simply by the amount of plutonium that is a trace in the normal dust around you.

Minute traces of plutonium are usually found in the human body due to the 550 atmospheric and underwater nuclear tests that have been carried and a small number of major nuclear accidents. Most atmospheric and underwater nuclear testing was stopped by the Limited Test Ban Treaty in 1963, which was signed and ratified by the United States, the United Kingdom, the Soviet Union, and other nations. Continued atmospheric nuclear weapons testing since 1963 by non-treaty nations included those by China (atomic bomb test above the Gobi Desert in 1964, hydrogen bomb test in 1967, and follow-on tests), and France (tests as recently as the 1980s).
Because it is purposely manufactured for nuclear weapons and nuclear reactors, plutonium-239 is the most abundant isotope of plutonium by far.[30]
It is also hypothetically possible for minute quantities of plutonium to be produced by the natural bombardment of uranium ores with cosmic rays.

I am pretty sure, you can even calculate how much plutonium you can lose to launch accidents so that its level in nature will eventually drop to half of what it is today.

 

[Wishbone]

Small wonder cancer is being more frequent... If there's a way to avoid extra poisoning, I would choose it.

And re: disruption. Even if it succeeds, it simply MIRVs the asteroid unless you do it over and over and over again. The damage expectancy will increase, since the blast roughly scales as a cubic root of yield. (up to a point, as ablation in the atmosphere takes its toll). Just think what this rain of death can do to sprawled out cities and agglomerations of today.

 

[Urwumpe]

Small wonder cancer is being more frequent...

Fallacy. actually, more people die of cancer, because we know about it, and because today, people live long enough to die of cancer.

In the past, more people died of illnesses, that have easy cures today, or simply malnutrition.

Its kind of scary, if you read in which year the last cholera epidemic in Hamburg (not Haiti) had been one major reason for establishing a national health care in Germany...

 

[T.Neo]

If there's a way to avoid extra poisoning, I would choose it.

Could you clarify?

I don't see how one could choose the death of millions- or billions, over a slightly higher amount of plutonium or uranium in the atmosphere...

And re: disruption. Even if it succeeds, it simply MIRVs the asteroid unless you do it over and over and over again. The damage expectancy will increase, since the blast roughly scales as a cubic root of yield. (up to a point, as ablation in the atmosphere takes its toll). Just think what this rain of death can do to sprawled out cities and agglomerations of today.

Not really; if the fragments seperate far away enough (as I believe Zatniktelman was talking about much earlier in this thread) they will hit over a far wider area or miss the Earth entirely. If we're talking about something like Apophis, that we can potentially catch decades in advance, before passing through a so called "keyhole", then there is the potential for the fragments to miss Earth by a large margin.

And if you intercept the bolide at any sensible time, there's a good potential for the fragments to at least be split up over a large part of the planet. In the case of Apophis, that means that they (probably) hit an uninhabited area and do relatively little damage, but in the case of a larger object, it probably causes more destruction, in a slightly different manner.

Keep in mind though that I'm talking deflection, not disruption, using nukes.

Urwumpe, what about a crude mass driver using material from the asteroid? That way you can solve getting the propellant to a high velocity by drawing on the large mass of the object, and also have a more efficient deflection/disruption/mitigation strategy than trying to deconstruct the entire thing...

 

[SiberianTiger]

Maybe spinning such a body fast enough would be ok to make it fall apart? Attach a pair of huge counter-tilted mylar sails on opposite sides on the asteroid and let solar winds do the job...

 

[Urwumpe]

Urwumpe, what about a crude mass driver using material from the asteroid? That way you can solve getting the propellant to a high velocity by drawing on the large mass of the object, and also have a more efficient deflection/disruption/mitigation strategy than trying to deconstruct the entire thing...

Sure, if the asteroid does not rotate at all. I currently think along gathering material from the asteroid and collecting it in containers...which could then be mass driver fired at the right angle.

Of course, this is not realistic now, and not near future at all... but some sort of logical... building space craft that eat asteroids and send standard buckets with asteroid material do Earth.

 

[T.Neo]

Or anywhere else for that matter? I can't imagine Earth as the center for all space-based industry...

Then again, there is always a potential to import refined resources, but I doubt this would be anything terribly abundant.

 

[Urwumpe]

Or anywhere else for that matter? I can't imagine Earth as the center for all space-based industry...

Well, for nearly everything else, it has perfect qualifications to be the center...

Will likely take a long while until this changed. Of course, it is likely we will want to move the pollution of refining ore to some place where it does not matter... eg into orbit. The thermal control might be tough there for processing metal, but the quality would be extremely good and pollution by CO2 is a minor problem.

 

[Keatah]

I think the entire point is that you launch it really far in advance. The way it works is that the ship just maintains it's position on one side of the NEO. The NEO would use it's slight gravity to pull the ship, and the ship would use it's slight gravity to pull the NEO. However, the ship uses it's thrusters to stay a constant distance from the NEO. The total effect is to transfer the momentum from the thrusters to the NEO. As long as you launch it long enough in advance, I see no reason you couldn't change the trajectory enough to do something useful. The only reservation I have about the plan is what happens to the exhaust from the gravity tug's thrusters? It seems they'd have to be oriented at a large angle in order to miss the asteroid, while still staying close enough. This makes thing much more inefficent. The big question I'm unequipped to answer is whether it would be more mass efficent to waste propellent like this, or to include landing gear so the tug can push directly.

It would only be a matter of how long. If you direct connect the tug, then you could expend the fuel in a matter of minutes and get a change.

If you gravity-couple the tug, then you'd have spread out your thruster firings over months.

End result is really no different either way you play the game, except the shape of the final trajectory. The same amount of energy is being transferred to the asteroid.

 

[T.Neo]

Urwumpe, of course, but don't you think there is a little problem with having to go to asteroids for materials that make up large percentages of our own planetary crust? Or better still, recycling what and where we can?