How to Make Use of an Asteroid on Earth

On 1/03/2010 3:49 AM, William Mook wrote:
On Feb 28, 1:15 am, Pat wrote:
On 2/27/2010 12:42 PM, Damon Hill wrote: A large disturbance can, and
has been observed,

to break up asteroids into multiple impactors. Ask the Jovians.

And all that took was a mild dive through Jupiter's gravity field.
Here's a whole other approach to deflecting a asteroid:http://www.mikebrotherton.com/diamonds/?page_id=134

Pat

Right! Applied pressure must accelerate less than surface gravity.
Exceed surface gravity and parts are left behind - definitely. It
will take care and planning, but it will be less difficult than say
herding sheep - that's why the ability to apply small spot sizes (or
small explosions for the micro-nukes) broadly and quickly across a
surface will be important. Absolutely.

I find it difficult to reconcile the need for small thrust with any kind
of nuke, particularly as there's a limit to how small a nuke can be.

However, making one's nuke tunnel into the middle of the 'roid, which
would presumably require little energy in a lightly compacted object,
and then detonating it, would seem likely to scatter the thing all over
the sky, with most of it missing the Earth entirely provided the action
is not left until the last moment.

Sylvia.

On Feb 28, 6:15*pm, Sylvia Else wrote:
On 1/03/2010 3:49 AM, William Mook wrote:



On Feb 28, 1:15 am, Pat *wrote:
On 2/27/2010 12:42 PM, Damon Hill wrote: A large disturbance can, and
has been observed,

to break up asteroids into multiple impactors. *Ask the Jovians.

And all that took was a mild dive through Jupiter's gravity field.
Here's a whole other approach to deflecting a asteroid:http://www.mikebrotherton.com/diamonds/?page_id=134

Pat

Right! * Applied pressure must accelerate less than surface gravity.
Exceed surface gravity and parts are left behind - definitely. *It
will take care and planning, but it will be less difficult than say
herding sheep - that's why the ability to apply small spot sizes (or
small explosions for the micro-nukes) broadly and quickly across a
surface will be important. *Absolutely.

I find it difficult to reconcile the need for small thrust with any kind
of nuke, particularly as there's a limit to how small a nuke can be.

The pulse is largely UV light in vacuum, and it is spread over a large
area. So, a pulse spread over a large illuminated surface ejects
material quickly, but evenly - and if done at the right rate, provides
a series of pulses that produce a controlled thrust.

For example, take a sphere 50 km in diameter massing 1e+17 tons with a
surface gravity of 0.0025 m/sec^2 and a density of 1.2e3 kg/m3. Let's
say we want to accelerate this evenly at 0.0010 m/sec^2. This is less
than half the surface gravity.

Imagine a nuclear pulse that deposits UV light across one side of this
sphere so that it ejects material to some depth at 50 km/sec.

F = ma = mdot * Ve

a = 0.001 m/sec/sec
m = 1e+17 kg
F = 1e+14 N
Ve = 5e+4 m/sec

so...

mdot = 1e+14/5e+4 = 2e+9 kg/sec

Since the hemisphere contains 5.9e+10 kg/cm of depth, then a gamma
flash would need to blow away material across that surface at a rate
of 33.8 microns per second.


and

E = 1/2 m * Ve^2 -- W = 1/2 * mdot * Ve^2 -- W = 1/2 * F * Ve

So, 2e+9 kg/sec at 50,000 m/sec implies a power of 2.5e+18 Watts.
Fusion produces 6.45e+14 Joules/kg - so this requires the detonation
of 3.5 metric tons of lithium deuteride per second - to maintain this
low rate of acceleration.

With 100 blasts per second - each blast a few millionths of a second -
produce very sharp gamma bursts, but these are thermalized when
absorbed by the surface of the planetoid and it takes a milli-second
to clear away before the next pulse. 10,000 microseconds between
pulses the system settles down due to gravity, and another pulse
arrives.

Each bomblet is only 70 kg of materials twenty liters in size
positioned in such a way as to produce a controlled directed blast of
ejecta from the body which is thoroughly mapped and probed before
engineered pulses are applied to it.

However, making one's nuke tunnel into the middle of the 'roid, which
would presumably require little energy in a lightly compacted object,
and then detonating it, would seem likely to scatter the thing all over
the sky,

Which is why you don't do it.

Its best to think of the thing as liquid, and transporting it in a way
as not to produce waves.

with most of it missing the Earth entirely provided the action
is not left until the last moment.

Um.. I'm talking about GATHERING ASTEROIDS INTO USEFUL ORBITS FOR
PROCESSING INTO USEFUL PRODUCTS FOR HUMAN INDUSTRY.

So, you're missing the point Sylvia.

We close our mines and refineries, processing plants and factories on
Earth and move them all to orbit - using teleoperated robots.

http://en.wikipedia.org/wiki/Asimo


Sylvia.

On 1/03/2010 12:22 PM, William Mook wrote:

For example, take a sphere 50 km in diameter massing 1e+17 tons with a
surface gravity of 0.0025 m/sec^2 and a density of 1.2e3 kg/m3. Let's
say we want to accelerate this evenly at 0.0010 m/sec^2. This is less
than half the surface gravity.

Imagine a nuclear pulse that deposits UV light across one side of this
sphere so that it ejects material to some depth at 50 km/sec.

F = ma = mdot * Ve

a = 0.001 m/sec/sec
m = 1e+17 kg
F = 1e+14 N
Ve = 5e+4 m/sec

so...

mdot = 1e+14/5e+4 = 2e+9 kg/sec

Since the hemisphere contains 5.9e+10 kg/cm of depth, then a gamma
flash would need to blow away material across that surface at a rate
of 33.8 microns per second.


and

E = 1/2 m * Ve^2 -- W = 1/2 * mdot * Ve^2 -- W = 1/2 * F * Ve

So, 2e+9 kg/sec at 50,000 m/sec implies a power of 2.5e+18 Watts.
Fusion produces 6.45e+14 Joules/kg - so this requires the detonation
of 3.5 metric tons of lithium deuteride per second - to maintain this
low rate of acceleration.

With 100 blasts per second - each blast a few millionths of a second -
produce very sharp gamma bursts, but these are thermalized when
absorbed by the surface of the planetoid and it takes a milli-second
to clear away before the next pulse. 10,000 microseconds between
pulses the system settles down due to gravity, and another pulse
arrives.

Each bomblet is only 70 kg of materials twenty liters in size
positioned in such a way as to produce a controlled directed blast of
ejecta from the body which is thoroughly mapped and probed before
engineered pulses are applied to it.

However, making one's nuke tunnel into the middle of the 'roid, which
would presumably require little energy in a lightly compacted object,
and then detonating it, would seem likely to scatter the thing all over
the sky,

Which is why you don't do it.

Its best to think of the thing as liquid, and transporting it in a way
as not to produce waves.

with most of it missing the Earth entirely provided the action
is not left until the last moment.

Um.. I'm talking about GATHERING ASTEROIDS INTO USEFUL ORBITS FOR
PROCESSING INTO USEFUL PRODUCTS FOR HUMAN INDUSTRY.

An object such as you described would have a Roche limit of about 20,000
km, so not so readily accessible.

But a more serious objection is that it's one thing to take an asteroid
that crosses Earths orbit, and move it so that it does so about when the
Earth is there. It's quite another to get it into orbit round the Earth,
which is going to require a significant change in velocity. And if your
preferred asteroid doesn't come anywhere near Earth's orbit anyway...

Sylvia.

On Mar 1, 12:42*am, Sylvia Else wrote:
On 1/03/2010 12:22 PM, William Mook wrote:



For example, take a sphere 50 km in diameter massing 1e+17 tons with a
surface gravity of 0.0025 m/sec^2 and a density of 1.2e3 kg/m3. *Let's
say we want to accelerate this evenly at 0.0010 m/sec^2. *This is less
than half the surface gravity.

Imagine a nuclear pulse that deposits UV light across one side of this
sphere so that it ejects material to some depth at 50 km/sec.

F = ma = mdot * Ve

a = 0.001 m/sec/sec
m = 1e+17 kg
F = 1e+14 N
Ve = 5e+4 m/sec

so...

mdot = 1e+14/5e+4 = 2e+9 kg/sec

Since the hemisphere contains 5.9e+10 kg/cm of depth, then a gamma
flash would need to blow away material across that surface at a rate
of 33.8 microns per second.

and

E = 1/2 m * Ve^2 -- * W = 1/2 * mdot * Ve^2 *-- *W = 1/2 * F * Ve

So, 2e+9 kg/sec at 50,000 m/sec implies a power of 2.5e+18 Watts.
Fusion produces 6.45e+14 Joules/kg - so this requires the detonation
of 3.5 metric tons of lithium deuteride per second - to maintain this
low rate of acceleration.

With 100 blasts per second - each blast a few millionths of a second -
produce very sharp gamma bursts, but these are thermalized when
absorbed by the surface of the planetoid and it takes a milli-second
to clear away before the next pulse. *10,000 microseconds between
pulses the system settles down due to gravity, and another pulse
arrives.

Each bomblet is only 70 kg of materials twenty liters in size
positioned in such a way as to produce a controlled directed blast of
ejecta from the body which is thoroughly mapped and probed before
engineered pulses are applied to it.

However, making one's nuke tunnel into the middle of the 'roid, which
would presumably require little energy in a lightly compacted object,
and then detonating it, would seem likely to scatter the thing all over
the sky,

Which is why you don't do it.

Its best to think of the thing as liquid, and transporting it in a way
as not to produce waves.

with most of it missing the Earth entirely provided the action
is not left until the last moment.

Um.. I'm talking about GATHERING ASTEROIDS INTO USEFUL ORBITS FOR
PROCESSING INTO USEFUL PRODUCTS FOR HUMAN INDUSTRY.

An object such as you described would have a Roche limit of about 20,000
km, so not so readily accessible.

But a more serious objection is that it's one thing to take an asteroid
that crosses Earths orbit, and move it so that it does so about when the
Earth is there. It's quite another to get it into orbit round the Earth,
which is going to require a significant change in velocity. And if your
preferred asteroid doesn't come anywhere near Earth's orbit anyway...

Sylvia.

I think I mentioned that the total delta vee is 6.5 km/sec - with most
of that at Earth.

Let's do an example calculation. Let's take an object from Ceres to
Earth orbit.

The equation to use is the vis viva equation;

v = sqrt( mu * (2/r - 1/a))

Ceres orbit is

a=2.7663 AU (413.8 Gm)
V = 17.882 km/sec

Earth orbit is

a=1.0000 AU (149.6 Gm)
V = 29.783 km/sec

The transfer orbit is

a=1.8832 US (281.7 Gm)

And velocity at aphelion is;

V(2.7663 AU) = 13.049 km/sec

which is 4.833 km/sec decrease in speed.

Given the surface gravity of Ceres is 0.27 m/sec2 it would take at
least 5 hours to impart that speed to Ceres in a way that would not
tear it apart.

The velocity at perihelion is;

V(1.0000 AU) = 36.098 km/sec

which is 6.315 km/sec decrease in speed again.

Given the surface gravity of Ceres is 0.27 m/sec2 it would take at
least 8 hours to impart that speed to Ceres in a way that would not
tear it apart.

Total delta vee is 11.148 km/sec. With an exhaust speed of 50.000 km/
sec we can calculate how much of Ceres must be vaporized to carry out
this transfer. 19.99% of the total mass of Ceres.

The jet energy contained in the plume is 1.25 trillion joules per
metric ton of propellant - with only 1/3 of the energy showing up in
the plume this means that 3.75 trillion joules are expended in a
fusion pulse unit per metric ton. So, each metric ton of ejecta
requires 2 grams of lithium 6 deuteride or Boron 10 or other
aneutronic fusion fuel.

So a total of 3.77e+17 kg of fusion fuel is needed to be applied to
energize 1.89e+20 kg of Ceres surface in a way to impart this delta
vee

There are 4.35e+9 kg of Boron produced each year.
There are 1.70e+7 kg of Lithium produced each year.

So, it would take a massive millionfold increase in the production
rates of these materials to use them in the way described here.

Not much deuterium is produced each year, but there's plenty of it in
the oceans, so this might be an interesting source.

The production rates of fusion materials on Earth today limits the
rates to about 1 millionth the mass of Ceres. This is something
that's 1/100th the diameter of Ceres - EACH YEAR. So, something about
5 km in diameter - each year - is the limit of what we can expect.
Even so, the mass of materials is stupendous - sufficient to provide
for everyone's material needs.

Once you've got Ceres or another low density object on orbit, Silvia
is correct, the Roche radius determines how close you can bring it
before it breaks up into a ring;

The Roche Radius for Ceres is

d = R * (2* rho(M)/rho(m))^(1/3) = 11,115 km

Where;

R = 6.371 Mm
rho(M) = 5.515 g/cc
rho(m) = 2.077 g/cc

SO, if you navigate the planetoid into a tight orbit say 1,000 km
above Earth, it will rip apart due to gravitational forces.

But, is breaking up a planetoid that you want to process into useful
stuff a bad thing?

To me it seems like a good way to use tidal forces to process
asteroids for you.

Why not get relatively dense objects and use them as shepherd moons to
keep pieces from being a threat to navigation and safety and then
bring stuff into the space between the shepherd moons and let tidal
forces tear them apart for you?

Then send free-flying solar powered industrial satellites to process
the pieces that are found there?

This is the way I'd do it.

A theta-pinch method to compress fissile materials like weapons grade
plutonium or highly enriched uranium can get densities 10 to 100 times
resting density. This is 3 to 30 times the densities achieved by
using shaped plastic explosives.

10 kg of Plutonium in a sphere 10 cm in diameter forms a critical mass
at resting density. 15 kg of Uranium-233 in a sphere 11 cm in
diameter ditto. Uranium 235 requires 52 kg of material in a sphere 17
cm in diameter for explosion.

Compressing to 3x resting density reduces masses to 10% - 1 kg Pu, 1.5
kg U-233, 5.2 kg of U-235.

Compressing to 100x resting density reduces masses to 0.01% - 1 gram
of Pu, 1.5 grams of U-233, 5.2 grams of U-235.

Using anti-matter to catalyze fissile reactions increases neutron
yield from 2 to 9 neutrons per fission which reduces things by another
factor of 10 - 100 mg to 520 mg of fissile material.

There are 2000 metric tons of weapons grade materials in the world.
With theta-pinch techniques, it is possible to create millions of
'triggers' for propulsive fusion units.

Fusion units consist of lithium-deuteride, or boron-10 triggered by
fission 'sparks'

The shape of the fusion fuel once detonated, determines the shape of
the resulting blast.

A long cylinder produces an explosion that spreads out from the center
of the cylinder like a sheet.

A plate produces an explosion that spreads out from the surface of the
plate forming a blast focused along a line passing perpendicular to
the center of the sheet.

Changing the shape of things makes things more interesting.

A kg of fusion material detonated by a few milligrams of fissile
triggering material form the basis of a propulsive unit.

A disc of boron 10 a few microns thick and a few meters wide -
detonated from the center - plated with MEMS based chemical rockets to
maneuver freely in space - and equipped with a coating on one side
that glows intensely in the X-ray region when energized - that coating
covered with MEMS based phase control units - described here

http://www.youtube.com/watch?v=jWuL4sZ3ppY

The sheet is detonated by a fissile trigger. The blast wave spreads
across the surface, energizing the coating. The coating sticks around
about 20 times longer than the boron sheet that energizes it - and
glows intensely in the X-ray region all that time. The phase control
rods are oriented to form a controlled well-defined pattern of X-ray
light in a specific area.

That's it!

A vehicle, brings a few thousand of these self powered sheets to the
vicinity of an appropriately sized asteroid. They self-deploy around
the asteroid, after a careful survey is done, and then they detonate
according to a well engineered sequence producing well defined regions
of intense Xray illumination to create well defined high speed jets of
ejecta from the surface of the asteroid - all times and controlled so
as to maintain the integrity of the asteroid as its being moved.

In sci.space.policy message
, Sun, 28 Feb 2010 16:22:19, Sylvia Else
posted:

Well, yes, but the point is that if, as is suspected, asteroids are
held together by gravity, then the force that can be applied without
making them come apart is very small. Changing the orbit of such an
object would require the application of a small force over an extended
period of time, which is going to be hard to achieve using bombs.

In the present context, "bomb" has inappropriate connotations. A nuke
exploding near an asteroid is not like a hand-grenade in the same room.
It gives (I suppose) no solid shrapnel, and rather little blast, for its
energy, in the sense of moving gas.

It should be thought of more as a VERY bright flash-bulb.

Neither would give much push to a perfect mirror, because photons have a
poor momentum/energy ratio.

A force applied at a point will of course tend to scatter a rubble-pile;
the same is not true of a well-distributed force.

A rubble-pile passing not far outside its Roche Limit with a large body
will receive a considerable force, but fairly evenly distributed.

--
(c) John Stockton, nr London, UK. Turnpike v6.05 MIME.
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
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Dr J R Stockton wrote in
nvalid:

This assumes the object is a reasonably solid object; more recent data
suggests most asteroids are dusty accretions loosely constituted by
their own weak gravity. A large disturbance can, and has been observed,
to break up asteroids into multiple impactors. Ask the Jovians.

Procede cautiously.
YSCIB.

Remember that in a vacuum a nuke generates comparatively little direct
blast. The idea is not to give the whole target a massive shock, but to
dump enough energy into the surface that it boils. The ejecta will go
radially outwards from most of the illuminated hemisphere, pushing the
rest inwards. That is a comparatively favourable situation.

The necessary caution should not be exaggerated.

Assuming that by using "Jovians" you are referring to the impacts of
SL-9 (D/1993 F2) in 1994 : it was broken up in 1992 when it passed
within Jupiter's Roche limit. It felt a substantial tidal field for
some hours, pulling it apart. The analogy is weak.

As are the forces holding together rubble piles, especially elongated
ones.

I disagree that Jupiter's gravity "pulled apart" SL-9; it almost
certainly induced a tumble that the object pulled itself apart
into it's many constituent parts. Wouldn't take much considering
the very tiny amount of gravity present to hold it together. An
adjacent nuclear explosion would do the same if the energy caused
surface material to ablate violently.

These things will have to be handled with relative delicacy.

--Damon

On 2/03/2010 5:36 AM, William Mook wrote:
SO, if you navigate the planetoid into a tight orbit say 1,000 km
above Earth, it will rip apart due to gravitational forces.

But, is breaking up a planetoid that you want to process into useful
stuff a bad thing?

It's an exceptionally bad idea. When it breaks up, the pieces don't
enter nice well behaved circular orbits. They enter elliptal crossing
orbits. That is, the pieces will subsequently collide with each other.
You'd end up with a space debris problem on a vast scale.


To me it seems like a good way to use tidal forces to process
asteroids for you.

Why not get relatively dense objects and use them as shepherd moons to
keep pieces from being a threat to navigation and safety and then
bring stuff into the space between the shepherd moons and let tidal
forces tear them apart for you?

You have to find them first.

Sylvia.

On Mar 1, 9:41�pm, Sylvia Else wrote:
On 2/03/2010 5:36 AM, William Mook wrote:

SO, if you navigate the planetoid into a tight orbit say 1,000 km
above Earth, it will rip apart due to gravitational forces.

But, is breaking up a planetoid that you want to process into useful
stuff a bad thing?

It's an exceptionally bad idea. When it breaks up, the pieces don't
enter nice well behaved circular orbits. They enter elliptal crossing
orbits. That is, the pieces will subsequently collide with each other.
You'd end up with a space debris problem on a vast scale.



To me it seems like a good way to use tidal forces to process
asteroids for you.

Why not get relatively dense objects and use them as shepherd moons to
keep pieces from being a threat to navigation and safety and then
bring stuff into the space between the shepherd moons and let tidal
forces tear them apart for you?

You have to find them first.

Sylvia.

can you imagine the ground effects of a rubble asteroid breaking up in
earth orbit?

lets see it would cool the planet, maybe cause a ice age, cause
massive food production problems cut off most or all space ased
operations like satellite tv, telephone, and credit card processing,
disrupt or end air travel, since the debris could get sucked into jet
engines, ISS would be toast, access to space perhaps ended for
thousands or millions of years, it could end life as we know it on the
earth........

all bbecause a asteroid happened to play pool with the earth, and
direct iumpact with the surface wouldnt be necessary

In sci.space.policy message ,
Mon, 1 Mar 2010 18:10:16, Damon Hill posted:
Dr J R Stockton wrote in
. invalid:


Assuming that by using "Jovians" you are referring to the impacts of
SL-9 (D/1993 F2) in 1994 : it was broken up in 1992 when it passed
within Jupiter's Roche limit. It felt a substantial tidal field for
some hours, pulling it apart. The analogy is weak.

As are the forces holding together rubble piles, especially elongated
ones.

I disagree that Jupiter's gravity "pulled apart" SL-9; it almost
certainly induced a tumble that the object pulled itself apart
into it's many constituent parts. Wouldn't take much considering
the very tiny amount of gravity present to hold it together. An
adjacent nuclear explosion would do the same if the energy caused
surface material to ablate violently.

You are entitled to your own opinion. I doubt whether anyone else will
want it. You should endeavour to obtain a physics degree, or to consult
reputable authorities.

--
(c) John Stockton, near London.
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