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Deflecting the killer
asteroids cheaply and easily
How
many times have we heard about an asteroid colliding with Earth
and destroying our civilization? How many disaster movies
have been made with that plotline? Here is a short list:
- The Day the Sky Exploded (Italian) -1958
- Meteor - 1979 - Sean Connery
- Asteroid - 1997 - Michael Biehn
- Deep Impact - 1998 - Robert Duvall & Morgan Freeman
- Armageddon - 1998 - Bruce Willis (no relation - too bad)
There have also been numerous TV
specials and even mini-series with the same plotline.
The solution
has been known to scientists for DECADES. But of course
Hollywood wouldn't want to spoil the opportunity to make a lot of
money with the simple solution. Surprisingly the media has not
managed to find the WELL-KNOWN solution either. But of course
the media is always trying to alarm the public and whip the public
into a frenzy over nothing.
The
solution: A Coilgun or Mass Driver
History: It starts with the
linear induction motor
From Wikipedia we quote: "A feasible linear induction motor is
described in the US patent 732312 (1905 - inventor Alfred Zehden of Frankfurt-am-Main ),
for driving trains or lifts. The German engineer Herman Kemper built a working model in
1935. In the late 1940s, the late professor Eric Laithwaite of Imperial College in London developed the first full-size
working model." Mass drivers were built and tested at
MIT in the 1970s. My patented spaceship propulsion system (US
patent 5,305,974) uses a variation of the coilgun which is called
an electromagnetic projectile launcher. This propulsion
system is 1000 times better than rockets but NASA is not interested
because of the NIH syndrome (Not Invented Here).
Literature: Novelists
have NOT overlooked the linear induction motor or Mass Driver. The
first reference found in literature is described in Wikipedia
here. 1897: From Wikipedia we quote: "The
first mass driver known in print was actually called the
"electric gun" and described in detail as a way to launch
vehicles into outer space from the earth's surface. It appeared in the 1897 no
longer copyrighted science fiction novel "A Trip to Venus" -
by John Monroe and was published in 1897 by Jarrold & Sons, London. The
book is out of copyright and freely available as a text file from the
project gutenberg.org " 1966: (Robert A.
Heinlein) In his novel, The Moon Is a Harsh Mistress mass drivers are used by Lunar rebels to
launch artificial meteorites in an orbital bombardment of the Earth.
1976: The High Frontier - Human Colonies in Space (Gerald K. O'Neill) This novel describes in some detail the precise
solution required to solve the "killer asteroid" problem.
The Solution: As was described
by Gerald O'Neill, you simply place a mass driver on the asteroid and
have it chew up small amounts of the asteroid and spit them out into
space using the mass driver. According to Newton's third
law of motion - "For every action, there is an equal and opposite
reaction" - as you throw asteroid material into space from its
surface, an equal and opposite force will push the asteroid in the
opposite direction. Of course in this case we wish to deflect
the orbit of the asteroid so that it will miss the Earth.
Physics and Math: We
now show mathematically how this solution can be accomplished.
1. Select our candidate
asteroid. Let the asteroid be 1000 meters in diameter - or
1 kilometer.
The volume is:
Volume = 4/3 * pi * radius3
Volume = 1.33333 * 3.14159 * 500 * 500 * 500 =
523.6 million cubic meters.
or Volume
= 0.524 billion cubic meters.
2. Select the density
of our asteroid. The density of asteroids varies from
about 2 to as high as 7.
We
choose 4 grams per cubic centimeters as a likely density.
3. Calculate the mass of
the asteroid: Mass = volume * density
Mass = 0.524 billion cubic meters * 4 metric tons per cubic meter.
Mass = 2.096 billion metric tons = 2 trillion kilograms
4. Select
our ejection mass. Just pick some number - say
200 kg = 1/5 metric ton.
For a density of 4, this would amount to 1/20 of a cubic meter -
or about 1.75 cubic feet.
5. Select
our ejection velocity. Mass drivers are capable of
almost any velocity but of course the larger the velocity the bigger
and more expensive the launcher will be - and also the more likely
that it will malfunction. Actually mass drivers or EMPLs
(electromagnetic projectile launchers) are capable of anything from 1
kilometer per second up to 100 kilometers per second or even
higher. We pick 1 kilometer per second to make the mass driver as
small as possible. velocity = 1 Km/sec = 1000
meters per second.
6. Calculate the
momentum of the ejected mass.
The momentum is: Momentum = mass * velocity
Momentum = 0.2 MT * 1000 m/s = 200 MT (m/s)
7. Calculate the
resulting reaction on the asteroid in terms of opposite velocity (per
launch).
This is the deflection velocity which is perpendicular to the
normal motion of the asteroid.
Reaction velocity is: Velocity = Momentum of
ejected mass / Mass
of asteroid
Deflection Velocity = 200 MT (m/s) / 2 billion MT
Deflection Velocity = 10-7 meters per second (per launch)
8. Calculate
the number of launches per day. Clearly the number of
seconds in a day is 86,400.
Let us try for one launch every 10 seconds. This would be
8640 launches per day.
9.
Calculate the change in velocity achieved each day.
Velocity increase per day = 8640
launches per day * 10-7
m/sec (per launch)
Velocity increase per day = 0.000864 m/sec per day.
10.
Calculate the change in velocity achieved in one year.
Velocity increase per year = 0.000864 m/sec per day *
365 days = 0.315 m/sec per year
11.
Calculate the total deflection of the asteroid over one year
Total deflection = Average velocity * Total time (seconds per year)
Total deflection = 0.5 * [Initial velocity + Final
velocity] * Total time (seconds per year)
Total deflection = 0.5 * [ 0 + 0.315 m/sec] * 31.5 million
seconds per year
Total deflection = 0.5 * 0.315 m/sec * 3.15 x 107
seconds per year
Total deflection = 0.496 x 107 meters per year
Total deflection = 5,000,000 meters = 5000 kilometers
in the first year
12.
What about the second year? Clearly the final
velocity will be twice as large.
Total deflection = Average velocity * Total time (seconds per year)
Total deflection = 0.5 * [Initial velocity + Final
velocity] * Total time (seconds per year)
Total deflection = 0.5 * [ 0.315 m/sec + 0.630 m/sec ] * 31.5 million
seconds per year
Total deflection = 0.5 * 0.945 m/sec * 3.15 x 107
seconds per year
Total deflection = 1.49 x 107 meters per year
Total deflection = 15,000,000 meters = 15,000 kilometers
in the second year
Conclusion:
A SINGLE mass driver operating as outlined above could deflect a 1
kilometer asteroid by 5000 kilometers in a single year and 20,000
kilometers in two years.
Obviously for insurance we would send a lot more than one - perhaps as
many as 50. Also, if the asteroid were 2 kilometers in diameter,
the mass would be 8 times as large and the deflection would be only
625 kilometers in one year (for each mass driver). Clearly a rogue
asteroid which is less than a year away could still be deflected if we
sent a large number of mass drivers to attack it - or if we increased
any of the several parameters of the mass driver mentioned
above.
Implementation:
Our choice of implementation would depend heavily upon (1) the size
of the asteroid, (2) the amount
of time we expect to have before a potential catastrophic collision
with the Earth - and of course upon (3) the distance from Earth to
the asteroid in question. NASA's currently preferred
method of interplanetary travel is the rocket - which I have pointed
out above is a POOR (i.e. SLOW) method of travel - but it could work
given enough time. As you know from past missions to Mars, it
takes NASA about 8 months to reach Mars and years to reach Jupiter or
Saturn. Thus, we would LOSE at least 8 months (and perhaps
years) of deflection if we were to use NASA's rockets and the asteroid
was as close as the orbit of Mars. My propulsion system can
reach Mars in 5 weeks and Jupiter in 6 months. Hence by using my
propulsion system, we would have many more months (or years) of
deflection to apply. In any case, the mass driver
itself would obviously be powered by a nuclear reactor.
Since there will be no people involved in this mission, NO shielding
will be required for the reactor. I would recommend assembling
the mass drivers in high Earth orbit and sending them on their way
using my propulsion system.
Cost: As you can read
in my book Jobs for the 21st Century, I have shown how a manned
mission to Mars can be accomplished for under $10 billion.
Since this mission would be much simpler, I think we could be
confident that it too would cost under $10 billion.
Books of interest
Comments? Email me at crwillis@androidworld.com
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