[X] My Assistant

[Bob Shaw]

Can I suggest you all have a look at the link I posted above, which gives a brief but very clear summary of the facts - in particular, one of the (many) benefits is that the gravitational tractor method sorts out all the problems to do with a rotating asteroid (landing, pointing the engines, and the rest).

Remember that to safely deflect an asteroid we need a tiny change in it's orbit, if caught early; to exploit asteroidal resources would require orders of magnitude greater velocity changes (even if an asteroid *could* be brought into a loose association with the Earth by clever orbital billiards, I for one would not be happy unless there was some substantial fail-safe boost option for the thing!).

Bob Shaw

[chris]

Can I suggest you all have a look at the link I posted above..

Bob Shaw

Nice paper, thanks for pointing it out.

Chris

[ljk4-1]

There is an entire thread on the towing topic here:

http://www.unmannedspaceflight.com/index.p...indpost&p=21361

[tty]

I don't think that a force of some tons would break appart a pile of rubble like Itokawa.

It would, if applied long enough

We could perhaps need a large foot for the thruster, or mount it on a larger block. But basically it is like pushing a hill with a buldozer: we don't break the hill, even if it is just a loose heap of stones or sand. I think there are some common laws between our ordinary world on Earth and the world out in space.

That hill is kept together by the gravity of a body of rocks about 8,000 miles in diameter. An asteroid isn't.

Using an atom bomb looks more efficient; but if you put the bomb close, there is a serious risk of breaking the rubble pile (or comet nucleus or any other soft space material) turning a probable asteroid threat into a certain meteorite shower. If you fire it at safe distance to avoid this, the asteroid receives only a blast of hot gasses which is not very efficient to push it. Not accounting with the risk of radioactive pollution, and all the environment/legal concern about sending a nuclear weapon in space. So it is not so simple as it looks at first glance.

It would, as I wrote, have to be detonated some distance away, and actually that blast of high-velocity plasma (not gas) will transfer its momentum rather effectively to the asteroid. Some of the surface material will vaporize but that is all to the good since the recoil will increase the momentum transfer. It's actually a variety of the old "Orion" nuclear pulse concept.
As for the radioactivity, if the Earth is hit by a comet at least I won't care if it's a bit radioactive. It is very unlikely that I (or anyone else) will survive long enough for it to matter.

tty

[ljk4-1]

How about covering it in reflective material as I once saw as an
alternative idea to nuking a space rock? Too little energy to
generate in time to move it away from Earth?

Attach solar sails to all potential Earth-crossers and start moving
them now so by the time they would have been a real threat,
the effort will have made them otherwise. Why wait around
until finding out we only have a few decades at most to
deflect them? A pre-emptive shove, I say.

[ljk4-1]

Now here we go: Let's fight fire with fire:

http://www.newscientistspace.com/article.n...line-news_rss20

What we should ultimately do is "corral" most Earth-crossers and put them
in a "safe" place for eventual mining as we create our space colonization
infrastructure in the Sol system. No sense wasting some perfectly good
resources already in space that will be easy to land and lift off from.

The article also has a cool artwork of a spacecraft on a collision course
with a planetoid that looks like a cousin to Hyperion.

[Guest_BruceMoomaw_*]

Once again, this leads me to the discouraging conclusion -- pointed out by a growing number of SF writers -- that, if we do start shoving near-Earth asteroids around, the odds are tremendously greater that Earth will be hit within the next few million years (or the next few THOUSAND!) by a rock deliberately aimed at us by some political faction elsewhere in the Solar System than by one thrown at us by Mother Nature within the next few tens of millions of years.

[Guest_Richard Trigaux_*]

From here (again) the need to develop more wisdom and eliminate wars and their causes, otherwise all our nice techs will not protect us of ourselves. But this is another topic.

[ljk4-1]

Once again, this leads me to the discouraging conclusion -- pointed out by a growing number of SF writers -- that, if we do start shoving near-Earth asteroids around, the odds are tremendously greater that Earth will be hit within the next few million years (or the next few THOUSAND!) by a rock deliberately aimed at us by some political faction elsewhere in the Solar System than by one thrown at us by Mother Nature within the next few tens of millions of years.

One of Carl Sagan's big concerns in the last few years of his life
was some group using the technology to move planetoids and
aiming them at Earth instead:

http://trs-new.jpl.nasa.gov/dspace/handle/2014/33485

[ljk4-1]

The following is from Larry Kellogg's list regarding the recent close
passage of a PHA and Arecibo's radar study of it - where it found that
it is not a single object.


anntransfer.com/mn/0402/19.htm

- NEODyS has posted 2004 DC & 2004 DD

http://www.hohmanntransfer.com/mn/0402/19.htm#risks

Risk monitoring 19 Feb.

NEODyS has joined JPL in posting 2004 DC and also today has posted 2004 DD.
The latter was announced yesterday in MPEC 2004-D07 as discovered Tuesday
morning by Arianna Gleason with the Spacewatch 0.9m telescope in Arizona and
confirmed over the next night by KLENOT in the Czech Republic, the
Starkenburg Observatory team at Calar Alto in Spain, and Arianna Gleason
with the Spacewatch 1.8m telescope. From its brightness (JPL H=17.89), this
object is roughly estimated at 895 meters/yards wide.

None of the objects listed with impact solutions and currently in view were
reported in the Thursday Daily Orbit Update MPEC.

http://www.hohmanntransfer.com/mn/0402/24.htm

Summary Risk Table - sources checked at 2359 UTC, 24 Feb

-------------------------------------------------------------
http://www.morien-institute.org/skywatch2006.html

Skywatching Calendar 2006
-------------------------------------------------------------

http://www2.jpl.nasa.gov/calendar/

Snip

# Jun 03 - Asteroid 2004 DC Near-Earth Flyby (0.026 AU)

http://neo.jpl.nasa.gov/cgi-bin/db_shm?des=2004+DC

http://www.cfa.harvard.edu/iau/Ephemerides...al/K04D00C.html

# Jun 03 - New[Jun 01] Asteroid 2006 KJ89 Near-Earth Flyby (0.098 AU)

# Jun 03 - Asteroid 232 Russia Closest Approach To Earth (1.226 AU)

=============================================================
Space Weather News for June 3, 2006

http://spaceweather.com

What's Up in Space -- 3 Jun 2006


BINARY ASTEROID: Asteroid 2004 DC is flying by Earth today about 2.5
million miles away. Yesterday, astronomers using the giant Arecibo radar in
Puerto Rico pinged the asteroid and discovered that it is actually two
asteroids--a 60m rock orbiting a 300m rock. Researchers estimate that one in
six near-Earth asteroids are binaries.

=============================================================

http://www.naic.edu/vscience/schedule/tpfi...rtagR2208tp.pdf

Technical Page
Proposal Type: Regular
General Category: Planetary Radar
Observation Category: Solar System

Total Time Requested: 10 Hours

Proposal Title: Physical Characterization of Potentially Hazardous Asteroid
2004 DC

ABSTRACT:

We request 10 hours of Arecibo S-band planetary radar time to physically
characterize potentially hazardous near-Earth asteroid 2004 DC. This is both
the first opportunity to observe this 0.7 - 1.5 km diameter (H = 18.1)
asteroid with radar and a rare opportunity to observe a large near-Earth
asteroid at a signal-to-noise ratio of several thousand per run. Radar
observations will refine the orbit of 2004 DC, describe its surface
morphology and radar reflection properties, and constrain its size, shape,
and spin state. High resolution radar imaging will resolve geologic features
several meters in size and determine if 2004 DC has any satellites.

=============================================================

http://www.cfa.harvard.edu/iau/lists/PHACloseApp.html

PHA Close Approaches To The Earth

The following table lists the predicted encounters by Potentially Hazardous
Asteroids (PHAs) to within 0.05 AU of the earth from the start of this year
through 2178. Objects with very uncertain orbits are excluded from this
listing, as are recently discovered objects whose orbits have been computed
without consideration of planetary perturbations. The distances quoted are
from the nominal orbit solutions in the cited references and can be quite
uncertain, particularly for one-opposition objects. Perturbed orbital
solutions consider perturbations by eight major planets (Mercury to
Neptune), three minor planets (Ceres, Pallas and Vesta) and treat the earth
and the moon as separate perturbing bodies. For comparison, the mean
distance of the moon is 0.0026 AU = 384400 km = 238900 miles. (1 AU is
approximately the mean distance of the earth from the sun = 149597870 km =
92955810 miles.)

Object (and name) Date of encounter (TT) Distance Orbit arc
Reference Object (and name)

Snip JD Calendar AU
2004 DC 2453890.33 2006 June 3.83 0.02586 2 oppositions,
2004-2006 E2006-L08 2004 DC

=============================================================
http://www.cfa.harvard.edu/iau/lists/Dangerous.html

List Of The Potentially Hazardous Asteroids (PHAs)

http://www.cfa.harvard.edu/iau/lists/InnerPlot2.html

Plot of the Innermost Solar System

http://www.cfa.harvard.edu/iau/Animations/Animations.html

The Animations Page

Here are links to a number of animations prepared at the Minor Planet
Center. They are not intended as rigorous depictions of the past and future
motions of the objects concerned (although at the scales of these diagrams,
any difference would probably not be noticeable), rather they are intended
to assist in understanding the state of knowledge about the contents of the
solar system ("A picture is worth a thousand words").

[ljk4-1]

Nuking Planetoid Golevka

Supercomputer Takes on a Cosmic Threat

http://www.space.com/businesstechnology/06...d_computer.html

A super-powerful computer has simulated what it might take to keep Earth safe
from a menacing asteroid.

[Guest_PhilCo126_*]

In the news this week:
A team of scientists supervised by Steve Ostro (NASA) and Jean-Luc Margot (Cornell University) established that binary asteroid KW4, discovered in 1999, will pose no danger to Earth...

[Guest_PhilCo126_*]

United Nations discussed the issue of a " doomsday " asteroid and what we could to about it:
http://www.cnn.com/2007/TECH/space/02/19/a...reut/index.html