A Gravitational Tractor For Towing Planetoids, Saving both Earth and Space Rocks Options

[Toma B]

I thought among the big arguments *against* nuclear weapons use on a threatening NEO was that if the NEO was too big, a nuclear explosion would not budge it.  Also, if the NEO is essentially a big rubble pile barely held together by gravity (which is what Itokawa sure looks like), then a detonation might only shatter the space rock and just spread the debris over more places on Earth.

My favored scenario is attaching a rocket or two or more on the NEO and having the continual thrust from their engines eventually push the rock into a non-threatening orbit.  Not destroying the NEO also saves it for future study and space resource use.

If NEO is to BIG for Hydrogen bomb to nudge it slitely of its Earth-colliding course than nothing that we can make can save us...
If NEO is RUBBLE-PILE bomb will shatter it and there will be a nice meteor storm ( with bright fireballs ) , even if some larger chunk remains it will only cause local damage,nothing on the global scale...
I would more thrust the BOMB because it is several thousand times tried unlike Gravity tractor which never is...

P.S.

AAARRGGHHH!!!!
My English is not so good...
I need 3-5 times more time to write post than most of you guys...

[Bob Shaw]

All in all, I'd rather have a few thousand 100-meter craters and the ensuing, potentially manageable destruction casued by them, than have a single 200-km cratering event whose blast effects would wipe out most life on Earth...

-the other Doug

Doug:

I think it's a case of 'horses for courses' - but that the gravitational tug remains a striking, and so far as I can see, feasible, new idea which is well worth pursuit. The 'Don Quixote' impact experiment is well and good, but I'd far rather see a tractor experiment sooner rather than later...

Bob Shaw

[ljk4-1]

Astrophysics, abstract
astro-ph/0102126

From: Donald Korycansky [view email]

Date: Wed, 7 Feb 2001 22:40:53 GMT (84kb)

Astronomical engineering: a strategy for modifying planetary orbits

Authors: D. G. Korycansky, Gregory Laughlin, Fred C. Adams

Comments: 21 pgs, 7 figs. Paper to appear in Astrophysics and Space Science

Journal-ref: Astrophys.Space Sci. 275 (2001) 349-366

The Sun's gradual brightening will seriously compromise the Earth's biosphere within ~ 1E9 years. If Earth's orbit migrates outward, however, the biosphere could remain intact over the entire main-sequence lifetime of the Sun. In this paper, we explore the feasibility of engineering such a migration over a long time period. The basic mechanism uses gravitational assists to (in effect) transfer orbital energy from Jupiter to the Earth, and thereby enlarges the orbital radius of Earth. This transfer is accomplished by a suitable intermediate body, either a Kuiper Belt object or a main belt asteroid. The object first encounters Earth during an inward pass on its initial highly elliptical orbit of large (~ 300 AU) semimajor axis. The encounter transfers energy from the object to the Earth in standard gravity-assist fashion by passing close to the leading limb of the planet. The resulting outbound trajectory of the object must cross the orbit of Jupiter; with proper timing, the outbound object encounters Jupiter and picks up the energy it lost to Earth. With small corrections to the trajectory, or additional planetary encounters (e.g., with Saturn), the object can repeat this process over many encounters. To maintain its present flux of solar energy, the Earth must experience roughly one encounter every 6000 years (for an object mass of 1E22 g). We develop the details of this scheme and discuss its ramifications.

http://arxiv.org/abs/astro-ph/0102126