Starship Asterisk*

There are allot of good ideas in older science fiction movies and books. Lots of stuff about resource harvesting and mining. And, newer often does not mean better. Or is someone looking for some free consulting? :wink:

Norval

The article I read on this said that objects as small as 100 meters can do significant damage. It also said landing a propulsion unit has problems such as the object may be very loosely conglomerated and it's rotation could cause problems (the article did not mention that some small objects have chaotic rotation). Also blowing it up may make things worse.

I thought you could use a mass and a solar sail for propulsion. The mass would be at the end of a tether very close to the object for the maximum attraction and the sail can be as large as you want. Presumably with thrusters you need to be further away to avoid hitting the asteroid and loosing net thrust.

I remember reading Carl Sagan on this topic and he said this technology would be the most dangerous thing ever invented because someone could direct a near miss object into a collision. However, it could also be used to capture an object for fuel or metals which could have a tremendous economic value (compared to the cost of sending mass up into orbit).

Geeee, S. Bilderback, I guesses yah didn't read them thar scientists reports in the pdf format? They strongly disagree with you. Doing it the ion way is the most efficiant they says. :lol:

That aside, my assessment is with you about the direct approach. There are several easy ways with the technologies and capabilities available today it "should" be a snap. Why then isn't it? And, these folks seem to be stumbling around in the dark compared to 30 years ago. Go figure.

Norval :wink:

Landing a thruster unit on the asteroid and have it capable of stopping or controlling the asteroid's rotation and also give it a gentle nudge would be the most economical solution if brut force doesn't lend itself as a feasible solution.

I'd still like the use of a 100 M-ton H-bomb and see one of those things do something useful. If 800 lbs of inert copper could rip-up Tempel 1 as it did with only a 19 Gigajoules collision (that's 4.8 tons of TNT), think of what 20 million times that would do.

An interesting concept, which probably shouldn't be dismissed out of hand.
(1) Collisions may be more efficient at transferring momentum, but this method is feasible only for rocky asteroids, which won't shatter. A comet or water-ice asteroid might fragment on impact, making the problem potentially worse.
(2) As some postings point out, 20 tons is a modest size for towing an asteroid. The small gravitational attraction would certainly limit the acceleration that could be achieved.
(3) Rather than rely on any kind of tether, physical or otherwise, why not land on the asteroid and install a reactor and ion drive on its surface? Unless the asteroid was a conglomerate of separate bodies, this would allow much greater thrust to be applied.
(4) Another method (which would preserve the visual impact of this painting) involves a "tug" with diametrically opposed ion thrusters. By hovering close to the asteroid and directing one thruster at its surface, while the other thruster maintained the tug's position, substantial momentum could be transferred to the asteroid. In addition, this might also transfer a large electrical charge, raising the interesting possibility of an "electrostatic" tether, which could be orders of magnitude stronger.
(5) I understand the purpose of showing the half-illuminated Earth in the background, but, since its apparent size approximates that of the moon from Earth, it must be on the order of only a million miles away. One would hope that the tug's work has already been accomplished at this point!
(6) As for the asteroid towing the rocket vs the other way around, neither viewpoint is technically accurate. In fact, the rocket's ion thrusters will accelerate the combined mass of the rocket-asteroid system. Neither one "tows" the other [/i]per se[i].[/i]

I would believe that the asteroid would most likely tow the rocket with its stronger attraction.
Orin

The energy it would take to send a 20 ton tug out into the orbital path far enough out to change the orbital path of an asteroid before it hit the Earth would be astronomical! It would be much more efficient to slam the tug into it.
In perspective, in close proximity, the gravitational pull between two aircraft carriers is in the neighborhood for 5 lbs (100,000 tons per carrier), depending on the size of the asteroid, 50 years of advanced warning maybe needed to get there and get the job done.

http://antwrp.gsfc.nasa.gov/apod/ap051110.html

But it will take twenty years to move just a 200 meter object enough to miss earth.

I think that NASA scientists should talk to a few tug boat skippers that do this for a living. Try contacting Crowley or Foss companies for some real information on attempting such operations. http://www.nicholsboats.com/tug_boats.htm and
http://www.ebdg.com/portfolio/tugboats.htm

Gravity towing? A twenty ton rocket is going to produce enough "gravity" with it's mass to be able to pull ,,,,,,,,,,,,,, nothing.
So, where does the "gravity tow line" come from? :?

When we can make a "tractor beam" we will have unattached "tractor tugs".

Get a think tank with some diverse "experience", besides just knowing there are things called tug boats. :)

Norval