Talk:Gravity tractor

Acceleration from body radius and tractor mass

It might be considered useful to present the relationship, for the optimal orbit around a spherical asteroid, between the acceleration achieved, the radius of the asteroid, and the mass of the tractor. I believe that I can provide this (assuming the asteroid to greatly outweigh the tractor), but it would need checking. 82.163.24.100 (talk) 19:14, 31 March 2009 (UTC)

See http://www.merlyn.demon.co.uk/gravity2.htm#GT. 82.163.24.100 (talk) 12:12, 1 April 2009 (UTC)

The obvious placing of the orbiting tractor is at a radius such that, firing aft, the exhaust just misses the asteroid surface. However, that cannot be optimum, unless it is necessary to mimimise fuel use : if the exhaust is directed slightly outwards, there is a second-order effect on the towing efficiency, but the tractor can be moved inwards by a first-order amount which has a first-order effect on the towing force. 82.163.24.100 (talk) 16:38, 3 April 2009 (UTC)

Advantages

The tidal forces are indeed small; but at the maximum they are larger than the average propulsive force. The tractor is a heavy object near to the asteroid's surface. One should consider whether surface material can be lifted; at least for likely masses, it seems not. 82.163.24.100 (talk) 11:55, 6 April 2009 (UTC)

Merge from Gravitational tractor

As far as I can see, a gravitational tractor is just another name for the gravity tractor. Therefore, I suggest it to merge into one article. Any (other) opinions? EmilTyf (talk) 23:55, 19 May 2009 (UTC)

Agreed. Anything in Gravitational tractor not here needs to be put here, and Gravitational tractor removed. 82.163.24.100 (talk) 17:00, 31 August 2009 (UTC)

I've gone ahead and done the merge. I didn't bring the text over from the old Gravitational tractor, because I didn't spend the time to crunch through all the numbers and compare them with the ones in this article. It seemed fairly duplicative, but if someone wants to take a closer look, go ahead. Kingdon (talk) 01:36, 31 December 2009 (UTC)

Reaction Mass Counterreaction

I completely agree with Kingdon's edit summary for edit 345033626 - the clause added in the previous edit was awkwardly worded and not very helpful. However, Patrick is correct that the fate of the reaction mass is a big issue for a hovering tractor. Wouldn't the exhaust slamming into the target (towed) object impart a force in the opposite direction of the (already miniscule) pull of the tractor? I don't know the numbers, but that's got to be a significant hurdle if not an outright negation of the intended delta-v.

I am therefore adding a paragraph under the Limitations section describing this problem. If my reasoning is wrong, please discuss here. ☯ Z.S. ☠ 17:16, 17 March 2010 (UTC)

I don't see any obvious problems with that text, but really it should be based on what the sources say rather than original research. I would imagine things like the distance between the craft and target and whether the reaction mass is in a tight beam or a wider one might matter, for example. Kingdon (talk) 14:06, 29 March 2010 (UTC)

Found and added one reference pretty quickly; I'm sure other, more in-depth ones exist. I'll hunt more diligently for them when I've got a bit more time for it. Thanks for responding! ☯ Z.S. ☠ ......(talk) 14:12, 30 March 2010 (UTC)

Thanks. Having that one is a big improvement over not having it cited. Kingdon (talk) 01:14, 4 April 2010 (UTC)

Found really cool, detailed JPL study done for B612 Foundation. The study specifically ponders a tractor vehicle with main thrusters angled 45° away from the object. If I happen across more references later, I'll put them in, but I think this is adequate for now. ☯ Z.S. ☠ ......(talk) 17:39, 8 April 2010 (UTC)