wrote on Mon, 3 Sep 2018 18:18:21 -0700
(PDT):

On Monday, September 3, 2018 at 7:29:47 PM UTC-4, wrote:
"The notion of an asteroid headed for Earth is typically seen as a bad omen. On
the flip side, some scientists and entrepreneurs increasingly see this scenario
as a potential opportunity. Deliberately redirecting asteroids to our planet’s
vicinity could enable us to study them up close, or even mine them.

Given that these objects are packed with valuable resources, building a
collection of them nearby could spark major advances in spaceflight, to say
nothing of the scientific research that might result from easy access to these
extraterrestrial bodies.

A recent paper published in Acta Astronautica suggests that asteroids could be
captured in Earth’s orbit with aerobraking, a maneuver that uses atmospheric
drag to decelerate and position objects in stable trajectories around a planet.
Aerobraking has helped place interplanetary spacecraft in orbit around Mars and
Venus, and to slow down spacecraft returning to Earth.

Led by Minghu Tan, a PhD student at the University of Glasgow, the paper
immediately addresses the most obvious concern with this scenario: What if
there’s some mistake in the redirect process and an asteroid accidentally
impacts Earth? It’s bad enough that the dinosaurs were oblivious to their
doomsday space rock, but it would be especially embarrassing if we humans smack
ourselves in the face with one."

See:

https://motherboard.vice.com/en_us/a...o-earths-orbit


Using aerobraking is a rather touchy affair. It implies a high
thrust impulse on the asteroid to begin the transfer orbit.

A small impulse to use gravitational capture allows the use of an
emergency escape engine to eject a failed capture.


Except the rationale for using aerobraking is that you cannot paste a
big enough engine on a target asteroid to stick it in orbit without
using something like aerobraking to slow it down.


Small vectoring to one of the L orbits and a mass limit rule
would be an alternative.


Again, how big an engine with how much fuel do you think you can lift
up to an asteroid? Personally, I prefer 'lithobraking' by tossing
them into a lunar crater and then sending a crew in to mine out the
content by conventional means. Nobody gets hurt and it's easier than
mining and smelting the things in deep space.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden