Re: Earth-grazing asteroids as a military resource

On 05/03/2025 15:19, john larkin wrote:

On Wed, 5 Mar 2025 10:02:17 +0000, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:
 

On 04/03/2025 22:59, TTman wrote:

On 04/03/2025 02:02, Bill Sloman wrote:

The latest New Scientist talks about asteroid 2024 YR4 being
downgraded from a 1 in 32 chance of hitting Earth (the 17th February
estimate) to a one in 25,000 chance on the 24th February.
>
It's some where between 40 and 90 metres in diameter. Presumably there
are more smaller asteroids (which will be harder to see).
>
Eventually some military clown is going to get the idea finding a few
of them and sending up stick-on ion drives, so that the earth-grazing
orbits can be shifted into earth-impacting orbits.
>
A couple of them hitting Russian occupied-areas of the Ukraine would
upset Putin no end.
>

>
Excellent suggestion.! Needs some clever maths calcs though...

>
Timing is everything in orbital dynamics.
>
The Earth is moving along it's orbit at 30km/s and the impactor is
similar or possibly faster depending on its orbital parameters. IOW just
a couple of minutes difference between a direct hit and a miss.

 Or milliseconds.

100MT equivalent KE would have a fireball ~10km across - much like the Russian 100MT Tsar Bomba. And be a penetrating ground burst as well.
You can afford about 300ms error and still annihilate a target.
Make a mess of the surrounding countryside too. No fallout but for a very big asteroid impact cloud cover might make it an extinction event.
Serious effort is made to spot anything that might one day intersect with the Earth in its orbit. Quite a lot of Earth crossing asteroids.
Fortunately Jupiter acts as a cosmic vacuum cleaner for the solar system catching comets and tearing them apart. A la Shoemaker Levy 9.
(back in the good old days when humans spotted them first)

Its actually better than that since glancing impacts will skim off the
upper atmosphere like a stone does off off a pond. And only iron or
stone ones coming in at relatively steep angles get to reach the ground.
Many are loose aggregates of ice and pebbles that disintegrate on entry.

 Drones are more sensible weapons.

Autonomous ones look a bit too much like Terminator for my liking.
--
Martin Brown