[ExI] new job

[Stuart LaForge]

On 2024-12-18 15:24, Adrian Tymes via extropy-chat wrote:
> On Wed, Dec 18, 2024 at 5:28 PM Keith Henson via extropy-chat
> <extropy-chat at lists.extropy.org> wrote:
> 
>> On Wed, Dec 18, 2024 at 1:58 PM BillK via extropy-chat
>> <extropy-chat at lists.extropy.org> wrote:
>>> On Wed, 18 Dec 2024 at 20:54, Adrian Tymes via extropy-chat
>> <extropy-chat at lists.extropy.org> wrote:
>>>> What would it take to nudge Apophis from "might impact Earth
>> later" into a stable orbit around the Earth, or perhaps the Moon
>> (and thus around the Earth)?
>>> 
>>> Perplexity AI thinks it is an impossible task.
> 
> And makes a few mistakes in the data while doing so.  But yes, this is
> certainly not a task to be done before 2029.

Have you accounted for the Oberth effect? On April 13, 2029, it will be 
only 13,600 km from Earth and travelling very fast. Any impulse that we 
can give it on that day would have the greatest effect on its kinetic 
energy. There might be a way to use a fancy gravitational slingshot 
around the Earth and the moon to put it in some stable orbit or 
Lagrangian point. My point is that the closest approach is the best time 
to give it a "nudge". Maybe AI can figure out the optimal solution.

>> With current technology, I agree.
>> 
>> With self-replicating nanotechnology, you could turn the whole thing
>> into a light sail and fly it wherever you want.
> 
> You wouldn't even need self-replicating nanotechnology, just something
> that can grind up asteroid mass and turn it into solar sail material,
> along with assembly robots to put it in place.
> 
> If we're consulting with AIs, Claude.ai gives the following if 1% of
> Apophis was turned into about 270 km^2 of solar sail material:
> 
> Solar radiation force at 0.9225 AU:
> Pressure = 9 μN/m² × (1/0.9225)² = 10.57 μN/m²
> Total force = 270,000,000 m² × 10.57 × 10⁻⁶ = 2,854 N
> Delta-v per year:
> a = 2,854 / (27 × 10⁶) = 1.057 × 10⁻⁴ m/s²
> Yearly delta-v = 1.057 × 10⁻⁴ × 31,557,600 = 3,335 m/s per year

The problem with solar sail is that Apophis tumbles and flips around its 
three axes of rotation. How can you attach a sail to the asteroid 
without it getting tangled and twisted?

> ...one year's worth of which might be a bit more than is needed to
> capture Apophis.  Launch the machinery during a close pass, perhaps
> 2036.  Give it several years to make, deploy, and test the sail.
> Start capture operations a bit over a year before the next close pass,
> in this case 2051.  (Maybe two years, since the 2029 approach will put
> it in a slightly longer orbit with lower solar radiation force
> available.)  Maybe do have self-replicating factories, but with
> macrotech rather than nanotech.

Two government space craft are commissioned to go to Apophis in 2029: 
The ESA's RAMSES probe and NASA's Osiris. It would be interesting if 
some private space craft were also at the rendezvous.

Stuart LaForge