Astounding engineering feat

[rancke]

I'm trying to come up with an 'Astounding Engineering Feat" for a belter society. Basically AEFs are Wonder of the World stuff. Things people still talk about centuries later. (This particular one is from the 4th Century and it is still spoken of in 1105). It's very early in the history of the system, so it may "only" be astounding because of the scale compared to the small population. But what sort of engineering feats can you perform in an asteroid belt? There's no need for bridges and dams and stuff like that. Any ideas?

I've been thinking about putting spin on an asteroid to give it (pseudo-)gravity without the use of artificial gravity. Maybe diverting one astroid to graze another and put spin on it? Does that sound plausible?


Hans

 

[Agemegos]

How about bubble-forming an asteroid? Melt the whole thing, blow it like glass, draw it into a bottle shape, then let it cool. Install airlocks and set it spinning on the long axis. Fill it with air and landscape the inside. Et voila! Inside-out world like a giant O'Neill cylinder.

 

[far-trader]

How about some really complex asteroid shepherding feat? Some gritty old prospector who set up a pair (or more) of large asteroids in a gravitational shepherding orbit to keep all his claims in a nice tight grouping? Using just his old Seeker over several years. And it's still the biggest grouping and most valuable collection in the belt, now owned by his descendants. Just the first idea that popped into my head. Vaguely inspired by old farmers who would make quite solid and long stone fences from the stones they laboriously dug up out of the fields each time they plowed. All by sweat of brow and callous of hand.

 

[Peter Schutze]

an "ancient artifact" I'm planning to include in my campaign is a "chain of pearls" created by moving the big rocks to the same orbit and proximity etc with solar concentrators etc giving them a bright "sparkle"

 

[mike wightman]

Forming a rosette of your habitable asteroids.

 

[aramis]

How about bubble-forming an asteroid? Melt the whole thing, blow it like glass, draw it into a bottle shape, then let it cool. Install airlocks and set it spinning on the long axis. Fill it with air and landscape the inside. Et voila! Inside-out world like a giant O'Neill cylinder.

The heating required to do so would be insane...

 

[Icosahedron]

How about doing a Mega Mount Rushmore?

 

[Agemegos]

The heating required to do so would be insane...

Larry Niven suggested using a vast paraboloidal mirror of aluminised film (i.e. lightsail material) to do it. Assuming that you need to warm the asteroid up from 250 K to 1,500 K to melt the stone you would need a collecting area of about 1,300 times the profile of the asteroid. And this is supposed to be an astounding engineering feat.

Besides: isn't the energy required to change an asteroid's orbit significantly comparable to the energy required to melt it? The energy required to heat rock from SLTP to melting point and melt it is on the order of 1 MJ/kg, which is comparable to giving it a delta-v of 1.4 km/s: not a huge amount in orbital operations.

 

[Agemegos]

How about doing a Mega Mount Rushmore?

Carve some moon into a great leering Darsh face, perhaps?

 

[Agemegos]

Maybe diverting one astroid to graze another and put spin on it? Does that sound plausible?

Not to me. As far as I understand it, asteroids are not solid bodies, and certainly not bodies with structural strength comparable with engineered structures. Rather, they are loose or weakly-cemented agglomerations bound chiefly by their own feeble gravity and perhaps cemented with a little ice.If you were to set one spinning fast enough to produce a net outward-from-the-axis pseudogravity, then the centrifugal effect of the rotation would perforce exceed the centripetal effect of the poor thing's gravity, and the asteroid would come apart in a spray of rocks and gravel.

Now, a meteroid is a different story, being a boulder, a coherent chunk of rock bound by its mechanical strength. But those are too small to provide comfortable rotational pseudogravity, and besides it is hardly impressive, let alone astounding, to set one spinning like a top. A couple of RATO units would do it, or a few minutes with two M-drives.

 

[Agemegos]

Oo! Oo! Here's an astounding feat of engineering:

Drain all the ions out of the radiation belt of a gas giant, so as to allow exploitation of its inner moons! I think you could do it with a large electrodynamic tether: scoop 'em up with a Bussard ramscoop, essentially.

 

[Starviking]

A few thoughts spring to mind:

Perturbing the orbits of asteroids in order to cause them to collide/merge in order to create a larger body, AKA - we're going to make a planet, but it will take some time.

Adding grav to an asteroid, providing an atmosphere, and heating it by use of a parabolic mirror.

 

[Starviking]

Not to me. As far as I understand it, asteroids are not solid bodies, and certainly not bodies with structural strength comparable with engineered structures. Rather, they are loose or weakly-cemented agglomerations bound chiefly by their own feeble gravity and perhaps cemented with a little ice.If you were to set one spinning fast enough to produce a net outward-from-the-axis pseudogravity, then the centrifugal effect of the rotation would perforce exceed the centripetal effect of the poor thing's gravity, and the asteroid would come apart in a spray of rocks and gravel.

Regarding the structure of asteroids - most seem to be solid, though some are 'rubble-piles', at least according to ESA - http://www.esa.int/esaSC/SEM044W4QWD_index_0.html

 

[aramis]

Larry Niven suggested using a vast paraboloidal mirror of aluminised film (i.e. lightsail material) to do it. Assuming that you need to warm the asteroid up from 250 K to 1,500 K to melt the stone you would need a collecting area of about 1,300 times the profile of the asteroid. And this is supposed to be an astounding engineering feat.

Besides: isn't the energy required to change an asteroid's orbit significantly comparable to the energy required to melt it? The energy required to heat rock from SLTP to melting point and melt it is on the order of 1 MJ/kg, which is comparable to giving it a delta-v of 1.4 km/s: not a huge amount in orbital operations.

There's a consideration that you appear to have overlooked, and Niven handwaved: when you liquefy an asteroid in vacuum, some of the liquid escapes. You have to do it fast to minimize the losses, but then you also have to liquefy the core, and solar heating won't be doing that. It will boil off the surface and accelerate the asteroid. Silicates, BTW, are poor thermoconductors... The Energy of the fluid state should be sufficient to hit escape velocity on most small asteroids, and thus literally boil it away.

The Engineering feat isn't the heating, but the keeping it a single object while you manipulate it.

 

[Agemegos]

The Engineering feat isn't the heating, but the keeping it a single object while you manipulate it.

Use artificial gravity.

 

[aramis]

Use artificial gravity.

Which would then prevent inflation...

 

[Agemegos]

Which would then prevent inflation...

Only until you increase the gas pressure in the bubble. Gas pressure in the bubble interior will not tend to cause material to bleb off the shell exterior.

 

[Agemegos]

There's a consideration that you appear to have overlooked, and Niven handwaved: when you liquefy an asteroid in vacuum, some of the liquid escapes. You have to do it fast to minimize the losses, but then you also have to liquefy the core, and solar heating won't be doing that. It will boil off the surface and accelerate the asteroid. Silicates, BTW, are poor thermoconductors... The Energy of the fluid state should be sufficient to hit escape velocity on most small asteroids, and thus literally boil it away.

It won't boil unless it reaches boiling point, even in the very low gravity of an asteroid surface. You will lose the volatile material, a small splashes of the melt thrown off by bursting bubbles of evaporated volatiles, but not the bulk material. In general you don't boil stuff by heating it to its melting point, and a drop of water in free fall does not spontaneously fly apart as a mere result of being liquid.

At least some asteroids are believed to have melted (from fission of Al-26) in the early solar system, and to have survived in a molten state long enough for stone material to separate from nickel-iron, differentiating by density in feeble asteroidal gravity. If molten asteroids didn't boil away under self-heating then it doesn't seem obvious that they must do so when heated again.

 

[aramis]

Vaccum reduces boiling point. For most liquids, to very close to liquification point.

 

[rancke]

So how about this (all I need is a one-line chronological entry):

360: The Habeca Cooperative fuses 14 lesser asteroids to create Habeca Rock.​

Would that work?


Hans