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29 votes
Accepted

Why wouldn't the world have advanced warning of a significant asteroid/comet strike?

The near-Earth objects we look for are mostly in the plane of the ecliptic, because that is where the vast majority of solar system material not in the Sun is to be found. The object that is about to ...
SoronelHaetir's user avatar
25 votes

Negative pressure projectile propellants (Alternatives to gunpowder)

It sounds like a poorly conceived idea. Reason? With increasing pressure you can go up as much as you want, the limit being the strength of your barrel. If 20 bar of up pressure are not enough, you ...
L.Dutch's user avatar
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21 votes

Why wouldn't the world have advanced warning of a significant asteroid/comet strike?

So a counterpoint to your view. The world thinks there is no warning system, not because it doesn't exist, but because the world has no way to respond to this information. A world ending meteorite ...
Flotolk's user avatar
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18 votes

Why wouldn't the world have advanced warning of a significant asteroid/comet strike?

The Asteroid was caused by the collision of 2 other asteroids that were not anticipated to hit earth So, there are two asteroids flying on a merry orbit, close-ish (in astronomical terms) to earth - ...
TheDemonLord's user avatar
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16 votes

How disadvantageous would symmetrical, four-fingered hands be?

If you mean a hand a bit like this: then I don't think it would be of any significant disadvantage, so long as the fingers and thumbs had fleshy pads similar to those of human hands and the thumbs ...
Penguino's user avatar
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15 votes

Why wouldn't the world have advanced warning of a significant asteroid/comet strike?

It could be an extra-solar object like 'Oumuamua. That would explain why it hadn't previously been detected. A sky survey might pick it up, but since it's heading almost directly towards us on a ...
N. Virgo's user avatar
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14 votes

With modern technology would it be possible to build an HG Wells style Martian tripod?

When it comes to 'possible', a War of the Worlds tripod should be achievable with near-future technology, pretty much just the R&D required to actually build the thing. While it wouldn't be the ...
Monty Wild's user avatar
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14 votes
Accepted

Keeping an airship aloft using only propellers (and nuclear reactors)

There aren't many Small Modular Reactor designs for which a mass has been given. One for which there is a mass figure is the Hyperion Power Module, which weighs 'less than 50 tons' and produces 25MW. ...
Monty Wild's user avatar
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11 votes
Accepted

Efficient method of storing energy in a near-future, semi-hard sci-fi game

Perhaps Pretorium has a stable nuclear isomer that can store a lot of energy for a long time, and is easy to trigger to release that energy, making it ideal to be used to make a nuclear battery If ...
Monty Wild's user avatar
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9 votes

How disadvantageous would symmetrical, four-fingered hands be?

You're fine. Based on how humans actually grip things, they can do every grip humans can. If anything, a few grips might actually work better. The diagonal grip will be the only one weaker. You are ...
John's user avatar
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9 votes

With modern technology would it be possible to build an HG Wells style Martian tripod?

Probably Doable Currently the tallest robot built to date that walks on legs is an 18 meter tall, 25 ton, bipedal Gundam replica in Yokohama Japan. Although this robot is not quite as tall or heavy ...
Nosajimiki's user avatar
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9 votes

Efficient method of storing energy in a near-future, semi-hard sci-fi game

Frame-challenge. This is a science-fiction answer to a science-based question. I wrote it that way because the constraints of the elements on the projected island of stability as science knows them ...
Escaped dental patient.'s user avatar
9 votes

Why wouldn't the world have advanced warning of a significant asteroid/comet strike?

Really bad luck Estimates show that an asteroid in excess of 1 kilometer in diameter impacting Earth would be a civilization-kill event. While we have found over 90% of near earth 1-kilometer ...
Bubbles's user avatar
  • 879
7 votes

Why wouldn't the world have advanced warning of a significant asteroid/comet strike?

Maybe it doesn't orbit; it's an interstellar object that strikes the Earth on the way through. We had our first recorded passage through the solar system of an interstellar object recently: https://en....
Robertiton's user avatar
7 votes

Keeping an airship aloft using only propellers (and nuclear reactors)

Have a look at the Convair NB-36H. This is 1950's technology. It had a nuclear reactor and propellors. One was not actually connected to the other but it could have been, and would have been if a ...
Richard Kirk's user avatar
  • 9,489
7 votes

Negative pressure projectile propellants (Alternatives to gunpowder)

This - or something adjacent to this - has been done before. Ultimately, there's no reason not to use regular propellant. Normal things explode just fine, and if you have the tech to make something ...
controlgroup's user avatar
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6 votes

How many people can China geographically support?

How many people can China support depends on the meaning of support. The People's Republic is the world's largest food importer; it imports food worth about 130 to 140 billion dollars per year. This ...
AlexP's user avatar
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6 votes

Keeping an airship aloft using only propellers (and nuclear reactors)

Your propeller-airship is just a very large helicopter. So yes, it's possible, but just like with helicopters, it uses absurd amounts of energy to stay aloft. A side note: the suction on the top of ...
Burki's user avatar
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5 votes

With modern technology would it be possible to build an HG Wells style Martian tripod?

I think the tripods could work but they may be a bit different to the machines that are typically drawn on 'War of the Worlds' book covers. The robots in the MIT and Boston Dynamics labs are very ...
Richard Kirk's user avatar
  • 9,489
5 votes

Efficient method of storing energy in a near-future, semi-hard sci-fi game

So if the element was discovered in the future and it is on the island of stability, this element must have an atomic number above 119 and is a theoretical element. As stated the pretorium has a half-...
Khorzin's user avatar
  • 184
5 votes

How to fight effectively on a space station

Why risk our guys at all? A space station is a hostile environment life-support system. All we need to do is reversibly break the life-support system and we win for free. Turn up the heat. 1: Wrap ...
g s's user avatar
  • 7,277
5 votes

Keeping an airship aloft using only propellers (and nuclear reactors)

"Can you launch an ICBM horizontally?" "Sure, why would you want to?" (The Hunt for Red October) From a science-based perspective, yes, you can create the airship you're talking ...
JBH's user avatar
  • 124k
5 votes

Negative pressure projectile propellants (Alternatives to gunpowder)

As stated by the other answers, vacuums are a bad idea. However, consider this answer a loose interpretation of your final sentence. A coilgun "sucks" metal projectiles forward out of the ...
David Robie's user avatar
4 votes

With modern technology would it be possible to build an HG Wells style Martian tripod?

It wouldn't be possible with these specifications, but with some changes, it would be plausible There was a project similar to tripods in the 60s, the "Pedipulator", a machine that walked on ...
Khorzin's user avatar
  • 184
4 votes
Accepted

Colonizing a frozen Waterworld

Frame Challenge: Your story line is about faced. At the moment? Your traveling to the planet to colonize it and then terraforming it. In reality? You would need to Terraform the planet first and then ...
Mon's user avatar
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4 votes

Keeping an airship aloft using only propellers (and nuclear reactors)

Frame-ish Challenge So - in your question - you never specified how high up said vehicle was to travel. Which gives me a chance to talk about one of my favourite bits of Aviation lore: WIGs or as the ...
TheDemonLord's user avatar
  • 27.3k
4 votes

Negative pressure projectile propellants (Alternatives to gunpowder)

Using suction to "pull" the projectile has one major drawback: as you suck at the projectile, you are also sucking at the air outside the barrel with the same but opposite force. The air ...
Going Durden's user avatar
  • 3,956
3 votes

Why wouldn't the world have advanced warning of a significant asteroid/comet strike?

This might seem simple, but it does explain the "Why did we not notice this ?" The asteroid is moving significantly faster than usual. (Maybe it's naturally accelerated, maybe it isn't, ...
Or4ng3h4t's user avatar
  • 470
3 votes

Colonizing a frozen Waterworld

Paraphrasing: If Earth were moved to the outer main asteroid belt (and the belt and Jupiter removed), and humans came upon it, what could we do? Land, dig graves, occupy graves. Unless you are ...
David G.'s user avatar
  • 1,377
3 votes

Appropriateness of lasers for alien plant control

This is already happening here. Have a look at the Mosquito Laser. If the targeting mechanism becomes cheap enough, then this can deny territory such as inside a house to mosquitoes. This is not the ...
Richard Kirk's user avatar
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