For Questions That Don't Merit Their Own Thread

[p1t1o]

10 minutes ago, peadar1987 said:

To be honest, I don't really value small children above or below anyone else. I'd run over two small children to save three adults in a heartbeat (and run over two adults to save three children). What if the car has to make a choice about whether to hit a doctor, or two criminals? At a certain point, you just have to go with the solution that will result in the best outcome most of the time. I don't really have any time for the argument that the cars will decide who lives and who dies, if they have the potential to save many lives on average over a long enough period of time, from a utilitarian perspective that's far better than whatever permutations of the trolley problem people can come up with.

Well, I'd give small children a priority because they have more life left to lose, in a manner of speaking. And neither of those situations call for you to sacrifice *yourself*. But the difference in, ahem, "value" between 2 groups isn't what I think the main difficulty is, that will always be a quagmire: "Is a teacher worth more than a janitor? Is a President worth more than a teacher?" etc. etc. The difficulty that the survey says to me is: "Automatic cars should sacrifice the driver to save 2 people. Except when I'm the driver."

Its a tough one. Personally I think that our society is still to obsessed with blame and punishment to be able to accept putting that much control in the hands of a software developer. It will all be roses and sunshine until somebody's daughter gets crushed to death by a car that wasn't initially going to hit her, but swerved into her to avoid someone else, or worse, to avoid something *it thinks* is someone else.

I think I actually just decided I'm not a great fan of self-driving cars.

[PB666]

7 hours ago, peadar1987 said:

To be honest, I don't really value small children above or below anyone else. I'd run over two small children to save three adults in a heartbeat (and run over two adults to save three children). What if the car has to make a choice about whether to hit a doctor, or two criminals? At a certain point, you just have to go with the solution that will result in the best outcome most of the time. I don't really have any time for the argument that the cars will decide who lives and who dies, if they have the potential to save many lives on average over a long enough period of time, from a utilitarian perspective that's far better than whatever permutations of the trolley problem people can come up with.

You dont have to run them over, you can walk them over, or just stop and sit on them, heh-heh. 

[Vanamonde]

How about we get away from who it would be more or less ethical to run over and get back to discussing science in the science subforum?

[RainDreamer]

How about instead of thinking about what to do in case of an accident, we think about how to prevent them from happening at all with a better traffic system using self driving car? Things like sensor near roads to check for land slides, acess to weather data to regulate speed and traffic, etc. If anything happens at all it would be something no one can expect to make a decision for anyway

Edited June 26, 2016 by RainDreamer

[PB666]

6 hours ago, RainDreamer said:

How about instead of thinking about what to do in case of an accident, we think about how to prevent them from happening at all with a better traffic system using self driving car? Things like sensor near roads to check for land slides, acess to weather data to regulate speed and traffic, etc. If anything happens at all it would be something no one can expect to make a decision for anyway

When they talk about accidents, most traffic accidents are the result of several unexpected coincidental events, so the reality is that a vehicle that avoids such coincidences by slowing down or avoiding high risk situations whike generally not be causal. 

[magnemoe]

On 24.6.2016 at 10:02 AM, p1t1o said:

 

This was quite interesting, even if it was from Gizmodo. Jist of it is: A survey showed that people want self driving cars to attempt to minimise any casualties in an accident, even if it means putting the safety of its own occupants at risk. However, the same survey showed that not very many people would be willing to travel in such a car...

http://gizmodo.com/your-self-driving-car-will-be-programmed-to-kill-you-de-1782499265

 

Overestimating the smartness of the software a lot, it would not be capable of making this sort of decisions as it can not calculate it, look on how much google street view mess up with statues or billboards and that is not real time analyze in an overload setting. 
Way more relevant is the settings there the car would drive of the road to avoid an direct hit, An ditch filled with snow works well for up to 80 km/h litobraking, No damage to car in two experiences You would ditch the car to avoid hitting people or an car head on anyway. This saved my sister who tumbled on an motorbike after hitting an pothole, car in other direction ditched, significant damage on car, no damage on her or bike, her insurance covered the car repair, everyone was happy. 
Note that this is stuff you are likely to run into driving an car during your life unlike this hypothetical setting, you tell the car you have 10 kids in the trunk to be sure

 

[p1t1o]

5 hours ago, magnemoe said:

<snippity-snip>

Sure of course, its a hypothetical - "What if cars could make this kind of decision?". We can't rule it out for the unknown future, could be almost inevitable.

[PB666]

17 hours ago, p1t1o said:

Sure of course, its a hypothetical - "What if cars could make this kind of decision?". We can't rule it out for the unknown future, could be almost inevitable.

Driverless cars will inevitably be safer than humans, particular when they can crosstalk about hazards and emergent situations. 

[shynung]

Is it possible to create a device able to project a blob of plasma carrying lethal amounts of energy in a controllable fashion?

Or, in other words, is it possible to build a plasma gun?

[p1t1o]

41 minutes ago, shynung said:

Is it possible to create a device able to project a blob of plasma carrying lethal amounts of energy in a controllable fashion?

Or, in other words, is it possible to build a plasma gun?

This question comes up SO. OFTEN!

The classic response is: plasma is essentially very hot gas. A gun that fires hot gas, you can imagine, will be very hard to weaponise.

 

Its very much more efficient/effective to generate plasma in-situ on contact with the target, these weapons are commonplace:

https://en.wikipedia.org/wiki/Shaped_charge

Or you can use the expansion of plasma to drive a projectile:

https://en.wikipedia.org/wiki/Explosively_formed_penetrator

Think of it like this: solid high explosive is like stabilised plasma stored in a cold, dense state . Probably the best way we currently have to project it at a target.

 

If you are looking for a real-world approximation of the plasma rifle from DOOM, this is probably about as close as you will get - and considering the validity of the "first response" is pretty damn close actually!: (although "rifle" might be pushing it!)

https://en.wikipedia.org/wiki/Shiva_Star

https://en.wikipedia.org/wiki/MARAUDER

"Shiva Star was also used to develop an experimental weapon known as MARAUDER for the SDI effort between 1989 and 1995. The idea appears to have been to createcompact toroids of high-density plasma that would be ejected from the device using a massive magnetic pulse.[2] The plasma projectiles would be shot at a speed expected to be 3000 km/s in 1995 and 10,000 km/s (3% of the speed of light) by 2000. A shot has the energy of 5 pounds of TNT exploding; although it caused little or no physical damage, the energy would shower the interior of the target with high-energy x-rays that would potentially destroy the electronics inside. The tests cost a few million dollars a year.[3] The project was scrapped at some time after 1995 because of problems keeping the plasma projectiles stable for the distances required by orbital weaponry."

[PB666]

3 hours ago, shynung said:

Is it possible to create a device able to project a blob of plasma carrying lethal amounts of energy in a controllable fashion?

Or, in other words, is it possible to build a plasma gun?

THe way to do this is to have a confining RF beam that keeps the gas isolated. There is a thing called cold plasma, but its not as damaging as one might want.

The first step in the process is to agitate the gas to get it to loose one of its outershell electrons, this generally can be done with vacuum UV, next step up the frequency progressively to remove lower electrons. This can be done with UV/Xrays. Finally to put pressure on the nucleus this can be done with Xrays (this gives the final bit of force required for a hydrogen-bomb). This gets the gas to move quite rapidly and in the confined space created by RF it will move in the direction of the momentum imparted by the Xrays.

I have to say, the xrays over great distance will probably be more damaging to the target than the plasma. In fact why waste your time, photon weapons achieve the same result, if you know the surface composition of the target, just pound the target with different wavelengths at its excitations frequencies, and dumb in a few X-rays, that has the effect of generating basically alpha and beta particles, but at much higher doses than a typical laboratory.

[Core]

Microwave rifles would be interesting. Just watch out for the ricochet.

 

Now to restate a previous question of mine in a more clarified way:

If there was a Halo structure (like those in the Halo series) that had a mass equal to that of the Earth, how would the gravity be effected on it, and how would orbits around this structure work?

Edited June 28, 2016 by Core
Forgot something.

[andrewas]

If you are far enough away from it, you can orbit it more or less as normal. The gravity will be non-spherical which means that orbits will precess, and since the mass distrbution is much more extreme than Earth's, this precession will be much faster than it is in Earth orbit. I'm not sure how low you can go and still have a stable orbit.

Within the ring, gravity will be towards the near side of the ring, and towards the plane of the ring. There are no stable orbits within the ring. At the center point all gravity cancels, but the slightest perturbation will result in you leaving that center point and gravity will accelerate you towards the ring.

[p1t1o]

9 hours ago, andrewas said:

If you are far enough away from it, you can orbit it more or less as normal. The gravity will be non-spherical which means that orbits will precess, and since the mass distrbution is much more extreme than Earth's, this precession will be much faster than it is in Earth orbit. I'm not sure how low you can go and still have a stable orbit.

Within the ring, gravity will be towards the near side of the ring, and towards the plane of the ring. There are no stable orbits within the ring. At the center point all gravity cancels, but the slightest perturbation will result in you leaving that center point and gravity will accelerate you towards the ring.

I think any orbit outside of the ring and in the plane of the ring, should be stable. You should be able to orbit very close to the underside of the ring.

[Wjolcz]

How small can a graphene-based computer be? And I don't mean a simple logic gate, but an actual computer that could act as a normal PC or a phone. Would that enable smartphones to be paper-thin and super fast?

[DDE]

21 hours ago, p1t1o said:

Its very much more efficient/effective to generate plasma in-situ on contact with the target, these weapons are commonplace:

https://en.wikipedia.org/wiki/Shaped_charge

* cough * Shaped charge warheads are hypervelocity kinetic weapons, not plasma ones. They drive a stream of superplastic solid metal, not plasma.

[p1t1o]

36 minutes ago, DDE said:

* cough * Shaped charge warheads are hypervelocity kinetic weapons, not plasma ones. They drive a stream of superplastic solid metal, not plasma.

I knew that they are kinetic weapons, that they dont "burn" or "melt" their way through, but I was under the impression that the jet was hot enough to be plasma. Browsing some literature, the term "plasma jet" is used quite widely (and i know how to avoid places fall into the various misconception traps) however, temperatures of jets are quoted in various places as being in the 500-odd degree range, which is not hot enough for plasma to form. 

Though I did find confirmation that plasma is formed in the heart of most high-explosive detonations, and if you make a shaped charge without a liner, you do indeed form a plasma jet - you will get much less penetration without a liner however.

Just goes to show that you don't really need plasma for any reason, but it tends to show up in high energy events, more as a by-product than anything else.

If we didn't give "plasma" such a cool name, I doubt it would be brought up so often in weapon discussions.

Edited June 29, 2016 by p1t1o

[PB666]

Why do we devolve into weapons you exactly don't want to use in space because of the self-destructive projectiles they produce. If an alien race wanted to destroy all space programs on earth the would detonate a shape charge in retrograde orbit in the side of the shape are lined with couple of 100000 1 inch cubes, and eclosed in a couple of million inch sized cubes.

[DDE]

14 hours ago, PB666 said:

Why do we devolve into weapons you exactly don't want to use in space because of the self-destructive projectiles they produce. If an alien race wanted to destroy all space programs on earth the would detonate a shape charge in retrograde orbit in the side of the shape are lined with couple of 100000 1 inch cubes, and eclosed in a couple of million inch sized cubes.

Something something forcefield.

Ultimately it's quite possible to angle the explosive ordnance so that the parasitic frag ends up in a short-lived orbit.

[PB666]

15 hours ago, DDE said:

Something something forcefield.

Ultimately it's quite possible to angle the explosive ordnance so that the parasitic frag ends up in a short-lived orbit.

Not nuclear about the best you can do is a disk.

[peadar1987]

8 hours ago, PB666 said:

Not nuclear about the best you can do is a disk.

You could probably get full coverage eventually if you fired it off in a polar orbit. Collisions with debris in equatorial or inclined orbits would produce shrapnel with all sorts of crazy inclinations.

[todofwar]

Anyone have recommendations for scientific journals on planetary science? My university subscribes to pretty much everything so pay walls aren't an issue

[RocketSquid]

Does fission produce enough Xenon-135 to run an ion engine?

[PB666]

35 minutes ago, RocketSquid said:

Does fission produce enough Xenon-135 to run an ion engine?

If you exhaust velocity is c, yes. Power efficiency is horrible.

[peadar1987]

34 minutes ago, RocketSquid said:

Does fission produce enough Xenon-135 to run an ion engine?

Short answer. No. Xenon-135 has a half-life of about 9 hours. About 6% of U-235 fissions to Xenon-135. Half of this transmutes to Xenon-136 through neutron capture. You're going to get about 3% of the mass of the U-235 in the fuel as Xenon. At 4% enrichment, that's 0.0012% of the nuclear fuel. You're not going to produce enough Xenon to make any sort of meaningful difference.