For Questions That Don't Merit Their Own Thread

[DDE]

3 hours ago, ARS said:

Is it feasible to create a reusable railgun that addressed the heat and rail durability problem by making the railgun projectile packed with single-use rails in one package? With the actual barrel seen outside being coilgun accelerators? Essentially, a railgun "shell" is a self-contained single-use railgun designed to fire the projectile to attain initial velocity into the barrel before being accelerated by accelerator coils inside the barrel. In theory, this makes the railgun cheaper to maintain by eliminating the need for expensive alloys for reusable accelerator rails since the rails on the shell is intended to be single use

Why are you bothering with a Gauss gun? Just eject the rails once expended, or better yet, let the recoil eject them out the other end.

[ARS]

So... This thing has been bugging me for a while. Recently there's an accident near my place, a car was hit by a train when it goes across the train crossing and trapped when the safety gate closes, no survivors. EVERY DAMN TIME there's accident like this, everyone (even live report and newspapers) said that the car stopped in the middle of the track because there's an electromagnetic field emitted by the train crossing as the train about to pass (some goes even more specific, saying that the arrival of train (somehow) magnetized the rails and disables car's engine and locks it in place). I'm very skeptical about this explanation since every accident like this (especially when the car stopped in the middle of the track) always explained with "magnetized rail". Keep in mind that the trains in my country mainly consisted of diesel-powered train (no electric, TGV or Shinkansen-like trains and the rails, while it's made from ferrite, it is not electrified). Could someone explain the "car engine stopped in the middle of train crossing" problem? Also, does a "magnetized rail" explanation true or not? Because I haven't find a single piece of scientific explanation/article about it in internet, which makes me suspect this is a hoax

Edited July 3, 2019 by ARS

[kerbiloid]

Afai-just-read, as the railway crossing is highly automated, ~2 km of railway from either side of the crossing are equipped with a signal chain to automatically switch the lights and barriers when a train is "on rails" (both literally and in Kerbal sense). All this several kilometer long distance are one big button being pressed by the trains. So, it is anyway powered, regardless of the locomotive engine.
 

Edited July 3, 2019 by kerbiloid

[ARS]

11 minutes ago, kerbiloid said:

Afai-just-read, as the railway crossing is highly automated, ~2 km of railway from either side of the crossing are equipped with a signal chain to automatically switch the lights and barriers when a train is "on rails" (both literally and in Kerbal sense). All this several kilometer long distance are one big button being pressed by the trains. So, it is anyway powered, regardless of the locomotive engine.
 

Except not in my country. Every railway crossing has a guard post with a personnel inside. The only connection on the rail is located several kilometer away from guard post, which is a sensor that notifies a train is arriving, this activates a bell on guard post to alert the personnel to press the button on the guard post to close the safety gate. The rails on the crossing is literally just steel beams buried inside the asphalt

Of course, there IS a train accident in my country that's caused by personnel not hearing the bell and didn't close the gate (one infamous accident in my town involves the personnel wearing headphones when it's prohibited), but that's another topic

[DDE]

3 hours ago, ARS said:

So... This thing has been bugging me for a while. Recently there's an accident near my place, a car was hit by a train when it goes across the train crossing and trapped when the safety gate closes, no survivors. EVERY DAMN TIME there's accident like this, everyone (even live report and newspapers) said that the car stopped in the middle of the track because there's an electromagnetic field emitted by the train crossing as the train about to pass (some goes even more specific, saying that the arrival of train (somehow) magnetized the rails and disables car's engine and locks it in place). I'm very skeptical about this explanation since every accident like this (especially when the car stopped in the middle of the track) always explained with "magnetized rail". Keep in mind that the trains in my country mainly consisted of diesel-powered train (no electric, TGV or Shinkansen-like trains and the rails, while it's made from ferrite, it is not electrified). Could someone explain the "car engine stopped in the middle of train crossing" problem? Also, does a "magnetized rail" explanation true or not? Because I haven't find a single piece of scientific explanation/article about it in internet, which makes me suspect this is a hoax

At surface level? It’s a reversed railgun - no power source and a self-propelled projectile make it a very simplified, but fully functional model of an electric generator. I can definitely see how it can generate a current, diesel or not.

Question is how that field affects a car.

Edited July 3, 2019 by DDE

[kerbiloid]

Maybe somebody in that thread is aware?

 

[Kerbinchaser]

2 hours ago, kerbiloid said:

Maybe somebody in that thread is aware?

 

What is the question?

[kerbiloid]

7 minutes ago, Lo Var Lachland said:

What is the question?

 

[Flibble]

Never heard of anything like that and we have automated crossings here. I have seen video of a car missing a train by centimetres and the engine kept running. Even if the engine cut out the car would roll off the crossing anyway.

[cubinator]

Why don't amputation surgeons use lasers to cut through limbs? It seems like it would work pretty well if you used a typical cutting laser with several passes.

[Spacescifi]

15 minutes ago, cubinator said:

Why don't amputation surgeons use lasers to cut through limbs? It seems like it would work pretty well if you used a typical cutting laser with several passes.

 

Money. As it is doctors have been known to order X-ray and other tests that are not absolutely necessary for the patient.... just to get some of the cost back of buying the machine. Kind of hard to justify use of lasers to get back the cost of the machine when cheaper options are available. Like automated blades/saws.

Something tells me that a cutting grade laser would be expensive.

Also, from a medical point of view, you may or may not want to cauterize the flesh around a cut. With a laser you will likely end up cauterizing the surrounding flesh of the cut, so if you do not want that... you get where I am going?

Edited July 3, 2019 by Spacescifi

[cubinator]

 

4 minutes ago, Spacescifi said:

Something tells me that a cutting grade laser would be expensive.

I think it would be within the range of what a lot of other medical equipment costs...You could basically just change the shape of a typical CNC laser cutter and tune it to the right settings.

4 minutes ago, Spacescifi said:

Also, from a medical point of view, you may or may not want to cauterize the flesh around a cut. With a laser you will likely end up cauterizing the surrounding flesh of the cut, so if you do not want that... you get where I am going?

I see that you might not want to cauterize it. It would be less messy, though, and would leave a clean, flat cut.

[Spacescifi]

4 minutes ago, cubinator said:

 

I think it would be within the range of what a lot of other medical equipment costs...You could basically just change the shape of a typical CNC laser cutter and tune it to the right settings.

I see that you might not want to cauterize it. It would be less messy, though, and would leave a clean, flat cut.

 

It is not always about clean though. These are limbs afterall, not wood.

I am thinking that cauterizing will definitely kill nerve endings and such.

Not to say they won't come back, but it just seems... excessive.

 

By the way, they do use lasers for cauterising incision lines, so as to seal them.

[Kerbinchaser]

8 hours ago, kerbiloid said:

@ARS

This does not exist here in the United States. Here, crossings are triggered by a sensor further down the track, which is activated when the train rolls past it. There is no "electromagnet" and cars you are able to cross with the lights still active. I looked for a diagram all over the internet but could not find anything. 

Edited July 4, 2019 by Lo Var Lachland

[ARS]

@Lo Var Lachland, I found 2 discussions that discussed about the problem. It seems the claim that the car magically "stalled" when crossing the railway is dubious, especially when there's an added mumb-jumbo of "EM field generated from passing train". Maybe you're interested

Links:

EM field on tracks: https://www.quora.com/Does-a-kind-of-magnetic-field-from-an-incoming-train-really-cause-a-car-to-stall-on-the-tracks#

Engine stalls: http://cs.trains.com/trn/f/111/t/84781.aspx

 

[magnemoe]

1 hour ago, ARS said:

@Lo Var Lachland, I found 2 discussions that discussed about the problem. It seems the claim that the car magically "stalled" when crossing the railway is dubious, especially when there's an added mumb-jumbo of "EM field generated from passing train". Maybe you're interested

Links:

EM field on tracks: https://www.quora.com/Does-a-kind-of-magnetic-field-from-an-incoming-train-really-cause-a-car-to-stall-on-the-tracks#

Engine stalls: http://cs.trains.com/trn/f/111/t/84781.aspx

 

This its no magnetic field to speak of, add that the rails are grounded, they are also segmented up and segments are used to activate the railway crossing and to show the trains position at the rail controll center. 

Now as many rail crossings are higher than the road they might have an incline up to them, also the crossing of the track might be a bit bumpy this might stall the engine if driving at slow speed and high gear. Then people panic and freeze. 
 
 

[Nightside]

1 hour ago, ARS said:

@Lo Var Lachland, I found 2 discussions that discussed about the problem. It seems the claim that the car magically "stalled" when crossing the railway is dubious, especially when there's an added mumb-jumbo of "EM field generated from passing train". Maybe you're interested

Links:

EM field on tracks: https://www.quora.com/Does-a-kind-of-magnetic-field-from-an-incoming-train-really-cause-a-car-to-stall-on-the-tracks#

Engine stalls: http://cs.trains.com/trn/f/111/t/84781.aspx

 

I don’t believe the EM field story, it sounds too much like a problem for a Star Trek engine room (hint: did you try to reverse the polarity?)

To me it is a way of avoiding responsibility for a crash. The driver may be avoiding responsibility for fouling the tracks with an immobile car, the railroad company may be avoiding responsibility for a faulty signal.

anyway, I haven’t stalled a moving car but I have stalled out plenty when starting from a stop. 

Moral of the story: Don’t stop your car on the tracks.

[micha]

I find it dubious that a railway crossing might induce sufficient electrical interference to stall an ICE.

Also, if you ever -do- stall in a situation where you have to get the heck out of in a car, don't bother trying to restart the engine (there are many reasons why it might have stalled, including terminal ones such as simply being out of fuel). First gear and bunny-hop away using the starter.

Of course, that only works in manual cars.

[kerbiloid]

Spoiler

A traditional culture explanation.

As any crossroads, the railway crossing is a magic place, where the material world meets the world of dreams.
When a carriage is passing it, the driver can stick in a typical nightmare dream when you are on rails and can't run from the approaching train.
Sometimes the dream train gets materialized in the material world.

 

[Flibble]

4 hours ago, micha said:

I find it dubious that a railway crossing might induce sufficient electrical interference to stall an ICE.

Also, if you ever -do- stall in a situation where you have to get the heck out of in a car, don't bother trying to restart the engine (there are many reasons why it might have stalled, including terminal ones such as simply being out of fuel). First gear and bunny-hop away using the starter.

Of course, that only works in manual cars.

My starter will only fire with the clutch in.

[magnemoe]

5 hours ago, Flibble said:

My starter will only fire with the clutch in.

Same with mine, and yes this prevent you starting the car by accident it also stop you from moving it on the starter. 

[Spacescifi]

 

Could we make a flashlight powerful enough to emit god-rays (crepuscular rays)?

Not by putting extra stuff in the air (too easy), but by pure power?

 

I think we could, but the light source would probably be plasma, since any flashlight that powerful should melt the reflector I think.

Edited July 4, 2019 by Spacescifi

[kerbiloid]

Spoiler

 

[Spacescifi]

12 minutes ago, kerbiloid said:

  Hide contents

 

 

In broad daylight I meant.

At night is too easy.

[micha]

14 hours ago, Flibble said:

My starter will only fire with the clutch in.

Ah yes, all the modern "safety features" which actually bury useful functionality.  Aim for the lowest common denominator and evolution will take care of the rest.