For Questions That Don't Merit Their Own Thread

[magnemoe]

2 minutes ago, RoninFrog said:

Those guys have to be deaf.

My main question is how to get the water out of the barrel, just tumbling and planting your barrel into the ground and then fire will likely blow it up, yes an automatic is way safer here here as the gas can escape backward out the ejection port. Had this happen in the army then I get snow into the barrel and was only firing blanks but with would not want that on an non automatic gun. Fortunately guns tend to be weaker at the end, probably by design and by need, hunters has to move around for hours. 

However this is there the gyrojet could have their marked, use an rail barrel, just some rails to guide the projectile
For short range an bayonet works. Still gyrojet could have worked well for rifle greades. 

[RoninFrog]

On 4/19/2020 at 5:10 AM, ARS said:

Firing bullet underwater makes the bullet travel less due to underwater drag and significantly reduces its effective range. If say, there are 2 people swimming underwater, and they are at sufficient distance, is it possible for people to A fire a (non-underwater designed) bullet into person B, in such a distance that the bullet simply slows to a crawl just inches away from people B's face that the people B can clearly see the bullet before it drops down and sink underwater?

Yes.  If they are firing straight down or straight up.

[JoeSchmuckatelli]

On 4/20/2020 at 12:21 PM, kerbiloid said:

  Hide contents

 

 

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and others

https://lenta.ru/articles/2013/10/24/ads/

A nice technological solution to an extremely rare problem.

 

It doesn't look like a great solution for what SF guys need to do once they're feet dry. 

 

Given the bullet length, they're getting at best a pistol-length barrel - so I'm guessing (don't speak RU) that the effective range of this is about 25m.  Also, while I can't quite tell by the video, it looks like the leading edge is ridged; cavitation possibly?  So again, a nice technological 'solution' to a problem that won't / doesn't come up often in the real world

[kerbiloid]

1 hour ago, JoeSchmuckatelli said:

Given the bullet length, they're getting at best a pistol-length barrel - so I'm guessing (don't speak RU) that the effective range of this is about 25m.

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

30 m underwater (10 m at deeper underwater), 100 m in air.

[JoeSchmuckatelli]

3 hours ago, kerbiloid said:

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

30 m underwater (10 m at deeper underwater), 100 m in air.

Thanks for the link!

 

(And LOL:  "as a result, the APS is somewhat inaccurate when fired out of water"  )

[kerbiloid]

7 hours ago, JoeSchmuckatelli said:

"as a result, the APS is somewhat inaccurate when fired out of water" 

In this case the "inaccurate" means rotating 15 cm blades slashing the target at the pistol distance when they don't miss, lol.

Edited April 22, 2020 by kerbiloid

[DDE]

12 hours ago, JoeSchmuckatelli said:

Also, while I can't quite tell by the video, it looks like the leading edge is ridged; cavitation possibly?  So again, a nice technological 'solution' to a problem that won't / doesn't come up often in the real world

A recent and more versatile solution:

Spoiler

 

[DDE]

Israel's unmanned patrol boat program bites the dust after years of operational evaluations.

https://www.shephardmedia.com/news/uv-online/premium-israeli-usv-programme-hits-rocks/

[magnemoe]

On 4/22/2020 at 6:56 AM, kerbiloid said:

In this case the "inaccurate" means rotating 15 cm blades slashing the target at the pistol distance when they don't miss, lol.

This, now how did they deal with water in the barrel? Just get the front of the barrel filled with snow can easy destroy the gun. 
However that rocket bullet they made makes serious sense here you don't need an real barrel just use an mesh barrel, you could have an outer cover to protect hands. 
No it don't work at point blank range, add an bayonet. 

[Cunjo Carl]

What kind of bearings does turbo machinery use? Like on a turbojet or a turboshaft. I heard somewhere they use plain bearings, but that sounds crazy. Thanks in advance!

[RCgothic]

Depends on the speed and load. High speed bearings may not have any actual rollers - they are effectively plain bearings. But a slight axial offset generates a lift in the oil/grease that prevents them from contacting. Very clever.

But if they also need to work at slow speed and heavy load some actual rollers will probably be required.

[JoeSchmuckatelli]

On 4/23/2020 at 12:35 PM, DDE said:

Israel's unmanned patrol boat program bites the dust after years of operational evaluations.

https://www.shephardmedia.com/news/uv-online/premium-israeli-usv-programme-hits-rocks/

I'm highly leery of the Western fascination with the use of drones / unmanned vehicles.  

Two things come out of Russia's adventures in Syria: their unmanned AFV experience was dismal and their ability to interfere with NATO signals is increasing.  Absent the ability to have unrestricted use of the em spectrum for these drones - especially in peer to peer or peer to near-peer conflicts - the risks do not outweigh the benefits. 

[magnemoe]

2 hours ago, JoeSchmuckatelli said:

I'm highly leery of the Western fascination with the use of drones / unmanned vehicles.  

Two things come out of Russia's adventures in Syria: their unmanned AFV experience was dismal and their ability to interfere with NATO signals is increasing.  Absent the ability to have unrestricted use of the em spectrum for these drones - especially in peer to peer or peer to near-peer conflicts - the risks do not outweigh the benefits. 

Speed boat drones makes limited sense. They need to have some size to managing speed in rough water so they have to be boats anyway, yes you save a bit on not crewing them but get reliability problems. 
Platoon to company level UAV totally makes sense as they give very low level air recon, smaller and lower level drones makes even more sense especial if smarter. 

As you say larger stuff has issues, most of the current larger UAV would not work in WW2 as they would get shot down, however taliban don't have Zeros
They are low performance as they can get away with it.  US air force hated the idea of an cheap ground attack plane who would be effective but the accepted UAV as else the army would get them. 
And yes they don't work you fight peer to peer enemies, however this is rare, war in Ukraine  is the only one active between first world nations and its mostly an low intensity war. You had Nato against Serbia and the Falkland war, going back they become more common. 

[kerbiloid]

They should use a Fedorobot-like terminator on a scooter instead of these puny toyboats.

Because otherwise how can they not just sink the target, but board, inspect, and arrest the crew?

When they were babies, didn't they dream to be a lone pirate on a scooter?
Didn't they realize that grabbing the treasures from the hold is the most difficult part of the dream if the opponent's crew just laughs at you from above and rejects to put the cargo on your scooter?

[DDE]

11 hours ago, JoeSchmuckatelli said:

I'm highly leery of the Western fascination with the use of drones / unmanned vehicles.  

Two things come out of Russia's adventures in Syria: their unmanned AFV experience was dismal and their ability to interfere with NATO signals is increasing.  Absent the ability to have unrestricted use of the em spectrum for these drones - especially in peer to peer or peer to near-peer conflicts - the risks do not outweigh the benefits. 

You may be leery, but Western fascination with UGVs doesn't hold a candle to Russia's fascination with them. The same slidedecks that enumerate the failings of Uran-9/OKR Dolomite in Syria also present visions of entire unmanned battalions with tank-class drones. Russia wants (note the difference with the word "has") autonomous drone teaming, target acquisition and prosecution.

[kerbiloid]

These should have fronts gates to roll in.

Spoiler

 

[JoeSchmuckatelli]

10 hours ago, DDE said:

You may be leery, but Western fascination with UGVs doesn't hold a candle to Russia's fascination with them. The same slidedecks that enumerate the failings of Uran-9/OKR Dolomite in Syria also present visions of entire unmanned battalions with tank-class drones. Russia wants (note the difference with the word "has") autonomous drone teaming, target acquisition and prosecution.

Grin - politicians wanting the coolest new toys. 

@magnemoe  - yes, our local infantry support / recon stuff is working and handy, and the Predators (et.al.) have been wildly successful, and the drone swarm stuff looks deadly and promising...

TBH - I'm not surprised at industry or political interest in the technology... But that the professionals are not disuading the ground vehicle adventures is surprising. 

@magnemoe  

But as someone who has been in the 'keep mechanized fighting vehicles in the fight' game (read: service, supply, recover, repair and reissue taking up far more time than sending rounds downrange) - investment in heavy ground combat vehicles (at this time) is a fools errand.  The Russians have always been good at putting simple hard to break easy to fix stuff in the hands of the troops - which isn't a bad idea. They're also really good at artillery and rapidly expanding their emw capabilities - you would think that their collective experience would ameliorate any interest in overly technical solutions to simple problems 

[p1t1o]

On 4/25/2020 at 7:47 PM, Cunjo Carl said:

What kind of bearings does turbo machinery use? Like on a turbojet or a turboshaft. I heard somewhere they use plain bearings, but that sounds crazy. Thanks in advance!

I think they use some kind of suspended bearing or "air bearing" where above a certain low RPM, the bearing is actually levitated by air pressure - somehow using the rotation of the shaft itself -  in the centre of the bearing? Or something like that?

 

**edit**

beep-boop-beep google is your friend

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

 

Edited April 28, 2020 by p1t1o

[ARS]

Is it possible to reduce the G-force during reentry by making the reentry capsule outfitted with liquid breathing immersion module? So the crew is immersed in liquid to dampen the G-force, while still allowing them to breathe

[StrandedonEarth]

1 hour ago, ARS said:

Is it possible to reduce the G-force during reentry by making the reentry capsule outfitted with liquid breathing immersion module? So the crew is immersed in liquid to dampen the G-force, while still allowing them to breathe

I didn’t think immersing in dampened g-forces, merely increased how well the body tolerated gees. But you have to be breathing liquid as well, or the lungs would get crushed. And then there’s the weight penalty....

[DDE]

3 hours ago, ARS said:

Is it possible to reduce the G-force during reentry by making the reentry capsule outfitted with liquid breathing immersion module? So the crew is immersed in liquid to dampen the G-force, while still allowing them to breathe

A trick so old it's been featured in a 1935 movie does have a fairly comprehensive Wikipedia page:

Quote

Acceleration protection by liquid immersion is limited by the differential density of body tissues and immersion fluid, limiting the utility of this method to about 15g to 20g. Extending acceleration protection beyond 20g requires filling the lungs with fluid of density similar to water. An astronaut totally immersed in liquid, with liquid inside all body cavities, will feel little effect from extreme G forces because the forces on a liquid are distributed equally, and in all directions simultaneously. However effects will be felt because of density differences between different body tissues, so an upper acceleration limit still exists.

Liquid breathing for acceleration protection may never be practical because of the difficulty of finding a suitable breathing medium of similar density to water that is compatible with lung tissue. Perfluorocarbon fluids are twice as dense as water, hence unsuitable for this application.

 

[JoeSchmuckatelli]

1 hour ago, DDE said:

A trick so old it's been featured in a 1935 movie does have a fairly comprehensive Wikipedia page:

Perfluorocarbon fluids are twice as dense as water, hence unsuitable for this application

Dang - never knew that. Nor that they'd been thought about as g-force moderation.  I thought it was only good for meeting aliens on the sea floor! 

 

There (also) goes my solution to the manned giant battle robot Commander's Module

 

[kerbiloid]

The only thing confusing me in the sci-fi anti-g liquid beds is that the internal organs keep pressing the back from inside with same force.

[JoeSchmuckatelli]

Info on 18 Sco? 

 

I remember reading years ago that this is one of the closet Sol analog stars - getting even Margaret Turnbull excited - but I can't find much more about it. 

There was an article about its metalicity and speculation that it is too dusty for it to likely have a rocky planet in the habitable zone... But then I remember talk about excitement to see what the Webb spotted (back when it was on schedule)...

 

So I'm surprised I don't see much about it - but wouldn't it be one of the most studied stars in the recent years?  Shouldn't there be rich information from Kepler and TESS studies that are published/available to the average Joe?

 

All I see is 'no planets have been discovered' - but I haven't seen why 

[magnemoe]

On 4/29/2020 at 6:05 AM, kerbiloid said:

The only thing confusing me in the sci-fi anti-g liquid beds is that the internal organs keep pressing the back from inside with same force.

They do but its just 20 cm something. We have lots of experience on very high g load over very short term, high g load for minutes. 
None for long term high g trust and pointless to even think about before somebody make an touchship. 
At this time its pretty easy to test.