For Questions That Don't Merit Their Own Thread

[kerbiloid]

2 hours ago, magnemoe said:

this would be an serious issue with an machinegun. 

Unless you have a jetpack.

Spoiler

P.S.
Say, 250 rounds * 8 g * 800 m/s / 120 kg ~= 14 m/s of delta-V.

P.P.S.
Of course the jetpack should be hypergolic, not compressed nitrogen or CO2.

P.P.P.S.
If this is not a translator's misheard lyrics, in Expanse the drapersuit is powered with hydrazine.

Edited May 28, 2018 by kerbiloid

[winged]

What is the height and width limit for rockets built in the KSC?

[kerbiloid]

1 hour ago, winged said:

What is the height and width limit for rockets built in the KSC?

Physical range is ~2 km in every direction by default.

(Can be changed by some mods).

Also such large objects can suddenly visually appear/disappear when you approach of leave them.
Both huge static towers created with KerbalKonstructs, and huge orbital ships like that single-part Stanford Torus.

Edited May 28, 2018 by kerbiloid

[winged]

1 minute ago, kerbiloid said:

Physical range is ~2 km in every direction by default.

(Can be changed by some mods).

I mean the real VAB located in Florida

[magnemoe]

13 hours ago, kerbiloid said:

Unless you have a jetpack.

  Reveal hidden contents

P.S.
Say, 250 rounds * 8 g * 800 m/s / 120 kg ~= 14 m/s of delta-V.

P.P.S.
Of course the jetpack should be hypergolic, not compressed nitrogen or CO2.

P.P.P.S.
If this is not a translator's misheard lyrics, in Expanse the drapersuit is powered with hydrazine.

You have to add the weight of the powder too, not sure how huge an faction that would add, average speed would be slower to. 
However main issue is rotation this would also be way more annoying, yes you can compensate with an jetpack but it would still shake a lot i think

And why did they not use one of the newer cleaner monoprop? Way safer to handle. 

[kerbiloid]

1 hour ago, magnemoe said:

You have to add the weight of the powder too

~3..4 g.At least a half of it, vice versa, pushes the gun back, then slowly flows away. So, the powder effect is negligible.

1 hour ago, magnemoe said:

However main issue is rotation this would also be way more annoying, yes you can compensate with an jetpack but it would still shake a lot i think

Jetpack anyway should have RCS nozzles.

Say, 2 miniguns x 14 m/s, i.e. 30 m/s of additional speed in total.
Say, 10 bursts/second. I.e. 250/10 = 25 seconds of fire.
Average acceleration = 30/ 25 ~1.2 m/s².
Average force (max value) = 1.2 * 120 = 144 N.

So, the gunner needs 4 nozzles ~100 N each.

If use hydrazine (exhaust speed ~2200 m/s), dm = 120 * (exp(30/2200) - 1) = 1.7 kg
Plus several kg of hydrazine instead of powder (so, using bullets instead of shells).

So, ~10 kg of hydrazine and bullets per 500 rounds.

1 hour ago, magnemoe said:

but it would still shake a lot i think

It's a minigun, not a marksman rifle.

And that's why AK-74 has such thing on the nose.

Spoiler

 

1 hour ago, magnemoe said:

And why did they not use one of the newer cleaner monoprop? Way safer to handle. 

They will, if they pay.

[p1t1o]

On 5/28/2018 at 5:06 AM, ARS said:

What's the (supposed) actual advantage of gyrojet rounds compared to normal cartridge rounds? Seeing as the actual gyrojet weapon has inadequate performance (bullet starts slow and then accelerates, bullet veering off course, bad accuracy at long range but bad power at short range (it won't even harm the finger placed directly at gun barrel)). Does it even make a good weapon to substitute normal cartridge rounds?

I've read a few relevant facts on this:

The gyrojet was rare but found use in Vietnam, where it was praised for its unusual sound signature ("ZWIP", apparently ),  which when heard, did not necessarily originate from the firing position but from the path of the bullet - making the position of the shooter harder to pinpoint - which was a huge advantage in jungle warfare, meaning it was generally liked by those who used it.

It was very light compared to conventional firearms due to not needing heavy barrel construction.

Stopping power was low at short range but significant speed is reached within 10m, maximum speed (roughly Mach1, no exact data) reached in 20m after propellant burn-out. Propellant burn time is approx 0.1-0.12s

The only manufacturing run on ammunition had a defect in one of the rocket nozzles (4 small holes in the base, canted to impart spin stability) which damaged power and accuracy. The defect was never corrected as the weapon did not catch on. It can be assumed that a fully developed weapon would be more effective and less failure prone.

The firing mechanism was unique. The hammer hit the bullet from the front, forcing the round to hit the fixed firing pin at the rear. The rocket would then push through the sprung hammer, re-cocking it. Due to the above mentioned ammo defects, sometimes the rocket would not be able to pass the hammer, causing a misfire.

Edited May 29, 2018 by p1t1o

[kerbiloid]

41 minutes ago, p1t1o said:

rocket nozzles (4 small holes in the base

 

41 minutes ago, p1t1o said:

The hammer hit the bullet from the front, forcing the round to hit the fixed firing pin at the rear. The rocket would then push through the sprung hammer, re-cocking it

This construction makes to remember some aspects of late 1960s culture, besides sex and rock-n-roll...

[magnemoe]

2 hours ago, p1t1o said:

I've read a few relevant facts on this:

The gyrojet was rare but found use in Vietnam, where it was praised for its unusual sound signature ("ZWIP", apparently ),  which when heard, did not necessarily originate from the firing position but from the path of the bullet - making the position of the shooter harder to pinpoint - which was a huge advantage in jungle warfare, meaning it was generally liked by those who used it.

It was very light compared to conventional firearms due to not needing heavy barrel construction.

Stopping power was low at short range but significant speed is reached within 10m, maximum speed (roughly Mach1, no exact data) reached in 20m after propellant burn-out. Propellant burn time is approx 0.1-0.12s

The only manufacturing run on ammunition had a defect in one of the rocket nozzles (4 small holes in the base, canted to impart spin stability) which damaged power and accuracy. The defect was never corrected as the weapon did not catch on. It can be assumed that a fully developed weapon would be more effective and less failure prone.

The firing mechanism was unique. The hammer hit the bullet from the front, forcing the round to hit the fixed firing pin at the rear. The rocket would then push through the sprung hammer, re-cocking it. Due to the above mentioned ammo defects, sometimes the rocket would not be able to pass the hammer, causing a misfire.

Yes, it would be an very silent round, you would get the smoke and fire from rocket, but with burnout after 20 meter it would not be much worse than the muzzle flash.
You are right about the ammunisjon defect 
The low exit speed would make it very sensible to wind or moving the gun while firing. More an issue is that pistols are self defense weapons and primarily used at close range. 

Brings me back to the grenade launcher use

this looks a lot like an gyrojet bullet in that the bullet contains the propellant with holes for it to escape, however this burn out in the barrel. 
Having it continue to burn would let you get lower recoil and higher speed. The heavy bullet would be less affected by wind and its not supposed to be used at close range anyway. 
Have it only arm after burnout would be an simple way to arm the grenade at an safe distance. 
The larger bullet would also make it easier to make the engine,
Guess the rocket flame would be so much larger it would be an problem. 

 

 

[sevenperforce]

I once played around at great length with a gyrojet-styled bullet. Differences were ring fin stabilization in place of spin-stabilization, a pressure-bearing (albeit short) barrel to fix the low muzzle velocity, and caseless propellant. Would have had ridiculously good performance. Would also have been ridiculously expensive.

[p1t1o]

There's been some interesting work done on ramjet-powered projectiles:

[kerbiloid]

2 hours ago, p1t1o said:

There's been some interesting work done on ramjet-powered projectiles:

Afaik they are not really jet-powered, but have jets which fill the vacuum behind the flying supersonic shell with exhaust gases to decrease drag.

 

2 hours ago, sevenperforce said:

I once played around at great length with a gyrojet-styled bullet. Differences were ring fin stabilization in place of spin-stabilization, a pressure-bearing (albeit short) barrel to fix the low muzzle velocity, and caseless propellant.

At last they did it.

Spoiler

 

Edited May 29, 2018 by kerbiloid

[magnemoe]

10 minutes ago, kerbiloid said:

Afaik they are not really jet-powered, but have jets which fill the vacuum behind the flying supersonic shell with exhaust gases to decrease drag.

 

At last they did it.

  Hide contents

 

So the same as base bleed in practice, thought it would be smarter to have the intake in the rear, you don't need so much air and it would simplify the design a lot.

As for rocket arrows, scale it up 200 times for more fun. Yes the external mounted rockets would generate a lot of drag still using multiple of these would have an impact. 

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

 

[kerbiloid]

16 minutes ago, magnemoe said:

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

They fly.

Spoiler

 

But watching the video I had a strong feeling that an enemy soldier would be staying right in front of it to get a hit.
Did at least one arrow stick into the ground?

They would better use this powder and arrow tips to make a trivial canister shot.

Edited May 29, 2018 by kerbiloid

[magnemoe]

38 minutes ago, kerbiloid said:

They fly.

  Hide contents

 

But watching the video I had a strong feeling that an enemy soldier would be staying right in front of it to get a hit.
Did at least one arrow stick into the ground?

They would better use this powder and arrow tips to make a trivial canister shot.

They did not have good cannons yet, neither good canisters, filling the cannon with scrap was the best option and that only worked on very close range.
Now I would obviously scale the rockets up and use an iron casing around the exploding warhead, did not know they was explosive, thought they was just arrows. 
with an fragmentation warhead they would be devastating.

Armies before the US civil war stayed in thigh formations to defend against cavalry and you wanted it during melee as you would protect each other. 

During the civil war they had rifles capable of hitting at longer range so you had to stay in the kill zone longer, you got exploding cannon balls who was an effective area effect weapon, like this rockets would be with fragmentation warheads granted less accurate but easier to fire in large groups. 
Followed by breach-loaded rifles with an far higher rate of fire 

Also rockets has an nice advantage over cannons, the launcher is very simple so its easy to shoot huge salvos, downside is that the projectile is more complex and more bulky so you don't want to use them if you don't want an large salvo.
Today they also has longer range so all serious powers outside of Russia has replaced cannons larger than 155 mm with rockets, the cannon get to large to be easy to move around. 

[kerbiloid]

8 minutes ago, magnemoe said:

Now I would obviously scale the rockets up and use an iron casing around the exploding warhead

Which would highly likely lead to the whole thing explosion once a single rocket gets sticked inside the barrel for seconds or falls right in front of it.

_{I would try a canister diagonal cross-fire from flanks, then immediate front attack on the broken formation.}

14 minutes ago, magnemoe said:

Armies before the US civil war stayed in thigh formations to defend against cavalry and you wanted it during melee as you would protect each other. 

Afaik thigh formation have been discredited in Crimea War (1850s), US generals were just fond of traditions.

19 minutes ago, magnemoe said:

this rockets would be with fragmentation warheads

If a thick cannonball falls down, its fuse keeps burning, then it explodes.

If a big hollow pipe falls down, it would mostly likely break apart. If it's made of bad iron, it will either explode or fly away for several meters and fall.
Don't forget that steel melting became available just in XVIII or so century in Europe.

26 minutes ago, magnemoe said:

Today they also has longer range so all serious powers outside of Russia has replaced cannons larger than 155 mm with rockets, the cannon get to large to be easy to move around. 

Guided cluster rockets, not unguided old ones.

[magnemoe]

21 minutes ago, kerbiloid said:

Which would highly likely lead to the whole thing explosion once a single rocket gets sticked inside the barrel for seconds or falls right in front of it.

_{I would try a canister diagonal cross-fire from flanks, then immediate front attack on the broken formation.}

Afaik thigh formation have been discredited in Crimea War (1850s), US generals were just fond of traditions.

If a thick cannonball falls down, its fuse keeps burning, then it explodes.

If a big hollow pipe falls down, it would mostly likely break apart. If it's made of bad iron, it will either explode or fly away for several meters and fall.
Don't forget that steel melting became available just in XVIII or so century in Europe.

Guided cluster rockets, not unguided old ones.

With scaling up I thought 70-90 mm rather than 40 not anything larger because of accuracy and it would be ground burst. 
Think an rocket is slower on impact and you have the front as an crumble zone, also an cannon ball with an time fuse has the issue with hitting something hard with fuse part. 
Ok 15 years earlier , back then military strategy was not seen as dynamic but static, this was before the technology race with ironclads. 
Think you could do well with cast iron again cannon balls with no crumble zones, probably easier to make an impact fuse then you know the part impacting. 

And yes long range rockets is obvious PGM, they do not need to be pgm if fired in the thousands in short artillery range 

[Racescort666]

1 hour ago, magnemoe said:

Today they also has longer range so all serious powers outside of Russia has replaced cannons larger than 155 mm with rockets, the cannon get to large to be easy to move around. 

Big guns have seen action as recently as 1991 so I'd say that they probably have some utility over missiles.

[magnemoe]

29 minutes ago, Racescort666 said:

Big guns have seen action as recently as 1991 so I'd say that they probably have some utility over missiles.

I know Sea has an benefit in that you can easy carry 10 times the load you can do on land without any issue,  
And yes you remember if getting shelled by an battleship. 
Downside of battleships is that the designed during WW2 required an huge crew, this was not an issue during conscription in ww2, it was an issue then you have to pay 2000 seamen to crew it and all have high salaries.

[Spaceception]

So sorry in advance if this is a stupid question, I've just not seen it addressed, and I'm wondering what the answer is.
But we hear a lot regarding Interstellar travel as being dangerous because of the risk of hitting molecules and dust particles at even small fractions of c, and because of the kinetic energy in the ship, it can hit the speck with the force of an atomic bomb.

So my question is, could you hit enough of these specks that your velocity would be significantly reduced (And, affect your travel time by a few years), or is it rare enough that they're basically mild hindrances? I got the idea for this question after thinking of Orion, and how it uses Nuclear bombs to propel it; and how these specks would behave in a similar way, but in reverse. I'm not sure how answerable this is though, considering we don't know a whole lot about the Interstellar medium.

Edited May 31, 2018 by Spaceception

[Lisias]

46 minutes ago, Spaceception said:

So my question is, could you hit enough of these specks that your velocity would be significantly reduced (And, affect your travel time by a few years), or is it rare enough that they're basically mild hindrances? 

It's a statistical certain : given enough time, it's sure that this will happen. Assuming that you have mass enough in your shields (or energy enough for electromagnetic ones) and doesn't gets obliterated in the process.

Preventing such particles to traversal your ship (and you) are way more concerning that speed. The time that our Solar System took to form the first planets may hint us about the time needed.

Given our lifespan (hell, given a comet's lifespan! :-) ), it's merely a hazard - something that must be mitigated somehow - as calculating the mean density of particles of the measurable Universe and given the mass of the vessel and her exposure area, figure out how many hits to sustain. And pray for the mathematician's accuracy for the whole trip. :-)

 

[kerbiloid]

1 hour ago, Spaceception said:

could you hit enough of these specks that your velocity would be significantly reduced

Theoretically yes, but this bombardment will vaporize the ship before it stops.
And as it will be vaporizing from the front end, the jet of ablation will be slowing the ship additionally.

But this is not a problem, too, because the crew and command systems will get lethal dose earlier.

Also, avoid the molecular clouds. According to wiki, they are several orders of magnitude denser than just interstellar gas. Like hit a concrete brick moving throw air.

***

And two words about the optimistic Alcubierre drive.

https://www.quora.com/What-are-the-flaws-of-the-Alcubierre-drive-concept

 

Edited May 31, 2018 by kerbiloid

[p1t1o]

12 hours ago, kerbiloid said:

And two words about the optimistic Alcubierre drive.

https://www.quora.com/What-are-the-flaws-of-the-Alcubierre-drive-concept

Freaking heck FINALLY someone has come out and said it!

"Yeah of course we can go faster than light, we already know how, all you need is a warp drive" AUGH!

[kerbiloid]

9 minutes ago, p1t1o said:

Freaking heck FINALLY someone has come out and said it!

To be accurate, RainDreamer appears to be the first.

 

Edited June 1, 2018 by kerbiloid

[ARS]

Does a laser gun (which purely shoots energy, either continuous stream or pew pew pew variety) is supposed to have recoil? Does a laser gun even need barrel?