For Questions That Don't Merit Their Own Thread

[DDE]

11 minutes ago, ARS said:

Does aircraft bombs actually "whistle" when dropped from aircraft? Quite frequently, in movies and video games (especially if set on WW2 era, but sometimes extend to modern era), the bombs are depicted as whistling as it's released from aircraft until impact (most commonly during carpet bomb scene). What's the cause of that whistle?

Generally, no. That would be a sign of rather bad aerodynamic design. Some whine is inevitable, but not to the degree heard in cinematography.

However, a lot of people went for the deloberate psychological effect and welded literal whistles to bombs. And then you had whistles without bombs, dropped for the sheer intimidation purposes.

The peak of this was, apparently, Luftwaffe dropping worn-out tyres over Stalingrad. Sounded something awful.

[magnemoe]

5 hours ago, DDE said:

Generally, no. That would be a sign of rather bad aerodynamic design. Some whine is inevitable, but not to the degree heard in cinematography.

However, a lot of people went for the deloberate psychological effect and welded literal whistles to bombs. And then you had whistles without bombs, dropped for the sheer intimidation purposes.

The peak of this was, apparently, Luftwaffe dropping worn-out tyres over Stalingrad. Sounded something awful.

Once some fools starting dropping snowballs from the roof of an high rise, the snowballs had an distinctive whine coming down. Heard mortars make an whine in war reporting, especially for the mortars its something you want to avoid as people will take cover. 
However it might be hard to avoid as they are spin stabilized. 

[p1t1o]

Went on a skydiving training thing once - didnt end up doing a jump because of weather , but I did learn one thing - skydivers make quite a lot of noise.

At one point were were able to watch from the ground as a group did a freefall jump, and we could see them fall from the plane. As they fell, you could hear a quite prominent "tearing" noise that was the noise they made as the moved through the air.

Funny the things you think (or that movies make you think) are quiet. Bows, for example (as in bow-and-arrow) make quite a loud noise when shot too - like plucking an enormous guitar string.

 

 

7 hours ago, DDE said:

Generally, no. That would be a sign of rather bad aerodynamic design. Some whine is inevitable, but not to the degree heard in cinematography.

However, a lot of people went for the deloberate psychological effect and welded literal whistles to bombs. And then you had whistles without bombs, dropped for the sheer intimidation purposes.

The peak of this was, apparently, Luftwaffe dropping worn-out tyres over Stalingrad. Sounded something awful.

The well-known Ju87 Stuka famously had sirens installed on the aircraft itself, so that it made a noise whilst on its attack dive,  the so-called "Jericho-Trompete", which is a very recognisable sound from WWII movies. This has led to another movie-trope where any diving aircraft in any context would make an ascending siren-like wail.

[JoeSchmuckatelli]

4 hours ago, p1t1o said:

Went on a skydiving training thing once - didnt end up doing a jump because of weather , but I did learn one thing - skydivers make quite a lot of noise.

At one point were were able to watch from the ground as a group did a freefall jump, and we could see them fall from the plane. As they fell, you could hear a quite prominent "tearing" noise that was the noise they made as the moved through the air.

Funny the things you think (or that movies make you think) are quiet. Bows, for example (as in bow-and-arrow) make quite a loud noise when shot too - like plucking an enormous guitar string.

 

...

I had a completely different experience during my first jump - a seminal memory that I will never forget. 

Standing in the door of a C-141, wearing the cotton camouflaged uniform of the day, combat boots and a regulation issued kevlar helmet, I marveled at how loud a plane is.  The constant whine of the engines combined with the massive white-noise of the wind rushing past the door at 130 kts to create an almost physical sensation of sound felt in the bones as much as heard.  The shouts of the jump master and mutters of novice jumpers cracking wise or praying to whatever deity might be listening was a completely secondary event.  You literally had to force the mind to focus on applying meaning to words.  The physical reality of a heart beating in your chest and the wall of wind begging you to step into the void was much more visceral.

I had my hands on the bulkheads forming the hatch, my boot toe in the wind and I kept leaning into the doorway to look forward in anticipation of seeing the drop zone from 2500 feet.  Having only ever seen the ground from the tiny windows of commercial aircraft, standing in an open a door to the world at that altitude was a heady experience.  I never knew, until that moment, that planes don't turn... they slide through the air.  It's not at all like how your hands move when you're mimicking Mav and Goose: the wings tilt and the momentum carries the plane forward as the wings bite the wind and the plane slides into its turn.  The jump master roughly pulled me back twice, afraid the wind would snatch me from the door over the woods I wasn't trained or ready to land in.  I kept grinning toothily at her; a tough little staff sergeant easily a foot shorter and 100 pounds lighter than my 230 six-foot-seven twenty-one year old self.  She had no fear of the goofy, over eager corporal whose life she was trying to save.  She'd yell something at me that I couldn't hear - but which needed no words to understand: quit being a dumbass.  Until that light turned green, she was in charge.  After that... I was on my own.

Unlike civilian jumpers - especially those going for tandem jumps - we'd had weeks of training to get to this point.  I'd trained on what to do in the seconds after leaping from the plane to create a muscle memory I can still do step-by-step thirty years later.  I knew everything I was supposed to do from the moment I strapped on the bag, through waiting for the command to GO! and to not move when someone commanded us to "Check Can Of Peas!"  The only thing I hadn't done was actually do it for real.

I felt her slap my shoulder and was out the door before she felt the sting on her palm.

 

 

 

 

 

 

Silence.

 

 

 

 

 

It was strikingly peaceful staring past my toes at the tail of the plane as it eased itself out of my view.  Another insight; when I stepped from the plane, it and I were going 130 kts together.  It, however was still accelerating and I wasn't.  There was no movie-like snatch of air and fast-fade.  The tail just calmly left the frame of view I had locked on my hands and tightly clamped knees and polished black boots.  The only 'sound' was my counting in my head and waiting for the risers to snatch me back to reality.  I had time to realize that if I could see the tail of the plane past my boots that I was upside down.  It was a curious realization.

The physical relief of the risers snapping past my ear and my feet being flipped earthward was a ripping sound that only briefly interrupted the silence.  The chute foomped and flapped a bit as it filled, and then everything was quiet again.  I could hear conversations on the ground below me - much like balloonists report about flying over golf courses.  

I had this amazing, overwhelming sense of freedom, peace and control.  Far from merely falling, I was flying.  I played with climbing the risers of the T-10 Charlie to make the chute go where I wanted to.  It worked! 

And then, all too soon, the trees stopped being weird shrub-like top-down and unreal; they took on an abrupt reality as I passed into an altitude that my monkey brain recognized as dangerously high (before that, the brain doesn't ascribe much meaning to what you're seeing - its too foreign).  The moment the trees 'become real' is also visceral; you've got mere seconds to get your head out of the clouds and remember everything you need to do to not break yourself as you slam into the ground like a sack of potatoes.  Feet and knees together, eyes on the horizon and WHUMP and FLAP and...

You're alive!

 

...

 

So this opus aside: what you hear when you watch civilian jumpers is a product of their using 'flappy' suits to help slow and control their free-fall descent.  It's not always a feature of jumping.  I'll never forget the abrupt silence and the freedom and control you feel when its just you, a nylon bag and the world.

 

Hope you get a chance to jump!  It's something you will never forget.

Edited July 17, 2020 by JoeSchmuckatelli

[JoeSchmuckatelli]

3 hours ago, magnemoe said:

Once some fools starting dropping snowballs from the roof of an high rise, the snowballs had an distinctive whine coming down. Heard mortars make an whine in war reporting, especially for the mortars its something you want to avoid as people will take cover. 
However it might be hard to avoid as they are spin stabilized. 

I've never heard modern mortars make any sound before they impact.  In the old days, starting with the Germans in WWII some combatants put whistles on their bombs (and perhaps mortars) as a psychological weapon.  https://www.scienceabc.com/eyeopeners/why-do-bombs-make-a-whistling-sound-when-they-fall.html  But all of the mortars (small and large) and artillery that I've fired or had land near me in the modern era don't have this 'feature'.

I spent one highly intense day getting shelled by a variety of mortars and artillery from dawn to dusk, followed by several days of intermittent shelling.  We never heard them 'coming in' until they were exploding around us.  That's being close enough to feel the heat and concussion, taste and smell the mud and explosives and smoke and get mud in the face.  In other words close enough that pure luck is the only reason I'm around to write this.

So... today... the whistling sound?  it's just a movie trope.

Edited July 17, 2020 by JoeSchmuckatelli

[StrandedonEarth]

30 minutes ago, JoeSchmuckatelli said:

what you hear when you watch civilian jumpers is a product of their using 'flappy' suits

Yup, that’s what I was gonna say. I wonder if naked skydivers make a sound as various body parts flap....

The one static line jump I did: for those few seconds between letting go of the plane and the chute opening, my mind was completely, utterly blank.  

[JoeSchmuckatelli]

1 minute ago, StrandedonEarth said:

...: for those few seconds between letting go of the plane and the chute opening, my mind was completely, utterly blank.  

There's a real peace in those moments when the mind isn't constantly racing.  Rare and precious.

[JoeSchmuckatelli]

Time for a new question:

 

If we were to put a satellite in a circular orbit outside of the moon's orbit... To be stable and circular - would the satellite actually orbit the earth, or would the center of the orbit be the axis of the earth /moon co-orbit? 

[DDE]

1 hour ago, JoeSchmuckatelli said:

Time for a new question:

 

If we were to put a satellite in a circular orbit outside of the moon's orbit... To be stable and circular - would the satellite actually orbit the earth, or would the center of the orbit be the axis of the earth /moon co-orbit? 

Not ready to comment on the pertrubations... But it would orbit the Moon-Earth barycenter, which is still within Earth's radius.

[JoeSchmuckatelli]

8 minutes ago, DDE said:

Not ready to comment on the pertrubations... But it would orbit the Moon-Earth barycenter, which is still within Earth's radius.

Barycenter - that's the word I could not remember! 

 

Does that also ring true for satellites inside the moon's orbit? 

[magnemoe]

4 hours ago, JoeSchmuckatelli said:

Time for a new question:

 

If we were to put a satellite in a circular orbit outside of the moon's orbit... To be stable and circular - would the satellite actually orbit the earth, or would the center of the orbit be the axis of the earth /moon co-orbit? 

This is possible, you have some asteroids who is quasi moons of earth.
https://en.wikipedia.org/wiki/Claimed_moons_of_Earth#Quasi-satellites_and_trojans
As seen the orbit is not quite circular seen from earth. 
This should also be possible Earth Moon however it would need course corrections over time. 

[kerbiloid]

On 7/15/2020 at 12:26 PM, DDE said:

But, judging from SK-2, no-one else thought it was a good idea:

Isn't this something like that? It crossed Atlantics.

https://en.wikipedia.org/wiki/Spirit_of_St._Louis

Spoiler

 

On 7/17/2020 at 9:13 AM, ARS said:

Does aircraft bombs actually "whistle" when dropped from aircraft?

The whistling  means air dragging.

The smoother the shell is - the quieter it sounds.

Afair, the Ju-87 sirens were first of all to keep the proper speed and altitude by ears while diving, when widely opened from fear and full of blood, mad eyes of the pilot are staring at the approaching ground.

Edited July 21, 2020 by kerbiloid

[magnemoe]

On 7/15/2020 at 11:26 AM, DDE said:

The pilot was supposed to be lifted upwards along with some portion if the canopy for landing. The aircraft proved flyable... But, judging from SK-2, no-one else thought it was a good idea:

However, there are ways. Aside from Sukhoi T-4 where the drooping nose would reveal the windshield for landings,

two-seat MiGs have periscopes.

Are this so the guy in the back seat can land the plane in an emergency? 
The Sukhoi T-4 was kind of genial
 

[DDE]

23 minutes ago, magnemoe said:

Are this so the guy in the back seat can land the plane in an emergency? 

"Emergencies" can be disturbingly frequent on training aircraft, which the upper MiG is. Not too sure about MiG-31, where the guy in the back is a RIO, not a co-pilot.

[p1t1o]

25 minutes ago, magnemoe said:

The Sukhoi T-4 was kind of genial
 

T4 is one of my faves, with the nose up its lines are unlike anything else.

And I especially like how the windscreen, with the nose down, looks like it was ripped straight from a Diesel train locomotive. Very Russian.

[ARS]

What's the typical minimum range of ICBM missiles? For a weapon designed to deliver nukes to other continents, what's the minimum range where it absolutely cannot be fired because it's considered "too close" (for a weapon with this kind of range, the "close" could mean thousands of kilometers away right?)

[SuperFastJellyfish]

43 minutes ago, ARS said:

What's the typical minimum range of ICBM missiles? For a weapon designed to deliver nukes to other continents, what's the minimum range where it absolutely cannot be fired because it's considered "too close" (for a weapon with this kind of range, the "close" could mean thousands of kilometers away right?)

 

From the almighty wiki:

Quote

An intercontinental ballistic missile (ICBM) is a guided ballistic missile with a minimum range of 5,500 kilometres (3,400 mi)^[1] primarily designed for nuclear weapons delivery (delivering one or more thermonuclear warheads).

 

It has a hard minimum because there are different classifications of ballistic missiles:

Quote

ICBMs are differentiated by having greater range and speed than other ballistic missiles: intermediate-range ballistic missiles (IRBMs), medium-range ballistic missiles (MRBMs), short-range ballistic missiles (SRBMs) and tactical ballistic missiles (TBMs). Short and medium-range ballistic missiles are known collectively as theatre ballistic missiles.

 

[SOXBLOX]

CLASSIFIED*

But seriously, with a liquid fuelled missile, you can just shut down the engine. However, with solids (Minuteman, Peacekeeper, GBSD, etc.) you have to fine tune the trajectory. You could probably do away with any third stage, as well.

***

Also, not a hard minimum. The missile would still be an ICBM, because though it has that range, it just isn't used in this scenario.

Edited July 23, 2020 by SOXBLOX

[K^2]

1 hour ago, SuperFastJellyfish said:

It has a hard minimum because there are different classifications of ballistic missiles:

Pity. I was considering traveling to Panama and claiming that my shoe is an ICBM.

[DDE]

4 hours ago, SuperFastJellyfish said:

From the almighty wiki:

It has a hard minimum because there are different classifications of ballistic missiles:

This isn't the minimum range in the sense of the OP, but the minimum maximum range for a land-based misisile to be considered an ICBM under New START (it's the distance between Sakhalin and Alaska). The late Intermediate Nuclear Forces treaty banned everything land-based with maximum ranges of 500 to 5500 km (ship-based Tomahawks and Kalibrs were a-OK, so cue swarms of Russian Kalibr gunboats like the Buyan-M that are now conceptually obsolete) and then there's MCTR that almost completely bans international sales of missiles (or armed drones) with a range of above 300 km (which is why we're going to see fireworks next year when Russia becomes the chair of the MCTR oversight body just as America tries to craft exceptions for drones... while also likely failing to extend New START. RIP arms control.)

As an example of the above definitions in action, consider RS-26 Rubezh - a Yars minus a stage, with a maximum range of 6000 km, basically a 'Eurostrategic' IRBM that just barely scraped through the existing arms control network.

5 hours ago, ARS said:

What's the typical minimum range of ICBM missiles? For a weapon designed to deliver nukes to other continents, what's the minimum range where it absolutely cannot be fired because it's considered "too close" (for a weapon with this kind of range, the "close" could mean thousands of kilometers away right?)

Well, there are several answers based on how you go about launching them. The cheeky response is that Topol/Yars and Satan/Sarmat have a minimum range of 0 m: if the main engine fails after the gas generator ejects them from the launch container, it just falls back (and explodes).

You can always launch the missile vertically while compensating for the Coriolis effect for an effecfive range of 0 m - the Peenemünde guys did that a lot, but I have doubts about modern MIRVs surviving such a harsh descent.

The proper answer to your question is difficult because it involves what's called a depressed trajectory, with a lower apex than normal and more time spent in an atmosphere. Yeah, that costs range, but it also gets the weapon to the target much, much faster while complicating intercept. Hence related capabilities and flight dynamics are spoken of in hushed tones.

And at some point you get into the realm of short-ranged 'quasiballistic' missiles that neither cross the Karman line nor fly unguided for any significant length of time.

Edited July 23, 2020 by DDE

[kerbiloid]

At last, only the flight range is limited by the treaty.

Nothing prohibits using ICBM as a wheeled ram.

Edited July 23, 2020 by kerbiloid

[p1t1o]

I mean, any missile can be detonated on the launchpad for a range of 0m, or rolled down a hill for a range of several tens of metres, but more realistically:

There are ways to manage the energy provided by a solid booster, and methods to shut them off before total burn-out have been devised, but as it happens, minimum range of an ICBM is decided largely by structural integrity.

Google "depressed trajectory".

This is a tactic whereby a submarine would park close to the target and launch its SLBMs on a shallow trajectory, reducing flight time to very low (for ICBMs) values. This allows various tactical options, as you could imagine for short time-of-flight weapons. Decapitation strikes for example, or the more extreme "pop off nukes in a steady stream over their ICBM fields to prevent their launch (or nuking the silos again and again to guarantee destruction of very hard targets) until you have nuked their entire country into dust", as well as simply reducing the time for defences to react - especially as this type of trajectory also makes them largely immune to exo-atmospheric intercept and vastly reduces the time available for endo-atmospheric interception.

The problem here is that ICBMs are designed for maximum range with maximum payload, and thus are designed to withstand the forces of that kind of flight - ie: suborbital ballistic flight through vacuum with a short boost phase and minimal atmospheric flight.

Shorter ranges require the weapon to fly for much longer through the atmosphere and are also required to perform much harder (for an ICBM) manouvres. This means that the weapon must be strong enough to resist increased atmospheric heating and drag in the boost as well as stronger transverse aerodynamic forces. The more robust the weapon, the shallower trajectory it can fly, and thus the shorter range it can be reliably targetted.

Thus, minimum range is largely decided by structural integrity.

Further reading:

http://www.scienceandglobalsecurity.org/archive/sgs03gronlund.pdf

 

Edited July 23, 2020 by p1t1o

[kerbiloid]

5 hours ago, DDE said:

And at some point you get into the realm of short-ranged 'quasiballistic' missiles that neither cross the Karman line nor fly unguided for any significant length of time.

BDArmory Modular Missiles.

[DDE]

3 hours ago, p1t1o said:

Google "depressed trajectory".

Next step up from there is boost-glide, a.k.a. 'unmotorized hypersonics'.

[kerbiloid]

A minute of fizzix

http://scienceandglobalsecurity.org/archive/sgs23acton.pdf

(with pictures)

Edited July 23, 2020 by kerbiloid