Back Emergency to Slow down

[drhyed]

So when Your going across the Big map moving to mission areas and run into an unexpected enemy at 20 knots it takes a bit of time to slow down and for the sensors/sonar to work. I can slow down in a hurry by going to back emergency, I been on boats where this has been done and it makes big wakes, disturbances, and air bubbles. Anyone know if Im setting off signal flairs and laying out the welcome mat for the Russians doing this? With the new update I am still doing alright with subs but surface encounters are still giving me trouble so its hard to tell, I dont get cavitation warnings, anyone know?

Thanks
Jay

[THEBERBSTER]

A Warm Welcome To The Subsim Community > drhyed
Subsim <> Make A Donation <> See The Benefits <> Support The Community (http://www.subsim.com/radioroom/showpost.php?p=2027002&postcount=1)

[Killerfish Games]

You're not giving away yourself. You are rapidly decelerating so your flow noise and engine noise will decrease quickly.

[Capt.Hunt]

I'm sure one of our resident submariners could give us a definitive answer, but you'd think going all back emergency would make a heck of a racket. After all, the screw is only optimized to turn one way, and the pumps would probably shift to high speed.

[ET2SN]

I guess it depends. :hmmm:
Real world, its not like you're shifting gears from the helm.
All you're doing is turning the dial on the announceator which makes the pointer move on a similar dial back in Maneuvering.
Its up to the throttleman to see the new order and turn the "big wheel" to drive the screw, just like when you give a spoken order to "make turns for X knots".

So, I guess you can assume that you have a sharp throttleman back aft who knows you want to slow down fast. :D

[drhyed]

In thinking about it more the screw is attached to a electric motor and with an electric motor you can use induction to instantly reverse the polarity, which then works like a giant brake on the motor at the expense of heat generation ( I think? going off of my very limited knowledge of how trains work and driving a Prius :up: ) just flip the switch on the side of a ceiling fan when its spinning on high to see what Im referencing, now image if your ceiling fan blades were in water, consider how quickly they would slow down. Im sure with some testing at a place like the The Navy's Acoustic Research Detachment in Idaho they could work out a chart which got me down below 10 knots with the best risk vs reward for noise crated vs the disturbance I made in the water. Of course it would probably be contained in a chart with a million curves and lines for each 25 feet of depth and each 2 knots of speed I was going and require the use of a slide rule to decipher but thats part of reward of being a sub captain!

[Bubblehead Nuke]

I'm sure one of our resident submariners could give us a definitive answer, but you'd think going all back emergency would make a heck of a racket. After all, the screw is only optimized to turn one way, and the pumps would probably shift to high speed.

Yes.. it makes one HELL OF A LOT OF NOISE. HUGE "HERE I AM" TRANSIENT NOISES.

In reality you slam the forward throttle closed and open the astern throttle rapidly without regard to cavitation. You do not shift pumps unless ordered. You will answer the bell to the maximum limit of the current plant lineup.

This spins the screw in the opposite direction creating HUGE amounts of cavitation. The idea is that you are gonna hit something anyway and you can at least try to cut down on the damage done in the collision.

While I am on this tangent, if you want to slow down you ring up all stop. The boat will continue in the water but the screw will act as a brake. It is still turning but the drag of the water will slow the boat down. Think of it as coasting in a car. Drag will slow you down. You never, NEVER, NEVER open the astern throttles unless you are in an emergency, docking, or are in restricted maneuvering operation.

But hey.. its a game.

[ET2SN]

But hey.. its a game.


It sounds like we're both talking about "Crash Backs". :D

I had a buddy who was standing throttleman watch after we finally got good old Ustafish out of a long overhaul.
Our skipper had been talking about doing crash back drills so up in Control it wasn't that big of a surprise when the OOD ordered a backing bell while we were cruising along.
I guess the skipper didn't like the reaction time (putting it mildly) and he set a speed record sprinting from Control to Manuvering. :timeout:

Allegedly, our skipper took control of the throttles manually while he chewed out my bud and the RO. :timeout:

Now, anyone who ever stood watch back aft or made it through quals in general can say, "Hey, that part of the story IS REALLY MESSED UP!!" and you would be right. :yeah:

Getting back on topic, yeah you could order a backing bell IRL if the situation is dire enough but we're talking about a game where the whole point is to beat the Devs. :haha:

[Bubblehead Nuke]

It sounds like we're both talking about "Crash Backs". :D

I had a buddy who was standing throttleman watch after we finally got good old Ustafish out of a long overhaul.
Our skipper had been talking about doing crash back drills so up in Control it wasn't that big of a surprise when the OOD ordered a backing bell while we were cruising along.
I guess the skipper didn't like the reaction time (putting it mildly) and he set a speed record sprinting from Control to Manuvering. :timeout:

Allegedly, our skipper took control of the throttles manually while he chewed out my bud and the RO. :timeout:

Now, anyone who ever stood watch back aft or made it through quals in general can say, "Hey, that part of the story IS REALLY MESSED UP!!" and you would be right. :yeah:

Getting back on topic, yeah you could order a backing bell IRL if the situation is dire enough but we're talking about a game where the whole point is to beat the Devs. :haha:

Beat the devs.. yeah... that is a good way to put it. If we could make this game even 40% consistent with actual ops people would lose their minds.

To give more detail for those who are wondering:

There are two sets of throttle. One controls spinning the screw in ONE direction, one turns it the other direction.

I can not go into the physical plant layout but I can tell you this with 100% certainty. You do not EVER open the astern throttles to slow down. The ONLY time they are opened is to spin the screw in the opposite direction.

As an aside. If you are streaming the tail and you answer a backing bell then you can with almost 100% certainty loose the tail. Bad day in the sonar shack.

[ET2SN]

Well, to go even deeper- :D

The OP mentioned electric motors as a kind of justification but even that is shaky.
My first boat was the Barbel. Three standard navy diesels that turned generators which fed the battery wells which then fed two large electric motors coupled to a common shaft. No reduction gears and you still wouldn't want to just chuck it into reverse. :o

The best way to torture an electric motor is to do what's known as a Blocked Rotor Test. The motor sees the maximum possible amperage load and if the windings, cables, and brushes don't burn or blow up- you've got a good motor. :up:
Now imagine the stress of reversing the field while the motor is running near its rated speed (at some point you'll also block the rotor for a couple of seconds). :o

[Bubblehead Nuke]

Well, to go even deeper- :D
Now imagine the stress of reversing the field while the motor is running near its rated speed (at some point you'll also block the rotor for a couple of seconds). :o

Add the additional force of the screw as it is moving through the water thus making want to continue to spin in the same direction. You are adding to even MORE counter torque than just stopping the shaft and reversing it. Take your blocked rotor test and double the amount of stress due to counter electric motive force.

[Capt Jack Harkness]

In thinking about it more the screw is attached to a electric motor...
Not in any of the US boats we have in game. In most nukes the prop is spun by the turbines through the reduction gear. Or directly in the case of Narwhal.

There are two sets of throttle. One controls spinning the screw in ONE direction, one turns it the other direction.

I can not go into the physical plant layout but I can tell you this with 100% certainty. You do not EVER open the astern throttles to slow down. The ONLY time they are opened is to spin the screw in the opposite direction.


Well that makes sense. Steam turbines only work in one direction so if you wanted to spin the shaft both ways you would need backing turbines in addition to ahead turbines, each with their own throttles, and you would not want them fighting each other.

[Looney11]

During my time in the surface fleet, back emergency was only allowed to be called by the CO.

Normally, the axle would rotate at 80rpm at minimum and with pitch control of the blades, you'd get your propulsion from changing pitch in those conditions where the 80rpm and little pitch was enough for you. When exceeding these limitations, the axle rpm would be increased to max 200 or so.

When ordering back emergency, the pitch of the blades would be rotated to their reciprocal pitch leading to immense pressure on the screw blades, we didn't reverse the axle spinning direction.

[drhyed]

Normally, the axle would rotate at 80rpm at minimum and with pitch control of the blades, you'd get your propulsion from changing pitch in those conditions where the 80rpm and little pitch was enough for you. When exceeding these limitations, the axle rpm would be increased to max 200 or so.

Ahhhhh so more like a variable pitch prop on an aircraft! Well that was an obvious answer I should have picked up right away.

[ET2SN]

No, you're telling the crew back aft to slow the boat as rapidly as possible without blowing up the gears and seals. :yep:

Many people have no idea how "hands on" this stuff is IRL. :03:

You're ordering an approximation of something you and your crew have practiced in the past, you just don't remember doing it. :salute:

[Eagle1_Division]

Translation:

I was going down the freeway, and decided I could stop faster by putting my car in "reverse"... :D

Basically, right?

So the takeaway is, massive cavitation and transients, possible damage to ship.

It'd be great to see this implemented so I'm not tempted to just use "back emergency" to stop dead still and go all stealthy. Since, you know, I guess it's probably louder than launching a torpedo?

Implementation; cavitation for a second, a transient, all with a loudness proportional to your speed squared, and have the game roll a dice and take into account your speed to see if you just took on some propulsion damage or not.

[FPSchazly]

Translation:

I was going down the freeway, and decided I could stop faster by putting my car in "reverse"... :D

Basically, right?

Yeah, except without destroying your transmission :har:

[Bubblehead Nuke]

Since, you know, I guess it's probably louder than launching a torpedo?


Just a bit louder...

Implementation; cavitation for a second, a transient, all with a loudness proportional to your speed squared, and have the game roll a dice and take into account your speed to see if you just took on some propulsion damage or not. Nah.. The propulsion train is DESIGNED for this kind of operation. It is loud, it shakes the hell out of the boat, but you will not damage anything.
As long as you are answering the backing bell you are going to be making more noise than normal due to the dynamics of the screw.

Like I said, you stand a large chance of losing the tail and that is bad, but you will not damage your propulsion train.

[ET2SN]

I remember hearing about an SSN that stripped its reduction gears.

The walkway (several feet above them) was buckled. :o

[Bubblehead Nuke]

I remember hearing about an SSN that stripped its reduction gears.

The walkway (several feet above them) was buckled. :o


Um... I heard about that one.

They were pre-underway and they were spinning the shaft astern to clear the steam chests and they left the locking gear engaged.

With the shaft locked and power applied something has to give.

[ET2SN]

OK, its been over twenty years for me since I got out but were you ever homeported out of Pearl? :Kaleun_Cheers:

It feels like we might know some of the same people. :D

USS Barbel (SS580) 1988-1991
USS Bremerton (SSN 698) 1991-1993

[Julhelm]

I think the game already makes you output more noise when you order reverse? If it doesn't it should for sure.

Also it's nice to see so many veterans post here who 'been there, done that' for real.

[Bubblehead Nuke]

I think the game already makes you output more noise when you order reverse? If it doesn't it should for sure.


Unfortunately the devs have stated otherwise.


You're not giving away yourself. You are rapidly decelerating so your flow noise and engine noise will decrease quickly.

Also it's nice to see so many veterans post here who 'been there, done that' for real.

I do not seek to make even a game like Cold Waters 'lifelike'. That would be too boring to say the least. Am trying to do is give you a glimpse into the world we lived and breathed in.

To be honest, what I would like to see it more Commanding Officer driven. Your crew KNOWS its job. You are relying on them to give you information so you can do your job. You are giving them commands and expect them to do their jobs.

Thus things like cavitation do not happen. The crew will stop you from making operational mistakes. You have to TELL them to cavitate.

It is the things like that which create a immersive environment. You are by god the CAPTAIN and your men are doing thier jobs with you in command.

[Delgard]

Yes, I like it being CO-driven, but being informed is also paramount where a staff is involved.

Even if Weps is telling me that my launched torpedo is not directed on a line of bearing, I think he should.

Seeing the teamwork of all crew members reporting info and the CO taking that "science" and then adding his own Commander's "Art" to decisions marks teamwork.

[Capt Jack Harkness]

Unfortunately the devs have stated otherwise.


Julhelm is one of the devs.

[Bubblehead Nuke]

Julhelm is one of the devs.

Then he directly contradicted what was put out by another dev.

[ET2SN]

To be honest, what I would like to see it more Commanding Officer driven. Your crew KNOWS its job. You are relying on them to give you information so you can do your job. You are giving them commands and expect them to do their jobs.

Thus things like cavitation do not happen. The crew will stop you from making operational mistakes. You have to TELL them to cavitate.


You've made some outstanding points. :up:

I've felt in the past that (modern) sub games treat the platform like its a P-51 fighter plane. Its just you as the pilot and your hardware. I've seen many people who stream sub games play against the machine code more than they play the game itself. Far too many excursions to test depth (even worse, test depth at flank speed), aggressive to the point of being suicidal (you're the commander of the ship, something that's considered as a national asset, AND 110 to 120 crew members who have families back home), dog fights that completely miss the point of how modern subs and weapons were designed to be used, spam out 12 torps and then dodge the fish that get shot at you, etc., etc., etc...

Now, I realize that some of you are itching to say, "Aw c'mon. Its just a game.." which is fine. How about we play a game of tennis.. with a rugby ball, helmets, and padding? After all, its just a game, right? :)

[Capt Jack Harkness]

You've made some outstanding points. :up:

I've felt in the past that (modern) sub games treat the platform like its a P-51 fighter plane. Its just you as the pilot and your hardware. I've seen many people who stream sub games play against the machine code more than they play the game itself. Far too many excursions to test depth (even worse, test depth at flank speed), aggressive to the point of being suicidal (you're the commander of the ship, something that's considered as a national asset, AND 110 to 120 crew members who have families back home), dog fights that completely miss the point of how modern subs and weapons were designed to be used, spam out 12 torps and then dodge the fish that get shot at you, etc., etc., etc...

Now, I realize that some of you are itching to say, "Aw c'mon. Its just a game.." which is fine. How about we play a game of tennis.. with a rugby ball, helmets, and padding? After all, its just a game, right? :)
Well, sim junkies like myself are greatly appreciative of the community who makes it real. Subs, planes, cars, you name it, there's just something nagging in the back of the mind when you know it could be more real than it is...

[subcritical]

OK, its been over twenty years for me since I got out but were you ever homeported out of Pearl? :Kaleun_Cheers:

It feels like we might know some of the same people. :D

USS Barbel (SS580) 1988-1991
USS Bremerton (SSN 698) 1991-1993

I was in Pearl from '92-95 and '98-99. I did have a friend that was on the 698 as RO when the dry dock mishap occurred, which should have been around that time.

[GeneralGamer]

Back Emergency works well for slowing to fire a moss against a persistent torpedo or re-acquiring an enemy position to get a shot off at him. The way I figure it they already know where you are. Back Emergency isn't giving away anything. Next video tomorrow I will use this in battle.

I shot a Tigerish that an enemy Warship evaded by making full circles over and over with the torp about 15meters off his tail. Nothing I've ever seen before :har:
Well worth watching for a laugh.

[ET2SN]

I was in Pearl from '92-95 and '98-99. I did have a friend that was on the 698 as RO when the dry dock mishap occurred, which should have been around that time.

Were you the guy who clogged the trash chute in the high-rise barracks? :k_confused:

:D

The Bremerton set a dubious record during that over-haul. We completed an 18 month over-haul in only 49 months. :doh: Part of it was due to what you mentioned, there was a fire up forward while they were welding something into place but that happened before I checked on board in 1991.

There were also funding issues (this was the tail end of the cold war and priorities were shifting) coupled with "Let's try something new" syndrome as new equipment was being developed. At the end of it, we wound up with a Flight II boat with no VLS and a bunch of modifications back aft. :salute: