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SAM-N-8 Zeus

RyanCrierie

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Another little known thing, of which once again Designation Systems Net is the only real resource.

Copy of a xeroxed copy found in NHC files:

Naval Aviation Confidential Bulletin January 1949 - - - CONFIDENTIAL

ORDNANCE *

GUIDED MISSILES

ZEUS I LAUNCHED FROM 8-INCH GUN

On 15 September 1948, a guided missile was launched from a gun and deflected around a corner for the first time in the history of naval ordnance. This experimental missile, formerly called the Gun-Launched Guided Missile—Arrow Shell, has recently been named Zeus I by the Munitions Board and designated XSAM-N-8. The Naval Ordnance Laboratory is developing it under the sponsorship of the cognizant branches of the Research Division, Bureau of Ordnance.

Advantage over Conventional Projectile—The present experimental missile, which is fired from an 8-inch, smooth-bore gun, is fin-stabilized in flight rather than spin-stabilized. This reduces the drag and gives the missile, in comparison with the conventional 8"/55 projectile, a shorter time-of-flight to any slant range if it is used as an antiaircraft missile, or a longer range if it is used for bombardment. Although the fins of the missile are 8 inches in diameter, the body is saboted down to 4 inches. The design is thus lighter in weight than the standard 8-inch projectile and achieves a much higher muzzle velocity with the same powder charge. With 75 pounds of powder a muzzle, velocities of 3,150 feet per second have been obtained; with 100 pounds of powder, velocities of 4,000 feet per second.

Another advantage of the fin-stabilized missile is that it is not sensitive to the L/D (length/diameter) ratio. The present 8-inch Zeus I has an L/D ratio of 10, and calculations have shown that an L/D as high as 20 could be used without impairing the stability of the missile. The results of firing to date also indicate that the fin-stabilized missile has a smaller dispersion than the corresponding spin-stabilized Projectile.

Calculations show that if the Zeus I (the Arrow-Shell) is used without guidance, it has a greater single shot kill probability (S. S. K. P.) against maneuvering targets and a greater effective range than any of the present antiaircraft projectiles. However, when one step of guidance is added, calculations show that the S. S. K. P. and the range at which antiaircraft is effective are greatly increased. For example, the S. S. K. P. of the 5"/70. for a certain maneuvering target at 5,000 yards slant range is 0.025, while if one step of guidance is added to Zeus I (the Arrow Shell), its S. S. K. P. is 0.300 or an increase of 1,200 percent. Or to look at it another way, calculations show that for this same maneuvering target, Zeus I with one step of guidance has the same S. S. K. P. at 15.000 yards as the 5"/70 has at 5,000 yards; namely, 0.025. Thus, Zeus I will extend the effective range of antiaircraft fire to three times its present value for this particular S. S. K. P.

The guidance for Zeus I consists of a deflecting charge which is carried in the mid body of the missile and initiated from computers on the ground whenever the angle between the trajectory and the target becomes greater than any predetermined value, in this case 5°. This increases the S. S. K. P. of antiaircraft fire because, if the target maneuvers after the missile has left the gun, an intelligence system—that is, the ground radar and computer—knows where the target is and where the missile must go to secure a hit, and sends a message to the missile when the time has come to trigger the deflection charge. The deflection charge which reacts perpendicularly to the trajectory is sufficient for this weight of missile (72 pounds) to deflect it 5° into the corrected trajectory. The deflection charge produces a side thrust of 60,000 pounds for a period of 0.010 seconds, thus giving a total impulse of 600 lb./sec. to the missile.

Plans are now under way for Zeus II, an Arrow-Shell with guidance and extra propulsion. At the present time, plans call for a study of the possibility of adding some type of rocket propulsion, either solid of liquid propellant to the missile. This would increase the flight velocity over the muzzle velocity, decrease the time of flight to any slant range, and increase the range and the terminal velocity.
Photograph that was with the article (yes, i know, poor quality; but....hey....)
 

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Dilandu

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What I could not understand is how the control system knew, how exactly the shell is oriented? Without any kind of roll stabilization, how would the control station understood, at which direction the deflecting charge nozzle is pointed at the moment of activation?
 

zen

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Has to be timing.
Likely the deflection charge is always aligned a specific way and thus it's rpm is a known factor. It's thus just a matter of timing the initiation signal to coincide with the moment the rotation brings the charge pointing in the right direction.
 

stealthflanker

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The control is likely a combination of "Skid to turn" technique and "pif-paf" or "Jet dynamic" system similar to what used in PAC 3 or In Russian 9M96 missiles.

From the description tho, the Russian missile seems to be the closest analogue, with the deflection charge located at mid which, presumably the missile's center of gravity. Unlike ERINT tho, which will provide yaw or pitch moment to help turning. The deflection charge will directly push and turn the Zeus.

I'm curious tho about the possible guidance. Given the concept's age. Command or beamrider would be possibility with tail control. as those might be quite robust, to withstand massive acceleration in gun barrel. More advanced concept could use active radar homing, with canard control, and free to roll tail.
 

sferrin

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stealthflanker said:
The control is likely a combination of "Skid to turn" technique and "pif-paf" or "Jet dynamic" system similar to what used in PAC 3 or In Russian 9M96 missiles.

From the description tho, the Russian missile seems to be the closest analogue, with the deflection charge located at mid which, presumably the missile's center of gravity.
Aster is similar.
 

Dilandu

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zen said:
Has to be timing.
Likely the deflection charge is always aligned a specific way and thus it's rpm is a known factor. It's thus just a matter of timing the initiation signal to coincide with the moment the rotation brings the charge pointing in the right direction.
Hm... a probability, yes. Probably wouldn't work every time - a slight out-of-sync and the deflection would be in a wrong direction - but generally would work.
 

zen

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There maybe another option which is as the fins rotate there would be a differential in it's radar reflection.
Depends on the radar though.
 

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Six decades later the Italians used the same principle in 76mm guns with the DART munition, for the same purpose (extending AAA effective range).
https://www.leonardocompany.com/en/-/dart-strales-76mm

About the 8" thing; keep in mind the only platform that could have used it were the mere three Des Moines class cruisers.
https://en.wikipedia.org/wiki/Des_Moines-class_cruiser
 

Dilandu

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zen said:
There maybe another option which is as the fins rotate there would be a differential in it's radar reflection.
Depends on the radar though.
Actually... interesting possibility! Must admit, that I never thought of that!
 

Dilandu

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lastdingo said:
About the 8" thing; keep in mind the only platform that could have used it were the mere three Des Moines class cruisers.
https://en.wikipedia.org/wiki/Des_Moines-class_cruiser
They actually wanted something bigger. There are mentions that they planned to use incomplete battleship "Kentucky", rebuilding her into "anti-aircraft battleship" with three-two quadruple 8-inch RF turrets:





 

sferrin

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Would that have been in addition to Talos? :eek:
 

Dilandu

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sferrin said:
Would that have been in addition to Talos? :eek:
Basically, it was supposed to be short-range weapon with quick reaction time. Most of missiles of early 1950s were still liquid-fueled, and weren't exactly fast to launch. But then the solid-fuel RIM-2 "Terrier" came, and basically made "Zeus" obsolete in comparison.

But if Navy decided not to make a stopgap SAM out of "Talos" guidance test vehicle (which was exactly how "Terrier" was born), then probably "Zeus" would be deployed instead.
 

apparition13

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I just ran across this project, and think it is another example of potential technological development thought to be a dead end and abandoned too early. We're just now going back to the idea with DART and the guided rounds for the US 5" guns. What might have been with another several decades of development over the intervening years.

What I could not understand is how the control system knew, how exactly the shell is oriented? Without any kind of roll stabilization, how would the control station understood, at which direction the deflecting charge nozzle is pointed at the moment of activation?
From the first post: The present experimental missile, which is fired from an 8-inch, smooth-bore gun, is fin-stabilized in flight rather than spin-stabilized. This would require a new gun; the Des Moines wouldn't work as built. They would need smooth bore barrels, but also high elevation turrets.
 

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If they're talking about engaging at 15,000 yards, then the 41 degree elevation turrets in the Des Moines class would be adequate against most threats except very high level bombers*. Even low angle guns were useful AA weapons at longer range. Changing the Mk 16 to smoothbore probably wouldn't be too difficult, just swap out the liner for one without rifling, or build them without in the first place.

* And the turrets were designed for AA use, with provision to set the MT fuses on Anti-Aircraft Common shells just prior to ramming.
 

Dilandu

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From the first post: The present experimental missile, which is fired from an 8-inch, smooth-bore gun, is fin-stabilized in flight rather than spin-stabilized. This would require a new gun; the Des Moines wouldn't work as built. They would need smooth bore barrels, but also high elevation turrets.
Even with fin stabilization, the shell would still roll in flight. Some active roll stabilization was required. But could the 1940s gyro survive gun launch?
 

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Even with fin stabilization, the shell would still roll in flight. Some active roll stabilization was required. But could the 1940s gyro survive gun launch?
Unlikely it seems. The real breakthrough would have to wait until late 1960 or mid 1970's... At that time we reall have the technology for 10000G rated guided projectile.
 

Dilandu

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Unlikely it seems. The real breakthrough would have to wait until late 1960 or mid 1970's... At that time we reall have the technology for 10000G rated guided projectile.
It was suggested above that maybe the rotation of projectile could be somehow tracked by radar - maybe with some kind of corner reflector, which gave strongest return signal when it was directly above, or something - so the fire control could actually calculate in which position are shell in any moment.
 
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apparition13

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If they're talking about engaging at 15,000 yards, then the 41 degree elevation turrets in the Des Moines class would be adequate against most threats except very high level bombers*. Even low angle guns were useful AA weapons at longer range. Changing the Mk 16 to smoothbore probably wouldn't be too difficult, just swap out the liner for one without rifling, or build them without in the first place.

* And the turrets were designed for AA use, with provision to set the MT fuses on Anti-Aircraft Common shells just prior to ramming.
At 15k yards the estimated chance of an intercept is estimatrded to be 2.5%; the real difference was at 5000 yards where the probability was 30%. Would 41% still be enough elevation at that distance? Or would a 6" round with folding or flip-out winglets work with Worcester class 6" guns, re-gunned with smoothbores?
 

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At 15k yards the estimated chance of an intercept is estimatrded to be 2.5%; the real difference was at 5000 yards where the probability was 30%. Would 41% still be enough elevation at that distance? Or would a 6" round with folding or flip-out winglets work with Worcester class 6" guns, re-gunned with smoothbores?
The 6"/47 Mk 16DP guns on the Worcesters only had a maximum elevation of 44.5 degrees, just 3.5 degrees more than the 8" Mk 16 on the Des Moines and while they were designed for 12rpm/gun, they were unreliable, while the 8"/55 Mk16RF turned in a reliable 10rpm/gun.

I can't find the AA ceiling for either mount, but a ROM figure (range * sin elevation - (0.5* 32 fps * time of flight^2) )suggests their AA ceiling at 5000 yards as around 8000ft for the 8"/55 Mk 16 RF and 10,000 ft for the 6"/47 Mk 16 DP (probably on the high side as I'm not allowing for drag/external ballistics). Push that out to 15000yds and it's c27,000ft and c29,000ft. Attack profiles were changing as jet aircraft and missiles appeared, but both vessels had been deliberately designed as capable of anti-aircraft use, yet with those turret elevation limits.

A 600kt target will cover 15000 ft in about 75 seconds. In that time a Des Moines can pump out 12 barrels * 10 rpm/gun * 75/60 = 150 rounds. Even at only 2.5% that's a high chance of a kill. If, more realistically, they fire a box barrage to put 12 shells at 5000 yds as the target arrives, that's 12 30% chances of a hit. And they can potentially do that every 2000 yards from 15000 yards out.
 
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