Newsgroups: sci.military.naval
Subject: Re: Arsenal ship changes course
From: norton@ASYNC01.acm.org (Scott Norton)
Date: Fri, 30 May 97 00:18:57 EST

In article <5jl3jg$pjd@mercury.hgmp.mrc.ac.uk> cdownes@hgmp.mrc.ac.uk (Stephen Downes) writes:
> Matt Clonfero (Matt@aetherem.demon.co.uk) wrote
>
> > Stephen Downes <cdownes@hgmp.mrc.ac.uk> wrote:
>
> > > I'm confused. I thought if you fire a gun vertically, then you are either
> >> (a) aiming at a flying target, or
> >> (b) relying on a combination of wind, Coriolis forces and your own changes
> >> of course to prevent the shot coming down vertically on yourself.
>
> > (c) have a guided shell.
>
> Yes, I can see how that would help you miss yourself. What I don't see
> is how you can guide the shell through approximately a 45 degree change
> of course, to get maximum range, even with retractable winglets, without
> losing  a fair bit of forward velocity (and hence, range).


It seems counterintuitive, but the vertical launch is close to
optimal.  The real enemy is air drag, and it is very efficient to get
above 30,000 feet quickly.

For the EX-171 ERGM to get maximum range, it is launched at 60 degrees
elevation, and that is the limit of the gun.

For a 155 mm, 24 caliber, about 400 lb projectile which is half rocket
motor, the optimum trajectory is about an 85 degree launch, a
pitchover in the regime between 40,000 feet and 80,000 feet, rocket
firing near apogee, and a long downhill glide.

Prove it for yourself!  Just borrow a Cray computer from DSWA, and
optimize the trajectory piecewise.  Remember to include the lift limit
of your control system, and both parasite and induced drag.

The vertical gun came about when the Navy gun community stopped
worrying about firing ballistic ammunition, and assumed everything
would be guided and gliding.  You needed controlled flight to get the
range to the beach--a 25 mile standoff was mandatory, and in the COEA,
a 24 mile gun got zero points, since it couldn't reach the beach.
Trying to do this with just muzzle energy was impractical, and you
needed control and navigation anyway to have any kind of accuracy at
25 miles.

So once you have a control system, you can reoptimize the entire
trajectory.  85 degrees or so give the best range, and 90 degrees is
not very suboptimal.  The performance curve is fairly flat at these
high elevations.

> What are the compensatory advantages of the vertical gun? Lack of turret with
> saving in cost, ease of installation, stealthier? Rate of fire? Ease of
> switching target?

Cost is lower and reliablity is higher, since there is no train or
elevation drives, and the feed doesn't have to move the rounds to a
breach that moves around.  Stealth is improved , since the gun is
buried in the hull.  The mass is also lower, and installation can be
modular (using the same SSES B module as 64 VLS cells).  Since the
barrel doesn't move, its blast overpressure profile is fixed.  (Blast
overpressure from the 5"/62 firing the EX-171 might be a problem for
the SPY-1 radar faces if the gun is trained too far aft.)  The gun
doesn't block the field of view of any sensor or the field of fire of
any other weapon.  The recoil and barrel cooling systems can access
the barrel all along its length, rather than just at the breech end.


> In hope of illumination

Star shell, on the way!

>
> Stephen
>


--
Scott Norton
Norton@ACM.org
Defense Technology, Inc.
2920 South Glebe Road
Arlington VA  22206
+1-703-299-1656, fax: +1-703-706-0476

Newsgroups: sci.military.naval
From: norton@ASYNC01.acm.org (Scott Norton)
Subject: Re: Why No 155mm Naval Guns?
Date: Sat, 7 Mar 98 20:16:32 EST

In article <34F8436E.4324@iamerica.net> TMOliver <swrctmo@iamerica.net> writes:

> Nigel Brand wrote:

>
> The FMC 8" mount was cancelled in the late 70s for sound reasons,
> primarily the over-stressing of surrounding hull structure in the vessel
> types/sizes it was designed to equip.

Also, this mount didn't have a magazine or lower hoist, just a
doubled-up ready service drum.  So yes, you can put an 8" gun in the
space of a 5", but only if you leave out the magazine.  (My saying it
that way is a little flip, but practically, the 8-inch gun suffers
from the small number of projectiles it carries, if you compare on a
same-volume or same-weight basis.  And when you look at the life cycle
of a ship, volume or weight correspond to fuel.  So while the up-front
cost of a larger ship with a larger gun is minimal, the life-cycle
cost is significant.  Against most NSFS targets, 8-inch is too much;
you'd rather have two 155 mm rounds or four 5-inch rounds.

>
> There's been a lot of ether spent on smn in discussions of a USN
> 155mm/6" "vertical gun".  Unfortnately, no one has weighed in with an
> adequate description of that to which the term is referring.

For a picture, see

 http://www.nswc.navy.mil/tic/industry_day/peo-sc/pp3/sld004.htm

or my article in the May/June 1996 issue of Surface Warfare (page
17-18).

>
> Question....
>
> Back in the 70s/80s, speculative drawings began to appear for a gun
> mount, presumably 155mm/6"DP, illustrated with 90 degree elevation
> capability variously referred to a "vertical gun" or "vertical loading
> gun".  The design centered around a simple and mechanically feasible
> feature, between rounds the barrel/action would elevate to vertical for
> loading (presumably ejecting hot brass on the way), trading a slight
> slowing in RoF for the mechanical reliability and simpler structure of a
> vertical loading mechanism, and doing away with the need to move shells
> from vertical magazine storage to a horizontal position in a loader
> fixed to the gun breech/recoil mechanism.

Naval Weapons discusses this design, which was an FMC concept.
(Friedman's book, I think.  My copy is at the office.)

> I then and now tend to accept that this is what is being referred to as
> a "vertical gun", not some "fixed tube" requiring that every projectile
> be "guided"and in many cases booster-assisted, a factor which would
> raise to cost of NGFS or any other fire mission substantially, while
> substantially reducing potential range and warhead weight, inevitable in
> a projectile with a booster and/or guidance equipment (nozzles or popout
> control surfaces)

The fixed tube design gets the added benefit of a simpler feeding and
loading system.  That is part of the reliability benefit, along with
removing all the rest of the train and elevate equipment and the
cantelevered supporting of the barrel itself.   But the real support
for this design comes from the ship designers, who like the idea of a
gun that sits low, instead of being on a stand on the deck.  They can
hide the radar and IR cross section of the gun.  They don't have to
deal with a source of blast (the muzzle) that wanders around,
sometimes near radars, sometimes near air inlets, sometimes near
helicopters.

Regarding guided projectiles:

Much of the gun's design is driven by modern operational requirements.
The ships want to stand off 20 miles from the cost.  Without guidance,
the weapons are almost totally ineffective.  A post in this newsgroup,
in the never-ending BB vs BB thread, pointed out that the race in guns
and armor proved to be specious, and the key was who have the best
fire control.  Rounds that hit the water are 0% effective, regardless
of their caliber or the enemy's armor's thinness.

Guidance cost will come down, because of the commercial economies of
scale of GPS electronics and micromachined inertial measuring units.
Detroit will be buying IMUs in million-unit quantities.  Draper Lab,
the best INS house around, is putting GPS/INS guidance in the fuze
well.  Thirteen cubic inches is not too great a price to pay for an 8
meter CEP and first-round fire for effect.

Yes, rocket motors will be expensive, mostly because there is no
commercial production of rockets or their fuel.  So, a gun big enough
to get the needed range would be quite desirable, to bring the cost of
the mission down to an acceptable level.  Think of the Paris gun.  But
don't try to train and elevate such a gun.  Mount it low, like a bomb
ketch carried its mortars.

A vertical-loading gun, like FMC proposed, would reduce the complexity
of the trays in a conventional mounting, but would seriously reduce
the rate of fire for the gun.  The 5" gun suffers from being a
dual-purpose design, which has to be rather handy and quick firing
with 50-70 pound projectiles for the ship defense mission, while it
prefers to be long-barreled and efficient when firing the longer
range, 100 lb NSFS rounds, but with lower rate of fire requirements.
The up-gunned 5"/62 can't fire a 100 lb projectile with the same
muzzle energy as a 70 lb one because of the momentum limit (recoil is
mv while energy is  mv^2).  FMC has beefed the mount up as much as
they can in key areas, and turned the recoil cylendars around to get
a longer stroke, but the gun is recoil limited.  Beef it up, and it
will start to shear the bolts off the deck.

The VGAS gun represents an intentional split from the dual-purpose
design.  VGAS is for long-range NSFS.  For shorter range missions
where quickness is needed, use the a train-and-elevate mount which can
now be optimized for ship defense.

Remember that the Marines that will be supported by NSFS are not
landing at Iwo Jima in 10-knot amtracs under the support of
direct-firing destroyers a few miles off the beach.  They are going
inland in V-22's and helicopters, and approaching the beach
from over the horizon in AAAV's and LCACs.  NSFS needs the range to
support the Marine's operational maneuver.  The targets stretch from
25 miles to 70 miles inland, and the most important targets are the
interdiction and supression missions--taking out the enemies MLRS and
155 tubes, and stopping his mobile reserves.

--
Scott Norton
Norton@ACM.org
DTI Associates, Inc.
2920 South Glebe Road
Arlington VA  22206
+1-703-299-1656, fax: +1-703-706-0476

Newsgroups: sci.military.naval
From: norton@ASYNC01.acm.org (Scott Norton)
Subject: Re: Why No 155mm Naval Guns?
Date: Sat, 7 Mar 98 19:30:14 EST

In article <34F765A0.600839C3@ozemail.com.au> Nigel Brand
<niagb@ozemail.com.au> writes:

> Actually the USN and FMC are looking at this possibility. I believe
> there is also a whacko project for something called a Vertical Launched
> Gun of this calibre, firing guided projectiles, but I don't know the
> status of this.


Don't call it whacko. Its a part of the President's Budget, under
PE 0603795N, project S2323, "Vertical Guns for Advanced Ships (VGAS)."
The vertical configuration is quite suitable for this application.
The guided projectiles it will fire are optimally launched at about 70
degrees Qe, and the loss of launching vertically is not significant.
The project is currently in a design and analysis phase, with the big
money not starting for a year or so.

There is some information on the NSFS advanced technology needs and
initiatives at the SC-21 web site,

 http://sc21.crane.navy.mil/indust15.pdf

and the PEO-TAD site

 http://www.nswc.navy.mil/tic/industry_day/peo-sc/pp3/sld004.htm

--
Scott Norton
Norton@ACM.org
Defense Technology, Inc.
2920 South Glebe Road
Arlington VA  22206
+1-703-299-1656, fax: +1-703-706-0476