The Ship Model Forum

by **Werner** » Thu Nov 01, 2007 8:01 am

Thanks for that, Dave!

It seems obvious that an attempt at stealth is futile; instead the kind of careful shaping of "bright" components on deck as has been done with the Burke, with the goal of decreasing the range of "lock" in Radar-guided missiles, is about all that profitably be done.

by **Dave Wooley** » Thu Nov 01, 2007 7:23 am

There seems to be a strong body of technical opinion that seems to indicate that stealth warships will be as easily seen as any conventional warship is seen by radar using EM disturbance detection. This is an extract from the pre-amble to a forth coming seminar on that subject .

The purpose of this work is to examine the feasibility to detect an ocean going vessel by its wake in the presence of wind waves. The wake of a ship and the ambient sea waves generate velocity field of electrically conductive seawater. Consequently a disturbance in the Earth geomagnetic field is induced. A closed-form solution for the magnetic field induced by the wake of a ship moving in a sea of finite depth is obtained, and the corresponding numerical simulations are performed. The results of the simulations are compared with the corresponding magnetic field disturbed by wind waves. Spectral analysis of the magnetic field, induced by the wake of a ship and sampled by an air-borne magnetometer moving steadily along a rectilinear path is performed. Numerical computations indicate that the spectra of the magnetic fields induced by the ambient random waves and by the wake of a moving body have quite different characteristic. Typically, the peaks of the body-induced magnetic field spectra are located in the range of frequencies where the corresponding values of the wind wave's spectra are less significant. It is shown that the feasibility of electromagnetic detection of ships wake depends on their speed and water depth.
Food for thought

Dave Wooley

by **Werner** » Tue Oct 30, 2007 11:48 am

Thinking about the HPM weapon from the post directly above, I wonder what would happen if the implosion parts of a nuclear weapon were sited around a sphere of piezoelectric crystals like quartz or certain man-made compounds. It might be possible to generate a substantial EMP from the explosion, and to tune the frequency by doping the crystals. It would make an interesting alternative warhead for cruise missiles.

by **Werner** » Sun Oct 28, 2007 11:50 pm

TheRegister notes that the USAF is preparing a new generation of active EW gear designed not only to confuse the enemy's sensors, but possibly strong enough to fry receivers and damage control/fusing circuits for weapons.

Is it possible that the world's foremost "stealth service" has concluded that stealth does not represent enough of an edge, and that it will likely be defeated on the battlefield, leaving aircraft designed around stealthy shapes with a decided disadvantage an enemy can employ to his advantage?

Certainly any emission completely defeats the purpose of stealth. The enemy can get an instant bearing on you, and an almost immediate indication of your speed, altitude and possibly your range. Two cooperating receivers can determine range instantly.

http://www.theregister.co.uk/2007/10/28 ... n_spotted/

by **Guest** » Fri Oct 26, 2007 2:34 pm

Werner wrote: $63 million... isn't that what it cost to equip the B-2 with an aluminum and plastic reclining lawn chair so the crew could sleep in their 40+ hour missions?

For $62 million I guaranty I can equip each and every B-2 with far superior padded fire proof and G-force proof lawn chairs! God damn no bid contracts!

by **Werner** » Fri Oct 26, 2007 2:17 pm

You mean this:

NavyTimes wrote:Report: DDG 51s heavily damaged by �bow slams�

Staff report
Posted : Monday Oct 15, 2007 18:50:02 EDT

Thirteen Arleigh Burke-class destroyers have suffered �significant� structural damage in rough seas because designers didn�t account for the effect of �bow slams� on the ships� hulls, Navy documents say � and fixing the problem could cost almost $63 million.

A Navy PowerPoint presentation, obtained by Navy Times, confirmed a report Thursday in the British defense publication Jane�s revealing the design problems in the Burke class.

Support beams and other structures inside the destroyers warp so much from the stress of withstanding high seas that they must be cut out and replaced, even in new ships � the destroyer Gridley, commissioned in February, already underwent repairs in September. The document listed the following ships as damaged: Arleigh Burke, Curtis Wilbur, Stout, Paul Hamilton, Stethem, Carney, Gonzalez, The Sullivans, Ross, McFaul, Higgins, Winston S. Churchill and Lassen.

�Damage ranges from local buckling of deck transverse beams and shell web frames and shell longitudinals resulting in several inches of permanent deformation,� said one slide in the presentation.

Internal structure warping is not uncommon among surface warships; the Navy�s cruisers and frigates have gone into shipyards for hull-stiffening repairs.

With each ship designed to serve for around 35 years, the Burkes are the Navy�s only destroyers in service. The first ship was commissioned in 1991, and shipyard Bath Iron Works of Bath, Maine, announced it has started work on the last, DDG 112, expected to join the fleet in 2011.

$63 million... isn't that what it cost to equip the B-2 with an aluminum and plastic reclining lawn chair so the crew could sleep in their 40+ hour missions?

by **Guest** » Fri Oct 26, 2007 1:16 pm

Speaking of seaworthy Burkes, anyone see the report on their bows crumpling?

by **Werner** » Fri Oct 26, 2007 11:59 am

bb-56 wrote:Question then, is the 6" turret on the DDx really a lot better than the 5" 62 caliber on the later FLT II Burkes?

My understanding was the /62 descends from the 5-inch/54, while United designed the 15.5cm to use standard NATO rounds. In addition to benefiting the supply chain, the 15.5 will be able to take advantage of R&D on the other 15.5s.

The Navy really wanted the fully automatic FMC (now United) 20.3cm, but it was too costly.

by **bb-56** » Fri Oct 26, 2007 10:50 am

Wow, reading through all your posts is sad, I thought something that looked that cool would be good but these weapons would work fine on a Burke Class and be seaworthy to boot. and less expensive if damaged or lost in hostile water.
Question then, is the 6" turret on the DDx really a lot better than the 5" 62 caliber on the later FLT II Burkes?

by **Guest** » Thu Oct 25, 2007 4:52 pm

Seasick wrote:The Soviet censors completely missed the value of the paper that the US used to build its first stealth technology. There was hell to pay at the Soviet academy of Sciences in Moscow. (The censors not the paper's author.)

The author, who was a dedicated communist, was quite dismayed at the application of his reasearch by the USA.

Soviet Union completely missed the significance of Sputnik also until the uproar it generated in the west trickled back into the Soviet Union. The Russians had a spare ICBM research booster sitting around, and the head man of Soviet rocketry program thought it would be neat to put a satellite into orbit with it. So he had his machine shop whip up an airtight aluminum sphere holding a battery and a transmitter in something like a 2 weeks and launched it. The Soviet political hierarchy thought he was jerking off and was about to reprimend him wasting state resources. Then the uproar in the west tricked back and the Soviet leadership decided to credit themselves with visionary leadership instead.

by **Seasick** » Thu Oct 25, 2007 4:33 pm

The Soviet censors completely missed the value of the paper that the US used to build its first stealth technology. There was hell to pay at the Soviet academy of Sciences in Moscow. (The censors not the paper's author.)

The author, who was a dedicated communist, was quite dismayed at the application of his reasearch by the USA.

by **Guest** » Thu Oct 25, 2007 11:49 am

Werner wrote:It is reasonable to assume there is cross-pollination in the Oceanographic realm which would solve many of your objections.

Not really, at least not if the assumption is the cross pollination would bear fruit in such a time frame as to make it reasonable to allow the expectation of its maturation to dominate current naval R&D.

by **Guest** » Thu Oct 25, 2007 11:45 am

Whether Poseidon's achievements are impressive from the view from ASW warfare depends on the size of the area it is averaging to achieve the so-called cm resolution of sea level.

If it is averaging the level of 50 sq km of ocean surface to an accuracy of cms, that accuracy is useless for submarine detection. On the other hand, if it can individually measure the level of every square meter of the ocean to an accuracy of cm, and do so fast enough so that the pattern itself does not distort out of all recognition between the time when one scans the first part of it to the last, then that's a different story.

by **Foeth** » Thu Oct 25, 2007 2:19 am

All your naysaying has been addressed by astronomers who use adaptive optics to obtain better resolution images from modest terrestrial satellites than can Hubble, far out in space.

I know that. My naysaying doesn't apply to individual techniques to find the moon or make a good picture of some location in space, but the compounded difficulties of scanning a very very very large surface with a highly stochastic nature at a very very very high spatial and temportal resolution which should be analyzed by a pretty powerful computer and a nifty alhorithm to find a signal that is well below the signal-to-noise ratio.

Article: http://news.bbc.co.uk/2/hi/science/nature/6922312.stm

The satellite's radar altimeter, Poseidon-3, is designed to measure the sea level height to within a few centimetres. It will do this from its orbit more than 1,300km above the Earth

Pretty impressive nonetheless!

Factsheet

by **Werner** » Thu Oct 25, 2007 2:01 am

Foeth wrote:Lasers reflect particularly bad on fluid interfaces. If fact, most of the time they do not reflect at all. They do reflect on the froth on waves, which is easily a few millimeters thick, adding noise to the signal. Add this this that you need to correct for atmospheric distortion which may be bad considering the weather pattern.

All your naysaying has been addressed by astronomers who use adaptive optics to obtain better resolution images from modest terrestrial satellites than can Hubble, far out in space.

I do not pretend to know the answers to your objections because I am not a technologist, and we used the models for an entirely different purpose. What I can say is that the objections you raise, while good in and of themselves, are areas that have been addressed by those in the field, and based on the use of Lasers and Radar for satellite mapping of ocean currents and other well-known activities, must have been addressed to some degree in the last two decades.

I can offer no insight into the these technologies, and anything I say along these lines is sheer conjecture, but I would say that there are projects in closely allied fields which have had to solve these problems for their own purposes. Therefore, it is reasonable to assume there is cross-pollination in the Oceanographic realm which would solve many of your objections.

by **Foeth** » Thu Oct 25, 2007 1:53 am

Lasers reflect particularly bad on fluid interfaces. If fact, most of the time they do not reflect at all. They do reflect on the froth on waves, which is easily a few millimeters thick, adding noise to the signal. Add this this that you need to correct for atmospheric distortion which may be bad considering the weather pattern. I doubt this distortion is helpful in keeping the laser of a single spot and I guess it will shift position (you are trying to find wave elevations for waves several meters long, the moon is a tad larger). Second, such an interferometer is a point source and you cannot obtain any directional information. Spacial correlation from one point is not really helpful. You'd pretty much have to nail the position of the sub first before you know where to aim an array of these sensors and the chances of a random sub happening to pass your beam are slim. And say you do manage to get past all these difficulties, you still have to get a pattern that is well below to signal-to-noise ratio.

And still, even if everything worked perfectly, I still say it will be difficult if not impossible to get the pattern of a wave a few mm's heigh from your data.

by **Werner** » Thu Oct 25, 2007 1:36 am

A Laser interferometer is quite able to distinguish differences of 1/4 the wavelength of light. The model used is not so interested in the different distances between the various samples and the observer, but the distance between the samples. You are looking for a particular pattern to emerge out of the static, kind of like the old-fashion color-blindness tests, not for the needle in a haystack. Once the pattern is established, you know the submarine's position to within a few dozen meters at the time the sample was taken, and you know it's course and speed. Of course in the 1980s the computing power required and the telecommunications from the satellite made this an academic exercise, but now it could possibly be done in real time. Perhaps the abandonment of SOSUS in the 1990s means the USN in fact followed this methodology for ocean barrier tripwires and added the instruments to the constellation of Naval Observation Satellites.

Satellite Lasers and Radars have been measuring the pressure wells and hills on the ocean caused by atmospheric pressures for some time. There was quite a significant one off the SE coast of Australia recently. A simpler use was the Laser reflector left on the Moon which was used to measure the orbit of the Moon to within a few millimeters in the 1960s.

I hasten to add that the amount of data gathered, the gathering techniques and the algorithms needed to process the data are far more robust and abundantly more verifiable than the extremely crude approach to modeling climate, with massive assumptions and cryptic, secretive and proprietary algorithms upon which certain profiteering scientists and politicians have raised the alarm of impending doom. The techniques for sensing deeply submerged submarines from space has received more public scrutiny and peer review than the work of elite climatologists like Nasa's Hanson, who refuses flatly to allow peer review.

by **Foeth** » Thu Oct 25, 2007 1:19 am

The reason I don't believe is that is difficult to attain accuracry within 1mm (or at least with great care) in laboratories when you are measuring wave heights. You usually use electrodes (wetted surface proportional to conductivity hence wave height) or optical systems (triangulation).

And say you are able to do it (which you're not), how do you intend to find one if you know if it's somewhere within a hundred square miles? Scan the entire surface? Correlate that data for several hundred measurements? Considering the stochastic nature of the wave height elevation, filtering out a milimeter heigh wave sounds far-fetched.

by **Werner** » Thu Oct 25, 2007 12:24 am

Foeth wrote:
Werner wrote:were able to detect deeply submerged submarines using the internal waves generated by the submarine which were observable as coherent millimeter-sized changes of the surface patterns above the submarine.
I've hear similar claims but I don't believe any of it.

The articles generated considerable interest among naval professionals, but you may also recall the low ebb the end of the USSR brought to the ASW "business". The publication coincided with the abolition of an ASW "desk" at the Pentagon and the abandonment of a number of ASW systems and programs as a part of "The Peace Dividend".

by **Werner** » Thu Oct 25, 2007 12:21 am

Anonymous wrote:What waves are you transmitting through the fossil beds? Acoustic or electromagnetic?

We weren't that sophisticated. We were looking for other markers in the bedding which indicated standing waves and the other phenomena the Russians relied on in their research. In this case the depth of the wave was a temporal marker of disruption and not an instantaneous indication.

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