Nothing stopping them from adding a GPS antenna to the tethered low profile buoy they've been using for years at minimal restrictions on depth and speed.
Yeah, and if you can't ping the floor what good are maps going to do you?...it's not like you can look out and see what's in front of you.
NikolaeVarius
Lifer
- Oct 25, 2006
- 11,036
- 11
- 91
I'll try this again:
The primary method of navigation for U. S. submarines is the Ships Inertial Navigation System (SINS). Initially this was a mechanical system using spinning gyroscopes to establish a stabilized platform and the data from very sensitive accelerometers was single and double integrated to provide values for velocity and distance traveled from a known location. The outputs of multiple, parallel systems were compared statistically for verification and reliability. From periscope depth the system could be adjusted for drift by use of a celestial star tracker integrated in a specially equiped periscope. An antenna could be raised above the surface to receive signals from shore based LORAN C facilities. Reference could be made to undersea land marks and beacons. Later versions use ring laser gyro navigation systems that use the principles of Einsteins theories to determine the same information earlier obtained from mechanical systems. An Antenna can be raised above the surface to receive GPS data as well as the ealier methods of verification. Sensitive versions of the modern navigation systems are capable of determining rates of continental drift.
The big problem with submarine based ICBM's is not navigation but the determination of the location of the targets. A huge project in the early days of the cold war was the mapping of the countries behind the iron curtain. We have better and more accurate maps of their countries than they do.
The primary method of navigation for U. S. submarines is the Ships Inertial Navigation System (SINS). Initially this was a mechanical system using spinning gyroscopes to establish a stabilized platform and the data from very sensitive accelerometers was single and double integrated to provide values for velocity and distance traveled from a known location. The outputs of multiple, parallel systems were compared statistically for verification and reliability. From periscope depth the system could be adjusted for drift by use of a celestial star tracker integrated in a specially equiped periscope. An antenna could be raised above the surface to receive signals from shore based LORAN C facilities. Reference could be made to undersea land marks and beacons. Later versions use ring laser gyro navigation systems that use the principles of Einsteins theories to determine the same information earlier obtained from mechanical systems. An Antenna can be raised above the surface to receive GPS data as well as the ealier methods of verification. Sensitive versions of the modern navigation systems are capable of determining rates of continental drift.
The big problem with submarine based ICBM's is not navigation but the determination of the location of the targets. A huge project in the early days of the cold war was the mapping of the countries behind the iron curtain. We have better and more accurate maps of their countries than they do.
Just curious...how well does a GPS work when its raining heavily? I am getting a GPS unit for the car, but I have never used a GPS in my life. Im assuming that a few kilometers of rain dropping might have the same effect of being a few meters underwater?
Yeah, rain doesn't do anything to GPS. I've been driving with a TomTom ONE in my car for a while and its worked great in rain and snow so I wouldn't worry about it. I haven't driven underwater before so I don't know about that, but my TomTom has never directed me off a bridge - maps are good.
soydios
Platinum Member
- Mar 12, 2006
- 2,708
- 0
- 0
When a sub is on patrol, it uses inertial navigation, which is essentially a very advanced compass+speedometer+clock. When they come to periscope depth, they can raise a mast to do a GPS and/or celestial navigation check.
A GPS unit would probably get skewed readings when underwater. Light travels slower in water than in air (this is the reason for diffraction). The x- and y-coordinates would be more-or-less the same (same effect of slower light waves from all satellites), but the altitude would be thrown off (apparently longer time for satellite-to-receiver indicates lower altitude), most likely. That is, assuming you get signal at all.
A GPS unit would probably get skewed readings when underwater. Light travels slower in water than in air (this is the reason for diffraction). The x- and y-coordinates would be more-or-less the same (same effect of slower light waves from all satellites), but the altitude would be thrown off (apparently longer time for satellite-to-receiver indicates lower altitude), most likely. That is, assuming you get signal at all.
MrDudeMan
Lifer
- Jan 15, 2001
- 15,069
- 94
- 91
Because 10s or 100s of KHz IS extremely low frequency for communication. Your point is baseless as this is all relative, and clearly he was talking within the scope of communication frequencies. Cordless phones in your house use 900MHz or more, making 100KHz less than .01% of that.
Born2bwire
Diamond Member
- Oct 28, 2005
- 9,840
- 6
- 71
Well to be specific it comprises from very low frequency to low frequency, ultra low frequency is from 300 Hz to 3 KHz. I cannot remember off hand what frequency the US uses as a beacon and communication for it's subs, but it is on the order of 10 KHz, in the very low frequency range.
Once upon a time, they wanted to build a submarine antenna in the UP of Michigan. It was for 18KHz. It was soethin glike 50 miles in length.
It was at least delayed for a while beause they were afraid it'd make the cows sterile, but I believe it was ultimately built (~15-20 years ago).
ULF / LF can penatrate the Earth and the oceans. However, the data rate is so small, they are restricted to small letter groups that are coded for specific actions (like 'AA' = "Surface RFN and get a real important message via UHF / SAT")
FWIW
Scott
It was at least delayed for a while beause they were afraid it'd make the cows sterile, but I believe it was ultimately built (~15-20 years ago).
ULF / LF can penatrate the Earth and the oceans. However, the data rate is so small, they are restricted to small letter groups that are coded for specific actions (like 'AA' = "Surface RFN and get a real important message via UHF / SAT")
FWIW
Scott
On the matter of signal attentuation in water, it's even more complicated. We all think in terms of conductivity and resistance as if they were constant. But in fact they are not - they change at different frequencies. Mathematically, the propogation coefficient of any medium at a particuclar frequency is written as a complex number, a + iß. The real portion, a, determines the wavelength of the high-frequency wave in the medium. The imaginary portion, ß, is the attentuation coefficient and determines how much the signal is reduced as it passes though one wavelength of medium. At low enough frequencies each of these is constant and ß is just another version of resistance. But in the right frequency range they both change with frequency. Over a certain frequency range, a drops evenly, from a low-freq value to a lesser value at high freqs, as frequency increases; ß rises from almost nothing at low freqs to a peak value and then reduces to near-zero again at high freqs.
The reason for this is the mechanism of the interaction of the medium with the electromagnetic waves. Molecules of the medium, and smaller parts of these molecules, are tumbling and turning at all times, each with their own characteristic freequencies. When the frequency of the applied electromagnetic wave is close to the frequency of the tumbling molecule, the molecule absorbs energy from the waves and gets more excited. Now it's tumbling a bit more energetically, and we observe this in a macroscopic way as an increase it the temperature of the medium. Meanwhile, the wave is now less intense because it contributed part of its energy to the molecules.
Now, it just happens that many smaller organic molecules absorb energy around 3 to 20 GHz. Water is a little lower, between 0.5 and 5 GHz. That is the basis of microwave ovens - the operate around 2 GHz. And GPS systems are in the same frequency range, so any water will attenuate (i.e., absorb substantial energy from) those frequencies. Thus the signals will not penetrate very far into water, salty or not. But the amount of attenuation is NOT directly dependent on conductivity at zero or very low frequencies, because the mechanism of absorbing the wave energy is not movement of ions through the water. It is the increase in rotational energy of the water molecules themselves.
The reason for this is the mechanism of the interaction of the medium with the electromagnetic waves. Molecules of the medium, and smaller parts of these molecules, are tumbling and turning at all times, each with their own characteristic freequencies. When the frequency of the applied electromagnetic wave is close to the frequency of the tumbling molecule, the molecule absorbs energy from the waves and gets more excited. Now it's tumbling a bit more energetically, and we observe this in a macroscopic way as an increase it the temperature of the medium. Meanwhile, the wave is now less intense because it contributed part of its energy to the molecules.
Now, it just happens that many smaller organic molecules absorb energy around 3 to 20 GHz. Water is a little lower, between 0.5 and 5 GHz. That is the basis of microwave ovens - the operate around 2 GHz. And GPS systems are in the same frequency range, so any water will attenuate (i.e., absorb substantial energy from) those frequencies. Thus the signals will not penetrate very far into water, salty or not. But the amount of attenuation is NOT directly dependent on conductivity at zero or very low frequencies, because the mechanism of absorbing the wave energy is not movement of ions through the water. It is the increase in rotational energy of the water molecules themselves.
Born2bwire
Diamond Member
- Oct 28, 2005
- 9,840
- 6
- 71
I think you have it backwards. At around microwave frequencies, the rotational movement of the water molecules dominates the absorption of energy via dielectric heating (this is the primary mechanism for generating heat in a microwave). When the frequency of the incident fields are on the order of the relaxation time of the molecules, then the frequency dependence on the conductivity comes into play. But at low frequencies, the polar molecules will "slowly" rotate in time with the field. This rotation is going to be slow due to the low frequency and the temperature increase will be low. Thus, at low frequencies, the eddy currents that arise due to the movement of ions in the water will be the dominant mechanism for attenuation. For water with any appreciable conductivity though, like salt water, the attenuation of the electromagnetic waves due to eddy currents will be dominant across Maxwellian frequencies, resulting in a more or less constant conductivity.
Re reply by Born2bwire:
The way I view it, the polar molecules ( water or whatever) do not exactly rotate slowly in time with the applied field. Their relaxation rates are much faster than low-frequency fields, so each molecule spends very little time oriented at the right angle to the field to actually experience a torque and absorb energy. Thus, the efficiency of absorbtion from low-frequency fields is poor, and the absorption coefficent is small.
I've not worked directly with microwaves in conductive aqueous media. My work was in polar molecules (and those with rotating substituent groups) with generally low absorption coefficients, so we deliberately stayed away from solvents with low-frequency conductivity, and ensured we used water-free organic solvents. This was in recognition that those sources of conductivity might show up at microwave frequencies as small contributions to absorption, but certainly not zero contributors. So we avoided those absorbers to make our work easier. I would not expect ionic movement to contribute significantly to microwave energy absorption in water - I'd expect the dielectric absorption by water itself to dominate largely. But I'll admit I do not have personal experience to quantify that.
The way I view it, the polar molecules ( water or whatever) do not exactly rotate slowly in time with the applied field. Their relaxation rates are much faster than low-frequency fields, so each molecule spends very little time oriented at the right angle to the field to actually experience a torque and absorb energy. Thus, the efficiency of absorbtion from low-frequency fields is poor, and the absorption coefficent is small.
I've not worked directly with microwaves in conductive aqueous media. My work was in polar molecules (and those with rotating substituent groups) with generally low absorption coefficients, so we deliberately stayed away from solvents with low-frequency conductivity, and ensured we used water-free organic solvents. This was in recognition that those sources of conductivity might show up at microwave frequencies as small contributions to absorption, but certainly not zero contributors. So we avoided those absorbers to make our work easier. I would not expect ionic movement to contribute significantly to microwave energy absorption in water - I'd expect the dielectric absorption by water itself to dominate largely. But I'll admit I do not have personal experience to quantify that.
Born2bwire
Diamond Member
- Oct 28, 2005
- 9,840
- 6
- 71
Exactly, the rotations of the molecules occur slowly in time. In my mind, the rotations are not a continuous motion, the molecule is directed up and then will probably suddenly rotate to be directed down after the EM wave has sufficiently changed sign. I did not mean that they rotate continuously in a slow motion, they will still rotate in a fast movement from up to down but the frequency over which the changes in the direction of the dipole moment will be "slow". So for the time-average picture, the temperature increase is very small. The dominance of dipole rotations in terms of dielectric heating at microwave frequencies is limited to water that is distilled or has a low conductivity. This is because the dipole rotations dominate over the heat produced by eddy currents in the form of the movement of ions in solution. However, if you have an appreciable amount of ions in solution, like in salt water, then the ionic currents going to dominate. Electromagnetic waves that impinge upon a conductive medium will induce eddy currents into the medium. These eddy currents will produce secondary fields that counteract the incident wave. So the attenuation of the incident waves is due field cancellation and not necessarily the loss of energy due to dielectric heating (though the induced currents will produce heat due to the resistance of the medium).
Text
The paper linked here shows the absorption EM waves in water and sea water in figure 6 (b). Sea water has a linear absorption, associated with a constant conductivity. However, the absorption of water (with low amounts of salinity) has noticeable peaks in the higher frequencies. These peaks are associated with the relaxation time of the rotation of the water molecules. I noticed in another paper that a better model for the microwave spectrum has two peaks, the second peak is in a much higher frequency. The model that is often used is the Klein-Swift Model
Your language suggests that you were using water as a solvent. As such, you would have to be careful to use compounds that would not readily ionize in the water. So, the obvious case in my mind is that sodium chloride can be suspended in an aqueous solution in maybe an oil or some other suspension that would not promote the breakdown of the ionic bonds. In water, sodium chloride will readily breakdown into its ions, resulting in a far different conductive behavior than if the sodium chloride molecules remained intact.
In my work we did NOT use water as a solvent - in fact, stayed as far away as possible. We were working with various polar organic solutes in non-polar organic solvents so that the absorption of microwaves by the solvent was extremely small. For example, cyclohexane was widely used in our lab, sometimes para-xylene. We scavenged water out of these by putting fresh clean sodium wire into the bottle. We were looking at the relaxation times of the polar molecules as a whole, and of polar substituent groups within the molecules that could rotate with respect to the rest of the molecule. These two processes have different relaxation times, and are affected differently by the surrounding solvent system - for example, by the viscosity of the solvent if you add a third non-polar high-molecular-weight material.
All very fundamental scientific research, but it helped me understand a lot about the nature of molecular interactions at close range, dynamic equilibria, and the role of natural relaxation times (there usually is more than one) in any process. In my later industrial career, that linked to process response times and control strategies.
All very fundamental scientific research, but it helped me understand a lot about the nature of molecular interactions at close range, dynamic equilibria, and the role of natural relaxation times (there usually is more than one) in any process. In my later industrial career, that linked to process response times and control strategies.
inertial guidance
and boomers do stay in communication 100% of the time when on "alert" (alert meaning they are ready to launch missiles)
they use either a floating buoy or floating wire antenna that are deployed to keep in communication as well as ELF (extremely low frequency) communications
TRENDING THREADS
-
Discussion Zen 5 Speculation (EPYC Turin and Strix Point/Granite Ridge - Ryzen 9000)- Started by DisEnchantment
- Replies: 24K
-
Discussion Intel Meteor, Arrow, Lunar & Panther Lakes Discussion Threads
- Started by Tigerick
- Replies: 21K
-
Discussion Intel current and future Lakes & Rapids thread- Started by TheF34RChannel
- Replies: 23K
-
-
Facebook
Twitter