Behind the China Missile Hype

Lezt · Mar 13, 2012

Hold on a minute, since heat transfer is one of my fields of study, I don't think you understand IR, or radiative heat transfer that well.

Stefan Boltzman's Law of radiant heat transfer is:

q1-2 = e1*e2*(s)*(F1-2)*((T1)^4-(T2)^4)

where;
q1-2= heat transfer from 1 to 2
e1 = emisitivity of source
e2 = emisitivity of receiver - a well designed receiver will be close to 1 or 0.99
T1 = temperature of source in Kelvins
T2 = temperature of receiver in Kelvins (rankins if you are IP)
F1-2 = view factor (but since it is a seaker, it doesn't matter as the seaker will look for a spike in its sector)

infinite atmosphere have an effective emisitivity of ~0.83 in the IR band. an avg temp of 0C (-50C at 10 km up, +30C near the surface) or 273K
space have an effective emisitivity of effectively zero, average space temp is -270K
Sea water have an effective emisitivity of ~0.5 in the IR band (IIRC) and a average water temperture of ~20C (293K)
A carrier will have a ems of around 0.95 for the deck, the deck depending on if it is reflecting sunlight and the heat generated will be 50-60C lets say 50 C for 323K

Note that boltmanz's law is based on T^4 and that the ems of the ship is higher than it's surrounding means, that the ship will appear much more intensely in an IR seaker than the surroundings. So from what I have posted, if you calculate it, q from the ship will be much bigger than anything else.

I mean, think about it, if atmospheric IR is such an issue, how can a heat seaker missile hit.. a tank in the desert during mid day?

Honestly, I don't think it is that hard to build a working seaker; you can probably build one with commercially available equipment. like for around 3000 USD you can get a micro-epsilon branded IR sensor with a 1 sec scan rate; at 40K USD you can get a Flir thermal imaging video recorder with a fairly good scan rate and excellent resolution.

You should also read into signal processing, if I know that the ship will be around X degrees plus or minus 10 Celcius, I can write a fast fouier transform that filter out all signal from X degrees plus or minus 10 Celcius. I have done something similar with electrical equipment, since we know that north america uses 60 Hz, I used a FFT to remove data originating from that frequency and my sensor readings became much cleaner.

^ the technology and science is all there; I don't know why you think it can't be done.

s002wjh · Mar 13, 2012

Lezt said:
Hold on a minute, since heat transfer is one of my fields of study, I don't think you understand IR, or radiative heat transfer that well.

Stefan Boltzman's Law of radiant heat transfer is:

q1-2 = e1*e2*(s)*(F1-2)*((T1)^4-(T2)^4)

where;
q1-2= heat transfer from 1 to 2
e1 = emisitivity of source
e2 = emisitivity of receiver - a well designed receiver will be close to 1 or 0.99
T1 = temperature of source in Kelvins
T2 = temperature of receiver in Kelvins (rankins if you are IP)
F1-2 = view factor (but since it is a seaker, it doesn't matter as the seaker will look for a spike in its sector)

infinite atmosphere have an effective emisitivity of ~0.83 in the IR band. an avg temp of 0C (-50C at 10 km up, +30C near the surface) or 273K
space have an effective emisitivity of effectively zero, average space temp is -270K
Sea water have an effective emisitivity of ~0.5 in the IR band (IIRC) and a average water temperture of ~20C (293K)
A carrier will have a ems of around 0.95 for the deck, the deck depending on if it is reflecting sunlight and the heat generated will be 50-60C lets say 50 C for 323K

Note that boltmanz's law is based on T^4 and that the ems of the ship is higher than it's surrounding means, that the ship will appear much more intensely in an IR seaker than the surroundings. So from what I have posted, if you calculate it, q from the ship will be much bigger than anything else.

I mean, think about it, if atmospheric IR is such an issue, how can a heat seaker missile hit.. a tank in the desert during mid day?

Honestly, I don't think it is that hard to build a working seaker; you can probably build one with commercially available equipment. like for around 3000 USD you can get a micro-epsilon branded IR sensor with a 1 sec scan rate; at 40K USD you can get a Flir thermal imaging video recorder with a fairly good scan rate and excellent resolution.

You should also read into signal processing, if I know that the ship will be around X degrees plus or minus 10 Celcius, I can write a fast fouier transform that filter out all signal from X degrees plus or minus 10 Celcius. I have done something similar with electrical equipment, since we know that north america uses 60 Hz, I used a FFT to remove data originating from that frequency and my sensor readings became much cleaner.

^ the technology and science is all there; I don't know why you think it can't be done.

well IR is not my field of study, but if IR is that easily implment into a hypersonic ballistic missile, then why haven't we seen a IR seeker on these type of missile.

also can a glass dome typically use for IR/optical seeker withstand the temperture during re-entry. whats the temperture/pressure exert on the missile and its surrounding atomsphere during missile terminal phase. untile someone can anwser these or link shows its done or relative simple to sovle, i still say RF is the prefer method.

for signal processing to work, the noise has to be less than signal. now if i put a fireball infront of seeker, can the seeker detect heat emmsion from carrier behind the fireball.

a heat sink missile can hit tank because the dome doesn't have to worry about the pressure/temperture during re-entry, nor its hypersonic. when you reach mach7 or more, the pressure/heat increase affect your receiver, increase temperture/pressure of missile surface and its surrounding. the equation you suggest doesn't take care the atomsphere pressure/heat generate from a hypersonic missile when passing through air at extreme speed.

to find the true receiver temperture/pressure, you need simulate the effect of atomsphere pressure at that speed. and create a glass dome that can withstand pressure/temperture during re-entry. thats my point i've talking about for the past posts. it might be possible to solve these issues, but is the cost/resource/time justify put in IR sensor along with RF

again that equation doesn't factor in other vairable, it assume both target and receiver are stationary, maybe. for ballistic missile you need consider the increase in pressure/temperture to the missile and its surrounding due to its speed. there might be an equation for that too. and you can plug in the number and see if its possible for speed at mach7 or more

delft · Mar 14, 2012

s002wjh said:
yes it make sense for redundancy, but at some point the price, time, diffculty become issues. most missile only need one sensor, put more than one increase the cost, time, integration etc. espeically for ballistic missle and IR, would pla favor use both RF and IR, spend alot time/cash try to fix the issue associate with IR on ballistic missile or is it better to use that resource for better algorithm development, better rf sensor, and testing etc etc. why spend so much time/cash to put another detection sensor that basically has the same purpose as teh RF sensor. in any project, the PM has to consider the cost, time, resource management etc, RF is the better choice.

You need one, or even more, back ups to cater for failure on one of the channels, possibly due to measures taken by the target.

s002wjh · Mar 14, 2012

delft said:
You need one, or even more, back ups to cater for failure on one of the channels, possibly due to measures taken by the target.

like i said, you don't need several different type of sensors if the cost, implmentation is too great. even in modern missile, i can't think of a single missile that has both IR and RF sensors. and i would think the people who design it know what they doing.

Lezt · Mar 14, 2012

s002wjh said:
well IR is not my field of study, but if IR is that easily implment into a hypersonic ballistic missile, then why haven't we seen a IR seeker on these type of missile.

If you have not seen it than it does not exist? I love the sidewinder example, the seaker (sun tracker) was developed in the late 40s, the missile was first produced in 1950s and people generally know about it in the 70s. 30 years or more is a common lag between military development and common knowledge of its existence.

s002wjh said:
also can a glass dome typically use for IR/optical seeker withstand the temperture during re-entry. whats the temperture/pressure exert on the missile and its surrounding atomsphere during missile terminal phase. untile someone can anwser these or link shows its done or relative simple to sovle, i still say RF is the prefer method.

1) seaker is for terminal phase only meaning it is only active once within the atmosphere
2) because of 1, the seaker lense could be heat shielded. and the shield can be ejected once in the atmosphere
3) pressure have minimal impact on IR, the emisitivity change due to differential pressure is minimal, since the stefan boltzman's law is a temperature to the forth power, the changes in temperature is a much higher driving factor as T^4 is much bigger.

s002wjh said:
for signal processing to work, the noise has to be less than signal. now if i put a fireball infront of seeker, can the seeker detect heat emmsion from carrier behind the fireball.

not true, you are thinking of displacement filtering. with fast fouier transform, you can remove specific frequencies. I have used FFT to remove the 60 hertz mains power frequency from my sensors before which were at a much lower frequency and lower voltage.

Infact, the first gen sidewinder have an awful tendency to lock onto the sun, as the sun is a much hotter object than an aircraft exhaust. later versions fixed this with a better heat mirror filter, N2 bottle and by signal processing. Simularly, the missile was made more resilient to flares, as the temperature which flare burn at can be filtered out with FFT (ofcourse not perfectly as flare is designed to burn as hot as lets say an engine).

All of these have been done and is proven technology.

s002wjh said:
a heat sink missile can hit tank because the dome doesn't have to worry about the pressure/temperture during re-entry, nor its hypersonic. when you reach mach7 or more, the pressure/heat increase affect your receiver, increase temperture/pressure of missile surface and its surrounding. the equation you suggest doesn't take care the atomsphere pressure/heat generate from a hypersonic missile when passing through air at extreme speed.

I think you know in physics, we call something a law (like the the law of thermal dynamics) it is sufficiently proven. Boltzman's theory is heat transfer entirely by radiation and stefan, emperically derived the constants. This have been continuously refined and proven by the scientific community for the past 200 years. If you have issues with it, you can take it up with a credible scientific journal like the journal of heat transfer.

Pressure does not affect radiation much, it changes the fluid emisitivity and you are talking in the order of a few percent with extreme change. This is why an IR camera mounted on a deep sea submarine will be as accruate when it is deep (1000 atm) or when it is near the surface (1 atm). You can add a emisitivity function term to the equation, not necessarily a hard thing to do, just more iterations. So the equation do include pressure and other variance into consideration. But at the end of the day, the temperature is the driving factor of that equation.

s002wjh said:
to find the true receiver temperture/pressure, you need simulate the effect of atomsphere pressure at that speed. and create a glass dome that can withstand pressure/temperture during re-entry. thats my point i've talking about for the past posts. it might be possible to solve these issues, but is the cost/resource/time justify put in IR sensor along with RF

again that equation doesn't factor in other vairable, it assume both target and receiver are stationary, maybe. for ballistic missile you need consider the increase in pressure/temperture to the missile and its surrounding due to its speed. there might be an equation for that too. and you can plug in the number and see if its possible for speed at mach7 or more

As I have put it above your concerns are invalid. the technology is already on the AIM132 which travels at around Mach 3-4.

Since this is not your area of study, just believe me when I say that the science and technology is all there as individual piece. Can it be combined into a small enough package which can widstand the stresses of reentry is another question.

s002wjh · Mar 14, 2012

Lezt said:
If you have not seen it than it does not exist? I love the sidewinder example, the seaker (sun tracker) was developed in the late 40s, the missile was first produced in 1950s and people generally know about it in the 70s. 30 years or more is a common lag between military development and common knowledge of its existence.

1) seaker is for terminal phase only meaning it is only active once within the atmosphere
2) because of 1, the seaker lense could be heat shielded. and the shield can be ejected once in the atmosphere
3) pressure have minimal impact on IR, the emisitivity change due to differential pressure is minimal, since the stefan boltzman's law is a temperature to the forth power, the changes in temperature is a much higher driving factor as T^4 is much bigger.

not true, you are thinking of displacement filtering. with fast fouier transform, you can remove specific frequencies. I have used FFT to remove the 60 hertz mains power frequency from my sensors before which were at a much lower frequency and lower voltage.

Infact, the first gen sidewinder have an awful tendency to lock onto the sun, as the sun is a much hotter object than an aircraft exhaust. later versions fixed this with a better heat mirror filter, N2 bottle and by signal processing. Simularly, the missile was made more resilient to flares, as the temperature which flare burn at can be filtered out with FFT (ofcourse not perfectly as flare is designed to burn as hot as lets say an engine).

All of these have been done and is proven technology.

I think you know in physics, we call something a law (like the the law of thermal dynamics) it is sufficiently proven. Boltzman's theory is heat transfer entirely by radiation and stefan, emperically derived the constants. This have been continuously refined and proven by the scientific community for the past 200 years. If you have issues with it, you can take it up with a credible scientific journal like the journal of heat transfer.

Pressure does not affect radiation much, it changes the fluid emisitivity and you are talking in the order of a few percent with extreme change. This is why an IR camera mounted on a deep sea submarine will be as accruate when it is deep (1000 atm) or when it is near the surface (1 atm). You can add a emisitivity function term to the equation, not necessarily a hard thing to do, just more iterations. So the equation do include pressure and other variance into consideration. But at the end of the day, the temperature is the driving factor of that equation.

As I have put it above your concerns are invalid. the technology is already on the AIM132 which travels at around Mach 3-4.

Since this is not your area of study, just believe me when I say that the science and technology is all there as individual piece. Can it be combined into a small enough package which can widstand the stresses of reentry is another question.

yes it come to a point with all the stuff need to be done on the ballistic missile just in order to use IR. might as well use RF. on top of that no one knows IR should be used on ballistic missile, it hasn't done it before, and Can you tell me a missile that has both IR and RF seeker? or say IR on ballistic missile done it before. if not, you arguement is worthless since if IR is better/cheaper/whatever the reason to subsitude or combine with RF for hypersonic missiles, then engineer will develop this type of missile long ago. IR has been on the market for decades.

No, if your noise is greater than your signal than you can't detect the signal period. i work in defense for many years, although i'm not in IR, but i work in RF/digital stuff. you can't detect the signal if your clutter is greater than your signal.

you are not looking at the sun or anything, the entire frontal portion of missile are enclosed with high pressure/heat. put a big fire ball right infront of your ir sensor, so it cover entire surface of seeker, i don't care what algorithm you use, can you detect objects behind it. its not like we don't have sophiscate ir sensor in our lab. i even try this experiment before.

again you use arguement about because it has been done to A with these variable, so it must be true for B. there are reason engineer didn't use IR for hypersonic missiles. mach3 is only supersonic. as the speed increase the increase in pressure/temperture is not linear. we are not talking about few degrees, its thousands kelvin. your entire seeker is covered by hot gas/high pressures. the minium speed is mach7+ to some mach 17, depend on type of ballistic missiles. the pressure/tempture at that speed is huge compare to mach3.

another thing is weather can affect IR sensor, which RF doesn't have to worry about.

here is some link about diffculties need to be solved for the IR seeker mounted on a ballistic/hypersonic missiles. note ballistic missile are typically faster than hypersonic cruise missile during re-entry/terminal phase.

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When an optically guided hypersonic vehicle flies in the atmosphere, the scene is viewed through an optical dome. Because of hypersonic friction with the atmosphere, the optical dome is inevitably covered by a serious shock wave, which threatens to alter the dome's physical parameters and further induce wavefront distortion and degradation of images. By studying the physical phenomena occurring within the optical dome in such an adverse environment, this paper identifies the relationship between the variation of the dome's optical characteristics and the infrared image degradation. The research indicates that the image quality degrades sharply as the vehicle's Mach number increases. Simulations also show that while the thermo-optic effect, elastic-optic effect, thermal deformation, and variation of transmittance have little effect on the optical system, the thermal radiation severely degrades images when vehicles fly at hypersonic speeds

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there are some pictures shows the result of the image

Table I. Physical characteristics of shock wave when the vehicle flies at different Mach numbers.
Mach number Temperature (K) Air density (Kg/m3) Density of heat flux(MW/m3)
3.0 440 1.57 0.11
4.0 480 1.69 0.34
5.0 530 1.82 0.64
6.0 590 1.97 1.35
8.0 800 2.21 3.30

Hypersonic flights lead to high temperature flows, dense plasma sheath, and cumulative heating of air-frames. Consequently the performance of all on-board sensor systems such as GPS, telemetry, communication, command and control, radar, ladar, and electro-optical sensors are all adversely affected to varying degrees by the hypersonic environment. Further, the dynamic range of parameters that characterize the environment is quite large and is strongly influenced by many factors including altitude, velocity, duration of flight, geometry of the vehicle, airframe, and heat-shield material. For instance, the electron density can vary by several orders during the course of a trajectory. Hence, sensor systems encounter a variety of situations. Some of the issues encountered include signal attenuation, communication blackout, signal distortion due to turbulent flow, radiation from heated optical windows, and emission from hot flows. Communication blackout although old is still a problem and is encountered when the signal frequency is well below the plasma frequency. A successful technique to work around or eliminate the plasma sheath would alleviate some of the problems. Although several schemes have been proposed to overcome blackout, all of them have serious limitations and only work under preferred ideal conditions. An adaptive sensor system which uses a diagnostic tool to sense and adaptively match to the environment will be desirable. Even in the case when the RF signal is above the plasma frequency the plasma sheath may be a dispersive, inhomogeneous, fluctuating, and lossy medium. This poses challenges to wideband RF system using conformal arrays. With arrays we also face the problem of mutual coupling and impedance mismatch effects on beam forming. Moreover, the signal transmitted from the vehicle may be sufficiently intense to initiate nonlinear processes in the plasma sheath. In addition, the performance of GPS receivers is a concern because the receivers have to contend with blackout, attenuation, and distortion due to turbulence. The rapid maneuvers and high velocity place limitations on the integration time of the processing algorithms of the receivers. Although optical sensors are not similarly affected by the plasma they have their own share of issues. The hot window can radiate at infrared frequencies and the hot flow fields can emit and absorb at optical frequencies thereby seriously affecting the optical and EO/IR sensors on board. We are particularly interested in assessing the impact of environment on spectral measurements and imaging. Beam pointing error and wave front distortions are also of concern. Research opportunities exist in the analyses and mitigation of the above-mentioned issues confronted by sensors aboard hypersonic platforms.

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Behind the China Missile Hype

Lezt

Junior Member

s002wjh

Junior Member

delft

Brigadier

s002wjh

Junior Member

Lezt

Junior Member

s002wjh

Junior Member