Northrop Grumman B-21 Raider (LRS-B)

Logically, if it has been tested to 1800°C as a stealth coating material, it would have to be in relation with a representative aerospace airframe, hence with a degree of thermal expension. Otherwise this will constitute a fraud.
 
TomcatViP said:
Logically, if it has been tested to 1800°C as a stealth coating material, it would have to be in relation with a representative aerospace airframe, hence with a degree of thermal expension. Otherwise this will constitute a fraud.
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This is preliminary research. It might be the next wonder material or it might be a dead end. But fraud is a really strong word to use.
 
Yes. And I did forgot that tiles (thermo protective tiles) don't expand but slide one relatively to an other as the structure expand.
Hence, no extreme thermal expansion might have to be supported by such material.
 
TomcatViP said:
Yes. And I did forgot that tiles (thermo protective tiles) don't expand but slide one relatively to an other as the structure expand.
Hence, no extreme thermal expansion might have to be supported by such material.
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Except I'd think gaps would be a no-no for stealth.
 
“In fact, applying the ceramic “skin” is fairly straightforward. A liquid ceramic precursor is sprayed onto the surface of the aircraft. And as the liquid precursor is exposed to ambient air, it undergoes a series of chemical reactions and is converted to the solid ceramic material”

The above is the key paragraph IMO assume it’s like any coating that’s applied to a surface albeit with different chemistry.
 
sferrin said:
TomcatViP said:
Yes. And I did forgot that tiles (thermo protective tiles) don't expand but slide one relatively to an other as the structure expand.
Hence, no extreme thermal expansion might have to be supported by such material.
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Except I'd think gaps would be a no-no for stealth.
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The A-12 wedged leading edge would be an accute comparison with foam replaced by ionized air in the interstices. Aslo, some protective material are done to slide ontop of each others leaving no gap on the entire range of temperature.
 
I guess the rate of expansion even at supersonic speeds might be fairly low given the low thermal expansion coefficient of ceramics. But vibration and aeroelastic loading might be more complicated scenarios.
It's certainly a very interesting development and could have all kinds of applications in hypersonics too.
 
There is not, nor will there ever be stealth "coatings" that work at high mach, when inside the earths atmosphere.
 
sublight is back said:
There is not, nor will there ever be stealth "coatings" that work at high mach, when inside the earths atmosphere.
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What makes you so sure? I’d be interested to hear your take on the limiting factors and what makes them insurmountable.
 
SparkyDinosaur said:
sublight is back said:
There is not, nor will there ever be stealth "coatings" that work at high mach, when inside the earths atmosphere.
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What makes you so sure? I’d be interested to hear your take on the limiting factors and what makes them insurmountable.
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Whether you're generating a boundary layer in front of the leading edge or it's the leading edge itself, the ambient temperature of the air is going to be insanely high. Hypersonic speeds basically make your signature huge for IR sensors. At that point, there's no reason to really have stealth coatings unless you want to retain some type of dual subsonic/hypersonic role.
 
SparkyDinosaur said:
sublight is back said:
There is not, nor will there ever be stealth "coatings" that work at high mach, when inside the earths atmosphere.
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What makes you so sure? I’d be interested to hear your take on the limiting factors and what makes them insurmountable.
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The electromagnetic conduction in materials changes with temperatures. These changes adversely effect the materials ability to reduce radar signatures. If nobody has coined a term for this, we'll just start calling it "SPF's Law".
 
TomcatViP said:
The paper states that
TomcatViP said:
Initial results (extracted from the link above from @bobbymike ):
What’s more, the ceramic material retains its radar-absorbent characteristics at temperatures as high as 1,800 C (and as cold as -100 C).
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Ceramics have high specific heats because of the crystals lattice structure, so they will if one is found, continue to act as ram at higher temps as compared to an iron ball type of ram. Metals expand and therefore the energy needed to conduct electricity rises with temps. Electromagnetic waves do penetrate metals contrary to popular belief but the wave rapidly decays and the skin depth penetration is as I recall from wave mechanics found by calculating (1/e) * E0 where E0 is the energy of the free wave. So an electromagnetic wave will pass through a sheet of metal that is thin enough. Which makes me curious about the thin gold coated canopies.
 
sublight is back said:
There is not, nor will there ever be stealth "coatings" that work at high mach, when inside the earths atmosphere.
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There have been stealth coatings and materials on hypersonic vehicles for over 50 years.
Reentry vehicles are shaped for RCS reduction and have been since the 50s. Of course, when moving through the atmosphere at high speeds they are covered by ionized gas, which itself changes the radar return. The vehicle is shaped - and coated - to change the nature of that ionized gas. Ablative coatings can change what frequencies the ionized gas reflects or absorbs, how much, etc.
 
quellish said:
sublight is back said:
There is not, nor will there ever be stealth "coatings" that work at high mach, when inside the earths atmosphere.
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There have been stealth coatings and materials on hypersonic vehicles for over 50 years.
Reentry vehicles are shaped for RCS reduction and have been since the 50s. Of course, when moving through the atmosphere at high speeds they are covered by ionized gas, which itself changes the radar return. The vehicle is shaped - and coated - to change the nature of that ionized gas. Ablative coatings can change what frequencies the ionized gas reflects or absorbs, how much, etc.
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Sorry, I should have been more specific and qualified that statement with "VLO".
 
aim9xray said:
"Oh, yeah. Oooh, ahhh, that's how it always starts. Then later there's running and um, screaming."

"B-21 Program - Red Team Review", Dr. Ian Malcolm, Senior Member
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"We spared no expense" would be appropriate, too. And "that's really one big pile of sheet."
 
trose213 said:
There's also New START to cross off the list.
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With China being considered the new (and only ?) opponent in 90% of the discussions in security spheres, I'm not sure if any treaties not including the same party will have considerable effect in implementation of any new program. When the enemy you're facing doesn't have the constraints described in the New Start, why unnecessarily put them on yourselves.
 
A bomber only counts as a single launcher and warhead. Assuming B-21s are nuclear capable from the get go, the US can always denuclearizate other bombers. I believe nearly twenty B-52s and some non combat coded B-2s fall into that category currently. There probably won’t be many B21s in service when NEW START expires, and it cannot be renewed.
 
Josh_TN said:
A bomber only counts as a single launcher and warhead. Assuming B-21s are nuclear capable from the get go, the US can always denuclearizate other bombers. I believe nearly twenty B-52s and some non combat coded B-2s fall into that category currently. There probably won’t be many B21s in service when NEW START expires, and it cannot be renewed.
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I hope that the B-21s are nuclear capable from the start and that the USAF does not go down the same route that it took with the initial Block 10 B-2s when they were first delivered to the Air Force, I would think that would be bad news for the entire programme.
 
I can't speak to their plan, like most things it seems classified. If the buy really ended up being 145 aircraft, an initial batch that was non nuclear capable wouldn't be a big deal. They can be nuclearized later and honestly the bulk of the work they do is going to be conventional anyway. If the US really has a problem of too many nuclear capable bombers before Feb 2026, that seems like a good thing to me. Perhaps they will just take an extra SSBN offline ('non-deployed') for a few months until New START expires so as not to have to modify any existing bombers. That would allow for twenty additional nuclear capable bombers.
 
Josh_TN said:
I can't speak to their plan, like most things it seems classified. If the buy really ended up being 145 aircraft, an initial batch that was non nuclear capable wouldn't be a big deal. They can be nuclearized later and honestly the bulk of the work they do is going to be conventional anyway. If the US really has a problem of too many nuclear capable bombers before Feb 2026, that seems like a good thing to me. Perhaps they will just take an extra SSBN offline ('non-deployed') for a few months until New START expires so as not to have to modify any existing bombers. That would allow for twenty additional nuclear capable bombers.
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Let's just say things aren't looking too optimistic for the New START follow on.
 
trose213 said:
Josh_TN said:
I can't speak to their plan, like most things it seems classified. If the buy really ended up being 145 aircraft, an initial batch that was non nuclear capable wouldn't be a big deal. They can be nuclearized later and honestly the bulk of the work they do is going to be conventional anyway. If the US really has a problem of too many nuclear capable bombers before Feb 2026, that seems like a good thing to me. Perhaps they will just take an extra SSBN offline ('non-deployed') for a few months until New START expires so as not to have to modify any existing bombers. That would allow for twenty additional nuclear capable bombers.
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Let's just say things aren't looking too optimistic for the New START follow on.
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Agreed. While the Biden administration was willing to renew New START, I think this was only because the US has no new warheads or launch platforms in production. By 2026, at a minimum the B-21 should be entering production. At that point I doubt any arms control regime that doesn’t involve China would be adopted, and China has shown no interest in arms control.
 
Josh_TN said:
trose213 said:
Josh_TN said:
I can't speak to their plan, like most things it seems classified. If the buy really ended up being 145 aircraft, an initial batch that was non nuclear capable wouldn't be a big deal. They can be nuclearized later and honestly the bulk of the work they do is going to be conventional anyway. If the US really has a problem of too many nuclear capable bombers before Feb 2026, that seems like a good thing to me. Perhaps they will just take an extra SSBN offline ('non-deployed') for a few months until New START expires so as not to have to modify any existing bombers. That would allow for twenty additional nuclear capable bombers.
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Let's just say things aren't looking too optimistic for the New START follow on.
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Agreed. While the Biden administration was willing to renew New START, I think this was only because the US has no new warheads or launch platforms in production. By 2026, at a minimum the B-21 should be entering production. At that point I doubt any arms control regime that doesn’t involve China would be adopted, and China has shown no interest in arms control.
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The PRC for now is still irrelevant, the problematic part for the US is the March 1st weapons.
 
In_A_Dream said:
FighterJock said:
Why stop at 145? I wanted the USAF to order 200 B-21s.
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Look forward to 2030 and the possible rapid increases in modernization between China & the US. We could be looking at the design phase of an entirely new bomber.
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I like the sound of a new bomber, because by the 2030s the B-52 will be getting on to nearly 90 years old and will be needing replaced even with the new engines.
 
If the NGAD program is a success, could this lead to a rolling strike aircraft to follow on from the B-21?
 
Foo Fighter said:
If the NGAD program is a success, could this lead to a rolling strike aircraft to follow on from the B-21?
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You know, it's really hard to predict what the thinking will be 10 years from now, because I'd imagine the USA & China will be getting very creative to maintain a competitive edge against one another. Will a penetrating strike aircraft be viable? What if the airspace is saturated with high altitude AEW drones who can provide an air radar compliment to ground radars to help maintain the air picture? Along with squadrons of cheap on-alert drones who can be launched from anywhere to counter any invading forces. That coverage could be extended out as far as China needs in order to prevent the US from being able to get within a reasonable strike distance and due to the amount of deployed forces, it would take an overwhelming amount of missiles to cripple any infrastructure in support of it. It could become its own form of deterrence and if they are EMP-hardened, then oof.
 
Foo Fighter said:
If the NGAD program is a success, could this lead to a rolling strike aircraft to follow on from the B-21?
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The B-21 is a strike aircraft, so I'm not sure what this program you're discussing would be.
 
I am talking about a program of rolling modifications and updates which is what I understand NGAD to be.
 

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