3D-Printed Ceramics Could Help Build Hypersonic Planes (livescience.com)

An anonymous reader writes: Researchers have used a 3-D printer to make specialized ceramic parts that have overcome one of the biggest problems with ceramic objects: their tendency to crack. This new method is 100 to 1,000 times faster than previous 3D-ceramic-printing techniques, the researchers said. Furthermore, electron microscopy of the end products detected none of the porosity or surface cracks that normally weaken ceramics; indeed, these silicon carbide materials were 10 times stronger than commercially available ceramic foams of similar density, the scientists noted. "If you go very fast, about 10 times speed of sound within the atmosphere, then any vehicle will heat up tremendously because of air friction," said Tobias Schaedler, senior scientist at HRL Laboratories in Malibu, Calif. "People want to build hypersonic vehicles and you need ceramics for the whole shell of the vehicle."

Comments

Because ceramics don't get hot?

[h33t l4x0r]

Tell that to my coffee mug.

Re:Because ceramics don't get hot?

[Rei]

When was the last time your coffee mug melted?

The point isn't to stop them from getting hot - the point is to not melt or weaken when they do. Ceramics are the best materials in existence for this. For example, hafnium nitride carbide melts at 4126C. Iron boils at 2826C. And this is more meaningful than it sounds - because the only ways during reentry that one can get rid of heat are storage, ablation, and radiation. Depending on the Cp scaling factor, ablation and storage are proprortional to the temperature to the 1-2 power while radiation is proportional to the fourth power of the temperature. So being able to tolerate a given amount of higher temperatures translates to being able to dissipate far greater amounts of reentry heating.

The fact that their first material was silicon oxynitride I find interesting. I don't know how thick their layers are and whether they're able to get any transparency out of them, but thin films of silicon oxynitride are sometimes used for gradient-indexed optics - by changing the ratio of oxygen and nitrogen you can greatly change the refraction index, and thus make things like perfectly flat, thin transparent objects that function as lenses - like a fresnel lens but without roughness or distortion. And when you dope silicon oxynitride you can make phosphors of various colours. So depending on what blend of powder they lay down with the print head they may be able to use it as a rather nifty optics-printer. And since they're using UV to solidify the substance they're basically doing photolithography, aka they should be able to do very fine details. And it's a dielectric with good thermal conductivity. See where I'm going with this? Literally printing your own displays.

Re:Because ceramics don't get hot?

[Rei]

Your claim about "ceramics" in general is not true. Ceramics are a broad category with widely varying response to heating. Many are perfectly stable with numerous quick heating/cooling cycles (also note: reentry is not a "quick" process from a materials standpoint).

Ceramic parts are widely used in tasks that deal with extreme temperatures, particularly in oxidizing environments. At some temperatures they're really the only things that can take the heat.

Re:Because ceramics don't get hot?

[ShanghaiBill]

Ceramics precisely shatter when the temperature changes too quickly.

This is not true for all ceramics. Many ceramics can tolerate high heat gradients. The biggest problem with ceramics for applications like turbine blades, is that while they are lighter and stronger, they are also more likely than metal to fail catastrophically. So ceramic turbine blades are a big improvement for generators and drones, but are not yet reliable enough for manned aircraft. With these new techniques, that may change.

Re:Because ceramics don't get hot?

[fahrbot-bot]

Ceramic parts are widely used in tasks that deal with extreme temperatures, particularly in oxidizing environments. At some temperatures they're really the only things that can take the heat.

And in other areas that, at least, I hadn't considered. The shaft seal (example) in my Hayward pool pump is ceramic. Half is stationary, on the casing, the other half rotates with the shaft. The components that touch face-to-face are ceramic with rubber around the edge holding them in place.

Re:Because ceramics don't get hot?

[Rei]

Serenity's got more than a few ceramic parts in her. ;)

Re:Because ceramics don't get hot?

[Dereck1701]

Weren't one of the Space Shuttles primary thermal protections systems a ceramic (thermal tiles)? They had to survive being heated to thousands of degrees and then being plunged into cold water.

Re:Because ceramics don't get hot?

[beelsebob]

Right, I mean, that's exactly why they use them for heat resistant coatings on vehicles that need to reenter the atmosphere.

Oh wait no, that's because *you're* wrong, and certain ceramics (notably, ones without porosity, and without air or water trapped inside them) are extremely good at resisting heat and heat changes.

Re:Because ceramics don't get hot?

[Deadstick]

They had to survive being heated to thousands of degrees and then being plunged into cold water.

What cold water would that be?

Re:Because ceramics don't get hot?

[Dereck1701]

Carbon-Carbon was used on the leading edges of the wings and the nose cone, the TILES were made of high purity silica. And while during normal operations they didn't actually have to survive being plunged into water it was apparently done to demonstrate their resilience.

Extract from http://science.ksc.nasa.gov/
"For example, an HRSI tile taken from a 2,300 F oven can be immersed in cold water without damage. Surface heat dissipates so quickly that an uncoated tile can be held by its edges with an ungloved hand seconds after removal from the oven while its interior still glows red."

Re:Because ceramics don't get hot?

[whopub]

This is what I want to read about. Does this new ceramic outperform the tiles used on the space shuttle? Could they be put to that kind of use without having to be replaced every few landings? Could the 3D printing process allow for these tiles to be much bigger, as in 10 nicely shapped huge pieces put together instead of hundreds of small square angle 'bricks'? The tiles on the space shuttle were small to avoid breaking, which is more likely to happen on bigger surfaces.

Compression, not friction

[Brett Buck]

The heating is largely from compression heating the air, not "friction" in the usual sense.

Re:Compression, not friction

[jeffb (2.718)]

I'm kinda hoping that a scientist working in the field knows about this, and just figured that "compression" was too big a word for most laymen (and, increasingly, most reporters).

Re:Compression, not friction

[Rei]

It's not even that simple.... in the exosphere, it's more like individual particle collisions than like dealing with a bulk gas. And then when you get deeper you get into the atmosphere, it still doesn't behave like a normal gas - the dense compression shocks of air that you've built up in front of you that are so hot that you actually lose some of the heating energy to endothermic chemical reactions - there's a different equilibrium there than at lower temperatures. While there's enough time to reach the new equlibrium in the shocks in front of the spacecraft, in the sidestream the gas moves past so fast that it doesn't have time to reach its new equilibrium as it cools ("frozen reactions") - the reactions happen at a point well behind the spacecraft, releasing the energy there. So the spacecraft actually gets away with bypassing part of the energy it's losing to the atmosphere.

On the other side, these frozen reactions have downsides too - it's part of what makes scramjets so difficult (the desired combustion being "frozen" to past the end of the craft due to insufficient reaction time). In fact, if this didn't happen, you could potentially make spacecraft that propel themselves in the outer reaches of the atmoshere/low Earth orbit (anywhere over 100km really) without need for onboard propellant by recombining the free oxygen radicals that dominate there. (technically you still probably could, but it would require a long spacecraft indeed)

Re:Compression, not friction

[Lab Rat Jason]

Lol... I came here to say exactly this. Why any reporter would type anything these days without fact-checking it blows my.... wait... I retract my previous statement.

Re:Compression, not friction

[Coren22]

Compression? You mean reducing the dynamic range of a song?

next, ceramic drones

[turkeydance]

in the shape of an ashtray

People DON'T want this

[BarbaraHudson]

"People want to build hypersonic vehicles and you need ceramics for the whole shell of the vehicle."

Only the military wants hypersonic vehicles like this - unlike ICBMs, these would be harder to detect until they reach their targets. This will be a destabilizing factor between the east and west - and you can be damn sure China will build similar vehicles.

Re:People DON'T want this

[fnj]

Only the military wants hypersonic vehicles like this

It seems to me that a few people might be interested in flying 12,087 km from Los Angeles to Sydney in 3.8 hours at Mach 3 or 2.3 hours at Mach 5, rather than 13.4 hours at Mach 0.85. Like maybe just about everybody who flies that route or a comparable route.

Re:People DON'T want this

[BarbaraHudson]

The military has openly speculated about hypersonic delivery systems that don't need to go into orbit. Anti-ballistic missiles would be pretty useless to a target that is not on a fixed ballistic path after the original launch.

Re:People DON'T want this

[BarbaraHudson]

It would probably be cheaper to just send them by sub-orbital ballistic craft. No fighting air resistance for most of the flight.

Re:People DON'T want this

[Rei]

Let's not hate on Concorde for too much - it served for 27 years, which while certainly not record-setting wasn't a bad run. British Airways was said to have turned a profit on their runs. It was doomed by a collection of factors - the only crash of the plane in 2000 (not the design's fault, it hit debris shed from a DC10 that the airport should have cleaned up), the 2001 terrorist attacks, and a general downturn in aviation and reduced profits. Also when the plane was grounded after the 2000 accident it's said that the airlines realized that they made more money in shunting their concorde passengers into first class of their other flights - it's not like they had another supersonic plane they could just switch to.

Supersonic commercial travel will certainly happen again, and the next plane will be improved over Concorde in every regard. It really just needs a sustained upswing in long-distance commercial air travel, particularly the high end of the market. Maybe emerging markets will be the spark that's needed.

Re:People DON'T want this

[SuperKendall]

Indirectly they were; because the price per ticket is reduced with advances like this in ceramics which makes supersonic flight cheaper.

Re:People DON'T want this

[Rei]

It's not that simple with air transport because there's another factor - altitude. Altitude means thinner air, which means reduced air resistance. It's not like transport on the surface where you're facing wind or water resistance roughly proportional to the square of the velocity, there's more factors involved.

Re:People DON'T want this

[BarbaraHudson]

The Pentagon assessment disagrees with you.

Re:People DON'T want this

[joe_frisch]

I would very much want ECONOMICAL hypersonic transportation. Unfortunately I think it is a real long shot. This technology might be a minor help for one of the many problems that would need to be solved.

Re:People DON'T want this

[ShanghaiBill]

The Pentagon assessment disagrees with you.

So the Pentagon thinks more money should go to the ... Pentagon? Nobody has a greater vested interest in scaremongering about China, especially since Russia is not a scary boogey monster anymore.

Re:People DON'T want this

[Rei]

Again, not necessarily. Your average LEO satellite for example goes 7,8 kilometers every second at no incremental energy cost. Yes, it cost a lot to get it there, but the amount of energy it consumes per kilometer traveled as a whole is miniscule. The fact that there is almost no resistance there is a really big deal. You cannot simply say "because something is going faster then it's using more energy per kilometer". That's a rule of thumb but certainly not a hard, fast rule. When the forces you're experiencing change as you move into a different envelope, your energy consumption changes. And that change can be greater than the energy you burned to get into the different envelope.

Re:People DON'T want this

[Rei]

According to you, the flight takes 5 minutes and needs one drop of kerosene now?

Where did I say "20 orders of magnitude difference"? I just said your claim of "a few percent" is not at all representative.

Let's look up some stats about the original 747-100 and a new aircraft (say, the A380). On all comparisons I'll put the original 747 first and the A380 second

Price (2014 dollars): $168m/$428m

Range (same cruising speed): 9045km/14800km

Passengers (three section seating): 397/555 (with more area per passenger)

Maximum load: 142 tonnes/283 tonnes

Operating costs: Difficult to quantify, but the A380 is said to have "direct operating costs per seat 15-20% less than those for the 747-400", which is itself several generations after the original 747-100, so somewhere in the ballpark of 30-40% better is probably a reasonable guess.

Fuel cost per seat per mile: $0.138 / $0.108

Standard features list:
Boeing 747-100: Lavatory, Phone System, Reading Light(s)
Airbus A380: Bar, Cabin Lighting, Chairs: Berthing, Chairs: Moveable, Galley, Hot Water, iPod Connection, Microwave, Monitor(s), Separate Air Outlets, Soundproof Cabin, State Room, Stowable Work Table, Lavatory, Phone System, Reading Light(s)

Accident history: 3% of all 1505 747s (whole category, not just 100s) ever built have been lost to crashes. Concerning the 747-100,200,and 300 series specifically, the rate is 1.06 fatal crash per million departures. / Despite being produced for over a decade with 173 in service, there's not been a single hull loss or fatal accident with a A380, only one emergency of significance. If we want to compare to a slightly older aircraft to get more miles under its belt, the 747-400 (1988) had a rate of 0.07.

Further detail on accident histories: while it's hard to do a precise safety comparison between the two due to the different service histories, it's worth noting that the biggest advance in the airline industry in the past four decades has been in safety in general. New regulations (resulting in frequent modifications and retrofits, change in design processes, etc) have cut the rate of fatalities per million departures from around 40 when the 747-100 was launched to around 10 today.

The price of aircraft has gone up - but the TCO has gone well down, particularly because of the 30-40% improvement in fuel economy. This has also translated into much greater range for the same general plane configuration.

Your 20 orders of magnitude nonsense? Of course not. But "a few percent"? It's way better than that.

It should be added that, again, the Concorde (ignoring Russia's ill-fated effort) was the first supersonic passenger jet - a prototype, if you will. The 747-100 certainly was not. If you want to make a more proper comparison, you need to compare an A380 with a de Havilland Comet. The comet, by comparison to a passenger jet 40 years later, was a terrible, expensive, inefficient, unsafe plane. But it broke the ground for others to follow.

The same holds for the Concorde

Re:People DON'T want this

[LWATCDR]

Ahhh. No
This is also useful for space flight aka scramjet to orbit and also possibly for gas turbine blades as well as other high temp objects.
Hypersonic strategic weapons will not have a destabilizing effect at all. Just as today SLBMs will be the final deterrent.

Re:People DON'T want this

[Blaskowicz]

The internet also allows to research about dozens of flights and destinations long in advance, hostel or housing, aerial maps or even "streetview", reading about legislation in the far away country and hundreds of other little things.

Showing off is certainly done is certainly done, on asocial media.
People go to Thailand for a long vacation on unemployment money, where $1 likely buys you more than needed in dubious strong alcohol to kill you.
Communication may well obviate some of the "need", but it hugely increases the "want" and the "do".

Re:People DON'T want this

[Blaskowicz]

The problem with that is it's going to make many people nervous, particularly those manning a nation's "early warning system" or "strategic rocket forces". It is hard to tell whether that flight is a business trip or a nuclear attack. Long range hypersonic or sub-orbital weapons face about the same problem.

Re:People DON'T want this

[Rei]

The reason that a LEO satellite goes 7,8 kilometers per second at no incremental energy cost is because it's in really, really, really thin air. Which is the whole point I've been making in this entire thread: the higher you go, and the thinner the air, the less energy it takes to move through it. You don't have to go all the way to LEO, but every kilometer you increase in altitude cuts your energy consumption significantly.

And really, " Otherwise you have no reason to worry about ceramics, and can work with tin foil." - you've never heard of reentry? One of the biggest heat-challenges confronting modern engineering? Objects moving very high and fast, even if they experience little heating in-transit, experience much on return.

In the atmosphere, you can travel higher, where there is a thinner atmosphere, and you have less drag, but also less dynamic lift.

Which is why for an aircraft wanting to go faster you do one of two things, depending on how much faster we're talking about and the propulsion system:

1) Cruise at a steady higher altitude at the higher speed, such that drag and lift force remains the same - but since you're going faster , you're spending energy to overcome the drag force for less time.

2) Use your in-atmospheric propulsion and lift during ascent to arc you into a parabola. At the peak of the parabola you may have insufficient thrust or lift to maintain a steady state, but the point is not to maintain a steady state.

#1 is more optimal for the lower end of supersonic flight, #2 toward the higher end.

Re:People DON'T want this

[ceoyoyo]

The generation that was really paranoid about those things is starting to die off. I wouldn't be surprised if, in the next twenty or thirty years, we get over that particular fear entirely. If you wanted to launch a sneak attack you could put nukes on regular airliners... there's no reason for them to go fast if they're disguised. Ballistic airliners would still be easily distinguished from ballistic missiles: they'd fly trajectories that didn't spill the rich peoples' drinks. Finally, there's not much point in worrying about a first strike because if it did happen there's not much you could do about it and your submarine launched missiles would be unaffected.

Re:People DON'T want this

[Rei]

Unless people start making ballistic missiles that look like airplanes, they're going to have very different radar signatures.

If a country doesn't trust another to not hide their missiles as aircraft, then they won't allow ballistic aircraft transit with that country. The US could still allow ballistic aircraft with, say, Britain while not allowing it with, say, Russia. To get permission to launch, every flyover state would have to give permission - which they wouldn't give if they had fears of a concealed nuclear attack.

Re:People DON'T want this

[Rei]

Scramjets are rather difficult to orbit. But they are rather interesting for high speed suborbital flight. They let you go through some very thin, high air, very fast. It's also possible to use them for launching into even higher parabolas where they can't fly steady-state, but just drift with nearly no resistance on their way to the destination.

Re:People DON'T want this

[BarbaraHudson]

You know that it's getting easier to track submarines ... eventually they will not be immune to a preemptive first strike. Plus there are ABM systems, which are improving.

Re:People DON'T want this

[LWATCDR]

Scramjets can get very close to orbital speeds so all that is needed is a small booster to put you into a stable orbit.
Yea people want this for any number of devices. The fear on Slashdot at times borders on the level of fear of Trump supporters.

Re: People DON'T want this

[alva_edison]

Google puts it at about 36 THB to 1 USD, a draught beer costs about 100-150 THB, so 3-5 USD. Rough estimate. That puts the economies for alcohol roughly on par with Thailand maybe a little cheaper.

Re:People DON'T want this

[KGIII]

I presume that AC is unfamiliar with your posting history and style. Very few of your comments are opinions that don't seem grounded on a whole bunch of numbers, history, and logic. In other words, you're generally able and willing to support anything you've said with actual data as opposed to "generally accepted wisdom" or the likes. If they're unwilling to bring a bunch of data to the debate, I'm unsure why they'd bother.

Re:People DON'T want this

[KGIII]

Somewhere, in the dark recesses of the Pentagon, lies a filing cabinet. Inside that filing cabinet are plans, updated from time to time, about how to attack or what to do in the event of an attack. In there, are things like assessments of power and capacity to wage war.

That said, we have plans to invade Canada and counter-plans with responses of what to do when Canadians zerg-rush the border of Maine to steal their maple syrup, foliage, and blueberries.

Re:Useful for President Trump's wall, too.

[U2xhc2hkb3QgU3Vja3M]

How about a wall for the northern border too, eh?

Re:Useful for President Trump's wall, too.

[NEDHead]

If Trump wins, the Canadians will take care of that

Re: Useful for President Trump's wall, too.

[tysonedwards]

âoeThis is a wall. Sorry, buddy, nobody allowed in. Look, thereâ(TM)s just some really cool shit back here and we donâ(TM)t feel like sharing it.â Sincerely, Canada

Re:I want this!

[BarbaraHudson]

That also makes it more likely that somebody would take a preemptive first strike.

Less porosity = less insulation factor

[Chas]

Basically part of what the ceramics are doing is insulating components underneath from the heat and friction.

If the ceramic compound is less porous, there's less air space in there. Which means less thermal isolation.

So the ceramic compound goes from being a thermal insulator to a thermal mass.

You REALLY don't want that kind of thing on a hypersonic vehicle.

Re:not air friction

[TapeCutter]

Compression = Bashing atoms together until photons fall off.

Friction = Bashing atoms together until photons fall off.

Re:Useful for President Trump's wall, too.

[Lab Rat Jason]

Don't you mean Supreme Chancellor Trump?