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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."
The heating is largely from compression heating the air, not "friction" in the usual sense.
in the shape of an ashtray
If Trump wins, the Canadians will take care of that
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.
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.
Shiny New Australia.
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
Thirty four characters live here.
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.
Shiny New Australia.
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.
Shiny New Australia.
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.
The Pentagon assessment disagrees with you.
"Transparent" is a shit show that trades on every stereotype going. A man in drag is NOT a transsexual.
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.
Serenity's got more than a few ceramic parts in her. ;)
Shiny New Australia.
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
Shiny New Australia.
They had to survive being heated to thousands of degrees and then being plunged into cold water.
What cold water would that be?