Submitted by lughnasadh t3_10iq1ok in Futurology
This title is super click-baity and almost a blatant lie. If you read the article, its still powered by a regular old gas turbine (aka jet engine, which are far from simple and definitely have moving parts) but the thrust is directed by something similar to what you see on a Dyson fan, instead of a traditional nozzle like most aircraft.
Obviously it needs a compact, high powered engine. In aviation this means gas turbine.
However, this is absolutely an innovative way of delivering that power. Turboprops are efficient, but require complicated gearboxes. Jets are noisy and inefficient, unless it’s a turbofan, but those are big.
This is like halfway between a jet and a turboprop.
My point was that the title of the post is incredibly misleading. I'm not saying that it's not a good idea or that it won't work. Just that it's not some magical solution.
I dunno, coming from military aviation it’s a good title.
Like, clearly it needs a power source, and clearly that’s a gas turbine engine. But putting power down, efficiently, without a gearbox or transmission is revolutionary.
Edit: also for people who are worried about that kind of thing, you can make this green / zero emissions. Solar powered ammonia production is ramping up quickly, and ammonia is an easy substitution for gas turbine engines. Loses about 30% energy density over jet fuel, but it’s workable when range isn’t a limiting factor.
It's not a good title at all. A gas turbine is not some "new type of engine" and they definitely aren't "bladeless" so I don't know why you think that.
30% less energy dense is a hell of a lot since range is always a limiting factor in aircraft. I don't see that becoming a commonly used fuel in the industry.
https://aviationh2.com.au/liquid-ammonia-is-the-carbon-free-fuel-of-choice-for-aviation-h2/
If you run the numbers for a typical jet design, carrying 30% more fuel for range is fine for medium range sorties. Anything over ~10h will probably require some kind of biodiesel fuel, but sub-10h in an A330 or long range private jet is very workable.
And as more countries force carbon emitters to pay for their negative externalities via tax, green fuel will become cost competitive. With cheap solar, ammonia should be similar cost to current jet fuel prices, so it'll be significantly cheaper. Western Australia and other places are setting up huge green energy projects for cheap ammonia and hydrogen fuel.
Also, given the increasing protest movement against private jet emissions, people will be willing to pay extra for green fuel. Hell, if I ran PR for an ammonia aircraft startup I would be doing everything I could to encourage protests...
Most aircraft don't have the space for more fuel tanks to carry 30% more fuel so there's a big issue with that right off the bat. Also that increases the weight of the aircraft, not just from the fuel itself as the airframe will have to be strengthened to carry the extra weight. Weight is by far the most important limiting factor when it comes to range so if youre looking to fly very far at all. Carrying 30% more fuel is a huge issue for most types of aircraft and is not gonna cut it.
Have you done ATPL flight planning? Most commercial jets operate economically on routes that are much shorter than their max range.
Plenty of 787s are doing NY-LAX.
I believe this is what u/slowslownotbad was referring to in their previous comment when they spoke on the 30% efficiency decrease
Isn't that also because the pilots have to have surplus fuel for their alternate landings as well as possible holding patterns due to emergencies or priority changes?
Yeah, alternate fuel stuff seems complicated but it's basically a scenario-based planning exercise. Like, I'm gonna do a long overwater flight to a remote destination, so I need gas for depressurization or single engine failure or weather holding/divert. I'm legally required to carry gas for certain things at certain times, and I can add extra if I want to. But I need to plan to arrive at a low enough fuel state that I can land below maximum landing weight.
That last point is gonna be most limiting for ammonia fuel in certain missions; because NH3 is less energy dense, it will require pilots to routinely land with a greater fuel load of unburned contingency gas. This will cut into usable payload.
So it's not a perfect solution, but it's got tonnes of promise.
Not a pilot, but yes they do take extra fuel. I believe it's like 5% of the trip total as extra for taxiing and weather reroutes, plus enough to get to an alternate airport if your destination is not viable. Plus aircraft carry an emergency reserve of 30 minutes worth of flight time. If you break into that last bit, you're likely declaring an emergency and ATC will give you priority sequencing to land.
You want to have enough for safety and wiggle room, but not just full to the brim as that's a lot of extra weight to carry around, which means you burn through fuel faster.
You're assuming that aircraft are already filled up to max, and thus would need extra tanks and being reinforced to hold them, etc.
That's just a wrong assumption though.
Take most any flight within Europe, or even coast to coast US like JFK to LAX as u/slowslownotbad mentioned. These flights run a couple hours, 5 tops, right?
Now let's look at an aircraft like the 737-800. It burns ~5,000 lb of fuel per hour, with a max capacity of 46,000+ lb. A 5hr flight would burn 25,000 lb of fuel. You take enough fuel onboard to get to the destination, plus an extra amount in reserve (startup, taxiing, weather diversions, holding pattern at destination), and then enough beyond that to get to an alternate airport if you can't make the planned destination.
For the sake of argument, let's say that added up to 30,000 lb. That still leaves 16,000 lb empty on the longest continental flight. That right there is beyond the 30% increase we are talking, so it's not crazy to think that airlines could switch over to a greener fuel on flights under certain distances. They'd have the capacity.
I'm not arguing the rationale that there are plenty of routes where this is possible. What I'm saying is that there is a huge penalty in the max range of the aircraft, and that makes them much less versatile, limits their route options, and are much less attractive to airlines. You're much more likely to see alternative fuels such as compressed hydrogen used (Rolls-Royce has already run an engine on hydrogen) than you are to see something used that would result in such a huge range penalty.
But even if airlines were to transition over just their short haul flights, that would make a huge difference in terms of fuel/emission savings. It doesn't have to be all or nothing.
When I worked in ATC I learned that airlines (here in Canada, at least) drafted up 3 flight plan proposals for each flight. One was the shortest time, one was the most fuel efficient routing, and one was the cheapest (considering fuel and ATC charges for how many sectors you cross, etc).
I'm sure it wouldn't be hard to factor in alternative fuels when making those calculations.
To add to my previous comment, taking the 787 Dreamliner that someone else had mentioned, you're talking a max capacity of 223,000 lb, and maybe 10,000 lb an hour. Flying JFK to LAX is a joke with that capacity. Definitely room for a less dense fuel in those tanks.
> they definitely aren't "bladeless" so I don't know why you think that.
It's "bladeless" in that if you're a life-flight medic you don't have to worry about a blade lopping half your head off.
If you took the propeller off of turboprop aircraft it would be extremely safe, even arguably "bladeless" even though the turbine has blades inside of it.
It's a bad headline, but it's closer to the truth than I think you're giving it credit for.
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Conventional turbofan engines don't have a gearbox or transmission. The closest thing they get is that they might have two or at most three shafts for their turbine/compressor stages.
That's true. The main advantage of this over a turbofan is size - efficient turbofans are quite large.
To be fair, small turbofans do exist, but they're not very efficient. For instance, a cruise missile engine might do 0.683 lb/lbf/h (https://en.wikipedia.org/wiki/Williams_F107).
Whereas Jetoptera claims as low as 0.26 lb/lbf/h (https://jetoptera.com/products/). FYI smaller is better, so Jetoptera is claiming better than 2x efficiency when compared to a small turbofan.
>That's true. The main advantage of this over a turbofan is size - efficient turbofans are quite large.
The main advantage of this over a turbofan is that it can be rotated to offer VTOL or STOVL options.
Pretty easy to rotate a relatively low velocity duct vs rotating an entire turbofan or creating a complex orbital gear to deliver the turbine power to the fans. (See: complicated clutch issues with the F35 VTOL.)
Yeah, it sounds like the plane will pop a CO2 cartridge every time it needs thrust.
Or depending on the size of the craft a battery.
Oddly enough, and I’m not talking out of my ass (Licensed aircraft powerplant mechanic) a jet turbine is easier to work on than any reciprocating/piston engine in my opinion. Simplicity is what makes turbine based power plants so reliable. Sure to someone who’s not mechanically inclined it would seem so but it’s actually very simple.
I agree, turbines are simple compared to piston engines. They aren't "almost no moving parts" simple though. My point was that the title of the post was misleading about the power source, as if they'd invented a new type of engine or something, which isn't the case. I am fully aware of how reliable turbines are I was just disappointed once I read the article based on the title.
>They aren't "almost no moving parts" simple though
The people who say this conveniently omit the myriad of valves and pumps and switches and mechanical computers (or computer computers) and bearings and fluids and reservoirs that are required to safely feed fuel to the engine, manage its airflow/temperature/RPM/acceleration/pressures, and lubricate it.
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>but the thrust is directed by something similar to what you see on a Dyson fan
Minor correction since we're trying to correct misleading headlines: the thrust isn't from the gas turbine, the air passing through the turbine is simply exhausted. The thrust is from a cold air compressor driven by the turbine shaft. So it's like a turbine powered helicopter or turboprop aircraft in that the turbine is used just like a piston engine purely for mechanical energy.
That's one of the features that the creators are advertising: the thrust is cold and relatively safe, like rotor wash vs standing behind a jet.
Also theoretically with breakthroughs in battery technology, you could skip the turbine entirely. The technology itself isn't reliant on turbines. They could use any power plant: piston, electric motor, Mr Fusion-- anything that can power a compressor.
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