Electric Vertical Take-Off Aircraft Successfully Tested By DARPA (newatlas.com)

Slashdot reader drunkdrone tipped us off to some big aviation news: After several years of development DARPA has successfully completed flight-testing of one of the most novel, and odd-looking, aircraft designs we've seen in some time -- the sub-scale electric X-Plane. After calling for an innovative new approach to an aircraft with vertical takeoff and landing capabilities, DARPA awarded its Phase 2 contract to Aurora Flight Sciences in early 2016. Aurora's design includes 24 electric ducted fans, 18 on the main wings and six on the smaller front canards. Both the main wings and the canards are designed to tilt upwards for vertical takeoff before rotating to the horizontal for regular flight... The prototype was also used to trial a number of other technologies DARPA has been developing, such as 3D-printed plastics for flight structures and aerodynamic surfaces.
The article includes video of the test flight, and reportedly the aircraft also successfully tested "sustained hovering." DARPA will now begin officially developing a full-scale aircraft, which has been designated "the XV-24A."

Comments

Electrical AND 3D-printed?

[Anonymous Coward]

Share and Enjoy!

Re:Electrical AND 3D-printed?

[Anonymous Coward]

Except for the fact that there is no aircraft here, just a model, sure, it's the 3D printed future...

Re:Electrical AND 3D-printed?

[DontBeAMoran]

Even if it's a model doesn't it qualify for the term "aircraft"?

Re:Electrical AND 3D-printed?

[Anonymous Coward]

Sure, but these 3D printer fanatics make it sound like the entire thing was 3D printed in their living room and ready to transport 140 people right after it's done printing.

There is no such thing. Anywhere.

Re:Electrical AND 3D-printed?

[Megol]

Not "just a model" as the FA states that the aircraft did in fact take off - so a flying aircraft, not a model of one.

Re:Electrical AND 3D-printed?

[Megol]

Couldn't you just have stopped yourself before posting such an obvious strawman?

Re:Electrical AND 3D-printed?

[Anonymous Coward]

So please climb aboard it and tell us how it's not a model.

Re:Electrical AND 3D-printed?

[Anonymous Coward]

Wow, all this time making RC model aircraft, I didn't know it wasn't actually models because they flew.

Re:Electrical AND 3D-printed?

[Anonymous Coward]

Ah, but it's a 3D printed strawman!

Re:Electrical AND 3D-printed?

[LifesABeach]

Some thoughts occured to me while RTA:
- I'm curious about the air time. Could Tesla batteries be used here?
- Speed is nice, but after 90 minutes one has to deal with the first law of bladder.
- A non DARPA issue is battery recharge time.
- Maybe Amazon could further develop this?

Re: Electrical AND 3D-printed?

[Anonymous Coward]

Aren't they models because they are trying to look like a larger scale aircraft?

Re: Electrical AND 3D-printed?

[Anonymous Coward]

This is trying to look like a hypothetical larger scale aircraft that only exists in artist's renderings.

So what's the range of the full size prototype?

[wisebabo]

So while TFA says the full size version will go 300 knots (345mph) and be able to carry 40% of its 12,000 lb. weight as payload, it doesn't mention the range.

If it's at all decent, the implications of these VTOL aircraft (with better batteries) should be obvious to all. Coupled with a always on autopilot (with the only user control being redirection or emergency landing) it could transform commuting (assuming a really good air traffic control system).

The world is really looking like a blade runner future complete with constant precipitation from climate change, genetically modified humanimals from CRISPR-cas9, off world colonies from Space X and now VTOLs. We're even (especially) headed for the tremendous inequalities in wealth (also in Elysium and Avatar).

Let's just hope this isn't a prelude towards a Terminator or even a Matrix future because I doubt there will be any reason for the machines to keep us around (no bio-catalyzed cold fusion I'm afraid).

Re:So what's the range of the full size prototype?

[Anonymous Coward]

You really need to cut back on your consumption of sci-fi and fantasy, you're beginning to lose touch with reality.

Re:So what's the range of the full size prototype?

[DontBeAMoran]

We keep re-defining "reality" every day. Maybe you're the one who's lost touch?

Re:So what's the range of the full size prototype?

[jamesborr]

Probably limiting by the hydrocarbon based fuel carried onboard, per: "A few improvements are slated to be incorporated into the full-scale model, most notably a hybrid turboshaft engine to drive the electric generators powering the fan units, as opposed to simple batteries used in the demonstrator model."

Re:So what's the range of the full size prototype?

[Anonymous Coward]

Um, let's see. I am a human being composed of water and complex molecules. Like everyone else alive now, and alive a thousand years ago. I need air, food, and water. Gravity and proper temperature. Outside I see the same planet, the same Sun. I see streets, houses, and cars. None of these things have changed much.

We can communicate a bit better, and can entertain ourselves to death. In about 4 hours, you will need to eat. That is reality. Nothing has changed.

Someone made some pictures on a computer describing a vehicle that will fly in the air... Like an airplane? We've had those for a hundred years now.

So, tell me again how reality is "redefined" *every day*?

Remember, Haldol takes hours for maximum effect.

Re:So what's the range of the full size prototype?

[Anonymous Coward]

Science fiction has become reality, at least in the minds of the dip shits buying this BS. "Happiness: we're all in it together!"

Re:So what's the range of the full size prototype?

[swb]

I'm guessing the turboshaft is meant to provide take-off power and it can cruise on batteries in a kind of winged flight mode? Otherwise I'm not seeing the advantage of a turboshaft given the energy losses associated with electric generation.

Re:So what's the range of the full size prototype?

[wonkey_monkey]

Will there also be half-naked 1982 Darryl Hannah?

Re:So what's the range of the full size prototype?

[dunkelfalke]

the transmission is the advantage. look up how large and heavy (and unreliable) helicopter gearboxes are.

Re:So what's the range of the full size prototype?

[jamesborr]

Agree -- just don't assume that a production version of this won't be pulling up to the Jet-A dispenser to deliver reasonable operational ranges. Might we someday end up with batteries that are as energy dense (volume and weight) -- certainly that is the hope, just not necessarily reality as yet. Even when that stage is reached, time and ease of charging is still going to be a concern (i.e. "portable" military facilities for this kind of aircraft are not likely to be next to a decent sized electrical sub-station) -- meaning that diesel powered electrical generators will likely be the norm, and time to "re-fuel" will need to be measured in minutes and not hours...

Re:So what's the range of the full size prototype?

[blindseer]

I'm guessing as you are but the way I understood it is that the electrical power would be provided by a turbine engine driving a generator. No batteries, or at least none that drive the propellers.

Batteries have very poor energy density compared to hydrocarbons, a difference of 2 or 3 orders of magnitude. I expect that the prototype used batteries because range is not an issue for testing but cost is.

When it comes to the losses of electric generation we've seen the advantages of an electric drive train for over a century now. Nearly every locomotive has an electric drive train. An increasing number of ships at sea do as well. As we come to demand better performance from our automobiles we've been switching to electric drive trains there as well.

Re:So what's the range of the full size prototype?

[blindseer]

As this is a tilt rotor aircraft I would think that a more appropriate analogy would be with the V-22 and aircraft like it. Or even with other VTOL aircraft, such as the V-8 (Harrier derived craft) or F-35B (lift fan variant).

What we've had before were two classes of aircraft, helicopters and airplanes. Helicopters could take off and land on small areas but were slow and fuel hungry. Airplanes used much less fuel per mile traveled and/or mass carried but at the cost of needing a large take off and landing area.

Tilt rotor craft allowed one to create an aircraft that had speed, small take-off/landing area, and fuel efficiency, but at a cost of complexity and reliability. The V-22 is a very well liked aircraft but it has high maintenance costs from its complex gearboxes. If this experiment is successful then the cost penalty for VTOL airplanes can become very very small. It's not likely to make traditional helicopters and airplanes obsolete but it will replace many of them in many cases.

Re:So what's the range of the full size prototype?

[Anonymous Coward]

Efficiency in energy transfer from the shaft to the EDFs (electric ducted fans) is very high with AC motors (~95%) and high performance rotary generators (up to 99%).

The advantage of a turboshaft setup is the savings in energy storage weight. Jet fuel has 50-100 times the specific energy of lithium ion batteries (https://en.wikipedia.org/wiki/Energy_density). Plus, the jet fuel gets burned and ejected in flight, so the aircraft reduces its weight over the course of the flight.

The typical use of batteries and engines in concert is actually the opposite of what you described. Some experimental aircraft have used small battery banks to supplement power at takeoff so that the engine can be designed for max efficiency at cruise power and altitude (cruise is often only 50-75% of takeoff/climb power).

This particular aircraft uses a turbine-electric drivetrain to take advantage of the efficiency increase provided by distributed propulsion (increases the lift over a wing by ~100-500%) and ducted fans (can as much as double propulsive efficiency vs. an open rotor). Also, there's another NASA x-plane in development just to explore the benefits and applications of distributed propulsion.

There's also a *lot* of other clever stuff they've done, like varying the fan blade angles to change the load on the electric motors instead of using massive Electronic Speed Controllers and DC electric motors. Saved ~900 lbs in hardware/wiring and increased electrical efficiency.

The aircraft was designed for the x-plane program's goals of increased 1) speed, 2) range, 3) hover efficiency and 4) payload fraction vs. a traditional helicopter.
So far, it's met all those goals and beat out the entries from Sikorsky, Boeing and Karem for the VTOL X-plane program. The biggest technological hurdle yet to be overcome is creating miniaturized 1 MW generators, but they seem pretty confident about them. Range should be significantly superior to helicopters, probably on par with or beating the V-22 (adjusting for scale, of course).

It's important to note that this is a technology demonstrator. You'll probably never see something exactly like this in the US VTOL fleet, but the leaps in technology and new designs will show up in other aircraft in a couple generations.

source: a couple long chats with an Aurora test engineer and the Aurora chief engineer and a very thorough update that Dr. Bagai (DARPA project manager for the VTOL X-Plane program) gave a couple weeks ago. (All public knowledge, just not published widely outside the technical community)

Re:So what's the range of the full size prototype?

[swb]

It sure hasn't hit the recreational marine market, though. You can get pod drives, but they are mechanically driven off of diesel engines.

I always wondered if they could do a hybrid drive on a boat with a single engine and batteries driving electric motors. I'm only aware of one (newish) maker doing it, but I would think for a lot of the inland boating market where ranges under 25 miles and cruise speeds of 10 knots are common.

The batteries would be a wash if you removed one of the engines and less fuel might offset a heavier generator.

Re:So what's the range of the full size prototype?

[blindseer]

The batteries would be a wash if you removed one of the engines and less fuel might offset a heavier generator.

That does not seem likely to me. We design aircraft with multiple engines because it provides redundancy and convenience. Two engines are nice because they can derive power from a shared energy pool, the fuel tanks. With a single engine and a battery pack the loss of the engine means losing access to that pool of energy that is the fuel.

Then there is the issue of charging up that battery. Given proper infrastructure the battery could be charged from grid power. In the case of remote locations, or emergencies, the grid power cannot be relied upon. In which case the electricity would come from diesel generators and the like. In that case the batteries would be charged from a generator as part of the ground crew tools, have to be charged from the engine on board using fuel while idle on the ground, or whatever. The energy would still come from the fuel but with the additional losses of charging and discharging the battery.

If a battery-turbine "hybrid" plane did suffer a failure of either power plant, the turbine or battery, then parts for both would have to be kept on hand. With a two engine craft a power plant failure would typically mean replacing the engine with one that can fit in either spot. It's the low replacement part count that keeps aircraft like the A-10 in the air. The A-10 has very few parts that are unique to left or right. There is no "left wing" or "right wing" there's just "wing".

A friend of mine worked as ground crew servicing F-16 jets, which has one main engine. A twin engine craft can use power from one engine to restart the other, but a single engine craft does not have that option. There is a battery on board of the aircraft but that is only for navigation and communication. If the engine is in need of restart in the air, or with a lack of proper ground equipment while on the ground, there is a small powerful engine on the plane that can start the main engine. I recall that it runs on hydrazine but I'm not sure about that. Even so there is only enough fuel for the auxiliary engine to attempt two or three engine starts.

The point is that even with an electric drive system the poor energy density of batteries do not make sense to drive the engines. Electric passenger commuter cars can get away with using battery storage because ranges are short and charging stations are easy to find. Not having to get airborne, or stay afloat, helps considerably too.

Re:So what's the range of the full size prototype?

[blindseer]

Might we someday end up with batteries that are as energy dense (volume and weight) -- certainly that is the hope, just not necessarily reality as yet.

I'm pretty sure that will never happen. That is assuming one defines a battery as we understand it currently, a device that stores electric energy directly as a reversible chemical process. What some people call "batteries" are really just capacitors or fuel cells that have a form/fit/function similar to a battery, and even then I'm not sure we'd see anything better.

Jet-A is an incredibly dense energy source that is a liquid at temperatures and pressures that we will commonly run into. This means it can be stored in something as inexpensive, durable, and lightweight as a steel tub or plastic bottle. It has other nice properties such as it's ability to lubricate and preserve metal parts, and that it's relatively difficult to ignite in case of an open flame.

Jet-A is really hard to beat as a fuel.

Re:So what's the range of the full size prototype?

[swb]

I was thinking of a specific use case -- inland lake recreational marine. A plane is a different animal, as is ocean-running boats.

The lake I boat on is pretty big -- 22 square miles comprised of a dozen or so interlocking bays, but you would be hard pressed to run more than 30 miles of traveled distance in a single day.

For this specific application, I don't see why a single engine hybrid, diesel-battery-electric application wouldn't work. Half the boats on the lake are single engine and a total engine failure isn't exactly life threatening, either.

Most days we don't travel more than 10 miles, a range a Tesla-size battery could provide about 6 knots of cruise on a 30 foot hull pretty easily. Many slips have 30A service for charging and an on-board diesel generator for charging and diesel-electric propulsion would extend the range to fuel on board.

I'm only aware of one commercial option, Greenline Hybrid, which uses a single diesel and batteries but it puts the prop, combination motor/generator and diesel on a single shaft with a hydraulic clutch to operate as prime mover and generator as well as having about 6 hours of cruise at 6 knots on battery alone. They also have a model with 1.3 kW solar panels which they claim can actually drive the entire thing (albeit slowly, like 3 knots).

If I had the money I would be inclined to find an good hull with worn out engines and roll my own for this use, but see if I could make it pure electric drive with the diesel only for electric generation.

Re:So what's the range of the full size prototype?

[Baron_Yam]

>I was thinking of a specific use case -- inland lake recreational marine.

There's a fun English show about these guys who travel around finding ways to use renewable energy sources to replace traditional hydrocarbon based ones. It's fun because they do the planning, building, and testing right in front of the camera. (Sorry, I can't recall the name right now).

Anyway, one job they did was a solar-powered water taxi. I believe the batteries ended up being ballast to counter the roof of solar panels they put on the thing. Or I may be mixing up two different boat-based episodes.

Regardless, they had an electric boat going one way or the other, for a commercial (though small scale) application.

Personally, I'd have a shore-based charging station rather than carry what amounts to a huge wind-catching weight above the center of mass of my vessel... and I'd want a really good bilge pump because I think filling the boat with enough foam to ensure you'd stay afloat if you took on water would mean no usable interior space.

Re:So what's the range of the full size prototype?

[swb]

The solar installs I've seen on boats amounted to flush mounted over cockpits or other roofline enclosures. Nothing to catch the wind.

Other than the one Greenline with 1.3kw solar, for most purposes solar on a boat is only really useful for offsetting DC consumption for house batteries -- a couple hundred watts -- not propulsion, unless you're doing some really unusual purpose-built solar boat.

Shore charging is fine, but you'd really want diesel generation for both higher running speeds than batteries can supply and for distance. Plus you'd need it anyway for house power.

I think a battery array install along the keel line in the bilge would be ideal, and a lot of larger fiberglass hulls end up with lead there anyway for ballast. They wind up being sort of tall for their typical running weight and more mass at the keel line in the bilge does a lot to help counter rolling at anchor and makes stabilizers much more effective.

Yeah, but the extension cord limits range

[Anonymous Coward]

to a few hundred yards.

Re:Yeah, but the extension cord limits range

[Areyoukiddingme]

Yeah, but the extension cord limits range to a few hundred yards.

I've got two extension cords. Twice the range! At this rate I'll have a flying car with a range that covers the city after just a few hundred dollars at the hardware store!

Re:Yeah, but the extension cord limits range

[dwillden]

And that just brings an image of a massive Traffic "Tie-up", with dozens of miles long extension cords all balled up in a massive knot.

Kill that fucking music!

[fustakrakich]

And let us hear what the damn thing sounds like.

Re:Kill that fucking music!

[ChrisMaple]

Whoosh

Re:Kill that fucking music!

[Anonymous Coward]

Presumably the music is there for a reason... I bet it's noisy as hell.

Re:Kill that fucking music!

[wonkey_monkey]

Don't know how modded you troll. Sound is going to be an incredibly important factor in getting something like this off the ground, as it were. As I understand it, jets have been getting significantly quieter over recent years, and this has allowed air travel and airports to expand where previously it wouldn't have been allowed.

Re:Why?

[Anonymous Coward]

Just to acknowledge Mark Miller at the comments section, in the linked page makes better considerations about conversion (I had not read it previously, my bad).

Re:Awsome. But what does it do

[petes_PoV]

Hopefully the scaled down (from the design target 5 tonne) vehicle will sit in my back yard, get plugged into mains power to recharge itself and take me to work every day.

Nice to see some perspective

[Anonymous Coward]

This is the truth, folks, not, 'Drones are delivering babies via Alexia!'. Technology is not operating on par with the year 2525 as Musk and the other techtards would have you believe. Cool stuff, unlike millennials, some of us actually *enjoy* reality. Being honest about the present is the only way to move forward, in fact.

Re:Why?

[SlaveToTheGrind]

So that we know how that compares to a boat? (knots)

No, so that we know how that compares to other aircraft. Airspeed has been measured in knots since well before you were a gleam in your parents' eyes.

Re:Awsome.

[Anonymous Coward]

Um, excuse me, we are re-defining reality every day and we will soon live like in Bladerunner and mining asteroids. 3D printers.

Because your utopia is a failed dream

[Anonymous Coward]

Your utopia is a failed vision. Your dreams of forcing Americans to conform to your vision are stupid. Simply put, we won, and we keep winning. Winning economically and culturally.

Re:Because your utopia is a failed dream

[Anonymous Coward]

> Simply put, we won, and we keep winning. Winning economically and culturally.

You elected Trump.

I rest my case.

FTFY

[s.petry]

So that we know how that compares to a boat? (knots)

No, so that we know how that compares to other aircraft. NAVAL Airspeed has been measured in knots since well before you were a gleam in your parents' eyes.

Naval aircraft is an exception, other aircraft traditionally use MP/h and KM/h.

Re:FTFY

[fisted]

MP/h and KM/h.

+5, Troll

Re:FTFY

[dunkelfalke]

Sure about this?
http://tfmlearning.faa.gov/Pub...

According to this document, knots are used for aircraft (optionally Mach numbers above certain flight level).
USSR used km/h, though. I think Russia still partially uses km/h because on Soviet built aircraft this is what flight instruments show.

Re:FTFY

[K. S. Kyosuke]

And they don't anymore? I just checked on some of our local regulations and the preferred unit is km/s, with knots being temporarily but indefinitely (someone was being clever!) allowed (or rather tolerated?).

Re:FTFY

[dunkelfalke]

Looks like this is the case. The SSJ cockpit is in English, so I guess it uses feet for altitude and knots for airspeed and besides it uses a lot of the same avionics that Airbus uses. This is so far the only passenger airplane Russia has developed after 1991 since the upcoming MC-21 still hasn't had its first flight.

Re:FTFY

[SlaveToTheGrind]

I'm a private pilot, friend -- you picked a bad time to get cocky.

You're sadly wrong, and about 60 seconds of research will confirm that. Feel free to try that before sticking your foot in your mouth next time.

Re:FTFY

[Anonymous Coward]

maybe in your special world they do, in the real world, Airspeed is indicated in Knots and altitude in feet

Re:FTFY

[s.petry]

Liar. You being able to find conversions does not mean that is how the specs are written. Specs on all US Aircraft, except Navy, are released and spec'd for Mp/h and range is given in Miles then converted to Kilometers. Range for Navy aircraft are given in Nautical Miles, but Mp/h first and conversions to Knots and Km/h. I have worked around the industry since the early 80s dumbass. Go try to look smart at a Junior high where people may believe you.

Re:FTFY

[s.petry]

Aviator guides are not the same things as design specifications, which use Mp/h as the guide. Again, the exception is the Navy who uses knots for specifications. Knots and Km/h are conversions on land based crafts, which is an easy thing to do when you know Mp/h.

Re:FTFY

[SlaveToTheGrind]

Liar.

Hey, you're the one that got caught with your hand in the cookie jar.

You being able to find conversions does not mean that is how the specs are written.

And you being able to Google random stuff and paste it in here doesn't mean that's how the industry works.

Try looking at a few actual airspeed indicators in real live planes (as opposed to "working around the industry," whatever that means -- perhaps your office was near an airport?) and report back what units you see printed on the vast majority of them. Next, take a look at airplane performance specifications and report back what units are typically used for, e.g., "cruise speed," "max speed," "stall speed," etc. For even more bonus points, try cracking open the FARs and see what default units they use for airspeed. Do be sure to get back to us with your findings.

But since blowhards like you are incapable of admitting when they're just flat out wrong, I won't be holding my breath.

Does this really exist?

[Anonymous Coward]

All I see are artists impressions.

Reminds me of Tesla Model G.

[Anonymous Coward]

The G stands for GAY IDEA. Who would be retarded enough to fly/ride in THAT?

Re:Why?

[Anonymous Coward]

Please see my colorful remark about tradition in my original post. Alas, "has been measured since..." equates to tradition in my lingo.

Seriously, while avoiding the urge to offend you, let me mention what's been said before: "if you do what you've always done, you get what you always got".

Knots is, frankly, beyond useless: it actually hampers communication. And mph is in the same league: let's face it, it's useless in 90% of the world countries (considering that 10% still can understand miles, though with differing sizes).

Links:
http://www.zmescience.com/other/map-of-countries-officially-not-using-the-metric-system/
https://en.wikipedia.org/wiki/Mile

Why Don't You Educate Yourself, Shitlord

[Anonymous Coward]

Knots are the standard measure of speed in both the aviation and maritime industries, globally!

Why don't you educate yourself, shitlord.

Re:Why Don't You Educate Yourself, Shitlord

[Anonymous Coward]

> Knots are the standard measure of speed in both the aviation and maritime industries, globally!

Well, Google does not think so (at least, in the last year):

https://trends.google.com/trends/explore?date=today%2012-m&q=aircraft%20mph,aircraft%20knots,aircraft%20km%2Fh,aircraft%20mach

See also:

https://trends.google.com/trends/explore?date=today%2012-m&q=airplane%20mph,airplane%20knots,airplane%20km%2Fh,airplane%20mach

And:

https://trends.google.com/trends/explore?date=today%2012-m&q=plane%20mph,plane%20knots,plane%20km%2Fh,plane%20mach

So much for your knots theory...

> Why don't you educate yourself, shitlord.

Very curious, coming from a country unable to use the units that EVERYBODY ELSE AND THEIR DOG uses.

Re:Why Don't You Educate Yourself, Shitlord

[Anonymous Coward]

I don't think that the search keywords of morons, used for Google trends, are what are used for global aviation industry standards.

Airspeed is measured in knots, up to 250 knots. Past 250knots, the preferred unit of measure is Mach.

You shitbird.

Re:Why Don't You Educate Yourself, Shitlord

[Anonymous Coward]

I just did entrance exams for air traffic control, and it was all in knots.

Cheep bike

[AndyKron]

For $19, the price of the "lock" + universal key, a thief can have a nice bike. Noted.

newatlas blocks adblockers - do not link to them

[nyet]

Just go to the source.

newatlas sucks - if you run an adblocker, it won't let you access any of their stories.

http://www.darpa.mil/news-even...

Re:newatlas blocks adblockers - do not link to the

[technosaurus]

just another way slashdot is trying to subtly modify our behavior.

How well does it scale?

[knorthern knight]

This could be a showstopper. Simple explanation...

* when you scale up a propeller-driven aircraft by a factor of N, the area swept out by the propeller(s) increases by a factor of N^2

* but the craft's width, height, and length each increase by N, so the aircraft's volume, and therefore weight, increases by a factor of N^3

Double the scale of the aircraft; propellors sweep out 4 times the area, but the body weighs 8 times as much

Triple the scale of the aircraft; propellors sweep out 9 times the area, but the body weighs 27 times as much

Oops. Ever wonder why toy drones have dinky little propellors, relatively speaking, compared to real-life helicopters which have a gigantic overhead rotor?

Re:How well does it scale?

[Kotukunui]

I agree about the volume increasing by N^3, but does that necessarily mean the weight increases by that factor? Most of the volume inside the fuselage of an aircraft is air. Empty space to be filled with systems and payload. I guess it could be argued that the most efficient aircraft are designed to transport as close to their full volume as possible of payload, but not all of it will have the same density as the structural material. I suspect you are on the correct path but I'm not sure if the ratio is a simple N^2 for air moved versus N^3 for mass. There must be an efficiency curve intersection in there somewhere, I'm just not smart enough to define it.

Re:How well does it scale?

[blindseer]

While sometimes that can work against you it can also work for you. When it comes to things like efficiency in heat engines then making them larger can mean the area of losses grows by N^2 but volume of power production grows by N^3.

Sometimes bigger is better.

Re: So what's the range of the full size prototype

[Anonymous Coward]

People travelling between the continents inside aluminum cylinders traveling at 500mph at 30,000 feet? Preposterous!

People being able to send video messages to each other using small computer screens that will inside a pocket? Ludicrous!

You dumbfuck

[Anonymous Coward]

You are so profoundly ignorant that you think you're right. German ATC assigns speed in knots and indicated mach. British ATC assigns speeds in knots and indicated mach. Chinese ATC assigns airspeeds in knots and indicated mach. Indian ATC assigns airspeed in knots and indicated mach. Been assigned airspeeds in knots all over Africa, Europe and Asia. Russia is the only exception, with ATC done in KPH, but my understanding is that they accept knots because everyone else in the world flies knots.

Re:You dumbfuck

[blindseer]

A knot is defined as one minute of geographic latitude in one hour, or a close approximation of it.

My understanding is that this is an accepted means of indicating speed is because it makes for easy translation of speed and distance on common maps. Certainly tradition plays a part but this part it plays is because of how people kept time and measured distance. Since we still use minutes of latitude and hours in tracking distance and time we still use the knot to translate between them.

When traveling at greater heights and distances then other units become more convenient, like mach number and kph. Even then the conversion to knots is almost inevitable since the world is laid out in minutes of arc on most any map you'll find.

Re:You dumbfuck

[Anonymous Coward]

You are so profoundly ignorant that you think you're right.

Typical of ignorant internet commenters. And they're proud of it too. /signed someone who develops commercial avionics software.

Re:You dumbfuck

[Anonymous Coward]

Thanks for the explanation. I'm not sure all that applies anymore, since we use electronic navigation systems. It could help though in case of critical navigation system failure, though. And I'm not sure even in that case, since aircraft could have redundant systems for that.

I'll admit such knowledge is completely outside my experience (even with maps!).

Meanwhile..

[CptLoRes]

we have the open-source/DIY community doing pretty much the same, having the ability to do complete fully autonomous vertical takeoff, transition, mission and landing scenarios for over a year now. All at a fraction of the cost. http://ardupilot.org/plane/doc...

Astronavigation and knots

[blindseer]

I'm not a professional map reader by any means but I did some work on electronic navigation systems and I like to read about history, because of this I read up on how navigation is done now and how it was done before.

I suspect that measuring speed in knots came in common use once people understood astronavigation. Common trade routes were primarily along longitudinal lines, such as along the American coasts and from Europe to Africa. Knowing your speed in knots would have a lot of meaning in that case. By knowing your latitude at a given time in the past and comparing that to your current latitude then speed can be approximated. Knowing the time is also fairly trivial even before modern time pieces so long as one did not deviate far from a given longitude.

When it comes to radio navigation the units used there would lead one to use kph to indicate speed. Radio wavelengths are commonly measured in meters. Angular measurements would be in degrees and minutes still but that does not mean it translates well to the degrees and minutes used to indicate latitude and longitude on a map. Distances and directions still would though.

When it comes to critical navigation failures on land, sea, or air it is not uncommon to fall back to astronavigation. However this does not necessarily mean one would also fall back to using knots in measuring speed. Kilometers, minutes of arc, and such are still very useful and would translate well to a map laid out in kilometers.

Knots may fall out of common use in time but it's got a lot of inertia behind it. A lot of that inertia will come from trade routes still being largely oriented north-south.

Re:Astronavigation and knots

[Anonymous Coward]

Interesting. And it will probably last a number of years, since not everyone has access to formal education and for many (if not most) communities all over the world, knowledge is passed from generation to generation.

That said, I searched for the origins of its use, but there are only references to simple devices used since the 15th century.

One definition says people would have a rope with knots, throw it in the water and see how many "knots" were let out.

ref: https://www.infoplease.com/askeds/nautical-knot

Re:Astronavigation and knots

[blindseer]

That is a very likely story behind the use of the word "knot" as a measure of speed. How a "knot" became defined as a minute of latitude per hour is another matter.

I suspect the use of knots in a rope to measure speed was one thing, and the measure of speed by minutes of latitude per hour was another thing, which converged in meaning over time. I don't know the answer and it's possible no one does.

Re:Astronavigation and knots

[Anonymous Coward]

It's because you can very easily measure distance on a nautical chart using compasses (the kind with two legs) and the vertical scale, which is naturally divided by degrees and minutes of latitude, provided you use the nautical mile (i.e. one minute) as your unit of measure.

Re: So what's the range of the full size prototype

[Anonymous Coward]

If they ever figure out how to make flow batteries store lots of energy without weighing literally tonnes it might work!

Or battery swap. It's the military, fly to base of operations carrying extra battery pack (cargo comes in via larger planes). Then leave your spare battery charging while you fly in and out of the operating area with real cargo, swapping battery every time you land back at the base.

someone should tell them

[Anonymous Coward]

Someone should tell them you can buy a sub-scale quad copter from ali express. it also is electric and does VTOL.

needs full size

[Anonymous Coward]

I'll be impressed if the full-size version works as well. RC aircraft have well-proven power to weight advantages with electrics, but run into scaling issues quickly.
Getting this aircraft to work is about as impressive as the initial multi-copters. What will be impressive is if they can solve the scaling issue.

An inefficient design?

[cyn1c77]

This aircraft (which is hard to find an actual picture of) seems like a really inefficient design.

Each engine introduces substantially more weight and drag than does simply increasing the propeller diameter, so usually designers choose to minimize the number of nacelles and engines to what is required to accommodate an engine failure in flight.

This prototype seems to be taking the opposite approach. While it looks interesting, it also seems like it would have a lot of drag when it transitions into horizontal flight mode. This is probably what TFA means when they say "The biggest challenge yet to be overcome will be whether the full-scale model can meet the performance objectives DARPA initially set for the project."

Things to Come?

[tmjva]

The wings remind me of the gull winged WT715 in H.G. Well "Things to Come" but without the ducts.