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1669: Planespotting

Posted: Mon Apr 18, 2016 2:37 pm UTC
by Ignitus
Image

URL: http://xkcd.com/1669/

Title Text : No, a hydroplane doesn't land on water--that's an aquaplane. A hydroplane is a plane that gets electric power from an onboard water reservoir with a tiny dam and turbines.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 2:40 pm UTC
by cellocgw
No, Randall's wrong: a hydroplane is made of water.
Even better, it generates fuel by separating itself into H2 and O2, then burning the reactants. :mrgreen:

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 2:41 pm UTC
by AlfaLyr
"Boeing Q404, plane not found on this server"

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 2:49 pm UTC
by Ignitus
I like to think he at least got the Boeing 747 correct and the rest of the message was data corruption and invalid error handling.

cellocgw wrote:No, Randall's wrong: a hydroplane is made of water.


:lol:

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 2:54 pm UTC
by speising
How do you even pronounce "Mk. IVII"?

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 2:56 pm UTC
by Keyman
speising wrote:How do you even pronounce "Mk. IVII"?

42

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 2:56 pm UTC
by Echo244
OK, so Randall's responding to the "Captain Speaking" aeroplane-identification criticism...

It being Randall, I'm kind of expecting the aeroplane pictured to be a composite of identifying features of various aircraft types listed, before salting the description with nonsensical additions like "dual-wield". However, my technical background in this field isn't strong enough to pick out any details and match them with -380 or anything...

Anyway. Not a 747, I don't think. Too few engines.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 3:05 pm UTC
by rmsgrey
Looks to me like a classified military drone (and much closer than you think)

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 3:07 pm UTC
by Caesar
Ehm, shouldn't it be "...one of those people who know..."?

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 3:18 pm UTC
by Neil_Boekend
cellocgw wrote:No, Randall's wrong: a hydroplane is made of water.
Even better, it generates fuel by separating itself into H2 and O2, then burning the reactants. :mrgreen:

I know someone who genuinely seems to believe you can power a car with that kind of setup and no external power. Apparently there are quite a few scammers that sell conversion kits. I have advised him to read up on conservation of energy.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 3:27 pm UTC
by BlitzGirl
Caesar wrote:Ehm, shouldn't it be "...one of those people who know..."?

I think that the comic's construction is correct. The verb "knows" is being applied to the singular "one." I'm one who knows...

But then again, I've always assumed I'm one of those people who knows a lot about words, but I've never actually checked.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 3:33 pm UTC
by Caesar
BlitzGirl wrote:
Caesar wrote:Ehm, shouldn't it be "...one of those people who know..."?

I think that the comic's construction is correct. The verb "knows" is being applied to the singular "one." I'm one who knows...

But then again, I've always assumed I'm one of those people who knows a lot about words, but I've never actually checked.


It's grammatically correct but if you apply the "knows" to the singular "who" instead of the "people", then "those people" is left unspecified. But that's not what the speaker meant. He meant a group of people who know a lot about planes.
That's my understanding of it, anyway.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 3:35 pm UTC
by orthogon
Caesar wrote:Ehm, shouldn't it be "...one of those people who know..."?

Oh no. What have you done?

I see your point, but I suspect the way Randall wrote it is fairly common usage. The thing is it's not actually ungrammatical, because you can parse it as "I'm (one of those people) who knows...", with the singular NP in parentheses agreeing with the verb. But I agree that "I'm one of (those people who know ...)" is closer in literal meaning to what's meant: "Me ϵ (People who know)".

ETA: Actually you could say "I'm one of those people; I know a lot about planes".

Pseudo-edit: Ah, do you think it should be know to agree with the first-person I? In that case, no, you say "I'm a person who knows a lot about planes": the grammatical subject is a person.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 3:38 pm UTC
by Soupspoon
speising wrote:How do you even pronounce "Mk. IVII"?

It's 1001 in 1337-LATIN...

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 3:38 pm UTC
by ManaUser
speising wrote:How do you even pronounce "Mk. IVII"?

It's just Mark 6, widely considered to be two steps forward and one step back from the previous model.

Either that or Mark Ivy, companies are always respelling words for trademark purposes these days.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 3:39 pm UTC
by cellocgw
orthogon wrote:
Caesar wrote:Ehm, shouldn't it be "...one of those people who know..."?

Oh no. What have you done?

I see your point, but I suspect the way Randall wrote it is fairly common usage. The thing is it's not actually ungrammatical, because you can parse it as "I'm (one of those people) who knows...", with the singular NP in parentheses agreeing with the verb. But I agree that "I'm one of (those people who know ...)" is closer in literal meaning to what's meant: "Me ϵ (People who know)"


On the bright side, there's no option for an Oxford Comma anywhere in the original sentence :lol:

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 3:58 pm UTC
by Neil_Boekend
Well if water powered spaceships are a potential thing, why not planes?

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 4:00 pm UTC
by moody7277
First thing the alt-text brought to mind was this.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 4:37 pm UTC
by pixeldigger
It appears to actually be a Bombardier Dash 8 Q400

Image

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 4:40 pm UTC
by Rondar
Hello. I registered just because there's a whole page in this thread and no one has mentioned whether that is Black Hat or White Hat in silhouette. Please stop making me work for things.

If it's Black Hat, is he asking about the plane because of some nefarious scheme? If it's White Hat, was the question more philosophical?

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 4:46 pm UTC
by Sableagle
Thank you. I knew it looked familiar.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 5:44 pm UTC
by Envelope Generator
dual wield
Image

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 7:51 pm UTC
by Moose Anus
Neil_Boekend wrote:
cellocgw wrote:No, Randall's wrong: a hydroplane is made of water.
Even better, it generates fuel by separating itself into H2 and O2, then burning the reactants. :mrgreen:

I know someone who genuinely seems to believe you can power a car with that kind of setup and no external power. Apparently there are quite a few scammers that sell conversion kits. I have advised him to read up on conservation of energy.
You actually can do it using chemical energy to make it all work. For example, you can combust hydrocarbons to drive a dynamo which can electrify water and generate H2 and O2 which can then be combined to produce a clean energy solution.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 8:43 pm UTC
by Pfhorrest
Moose Anus wrote:
Neil_Boekend wrote:
cellocgw wrote:No, Randall's wrong: a hydroplane is made of water.
Even better, it generates fuel by separating itself into H2 and O2, then burning the reactants. :mrgreen:

I know someone who genuinely seems to believe you can power a car with that kind of setup and no external power. Apparently there are quite a few scammers that sell conversion kits. I have advised him to read up on conservation of energy.
You actually can do it using chemical energy to make it all work. For example, you can combust hydrocarbons to drive a dynamo which can electrify water and generate H2 and O2 which can then be combined to produce a clean energy solution.

Except for the exhaust from the hydrocarbon combustion

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 8:53 pm UTC
by Neil_Boekend
I am reasonably sure they tried to sell a device that splits water, burns the hydrogen with the water in a combustion engine, generate movement and electricity from that and use the electricity to split the water. You know, in an energy leaking closed circle.
But I can't be completely sure since details are scarce.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 9:07 pm UTC
by Krenn
Ignitus wrote:Title Text : No, a hydroplane doesn't land on water--that's an aquaplane. A hydroplane is a plane that gets electric power from an onboard water reservoir with a tiny dam and turbines.


I'm trying to figure this out... assuming the water reservoir experiences acceleration equivalent to what the exterior plane is experiencing.... and assuming that acceleration, and corresponding pressure/movement is what drives the tiny turbines....

and assuming that water turbines are precisely as efficient at reclaiming energy as the external jet turbines are at expending it...

Is there any sane reason for those water turbines to be installed in the first place?

I would assume that what you've just created is a really complicated, overly massive system for transferring power from the external jet turbines to the internal water turbines, for purposes of powering cabin electronics or whatnot. And I would also assume that just drawing that same power off from the jet turbines directly would be far more effective, since you wouldn't have to carry the mass penalty of all that water, and continuous power draw would be easy to plan for.

but off the top of my head, I can't mathematically PROVE that.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 9:28 pm UTC
by bachaddict
I'm pretty sure there are legitimate hydrogen kits made to use some of the excess electricity from the alternator.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 9:46 pm UTC
by Copper Bezel
Krenn wrote:I'm trying to figure this out... assuming the water reservoir experiences acceleration equivalent to what the exterior plane is experiencing.... and assuming that acceleration, and corresponding pressure/movement is what drives the tiny turbines....

and assuming that water turbines are precisely as efficient at reclaiming energy as the external jet turbines are at expending it...

Is there any sane reason for those water turbines to be installed in the first place?

I would assume that what you've just created is a really complicated, overly massive system for transferring power from the external jet turbines to the internal water turbines, for purposes of powering cabin electronics or whatnot. And I would also assume that just drawing that same power off from the jet turbines directly would be far more effective, since you wouldn't have to carry the mass penalty of all that water, and continuous power draw would be easy to plan for.

but off the top of my head, I can't mathematically PROVE that.

The potential difference between the top of the reservoir and the bottom isn't changing significantly as you move the whole system up and down. The output of the dam will be higher and lower depending on whether or not you're accelerating vertically, so a fraction of any power you siphon off while accelerating into a climb will be coming from the engines, and there's generally more climbing at the start (when the reservoir is high) and more descending at the end of the flight (when the reservoir is low), but unless you're planning to shut the system off before the end of the flight, which rather invalidates the idea of continuous power, you're going to be paying back what you gained by extracting less energy per mass of water in the descent phase. Since gravity is slightly less at your cruising altitude, you will also extract slightly less from the system than you put in on the ground even in a perfect-efficiency case. But the reservoir is definitely still a battery charged on the ground rather than a transformer powered by the engines.

Obviously, the potential difference in the system is going to be measured in feet and the potential difference involved in raising the system and carrying it along with you in flight is measured in thousands of feet, so the output will be minuscule in comparison to the energy cost of flying the system, which is simply to say that it's a battery with much, much lower energy density than is practical for flying. A practical battery doesn't actually have to be able to fly itself, though - real airplanes use jet fuel to fly, but have people inside them who use electronic devices running from Lipo cells, which have a significantly lower energy density than the jet fuel does.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 9:54 pm UTC
by Krenn
Copper Bezel wrote:
Krenn wrote:I'm trying to figure this out... assuming the water reservoir experiences acceleration equivalent to what the exterior plane is experiencing.... and assuming that acceleration, and corresponding pressure/movement is what drives the tiny turbines....

and assuming that water turbines are precisely as efficient at reclaiming energy as the external jet turbines are at expending it...

Is there any sane reason for those water turbines to be installed in the first place?

I would assume that what you've just created is a really complicated, overly massive system for transferring power from the external jet turbines to the internal water turbines, for purposes of powering cabin electronics or whatnot. And I would also assume that just drawing that same power off from the jet turbines directly would be far more effective, since you wouldn't have to carry the mass penalty of all that water, and continuous power draw would be easy to plan for.

but off the top of my head, I can't mathematically PROVE that.

The potential difference between the top of the reservoir and the bottom isn't changing significantly as you move the whole system up and down. The output of the dam will be higher and lower depending on whether or not you're accelerating vertically, so a fraction of any power you siphon off while accelerating into a climb will be coming from the engines, and there's generally more climbing at the start (when the reservoir is high) and more descending at the end of the flight (when the reservoir is low), but unless you're planning to shut the system off before the end of the flight, which rather invalidates the idea of continuous power, you're going to be paying back what you gained by extracting less energy per mass of water in the descent phase. Since gravity is slightly less at your cruising altitude, you will also extract slightly less from the system than you put in on the ground even in a perfect-efficiency case. But the reservoir is definitely still a battery charged on the ground rather than a transformer powered by the engines.

Obviously, the potential difference in the system is going to be measured in feet and the potential difference involved in raising the system and carrying it along with you in flight is measured in thousands of feet, so the output will be minuscule in comparison to the energy cost of flying the system, which is simply to say that it's a battery with much, much lower energy density than is practical for flying. A practical battery doesn't actually have to be able to fly itself, though - real airplanes use jet fuel to fly, but have people inside them who use electronic devices running from Lipo cells, which have a significantly lower energy density than the jet fuel does.


I'm assuming that there are two water resorvoirs, one in the front of the plane, and one in the back. during takeoff and initial climb, the front tankage feels an acceleration towards the back of the plane, and turbines at the back of the plane convert that into energy before storing the water in rear tankage.

during descent and landing, this process theoretically runs in reverse, and during level flight, no significant energy transfer occurs. in order to power cabin electronics throughout the flight, you would need to somehow charge batteries during the ascent phase, and have that charge last until the descent phase.

I'm PRETTY sure that having all that fluid slosh back-and-forth is robbing the aircraft of a small but measurable amount of manuevering energy, and that the parastic cost of lifting all that mass to 30,000 feet can't possibly be worth it.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 10:16 pm UTC
by Copper Bezel
I hadn't thought of a system like that, but not unrelatedly, I honestly don't think that's a very valid reading of the alt text. Hydroelectric dams and reservoirs are a thing that exist. Alt text suggests putting one on an airplane, because it's funny.

The system you're suggesting is indeed a very impractical transformer, and if it needs batteries to provide continuous power, then it could be pretty damn funny in its own right. But yeah, all the power comes from the engines. The water wants to remain stationary as you accelerate, but any resistance that your turbine applies is the plane's acceleration applied to the water, and that resistance is what extracts energy. So, the no-resistance, no friction, and no output energy case would be that the water sloshes along unobstructed and doesn't fight the plane's acceleration until it hits the back of the system, at which point it simply, all at once, becomes more mass that the plane has to accelerate. A turbine resisting the flow would be applying some of the plane's acceleration to the water and extracting just that much energy from the flow. It would be even more efficient if you let the water fall out the back of the plane and more efficient still if you the whole system on the ground and forgot about it.

Another option would be to mount tiny turbines in the wing flaps for regenerative braking.

Re: 1669: Planespotting

Posted: Mon Apr 18, 2016 10:25 pm UTC
by Soupspoon
bachaddict wrote:I'm pretty sure there are legitimate hydrogen kits made to use some of the excess electricity from the alternator.

Excess electricity?

If you put more (electrical) load on it, it demands to be driven with more kinetic energy in the first place... To simplify the process somewhat to excess.

Re: 1669: Planespotting

Posted: Tue Apr 19, 2016 2:10 am UTC
by GrapeDrank
This topic of the "hydroplane" was bothering me too. I actually registered just to add something.

I really only have a layman's understanding of physics and engineering in general, but in the event that the engines fail, wouldn't an airplane with the hydroelectric system be able to generate power by gliding upward? Or downward for that matter? Or even just turning? A gliding plane with engine failure could sacrifice altitude for power to keep in radio contact, etc etc.

Re: 1669: Planespotting

Posted: Tue Apr 19, 2016 3:18 am UTC
by RogueCynic
A plane generates a lot of wind as it travels. Why not use windmills to power the plane?

http://www.bing.com/search?q=boeing+747+retirement&src=IE-SearchBox&FORM=IE8SRC A lot of airlines have retired the 747 or will soon, so it probably isn't a 747.

Re: 1669: Planespotting

Posted: Tue Apr 19, 2016 3:36 am UTC
by serutan
Echo244 wrote: However, my technical background in this field isn't strong enough to pick out any details and match them with -380 or anything...

Anyway. Not a 747, I don't think. Too few engines.


The -380 *might* be a reference to that Airbus boondoggle, the A-380. but the silhouette is much too skinny for that.

Re: 1669: Planespotting

Posted: Tue Apr 19, 2016 7:19 am UTC
by Adacore
I think the comic pretty clearly says 797, not 747. From the context it seems likely that this is intentional.

Re: 1669: Planespotting

Posted: Tue Apr 19, 2016 9:02 am UTC
by The Moomin
Randall is thinking of old-fashioned limited range hydroplanes. The modern hydroplane is an excellent design.

The large bulge shown in the centre is the cloud condenser funnel. As the hydroplane goes forwards it funnels the cloud water droplets into the condenser where the water is then directed through the turbine to generate the power to move the plane forward to scoop more clouds.

The problem is pushing the plane fast enough through low lying clouds to generate the power to take off.

Re: 1669: Planespotting

Posted: Tue Apr 19, 2016 9:56 am UTC
by Thibaw
If that is BHG then he probably knows the answer to his question. Which adds some more levels to this.

Re: 1669: Planespotting

Posted: Tue Apr 19, 2016 1:19 pm UTC
by project2051
I've seen this guy on the network news, I think they call him an "aviation expert" or something like that.

Re: 1669: Planespotting

Posted: Tue Apr 19, 2016 5:50 pm UTC
by ps.02
I love these forum posts trying to explain in detail why the idea to use hydro power to lift a tank of water thousands of times its own dam height is actually not scientifically feasible. In case anyone here was in danger of taking it seriously.

Also, all the traffic explaining why something with a silhouette unlike a Boeing 747 in every way probably isn't a Boeing 747. (I mean, while you're at it, why not also explain why it probably isn't a Cessna Caravan? The degree of resemblance is about the same.)

Re: 1669: Planespotting

Posted: Tue Apr 19, 2016 7:55 pm UTC
by bachaddict
Soupspoon wrote:
bachaddict wrote:I'm pretty sure there are legitimate hydrogen kits made to use some of the excess electricity from the alternator.

Excess electricity?

If you put more (electrical) load on it, it demands to be driven with more kinetic energy in the first place... To simplify the process somewhat to excess.


Yes, but load on the alternator is not directly proportional to extra fuel burned. Whether the system recovers enough energy to cover its own losses is another matter.