[HN Gopher] Rocket Helicopter (2010)
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Rocket Helicopter (2010)
Author : jeffreyrogers
Score : 91 points
Date : 2020-09-04 15:00 UTC (7 hours ago)
(HTM) web link (www.tecaeromex.com)
(TXT) w3m dump (www.tecaeromex.com)
| protomyth wrote:
| Sounds a bit like the Fairey Rotodyne which had the same setup
| using small jets. It was very loud even for the standards of the
| day.
|
| https://www.youtube.com/watch?v=EA3AkvxwS_M
|
| https://en.wikipedia.org/wiki/Fairey_Rotodyne
| 6gvONxR4sf7o wrote:
| Doesn't the pitch of a helicopter blade change as it goes around
| the rotation? With a traditional rotor, the torque is always
| angular, but with these, the torque will be angular plus a
| cyclical vertical component, since the rocket pitch is the blade
| pitch. I'm wondering what the the structural and vibrational
| implications are of a rocket launching the blade tip up and down
| at 500 RPM.
| liability wrote:
| From what I can tell from the images and videos, this
| helicopter does seem to have a typical swashplate system for
| controlling blade pitch.
| kevin_thibedeau wrote:
| There is no cyclic. The entire mast is gimbaled.
| 6gvONxR4sf7o wrote:
| Wow, cool. I wonder if that's a big factor in why the test
| pilot said it was so vibration free.
| nsxwolf wrote:
| How does the fuel get to the rockets without the hoses getting
| torn off?
| javiramos wrote:
| Probably a rotary fluid coupling [0]. The fluid equivalent of a
| slip ring used in electrical applications.
|
| [0] https://www.dsti.com/rotary-unions/
| tus88 wrote:
| It flow inside the wings (yes copters have wings).
| mbrameld wrote:
| Nobody actually involved with helicopters calls them wings.
| They're called rotor blades.
|
| Similarly, nobody actually involved with helicopters calls
| them copters.
| jeffreyrogers wrote:
| The way these work is pretty interesting. Rather than combusting
| a fuel and an oxidizer as in a typical rocket, these use hydrogen
| peroxide that is exposed to a platinum catalyst, which causes the
| rapid decomposition of h202 into h20 and 02, which is then
| expelled through the rocket nozzle, generating thrust. This
| greatly simplifies the design of the rocket engine.
| arethuza wrote:
| H202 rockets have been around for a long time. Indeed, the UK's
| only self launched satellite was on a launcher using the stuff:
|
| https://en.wikipedia.org/wiki/High-test_peroxide
| liability wrote:
| The German V2 rockets also used hydrogen peroxide and a
| catalyst (sodium or possibly potassium permanganate) to drive
| their turbopumps (which pumped LOx and alcohol into the
| engine.) Here's a pretty good 2.5 hour long documentary about
| the V2 turbopumps specifically:
| https://youtube.com/watch?v=EgiMu8A3pi0
|
| (The H2O2/catalyst system is discussed/demonstrated around
| the 45 minute mark.)
| avmich wrote:
| Russian Soyuz rocket family still uses hydrogen peroxide
| for driving pumps on engines of 1st and 2nd stages - RD-107
| and RD-108.
|
| The only - notable - exception is Soyuz 2-1v, which has no
| boosters and the 1st stage engine is famous NK-33. That's a
| whole different story.
| mannykannot wrote:
| The claim in this article is that the motors use 70% hydrogen
| peroxide with alcohol (it does not say which one), without a
| catalyst. I have not found any explanation of the alcohol's
| purpose, or whether it is oxidzed in the process.
| skykooler wrote:
| It's confusing, because at the top they say "This rockets
| don't use a catalyst" but further down the page they say "all
| this thanks to our proprietary formula of the penta metallic
| catalyst pack invented by Juan Manuel Lozano Gallegos from
| TAM."
|
| (Side note: I saw that name and wondered where I had seen it
| before; turns out he's the guy Popular Science wrote about
| fifteen years ago for building his own peroxide-powered
| jetpack.)
| thescriptkiddie wrote:
| It could be a "mixed monopropellant". The H2O2 decomposes to
| H2O + O2, presumably at high enough temperature to react the
| O2 with the alcohol (probably ethanol or methanol). As an
| added benefit your exhaust gas is no longer oxygen-rich,
| which can cause problems.
| vanderZwan wrote:
| So does anyone know what happened after the last company that
| backed the project went bancrupt?
| pueblito wrote:
| Why doesn't this helicopter need a tail rotor? I was under the
| impression that it was to counteract the spinning main rotor
| liability wrote:
| In a normal helicopter, the helicopter is exerting a force on
| the rotors and thus feels an equal and opposite force that
| needs to be countered, either by a tail rotor or a counter-
| rotating rotor. This helicopter doesn't do that. If anything
| I'd think it might need a tail rotor to stop it from spinning
| in the same direction as the rotor, but I guess friction
| between the helicopter body and the rotor is low enough that
| this isn't a serious concern.
|
| (The linked youtube video shows a version of this helicopter
| that does have such a tail rotor, though positioned closer to
| the helicopter than it might normally be.)
| bzax wrote:
| The equal and opposite torque is provided by the blade tip
| rockets instead by the helicopter body.
| LeifCarrotson wrote:
| It is, the tail rotor is needed because on a conventional
| helicopter the main rotor is spun using a torque force from the
| helicopter body, through the engine/gearbox, and into the
| rotor. On this helicopter, the force is from the rotor through
| the rockets to the air, there's only a tiny friction force
| dragging the body along with the main rotor, and it looks like
| that's small enough to be counteracted by the aerodynamics.
| [deleted]
| vannucci wrote:
| When the engine on top of a helicopter spins the blades, they
| exert an equal torque force back on the body of the helicopter.
| In order to just spin the blades and keep the body straight,
| you have to cancel that torque by using a tail rotor which
| creates a force way back on the tail that with the length of
| the tail, cancels it out.
|
| In the case of this helicopter, the force to spin the blades
| comes from the tips of the blades, expelling gas out the tips
| will push the blade tips forward, so the body doesn't push on
| the rotor blades at all to spin them.
| jeffreyrogers wrote:
| Because the rotation is caused by a force at the rotor tips, so
| there is no torque on the aircraft. A conventional helicopter
| has an engine that is rotating a shaft connected to the rotor,
| so the engine is creating a torque on the shaft which causes
| the rotor to spin and then the shaft is creating an equal and
| opposite torque on the engine that is causing the aircraft to
| rotate the opposite way, which the tail rotor cancels.
| daniel-thompson wrote:
| The difference is in where the torque is generated. In a
| traditional helicopter, the engines (mounted to the main body)
| generate torque to spin the main rotor. Since the body spins
| the rotor, by Newton's third law, the body and the rotor spin
| in opposite directions. Therefore, you need a tail rotor to
| counteract that.
|
| With this design, the torque to spin the rotor is generated on
| the rotor itself, so there is no torque effect on the airframe.
| Note that there is still a (rotorless) tail with fins, probably
| to stabilize the aircraft in forward flight.
|
| For more on this design, see
| https://en.wikipedia.org/wiki/Tip_jet
| hinkley wrote:
| If you want to attach a spinning object to a stationary one
| you need bearings, which means friction, which means torque.
| Nowhere near the torque of a normal helicopter, but
| something. I take it the double fins in the back (at the end
| of a long lever) can more than handle that. Or at least, as
| long as the bearings don't fail.
|
| Gyroscopic precession, though... Is that enough tail or do
| you have to be gentle changing directions in this thing?
| daniel-thompson wrote:
| > Or at least, as long as the bearings don't fail.
|
| If the bearings fail, counteracting torque is the least of
| your worries - you should land immediately before the rotor
| shits itself and you turn into a flaming lawn dart. From
| the UH-60 operator's manual:
|
| > 9.22.10 Main Transmission Failure.
|
| > WARNING
|
| > If % RPM R decreases from 100% to below 96% with an
| increase in torque during steady flight with no engine
| malfunction, the main transmission planetary carrier may
| have failed. During a main transmission planetary carrier
| failure, it may be impossible to maintain % RPM R at 100%.
|
| > NOTE
|
| > Decreasing % RPM R may be accompanied by a drop in
| transmission oil pressure of 10 psi or more, and possible
| unusual helicopter vibrations.
|
| > PROCEDURE
|
| > 1. Collective - Adjust only enough to begin a descent
| with power remaining applied to the main transmission
| throughout the descent and landing.
|
| > 2. LAND AS SOON AS POSSIBLE.
| hinkley wrote:
| I like to keep people guessing by alternating between
| ironic understatement and hyperbole. Too much BBC
| perhaps.
|
| I know in low rpm devices, especially with radial forces
| (wheels) a bearing or race can start to go without
| destroying the whole assembly. To the point that
| bicyclists can bring in a wheel that's so far gone that
| the labor to fix it is twice the cost of a new wheel (I
| can fix this or we can get you a new _pair_ of wheels for
| the same price, installed). How long do you have between
| the first chip and game over on a rotor?
|
| Some how, even though "LAND AS SOON AS POSSIBLE" is in
| all caps, I doubt it entirely captures the urgency. If
| anything involved with keeping the blades attached fails,
| sounds like a case of any other plans you had are over
| and you need to be on the ground RFN while it's still a
| choice.
| jeffreyrogers wrote:
| > Gyroscopic precession, though... Is that enough tail or
| do you have to be gentle changing directions in this thing?
|
| The torque created by the tail is parallel (or nearly
| parallel) to the angular momentum of the rotor, so it
| shouldn't induce precession.
| AgloeDreams wrote:
| A typical helicopter has a motor between the body and the
| blades. Imagine using a screw gun. When you go to tighten a
| screw, equal force is imparted back on your hand because it's
| using your hand to push against.
|
| These designs have the rocket motors pushing between the blades
| and air. This means that the spinning main rotor is just
| sitting on a bearing and the rotor is not being pushed off of
| the main frame.
|
| However. You still need tail control to point it the way you
| want and to counteract inefficiencies in the main rotor
| bearing, that is why their prototypes have a tail rotor. That
| said, it's not As needed. If you lose the tail on a normal
| single blade heli, you are in for one hell of a ride. On this,
| a little forward movement and the vertical tail of the heli is
| likely enough to keep it straight.
| arethuza wrote:
| Something that spins around at high speed using 70% hydrogen
| peroxide....
|
| Don't think I'd want to be anywhere close to that device.
| Someone wrote:
| It doesn't spin that fast (linear speed) close to the
| helicopter, and any fuel leaking out of the wings during flight
| will fly outwards so you would be safe inside ;-)
|
| However, I expect they pump the fuel from the helicopter body
| into the wings, and I wonder how they guarantee the seal
| between the two. Helicopters must continuously adjust the angle
| of attack of the wings, so it isn't even a matter of a single
| fixed axis, and the chemical properties of hydrogen peroxide
| won't make things easier.
| regularfry wrote:
| Once it's started up, it's a centrifugal pump all on its own.
| You don't need a positive pressure pump on the body, the fuel
| would be sucked out and along the blades like a siphon.
|
| That doesn't make the seal problem much easier, but it at
| least does mean that if a seal were to fail, it would fail
| safe without spewing h2o2 everywhere.
| jeffreyrogers wrote:
| > I expect they pump the fuel from the helicopter body into
| the wings, and I wonder how they guarantee the seal between
| the two.
|
| I was wondering about that too. I haven't found a good
| explanation anywhere.
| milankragujevic wrote:
| Wow, I used to make rocket-powered helicopters in Kerbal Space
| Program a few years ago by putting a "Sepratron" on the tip of
| the "blade" made from structural wing parts. How appropriate :)
|
| See this video for more details:
| https://www.youtube.com/watch?v=1Sj_jgrokww
| baldeagle wrote:
| I'm a little skeptical about the claim of 'performance is the
| same at any altitude'... while yes, the engine performance is
| similar at altitude, the helo performance is not (what with the
| fewer air bits for the blades to move around)
| liability wrote:
| Yes, it's my impression that helicopters have problems with
| thin air reducing lift long before they lose engine power.
| That's why it's easier for them to fly forward than hover at
| high altitudes; the forward velocity of a moving helicopter
| provides more airflow over the rotors and thus more lift. I
| don't think it's a matter of jamming more air into the
| turboshaft engines, which presumably could be done using larger
| intakes.
| MaxBarraclough wrote:
| > it's my impression that helicopters have problems with thin
| air reducing lift long before they lose engine power.
|
| I believe this is generally true, but it's certainly possible
| to get into trouble.
|
| The world record for the longest autorotation was set after
| an engine flameout, after an attempt at the world record for
| highest altitude reached in a helicopter. [0]
|
| > the forward velocity of a moving helicopter provides more
| airflow over the rotors and thus more lift
|
| It's more that a helicopter in a hover (assuming little wind)
| must produce additional lift (i.e. more power) as it's stuck
| in a downdraught of its own creation. Introduce some forward
| movement, and the helicopter is flying through undisturbed
| air (or more precisely, the air entering the main rotor disc
| is undisturbed), which takes far less power.
|
| This is called 'translational lift'. It kicks in at around 30
| knots, and occurs at any altitude. It might be more
| consequential at very high altitude though, or under very
| heavy load, where the helicopter might have enough power for
| forward flight, but inadequate power for a hover. [1]
|
| The FAA have an interesting _Power vs airspeed_ chart, p19 of
| [2]. If I understand correctly, it means that if your goal is
| to keep a helicopter in the air as long as possible, you want
| to stay at around 62 knots of indicated airspeed. Fairly
| slow, but nowhere near a hover. ( _edit_ 'Ground effect'
| might also have some bearing on that question, but that's
| another matter.)
|
| [0] https://en.wikipedia.org/wiki/Jean_Boulet
|
| [1] https://en.wikipedia.org/wiki/Translational_lift
|
| [2] (PDF warning) https://www.faa.gov/regulations_policies/ha
| ndbooks_manuals/a...
| liability wrote:
| Very interesting, thanks for this. Do you suppose a hybrid
| system might be useful in special applications, like
| providing a power boost to rescue helicopters trying to
| hover above mountains?
| MaxBarraclough wrote:
| Rather beyond my knowledge but I'll take a stab at it:
|
| I don't think tip jets (the name for this design, oddly
| absent from the article) [0] are generally thought to be
| of practical value in modern helicopters. They have the
| neat advantage that they don't require a tail-rotor (the
| main rotor isn't driven by a drive shaft from the main
| body of the helicopter so there's no torque trouble) but
| I don't think they're all that practical. This article
| dates from 2010 after all.
|
| We already have a reliable means of increasing a
| helicopter's power: bigger engines. Alternatively, more
| engines.
|
| Heavy-lifting helicopters tend to be powered by twin
| turbine engines. [1][2] Even if they use unusual designs
| [2] the power-plant is the same as for any other serious
| helicopter. The enormous _Super Stallion_ military
| helicopter went even further: _3_ turbine engines! [3]
|
| I imagine a hybrid design would greatly increase
| complexity. Helicopters use a 'sprag clutch' to permit
| the rotor RPM to exceed the engine RPM, but not the other
| way around. This allows the rotor to keep spinning in
| case of an engine failure. (This is the reason
| helicopters don't drop like bricks when their engines
| fail.) Perhaps there would be a way to modify the design
| so that the conventional engine could still contribute
| power even as the rockets are firing, but I imagine it
| would be very high in complexity.
|
| Also, tail rotors can suffer if they aren't working in
| clean air, and of course this can threaten the
| helicopter's safety. [4] It's not something I know
| anything about but I imagine rockets on the main rotor
| could be troublesome in that regard.
|
| For yet another wacky (but likely impractical)
| alternative design with no need for a tail rotor, see [5]
|
| Lastly, google tells me rockets have been used to assist
| fixed-wing aircraft in takeoff. [6]
|
| [0] https://en.wikipedia.org/wiki/Tip_jet
|
| [1] https://en.wikipedia.org/wiki/Sikorsky_S-64_Skycrane
|
| [2] https://en.wikipedia.org/wiki/Kaman_K-MAX
|
| [3] https://en.wikipedia.org/wiki/Sikorsky_CH-53E_Super_S
| tallion...
|
| [4] https://en.wikipedia.org/wiki/Loss_of_tail-
| rotor_effectivene...
|
| [5] https://youtu.be/0Z2Rr39hiUs
|
| [6] https://en.wikipedia.org/wiki/JATO
| MaxBarraclough wrote:
| Too late to edit, I now see I failed at high-school
| physics.
|
| Trivially, a helicopter in a hover is producing the same
| lift force as a helicopter flying forward (with zero
| vertical speed).
|
| Being stuck in a downdraught means the hovering helicopter
| must use more power to generate the same amount of lift
| force.
| skykooler wrote:
| The thing is, there's less air for the blades to move, but
| there's also less drag on the blades for the same reason, so
| they spin faster with the same power input. This ends up
| cancelling out the loss of lift, meaning that the performance
| stays roughly constant with altitude until it is high enough
| that the blade tips start to approach the speed of sound.
| nextaccountic wrote:
| What happens at the speed of sound?
| AgloeDreams wrote:
| Honestly makes a lot of sense.
|
| Might be possible do do it as a ram jet too, that would get you a
| lot of efficiency upsides. Typical jet engines probably wouldn't
| work well however due to force but you get a fuel feed upside
| from the centrifugal force.
| mnw21cam wrote:
| Ramjets work at supersonic airflow speeds. You really don't
| want your helicopter blade tips going supersonic.
| [deleted]
| AgloeDreams wrote:
| Wouldn't it be possible to use a subsonic inlet but design
| the intake to allow for air to become super sonic in the
| flow?
| checker wrote:
| Fair warning, this is probably a ridiculous idea because I'm
| nothing close to a mechanical/aerospace engineer.
|
| Would it be possible to mount the ramjets to a ring around
| the blades along with some sort of transmission in the ring?
| I'm thinking setup this would allow the ramjets to function
| supersonically at the edge of the structure to ensure the
| best airflow and limit the speed of the blades. However such
| a transmission might be overly complex or heavy and it's
| possible that the ring around the blades would cause some
| weird aerodynamic effects.
|
| Thanks for obliging my curiosity!
| jeffreyrogers wrote:
| There was a helicopter that used a ram jet IIRC. I guess the
| only problem there is you need a separate starter motor to get
| the rotor spinning fast enough for the ramjet to take over, but
| most helicopters have electric starters anyways.
|
| Edit: Here's one https://en.wikipedia.org/wiki/NHI_H-3_Kolibrie
| gostsamo wrote:
| Isn't this fuel rather toxic in case of accident?
| arethuza wrote:
| One of concerns would be how much of it gets converted by the
| catalyst - if it's not 100% for any reason you've basically got
| a rotating sprinkler throwing HTP about.
|
| Edit: To be fair it's not HTP, fortunately for those under the
| flight path...
| rbanffy wrote:
| Everyone around it will turn blonde.
| Justsignedup wrote:
| Can this be converted to use standard combustible fuel?
|
| I wonder if this can be converted to a jet engine that pumps
| pressurized air out of the ends of the blade rather than this
| stuff.
| liability wrote:
| Maybe that could be made to work, but if you're already
| committed to using a gas turbine of any sort, why not make
| it a turboshaft engine and build a conventional helicopter?
| Either way you have to pay for the expensive maintenance of
| a turbine engine. If a rocket-helicopter could have any
| real advantages (they're certainly cool, but I'm rather
| skeptical), it would surely be the simplicity of the
| mechanism making it cheaper to operate.
| Justsignedup wrote:
| I think one of the big points is that elimination of the
| tail rotor could prevent 100% of the tail-rotor failure
| crashes. So something like 87% of crashes are related to
| tail rotor failures.
|
| So I guess that would be the advantage. Also lighter
| because you're now missing an entire complex mechanism
| for the tail rotor and potentially that giant tail.
| liability wrote:
| Coaxial rotor helicopters can be built without tail
| rotors, but my general impression is these are considered
| less reliable than conventional helicopters due to the
| added mechanical complexity of a coaxial system. But if
| tail rotor failure are that common, maybe coaxial rotor
| helicopters are worth the added complexity after all?
| They certainly seem more practical than rocket-
| helicopters.
| Justsignedup wrote:
| Interesting!!!
|
| However those rotors are primarily used for accuracy when
| flying. I believe they give more accurate control at the
| cost of speed.
| liability wrote:
| I'm not sure about that; the Russian Ka-50 coaxial attack
| helicopter seems reasonably quick, certainly not the
| fastest helicopter ever but comparable to an Apache at
| least (315km/h vs 293 km/h respectively, though the
| Apache has a higher never-exceed speed: 350km/h vs
| 365km/h)
|
| If you include compound helicopters (using horizontal
| pusher props or turbojets), coaxial helicopters can
| certainly be very quick; the S-97 can cruise at 410 km/h,
| but in that case you have the liabilities of a 'tail
| rotor' to contend with again. The S-69 could do a
| blistering 487km/h with it's turbojets, 289km/h without.
|
| One to consider is the Eurocopter X3, a single rotor
| compound helicopter without a tail rotor. It could do
| 472km/h and used two tractor propellers with variable
| pitch to counteract the rotor torque.
| rbanffy wrote:
| It's a 3 according to it's NFPA 704 diamond, so yes. Not the
| worst rocket fuel, but not exactly healthy.
|
| If you touch it, it'll bleach you.
| liability wrote:
| In addition to actually bleaching things, H2O2 has
| vasoconstrictive properties which can sometimes cause the
| _appearance_ of skin being bleached. Whenever I apply
| pharmacy-grade hydrogen peroxide to my skin it causes a
| temporary 'bleached' effect that fades after a few minutes.
| This is apparently a matter of small blood vessels near the
| surface of my skin being constricted. Wikipedia doesn't
| mention this effect but it's not too hard to find sources on
| (https://pubmed.ncbi.nlm.nih.gov/860154/). I'm not sure if
| large exposures could cause heart attacks though this effect,
| I suppose chemical burns would be the more immediate concern,
| but it's certainly not something I'd want to find out first
| hand.
| rbanffy wrote:
| Well... The people who make the rocket apparently make HTP
| jetpacks, so I assume they haven't killed too many people
| with their gear. Yet.
| liability wrote:
| They take a lot of precautions I'm sure. It's dangerous
| stuff but obviously not impossible to handle if you know
| what you're doing.
| rbanffy wrote:
| Unfortunately for my morning commute (which is not
| happening again anytime soon anyway), their HTP jetpack
| has about 20 seconds of flight time and, fortunately for
| society at large, you can't get HTP at a gas station.
| bfuclusion wrote:
| For any HN'ers in the bay area, if you're into this stuff you
| should pay a visit to the Hiller Aviation museum. It's right by
| EA on the San Carlos Airport. Hiller was a pioneer in helicopter
| design, and they have a ramjet tipped 'copter on display. Here's
| their website: https://www.hiller.org/museum/aircraft-on-display/
| hankchinaski wrote:
| doesn't this tiny rocket have very low range and bad efficiency
| compared to a traditional helicopter engine? the energy density
| of h2o2 is close to the one of a ion lithium battery (2.7MJ/Kg)
| vs the traditional gasoline+o2 (13.3 MJ/Kg) [1]. It seems like
| more a cool trick than something which can replace helicopter
| engines?
|
| [1]
| https://en.wikipedia.org/wiki/Energy_density_Extended_Refere...
| jeffreyrogers wrote:
| Yes, you're right. The advantages are that it is much simpler
| mechanically and can be made more cheaply. But I think it is
| mostly just a cool novelty. I don't see how these can compete
| with conventional helicopters.
| avmich wrote:
| Not just regular Li-Ion, but a specific kind, a few times more
| dense that the regular variety. Is it as easy to get as
| hydrogen peroxide?
| avmich wrote:
| I think Juan Lozano was making peroxide engines for early
| iterations of John Carmack's Armadillo Aerospace (whose website,
| sadly, is now only available via web archive...)
|
| EDIT: yes, AA is listed as a customer.
| maxbaines wrote:
| Seems obvious now I see it!
| pstuart wrote:
| It looks cool but the last update was 10 years ago for PoC?
| trhway wrote:
| my favorite application of that tech - Roton, a helicopter to
| space - https://en.wikipedia.org/wiki/Rotary_Rocket . USSR people
| know it as "Pepelats" http://copy-cats.work/aircraft02/rotary-
| rocket-roton :)
| nabla9 wrote:
| Tip jets can use compressed air. That would be more efficient.
|
| https://en.wikipedia.org/wiki/Tip_jet
|
| As with all cool concepts "Zee Germans" had the idea
| https://en.wikipedia.org/wiki/Focke-Wulf_Triebfl%C3%BCgel
| MaxBarraclough wrote:
| Not _all_ the cool concepts.
|
| The Dutch came up with the 'ornicopter':
| https://youtu.be/0Z2Rr39hiUs
| evilsetg wrote:
| A friend just showed me this beast, also using tip jets:
| https://www.youtube.com/watch?v=dWNq0LSnHLo
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(page generated 2020-09-04 23:00 UTC)