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BOEING / GoFly contest: Oh, BOEING


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#101 Kelpiecross

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Posted 23 January 2020 - 04:35

  I don't think this discussion is really going any where.   I have said all along that is just a personal  judgement of  mine that No. 88  is very good  -  and the DVVA  not so good. Maybe you are right - but  - I would steal the No.88  (and just might)  but you couldn't force me to take the DVVA for free - or even at the point of a gun.

 

  I will reiterate that I think "desmo"  is pointless and inferior to "spring".  

 

 Sorry to be a bit personal - but you turn out a few very (very) nice ideas and designs,  some "ordinary" ones and a few real "stinkers".  But you seem to defend them all to the death -   just work with the best.  

 

  (What category do you think I put the "Flyer" in?)    



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#102 manolis

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Posted 23 January 2020 - 15:08

Hello Kelpiecross.

 

Thanks.

With your questions you gave me the opportunity to present again (and to further explain) the various pattakon-VVA’s.

 

A technically oriented person can clarify a lot about the Variable Valve Actuation systems reading the previous page, and can decide by himself which is his favorite.

 

Since you like the Lost Motion VVA of post 88 (it is the “lost motion” version of the roller-version VVA used in the black Honda Civic), be my guest and apply it in a cylinder head and present the project here.

 

 

 

For the OPRE Tilting engine and the Flyer:

 

 

Here is another application of the OPRE Tilting engine:

 

OPRE_Tilting_Single_2.gif

 

The (single) OPRE Tilting engine has on its casing two “arms” whereon a holed pipe (yellow) is secured.

 

The one crankshaft drives, by means of a reduction gearing (comprising a pair of sprockets and a “short” toothed belt (not shown)), a propeller which is rotatably mounted on the holed pipe at the one side of the engine,

the other counter-rotating crankshaft drives, in a similar way, another propeller which is also rotatably mounted on the (yellow) holed pipe, but at the other side of the engine.

The two propellers are contra-rotating.

 

OPRE_Tilting_Single_1.gif

 

Through the holed pipe they pass the fuel and the control (like: the gas cable, a cable for the release of a parachute, etc).

 

Here is the engine with the arms whereon the holed pipe is to be secured; at right is the synchronizing gearing and the transmission to the one propeller.

 

OPRE_Tilting_Single.jpg

 

The diameter of the propellers is as large as desirable.

The basis of the engine (say, the flange or the pipe whereon the engine is secured) is rid of gyroscopic rigidity, of vibrations and of reaction-torque.

 

 

The flange at the end of the (yellow) pipe can be secured on the frame at the back of a parachuter replacing the conventional propulsion unit.

 

 

If the flange at the end of the holed pipe is secured on the nose of an ultra-light or of a small airplane, it is a complete propulsion unit having significant advantages.

 

 

If the holed pipe is substantialy extended, then a simple Portable Flyer (say, a "Witch’s Broom" Portable Flyer) is made:

 

Witchs_Broom.png

 

For  safety,

a second OPRE Tilting engine with its own pair of contra-rotating propellers can be secured higher on the holed pipe.

 

Thanks

Manolis Pattakos



#103 gruntguru

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Posted 23 January 2020 - 22:11

I prefer the DVVA. It is no more complex than the other two VVA systems and offers more flexibility in terms of lift and duration combinations. As a bonus, desmodromic operation offers significant performance advantages over a system using springs and even one using pneumatic springs.



#104 manolis

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Posted 24 January 2020 - 04:36

Hello Gruntguru.

 

You write:

“I prefer the DVVA. It is no more complex than the other two VVA systems and offers more flexibility in terms of lift and duration combinations. As a bonus, desmodromic operation offers significant performance advantages over a system using springs and even one using pneumatic springs.”

 

 

Quote from the US patent 8,201,531 titled: “Desmodromic variable valve actuation”, filed June 2008, granted June 2012(!) :

 

DESCRIPTION

The closest prior art is the U.S. Pat. No. 6,892,684 (***: it is the rod-version  pattakon VVA, that in the white Renault). Instead of actuating the central swivel joint by a cam lobe, in the present invention the swivel joint is actuated positively in both directions by a link having a drive pin mounted at one end, the drive pin being engaged in a track to reciprocate therein.

The resulting valve mechanism is rid of restoring springs of any kind, it operates reliably at racing revs because it is rid of heavy fast moving parts like the track, and it is fully variable: it can change continuously and independently the valve duration and the valve lift from a maximum value to even zero, i.e. it can better approach the ideal valve lift profile for the instant operational conditions of the engine in terms of revs, load, air temperature, coolant temperature, fuel quality, driving mode, altitude etc, i.e. it can optimize the operation and the thermal efficiency along a wider rev and load range.

 

Thanks

Manolis Pattakos


Edited by manolis, 24 January 2020 - 04:37.


#105 Kelpiecross

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Posted 24 January 2020 - 04:39

I prefer the DVVA. It is no more complex than the other two VVA systems and offers more flexibility in terms of lift and duration combinations. As a bonus, desmodromic operation offers significant performance advantages over a system using springs and even one using pneumatic springs.

 

  I am sure Manny would be happy to accept your investment monies.  



#106 Kelpiecross

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Posted 24 January 2020 - 04:53

  The "Witches'  Broom"  variation  on the basic "Flyer"  idea  is one of the cleverest things I have ever seen  - where can I buy one?    



#107 gruntguru

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Posted 24 January 2020 - 07:50

  I am sure Manny would be happy to accept your investment monies.  

 . . and yours.


Edited by gruntguru, 24 January 2020 - 21:07.


#108 manolis

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Posted 26 January 2020 - 06:13

Hello all.
 
This photo shows a windsurfer:
 
Wind_Surf.jpg
 
From Wikipedia:
 
“In 1948, 20-year-old Newman Darby was the first to conceive the idea of using a handheld sail and rig mounted on a universal joint so that he could control his small catamaran—the first rudderless sailboard ever built that allowed a person to steer by shifting his or her weight in order to tilt the sail fore and aft.”
 
Doesn’t it remind the way the pilot of the Broom Flyer controls his flight?
 
Thanks
Manolis Pattakos


#109 Kelpiecross

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Posted 26 January 2020 - 10:52

 . . and yours.

 

 

    and mine.



#110 Kelpiecross

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Posted 26 January 2020 - 11:43

 Manny - a few suggestions:  convert the "broomstick"  into a simple tripod and seat arrangement  -   double or triple the propeller/rotor diameter  and the bloody thing might fly. 



#111 Kelpiecross

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Posted 26 January 2020 - 11:52

   Manny - can you give a direct link to the EPO patent covering  design No. 88?  I can't (yet) figure out the EPO systems.         



#112 Kelpiecross

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Posted 27 January 2020 - 04:29

  Manny -  my first thought about the "Witches' Broom"  layout  was that it was horrifyingly dangerous  (and it is of course - but so are  all these small, one person, VTOL  flying devices - and looked no more into the design.  (My comment above was meant to be sarcastic - referring to the danger).   

 

  But - on further study - I think  that it is quite a practical idea - far more so than the original "Flyer".  For the following reasons:

 

  It would be freestanding - meaning you would not have to carry  the whole contraption on your shoulders - meaning the minimum weight could also be a bit higher.

 

 Being coaxial the propeller/rotor size could be whatever it needed to be  -  also meaning the necessary power could be less - or to have more power in reserve.   Maybe about 15 feet or so rotor diameter? 

 

 The "Windsurfer"  body/weight-shifting   control at first seemed silly - but would probably  be very effective.    

 

 However - I would make one important change: - have the engine/reduction gearing etc.  at the very bottom   under the platform that the pilot stands on.  and have coaxial shafts running up to the rotors.  This would lower the centre of gravity  and give "pendulum" stability to the whole thing both when flying and on the ground/taking off etc.

 

 The idea of the pilot not being strapped in etc.  seems very dangerous - but in a way could be safer than not being  strapped to the accident etc.  in a take-off mishap.

 

 Maybe a lightweight  "safety hoop"  around the pilot?  - just so he/she doesn't accidently fall off in flight.    It could actually carry two people maybe? 

 

 The whole idea is still deadly dangerous -  but I think plenty of people would try it  - you might be starting a new craze.



#113 manolis

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Posted 27 January 2020 - 08:52

Hello Kelpiecross.

 

Here is the original WIPO / PCT document https://www.pattakon...00127091758.pdf and here is the granted European Patent https://www.pattakon...EP1697619B1.pdf

 

Alternatively you can go to EspaceNet and Search for EP1697619.

 

Thanks

Manolis Pattakos


Edited by manolis, 27 January 2020 - 11:18.


#114 manolis

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Posted 27 January 2020 - 08:58

Hello Kelpiecross.

 

The purpose of the Portable Flyer is to travel fast at long distances, not to loiter hovering for fun. The hovering is to be used for special cases (like rescue).

 

With the big (~15ft diameter) propellers you suggest,

it would be good to hover but not to travel fast,

say,

like the Chinook CH47 which is better for hovering / auto-rotation than the OSPREY V22, but worse for covering at high speed / high mileage long distances.

 

 

As for the “pendulum stability” you talk about, it is wrong.

 

Intuitively it seems correct, however it is wrong.

 

Like you, Mayman (JetPack manufacturer and pilot) thinks the same:

 

(the following is from another forum)

 

Quote from Mayman’s interview with New Atlas’ Loz Blain (https://newatlas.com...-speeder/58822/ ) :

 

Jetpack Aviation's David Mayman on his upcoming Speeder flying motorcycle

. . .

 

Loz:

 

Indeed, he's become one of the four superhero horsemen of a new personal flight revolution. Mayman, with his calm, methodical aviator's approach and multi-turbine jetpack, plays Buck Rogers. On the other end of the scale is Frenchman Franky Zapata, an extreme sports nut and former jet-ski champion whose turbine-powered Flyboard Air has been seen thundering across air and water throughout Europe and the US. Zapata makes a natural Green Goblin.

Then there's Richard Browning, a British martial arts master with a multi-turbine jet suit and a company called Gravity. Browning's suit places jets not only on his back, but on his arms, making him a shoo-in for Iron Man. And standing slightly apart from them all is ex-Swiss military pilot Yves Rossi, whose extraordinary Jetwing literally lets him dance with aeroplanes in the sky. It needs to be launched out of a plane, though, so while it certainly looks like an incredible experience to fly, it can't lift straight off the ground like the others.

 

The-Speeder-696x392.jpg

. . .

 

Mayman:

 

But the pilot has to be on top. So the thing is literally dynamically unstable. Inherently unstable. And it has to be flown by computer. So that's what we're building. And the prototype is exactly that. The engines are clustered together, we purposely put the weight above that, and then we try to fly it.”

 

End of Quote.

 

 

In the specifications of the Speeder of Mayman, while the take-off weight is unknown, the price is US700,000$.

 

*********************************

 

Gruntguru:

 

This is nonsense. In a hover situation with an axial thruster, the stability is the same no matter how low or high the CG might be relative to the thruster. An axial thruster always exerts its force along the same axis as that axis tilts. Although somewhat non-intuitive the situation is not the same as a parachute where the thrust remains upwards as the system tilts. (A parachute needs to be above the CG)”

 

*********************************

 

 

For most people the situation is “heavily non-intuitive”.

 

Despite his long flying (and manufacturing) experience, Mayman can’t get it.

 

So let me help with a drawing:

 

Broom_Two_Engines_Flyer.png

 

It is the “Broom Flyer” of a previous post modified by adding another OPRE Tilting propulsion unit at the bottom of the (yellow) pipe.

 

Suppose for a moment that the pilot is aerodynamically “transparent”.

 

Case 1: upper engine running, lower engine stopped.

Case 2: lower engine running, upper engine stopped.

In either case the pilot feels the same, and controls his flight the same way.

 

The force from the spinning propellers is along the yellow pipe in both cases.

In the one case the power unit is above the pilot, in the other case the power unit is below the pilot.

 

 

But the pilot is not aerodynamically “transparent”, which brings a significant difference of the two cases.

 

With the running engine above the pilot (i.e. with the pilot inside the downstream of the propellers), he has not only “weight displacement control”, but he has also aerodynamic control over his flight: his head and limbs act as flaps / ailerons / fins: deflecting a part of the downwash, they receiving reaction forces which give full control over the flight (yaw, pitch and roll).

 

With the running engine under the pilot (say, as in Zapata’s Jetpack) the pilot at take-off, at landing, at hovering and at low / medium speeds is based exclusively on “weight displacement” to control his flight. And this is not a full control.

 

Thanks

Manolis Pattakos



#115 Greg Locock

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Posted 30 January 2020 - 07:19

His feet got chopped off



#116 manolis

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Posted 30 January 2020 - 12:05

Hello Greg Locock

 

Not only his feet, but also his hands, ears and nose got chopped off.

Nevertheless he still can fly.

 

So:

Is it more stable with the upper or with the lower engine running?

Is it more controllable with the upper or with the lower engine running?

 

Thanks

Manolis Pattakos



#117 Kelpiecross

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Posted 30 January 2020 - 13:31

And lost his wig. 



#118 Kelpiecross

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Posted 01 February 2020 - 06:27

  I have to admit that I was not aware that a low(er)  CoG  doesn't make a helicopter more stable.  Judging by the internet, very few people in the world  do (or did) know - some still refuse to believe it.

 

 I think there is a lot to learn about helicopter aerodynamics etc.   Problem is if you find out in real life  you (or one) will end up like the bloke in your drawings -  footless/handless/wigless and possibly dickless.    

 

 Although the CoG  doesn't add to stability it may alter the moment of inertia etc.  possibly making the  rolling rate etc.  of the craft too quick to respond to just by weight-shifting etc.   Maybe that is why the "Speeder"  needs a copmputer - its low MoI  makes the roll rate to quick to respond to.

 

  Possibly having the engine etc.  at ground level  and the rotors at the other end of the pole/broomstick/fuselage would increase the MoI and make the whole thing more controllable rather than having everything at the top end.  It also would make it a lot more stable on the ground. .   

 

 Maybe the craft should have "built-in" stability?   Presumably having a fixed dihedral  ("coning") on the blades/rotors would give added stability  - I can't find anything on the net about this but it seems a reasonable idea.  

 

 I don't think there is much point  in having a relatively small diameter rotor - losing lift efficiency and possibly gaining  some speed.  The GEN H4  has a rotor diam. of 13 feet and yet has a claimed top speed/cruising speed of about  120/62MPH - which I think is fast enough for most purposes. 

 

 I hate to say it - but a lot of people have tried to make a small  one-person  helicopter but without much success.  Even the H4  seems to have been something of a failure despite (presumably) spending millions on development.

 I doubt if you (or I) could do any better -  especially with reasonably limited resources.  

 

 Having said all the above - I have an old lawn mower engine, some fence palings and an old rotary clothesline  - should be able to make a helicopter from these bits.  

 

    

 

 I think I personally would attempt to make a small VTOL craft  using some sort of "bladeless" (for safety)  technology.

 

 Maybe a centrifugal fan with entrained air type of gadget?  Did you know the front lift outlets on a Harrier are "cold"?  - straight from the engine compressor.      


Edited by Kelpiecross, 01 February 2020 - 06:38.


#119 manolis

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Posted 01 February 2020 - 15:13

Hello Kelpiecross

 

Landing Gearing

 

When the engine / propellers are above the pilot / rider (i.e. when the pilot / rider is in the downstream of the propellers), it is not only the aerodynamic control that is added to the “weight displacement” control, it is also that the legs / feet of the pilot can be used as the landing gear (the most adjustable and weightless landing gear).

 

Flyers.gif

 

 

 

You write:

“I don't think there is much point  in having a relatively small diameter rotor - losing lift efficiency and possibly gaining  some speed.  The GEN H4  has a rotor diam. of 13 feet and yet has a claimed top speed/cruising speed of about  120/62MPH - which I think is fast enough for most purposes.”

 

62mph / 100Km/h is a very slow speed for flying devices.

At such speeds almost all the energy of the fuel is consumed for “hovering”, i.e. to keep the flying device from falling.

  

 

 

You also write:

“I have to admit that I was not aware that a low(er)  CoG  doesn't make a helicopter more stable.  Judging by the internet, very few people in the world  do (or did) know - some still refuse to believe it.

 I think there is a lot to learn about helicopter aerodynamics etc.   Problem is if you find out in real life  you (or one) will end up like the bloke in your drawings -  footless/handless/wigless and possibly dickless.    

 Although the CoG  doesn't add to stability it may alter the moment of inertia etc.  possibly making the  rolling rate etc.  of the craft too quick to respond to just by weight-shifting etc.   Maybe that is why the "Speeder"  needs a copmputer - its low MoI  makes the roll rate to quick to respond to.

  Possibly having the engine etc.  at ground level  and the rotors at the other end of the pole/broomstick/fuselage would increase the MoI and make the whole thing more controllable rather than having everything at the top end.  It also would make it a lot more stable on the ground. .   

 Maybe the craft should have "built-in" stability?   Presumably having a fixed dihedral  ("coning") on the blades/rotors would give added stability  - I can't find anything on the net about this but it seems a reasonable idea.”

 

Now that the “pendulum stability” issue has been clarified, let’s proceed deeper.

 

Increasing the moment of inertia is not a solution.

It slows down the response to an external disturbance (say, to a gust of wind), but it also slows down the restoring to the initial position.

 

On the air there is nothing to abut on.

 

The only thing a pilot has is the thrust force.

If the pilot can instantly and effortlessly vector the thrust force towards any desirable direction, the problem of the flight control is about solved.

But to be able the pilot to vector instantly and effortlessly the thrust force, there are some requirements:

 

Quote from Portable Flyer “DEVICE TECHNICAL REPORT” at https://www.pattakon...oFly/index.html :

 

Zero vibrations, zero gyroscopic rigidity, zero reaction torque:

 

• The symmetry of the engine, the zero phase difference between the two synchronized and counter-rotating crankshafts, the common combustion chamber (same instant pressure on the piston crowns of the two opposed pistons, same (and opposite) instant torque on the two crankshafts), and the symmetrical load (two counter-rotating symmetrical propellers) rids the saddle (and the pilot) of all kinds and orders of vibrations (zero free inertia forces, zero free inertia moments, zero free inertia torques, and zero combustion vibrations of all kinds). This is an absolute requirement when a powerful high revving engine is to be tightened to the body of a person.

 

• The reaction torque is also permanently zero: no matter how wide the “throttle” is opened, or how abruptly the “throttle” opens or closes, there is no reaction torque (the only that happens is the increase or the decrease of the thrust force provided by the propellers).

 

• The symmetry and the counter-rotation of the propellers and of the crankshafts maintains the gyroscopic rigidity of the PORTABLE FLYER zero. Even when only the one engine is running (for instance due to a malfunction of the other engine), the gyroscopic rigidity is zero. Zero gyroscopic rigidity means that the pilot “instantly” and “effortlessly” can vector the engine/propellers (i.e. the thrust force) towards the desirable 4 direction, which is an absolute requirement for a safe, accurate and instantaneous control of the flight.

 

• Without zero inertia and combustion vibrations, without zero gyroscopic rigidity, and without zero reaction torque at the changes of the “throttle”, the control of the flight becomes slow, inaccurate, unsafe, uncomfortable and exhausting.

 

End of Quote.

 

Thanks

Manolis Pattakos



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#120 manolis

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Posted 19 February 2020 - 12:25

Hello all.

 

Take a look at this video:

 

 

and then notice the number of its views.

 

Thanks

Manolis Pattakos

 



#121 gruntguru

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Posted 19 February 2020 - 22:45

Is that Ken Wallis?

 

Much adored by 24gerrard AKA Autogyro AKA Rotodyne etc etc



#122 Kelpiecross

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Posted 20 February 2020 - 09:33

Is that Ken Wallis?

 

Much adored by 24gerrard AKA Autogyro AKA Rotodyne etc etc

 

 It is indeed Old Ken.   I saw him demonstrating his autogyro in Oz in the 1960s -  he really did throw that thing around the sky  - and he lived to 97!

 

 24G etc. was a bit of a  pain in the arse  but he shouldn't have been banned  (and neither should have  Cheapy been banned as well).  The Rotordyne was a good idea  (but very loud)  and he was right about  F1 gearchanges  having a slight gap in power flow despite being described as "uninterrupted".  

 

 Manny - why did you show the video?  This is a proper aircraft  - not two propellers on a stick.  


Edited by Kelpiecross, 20 February 2020 - 09:36.


#123 gruntguru

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Posted 23 February 2020 - 22:22

https://www.youtube....eature=emb_logo

 

Jetman can now take off from ground, hover and transition to winged flight.



#124 GreenMachine

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Posted 24 February 2020 - 00:14

The engines Jetman is using seem much bigger, and that stands to reason as they are no longer just for forward flight, but for VTO(L?) now.  Interestingly, for the demonstration (test?) he landed vertically, but for the extended flight by parachute ... fuel capacity limitations?



#125 scolbourne

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Posted 24 February 2020 - 01:27

I was told he lands by parachute because it would take so much fuel, and would shorten the total flight by a large percentage. I would be interested to know whether he has made the transition from level flight to VTOL mode though



#126 gruntguru

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Posted 24 February 2020 - 02:55

The engines Jetman is using seem much bigger, and that stands to reason as they are no longer just for forward flight, but for VTO(L?) now.  Interestingly, for the demonstration (test?) he landed vertically, but for the extended flight by parachute ... fuel capacity limitations?

I wonder if they are now fan-jets or high-bypass? Lower velocity with higher flow is much more efficient for low (and zero) speed operation.



#127 GreenMachine

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Posted 24 February 2020 - 09:27

A quick g00gle says no.  I am assuming that he uses off-the-shelf model RC jet engines (I am pretty sure that is what he started out with), and all I can find there are straight turbojets, no sign of a bypass.   Some pretty big thrust numbers there though.



#128 manolis

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Posted 24 February 2020 - 14:52

Hello all.

 

Quote from Gruntguru’s link (JetMan video https://www.youtube....eature=emb_logo )  

 

“In 8 seconds he had reached 100 meters height,

in 12 seconds 200m,

19 seconds 500m,

and reached 1000m in 30 seconds at an average speed of 130 knots.

At the end of a 3-minute flight punctuated by a roll and a loop at 1800m altitude, Jetman Vince Reffet opened his parachute at 1500m before landing back at Skydive Dubai.

. . .

Controlled from the ground by the human body, the equipment enables Jetman Dubai to reach speeds of 400kmh, as well as hovering, changing direction and performing loops.”

 

 

Supposing a total take-off weight of 130Kg (1,300Nt), the required power in order to lift in (30-19)=11 seconds from 500m height to 1,000m height is:

 

P = 1,300N * 500m / 11 sec = 60kW

 

Supposing another 40kW to cover the aerodynamic resistance (average speed 130knots / 240Km/h), the total power is some 100kW / 136PS.

 

 

Do four jet-turbines on a DeltaWing make a “proper aircraft”?

 

 

In the “JetMan / Dubai” video at 2:29 Vince Reffet is hovering, while at 2:36 the leaning of the Delta Wing is still far from horizontal.

During these 7 seconds, the DeltaWing is an aerodynamic obstacle.

 

 

Richard Browning with his JetPack, leans some 60 degrees from vertical (30 degrees from horizontal) at only 136Km/h:

 

Browning_Leaning_85_mph.png

 

(youtube video at https://www.youtube....eature=youtu.be ).

 

 

Vince Reffet’s average speed is 240Km/h where the aerodynamic forces are three times stronger than at 136Km/h ((240/136)^2=3).

 

 

 

Do Yves Rossy / Vince Reffet really need the DeltaWing?

 

The DeltaWing is useful for supporting the Jet-Turbines away from pilot’s body, and as the fuel tank.

It provides aerodynamic lift at medium speeds, at the expense of more instability at take-off and landing during windy weather.

 

 

Mayman’s JetPack:

 

JetPacks_vs_Portable_Flyer.png

 

is Rossy’s DeltaWing  JetPack after removing the DeltaWing and supporting the JetTurbines on pilot’s body.

 

Thanks

Manolis Pattakos  



#129 gruntguru

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Posted 24 February 2020 - 21:50

The deltawing is a far more impressive flying machine. The higher L/D gives it far better speed, climb, manoeuvrability etc.

 

You say "Controlled from the ground by the human body" If true, this is total confirmation of your assertion that the portable flyer hover mode can be fully controlled by body movements.

 

Is it true? Is the jetpack pilot moving his legs in the downwash to control it during hover mode?



#130 GreenMachine

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Posted 24 February 2020 - 23:22

Interesting question GG.  I imagine that movement of the upper body (leaning forward or back, tilting left or right) would be the primary control mode, maybe rotation/roll is achieved by manipulating the thrust of the jet column.  I didn't see any movement of 'flying surfaces' on the delta wing itself in the video.

 

Depending on the detailed implementation of Manny's device, something similar may be possible...



#131 Kelpiecross

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Posted 25 February 2020 - 04:29

  I know which one I am going to buy  - even I can  afford $3000!   400 miles range!   200mph top speed!  You Beauty! 



#132 manolis

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Posted 25 February 2020 - 05:30

Hello Gruntguru.

 

You write:

“You say "Controlled from the ground by the human body" If true, this is total confirmation of your assertion that the portable flyer hover mode can be fully controlled by body movements.”

 

 

I say the same for over a dozen of years in forums and in US and UK patents.

 

But this specific wording:

 

“Controlled from the ground by the human body”

 

is not mine. It is quote from the introduction of “your” XDubai youtube video:

 

 

JetMan_XDubai.png

 

 

 

You also write:

“Is it true? Is the jetpack pilot moving his legs in the downwash to control it during hover mode?”

 

 

A JetPach pilot cannot put his legs / feet in the downwash because they will be burnt (in a presentation of Mayman, when he lands with his JetPack there is a barrel with water wherein he puts his feet to cool down; in the case of the DeltaWing, the jet-turbines are away from pilot’s legs).

 

So, during taking off and landing the pilots of all JetPacks are restricted to use only the “weight displacement” control, wherein pilot’s center of gravity is displaced relative to the thrust axis.

 

 

Worth to mention here:

The term “weight displacement control” is not correct: what really happens is that the thrust axis is displaced relative to the center of gravity.

 

 

While the “weight displacement” gives stability, it cannot control pitch, yaw and roll;  this makes necessary some control-fins at the exit of some of the JetPack turbines:

 

Yves_Rossy_Vertical_Take_Off.png

 

The above photo (video at https://youtu.be/lK75XLUIKUk ) is from the first vertical take off of Yves Rossy, Geneva lake, Switzerland.

 

The same is the case for the Zapata JetPack: without control-fins at the bottom of two of his JetTurbines, he cannot yaw, not until he reaches a significant speed (say, 120Km/h).

 

 

 

In the case of the Portable Flyer the pilot can use, from before taking off to after landing, both:

the “weight displacement control”

and

the “aerodynamic control” (wherein pilot’s head and limbs, being inside the downwash of the propellers, receive and apply strong aerodynamic forces for pitch, roll and yaw control).

 

This offers a complete control over the flight from hovering to cruising to landing.

 

Thanks

Manolis Pattakos



#133 Kelpiecross

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Posted 25 February 2020 - 11:40

   Gas turbines become increasingly inefficient as they get smaller - that's why they were never used successfully in cars  -   "model"  jets are ridiculously fuel inefficient.    I would think a fan jet would be quite possible - you can buy a prop-jet or turbine helicopter engine.  

 

 It may be of interest to know that the early  modern model jet engines  used a Porsche  turbo compressor  section - in fact model  jet engines really come from  car turbo technology.    After all - all you need to do  is directly join the compressor section to the turbine with a bit of fuel supplied and Bob's your uncle.

 

 An odd bit of history is that the Americans had  quite advanced turbo engines before WW2 -  but it never occurred to them  to bypass the piston part and make a gas turbine.       



#134 manolis

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Posted 26 February 2020 - 17:23

Hello all.

 

Quote fromYves Rossy’s web site (at https://yvesrossy.co...st--jetman.html ) :

 

"After far too much silence since that magnificent formation flight with the Patrouille de France in October 2016, I would like to give you some news.
At the end of last year, I decided to end my relationship with Jetman Dubai.
. . .
I now have new, more powerful "JETCAT P550" engines that allow amazing flight performance such as climbing vertically at 180 km/h (see video), which is the speed at which a human body falls into free fall...

I feel like in my Mirage III at the time, except I'm just a little guy with a wing on his back who plays plane like a kid with his body movements, imagine!
With such an outpouring of power, vertical takeoffs and landings are within reach!
Thanks to the help of extraordinary people who spontaneously offered their help, we can present to you today what seemed impossible: the stable and precise hover flight of the wing-man assembly allowing autonomous take-off and landing.

 

3decollage.jpg

. . .

developed an electronic stabilization system that reacts to body movements.”

End of Quote

 

JetCat_P550_Spec.png

 

Based on the above specifications, let's make a few calculations:

 

The idling consumption of the four JetCat P550 of Yves Rossy’s DeltaWing is: 4*300ml/min = 1.2lit/min = 72lit/hour.

 

The full load consumption is 4*1650ml/min = 6.6lt/min = 396lit/hour

 

The maximum thrust force is 4*550N = 2200N = 220Kp = 480lb

 

With, say, 30 liters of fuel in his DeltaWing, Rossy can fly at full power for 30lt/6.6lit/min = 4.5 minutes.

 

With the same 30 liters fuel the four JetCat P550 turbines of Rossy can idle for 30lit / 1.2lit/min = 25 minutes.

 

The weight of the four turbines is 4*4900g = 196N = 19.6Kp = 43lb; in this weight it is added the DeltaWing weight, the fuel weight and the pilot weight.

 

With the 480 to 750 degrees Celsius exhaust gas temperature the pilot has to keep his limbs away from the exhaust gas.

 

The supersonic speed of the exhaust gas (2,129Km/h, Mach 1.7) causes extreme / unaffordable noise.

 

The cost of four JetCat-P550 turbines is over 50,000 euro; in this amount has to be added the cost of the rest DeltaWing “aircraft”.

 

Thanks

Manolis Pattakos



#135 gruntguru

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Posted 26 February 2020 - 22:02

F1 Turbo-machinery.

 

Pressure ratio - 4.0

Mass flow - 0.6 kg/s

Fuel consumption (complete engine) - 2,400 ml/minute.



#136 Kelpiecross

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Posted 28 February 2020 - 05:15

On the subject of  turbos and small jet engines - I remember (can't find a reference) a report  from the F1 turbo era  that claimed  that one team was injecting fuel  into the turbo  to make it act as a gas turbine  to keep the turbo RPM and pressure up while the engine throttle was closed.  It was quickly banned - but not a bad idea if the rules allowed.  



#137 Kelpiecross

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Posted 28 February 2020 - 05:26

Manny -  I thought this video on the early development of the Bell helicopter system very interesting.  It demonstrates that it is pretty tricky to get stability and that you don't get many "second chances" when testing experimental aircraft.

https://www.bing.com...eo+&FORM=HDRSC3



#138 manolis

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Posted 28 February 2020 - 05:50

Hello all.

 

The “JetMan-Dubai” team claims 400Km/h top speed for “their” Rossy’s DeltaWing.

 

 

Based on the JetCat P550 specifications, let’s see what the various numbers have to “say” and how they connect with each other:

 

 

With 400Km/h (111m/sec) speed and 2,200N total thrust, the power that pushes the DeltaWing forwards is:

 

P = 111m/sec * 2,200N = 245kW

 

The energy E provided per hour by this power is: E = 245kWh.

 

Supposing a specific gravity of 0.8Kg/lit for the fuel,

the 4*1650ml/min = 396lit/h fuel consumption per hour of the four jet turbines at full load gives a “BSFC” (Brake Specific Fuel Consumption), if we can call it so, of:

 

396lit * 0.8Kg/lit / E = 316Kg / 245kWh = 1280gr/kWh

 

and the resulting “BTE” (Brake Thermal Efficiency), if we can call it so, is:

 

80g/kWh / 1280gr/kWh = 6%

 

Where the 80g/kWh comes from?

80gr/kWh is the BSFC of an ideal engine running at 100% BTE;

When a giant marine low-speed 2-stroke Diesel engine consumes 160gr of fuel per kWh of mechanical energy produced, it operates at 80/160 = 0.5 = 50% BTE.

 

 

The total Exhaust Gas Power Output is 4 * 162.6kW = 650kW, while the power that actually pushes the pilot / DeltaWing is, as previously calculated, P = 245kW.

 

That is, the four jet turbines provide 650kW + 245kW = 895kW of power from which the 27% ( 245 / 895 = 0.27, i.e. about one quarter) pushes the pilot / aircraft forwards, while the rest 73% (nearly the three quarters) is lost in the exhaust gas.

 

This means that the jet turbines run at 22.5% BTE ( 80gr/kWh / (316Kg/h / 895kWh)= 0.225).

 

22.5% = 6% + 16.5%

 

The 6% of the fuel energy pushes the aircraft forwards,

the 16.5% of the fuel energy is lost with the high speed exhaust gas,

while the rest 77.5% of the fuel energy is never transformed into “mechanical” (or “aerodynamic” etc) energy.

 

 

In the JetCat P550 specifications the Exhaust Gas Power Output is given as 162.6kW;

Taking the derivatives of both sides of the kinetic energy equation:

 

E = (1/2)*m*v^2

 

it results:

 

dE/dt = (1/2) * dm/dt * v^2.

 

(the dm/dt is the mass flow; the speed v of the exhaust gas is constant 2129Km/h).

 

(1/2) * (Mass Flow) * (Exhaust Gas Velocity)^2 = 0.5 *0.93Kg/sec * (2129Km/h)^2 = 0.5 * 0.93Kg/sec * (591.4m/sec)^2 = 162.6kW, which is the Exhaust Gas Power Output given in the specifications.

 

 

In the P550 specifications the Specific Fuel Consumption (Kg/Nh) is given as 0.144;

0.144Kg/Nh = 1650ml/min * 60min/h * 0.008Kg/ml / 550N

(0.008Kg/ml is the fuel specific density, 1650ml/min is the fuel consumption at full load).

 

 

For the pilot, who is “in the open air”, the 400Km/h speed seems exhausting, if not unaffordable for more than a few seconds.

 

At lower speeds, say at 200Km/h, a substantially smaller portion of the power provided by the turbines is utilized to propel the aircraft, while the rest power provided by the turbines is lost with the exhaust gas; however the aerodynamic resistance falls more (it falls with speed square).

 

The lower the speed, the smaller the portion of the power provided by the turbines that is actually used to propel the aircraft, with the rest power being lost in the exhaust gas (in case of zero speed, while the turbines continue to consume fuel, all the energy they provide goes to the exhaust gas).

 

The higher the speed, the more of the turbine power goes to propel the aircraft, and the less power is lost in the exhaust gas.

 

 

Quiz:

 

Suppose Rossy wants to cross Calais channel (some 22miles / 35Km) with his new DeltaWing.

At which speed the required fuel is minimized?

 

 

According the previous,

at normal / affordable speeds, say from 100 to 150mph (160 to 240Km/h), only 3%, or so, of the fuel energy is propelling the Jet-Pack Flying Device; the rest fuel is burnt to accelerate the exhaust gas and to warm the atmosphere.

 

Even if the CO2 footprint was not an issue, the running cost gets extreme.

 

Worse even, the weight of the required fuel for a useful (say, 50Km) range becomes too high, and this weight has to be lifted by the JetPack Flying Device (just like heavy batteries have to be lifted by the electric Flying Devices).

 

 

In comparison, the Portable Flyer with its internal combustion engines and its propellers is many times more efficient than the JetPacks, it needs many times less fuel for the same range, it has many times longer range with the same quantity of fuel, it has many times smaller CO2 footpinrt, it has many times lower running and ownership cost, etc.

 

Portable_Flyer_Transmission.png

 

Thanks

Manolis Pattakos

 



#139 manolis

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Posted 05 March 2020 - 04:31

Hello all.
 
 
“GoFly is thrilled to announce that Team teTra from Japan won the $100,000 Pratt & Whitney Disruptor Prize
The $1,000,000 Grand Prize is still up for grabs so if you think you have what it takes to win it all, contact us at info@goflyprize.com. 
. . .
Lighter (*** GoFly Founder and CEO) said that GoFly is deeply proud of all the teams from around the world that took up the challenge because “they – like us – believe that personal human flight is a key component of our future, not just for commuting to and from work and leisure activities, but for important needs like the delivery of medical care and disaster relief.”
 
At the moment, however, she explained that no team is able to meet the requirements for the Grand Prize, but “we are hopeful that teams may do so in the near future.   In fact, we look forward to announcing the Grand Prize winner soon, and congratulate all of our teams on their innovation and inspiration.”
The GoFly Prize is supported by Grand Sponsor Boeing, Disruptor Award Sponsor Pratt & Whitney, as well as more than 20 national and international aviation and innovation organizations. “
 
End of Quote
 
 
Here is the Japanese “te Tra” Personal Flying Device, the winner of the US100,000$ “disruptive technology” award:
 
 
Enjoy its “flight” and “landings”.
 
 
Unless it is a “Top Secret”, 
shouldn’t they explain what is the disruptiveness in this concept than won the only prize awarded?
 
Thanks
Manolis Pattakos


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#140 gruntguru

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Posted 05 March 2020 - 05:06

The layout is clearly unique and therefore potentially disruptive.



#141 scolbourne

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Posted 05 March 2020 - 07:55

It is rather funny but I have been using the same design as above on an RC FPV micro drone. I first converted a normal drone into a hovercraft, by repositioning the rear motors and adding a skirt. (I really recommend trying this as it is great fun if you have an old drone lying around). Then I decided to add a wing made from a polysyrene foam meat tray. To make the wing add lift rather than pushing the model into the ground, my result was very similar to above.



#142 Kelpiecross

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Posted 05 March 2020 - 09:35

  Are they serious?  

 

 There are possibly literally hundreds  of homebuilt  VTOL flying devices that fly better than this thing  - and with pilots on board.

 

 Was the designer's uncle one of the judges?   


Edited by Kelpiecross, 05 March 2020 - 11:51.


#143 gruntguru

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Posted 05 March 2020 - 22:30

Certainly a hilarious video.

Kinda what you would expect though, for a gadget you finished building at 2:00 am then wheeled out for the judges to view the first test flight.



#144 Greg Locock

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Posted 06 March 2020 - 00:40

If I was a Pratt and Whitney shareholder I'd be asking some very pointy questions at the next AGM. 



#145 scolbourne

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Posted 06 March 2020 - 04:28

  Are they serious?  

 

 There are possibly literally hundreds  of homebuilt  VTOL flying devices that fly better than this thing  - and with pilots on board.

 

 Was the designer's uncle one of the judges?   

Most VTOL craft are very inefficient when cruising in level flight. Having the wing should vastly improve the range as the engines can be throttled back whilst still maintaining enough lift and speed.



#146 manolis

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Posted 07 March 2020 - 05:58

Hello Greg Locock

 

You write:

If I was a Pratt and Whitney shareholder I'd be asking some very pointy questions at the next AGM.”

 

 

 

Quote from http://newsroom.pw.u...y-Final-Fly-Off

 

Pratt & Whitney Presents The Disruptor Award at GoFly Final Fly Off

 

HARTFORD, Conn., March 2, 2020 – Pratt & Whitney, a division of United Technologies Corp. (NYSE: UTX), presented The Disruptor Award to teTra Aviation, a team from Tokyo, Japan, at the GoFly Prize Final Fly Off competition on Saturday, Feb. 29, 2020 at Moffett Federal Airfield at NASA Ames Research Center in Mountain View, Calif. Pratt & Whitney was an overall corporate sponsor of the GoFly Prize and also provided The Disruptor Award, a $100,000 prize that recognized the team that was truly innovative, who went beyond in developing their personal flying device. 

 

“Throughout the two years that we worked with the teams in the GoFly competition, we were impressed with the passion and commitment they had to innovate personal flight. This truly aligns with Pratt & Whitney’s 95 year history of transforming the future of aviation,” said Geoff Hunt, senior vice president of Engineering. “Our judging panel was impressed with the grit, determination, and creativity of these innovators from across the globe who are pushing the boundaries of what is possible. Although the choice was difficult, one stood out: teTra Aviation demonstrated the spirit of innovation, disruption and perseverance to see their demonstration vehicle through the challenges of developing a revolutionary new air vehicle.  In all, the event was a testament to forward-thinking and embracing innovation to power the future of aerospace and I applaud all the teams for their efforts.”

 

teTra_Disruptive_Tech_Award.jpg

 

Launched in September 2017, The GoFly Prize is a two-year competition where teams leveraged recent advances in propulsion, energy, light-weight materials, and control and stability systems to make the dream of personal flight a reality. Teams built personal flying devices that can be used by anyone, anywhere.

Participating in this project provides Pratt & Whitney the opportunity to support the next generation of aviation leaders. As a sponsor, the company has provided mentors and lecturers to help teams around the world develop the future of flight. With curiosity as a major component in the development of next generation of engines, working with inventors from all walks of life on a project that has the potential to make a huge impact on the advancement of personal travel was a perfect fit.”

 

Thanks

Manolis Pattakos



#147 Greg Locock

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Posted 07 March 2020 - 22:57

Specifically why is the board of P&W wasting MY money rewarding amateurish attempts that fail at every single task except the simplest (get off the ground). A 10 year old could have said "make a big drone with a seat on it".



#148 manolis

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Posted 11 March 2020 - 03:49

Hello all.

 

Pendulum rocket fallacy

 

Quote from https://web.archive....y/pendrock.html

 

By Jim Bowery

Copyright 2001

 

 

Getting a rocket to lift off and fly straight up is a little like a juggler balancing a pool cue on his chin:

 

saturnv.gif

 

This balancing act is so difficult that many intelligent amateurs have tried building rockets that have their engines at the top.

 

This is one of the more intelligent amateur rocketeers, standing next to one of his first rockets:

 

robert_h_goddard_and_liquid_fueled_rocke

 

Notice the black engine is at the top and the heavy silver fuel tanks are near the bottom with long pipes going all the way to the top of the engine. He thought placing the engine ahead of the bulk of the rocket would keep the rocket stable as it pulled the rest of the rocket upward.

 

PS: His name is Robert Goddard (more at https://www.nasa.gov...dr_goddard.html ). He invented liquid fueled rockets. He even did so when some respected authorities still thought rockets needed a medium against which to push. Newton's third law of motion already told them otherwise, but even respected authorities can be dumb, just like the rest of us. One liquid fueled rocket is the Saturn V you see in the picture of the balancing pool cue above, carrying 3 courageous men to the moon. They are in the tiny white triangular capsule at the top. Like most amateur rocketeers who are inventing new kinds of rockets, Robert Goddard was also courageous in his own way. A lesser risk of inventing things is that a few people who have low self-esteem, or who like things just the way they are, will try to find an excuse to ridicule your efforts. Don't worry about it. Rest assured you will provide them just the excuse they need. Explosions and governments are bigger risks.

Live and learn, stay out of jail, make it work, and tell the tale.

 

 

Intuition says that when you lift something from the side, it's center of mass will swing below the point of support and stabilize, like a pendulum that eventually lines up right under your point of support after swinging back and forth a bit.

 

So far so good.

 

By putting the engine at the top of their rockets, some amateur rocketeers intend to keep them upright during lift off. They think their rockets won't fall over like a pool cue without the juggler, but will just wobble back and forth under the rocket engine's support, like a pendulum, until it is completely stable:

 

firepend.gif

 

One of the two main places where intuition goes awry is in forgetting that a rocket engine is rigidly connected to the rest of the vehicle, so the engine's support of the vehicle changes direction along with the center of mass.

 

The other place where intuition goes awry is assuming that larger masses will fall faster than lighter masses. Galileo showed this false when he dropped two differing weights from the Leaning Tower of Piza and they both hit the ground at the same time. The top and bottom of a pendulum rocket will fall at the same rate so gravity doesn't stabilize it.

That means, if the rocket engine is just a tiny bit misaligned with where the center of mass is, the whole rocket will continue to turn:

 

Inverting the "pendulum" doesn't really matter.

firerot.gif

fireroti.gif

In both (above) cases the center of mass is misaligned with the direction of thrust.

 

 

In outer space, such a rocket would just go round and round in a big circle. In Earth's gravity, however, the whole circle falls at 9.8meters/sec**2.

 

That means the "pendulum rocket" launch profile looks something like this:

 

nolaunch.gif

 

If you are wondering how simple model rockets with fins manage to fly straight up, the short answer is, "Because that's the direction they were going when they got going fast enough that the wind on their fins made it hard to turn any other direction." The long answer can be found at Quantum Scientific's Model Rocket Stability page. If that long answer still isn't enough for you, and you have a serious desire to learn, check out The Guidance and Control Systems FAQ.

 

 

The author (Jim Bowery ) wishes to thank Henry Spencer for telling him three times that the pendulum rocket is fallacious and to Robert Goddard for inventing liquid fueled rockets (and for providing the author with a convenient excuse for being so obtuse).

 

Thanks

Manolis Pattakos


Edited by manolis, 12 March 2020 - 04:50.


#149 Kelpiecross

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Posted 14 March 2020 - 05:51

  I am still not quite sure I understand it.   If Goddard didn't understand it either I am in good company.

 

  I thought this was interesting and possibly useful:

 

 http://www.heli-chai...namics_101.html

 

It just demonstrates how difficult it is using very small diameter propellers  -   same 300hp engine lifts about three times as much  with a 30ft. diam. prop/rotor  as with a 6ft. propeller.  



#150 Greg Locock

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Posted 15 March 2020 - 05:02

What Goddard should have done was hinged the rest of the vehicle to the base of the rocket, then it would apply a corrective moment if the rocket bit tilts.