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  #61  
Old 02.11.2009, 15:47
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Re: The Robot Apocalypse is closer than you think

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XYF Pogo is very stable design. It has the engine (propeller) mounted on top, like a Helicopter, just that the torque is balanced by the 4 horizontal fins. Whereas the Lunar lander has none of these, plus the blast engine being at the bottom can make it very unstable at take off and landing, hence the rocket like vehincles are launched from launch pads, while helicoters and aeroplanes can take off and land anywhere, except that for high speed jets, it has to be smooth surface.

Same thing as difference between airplanes which has wings mounted on top of the fuselages e.g. Hercules are more stable (pendulum effect) compared to aeroplanes with wings attached under the fuselage e.g. Spitfire. Relatively less stable provides for higher Agility. You can check that with any Aviation enthusiast.
Please stop! Actually, please continue, it's quite entertaining.

Can you explain why a helicopter or a prop-driven plane wasn't used for lunar landing?
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  #62  
Old 02.11.2009, 15:48
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Re: The Robot Apocalypse is closer than you think

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Because of how dense you are, Derv. Your sheer stupidity creates a massive gravitational pull, so they need more thrust to achieve orbit. This also explains how it's easier to take off from the moon.

Do you understand now?
You mean moon having 1/4 of Earth's gravity.

Less gravity would only mean you would need less Thrust while breaking through the gravitational pull of the planet (which you can do in matter of seconds), but would make it even more important to have Stabilisers?!

Plus you would still need enough fuel to travel through the distances in space, same as much as you needed while travelling TOWARDS the moon.

Its like saying you would need more fuel travelling from Geneva to Zurich then the return journey.. no?
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  #63  
Old 02.11.2009, 15:49
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Re: The Robot Apocalypse is closer than you think

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Please stop! Actually, please continue, it's quite entertaining.

Can you explain why a helicopter or a prop-driven plane wasn't used for lunar landing?
Lack of Power/thrust coz of prop-design vs jet engines.
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  #64  
Old 02.11.2009, 15:51
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Re: The Robot Apocalypse is closer than you think

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XYF Pogo is very stable design. It has the engine (propeller) mounted on top, like a Helicopter, just that the torque is balanced by the 4 horizontal fins.
Actually fins (or wings for that matter) dont balance torque. Try drilling a hole in your ceiling while standing on an office chair while holding an arm out to cancel the torque, see how well it works.


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Whereas the Lunar lander has none of these, plus the blast engine being at the bottom can make it very unstable at take off and landing,
You don't say. I wonder how a Harrier can take off with the center of mass above the center of thrust then.

A blast engine? Interesting.


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Same thing as difference between airplanes which has wings mounted on top of the fuselages e.g. Hercules are more stable (pendulum effect) compared to aeroplanes with wings attached under the fuselage e.g. Spitfire. Relatively less stable provides for higher Agility. You can check that with any Aviation enthusiast.
Oh wow. Same as "relatively less read makes for higher entertaining value on the internets".
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  #65  
Old 02.11.2009, 15:55
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Re: The Robot Apocalypse is closer than you think

Hey Dervaish, Nasa are trying to call you, they want you to design there next reusable space vehicle, they just realised, reading this thread, that they completely over engineered everything, and are really interested in your helecopter shuttle. Get in there!
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  #66  
Old 02.11.2009, 15:55
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Re: The Robot Apocalypse is closer than you think

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Lack of Power/thrust coz of prop-design vs jet engines.
Aha. I'm pleased to inform you a jet engine would develop exactly zero thrust on the moon, but please carry on.
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  #67  
Old 02.11.2009, 15:58
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Re: The Robot Apocalypse is closer than you think

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Aha. I'm pleased to inform you a jet engine would develop exactly zero thrust on the moon, but please carry on.
Then how do you create thrust on the moon?

Travelling through space, its not the engine but combusting the fuel, which is a problem due to lack of oxygen. The use liquid oxygen along with fuel ..if I can remember correctly.
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  #68  
Old 02.11.2009, 15:58
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Re: The Robot Apocalypse is closer than you think

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Its like saying you would need more fuel travelling from Geneva to Zurich then the return journey.. no?
Yeah, especially so if travelling from Geneva to Zurich would imply reaching escape velocity.
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  #69  
Old 02.11.2009, 15:59
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Re: The Robot Apocalypse is closer than you think

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Wrong again Derv.
Ok.. why do helicopeters have that small propeller at the rudders then?
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  #70  
Old 02.11.2009, 16:00
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Re: The Robot Apocalypse is closer than you think

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Travelling through space, its not the engine but combusting the fuel, which is a problem due to lack of oxygen. The use liquid oxygen along with fuel ..if I can remember correctly.
Would you mind rephrasing that in English?
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  #71  
Old 02.11.2009, 16:01
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Re: The Robot Apocalypse is closer than you think

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Actually fins (or wings for that matter) dont balance torque. Try drilling a hole in your ceiling while standing on an office chair while holding an arm out to cancel the torque, see how well it works.
How would you balance torque on a vehicle like XYF Pogo then?


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You don't say. I wonder how a Harrier can take off with the center of mass above the center of thrust then.
It can because theres enough thrust to lift its weight, and the wings provide for the stability.
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  #72  
Old 02.11.2009, 16:01
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Re: The Robot Apocalypse is closer than you think

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Ok.. why do helicopeters have that small propeller at the rudders then?
Probably because the fins don't cancel torque (but that's just a crazy thought i've had now).
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  #73  
Old 02.11.2009, 16:01
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Re: The Robot Apocalypse is closer than you think

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Ok.. why do helicopeters have that small propeller at the rudders then?
that's just a turbo boost when they need to get out quickly while under enemy fire.
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  #74  
Old 02.11.2009, 16:03
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Re: The Robot Apocalypse is closer than you think

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How would you balance torque on a vehicle like XYF Pogo then?
Now *that* is an interesting question. Pilot holding arm out of the cockpit as an extra fin?

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It can because theres enough thrust to lift its weight, and the wings provide for the stability.
A rocket also has enough thrust to lift its weight (one would hope...)... and the wings provide zero stability in hover flight. But please carry on.
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  #75  
Old 02.11.2009, 16:04
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Re: The Robot Apocalypse is closer than you think

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that's just a turbo boost when they need to get out quickly while under enemy fire.
Nah the propeller is used for amphibious helicopter operations. Everyone knows that.
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  #76  
Old 02.11.2009, 16:04
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Re: The Robot Apocalypse is closer than you think

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Ok.. why do helicopeters have that small propeller at the rudders then?
Derv, the Pogo was designed with Contra Rotating Turbo Props.

As Shorrick pointed out to you, fins have absolutely nothing to do with it.

Also, there's a difference between Jet engines and Rockets. Go and look it up. The Googles are very good for that, I hear.
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  #77  
Old 02.11.2009, 16:04
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Re: The Robot Apocalypse is closer than you think

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Would you mind rephrasing that in English?
Jet engines create thrust by combusting fuel (kerosene/jetfuel). For combustion/burning you need oxygen, which is in abundance within Earth's atmosphere. If you notice you have "air intakes" on the front side of aeroplanes, even cars and exhausts at the back.

In space there is NO oxygen hence you wont be able to burn fuel, hence the need to carry liquid oygen in tanks along with furl to help with Combustion.
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  #78  
Old 02.11.2009, 16:05
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Re: The Robot Apocalypse is closer than you think

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Nah the propeller is used for amphibious helicopter operations. Everyone knows that.
I stand corrected.
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  #79  
Old 02.11.2009, 16:07
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Re: The Robot Apocalypse is closer than you think

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Nah the propeller is used for amphibious helicopter operations. Everyone knows that.
Just like the froglets in The Clangers.
.
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  #80  
Old 02.11.2009, 16:07
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Re: The Robot Apocalypse is closer than you think

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Derv, the Pogo was designed with Contra Rotating Turbo Props.

As Shorrick pointed out to you, fins have absolutely nothing to do with it.

Also, there's a difference between Jet engines and Rockets. Go and look it up. The Googles are very good for that, I hear.
You're right, I missed the contra rotating turbo props in the pic

BUT still it has 4 horizontal fins, faily large in size too, as its need for extra stability while VTOL.
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