Jetpack rides (flies?) again

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Bruno Ogorelec
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Jetpack rides (flies?) again

Post by Bruno Ogorelec » Thu Jun 17, 2004 12:10 pm

Here I'm at it again. The jetpack. Here's a crude sketch.

The mushroom stalk on the pilot’s back is the engine assembly, carried in a backpack frame. The mushroom head is the thrust ducting. It is gimbaled and the pilot can tilt it in all directions.

The engine assembly consists of an arbitrary number of pulsejets blowing hot gas upwards. They are encased in a cowling lined with some sound-deadening material. The cowling also ducts fresh air from below and around the engines.

All engines blow into a common thrust augmenter above them. The augmenter duct has a ball joint between the engines and the thrust ‘wing’ assembly, so that the 'wing' can tilt in all directions while the hot gas delivery is uninterrupted.

The thrust ‘wing’ assembly is wing-like because it is streamlined with an elliptical-section carbon fiber casing. Within the streamlined casing is an annular (ring) duct into which the gases are fed tangentially from below, as if through wheel spokes. All the hot gas produced by the engines is thus made to run around the circular duct.

Two thrust ‘arms’ depart tangentially from the ring duct towards the ‘wing’ tips, laft and right. One occupies the leading edge of teh 'wing' and the other the trailing edge.

At the tips, they turn downwards into nozzles you can see sticking below. The nozzles contain simple small vanes that turn on command from the twist-grip controls on the ‘handlebars’ to provide yaw control. Forward and back control and left and right translation (which would be called pitch and roll in an aircraft) are provided by tilting the ‘wing’. (There's no conventional pitc and roll for a jetpack. Only the 'wing' tilts but the pilot remains more or less upright.)

Why the common thrust augmenter and the relatively complex ducting? So that the thrust is uniform all the time and equal between the two nozzles regardless of how many engines you have and regardless of whether one of them dies. With any problem the thrust diminishes, but stays symmetrical.

The 'wing' center is empty and can be used to stow a parachute.

By having the engines encased in a cooling duct, I have addressed some of the heat problem. It should also help cut noise. The result is bulk, but not necessarily much weight. If most things are done in carbon fiber, which is a good structural material for this kind of application, weight will be kept within tolerable bounds.

The only metal parts I would use would be the engines. Maybe the gimbals. Fuel tanks can be strapped to the frame sides.
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Bruno Ogorelec
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Post by Bruno Ogorelec » Thu Jun 17, 2004 3:00 pm

Here's an even rougher sketch of what's inside the thrust 'wing'.
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paul skinner
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Post by paul skinner » Thu Jun 17, 2004 3:14 pm

They've since gone out of business, but Solotrek looked kind of like what you're proposing.

http://www.solotrek.com/devhistory.html

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Post by Bruno Ogorelec » Thu Jun 17, 2004 3:35 pm

Principal Skinner wrote:They've since gone out of business, but Solotrek looked kind of like what you're proposing.
Solotrek was overkill. Huge cost, much machinery, yet little safety. I liked the basic idea, but there was no way to do what they did cheaply.

This machine is just a lot of empty ducting. No, it won't be as cheap as a bicycle, but might cost about as much as a fancier motor cycle, which is, I think, quite acceptable.

The ducting may look complex but once you make the female molds of the upper and lower half, it's just so much laying of wowen mat, soaking in a binder and curing. Then you bond the halves together. The design must be made very carefully, but production would not be complex.

You needn't even use pulsejets. Strap a Williams fanjet onto the backpack and have it blow into the ducting and you'll fly, allright. It's been done before. easier than with a pulsejet. Here's a picture. My aim is not to have something no one has ever done, but to do something that is fun but does not cost half a million.
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Post by Bruno Ogorelec » Thu Jun 17, 2004 3:37 pm

BTW -- I drew almost everything larger than necessary. With some thought and development I am sure the package can be a lot less bulky.

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Post by Mike Everman » Thu Jun 17, 2004 3:58 pm

Too cool. What could be more fun? And you can make it in your garage!
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AirBike

Post by Mark S. » Thu Jun 17, 2004 4:19 pm

This machine is just a lot of empty ducting. No, it won't be as cheap as a bicycle, but might cost about as much as a fancier motor cycle, which is, I think, quite acceptable.

Speaking of flying motorcycles check out this Link:

http://www.geocities.com/alliedaerobiker/

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Post by Tom » Thu Jun 17, 2004 4:43 pm

Webspace as cheap as it is, and they are using geocities? Not the best appearance if you want to be taken seriously.

Tom
Experience speaks more then hypothesizing ever can. More-so in chemistry.

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Post by Bruno Ogorelec » Thu Jun 17, 2004 5:20 pm

The air bike looks very sexy, but it is a dubious concept to my eyes. I am not an expert on this, but somehow, I'd like to hang from my lifter, not sit on it. I know that helicopters will fly just fine with the rotor underneath, but I'm not sure that it applies here, too. The footprint is just too damn narrow for comfort, I think.

Correct me if I'm wrong.

These guys are on the Internet for fun -- they've been there for years with no new developments. But, the renderings are very sexy looking.

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Post by Bruno Ogorelec » Thu Jun 17, 2004 5:24 pm

I would like your opinon on whether gimbaling and tilting the entire 'wing' makes sense, or should it be rigid and the two jet nozzles at the tips gimbaled? Bell Labs went for the latter solution and got the thing to be compact and neat, but I think a big gimbals is much easier to build for a home enthusiast than two small precision ones.

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Post by Mike Everman » Thu Jun 17, 2004 5:40 pm

I think it is most definitely two, at the exits. They gimbal collectively for forward/reverse, and differentially for yaw. Simple.
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Post by Bruno Ogorelec » Thu Jun 17, 2004 5:47 pm

Mike Everman wrote:I think it is most definitely two, at the exits. They gimbal collectively for forward/reverse, and differentially for yaw. Simple.
What about lateral translation? If you have the ability to hover, might as well be able to slide left and right. You'd have to have joystick control, really. Two joysticks at the ends of armrests.

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Post by Mike Everman » Thu Jun 17, 2004 6:08 pm

I'd just skip lateral movement for simplicity's sake. This needs to be as failsafe a linkage as possible. If one side fails, you're dead, and lateral movement is not essential, it would just "be nice". A similar trade-off is made on private hovercraft, that is: they have no reverse. They'd need a much more expensive feathering prop or diverters to do that, so you just deal with this limitation, since the "workaround" is natural. You'll still be quite agile, and will unlikely be hampered by it.

A simple bar with hand grip to each nozzle would be safest. If one starts to get sticky, you just pull harder and look for a place to land, preferably near a beautiful farmgirl... Oops, mind is drifting....
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Post by Mike Kirney » Thu Jun 17, 2004 6:19 pm

I like your drawings, Bruno. You should publish a graphic novel sometime.

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Post by Bruno Ogorelec » Thu Jun 17, 2004 7:02 pm

Mike Kirney wrote:I like your drawings, Bruno. You should publish a graphic novel sometime.
Thank you. I did something of the kind in high school, but the superintended thought it too 'graphic' and I had problems. Those were late 1960s and -- while flower power was very much on in the street -- schools did not take kindly to that sort of liberty.

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