Air~Speed

Design, Secure Funding, Build and Fly Worlds Fastest Airship.
 
March 9th, 2011
 
Basic layout has been selected, now a scaled model will be built and tested.  Below figures are just guestimated at this time.
 
Type:            Semi-Rigid
Crew:            Two
Length:         35 meters
Height:          5  meters
Width:          (Varying)  7- 11 meters
Powerplant:   2x  Jet-Tip  200 hp each
Volume:        2000 m^3
Max Speed:   150 kph
Range:           200 kilometers
 
 
 
 
 

Now we're talkin.   But what is Jet Tip?  Jet engine or a simulation?   Internal cockpit or gondola?   Landing gear?   External thrusters for vector control while landing and taking off?  Flesh this out for us, it sounds interesting.

Here is the information on the propulsion units:

http://tipjetusa.com/

and

http://www.tipjet.com/

and wouldn't owning a backpack version be great:

http://www.tipjet.com/tj_pho_gallry.htm

I have been fascinated  by  Tip Jets for a while now .  Its neat  how  they  pressurize  by centrifigal force in rotor blades .  But  as always  , theres always a catch . In  this case  its  buying and shipping  the  Rocket Grade Hydrogen Peroxide and its cost per gallon . Also as with  jets or rockets  ,  the  MPG  isnt  very good ether .
 But  here is  a  nice link  . http://www.peroxidepropulsion.com/

In the www.tipjet.com page it says:

"The G8-2 engine was designed around the fuel, liquid propane; primarily because of propane's "double energy" content. The energy available from propane comes from the compressive energy resulting from its low boiling temperature (-43.8 degrees F), as well as from the heat of combustion. By taking advantage of propane's natural compressive energy, the design of the engine is simplified. In addition, propane is safer than gasoline, readily available, easily stored and controlled, and it is inexpensive. Propane weighs 4.23 pounds per gallon, and releases 21,690 btu/lb when burned (oxidized)."

While the horsepower (and lightweight) is what is needed to propel Air~Speed, maybe switching over to propane tipjets would be easier to fuel up the ship?

Indeed it would !   I did not  know  they  were propane powered . 

Does anyone know the pressure of liquid propane?   I know that CO2 is about 900 psi when liquid, and that could be boosted if run through a heat exchange such as a gallon of very hot water, or around the exhaust system of another engine.   My 8 year old nephew asked me to make him a jet pack, I said, "...Okay..." and set about designing one using CO2 as the propellant.   What would be cool is if there was a degradent catalyst that would break down CO2 into oxygen and carbon, for it would also produce a lot of thrust.

Think this chart might answer the question?

http://www.engineeringtoolbox.com/propane-vapor-pressure-d_1020.html

I kinda missed the applicability to airships on this one. A jet tipped rotor ( mentioned above ) are usually 20 to 30 feet in diameter. Somewhat big for an ultralight. Jet tipped props have been investigated, but are esoteric enough to be out of our price range.

Notes:

1. The G8-2 is a multiple stage aspiration actuated ram jet. When it first came out it was among the worst of fuel hogs. The current website looks like they have made some improvements on this. The noise problem probably won't go away. Ram aspirated engines are not efficient, but they are cheap if you're good at welding stainless steels.

2. The cute little helicopter ( Dragonfly : http://www.peroxidepropulsion.com/) is Hydrogen Peroxide tip propelled.  ( There seemed to be some confusion between tipjet.com and tipjetusa.com ) The last time I checked the Dragonfly comes to your house after you pay $120K bucks. Not affordable unless you sell your dog, your wife, and the best behaved kid out of your bunch. Never mind ..... 13'th amendment.

3. Unmentioned is the fact that as you expand propane, it cools off and the vapor pressure drops. Since the pressure is feeding your aspiration, this is bad. So you have to heat the pressurized propane liquid or provide some serious pumping past a heater without back flow or back pressure. ( Hear the scales creaking under all the weight?)

4. The faster you go, the more the dynamic pressure affects the envelope, the more you have to add structural weight to support the thrust vs drag stress on the ship.  I don't get something for nothing , You don't get something for nothing.

Happy thinking!

1. All of the tip jet rotors are going to have a noise problem. Its a characteristic of the configuration and the primary reason that they haven't been widely adopted for helicopters.

2. They might be willing to sell components and perhaps make variants for this application.

3. There are ways around that, you can use the propane to cool the rocket body and nozzle the way liquid fueled rockets do. You can also control pressure drops with strategic changes in diameter.

4. Yes, but that is another issue separated from propulsion choice.

Since last week's conference call where we talked about tip jets, I've been thinking about it. The potential light weight and efficiency of the system is attractive.  One way to overcome the noise problem would be to have a small electric motor with a high torque gearbox that drives the the rotor when close to the ground and for "trim". Call it a "trolling mode". Once you get high enough and far enough away, you can light the jets and scream away.  I don't think it will be the solution for making super fast airship, more a way to build a light, compact, and simple propulsion system, compared to an equivalent one driven by a conventional motor.

I have to admit, the idea of a propane jet tip prop which can be lit on fire to heat the propane for better expansion while making a ring of fire exhaust come out the back of a fan duct sounds pretty cool.   Can a ram jet work on such a small little intake spinning in a circle?   Propane, as a duel energy fuel sounds like a great idea.   It's light weight, affordable, under pressure and can be made self heating and then have combustion energy as a jet or rocket motor.   I don't know enough about ram jets to say if it could work under mach one tip speed.  But find a way to burn the jet stream at the back of a cylinder which in turn will heat the propane to higher pressures sounds like an ingenious idea.   It does not sound like a garage project, however.

Okay, 200 psi for propane is not very much.   Co2 is about 900 and comes in 20 ounce bottles.   I don't know how long that would last.   It would not be cheap, that's for sure.  And you would definitely need a heat source to improve endurance and power.

Um... can you edit that. I'm not sure I understand what you are trying to describe. Sorry. I'm dense today.

Sorry, I am distracted.   The "Upload Files" button stops at 99 % every time and the "Insert Image" button will not accept any Url from photo bucket I try to use.  I am sick of the useless sophistication of the web.   What I am trying to describe above is a small  rocket motor on the prop to spin it.  It has an air intake like a ram jet.   It runs on propane, but the propane needs to be heated to expand it's pressure.  So wrap the fuel line around the little ram jet tube, once it is spinning fast enough, ignite the propane to give extra boost, this will in turn heat the propane up significantly.   It would produce spectacular rings of fire, if it worked.

Hey Boldt, would you consider using a multi stage ducted fan jet motor?   Say you want to use 24 hp on a 45 inch prop but to produce 220 lbs of thrust, but you want it in a smaller package, so take four 6 hp motors and stack them in a tapered duct with 24 to 20 inch propellers of increasing pitch with decreasing diameter.    Each stage speeds air up, compressing it slightly and pulling the back pressure off of the previous stage propeller.   You have the same hp but are using it spread out.   I have never seen it done, and it requires the high speed motors available today in the Model Plane RC industry.   I am trying to upload a drawing.

Attachment: Multi stage ducted fan jet.bmp (3824.0KB)

You need to reduce the size of the pictures and save them in a more internet friendly format.  Something like a jpg or gif.  Your drawing for example is over 3 MB in size. That is probably why you are having trouble uploading.

Thanks, James.

The H202 tipjet is really more of a tiprocket right? There is no need of an air intake unless it is used as a thrust augmentation device. 

There is also no need to put the jet at the blade tips because there is no need to aspirate. Just use an air reaction engine to turn a crankshaft driven prop... This way, you solve the noise problem. This would essentially be a steam engine without the boiler. 

Could be integrated to increase static lift too, in several ways.

Still need to see cost of H202 per gasoline gallon equivalent. 

Having the jets at the tips gives you a leverage advantage vs. driving the hub. its actually the only way it works. Otherwise you would have to build pretty much a turbofan engine...

I like the idea of using small propane pulse jets. They would still be loud, but no where near as bad as supersonic ram jets or the like.  You can even keep the tips leisurely and subsonic. 

Will still require tricky precision fabrication though. That I think is the biggest drawback to any tipjet scheme. Motors, redrives, and props are common and easy to obtain.  A custom tipjet application is going to take some engineering work and not cheap assembly.

Just the rear half of a turbofan since I am talking about a mono-propellant. There is no air intake or compressor, just a fuel line and an exhaust. Torpedoes have used the system I am talking about. H202 + catalyst + reaction engine -> steam + O2 + torque.

It looks like htp (high test peroxide) costs about 60 dollars per gallon of gasoline energy equivilant. That may not be that big of a deal if using htp yields cost saving and weight savings elsewhere. Plus system efficiency might reduce the cost of htp compared to gasoline.