Modern "Blimps"

[hiflier]

I think the best thing for me would be to get to the nuts and bolts of where I'm heading with this. Maybe should've started a new thread IDK. In the Autumn of 2010 I read an article about what was called a stealth "blimp". It was intriguing and so I jumped in with both feet for more information. I saw pretty quickly that it was not really a blimp at all in the classic sense; more like a dirigible along the lines of the say, the Aereon Company's concept

I have visited many web sites and read numerous papers, some pretty far fetched TBH, in an effort to gain a clearer picture of any history or prototypes. Once my post count reaches 10 I can upload some examples but in the meantime to answer your questions. The applications could be either military or civilian but in either case I see the surveillance aspects as the stronger end usage. So regarding payloads, it woul depend on the sutuation. Deploy elite troops and comm and other light equipment comes to mind in a covert op againt terrorists domestically or abroad.

That said the construction of something of a stealth nature and in that capacity, would by default have to have an extremely low reflective signal as has already been brought up. AND BTW, thanks for responding. I would like to extend the discussion further into the viability of this type of craft. And then expand into the aerodynamics of design for getting the most bang for the fuel buck which, being for all intents and purposes an LTA, will or should involve some basic meteorology.

 

[hiflier]

I'll risk jumping ahead on this idea a bit if I may in an effort to broaden the scope of discussion. For the sake of aerodynamics that may allow for a faster forward speed, maybe in excess of 100 mph I would like to keep the envelope somewhere around 300 ft in length, 200 ft in width and roughly 20 ft in height. The top surface would incorporate a turbine type system drawing air from above the airship and either sending the pressured air into exterior vents. By closing selected vents it is conceived that it would create a vectored flight with enough thrust to still direct pressurized air to steering ports either side of the leading contour.

In a perfect world the best configuration for the envelope would be a deltoid shape as opposed to bullet shaped. I looking over the description for vectoring in the previous paragraphs perhaps there will be some agreement. The real detriment to such a shape is the tendency to collect rainwater as weight. As a start I have calculated an airship of this design to have a groos tonnage capacity including cargo at roughly 18 tons. Fairly light weight but then it's only half as long as the Zepplin USS Los Angeles.

This deltoid design also has only 1/4 the helium capacity of the Los Angeles at around 600,000 cubic feet and where the Los Angeles had a weight of 44 tons it had a cargo capacity of 20 tons. The deltoid being smaller would only have a lift capacity of 6-10 tons depending on it's construction materials, crew, fuel, and other on-board equipment. Also a surface of this size, with a shallow curvature, could accumulate as much as 70-10 tons of water so flying at an angle to the ground in order to shed water would have to be one of perhaps several maneuvers to avoid the accumulation.

My lack of knowledge though doesn't allow me to determine if a contra rotating turbine would be the best choice for this application although some intuitive thinking says that a contra rotating turbine would be the way to go if the airship's helium capacity was below what would be needed for neutral bouyancy. This is obviously not a design concept for high altitude flight. Being more stealth in nature a photo-voltaic upper skin might be superfluous for night deployment and may even succeed in adding unnecessary weight . Any weight additions should be in the area of reducing or eliminating any infrared or radar signatures.

 

[hiflier]

So what about efficient flight? It depends of course on whether a direct route to a destination is an imperative. Of course efficiency falls under many catagories and often it's a criteria that involves multiple factors rolled into one set of parameters. But for the sake of this discussion I will rule out or at least diminish the element of time.

If the window for delivering a payload is more in line with there not being a gotta have it now scenario then it may follow that efficiency will have a different definition. It could then be defined simply as fuel consumption. Or training. Or taking advantage of opportunities for experimental maneuvers. If time is not of the essence then other duties or requirements may be performed enroute. I can definitely see where multi-tasking within a flight plan would itself need a plan in order to get the most bang for the buck between point A and point B.

I am not so naive to think this is anything new so I'm only bring it up in order to refreshen the principle that that gettin from here to there should involve efforts to make the in-flight time frame mean something. Getting where one is going is important, don't get me wrong, but practicing surveillance techniques and going over safety procedure in the event of mishaps would be beneficial too.

 

[My2Cents]

Looks like that design will generate a lot on aerodynamic lift.

 

[hiflier]

It's difficult to say actually with me not being an aeronautical design engineer. I would think the main issue would be what any other airship would encounter with say a 40 knot head or tail wind, or wind from any direction for that matter. This particular design may even be more at risk for having the fore or aft getting caught at an attitude such that wind play havoc with the ability to maintain level flight.

If wind at the bow is 40 knots and the airship speed is 40 knots then keeping the nose from lifting or diving against a cummulative 80 knot force seems problematic. It's why I'd like to eventually discuss some aspects of meteorology. Nothing Earth shaking but more in line with common sense and common considerations that I would think most if not all airship personnel in all areas fron design to deployment already know.

Drawing the picture accurately means bringing all this stuff back up as part of the reality into which the concept must fit in order to make any sense. And part of that reality include some basic atmospheric flight dynamics especially when planning a 1-2,000 mile long mission. Truth be known, I've really enjoyed the process of research on the feasibility of such a craft and why it would be the coolest thing in the sky.

 

[hiflier]

So when working up some preliminary figures to support this concept a few years back I did indeed find that the physics would work just fine. To illustrate the point for taking the current plan into account: 300 ft x 200 ft = 60,000 sq. ft. Then 60,000 sq. ft. x 20 ft. in height = 1, 200,000 cu. ft. Divide that by 2 (as this is trianglar which is half the volume) and one gets 300,000 cu. ft.

Using the weight of plain old air (76.36 lbs per 1,000 cu. ft.) minus the weight of 1,000 cu. ft. of helium (10.54 lbs per 1,000 cu. ft.) one gets a net weight lift of 65.82 lbs per 1,000 cu. ft. Since gas impurities affect lift I'll finish out the estimate by using a more conservative capacity for helium at around 60 lbs per 1,000 cu. ft; which I think is more in line with engineering parameters anyway. Therefore, as per my post #22 above:

60lbs lift x 600 units @ 1,000 cu. ft. each = 36,000 lbs divided by 2,000 lbs per ton = around 18 tons total gross weight. From here working out the materials, crew, fuel, and other on-board equipment such as propulsion, electronics etc. should be next.

BTW, there wass an error in post #22 that I just noticed when re-reading it: a typo that said the weight of rainwater on the surface of this craft would be70-10 tons and I meant to type 7-10 tons. My apologies if there was any confusion on that.

 

[cdxbow]

Stratobus

The stratobus sounds a bit like what has been proposed here, but is not tethered, being able to keep station under it's own steam. There are some big players involved in this so it may come to pass, though the technological challenges could be great. Winds could propose a really big challenge, not just to station keeping but to survival.

 

[hiflier]

Not really as the shape and deployment of the stratobus is different even though the LTA principles remain the same. The airship I'm describing will have similar goals but with more versatility and it's designed more for low-level flight. After a couple of more posts I will be able to present some illustrations that will better show the concept. In the meantime just know that the volume of lifting gas will be in the neighborhood of around 600,000 cubic feet.

 

[hiflier]

I would like to mention that I've read numerous papers by various agencies both old and some within the past couple of decades that did mathimatical comparisons between conventional aircraft, blimp/dirigibles, and hybrids (like the type in this discussion) and all the conclusions favored the hybrids both for cargo-to-fuel ratios and in economic considerations. Certainly enough to have built and tested the P-791 in field trials. Hybrids are the way to go as long as (as I've mentioned previous) the element of time can be somehow waived in favor of stealth.

I look forward to the next few of posts for the opportunity to bring the subject of both "modern" AND "stealth" into a far more visual concept.

 

[hiflier]

And by the way, I would like to add that I've seen and read many of the Google patent and other patent websites along the way. Most fall short of this design and those that are close do not have all the features incorporated into the concept. Some are LTA's with conventional propulsion outside the envelope and others are strictly brute force lift. Nearly all have claims of heavy cargo capacities with the usual generalities like surveillance platforms etc.

This is my tenth post so I should be able to upload some support data and photos from here out.

Thanks for your patience. Let the fun begin!

 

[hiflier]

Let's start with this concept first. And don't worry folks, this isn't about UFO's. But it shows a center oriented impeller so you can get a picture of what I'm talkjng about when describing the propulsion idea in the delta airship. The Avrocar in the photo though is different in several areas- sadly, the most important being it's instability and utter failure as a prototype.

It also was trying to fly by sheer brute force by mechanically directing air underneath as well as across it's upper surface for lift. The fan design is the only thing I'm after here for application in top surface of the airship. In otherwords, as a sort of glorified helo:

 

[hiflier]

The next concept is illustrated best by showing you a Center Tunnel design in a drawing presented in 1949. The nose of the dirigible was to have a directional air-inlet feature which would allow the bow to raise, lower or be steered side to side. A complimentary stern application was to be incorporated to direct exhausted air from the "tunnel drive" feature in a variable direction as well to allow vectored thrust at the stern:

 

[hiflier]

This is th P-791 from Lockheed Martin which as you can see was field tested and is subsequently being moved to a commercial application as a heavy lifter. It demonstrates of course the power of an airship but incorporates none of the ideas I'm talking about:

 

[hiflier]

This design however could be an LTA with a contra fan in the top surface of the body directing thrust to the stern with exhaust ports on both the starboard and port side of the nose/cockpit and getting rid of the the outboard prop propulsion system altogether. It would then be a true LTA airship utilizing the Avrocar's central turbine propulsion along with the dirigible's internal tunnel drive system. The result would be maximun lift, quiet operation and reasonalbly fast forward speed and control. Add to those features the ability for extended hover time, zero runway take-off requirements and your on the way to what would be in my opinion the perfect stealth/surveillance package capable of being deployed in sensitive operations into remote or inaccessible locations:

 

[Volkodav]

Very interesting, I particularly like the strategic lift missions a large airship could carry out. That said a dirigible surveillance platform would also be of value.

 

[hiflier]

Yes, thanks, it is an interesting concept but again, not incorporating any new ideas. The only thing new is putting everything together into one package. Has this idea already been thought of? Probably. Would it be public knowledge? Hard to say. Has it already been built? I think it would be good if it has.

When I read the article about a Black triangular craft a few years back it really caught my imagination. The only places where there was any discussion about such a craft was on UFO Forums. In reading some threads I saw that there were numerous reports spanning about 25 years. I was unable to find anything in a more sensible, real-world reference work and it has taken quite a bit of time to dig up what I have presented here as a real-world working concept using today's technology which, as you can, see isn't all that high tech. I think this airship could be easily constructed and deployed.

I put this idea out to everyone to see if there is any input on furthering the design and whether or not anyone thinks it's any good or not. To me it's seems reasonable enough to delve into the subject of stealth but I needed to lay the ground work for dialogue first so the discussion wouldn't wander into little green men- I subject that I reject out of hand.

 

[hiflier]

This illustration is from the late 1960,s is referred to by the name "Dynairship". It demonstrates that the proposed design as I've said isn't a new one. Only the suggested propulsion application I've been talking about would be anything new:

 

[My2Cents]

The next concept is illustrated best by showing you a Center Tunnel design in a drawing presented in 1949. The nose of the dirigible was to have a directional air-inlet feature which would allow the bow to raise, lower or be steered side to side. A complimentary stern application was to be incorporated to direct exhausted air from the "tunnel drive" feature in a variable direction as well to allow vectored thrust at the stern:

I see a number of potential problems with this design.

1. Foremost of is the friction losses from the tube, especially from the inlet to the first propeller which would necessarily be at a pressure less than the surrounding.
2. The total volume of air that can be accelerated would also be limited by the tunnel diameter.
3. The tube itself which must be kept rigid to avoid turbulence induced resistance and flutter. Doing this in a very large lightweight structure will be extremely tricky.

I suspect that 4 conventional exterior propellers the same size would generate more thrust and this is the primary this design was never built.

A suggested improvement would be to place a first larger propeller at the entrance in the nose as an induction fan / compressor, then have the tunnel narrow for successive fans, sort of a trumpet shape.

Let's start with this concept first. And don't worry folks, this isn't about UFO's. But it shows a center oriented impeller so you can get a picture of what I'm talkjng about when describing the propulsion idea in the delta airship. The Avrocar in the photo though is different in several areas- sadly, the most important being it's instability and utter failure as a prototype.

It also was trying to fly by sheer brute force by mechanically directing air underneath as well as across it's upper surface for lift. The fan design is the only thing I'm after here for application in top surface of the airship. In otherwords, as a sort of glorified helo:

Ignore the downward directed air and concentrate on the Coandă effect from the blown air flow over upper surface of the blimp and design to take advantage, probably a oblong flying saucer shape to maximize the upper surface area, then position your engine outputs to blow air over the top to generate lift.

An important consideration that needs to be taken into account for any airship design is roll stability. A blimp is like a ship without a keel that has to rely on ‘ballast’ for stability by placing the center of mass below the center of buoyancy. Looking at any conventional designs you will note that all concentrated weights are located below the centerline of the gasbag, and often below the gasbag completely to maximize this effect.

 

[hiflier]

All good points but the Center tunnel aspect in the dirigible drawing was simply to show internal ducting at work. The Avrocar "saucer" has a turbo fan in the upper deck which was used to take full advantage of the Coanda Effect which was enhanced by an adjustable ring "flap" around the edge of the craft. It's the Avrocar's upper surface fan that I would like to see applied to the delta airship design. Not only for propulsion but to keep excess noise away from ground sources as well.

Being a fully capable LTA at 600,00 cu. ft. of helium the upper-surface fan will only be used as in inlet for the rear duct exhaust and smaller thrusters on either side of the bow. A low center of gravity would be aided by designing the fan motor low in the ship. Yes, there will be friction within the ducting but the velocity of the craft won't be that high really. Cargo will help with center of gravity issues as well.

The Fan in the Avrocar looks to be 6 ft or less in diameter. In a delta airship 300 ft long and 200 ft wide at the stern the fan in the upper surface could be a low velocity/high volume design, also for low noise, with a thirty or fifty foot diameter set of blades or turbo-type fan. Extra exhaust ports along all edges would help bleed off excess thrust to maintain headway with heavier loads.

The gyro effect of a horizontally oriented fan would help stabilize the craft against pitch and roll issues. You bring up valid concerns which shows you've given this some thought. I've been trying to find a design for several years that has all these features rolled into one craft but my searches have all failed.

 

[hiflier]

I like the idea behind the Airship Endurance VTOL:

Home - AirShip Technologies Group

but again, it's not based on an LTA package. Also, because it isn't applied to an LTA or even a hybrid design, the Coanda Effect-based flight requires constant powered lift. Stop the motors and it falls out of the sky. Still, I like it.