Theo Verelst Model Airship Page

A fusion between hot air balloons, helium filled zeppelins (bimps), and model aircrafts.
A bit of an article-wise text, scroll down to see the fun parts:
pictures and later on video captures of the flying prototypes.


From the early days of aviation onward, there has been a major seperation between propelled airplanes, using a wing or direct vertical lift, and balloons, which have intrinsic lift. The only bridge beween that seperation has been the airship, or zeppelin, or blimp, and it has been discarded for major aviation purposes, and even in the model world, it has recieved little attention.

In this text we will look into the possibilities of (helium) airships on a small scale, that is maybe up to cargo capacities of 100kg, and mainly in the less than 1KG equivalent lift range.

We will assess the possibilities of such a model airship, its potential, practical feasibility, and even present working prototypes that proof that all associated problems can be solved to arrive at a working model airship with high flexibility, at very acceptable cost, and with ample flying capacities.

Since the prototypes are realy that: prototypes, some assessment of the encountered idiosyncrasies will result in some major models of the physics and flying properties of the proposed types of models, enough to start building some more developed prototypes.

Please mind that even though the prototypes were done a a budget of maybe a hundred dollars, the efforts are seriously aimed at airships that can compete with model choppers and aircrafts for their flying capabilities, and beat them in some, such as the time of flight, manouverability, and safety. It is very reasonable to expect research in some of the proposed directions to yield interesting results that have a variety of applications.

Historical considerations.

Balloons and blimps are an interesting form of aviation, that may have been hampered by at least one or more of the following reasons: The remainder of this text makes clear that some of these limitations don't apply to model airships, others can easily be lifted or made irrelevant, and others are not decisive to conclude that model airships are not feasible.

Big airships, about 200 meters long, ar still around, and can be rented for about $300,000,= a month, which shows that at least there is some interest, and it is easy to understand that the comfort of a hot air balloon (completely silent flight), combined with far greater action radius (in the desired direction !) gives then a competative edge.

Hot air balloons have developed into a relatively safe form of aviation, and can already be enjoyed for prices around $200 per person.

Blimps are mainly a promotional gimmic, and usually not seen as aircrafts, but as static attention drawers.

Physical figures.

A balloon filled with helium, such as latex weather ballons or party balloons, can carry around 1.6 KG of load per cubic meter (1000 liters) of (at 1+epsilon bar of pressure, epsilon<0.1) helium volume, which is a roundish balloon with a diameter of about 1.5 meters. Of course this depends on: surrounding air pressure, temperature, and balloon thickness and stretchability.

The balloons themselves, the ones that I bought are latex balloons of the party type, costing around $10 a piece, depending on size weigh in the order of 50 grams, so when it is filled with helium it has zero lift at a diameter of about 30cm, and starts to increase lift with every liter of helium that it is filled with.

Helium costs me about 1-2 dollar cents per liter, in quantities from 1000 to 10,000 liters, excluding the deposit of $125 for the gas container, and $0.50 a day container rent after 1 days.

A remote control receiver weighs a few dozen or so grams, baby-cell rechargeable batteries weigh 25 grams each, delivering 600mAmp.h at 1.2 Volts, and servo control units (actuators) can weigh as little as 20 grams, the ones that I bought weigh around 40 grams.

A 2 channel remote control unit, transmitter, receiver, 2 servos, and battery container, with a range of at least 300 meters (40MHz band) cost me around $60,-, and it should be mentioned that the supplied receiver and servos nicely adhere to model remote control standards and can easily be fed by a custom pulse control signal, for instance to drive the height-control servo by a altitude sensor, in feedback fashion.

Model airship proposal: outline of the major properties.

Considering a balloon can easily carry half a kilogram or so of extra materials,

Highlighted feature: lift/altitude control


Observed model properties.

The latex helium balloons loose their helium slowly, but when the larger (thicker) balloons ar enot filled to their specified size, they keep the gas fairly well, a week or so of usefull lift without refil is reasonably possible.

The two balloon prototype with propulsion in the middle, under the balloons reponds to rudder motions as can be expected: the longitudinal directional stability is poor, which means that the redirected air flow along the rudder will result in a torsion on the whole balloon system, which is than accelerated to turn, and needs to be accelarated into stable forward flight by equivalent counter rudder. Since the amount of forward thrust from one cell is nice to make the model fly at moderate walking speed, it is nt enough to auto-stabalize the model in forward direction, so a rudder motion is often followed by sideway drift that is not easily compensated for, due to the large momentum (as result of the total weight) and the relatively smal compensating force from the propellors forward thrust. At higher flying speeds, this should be better, now the balloons' travelling speed is also not too limited by the forward thrust of the propellor, it simply doesn't develop a very high overall air speed. (Its a 5volt 140mA idle current motor, running at 1.2 V, with a 12 cm nylon prop).

Research and development possibilities.