This post is an addition to the "Egg-shaped [simple] balloon" published earlier today. I choose the "Very small aerostat flying at dusk, Eastern Ukraine" as a main image. This photo was shot two-and-a-half years ago, at the peace time. Now we are under attack from Russia. It would be great to have a numerous tactical-size surveillance aerostats here! Personally, I would suggest something like several U.S.-made PGSS and PTDS. And even couple of TARS [ref_1] would be quite helpful on the Southern Ukraine, facing the threat from the sea and the occupied Crimea.
But let's drop away the politics, and focuse on the balloons, self-made things, and wild nature preservation.
The Kharkiv group "LTA for Ukraine" is working since 2003, to introduce the modern lighter-than-air technology, i.e. aerostats and airships, into Ukraine. We are a non-governmental, self-supported grass-root initiative.
As I noticed in my very first post, our work is significantly inspired by the materials generously provided as Open Source by the PublicLab.
Here is a part of the story, how we proceed. We started with the ambitios goal to model the steamlined shape of one of the historic airships, the Norge airship by Umberto Nobile. This resulted in design of 8 gores for outside envelope, plus the internal catenaria curtain and the ballonet pocket. The eight outside gores are 4 pairs of differently-shaped gores. The effort was started year 2004, abandoned for some time (by the way, we had here in Ukraine a pro-democratic Orange Revolution year 2004/2005, and the anti-Putin Revolution of Dignity year 2013/2014). The flying copy of the Nobile airship is not done yet, but the flatten-nosed version of that "aerostat" shape is used by us since 2012.
Few words about this micro-aerostat. It's length is about 2.5 meters, and the gas volume 27.5 cub.feet. The envelope is made of polyethilene, 0.015 mm (15 micrometers) thick, heat-seamed. The main features of the design are 1) internal suspension system, or "catenaria curtain", and 2) semirigid frame, made of carbon fishing rods and styrofoam bars. The rigging system is rudimentary -- almost non-existant. The flying line is attached directly to one point at the aerostat's frame, at the belly, near the nose.
This micro-aerostat has a name "Uchbovy" wich means in Ukrainian "A one for training".
Two photos below show the "Uchbovy" aloft, and Mikhail piloting it. We here find it quite helpful to use a fishing rod for navigating the micro-aerostats and balloons near the ground. One can fly the thing aloft way easily over the obstacles such as bushes, small trees and fences. Also the flexible rod is compensating the excessive drag when facing the gusts.
Fig. 1 and 2. Above, the micro-aerostat aloft in mid-day. Below, the team member Mikhail A. Blinov working as the pilot, or "winch operator".
The next photo, I hope, clarifies the design. The additional rod at the bow is used to position the pieces of modeling clay -- we did this experimenting with balancing and pitch.
Fig. 3 Micro-aerostat flying at sunset.
This streamlined shape was of much help for understanding the mechanics of tethered aerostat, and we still use the envelope, after several field repairs.
The over-simplified rigging, as was used in our first experiments, has significant faults. The aerostat with the flying line attached to its belly near the nose, is unsufficiently stable and in gusts can sometimes "overkeel" -- i.e. suddenly quickly rotate around its horizontal axis 360 degrees. The "anti-rolling" rigging scheme should follow the one described in the Kitoon patent. We plan to test this in near future.
The idea to make an appendix (or gas-feeding sleeve) of such a diameter, that the human' arm can be introduced through it into the envelope was suggested by M. A. Blinov, the "LTA for Ukraine" quite valuable member. The holes and cuts of the envelope are repaired with sticky tape "on the fist", in field situation.