Required hardware:
- a roll of black 33 gallons trash bags.
VERY IMPORTANT! Use 13 µm thick black bags ( .5 MIL )!
- a measuring tape,
- scissors,
- a knife with a rounded tip and small dents on the sharp edge
- a roll of tape 19 mm x 33 m
- 11 meters of sewing thread.
- a white out pen,
- a light weight basket (small plastic can : yogurt is fine),
- a living room !
Building Time: 3 to 6 hours with 2 people
For a single person it is difficult and, above 2 people, the others are only giving useless advises!
Process:
0 - Clear some space in your living room!1 - Unroll and put on top of each other 12 bags. Align the lower part of the bags (side with the bonding).
2 - Cut as close as possible from the bottom to eliminate the bonding (12 mm).
3 - Cut with a knife all the bags along one of the edges.
4 - Once opened, this makes plastic sheets of around 167 cm by 100 cm.
5 - Building the lower part of the balloon : Stack 6 sheets making sure edges are aligned.
6 - Fold this stack in two, so that one longest side covers the other one. You obtain a 167 cm by 50 cm stack.
7 - Using the white out pen, mark a point at 20 cm from the fold (pli) and draw a line to the other corner (see drawing).
8 - Cut along the line using the scissors.
9 - Unfold the stack of plastic sheets. /
10 - Align side by side 2 sheets with the narrow ends on the same side. Tape them together along the whole length. One person aligns the sheets with a slight overlap while the other one tapes.
11 - Repeat this task five times and roll the assembled sheets while progressing.
12 - Building the half upper balloon : Repeat operation 5 to 11 with the remaining 6 sheets following the drawing. Assembly is slightly more difficult due to the cranked shape.
13 - Balloon assembly : put side by side the upper and the lower balloon assemblies (tape should be on the same face). Assemble with tape.
14 - Close the balloon by taping from top to bottom (tape on the same face).
15 - Finish-up the top of the balloon to avoid leaks !
16 - Turn the balloon inside-out like a sock so that tape is inside the balloon. Tape outside is not pretty and bonding is more exposed to sun rays.
17 - Reinforce the bottom of the balloon with tape close to the edge (5 mm).
18 - Tape six 1.5 m sewing threads onto the bottom of the balloon, making sure that at least 6 cm of that thread are taped to the balloon (see picture). Do not apply tape on tape as bonding is not very good.
19 - Tape the 6 lines to the yogurt cup.
20 - Attach another 2 m line to the bottom of the yogurt to hold the balloon.
21 - Your balloon is finished. Weight should be around 220 gr! /
How to launch your balloon:
· Choose your day : clear sky, little or no wind, early in the morning before thermal activity· Lay the balloon on the ground with the opening in the wind if any.
· Inflate the balloon: several solutions:
- with a fan, it is easy
- with your arms! It is still easy enough for a small size balloon: knees down in the opening of the balloon to maintain one of its sides on the ground. Grab, with your hands, the other side and move it up and down to let air get into the balloon.
· Very fast the sun is going to heat the air in the balloon and the balloon is going to rise. It will finish inflating itself thanks to the sun heat.
· Load the basket. The biggest the load is and the smallest the vertical speed and the maximum altitude are.
· Hold the balloon using the line attached to the basket.
· After 5 to 10 minutes, the balloon is capable to lift its load.
· Release the balloon being careful that the wind will not take it towards electric lines or buildings.
· HAVE FUN
FAA Part 101: regulation applicable to free balloon
It seems that our small balloon has no applicable regulation!101.1 Applicability.
(a) This part prescribes rules governing the operation in the United States, of the following :(1) Except as provided for in §101.7, any balloon that is moored to the surface of the earth or an object thereon and that has a diameter of more than 6 feet or a gas capacity of more than 115 cubic feet.
(2) Except as provided for in §101.7, any kite that weighs more than 5 pounds and is intended to be flown at the end of a rope or cable.
(3) Any unmanned rocket except :
(i) Aerial firework displays; and,
(ii) Model rockets :
(a) Using not more than four ounces of propellant;
(b) Using a slow-burning propellant;
(c) Made of paper, wood, or breakable plastic, containing no substantial metal parts and weighing not more than 16 ounces, including the propellant; and
(d) Operated in a manner that does not create a hazard to persons, property, or other aircraft.
(4) Except as provided for in §101.7, any unmanned free balloon that --
(i) Carries a payload package that weighs more than four pounds and has a weight/size ratio of more than three ounces per square inch on any surface of the package, determined by dividing the total weight in ounces of the payload package by the area in square inches of its smallest surface;
(ii) Carries a payload package that weighs more than six pounds;
(iii) Carries a payload, of two or more packages, that weighs more than 12 pounds;
(iv) Uses a rope or other device for suspension of the payload that requires an impact force of more than 50 pounds to separate the suspended payload from the balloon.
(b) For the purposes of this part, a gyro glider attached to a vehicle on the surface of the earth is considered to be a kite.
[Doc. No. 1580, 28 FR 6721, June 29, 1963, as amended by Amdt. 101-1, 29 FR 46, Jan. 3, 1964; Amdt. 101-3, 35 FR 8213, May 26, 1970]
A solar balloon is an ultralight hot air balloon that only uses heat radiation from the sun to provide lift. Experimental technique nowadays, this innovative technique can be used for tethered or free flight, for recreational flying or other uses. The envelope is built from a black polyethylene plastic film 13-15 or 20 microns absorbs incident solar energy.
A small solar balloon 4 meters in diameter can lift 2 kg weight, one of 11 meters diameter can lift 55 kg, one of 14.5 meters diameter can lift 120 kg, etc.....
Phenomena which affect a solar balloonlast changed : 25/08/2008
Gravitation or terrestrial attraction: Very useful for getting back down to the ground!
Weight is the vertical downward force which Earth's gravitation exerts upon a body, proportional to its mass. P = m . g.
The principal factor is the mass of the warm air contained in the envelope. Mass of one cubic meter of warm air at 35°C : about 1.145 kg.
Example : There are 1735 cubic meters of warm air in a 14.5 meter diameter balloon ... The mass is more than 2 metric tons ! . To this must be added the masses of the envelope (polyethylene + adhesive tape + load tapes), plus the load circle, the harness and its support lines, any ballast, the pilot and parachute, and of any flight accessories.
"Any body immersed in a fluid experiences a force opposed to its weight of magnitude equal to the weight of the fluid which it displaces". This principle was formulated by Archimedes more than twenty centuries ago! It is the Archimedean buoyancy.
In this case, the displaced fluid is air at the ambient temperature. The body immersed in this fluid is the balloon!
Since the warm air inside the balloon is lighter than the ambient air, the resultant force is a vertical upwards force: the aerostatics force or "lift". The lift is about 0,8 Newton per cubic meter (i.e. 80 grams per cubic meter).
In a stable atmosphere, if this force is greater than the weight of the balloon's envelope and its load, the balloon will rises!
In a stable atmosphere, if this force is just equal to the weight of the balloon's envelope and its load, the balloon will remain at a stable altitude! /
Volumetric mass and temperature differential :
Volumetric mass is the mass per cubic meter or the quantity of matter mass per cubic meter. The volumetric mass of air at 15°C is 1.225 kg/m3. A balloon made of black plastic film inflated with dry air absorbs enough solar energy to raise its interior temperature significantly. The hot air expand and this reduces the volumetric mass of the warm air within the balloon quite substantially (there is less air molecules per volume unit). Thus this bubble of warm air rises because it is lighter than ambient. /
At sea level and at atmospheric pressure of 1013 millibars (hecto Pascal's or 29.92 in.hg.) we can note:
Air temperature / Mass of one cubic meter of air / Difference between masse of airat 15°C
0°c / 1,292 kg/m3 / +67 gr
15°C / 1,225 kg/m3 / 0 gr
25°C / 1,184 kg/m3 / -41 gr
70°C / 1,029 kg/m3 / -196 gr
100°C / 0,946 kg/m3 / -279 gr
150°C / 0,835 kg/m3 / -390 gr
/ · mass of one cubic meter of ambient air at 15°C : 1,225 kg
· mass of one cubic meter of warm air at 35°C : 1,145 kg
· difference between these masses : 80 grams per cubic meter of air, which produces an aerostatics force or lift (according to International Standard Atmosphere - ISA).
· If the temperature differentials increase the aerostatics force will increase also. This way a solar balloon 4m (13 ft) diameter has lifted a load of more than 3 kg with -8 °C ambient while it usually lift 2 kg during the summer.
For more information, volumetric mass of helium is 0,176 kg/m3. The Volumetric mass difference with ambient air (the lift) is about 11 Newton per cubic meter (i.e. 1.1 kg per cubic meter)! But it is very expensive and leak easily.
Other important considerations for a solar balloon:
· Heat radiation from the sun: his is more intense when the atmosphere is thin (at altitude) and when the sun's rays fall perpendicularly upon the receiving surface. Outside the atmosphere it amounts to 1,360 W/m2 (the solar constant), and on the ground to about 1,000 W/m2 (when the sun is overhead and the sky is clear). The average strength of solar radiation over the year, day and night, all weathers) is from 120 to 260 W/m2.
· Reflected solar radiation: Depending upon the type of soil and the cloud conditions (if you're above them they are a very good reflector), a fraction of the solar radiation is reflected upwards. Albedo is the proportion of reflected solar radiation: ice, fresh snow - 0.6 to 0.8; bare soils and deserts - 0.3 to 0.4; forests and agricultural areas - 0.1 to 0.15 ; water - 0.05 to 0.1 ; above clouds - stratus 0.4, cumulus 0.8. The albedo of black polyethylene is very near zero, which means that it absorbs all the solar radiation and reflects none.
· Thermal transmission: This is the heat exchange of the envelope to the outside air or inside air.
· Inside heat convection: Local differences in temperature close to the envelope surface cause local air density variations, which generate circulation movements, and these tend to mix the air so that the air temperature is equalized.
· Outside heat convection: Local differences in temperature close to the envelope surface cause local air density variations, which generate upward circulation movements.
· Effects of porosity of the polyethylene (negligible) and of losses through the envelope.
· Heat loss through the base (load circle) and through the top of the envelope (through the valve).
Useful jargon:
· Archimedean buoyancy or Archimedean force: the weight of the ambient air displaced by the balloon.
· Aerostatics force or lift: this is a vertical force, directed upwards, equal to the difference between the Archimedean buoyancy and the weight of the hot air contained in the balloon. It varies to the volume of the envelope, the temperature differential, the altitude, the pressure, etc.
· The weight of a solar balloon : This is the sum of the weights of the air contained in the envelope, the envelope itself (polyethylene + adhesive tape + load tapes), the load circle, the seat and its support lines, the ballast, the pilot and his equipment, his parachute, and the flight accessories (instrumentation).
· Empty weight: this is the weights of the envelope (polyethylene + adhesive tape + load tapes), of the load circle, of the seat and its support lines.
· Effective useful flight load: The weight of everything the balloon is carrying : pilot, parachute, ballast, and flight accessories.
· Maximum useful load: this is the maximum load that the balloon can carry in optimum conditions: volume at maximum, etc.
CNES-Education has a very detailed large teaching web site about helium balloons (in French) at http://www.cnes.fr/
Introduction of solar hot air balloonlast changed : 19/09/2007 / /
/ A solar hot air balloon takes advantage of the fact that solar radiation provides about 1000 Watts per square meter. A balloon made of black plastic film and inflated with dry air absorbs enough solar energy to raise the temperature of the air on the inside; this reduces the air density significantly.
This hot air bubble is lighter than the ambient air. The balloon rises.
Mass of 1 cubic meter of ambient air at 15°C : 1,225 kg.
Mass of 1 cubic meter of air at 35°C : 1,145 kg.
The climbing aerostatics force or lift is therefore 80 grams per m3.
A solar hot air balloon for human flight can be piloted vertically by using a valve at the top of the balloon: the solar balloon is oversized compared to its load. To fly at a desired altitude (level flight), the valve is opened slightly. To ascend, the pilot closes the valve completely. To descend, he opens more the valve.
It is possible :
· to arrest a descent quickly (obstacles or strong descents) by closing the valve and dropping ballast : 20 kg of water or of sand),
· to descend quickly (turbulence, vertical movements) by opening a valve at the top and a panel at the equator,
· to use automatic altitude regulation for level flight. /
Animated sequence 110K : How the solar balloon works ? /
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Solar Balloon - Ignacio Espila Navarro: