Balloons and Parachutes

Balloons

A local company called InterMet Africa manufactures meteorological instruments. They order weather balloons from an international manufacturer called Pawan (http://www.pawanexport.com)

Fig. 1: 1000g Pawan weather balloon with parachute launched in Diep River, Cape Town

InterMet Africa keep stock of weather balloons and you can buy directly from them. They currently have stock of the following balloons:

Size Price
1000g R 1200.00
600g R 390.00
200g R 135.00
100g R 75.00

You can look at the following website to select the right balloon for your team:

http://habhub.org/calc/

In general, the mass of the balloon determines how large the balloon can expand. The more you fill the balloon at ground level the more payload mass it will carry but it will burst at a lower altitude. Alternatively, you can trade payload mass for rise rate with the same amount of gas and same burst altitude. The rise rate of 5 m/s is stipulated for meteorological reasons to standardise the data. You can easily launch with a slower rise rate although this will result in a longer flight and greater distance to travel for recovery.

Helium

You can get helium from Afrox Partigas. There are various outlets in the Western Cape outlets. You can get their contact details on the following page:

http://www.afrox.co.za/en/contact/location_maps/western_cape/Index.html

There are a few options for purchasing the gas in different canister sizes

Canister Mass Helium Mass Helium Volume Refill Price (exl VAT)
9 kg 0.13 kg 0.73 m3 R 382.59
30 kg 0.6 kg 3.36 m3 R 1149.95
72 kg 1.5 kg 8.4 m3 R 1810.49

Customers can rent the cannisters once-off or on account. For a once-off, the customer takes the cylinder for a fixed period of a few days with a refundable deposit of R150. On account, the cylinder is rented on a monthly basis for a non-refundable amount of R80. For inflation, an inflator can be taken for a refundable deposit of R193.52 or you can buy the inflator for R642.85. All these prices are excluding VAT.

Parachutes

Intermet Africa stock parachutes. They sell these for R150. They are simple plastic parachutes.

If you would like a more advanced parachute you can look at those made for model rocketry. Local rocket clubs tend to make their own due to the large expense of importing them. If you would like to make one from parachute material you can look at the guide on the following model rocket website (Richard Nakka's Experimental Rocketry)

http://www.nakka-rocketry.net/paracon.html

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