tutorials

Calculators - Burst Calculator

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SRWe’ve developed this burst calculator for you to work out approximately how high your near space craft will go and how fast it will travel. These are the two key things you’ll need in order to predict where your flight will land.

Here’s how to use it:

  • Select the balloon type you’re using
  • Enter the combined weight of all of the items (see list for common item weights below – you’ll need to weigh your payload and camera too! – don’t worry about adding the balloon weight, the calculator will take care of it)
  • Use the slider to tweak your ascent rate
  • Take note of the Free lift. This is the amount of pull the balloon needs above the weight of the payload. Therefore to work out what total lift your balloon needs, add the free lift to the payload weight.

As an example, if using an extra large (2000g) balloon with a 1000g payload, to hit 5m/s requires a free lift of 1.49kg. With the payload attached, this is how much extra pull the balloon should still have. When filling the balloon then, with some filling scales attached (but before we attach the payload), we need to see a reading of 2.49kg (That is 1.49kg free lift + 1kg payload)

We strongly recommend that you try to stay within the limits shown. Anything below 4m/s will almost certainly drift a long way, and anything higher than 7m/s will require a lot of gas! Similarly, you should try to keep the combined weight to the recommended weight rating for the balloon you’re using. One final word of warning – particularly heavy payloads may not ascend at a steady rate at the top of the flight. Instead they can progressively slow down, and even stop ascending (known as a floater). This is another reason to make sure your ascent rate is above 4m/s and should be well over 5m/s if you’re testing the limits with a very heavy payload.

Common item weights

  • Locator: 65g
  • Satellite Locator: 90g
  • Parachute: 100g
  • Black box: 190g
  • Cord (per m used): 5g (expect to use 8-10m on your build)
  • Payload: Our Space box starts at 220g and Space box mini at 80g before any cutting
  • Camera(s): ???? (expect approx 100g – 200g)

Balloon weight ratings

How much our balloons are rated to carry (recommended)

  • Medium: 700g
  • Large: 800g
  • XL: 1000g

Descent rates (approx)

Here are some approximate descent rates for our 50″ parachutes. Pick the weight closest to your combined weight. Be aware that descent rates can vary depending on the nature of the balloon burst.

  • 500g   :   3.9m/s
  • 600g   :   4.1m/s
  • 700g   :   4.3m/s
  • 800g   :   4.6m/s
  • 900g   :   4.8m/s
  • 1000g :   5.0m/s
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