Tag: launch preparation

Risk Assessments, why are they so important?

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A risk assessment is a document in which certain risks of a project are set out and where you also set out the actions you are going to take to minimise or eliminate them.  We have created a risk assessment for our project.

When creating a risk assessment, the overall aim is to isolate a risk which can then be evaluated to discover the level of risk associated and finally put a controlled measurement in place to minimise or completely avoid any risks of danger or (in our case) the launch being compromised. The most essential part of making a risk assessment is planning. The more issues you can plan to avoid, the smaller the chance of issues arising on the day. Everyone should read the risk assessment and should be reminded of all the risks that involve them and their team on the day.

If, on the day, any issues do occur, it is important to be both reactive and proactive – meaning that resolutions should be created quickly and acted upon effectively to ensure the issues have a minimal effect on the overall outcome of the day.

Once we have released the balloon and the launch has been completed, we need to continue to plan for risks of the balloon’s journey. For example, we have fitted a radar reflector to our balloon so that any aircraft in the area can be made aware of the balloon’s location.

Finally, we also need to consider the risks relating to the balloon’s landing. We can take steps to try to ensure the landing zone is not a town or a busy road. However, we cannot be absolutely certain where our balloon will land.  Therefore, we have insurance for that risk.

References:

 https://www.britsafe.org/training-and-learning/find-the-right-course-for-you/informational-resources/risk-assessment/

https://www.brownssafetyservices.co.uk/blog/why-risk-assessments-so-important/

https://www.ccohs.ca/oshanswers/hsprograms/risk_assessment.html#:~:text=Risk%20assessments%20are%20very%20important,the%20public%2C%20etc.).

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How do we stop the balloon flying away (on launch day)? Ground Anchors

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Firstly, allocate a person who is going to hold the balloon, this person then must be weighed without the balloon and this measurement should be recorded. After the balloon neck is sealed to the filler nozzle with tape the allocated person will then take hold of the balloon at the tape joint and the balloon can begin to be filled with helium. The balloon should continue to be filled until the weight of the allocated person is at the desired weight (e.g.1.8kg) less than the original. At this point the helium supply should be turned off at the valve.

Once the balloon is completely sealed off (see picture below) the ground anchors should be attached (last year’s team used milk cartons filled with water). The balloon should then be allowed to lift ensuring that the ground anchors remain attached. Finally, once the remainder of the checks have been carried out and the payload attached, the ground anchors should then be cut with someone still holding the balloon. After the countdown to launch has finished the balloon should then be released.

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How do we know when we have filled the balloon with enough helium;

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In order to fill the balloon with the correct amount of gas, we need to be aware of something called “Neck lift”.

 

For simplicity, we will assume a 1kg balloon and a weight of 1kg for the payload and parachute.  Obviously if you put the balloon on some scales, we will get an accurate reading.

 

As the helium fills the balloon, the balloon starts to displace the surrounding air.  Because we are displacing air (which has a mass of over 1kg per cubic metre) with helium (which has a mass of about 10% of that), the more gas we put in the lighter the balloon becomes.  At about 1 cubic metre of gas, the balloon will be light enough to just lift off the ground.

 

Of course, at this point the balloon isn’t much use to us, we need it to lift the payload too.  So, we’ll put about 1 more cubic metre inside.  Now we’ve displaced enough air to give us about 1kg of lift.  Remember that our payload is 1kg, so if we closed off the balloon neck at this point and attached the payload, the balloon will not rise. Therefore, we need more lift to take the payload up into the air.  We need about 1 more kg of lift and so about 1 more cubic metre of helium.

 

How do we know we’ve put the correct amount of gas inside the balloon?  That’s where the neck lift comes in.  Remember that for the above example, we wanted 1kg to just lift the payload, and another 1kg to send the payload up at the right speed (5 metres per second), so that’s a total of 2kg (this is the neck lift). Neck Lift is how much upward pull the balloon has.

 

References:

http://www.daveakerman.com/?p=1732#:~:text=The%20Neck%20Lift%20tells%20you,without%20going%20up%20or%20down.

https://port1433.com/2017/07/17/hassp-1-what-we-learned-the-hard-way-with-pictures/

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How do you know when to launch;

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How do you know when to launch;

Importantly, you’ll want to make sure that the balloon lands somewhere you can retrieve it before the tracker runs out of battery – not too far away, and not in the sea! To have a look at a trajectory forecast. Most weather balloons rise/ drop at 5m/s but you should check the specifications of the balloon you have bought.

 

You’ll get the best images of the earth if it’s not too cloudy. If the launch is going to be a public event, you don’t want it to be raining. Also, it can be hard to launch a balloon in windy conditions. To ensure you have the most useful data, the more recent forecasts are more accurate, and forecasts should be closely checked when coming closer to the launch.

 

One website I have found for trajectory forecast is (Habhub.org) where using the launch details you can receive a forecast of the journey the balloon will take and its destination to ensure we can retrieve it.

References

https://www.metlink.org/observations-and-data/balloon-launch/

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