Typical profile of a high altitude balloon, ascent, apex and descent

Leave a comment

There is quite a lot of variability in ascent and descent rates, but typically the balloon follows a steady and linear path both for ascent and descent.

The balloon will ascend rapidly at first, and then settle to a steady 4.6ms-1 to 5.8ms-1 for a typical 1-meter radius helium balloon.

The apex is usually around 25-35km. (approximately 100,000 feet, for perspective, 3 times commercial aircraft cruising altitude)

The balloon’s descent rate can be controlled, but it is recommended to aim for a steady 4 to 5ms-1 rate of descent. (controlled by the parachute)

Assuming the balloon reaches 30km, and ascends and descends at average rates, the ascent time would be approximately 1 hour and 40 minutes, and the descent time would be around 1 hour and 50 minutes, summing to a round-trip time of 3 hours and 30 minutes.

It is important to try and fill the balloon with the correct quantity of helium (considering payload mass) because the flight prediction software relies upon the anticipated ascent and descent rates of the balloon. An underfilled balloon will tend to travel much further. The typical distance covered depends completely on atmospheric conditions e.g. wind speed and jet stream, and could be from a few miles to hundreds of miles.

A typical balloon’s profile:

https://www.whitemountainscience.org/wmsi-blog/2016/11/29/profile-high-altitude-balloon-recovery credit goes to Bill Church

Uncategorised

How do we know where the balloon is after we launch it?

Leave a comment

Our team aims to use a combination of radio tracking, GPS, and cellular communication (SMS) to track our payload.

The balloon will have a GPS module which allows the balloon electronics to record the exact location of the balloon, usually every minute. We will use a GPS chip that has no height restriction.

The Global Positioning System (GPS) works by a system of satellites which orbit the Earth and transmit their position and the time where they currently are. The GPS receiver can then triangulate where it is in space – the GPS module requires several available satellites for an accurate lock. (typically, 5m)

The main way the balloon will communicate with us on the ground is by radio, transmitting on a legal wavelength of ~70cm which is a frequency of ~430MHz. In order to achieve this, the balloon must have a ‘transmission antenna’ and we must have a ‘receiver antenna’.

The balloon transmits on an ‘omni-directional’ (all-directional) antenna, and we will receive the transmission on a directional ‘YAGI’ antenna. The reason for this is that the balloon does not know where we are, so it must transmit in all directions, whereas we know vaguely where the balloon is, so we can intercept the balloon’s signal from a known direction.

There is a problem, however. The radio signal works on a ‘line of sight’ basis – meaning that if the balloon happens to go behind a house, mountain or tree for example, we would not be able to pickup the signal transmitted by the radio. Therefore, we might lose the balloon when it lands. There is a solution, and this is to use SMS messaging as a backup for the radio. This guarantees the recovery of the balloon if we cannot access the radio signal but can access the SMS signal. So why don’t we simply use the SMS messaging only? The reason is that the mobile phone antennae are specially designed to only output signal on a horizontal basis – it would be a massive waste of time, money and energy to output the signal in all directions – because people simply are not in space (probably). The signal output from the SMS antennas can only be picked up below ~6,000m.

A combination of radio and SMS must be used to maximise the chances of recovery.

GPS, Radio and SMS modules left to right respectively:

 

Uncategorised

Can we take a 360 camera up – 3 June 2020

Leave a comment

In order to take a 360 camera up, we must account for its mass in the payload. There are many options for 360 video – you may have heard of a Samsung Gear 360, but we have decided to use a Kanda Qoocam for its high quality 4k 30fps recordings in 360-degree video.

Battery life must be considered carefully, because we do not want to send a balloon up with a camera that records for 1 hour if our flight takes 3 hours. To solve this, we will use a battery pack to allow the camera to continue recording for the full journey.

The image quality of the camera is key also – low quality video is not attractive or useful. 4k at 30 frames per second is perfect for this, because it is high quality, and at a bearable frame rate.

File size is an issue too, because if we run out of storage when recording we could miss key elements of our flight. To solve this, we will use a 128GB+ micro SD card to fully cover the whole flight.

Stabilisation of the image is important – spinning images are problematic and quite vomit inducing (if we plan to use it for VR). To solved this, digital stabilisation is used to smooth the video and make it watchable.

Our plan to view the video is by using a VR Headset such as an Oculus Rift S – this is very capable of running VR seamlessly.

Oculus Rift S, Kanda Qoocam left to right respectively:

Uncategorised

Welcome Trainee Astronauts

One comment

Welcome to your brand new blog BalloonX Joe, Poppy, Jack and Natasha. This is your online learning journal which will evidence your progress and achievements. You will see in due course how valuable this is.  Use it as a brain dump, a way of sharing useful information, logging progress, recording failures and successes and documenting what you have learned.

To get started, simply visit your blog’s dashboard. I will forward your shared username and password in the WhatsApp group. Tag all the posts you write with your name as well as what your post relates to.

 

Uncategorised
1 … 12 13 14