Basic structure of a near space high altitude balloon system:
Balloon: There a whole lot of companies which manufactures high altitude balloons especially for such experiments. Online stores are also available. After a whole lot of searching and contacting we found out 2 vendors.
Ningbo Yunhan Electronics Group Company Ltd
Payloads: The payloads form the vital part of any high altitude balloon experiment. Payload is nothing but the experiment that is to be carried out with the balloon in the near space. Likewise, in our case our, our ultimate goal is to look up in the sky and and study UV. So our final flight will consist of an UV spectrograph as the payload. But this work is in pipeline as we are beginners to balloon flights. So we as a team thought of having a series of balloon launches so that we can study these aspects in details. Our first flight is to be a tethered one in which we have planned to tie the balloon to a nylon rope and send the payload upto 200-300m. The payload at this level consists of a few cameras (which are available in market), GPS tracker, Data logger. Lets see each one in detail:
Cameras: After a whole 2 weeks of research on cameras we came across the most coolest of all and which would serve us the purpose; GoPro Hero. Its most suited for such purposes. But due to some inconvenience of online purchase we were unable to get it. So we settled down with Cannon Ixus 115hs.
Sat guide tracker: Tracking is always required in case of high altitude balloon experiments. As we know that GPS network is extended upto 18 km approx, we can have a GPS receiver on board the payload to help us locate its position during flight and descent. This would in turn help us for recovering our payload. Hence we planned to have this device. The vendor who supplied us with this device is
Data logger: A data logger (also data recorder) is an electronic device that records data over time or in relation to location either with a built in instrument or sensor via external instruments and sensors. Increasingly, but not entirely, they are based on a digital processor (or computer). They generally are small, battery powered, portable, and equipped with a microprocessor, internal memory for data storage, and sensors. One of the primary benefits of using data loggers is the ability to automatically collect data on a 24-hour basis. Upon activation, data loggers are typically deployed and left unattended to measure and record information for the duration of the monitoring period. This allows for a comprehensive, accurate picture of the environmental conditions being monitored, such as air temperature and relative humidity. For this purpose, we are using MSR145. This has selectable features which can be utilized as per our requirement. It has sales offices all over but we found one in India itself.
Recovery system: A latex balloon with sufficient helium is guaranteed to
burst, so a recovery system guaranteed to operate is vital. The parachute is
the simplest and most frequently used recovery device. The balloon carries the
parachute by its apex, which places the parachute in a position where it opens
immediately upon balloon burst. A length of load line (about 30 feet long)
separates the parachute from the balloon. Once the balloon bursts, we want what's
left of the balloon to drop over the side of the parachute, rather than on top
of it. For accurate details refer near space pdf.
Along with the parachutes, the most important thing is to have a flight termination
system in case of High Altitude Balloon for allowing the parachute to open up
and support it. There are various ways of having flight termination systems
(FTU). The one that we selected is to have a stopwatch to trigger the nichrome
coil with a current sufficient to melt it so that the parachute gets released
from it. With a stopwatch, the FTU acts as a stand-alone device that ensures
the termination of a flight in cases where the balloon becomes neutrally buoyant.
The components required for a FTU are available in the local electronic market.
Online stores for Parachutes: