Reusable Open Stratospheric Explorer (R-OSE)


A Multi-Balloon Stratospheric Platform for Remote Sensing Experiments

Project summary

The R-OSE project aims to design an innovative observation platform with very high spatial resolution (less than a meter) based on the use of small multiple stratospheric balloons. The use of small stratospheric balloons comes with a limit on the payload that can be lifted into the stratosphere. The typical payload is around 1.5 kg. By using a combination of more than one balloon, it is possible to significantly increase the mass of the payload and therefore increase the possibilities in terms of remote sensing projects. The R-OSE platform is not equipped with a separation system allowing the balloons to be released at the desired time. Instead, we count on the fact that at maximum altitude, one of the balloons will burst so that the remaining thrust force will not allow the balloon to remain buoyant. The payload will then begin its descent, slowed by the thrust of the remaining balloons and the friction of the parachute. R-OSE consists of a platform in the shape of an inverted pyramid on which the flight controller, an alarm and a GPS/Satellite beacon are placed to more easily find the payload at the end of the flight. The platform is also equipped with floats and a wind vane to limit its rotation. On the lower tip of the pyramid, a universal joint is used to attach the gondola containing the observation instruments. The universal joint keeps the gondola pointing towards nadir. The flight chain is made up, in order from bottom to top, of the gondola, the platform, a pivot, a parachute and the balloon(s). An important part of the project consists of the creation of a simulator to determine the burst altitude of the first balloon as well as the ascent and descent speed. This information is typical input to trajectory simulators for stratospheric balloon flights.

The platform

The pyramidal structure

The platform is basically made of a combination of carbon fiber rods and triangle shaped 1 mm thick aluminum sheeting. The rods are tied to the aluminum pieces with two nylon ties and glued with epoxy. The scientific payload is typically suspended to the lower vertex with a universal joint.

We also use a kevlar rope to attach the lower vertex of the structure to the swivel by using a taut-line hitch knot that allow us to tighten the rope in order to get a better support of the payload. To learn how to make the taut-line hitch knot, check that video https://youtu.be/_FfrIS8WQHc

Each aluminum piece of the 3 top vertices are aimed to support different parts of the system. First they are tied to the swivel located above at around 3 meters. On one aluminum piece, we install the wind vane. On the second we install the GPS/satellite device (a SPOT trace device) and the controller PCB. On the third we install the 5V 5000 mAh powerbank. The powerbank is thermally protected by an isolated enclosure made with a piece of extruded polystyrene.

On the side of the lower vertex, we installed the buzzer and a 2 alkaline #23A 12 Volt batteries pack. We also made an isolated enclosure for that battery pack.

Flight controller

Components

ItemModelLink/provider
GPSQuescan UBX-M10050-KB GNSS M10 G10A-F30https://www.aliexpress.com/item/1005005621100756.html?spm=a2g0o.order_detail.order_detail_item.3.72d4f19cXGoMjL
AccelerometerADXL345https://a.co/d/5aTT2Ct
RTC moduleDS3231https://a.co/d/fkBLotb
DC-DC chargerDD06CVSAhttps://a.co/d/gOwvy5d
MagnetometerHMC5883Lhttps://a.co/d/ha0TeUV
Barometric Pressure/Altitude/Temperature SensorMPL3115A2Adafruit https://www.adafruit.com/product/1893
Raspberry pi zero W https://www.pishop.ca/product/raspberry-pi-zero-w/

PCB

Battery pack

GPS/Satellite beacon

We are using the VCC 3.3 pin, the GND and the RX and TX. RX and TX are respectively connected to GPIO 15 and GPIO 14 on the Raspberry pi zero W.

Buzzer

We use the buzzer to facilitate the retrieval of the platform after the flight. We selected the CLT1083 buzzer and power it with 12 Volt batteries. For convenience, we added a switch to activate the buzzer just before launch. The buzzer is available from Amazon https://a.co/d/ftuuRn9 but any other buzzer should be use without problem as long as it emits loud enough (~ 100 dB à 12 V CC / 30 cm).

Floats

The floats are made of 3 pieces of extruded polystyrene 1 1/2 in thick of 17 cm x 10 cm. There are attached with two nylon ties to the 3 downward edges of the pyramid. The will be helpful if the platform land in a water body. But we also sometimes use them to capture warm micrometeorites in the stratosphere.

Wind vane

Software

https://github.com/gal1leo31/r-ose

To download the code:

cd
mkdir git
cd git
git clone https://github.com/gal1leo31/r-ose.git

The flight chain

Parachute

Swivel

Balloons

Gondola

The multi balloon simulator

The launch procedure

The mass budget

ItemMassProvider
Balloon600ghttps://the-rocketman.com/high-altitude-weather-balloons-hab/
Platform without 18650 batteries but including battery supports and insulation and buzzer and batteries600g 
Parachute200ghttps://the-rocketman.com/
3-Point Y Harness with open loops and swivel8ghttps://the-rocketman.com/weather-balloon-y-harness-and-shock-cord/
Two 18650 batteries for the controller100g 
Controller PCB with sensors and raspberry pi zero w  
GPS module10g 
Floats<78g 
Printed gondola356g 
2 action cams + hum and cables176g 
Battery cams121g 
TOTAL2249g  
Total PAYLOAD1649g 

Mass budget flight 1 (One 600g balloon)

ItemMass
Balloon600g
Platform without battery bank but including battery supports and insulation, buzzer and batteries600g
Platform battery bank96g
Parachute200g
3-Point Y Harness with open loops and swivel8g
GPS module10g
Floats<78g
Controller PCB with sensors and raspberry pi zero w50g ?
gondole moins secondaire sans batterie pour 2 cameras mais avec les fils de camera et avec muons complet1012g ?
Experience ouate mouillée et caméra mini Montcalm27g
Clé sonomètre13g
Battery bank caméras96g
TOTAL2190g

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Useful links

$StopWatch