Page 1

Credits

Page 2

Avionics

Page 3

Nacelle

At 40,000 meters and -60 ° C, the nacelle will have to protect cameras and sensors.

To recover the video data, sensor data, and any expensive equipment on board, the realization of the spacecraft is of fundamental importance.

It will be made starting from sheets of expanded polystyrene, hand cut and shaped so as to leave the minimum internal empty space.

With this arrangement the spacecraft will have a greater thickness and therefore better isolate the electronics from the very low external temperatures (up to -60 ° C).

In addition to this, its manual construction will allow us to position within specially created rooms and in different positions, the sensors, the camera, the batteries, and antennas. In this way, the most sensitive components at low temperatures, will be positioned closer to the center in order to be more thermally insulated than less sensitive.

Another important thing is to preheat before testing and launch the batteries up to 30 ° C. Inside, there will also be hand-warmers, and the nacelle will be covered with mylar sheets.

Of course nothing will be left to chance, and at the moment we have written a test code that will allow us to see how the temperature, humidity, and battery voltage inside the vessel varies over time when positioned in a room at -20 ° C.

The test will take up to 5 hours and all data will be stored on the special micro SD card so that it can be analyzed later.

In order to read the battery voltage supplying our arduino, we must connect the + and - power supply cables with two 47 Kohm resistors connected in series. Between one resistance and the other (in the middle of the two resistors), we will weld the signal wire, which will then be connected to arduino on pin A0 (as indicated in the comment at the beginning of the code).

This is the code we used to test the nacelle:

/* Programma per testare l'isolamento termico della navicella dell'aerostato

- Il cavo di segnale MOSI, va collegato al pin 51 di arduino.
- Il cavo di segnale MOSO, va collegato al pin 50 di arduino.
- SCK va collegato al pin 52.
- CS va collegato al pin 53.
- VCC  va collegato al 5V.
- GND va collegato al GND di arduino.
- data temp int = pin 7
*/

#include <OneWire.h>   /*  sensore temperatura interna  */
#include <DHT.h>     //#include <dht11.h>
#include <SPI.h>
#include <SD.h>

#define DHTTYPE DHT11  // definiamo il modello del nostro sensore

// Assegnazione pin
int pinTempExt   = 2;   // pin usato per temperatura esterna
int pinTempInt   = 7;   // pin usato per temperatura interna

unsigned long tempo ;

/* per tensione batteria */
int PinBatt = A0;
int ValPinBatt;
float Vpin_perc;
int   Vbatt;
float calc_res;
float R1 = 10000; //modificare questi valori con i valori realmente utilizzati.
float R2 = 10000;
/* fine per tensione batteria */

//OneWire  ds(pinTempExt);
DHT      dht(pinTempInt, DHTTYPE);
File     myFile;

void   sensTempI_umid(float *temp, float *umid);
float  getTemp();

void setup() {
Serial.begin(9600);
delay( 3000 );
Serial.println("Inizio");
dht.begin();
if (!SD.begin(53) )
Serial.println("Errore su SD");

pinMode (PinBatt, INPUT);
calc_res = (R1 + R2) / R2;

}

void loop()
{
char  buff[80];
// float temperatura = getTemp();  // temp esterna
int tpi = 0;     // temperatura int (gradi celsius)
int umd = 0;     // umidita'

tempo = millis( );
sensTempI_umid(&tpi, &umd);
Serial.print("Letto ");
Serial.print(tpi);
Serial.print(" ");
Serial.print(umd);

/* batteria */
ValPinBatt = analogRead(PinBatt);
Vpin_perc = map (ValPinBatt, 0, 1023, 0, 500);  //legger� 1023 quando ho 5 volt sul pin, quindi scalo 0-1023 in 0-500.
Vbatt = (int) (Vpin_perc * calc_res);
Serial.print(" ");
Serial.println(Vbatt);
/* fine batteria */

myFile = SD.open("TU.txt", FILE_WRITE);
if (myFile)
{
sprintf(buff, "Temp=%d  Umid=%d tens_batt=%d  tempo_trascorso=%lu", tpi, umd, Vbatt, tempo/60000);
Serial.println(buff);
myFile.println(buff);

myFile.close();
}
else
Serial.println("File non aperto");

/* Serial.print("Temperatura = ");
Serial.println(temperatura);       */

//  Serial.print("Temperatura: ");
//  Serial.print(t);
//  Serial.print(" *C  ---  ");
//  Serial.print("Umidita': ");
//  Serial.print(h);
//  Serial.println(" %\n");

delay(300000);//delay(300000);   // aspetta 5 min
}

void  sensTempI_umid(int *temp, int *umid)
{
float tp = dht.readTemperature(); // leggiamo il valore della temperature (in gradi celsius)
float hu = dht.readHumidity();      // leggiamo il valore per l'umidita'

// Controlliamo se le letture sono avvenute correttamente, altrimenti generiamo un messaggio d'errore.
if (isnan(hu) || isnan(tp))
{
Serial.println("Errore. Lettura dei dati non eseguita.");
*temp = 0;
*umid = 0;
}
else
{
*temp = (int) tp;
*umid = (int) hu;
}
}

This program writes on a micro SD card a text file (.txt) called TU. The file is compiled every 5 minutes with temperature, humidity, battery voltage, and time spent in minutes. Here's an example:

Temp=16  Umid=40 tens_batt=818  tempo_trascorso=0
Temp=16  Umid=39 tens_batt=780  tempo_trascorso=5

Nacelle Version 1

This photo is the starting point for the nacelle. It is simply a polystyrene box, and it was photographed together with a battery to give an idea of the size. For curiosity, we only carried out the previous test with the box, but as expected, the results were poor. We are improving the thermal insulation of the ship, and here you can follow the development.

Nacelle Under Development

As you can see in the picture beside, the nacelle has undergone modifications and we are currently working on it.

What we will do now is to wait for the used glue to dry completely, and then we will give it the final shape by working it with the paper-glazed. At the end of this will be coated in mylar

The ship's isolation is complete, and we have tested it again (without milar).

We got a 4-hour life on board electronics. Excellent result, considering also the fact that at high altitude the air will be rarefied and therefore the thermal dispersion will be lower.

Now that the test has given excellent results with the final version of the ship, we just have to complete the software programming of the onboard electronics, which is why when this step is completed, we will have to proceed with very little modifications to the nacelle for pass the cables of external probes and solar panels from the outside to inside, then finally we will proceed with the milar.


The Camera


For this ambitious project, it has been chosen as a camera a DBPOWER EX5000, capable of 1080p video.

Given the high energy consumption of the camera, we have decided to modify it, so that the batteries will be placed inside the nacelle, where the temperature is higher. In this way we will have enough charge to film about 3-4 hours. This time will be enough to film up to the maximum altitude and part of the descent.

The camera will be positioned inside a special compartment made of expanded polystyrene, so that it is properly locked and repaired at very low temperatures.

The choice of this particular positioning is due to the fact, that in this way will also be repaired in case of violent landing.

In this photo you can see the changes made to the camera, which consists in connecting the internal contacts of the wires to which the batteries will then be connected. They will be placed inside the nacelle, next to the batteries that will feed the sensors.

Instead of the original 900 mA, the new batteries will have 2400 mA which will guarantee a much higher autonomy.