Tomorrow we will send our server into the stratosphere. During the flight, the stratostat will distribute the Internet, shoot and transmit video and telemetry data to the ground. We wrote several times that we would tell about the technical side of our project "Space Data Center" (previously responded to the name ""). We promised - we deliver! Under the cut, a handful of pieces of iron and code.
Web server
Even in the previous βServer in the Cloudsβ project, when we went up in a full-fledged balloon with a crew of two, it was, letβs say, not rational to take a full-fledged server with a battery assembly with us. And now we are talking about a small stratospheric balloon, which will have to climb 30 km, and not 1. Therefore, we chose the same Raspberry Pi as a web server. This microcomputer will generate an HTML page and show it on a separate display.
Satellite connection
In addition to Raspberry, modems of Iridium and Globalstar satellite communications networks will fly on board. As you remember, we planned to add a modem of the domestic network "Gonets" to the company, but we did not have time to get it in advance, so we will send it on the next flight. Through satellite modems, the web server will receive your messages, which can be sent to . These messages will be passed to the Raspberry Pi, which will queue them up and display them on an HTML page.
An important point: the limit on the length of a text message in Russian is 58 characters (including spaces). If the message is longer, it will be truncated during transmission. Also, all special characters will be cut out of the text, for example, /+$%&;''""<>n and the like.
Since the Raspberry Pi has only one UART port, we will connect the satellite modems through an intermediate hub, which will collect data from the modems and send it to the Raspberry Pi.
radio modem
The web server will not only display all messages received from you on the display, but also broadcast them to Earth via the LoRa radio modem. So we want to test the idea of ββdistributing the Internet from the stratosphere (a tribute to the Google Loon project). Of course, our stratospheric balloon is not a full-fledged communication repeater, but even if its capabilities are enough for stable data transfer, without large information losses, then specialized systems will definitely cope with the distribution of the Internet from the pre-space.
Telemetry
In addition, we plan to display telemetry data on the same HTML page. Raspberry Pi will take them from a separate flight controller.
It interrogates various sensors that can be placed both inside and outside the hardware hermetic box, collects information in a heap, combs it and gives it in a convenient form to those who ask. In our case, it will ask for a Raspberry Pi. We will record pressure, altitude, GPS coordinates, vertical and horizontal speed and temperature.
Data from the flight controller is transmitted in long lines, which are then using this code:
$str = 'N:647;T:10m55s;MP.Stage:0;MP.Alt:49;MP.VSpeed:0.0;MP.AvgVSpeed:0.0;Baro.Press:1007.06;Baro.Alt:50;Baro.Temp:35.93;GPS.Coord:N56d43m23s,E37d55m68s;GPS.Home:N56d43m23s,E37d55m68s;Dst:5;GPS.HSpeed:0;GPS.Course:357;GPS.Time:11h17m40s;GPS.Date:30.07.2018;DS.Temp:[fc]=33.56;Volt:5.19,0.00,0.00,0.00,0.00,0.00,0.00,0.00';
parse_str(strtr($str, [
':' => '=',
';' => '&'
]), $result);
print_r($result);are converted into an array in a form convenient for display:
Array
(
[N] => 647
[Π’] => 10m55Π·
[MP_Stage] => 0
[MP_Alt] => 49
[MP_VSpeed) => 0.0
[MP_AvgVSpeed] => 0.0
[Baro Π rΠ΅ss] => 1007.06
[Baro_Alt] => 50
[Baro_Temp] => 35.93
[GPS_Coord] => N56d43m23s,E37d55m68s
[GPS_Home) => N56d43m23s,E37d55m68s
[Dst] => 5
[GPS_HSpeed] => 0
[GPS_Course] => 357
[GPS_Time] => 11h17m40s
[GPS_Date] => 30.07.2018
[DS_Temp] => [fΡ] ΠΠ.56
[Volt] => 5.19, 0.00,0.00,0.00,0.00,0.00,0.00,0.00
)We will also broadcast telemetry data to Earth along with your messages. To do this, we will deploy a receiving station at the launch site.
Display and camera
So that you can make sure that the server really receives your messages via satellite, and that it actually flew into the stratosphere, and is not standing in our office, we decided to display all messages with telemetry on a display that will be filmed by a GoPro. There was little time to prepare the project (but when is there a lot of it ?!), so we did not torture Aliexpress and a soldering iron, but instead took a ready-made device. More than enough for our needs. We will connect the display to the Raspberry via HDMI.
We also plan to broadcast video from GoPro via a separate radio channel, but how it will work is still unknown - perhaps low cloud cover will greatly reduce the communication range. But in any case, after we find the landed stratospheric balloon, we will post the video from the camera and you can see for yourself what messages our βpre-space data centerβ received and how high it climbed - telemetry will be displayed in the same HTML page, in addition, a piece of the horizon will be visible.
Food
All the beauty described above will be powered by an assembly of lithium batteries assembled according to the 3S4B scheme - three in series, four in parallel. The total capacity is about 14 Ah at a voltage of 12 V. According to our estimates, this should be enough, but after the final assembly, of course, we will measure the actual consumption, and if necessary, add more batteries.
Add to all this GPS beacons, by which we will search for a landed stratospheric balloon. And the "house" for the server and other devices will be a hermetic box.
It will protect delicate equipment from temperature and pressure drops. At the same time, it will reduce the radiation dose, although this does not play any role for our project, the server will fly in the stratosphere for too long, and the background there is not as high as on the ISS.
In addition to sending messages to , you can participate in the contest and guess where the probe will land. The main prize is a trip to Baikonur to launch the Soyuz-MS-13 manned spacecraft.
Source: habr.com