How the space industry works and why the new SpaceX project is never a sensation

Published on November 18, 2016

How the space industry works and why the new SpaceX project is never a sensation

Despite all the workload, I just could not help but respond to this news. Why? - This is madness. But let's get everything in order.

What does the space industry consist of:

  1. This is the development of the satellites themselves.
  2. This is a ground complex
  3. This launches - which combines the first two items

Satellite


So let's start with the satellite. The planned satellite has a mass of 386 kg. those. It belongs to the class of small devices. What does it mean? - A lot of things.

What problems will arise from an engineer, he wanted to make a satellite?

1. Power balance.
2. Radiation resistance.

Radiation


And before I thought about it, when I saw the altitude range of 1100-1300 km, this is exactly radiation resistance.

Radiation belts

Before you honestly taken from Viikpedia illustrations of the radiation belt of the Earth (or Van Allen's belt). It clearly shows that its inner part starts from 1000 km.

And what's so scary about that? The fact is that in these zones a lot of high-energy particles accumulate. And in these orbits, the apparatus is experiencing maximum radiation exposure. Yes, such that nobody launches into that range of heights. And on satellites that still intersect these heights (Hubble, for example) turn off all the equipment while they pass this belt.

What other problems does radiation have? - This is an accelerated degradation of solar cells and chemical batteries.

And now let's compare this with microsatellites operating in 500 km orbits, where the radiation level is much lower. Their typical life is 5-7 years. Those. To achieve the stated lifetime, engineers need to actively deal with radiation. And our choice is small:

  1. Put absorbing screens.
  2. Duplication of all electronics
  3. 10x power reserve for both solar panels and chemical battery.

In any case, this carries with it an increase in mass and 400 kg will not be there even once.

Power balance


Just above, I talked about solar batteries and chemical batteries - this is a problem of energy input. Let's talk a little bit.

The satellite is in low orbit. An antenna cannot be pointed at it, which means that the radiation pattern is at least a hemisphere. On existing satellites, the bandwidth of such antennas is 10 kbps . Why? - Energetically, the transmitter does not provide a signal to noise ratio at distances of 500 km for faster transmission. Those. To ensure the speed of at least 1 Mbit / s, you need to increase the transmitter power by ~ 100 times.

But there is a second component in the energy balance - heat dissipation. There is no air in space and convection does not work. All dumping is due to radiation. Usually they do it this way: all the heat released is “dumped” onto one huge radiator, which is placed so that it is not exposed to the sun.

And here begins the most interesting for me.

Orbit


Let me first clarify. The motion of the satellite obeys the laws of Kepler: the trajectory is described by an ellipse, in one of the focuses is the center of mass of the Earth. Therefore, in celestial mechanics, the motion of a satellite is described as follows:

Kepler elements

This ellipse would maintain its position in the ideal case. But in reality it changes, its orbit evolves. The pace of this evolution varies with inclination and eccentricity (a measure of deviation from the circle).

The third point: if the satellites are scattered in one orbit, but at different points of it, then the satellites will each evolve in their own way (the reason is gravitational field of the Earth). As a result, the mutual distance between them will constantly change. This limits the maximum number within a single orbit.

All together this means that for each group of satellites the direction to the Sun and its range of changes is different. This means that you have to recalculate the satellite layout.

Those. reduce costs, thanks to the conveyor production will not work. But in fact, everything is much worse. Due to the re-arrangement, the conditions in which the devices will operate will constantly change. What's so bad why I will tell in the next section.

Ground complex


But before answering the question posed at the end of the previous section, I again have to give some preliminary ones.

Suppose we solved all the problems with the satellite. But they need to somehow manage. So, under the ground complex in the space industry, I understand that part of the infrastructure that is responsible for managing the satellite.

What does it mean to manage in practice? - It means to process the telemetry data array from numerous sensors on board. To estimate the scale of the disaster: 3 spacecraft into a lightweight generate 100 GB of telemetry in less than a month.

And after processing, correctly transfer the device to the desired state.

Now multiply by 4000+ devices with a zoo of layouts and sensors, and with an individual list of problems.

It is clear that even with all the automation possible, the PCO of the entire system will look like the data center of a Yandex thread. With all that it implies.

But the key word "possible automation": There is no such system for at least 50 satellites. And it is planned to deploy the system starting from 800.

So, not considering the third point - the launch (I still hope to write about it separately), we can already say that the declared satellite parameters will not be achieved, and the changes in the ground infrastructure are simply titanic, the costs of which are impossible predict now.