Automatic landing "Burana"
Regular readers know that this event cannot pass by my attention, since I participated in the work on “Buran”, working in the Moscow experimental design bureau “Mars”. Although not at the most "advanced frontiers." There was a banquet in the hotel "Ukraine", where we celebrated this event, truly great for us. And there were plans for the next flight, also unmanned, but much longer, and there was work on these plans.
And then there was a dull timelessness, and then, in 1993, the closing of the program ...
I still haven’t written about Buran myself, although the next chapter about it is in my unfinished series about stories projects manned reusable ships. However, he wrote about the history of its creation, and about the rocket "Energy", too. And now I will not write about “Buran” as such, because it should not be a blog post, but a real article, and maybe not one. But I will try to show the area of responsibility of our department.
We did what the USSR provided, probably the only clear priority for all compared to the American shuttle. We, our department, did the algorithmic and software complex of the automatic landing of the Buran. As far as I know, the Americans have such a regime, but have never used it. Their shuttles are always planted pilots.
Now, as I understand it, the task of landing without the participation of the crew has been solved - after all, they land Drones, including large ones. But, in my opinion, passenger liners still do not land "in the machine." And then, I know for sure, well-equipped airfields could bring well-equipped liners to a height of 15 meters. Next is the crew. The task was aggravated by the fact that the aerodynamic quality of the Buran at subsonic was approximately half the quality of the then passenger aircraft - 4,5 versus 8-10. That is, the ship was "twice as close to the iron" as a normal swept passenger plane. Which is not surprising when you compare their shape.
Automatic landing of the 100-ton hulk is a very complicated thing. We did not do any “hardware”, only the software of the landing mode - from the moment of reaching (while decreasing) the height of 4 km to the stop on the landing strip. I will try very briefly to tell how this algorithm was done.
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First, the theorist writes an algorithm in a high-level language and tests his work with test examples. This algorithm, which is written by one person, is “responsible” for one kind of relatively small operation. Then the integration into the subsystem takes place, and it is dragged onto the modeling stand. In the stand “around” the working, on-board algorithm, there are models — a model of the dynamics of the apparatus, models of executive bodies, sensor systems, etc. They are also written in a high-level language. Thus, the algorithmic subsystem is checked in “mathematical flight”.
Then the subsystems come together and checked again. And then the algorithms are "translated" from a high-level language to an on-board machine (BCVM). To test them, already in the incarnation of the onboard program, there is another modeling stand, which includes an onboard computer. And around it is the same - mathematical models. Of course, they are modified compared to models in a purely mathematical stand. The model is "spinning" in a large general-purpose computer. Do not forget, these were 1980-s, personal numbers were just beginning and were very thin. It was the time of the mainframe, we had a Sparky of two EU-1061. And for the connection of the on-board machine with the model computer in the universal computer, special equipment is needed, it is also needed in the stand for different tasks.
We called this stand semi-natural, because in it, except for all mathematics, there was a real onboard computer. It was implemented on-board programs, very close to real-time mode. It was a long time to explain, but for the onboard computer it was indistinguishable from “real” real time.
Someday I will get together and write how the half-natural modeling mode happens - for this and other cases. In the meantime, I just want to explain the composition of our department - the team that did it all. It had an integrated department that dealt with the sensor and actuating systems involved in our programs. There was an algorithmic department - these actually wrote onboard algorithms and worked them out on a mathematical bench. Our department was engaged in a) translating programs into the on-board computer language, b) creating special equipment for a semi-natural stand (here I worked) and c) programs for this equipment.
Our department even had its own designers to make documentation for the manufacture of our blocks. And there was also a department that operated the mentioned EU-1061 Sparky.
The output of the department, and therefore the entire KB in the framework of the “buranny” theme, was a program on a magnetic tape (1980!), Which was carried further.
Next is the stand of the enterprise-developer of the management system. After all, it is clear that the control system of the aircraft is not only the onboard computer. This system made a much larger enterprise than us. They were the developers and "owners" of the on-board computers, they stuffed it with a variety of programs that perform the full range of ship management tasks from prelaunch to post-landing system shutdown. And to us, our landing algorithms, only a part of the computer time was allotted in that onboard computer, in parallel (more precisely, I would say, quasi-parallel) other software systems worked. After all, if we calculate the landing trajectory, this does not mean that we no longer need to stabilize the device, turn on and off all kinds of equipment, maintain thermal conditions, form telemetry, and so on, and so forth, and so on ...
However, back to working out landing mode. After working in the regular reserved computer as part of the entire set of programs, this set was carried to the stand of the enterprise-developer of the Buran spacecraft. And there was a stand, called full-size, which involved a ship. When working with programs, he waved Elevon, hummed with drives and all that jazz. And the signals came from real accelerometers and gyroscopes.
Then I saw enough of it all on the Breeze-M baffle, but for now my role was quite modest. I did not go outside of my design bureau ...
So, passed a full-size stand. Think that's all? Not.
Next was the flying lab. This is a Tu-154, whose control system is set up so that the plane reacts to the control actions developed by the onboard computer as if it were not the Tu-154, but the Buran. Of course, there is an opportunity to quickly “return” the normal mode. "Buransky" was included only at the time of the experiment.
The crown of the test was the 24 flight of a copy of the Buran, made specifically for this stage. It was called the BTS-002, had a 4 engine from the same Tu-154, and could take off from the runway itself. He sat down in the process of testing, of course, with the engines off, because “in the state” the spacecraft lands in the planning mode, there are no atmospheric engines on it.
The complexity of this work, or rather, of our software-algorithmic complex, can be illustrated with this. In one of the flights BTS-002. flew "on the program" to touch the lanes of the main landing gear. Then the pilot took control and lowered the nose rack. Then the program turned on again and led the device to a complete stop.
By the way, this is pretty understandable. While the device is in the air, it has no restrictions on the rotation around all three axes. And it rotates, as expected, around the center of mass. Here he touched the strip wheels of the main racks. What's happening? Roll rotation is now impossible at all. Rotation in pitch is no longer around the center of mass, but around an axis passing through the touch points of the wheels, and it is still free. And the rotation on the course is now in a complex way determined by the ratio of the steering moment from the rudder to the friction force of the wheels on the lane.
This is such an uneasy mode, which is so radically different from both flight and run on the “three points” lane. Because when the front wheel goes down to the lane, it’s like a joke: no one rotates anywhere ...
... I would add that problems, understandable and incomprehensible, from all stages of the tests were brought to us, analyzed, eliminated and again went all the way, from the mathematical stand to the BTS in Zhukovsky.
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Here you go. Everyone knows that the landing went flawlessly: an error in time 1 second - after a three-hour flight! - deviation from the axis of the band 1,5 m, in range - some tens of meters. Our guys, those who were in the KDP - this is an office building near the strip - they said that they had feelings - they could not express in words. Why, they knew what it was, how many things worked right there, what millions of interrelated events occurred in the right relationship, so that this landing could take place.
The outskirts of the airfield "Jubilee" at Baikonur. Now it's just an airfield, I flew from it. And it was built as the main strip for the operation of the space transport system “Energy” - “Buran”. Naturally, the only completed flight of the Buran ended here ... Photo by Galina Iodko
And I will say: “Burana” is gone, but the experience is not lost. A great team of first-class specialists, mostly young ones, grew up in this work. The charge from it was such that the team did not fall apart to its foundations in difficult years, and this made it possible to create a control system for the Briz-M upper stage right at that time. It was no longer a software system, there was already our own onboard computer, and the blocks that control all the onboard machinery - engines, cutters, adjacent systems of other developers, etc. And we did the ground-based testing and prelaunch preparation of the upper stage.
Of course, “Breeze” was made to all KB. But a very important role, above all in the creation of the software complex, was played by the people of Buran - people who built and perfected the great work of doing work with the participation of hundreds of experts from dozens of different profiles during the Buran epic. And now the KB, which has proven its viability, has a lot of work ...
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