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The treadmill for the International Space Station (ISS) or the BD-2 training complex is the first Russian development of this kind. It replaced the American counterpart aboard the Russian segment of the ISS.
A key feature of the treadmill has become a unique vibration protection system, created at Samara University. It has successfully operated for 4,000 hours in space and surpassed the resource appointed by the technical assignment (3,500 hours). Taking into account the average running speed during a training session in orbit, it turns out that for 5 years Russian cosmonauts have covered the way equal to the Earth's equator on the treadmill of the ISS *.
The BD-2 complex is the result of close cooperation of Samara University, RSC “Energia” and the Institute of Medical and Biological Problems of the Russian Academy of Sciences. In designing the treadmill, the university's long-term experience in creating systems for protecting aviation equipment and rocket and space technology from dynamic and vibro-acoustic loads was used.
The team of Samara University was to create a vibration protection system capable of amortizing the enormous dynamic loads arising during the cosmonaut’s running on the treadmill – about 200-250 kg. They can cause dangerous low-frequency oscillations of the ISS structures that can destroy them.
Engineers and scientists of the university solved this problem using their own design – the unique damping material MR (metal rubber) **. In addition, a non-standard design solution was used. Instead of rigidly attaching the treadmill and trying to ensure its stable position with the help of electromechanical devices, they allowed it to float at zero gravity, connecting the complex with the ISS only with weak mechanical connections — four low-frequency (0.2 Hz) vibration isolators from the MR. As a result, the collision of the treadmill and the station structures does not occur, and the transmitted load drops by 80 times, making up only 3 kg.
Taking into account the impeccable technical condition of the systems of the BD-2 training complex, its resource was increased and a decision was made to continue operation onboard the ISS.
Commentaries
Oleg Artemyev, a cosmonaut, the Hero of the Russian Federation, a participant of two space missions to the ISS, spent more than 365 days in space
“Classes on various simulators, on a treadmill are obligatory when working on the ISS. Whereas the norms and loads for cosmonauts are calculated by physicians on the Earth, so there is no initiative – we are running in accordance with a program prepared in advance. First, a warm-up is done in the active mode, then I choose one of four programs (cyclograms), and I run, making active-passive intervals, so that there is no heavy load on my knees. Being on the ISS, which flies at an approximate speed of 8 kilometers per second, I understand that in 40 minutes I “run” a distance equal to half of the globe – and this is fascinating”.
Danila Davydov, the Deputy Chief Designer of the Sector Research Laboratory (ONIL-1) of Samara University
“The treadmill design provides it with all six degrees of freedom, which means that within the certain limits it can move along three linear axes – forward / backward, right / left, up / down, and can also make angular movements: roll, pitch and yaw. The treadmill hangs in zero gravity, and our system holds it slightly. During cosmonaut training, it fluctuates slightly, but is actually separated from the station.
***
All rocket and space machinery passes ground tests, the final stage is reliability tests. Their volume is simply enormous, since this characteristic is one of the key, and the durability test is a significant part of these checks. On the benches of our laboratory, we imitated the loads which our vibration isolation system would be subjected to in space. The tests confirmed the resource – 3500 hours. This means that during this time the system should work without failures, breakdowns and downtime. However, bench or ground tests and space are different things. Only the exploitation can judge it. And the fact that we have fully confirmed the assigned resource by operation, even exceeding 500 hours, it indicates a very high reliability of the system”.
Nikita Himoroda, the Chief Specialist of the Institute of Biomedical Problems of the Russian Academy of Sciences (SSC RF-IBMP RAS) – the lead developer of the domestic treadmill
"BD-2 is the first Russian training complex in history. Prior to this, in the Russian segment of the ISS, American treadmills having electromechanical vibration damping systems were used. Vibration protection of the Russian treadmill is designed in a completely different way. It is based on the principles of mechanics and due to this, in its characteristics it considerably surpasses the foreign one.
The main difference is that the vibration isolation system created at Samara University is passive (non-volatile). Its operation does not require energy, and this is invaluable for the ISS, where there is no other energy source than solar panels. Every day, all cosmonauts train on the BD-2 treadmill aboard the space station for 40-45 minutes a day. And a month before descending to the Earth, an enhanced mode of two workouts a day begins. Equally important, this vibration protection system is simple and reliable. This is proven by the facts – it has more than fulfilled the assigned resource".
For reference
* – At different stages of the training, the cosmonaut develops a speed of 7 to 14 km / hour on the treadmill.
** – Metal rubber (MR material) is a unique damping material developed and produced in the laboratories of Samara University. MR material has the beneficial properties of rubber and is able, however, to resist aggressive environments, high and low temperatures, as well as other adverse external influences. The secret lies in the special technology of weaving and pressing spiral metal threads of different diameter.
The dampers obtained in this way on the basis of the MR material significantly surpass (in particular, in terms of reliability) counterparts known in Russia and abroad. They are traditionally used in the production of domestic space and aviation equipment, as well as in land and sea transport systems.
Due to the full metal structure, products made of the MR material, calmly withstand temperatures up to 400 ° C, and also have high resource indicators, since the processes of destruction develop relatively slowly in them. One more interesting feature of the metal counterpart of rubber is that its damping properties are enhanced when the pressed helix threads are broken inside the vibration isolator. For example, a quality guarantee for vibration isolators made of the MR for locomotives is given for 25 years, and for space technology – for 15 years.
