RÉSUMÉ
A summary of investigations results of human bone tissue changes in space flight on the orbital station (OS) Mir and international space station (ISS) using dual energy X-ray absorptiometry (DXA) is given. Results comparative analysis revealed an absence of significant differences in bone mass (BM) changes on the both OS. Theoretically expected BM loss was observed in bone trabecular structure of skeleton low part after space flight lasting 5-7 month. The BM losses are qualified in some cases as quicly developed but reversible osteopenia and generally interpreted as evidence of bone functional adaptation to the alterating mechanical loading. It was demonstrated the high individual variability BM loss amplitudes. Simultaneously was observed the individual pattern of BM loss distribution across different segments of skeleton after repetitive flights independently upon type of OS. In according with the above mentioned individual peculiarities it was impossible to establish the dependence of BM changes upon duration of space missions. Therefore we have not sufficiently data for calculation of probability to achive the critical demineralization level by the augmentation the space mission duration till 1.5-2 years. It is more less possibility of the bone quality changes prognosis, which in the aggregate with BM losses determines the bone fracture risk. It become clearly that DXA technology is unsuffitiently for this purpose. It is considered the main direction which may optimized the elaboration of the interplanetary project meaning the perfectly safe of skeleton mechanical function.