Tests of shielding effectiveness of Kevlar and Nextel onboard the International Space Station and the Foton-M3 capsule.

Radiation assessment and protection in space is the first step in planning future missions to the Moon and Mars, where mission and number of space travelers will increase and the protection of the geomagnetic shielding against the cosmic radiation will be absent. In this framework, the shielding effectiveness of two flexible materials, Kevlar and Nextel, were tested, which are largely used in the construction of spacecrafts. Accelerator-based tests clearly demonstrated that Kevlar is an excellent shield for heavy ions, close to polyethylene, whereas Nextel shows poor shielding characteristics. Measurements on flight performed onboard of the International Space Station and of the Foton-M3 capsule have been carried out with special attention to the neutron component; shielded and unshielded detectors (thermoluminescence dosemeters, bubble detectors) were exposed to a real radiation environment to test the shielding properties of the materials under study. The results indicate no significant effects of shielding, suggesting that thin shields in low-Earth Orbit have little effect on absorbed dose.

[Accounting the effect of spatial orientation of the International space station on dose rate during traverse of the South-Atlantic anomaly].

A method was devised to calculate dose rates aboard the International space station (ISS) with account for radiation field anisotropy in the region of South-Atlantic anomaly. The method enables incorporation in an explicit form the spectral-angular distribution of falling radiation in combination with ISS shielding mass distribution. It includes also a procedure of reducing these characteristics to the united coordinates with reference to ISS orientation. The dose rate ratio on the Service module opposite sides was shown to depend essentially on ISS spatial orientation.

[Problems of radiation safety of a Martian expedition crew]. / Problemy radiatsionnoi bezopasnosti ékipazha marsianskoi ékspeditsii.

Analysis of the radiation conditions during a piloted expedition to Mars made it evident that the radiation safety system will be one of the most critical components of life support aboard the future Martian vehicle. The concept and main functions of the system have been considered. The authors give their vision of the radiation monitoring system based on the present-day radiation safety postulates, comparison and contrasting methods and equipment applied for the purpose in current orbital and projected interplanetary flights.

TEPC measurements obtained on the Mir space station.

Measurements of the radiation environment inside the Mir space station were performed with a tissue equivalent proportional counter (TEPC) during the Antares mission in 1992, and over a long period following it. Interesting results concerning radiation measurements show (a) the South Atlantic Anomaly crossing, (b) the increase of radiation near the poles, and (c) the effects of solar particle events (the most important one occurring in early November 1992). This data also provides information about the dose and the quality factor of the radiation to which the cosmonauts were exposed during different missions. These data are compared with measurements obtained using a solid state detector.

[The model of radiation shielding of the service module of the International space station]. / Model' radiatsionnoi zashchishchennosti sluzhebnogo modulia Mezhdunarodnoi kosmicheskoi stantsii.

Compared and contrasted were models of radiation shielding of habitable compartments of the basal Mir module that had been used to calculate crew absorbed doses from space radiation. Developed was a model of the ISS Service module radiation shielding. It was stated that there is a good agreement between experimental shielding function and the one calculated from this model.

[Dynamics of radiation environment of space station "Mir" by the "DOZA-A1" readings]. / Dinamika radiatsionnykh uslovii na orbital'nom komplekse "Mir" po dannym pribora "DOZA-A1".

One of the serious disadvantages of the U.S. (AP-8 and AE-8) and Russian trapped radiation models is the lack of data concerning the dynamics of trapped particles fluences within a time interval shorter than the solar cycle. The available models are capable to predict the energy spectra of trapped particles only for periods in the vicinity of the solar minimum or maximum. The current models are also lacking data about the angular distribution of trapped particles. Meanwhile, these facts are important in conjunction with the problems of radiation safety of space crews. DOZA-A1 incorporating 7 semiconductor detector with a dose sensitivity of 2.4. 10(-4) muGy/pulse and a temporal resolution of 15 seconds, and a reading and charging unit were delivered to MIR in September, 1995; the experiment began in January, 1996. Measurements were made in three locations of the basal module. The articles deals with the analysis and comparison of experimental data with results of other dosimetric determinations and predictions of the trapped radiation models.

[Refinement of technique for cosmonaut's body radiation loading estimation using of orbital station dosimetric monitoring system]. / Sovershenstvovanie metodiki otsenki radiatsionnoi nagruzki na organizm kosmonavta s ispol'zovaniem sistemy dozimetricheskogo kontrolia orbital'noi stantsii.

Proposed is a technique for estimation of radiation loading of cosmonauts' body from the data of the space station radiation monitoring system by bringing the objective to a linear mathematical model. Resulted matrix ratios allow to work out the challenge; test calculations illustrating efficiency of the proposed technique are included.

Analysis of the pre-flight and post-flight calibration procedures performed on the Liulin space radiation dosimeter.

Liulin, a dosimetry-radiometry system, was developed to satisfy the requirements for active flux and dose rate measurements for the flight of the second Bulgarian cosmonaut in 1988. The system consists of a compact battery-operated silicon solid state detector unit and a read/write microcomputer and telemetry unit. We describe the pre-flight calibrations with charged particles, using radioactive sources and accelerated 170 MeV/nucleon proton and alpha particles at the Dubna, Russia cyclotron. We discuss comparisons with data obtained on Mir with the French-built tissue equivalent LET spectrometer NAUSICAA. Lastly, we describe post-flight calibrations performed with 1 GeV/nucleon 56Fe ions at the Brookhaven National Laboratory AGS accelerator, where the instrument was mounted in tandem with several thin position-sensitive silicon detectors behind a stopping target. The silicon detectors provided an energy spectrum for the surviving charged nuclear fragments for which the flux and absorbed dose were recorded by Liulin.

[An approach to formalized description of the spacecraft radiation safety task]. / Podkhod k formalizovannomu opisaniiu obespecheniia radiatsionnoi bezopasnosti ékipazha kosmicheskogo apparata.

Relationships correlating the damage expected from radiation exposure in space mission with radiobiological reactions of the body, parameters of radiation environment along the trajectory, and shielding properties of spacecraft structures were established with the use of mathematical tools of the set theory and the theory of chances. To this end, appropriate mathematical formulas were introduced which aided formalization of the space crew radiation safety task in the form of two inequalities.

The dose rate observed on 19-21 October 1989 and its modulation by geophysical effects.

The Liulin dosimeter-radiometer on the MIR space station detected the 19 October 1989 high energy solar proton event. These results show that the main particle increase contains protons with energies up to about 9 GeV. After the main particle onset the Liulin dosimeter observed a typical geomagnetic cutoff modulation of the dose rate from the solar particles as the MIR space station traversed magnetic latitudes. When the interplanetary shock and associated solar plasma enveloped the earth on 20 October between 14 and 17 UT the radiation exposure increased significantly due to the lowering of the geomagnetic cutoff. The analysis of this event shows how various geophysical phenomena can significantly modulate the dose rate encountered by earth-orbiting spacecraft.

"Mir" radiation dosimetry results during the solar proton events in September-October 1989.

Using data from dosimetry-radiometry system "Liulin" on board of "Mir"-space station the particle flux and doserate during September-October, 1989 has been studied. The orbit of the station was 379 km perigee, 410 km apogee and 51.6 degrees inclination. Special attention has been paid to the flux and doserate changes inside the station after intensive solar proton events (SPE) on 29 of September, 1989. The comparison between the doses before and after the solar flares shows increase of the calculated mean dose per day by factor of 10 to 200. During the SPE on the 29 of September the additional dose was 310 mrad. The results of the experiment are compared with the data for the solar proton fluxes obtained on the GOES-7 satellite.