Shield Protection for Spacecraft
Development of the Design Technology of the Lightweight Shielding Protection for the Pressurized Hulls of Spacecraft and its Theoretical, Experimental and Computational Justification
Tech Area / Field
- SAT-SAF/Space Safety/Space, Aircraft and Surface Transportation
8 Project completed
Senior Project Manager
Kulikov G G
Research Institute of Aviation Systems, Russia, Moscow
- Central Research Institute of Machine Building (TsNIIMash), Russia, Moscow reg., Korolev\nInstitute of Applied Mechanics, Russia, Moscow\nInstitute of Advanced Study, Russia, Moscow
- DaimlerChrysler Aerospace, Germany, Bremen\nLyndon B. Johnson Space Center, National Aeronautics and Space Administration, USA, TX, Houston
Project summaryThe safety of spacecrafts at a long-term space flight requires the creation of special protection from damage by meteoroids and orbital debris. As of now, this danger is the most important problem of spacecraft survivability. The known principles of designing of the protection demand the very massive shields. With an overall outer surface of a pressurized cabin more than 100 m2 the shielding mass becomes critical importance characteristic in spacecraft design. For example, the specific mass of an ISS Module shielding is equal about 10 kg/m2, its delivering cost to the orbit is more than 10.000 USD for each kilogram. Evidently even the saving 1 kg/m2 in the shielding weight leads to a considerable economy of the finance expenditure for space mission.
The goal of the Project is work out shielding technology to minimize spacecraft protection weight providing required survivability level. The realization of the Project opens up a wide field of applications for proposed design technology. In particular, the implementation of this technique is of prime interest for International Space Station (ISS) Modules design.
To achieve the above objective the two main problems should be solved.
To establish the most important hypervelocity impacts parameters that are responsible for lifetime increasing of the shielding samples;
To specify geometrical, physical and material parameters in terms of “cost-effectiveness” those are necessary to fabricate the shield samples on the basis of the hypervelocity impact specific features.
Within the context of solving these tasks the various features of the hypervelocity impact interactions will be investigated in an attempt to enhance the impact resistance. Particular emphasis will be placed on the dependence of the projectile fragmentation on specific impact energy. It manifests itself as the non-monotonic dependence of the Ballistic Limit Curve on velocity range 3 - 7 km/s (for normal impact). This effect is found by Swift, Preonas, Dueweke and Berike (1970) and has been the subject of investigation by Hans-G. Reimeders, Karl-Heinz Stecher, Michel Lambert (1993). Also variation of the fracture dispersion may play a certain role in the multi-shock conception.
The other effect that should be taken into account is a higher impact ability of the projectile at the oblique impact than at the normal impact. This is because the loading of the projectile at oblique shock may be smaller, than at direct one (at the same shock velocity). Moreover, the core of fractured material stream and the largest dispersed fragments determines the penetration effect of disrupted projectile. Therefore the protection design must be faced with the task of the fracture of a central part of a jet and largest fragments.
An analysis of the above mentioned physical problems would be done in the Project. The resulting solutions will be verified by the experimental investigations. It enable, on a basis of the new concept, to develop the shield protection samples with improved impact resistance and to reduce expenses on the protection of pressurized modules of the spacecraft at the given survivability level.
It is worthy of note that the Wipple shielding development has been done by partially using this approach.
This problem is associated with non-uniformity in spatial and size distributions of dangerous particles relative a spacecraft. It means that shielding construction must depend on the spatial positionand orientation of protected surface. Therefore it is necessary:
to determine an optimal decomposition of a pressurized module surface into separate zones with similar shielding characteristics,
to optimize of probability of no penetration (PNP) for the spacecraft by the choice of technically admitted ballistic limit curves (BLCs).
Solution of the above tasks allows to reduce the mass of shield protection owing to the accounting of the comprehensive analysis of risks that are caused by the “weakest” ballistic limit curves.
The competence of participants of the proposed Project is confirmed by the experience in designing and manufacturing of the “Zarya” Module shielding. It was the first ISS Module that is also known as FGB. Its PNP appeared to be equal 0.979 for 15 years of orbital life. The FGB surface area is about 180 m2. The average specific mass of protection system is about 7.4 kg/m2. The spacecraft hulk thickness varies in different zones from 1.44 mm to 6 mm; the average thickness is 3.2 mm. As material for shielding the aluminum alloy (Amg-6, standard density is 2800 kg/m3) was used. Previously some participants have been involved in the development of the protection systems for “Salyut” and “Mir” space stations.
The involved R&D personnel have an experience in handling of the problems that require the integrity of the fundamental investigations and practical implementations. Particularly, the participants from GosNIIAS and IPRIM of Russian Academy of Sciences have used such approach to solve of the above-mentioned tasks. The involved scientists from IAS have a skill and experience in solution of stochastic problems with restrictions and have intention to develop the algorithms for the surface module decomposition and for optimization of the PNP functional for the pressurized module. For development of the technology of the shield protection design as a whole the optimization programs are required that allow to calculate protective mass distribution. These programs will be used in combination with the programs for calculation of dangerous particle flows on the pointing surface zones (like “Bumper” program). The involved scientists from TSNIIMASH have such experience.
The advantage of this Project consists in the complex approach to the problem of development of the light-weight spacecraft protection, and in using of new principle of shield designing based on accounting of the impact interaction features for protection elements. There will be taken into consideration the cost of the used materials, technology of their treatment, and other problems that associated with the using of the materials in space. The application of this technology for shield design will allow to shorten time needed for creation of protection systems for any specific module that also leads to the saving of means. For example, FGB protection (where the part of the proposed technology was used) has been developed for 2.5 years that is twice as quick relative NASA Standards.
Proposed technological approach to the designing of the shield protection is semi-empirical. It includes the following stages:
Alternative protection schemes will be preliminary developed using physical analysis of processes of hypervelocity impacts.
Practical methods (by variation of the shield parameters) will be found, which allow to reduce the local impulse peak on a back wall.
Experimental investigations will carry out to make more precise physical models for hypervelocity impacts. The numerical values of parameters for the developed models will be found. Basic protective schemes and their modifications will be chosen.
The algorithms for decomposition of a pressurized module surface into separate zones with similar shielding constructions will be developed. The preliminary requirements to ballistic limit curves parameters for the separate zones will be found using the dangerous particles flows. The best distribution of the types of the protective schemes for these zones will be found using the optimization procedure.
The optimal spacecraft protective system for technical implementation and exploitation conditions will be found using the developed distributions. The experimental methods are standard and tested during R&D activity for the FGB protection system.
The following results will be obtained within the framework of the proposed Project.
Shield protection samples that will be less massive by 20-30% than by international standard. The reducing of the protection weight will be achieved using new information about hypervelocity impact interactions. The protection durability will be confirmed by its testing at hypervelocity impacts with aluminum spherical projectiles launched at the velocities up to 7 km/s.
Procedures for optimization of the shielding mass distribution on spacecraft surface zones.
Articles and/or reports to conferences on following items:
- protection technology for a whole spacecraft,
- physical features at hypervelocity impacts,
- results of experimental investigations.
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