A CONCEPT OF THE PURPOSEFUL RESEARCH OF THE DYNAMICS OF MAN-MADE CONDITIONS ON GEOSTATIONARY ORBITS (GEO) DURING THE SPACECRAFT DEVELOPMENTA.F. Klishin, G.D. Gotovtsev
Lavochkin Association, Russia
There exists the environmental problem caused by the cosmic space clogging up by the working spacecraft (S/C), the thrown-away upper stages (U/S), and their fragments generated by the S/C and U/S destruction, because of explosions or as a result of collisions among themselves. This problem is an actual one and is concerned with the endangering influence on the spacecraft functioning, because of probable negative consequences of the space debris (the man-made formations).
Features of the man-made formations and the condition status in the geostationary orbit (GEO) region represent the self-dependent, complex and complicated multilateral problem for the following reasons:
The last reason testifies that the natural «process of crushing», i.e. the independent fast increase of man-made objects due to the formation of new small man-made objects, has begun and exists. Now this process is an uncontrollable one and also represents the ever- growing main threat for the existence of the new spacecraft, launched with various purposes into this region. While the amount of large man-made objects is measured in hundreds, the small objects are counted by thousands and tens of thousands.
The international community is aiming at development of comprehensive and effective standards and regulations for the rate reduction of the GEO choking-up by the man-made formations, but those did not yield the desirable results yet. It seems that the boundary, when it was still possible to specify and develop the measures for efficient control of this process by technical means and with little material inputs, has imperceptibly already been crossed. It is expected that in the future the development of the serious, obligatory decisions for execution of expensive actions is necessary to overcome the consequences of the spontaneous developing of the GEO region and to decrease the SMO formation rate. Currently, in view of the circumstances mentioned, it is necessary to develop and improve methods to control the man-made conditions in the GEO, including the onboard means for surveillance and registration of the meteoroids and man-made objects, and also to eliminate by all available means, whenever it is possible, the negative ecological consequences of the space activities proceeding in this space region.
It is known, that today there are ~ 1000 large catalogued space objects (approximately 85 % of them are man-made) with the sizes > 1,0 m in the GEO region. They possess a sufficiently great potential energy (e.g., the pressurized gas containers, the fuel in tanks and propulsion systems, batteries, etc.), which can be scattered about as a result of an explosion under the following adverse circumstances:
The SO explosion results in generation of splinters (including the numerous small solid particles), which as a cloud of fragments will represent a threat for the existence of both the functioning spacecraft near the explosion zone and other large man-made objects, which possess the dangerous potential destructive energy with the subsequent generation of new splinters.
After an explosion one large object can generate from ten to hundreds of other smaller objects. The process and features of such destruction are unpredictable, but they depend on several factors, among them on the design of the object and characteristics of a source of the explosion, on its energy, the attitude, etc. Therefore, various calculation techniques are developed and investigated to estimate the amount of the generated splinters, and the parameters of their scattering (the dynamics of their movement). The results of these calculations are compared to the separate data available from the natural experiments.
Among the entire variety of the problems that are posed by the existence of the man- made conditions in the GEO, the problem of the creation of a reliable spacecraft is the main one for S/C developers. The design of a spacecraft should stand all kinds of probable influences, including the influence of the meteoroid and man-made objects (MMO) in the required operation terms.
2. TRADITIONAL METHOD OF THE MAN-MADE CONDITIONS DETERMINATION
There are the three following basic trends in studies of a problem related to the presence of the man-caused conditions in the GEO region:
By the existing strong restrictions put on the weight of a spacecraft to be launched and its subsystems, the problem of construction of a reliable S/C protection against the MMO influence is a difficult and multilevel one, since it assumes the consistent optimization of the final solution on all stages of the protection design and adjustment.
Let's note that currently the traditional method of modeling the man-made conditions in the GEO region for projected S/C is realized, and then this model is accounted for when the protection of the S/C against the meteoroid and man-made objects is developed. The method is based on the use of the research results of the first two trends. Its distinctive feature is the use of the data about existing catalogued large (the diameter ≥ 1,0 m) man-made objects in the GEO in the model, as a key parameter for the realization of assumptions about the corresponding distribution of the smaller man-made objects. Such an approach is justified by the fact that it is not obviously possible yet to systematize, and furthermore to catalogue, small (the diameter ≤ 0,5 m) man-made objects, because of their great distances from ground- based surveillance facilities, and of the imperfection of measuring devices (i.e. for the lack of the necessary volume of the statistical data). Now the results of separate successful measurements of parameters of the non-catalogued small man-made objects available from some observers are collected for further carrying out statistical generalizations. The insufficient scrutiny level for the distribution features of small man-made objects in the GEO region is a basic obstacle, which does not allow to construct a reliable mathematical model for the man-made conditions in this space region.
So, when estimating the man-made conditions for a projected S/C (for the required station in the GEO), the results obtained by the traditional method, i.e. by considering the distribution of the known data about the catalogued large space objects which are representatives and sources of the man-made objects, are used as the initial ones. In this case such a “from the general to the particular” approach allows to receive only the preliminary average data about the minimum level of probable man-made influences on the spacecraft (the estimate from below). The averaging does not even take into account the non-uniformity of distribution of the catalogued objects in the GEO longitude. This can only lead to the unfairly optimistic results, i.e. to the choice of a simplified device to protect the S/C against man-made objects.
3. RESEARCH OF THE DYNAMICS OF MAN-MADE CONDITIONS
To choose a reliable plan of a protection design for a spacecraft developed for long term operations in the GEO region (up to 10 years and more), it is necessary to increase the accuracy of the model for determination of the man-made conditions in this region, as compared with results obtained by the method considered above. It is proposed to solve this problem for the “Electro-L” meteorological satellite (Fig. 1) created by the Lavochkin Association by carrying out special regular researches of the man-made conditions (the stream density) in the vicinity of the required longitude slot of this satellite (76° East). The satellite will be in unfavorable conditions, i.e. not far from the Eastern stable libration point (75° East) with the maximal streams of working objects on this orbit, the large (catalogued) and the small (not catalogued) ones. The long research of the man-made conditions in the limited GEO region, but using the various surveillance means should allow to receive the most complete data about the features and the dynamics of man-made conditions in the concrete limited GEO region in a rather short time. It is planned to use the generalized results of this surveillance to specify the meteoroid and man-made condition model for the “Electro-L” satellite at a stage of the protection means improvement.
It is considered, that such a concept – the target research of the dynamics of man-made conditions in the required GEO region (for the concrete spacecraft) – will allow to adjust the technique and technology of the surveillance, to improve the surveillance facilities, and to intercompare in the future the data obtained by various researchers to increase the reliability and certainty of the final results.
The prospective approach should serve as more effective utilization of surveillance facilities for the decision with respect to the deadlines of an individual applied problem - to specify the real man-made conditions in the required GEO region. The application of the concept to similar problems but in other GEO regions, will serve to perfect its methodology, and the generalization of new similar results will help to specify some ideas, accepted now about features of the man-made conditions in the GEO region.
Fig. 1. An artistic view of the “Electro-L” satellite.
Ðàçìåùåí 10 äåêàáðÿ 2006.