The UerSions of Space Transportation Complexes in the System of Conceptual Projecting

1.I.Kurkin and D.R.Sidorov

Engines and Pouer Plants Dep.. Hoscou Ruiation Institute. 4. Uolokolamskoe Shosse Hoscow. 125871.Russia FM (095) 158-2!+??

AlAA Space Programs and Technologies Conference

and Exhibit SeDtember 21 -23, 1993 / Huntsville, AL

For permission to copy or repubilsh, contact the American Institute of Aeronautics and Astronautics 370 L'Enfant Promenade, S.W., Washington, D.C. 20024

AIAA-93-4133

THE V E R S I O N S O F SPAC.E TRAN~PORTUTION CONPLRXES IN THE SYSTEM OF C.ONC.EPTUAL FlUOJEC.TINi

Isor I.Kurk~n and

Dmitry A.Sidorov xu

Moscow Aviation Institute, MOSCOW, Russia

Abstrac t ___________.

This Paper describes an expert system of space transportation complexes (STC) conceptual designing- Such global tendencies as enlargement of international cooperation, orientation at ecological s tandards and commercialization of space activity are taken into account-

computer images integrity defining S T C infrastructure elements and methods of their interconnection. Design researrh 1 5

carried out according to scenarioes nf space exploration- On the basis of aerospace vehicles we have developed and analysed perspective versions of STC. Problems of economical concordance of international cooperation on implementins STC are outlined.

STC versions are considered to be

Introduction

Space exploration problems are demanding the search of engineering and technological solutions which will allow to solve Proposed tasks more effectively.There is a tendency to develope hybrid (combined) systems enlawins the capabilities of space vehicles and orbital complexes-In this connection we analyse some additional capabilities of space vehicles, propulsion systems and Power plants.

Copyright ( c ) 1993 by the American Institute of Aeronautics and Astronautics,Inc.All rights reserved.

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We study along scenarioes versions of aerospace vehicles usage for various missions and perform computer modification of well-known schemes of engines and energy blocks.

International cooperation in the imi=)ementation of STC-programmes SuPPoses to look for the ways of mutually benefit integration of financial resources.Taking into account high cost of STC it would be reasonable to consider macroeconomical indexes of a1 1 states-participants of the cooperation. One of the specific cost estimation methods of STC conceptual projects might be simulation, allowing in the conditions of uncertainty guantatively to determine STC cost characteristics.

A graphical image of a task for a computer dialogue is being developed. Such Computer image example is shown on Figure 1- In the centre of this figure is a conditional vector interpretation of the choice of power plant and propulsion system acceptable versions (point 1 ) . STC capabilities are considered as orientational indexes- Criteria indexes are as follows: payload specific mass //” /, transportation specific cost /C/, transportation time /c /. Limitations of the cargo compartment size, transportation specific cost,radiation doses are taken

Doctor,professor of MA1 xu Scientist of MA1

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into account- Version choice of Power Plant,PrOPulsion system and STC. as a whole depends on the task (point 2 ) and a scheme of its implementation.

transportation activities: - atmospheric flight scheme (point 7 ) ;

1.5 -amphibous plane as aerospace vehicle booster ; 1.6 -thermoplane a5 moving launch complex: 2.0 -perspective reusahle carriers.

We consider the followins schemes of 'd

the launchins site may be either on the Earth's surface OF in the air (Point 4) : - near-Earth operations scheme.when

2- Spheres of International Cooperation -__---------___---__--------.----------

tranSPoPtation vehicle is supported an the planned orbit (point 5 ) ; - deep space flight scheme of STC assembled on a near-Earth's orbit (point 6 ) .

design research of STC by the expert system. It includes information about known ~~03ect5 and existing vehicles a5 standards for comParison.Designations on Figure 2: 1 - 1 - one-stage aerospace vehicle; 1-2- aerospace vehicle of " MriarHotol"

1-3- two-stage version of aerospace vehi c1 e ; 1.4- screen-Plane as aerospace vehicle

The experience gained in the process of developins and exploitation of space enyineerins allows to carry out project researches of large space objects and their constraction in the neavest future. Such objects are: orbital stations and production modules,hish power energetics, space settlements, interplanetory space ships9space telescopes, etc. Space complexes are worth formins on orbits used by different statesrand in this connection beins main points for international cooPeration.These complexes are formed and function on the basis of power modules, delivered by carviers and ae-ospace vehicles.

Figure 2 presents the contents of the

type;

0 \ specific Power plant mass.

overall Power plant or engine efficiency

Fisure 1- The conditional interpretation of the choice-method-

Figure 2. The content of the expert

system.

2

MOL! I, x

A

Interorbital transportation vehicles ( ITV) with propu15ion systems of various capacity levels are being analysed for exploration of the geostationary orbit. On the compater

'd display screen we can see an imaye(Fig.6) in which payload mass is coordinated with flight time and an engine specific thrvst required.

@ ir,F,enr,. "?!,lL i o n b

y 9.; Homo

I ciccLr ,c L i t l Y I i 0, Y/ rlerLric F o r k d PWPr i'lb8L

u.3 "a,. L r n I 206 hr /" 0. I f l O 200 kq 1 9 " b " , 1 . rrnn L.

Figure 7 presents some versions of ITV with nuclear propulsion systems according to the projects of different states. For a transportation time of no more than 150 days the following variants of transport operations servicing are possible (Fig.6): a) flights from the base orbit UsinY only ITV with electro-rocket proPu15ion system of 300 kW; flights are connected with cargo transportation up of 10 tonnes in a single direction; b ) the usage of additional boosters (liquid ascent enyines) till altitode 5,000 km with the following application of ITV with electro-rocket propulsion system and power plant of 100 kW capacity;transported mass will

,000 hi

0.1

100 moo 100 be no more than 8 tonnes;

&us N . 5 h

Flsure 6 - The poss~bll~t~es of maintenance 1TV.

c ) after the ITV with liquid rocket engine separation at the altitude of 303000 km a maneuver for 3 tonnes payload delivery is provided by the help of ITV,having a solar power plant of 25-50 kW capacity-

4 - Servicing means of Base Orbital

Complexes _ _ _ _ _ _ _ _ _ - - -

Owing to separate launches of heavy and super- heavy boosters as "Energia". "Arian-5" ,"Saturn-5" types and some boosters of the next generations IFig.2,point 2.0) we can form a base structure of space objects,allowing to service of ITV. Aerospace vehicles can provide some additional shuttle capabilities (to and from) of Fensable space ohjects and in addition they will have an independent target P~lrPose.

5 . Aerospace Vehicles Capabilities ______._._________________________

According to Space Exploration ________.___________-------------

Scenarioes _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Various aerospace vehicles are suppos along the scenarioes: a) two-staye transportation aerospace vehicle for

;ed

Figure 7. The variants of nuclear - providing cargo streams of 5.10.15.20

tonnes per one flight "Earth-low orbit -Earth"; refueling of reusable ITV, - equipiny the vehicles with systems.

hlochs arranyiny.

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enlarging their operational capabiliLies, - ITV launching into a support orbit, - assembling and deassemblins of satellite complexes; b) single-stage meteoroyical aerosp,are transportation vehicle for flights i n t o epicentric zones of tropical hurricanes with the aim of a distant inflrrencp zipon them (required capacity levels are ahnirt 1 MW; the influence duration is abnut several dozens of minutes ) ;

c ) special single-stage aerospace vehicle in case of emergency for life-saving operations in the space, for urgent distant cargo transportation and delivering of rocket blocks in the space for withdrawal of radioactive produrts; d) two-stage multipurpose aerospase vehicle for

- additional equipment and development of base near-Earth complexes of "Mir-2" type,organization of unique productions; Figure 8 presents "Mir" station on different stases of its development I ; : ] ; designations on Fig.8: 1- space electric power plant or orh>tal plant assembly; 2- assembly of testiny module ; 3- robot; 4- orbital space vehicles for different missions; 5- power modules; 6 - docking system;7- transpor- tation vehicles of "Progress-3" and "Buran" types; 8- the second staye of space station I s Mir" development; 9- the third stage of "Mir"deve1opment;

- flights in the zone of tropical hurricanes epicentres with the aim nt

distant enfluence upon them with some reserve of power capabilities,

- the withdrawal from space dangerous large fragments in the zones of intensive transport operations owing to the powerful on-board energetics.

5-1. Aerospace Vehicle Versions

In order to provide the implementation of given tasks some potential capabilities of aerospace vehicles are analysed.For the analysis we use computer models of hybrid engines. Interior reserves of aerospace vehicles: - temperature contrasts during the flight on-board of aerospace vehicle, - hydrogen thermoaccumulating pvoperties.

._ I .. . ~ ~ ~ ~~ ~~ ~~ ~1

Figure 8. The stages of "Mir" orbital station development-

- pressure head energy potential, - possibilities of external regeneration of an engine thermal energy-

The scheme of glider arrangement proposed by NASA specialists is taken as the basis- Engines are attached to a glider in an integral module; the glider outside surface is used as propulsion plant operating surface (Figure 9). Designations on Fig.9: 1 - compression shock; 2- engines t+ust; 3- propulsion modules; 4- engine cross 5ec t I on.

F o u r versions of hybrid propulsion plants, each of which corresponding to a definite aerospace vehicle are presented in Figure 10. Designations: I- air-breathing engine contour; 1 1 - ramjet engine contour; 1 - a compressor; 2- a turbine; 3- a gas-generator; El.EZrE3rE4 - hybrid engines versions.

Various types of launching are envisaged: rocket, over-pass,from movable transportation complexes as a screen-plane.airplane,amphibious plane, thermoplane type- Proceeding from additional reserves of aerospace vehicles we develop a model computer modification of known engines for different flight condi ti ons.

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.-/ 5

Figure Y. The integral scheme of aerospace vehicle arrnnyiny.

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F% IIIRRIO QROPlhSlON IW

1 2 3

E4 HIBRIO PRDPffl.SION lllwl

Figure 10- The variants of hybrid engines schemes.

5.2. Two-stage Transportation

Aerospace Vehicle

Ease characteristics: take-off mass of 400-450 tonnes; payload mass- 5r10115,20 tonnes. For reducing engines negative influence on the environment we have chosen thrust-to-weight ratio in the range of 0 .7 -1 -0 - Chemical engines with specific thrust of 4500 N*sec/kg aFe offered for the second stage of aerospace vehicles-Hybrid engine scheme with air-breathing and ramjet engines contours is offered as a basic version for the first stage.We suppose the hybrid engine to reach the maximum speed of 6 Mach and support the demand thrust after reaching 2-3 Mach. The flight velocity of the first stage of aerospace vehicle is liaited; temperatures in engines exceeding 2600 K are excluded- -

Two p~inciples of an arrangement a r e compared: - 2 engine in a single module ( E2 in Fig.10 and Fig.11 ) r - air-breathing and ramjet engines with separate contours

~esignations on Fig.11-12: T/To - rate OE temperature growth in the engine; To- operating temperature level; 1-level of thrust supporting at the hypersonic regime or at the electrogeneratins regimes; M - Mach number; I- air-breathine engine Contour; 11- ramjet engine contour; I+II - combined zone of hybrid engine contours operation. The parameters f o r comparison: P/Po -relative thrust; Q/Qo - relative fuel consumPtion; M/Mo -relative engine mass; Po,Qo,To.Mo-standard engine indexes.

more preferable; it is more economical a 5 far as fuel consumption on the take-off is concerned; it has better thrust indexes is assumed to be the standard engine for the comparison of all hybrid schemes involved.

( E1 on Fig.10 and Fig.12).

The engine of the scheme E2 (Fig-IO) is

5-3. Meteorological Single-stage ------______-______________________ Aerospace Vehicle - - - -___________________

Base characteristics: take-off mass - 300 tonnes. payload - equipment meteorolo~ical operations. The most Preferable engine for this purpose is the hybrid engine El (Fig-lO).This engine is more economical as far as the fuel expedinture in the regime of SupPovting its thrust till 6 Mach is concerned. (Fis.lZ).However. due to -sufficient thrust capabilities of such engine, we SUPPOS~ the vehicle take-off from boosters.

when ramjet engine is workin9,the air- breathing engine is not effective and is Put in the regime of electaogenerating.The electrogenerator is on the shaft of the ensine-There aae two methods of electrogeneration: - with a ventilator switched off; air-baeathiny engine is Working in the regime of low power, - with a ventilator switched on; energy resourses of the pressure head are used.

After reaching velocities of 2-3 Mach

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6 bTrh R*, n 1

Figure 11. The characteristics of hybrid enyine E2.

5-4. Single-stare Aerospace

Vehicle for Emergency OperatiQns .---_-.-.___________.---------~--.

.---__.-.________-______________

Base characteristics: takeoff m i t i s

is 400-450 tonnes.payload mass is 7-4 tonnes- The engine of the simplest configuration ( E 3 on Fig.10) is preferable.Such engine is now under development in a number of states C 5 1 . The characteristic feature of this enyine is its gas-generator contour,intendecf for ventilator turbine drive.

range of flight velocities: from sen- space vehicle take-off velocity T.IP to the velocity of 6 Mach- It functions as a turbojet air-breathing engine till sonic velocity as a ramjet engine on hypersonic velocities. A s to the frrel consumption,it is lass economical as compared with the above schemes.but i t has minimal constrac- tion mass.The gas-generator contour of this engine is rrsed only during the regime of a turbo-jet air-breathing engine.

The engine is designed for a wide

5-5- Multipurpose Two-stage

Aerospace Vehicle ___---_-____________----------.

Base characteristics: takeoff mass 400-450 tonnesrpayload mass - 5-10 tonnes-For the implementation the ta5 i .s

and bettering electroenersetic capahili- ties of aerospace vehicles a model Computer modification of hybrid engine E3 (Fig.10) is Fealized. Fig-10 presents the scheme of modified engine Placins in the aerospace vehicle (version E4). The replacement of an unclosed gas- generator contour on a closed turbo- compressor contour is envisaged.Low

? 4 B

b r h b b r . x

Figure 12. The characteristics of hybrid engine 81-

temperature potential of hydrogen fuel 1s used.Estimation results are given in F I wwe 1 3 .Desi ynat i ons: H- flight altitude; all the rest parameters are given above.

the flight are provided by a ventilatm with a drive from a closed COntoOr- Parallel to the work of the engine at the hypersonic regime ( 3 - 6 Mach) thP yeneration of an electric energy take5 place.The effective work of a closed c ~ n t ~ u r i5 provided: up to 2 - 5 Mach

The launching and cruise regim- of

il l l l l l l i l l l I'lilll~iii,,UI( i., n, ,& T

U

Flsure 13. The characteristics of hvbride PnglnP E4

a - an air as heat transfer; h - hellium as heat transfer.

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veloczty as a result of heated hydrogen burning; at the velocity of 3-6 Mach owins to the energy pressure head. Compared operating items: air,hellium. hydrogen .

'Li The air contour is realized at the operating temperatures not less than 1800-2500 K - Hellium and hydrogen yive the contour of lower temperature. Figure 14 presents directions of bettering or worsing engine characteristics with the operating temperatures changes.Conventiona1 signs:

1 thrust growth rates; 2 thrust drop rates; 3 norking temperatures drop rates.

To. I:

-F T0.K

I200 1100, Figure 14. The directions of improvment or worsening characteristics of hybrid engine E4- a - hellim or hydroyen as heat transfers; b - an air as heat transfer.

)d The low temperature of the contour

is supported at a l l the regimes of the flight in the range of 300 K owins to the thermoaccwnrclatiny properties of hydrogen-External regeneration of the energy not used in the contour takes place; hydrogen.heated by the closed contour gives the possibility to set an additional specific thrust impulse in the engine about 300 Nrsec/kg.

The international cooperation on STC-programme can be considered as the system of economic relations: states- participators of the programme make mutual paymentsrconnected as with own services assignment as other states services application (boosters launching. communication,payload transportation to space-vehicle launching sites. etc. ). - Space activities commercialization is

supposed to use a positive profit rate f or servi ces cost calcolat ions.

Despite the tendency of growing pvivate business undertaking in space activities,the main source of space programmes financing is the state budget-Total allocations for STC- proyramme depend on economical situa- tion in the state-Russian astronautics is a good example: due to economical recession,the volume of space proyrammes state budget financing in 1991 was only 35% of the 1988 one C81.To estimate the possibility of state's participation in the international space Program it is worth-while to take into account macro- economi cal indexes.

Total budget expenditures on state Paricipation in the STC-program can be divided into the expenditures on own ohliyations implementation within international cooperation (own services) and the expenditures on payments to other states services.All expenditures are measured in a single currency. Such macroeconomical indexes a5 national income, normative ( from point of view economical growth ) payback time of state budget investments are taken into account at the expert system.

expenditures on STC-programme Participation will not exceed the normative for econmical growth value TP (years) when the condition is Provided C 9 3 :

The Payback time of state budget

TP 1 (l-Gm)*( l+r) \ ( - - - -xCl+(--- -l)cGmx( I+r)i

TS Gc , ( 1 )

where Gm - state's mass payload in a total mass payload under STC-program (mass quota). 04 Gm < 1. F - average profit rate on the budget expenditures in mutual payments of states-participators of the STC- prowram, Ts - total programme duration,years, Gc - state's budget expenditures on own obligations in total budget expenditures on obligations of all states-participators of the STC- programme (cost quota). 0 < Gc <l.

dependence of cost quota (Gc) from mass quota (Gm) when the payback time is equal to the normative value (TP).From Gc(Sm) we can see that at the fixed value of the

Figure 15 graphically depicts the

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profit rate (r) the value Gc depends inversely from the ratio of normativr payback time (Tp) to the total programme duration (Ts) .This dependence can be rised at the anticrisis regulation of national economy: the more is payback time in economy's branches the more preferable is state's participation in the international space programme on the commercial base.

0.8

0.6

0.4

0.2

Gill

0 0.2 0.4 0.6 0.8 ~ i ~ ~ ~ e 15. The dependence between C O - t

quota and mass quota. The necessity of taking into account

the economic risk factor is stipulated for a high cost and complexity of space technique-Allocations for the space programme may cause different econorniral consequences.The risk-index (Re) shnwing commensurating of possible negative and favourable economical consequences a- il

result of state's participation in the space proqramm is used:

where D - possible losses of national income due to state budget ass39115 immo- bilization for the space ProgFamme,

D - possible state incomefrom the Parti. cipation in the space PFocmamme.

state's participation in the

t

The index of economical risk of the

STC-pFogFamme is C51:

(in terms of the Keynesian theory of macroeconomics regulation)-At the expert system the acceptable level of the econamical risk is less than 1-This means that the expected income from the state's participation in the STC-proqramme should exceed the possible losses of the

national income-

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Figure 16 graphically shows the economical Fisk index depend on the mass quota of state-participator of the STC-programme.At the fixed values of r and d it is seen that the risk value depends inversely on the Cost quota.This is explained by the fact that with Gc decreasiny,the payments for services of other states connected with given state's payload insertinq into the space are increased.

0 0.2 0.4 0.6 0.0

Figure 16- Economical risk index VS. cost quota.

BY varying of Gm,Gc,r values taking into account (l)-(Z) we investigate the possibilities of economical interests concordance of states-participators of the STC-programme-The conditional example of such concordance is presented in the Table:

W

A 4.0 1.03 0.14 0.1,4 0 , 2 6 1

ti 6 . 0 1.02 0. I 4 0. 14 0.?6C

c 3 . 5 I . 0 5 0. 26 0. 26 0.643

U 5. 0 1.03 0. 14 0. 14 0 .267

E 6. 0 1.03 0. 30 0. 30 0. 667 ....~ I . 00 SVn: 1.00

While modelling the economical concordance of the international STC-proqramme we made the following simplifying assumptions:

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- the obligations (services) of separate states are not duplicated; failure to carry out own obligations leads to the failure of the whole Programme, - annual expenditures distribution on the programm is not taken into consideration. - differences of states-participators in Profit rate establishing (r) are ercluded.Therefore, the results of economical concordance of the international STC-programme should be perceived as the preliminary ones.

'-

v

CI'.

0

tonne

4.O.IO7

7.The Cost Analysis of STC-Versions 3.0 : TO7 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 0 40 80 120 tonne$

Figure 17. Aerospace vehicles specific overall expenditures VS- total payload mass.

Cost quota in the STC-proyramme supposes an integral estimation of forthcoming expenditures. The cost estimation experience of conceptual engineering projects shows that the main cause of actual and expected cost values descrepancy is connected with the lack of an accurate knowledge of engineering parameters and project implementation conditions.In this connection we have chosen the simulation as the prediction tool- The mathematics aspects of conceptual project specific cost estimation by the simulation procedure are considered in paper 132. The expected value of the specific cost is calculated by the project Parameter random varyuing in the Preliminary established range of its Possible meanings. Factors.determing RRD. production and exploitation of STC: aye considered.The expenditures are estimated in US dol lars ( 1YYo).

The results of specific overall expenditures estimation for aepospace vehicles (of single stage and two-stage schemes) made by simulation procedure are given on Figure 17. The single-stage version is presented by engines combination: air-breathing engine (ABE)+ ramjet engine (RJE) + liquid Propellant rocket engine (LPRE); the two-Stage version is presented by engines combination: ABEIRJE (first stage) and LPRE (second stage). In all the versions hydrogen fuel is employed.The overall specific expenditures (Cr) were estimated per a tonne of aerospace vehicle take-off mass- M-value on the graphics C r ( M ) means the total payload mass (tonnes) delivered to the orbit of 300 km altitude during to the programme duration.

The range Qf take-off mass random varying is 400-450 tonnes for both versions. As probabilities law distribution it was accepted Gauss-distribution. Maximal evror of Cr-estimates is 23% of calculated value for 95% level of confidence probability- As the graphics Cr(M) showes.beginning with the total payload mass appvoximately 60-70 tonnes the two-stage version of aerospace vehicle may have economical advantages. This conclusion is assotiated with the differences in the payload mass and design chaaacteristics of the aerospace vehicles versions.

Our preliminary investigations of two-stage aerospace vehicles using hydpogen fuel with the 400-450 tonnes of take-off mass and propulsion system as ABE + RJE (first stage) and LPRE (second stage) have shorn that the specific overall expenditures for payload transportation to the orbit of 300 km height will be no more B 700 Per k~ in 1990 prices if M ~ 2 1 , S O O tonnes- This means that the problem of substantial specific cost reducing of payload tvansportation to the space can be solved with aerospace vehicles in the process of large space complexes creation and exploitation-The results of the cost analysis were obtained accounting the current technological level.

payload tvansportation for any given state with payments for services of other states w a s investigated. With the above assumptions concerning the international cooperation it was stated that the specific cost of the payload

In addition.the specific cost of

transportation for a separate state w z l l not be le55 of the ratio of total expenditures on obligations to total payload mass-In other words,the prchlem of reducing the specific cost of a separate staters payload can't bp solved at the expense of other state'=. if a l l the state~-participators of STC-programme follow the principle of mutua I I y benef i t economi ca I re1 at ions.

Conclusions

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The application of the expert system for STC design analysis has lead us t o the followinY conclusions: 1. Hydpogen as a fuel provides somp add i ti onal f unc t i anal po5si bi 1 i ti e5 n l

aerospace vehicles and STC as a whvlP. 2. Ael\ospace vehicles Using hydrogen l r l e l will promote developing a transport infrastructure and reduce to a marked degree the specific cost of the payload transportation in the process of creatlon and exploitation of large orbital complexes. 3 . Economically acceptable variants of STC-programme concordance on the international basis are possible.

Acknowledgement _ _ - - _ _ _ _ _ _ _ _ _ _ _

The authors wish to thank Professor of MA1 E.U.Krasilnikov for PFDvidinY information about methods of active influence on tropical hurricanes-

References _-____-___

1. Kurkin I-I.,Sidorov D.A. et a].; Development of Infrastructure and Simulation of the Energy Series Assemblies for Solar Space Electric Power Station.-In the Boak: Solar Power Satellites: the Emerging Energy Option, E l l i s Horwood Publ-, N-Y.91953- 2.Koroteev A.S. et al.;Solar Energetics and Perspective Development of Space Vehicles.Academia of Sciences Session (USSR),Tashkent.Oct.,l541. C:.Kurkin I.I.,Sidorov D.A.;Prospects "4 Aerospace System Applications in Space Mission5.43 rd Congress of IAF, Washington. Aug.-Sept. 1992. 4.Furniss T. ;S&Y~P Aerospace Plane Gains Momentum; Flight Int.,No 4177,1589- 5-Tanatsugu N. et al.;DeveIopment Study on A i r Turbo-Ramjet for Future Space Plane.IAF Prepr-.311,1985. 6.tioelle D-,Kuczera H.; An Advanced Launcher System for Europe- 38 th Congress of IAF, Briyhton,Oct.l587. 7.Xoelle D.E.;S&~;nser Advanced Space Transportation System - Progress

8.Russian Space Today;Space,8,Nol,lS52. 5.Sidorov D.A.; Macroeconomics Analysis of International Space Prosrammes- -In Proc-of MAI,Moscow,1990.

W

Report 1990. a i m P~P.,NO 52oo,i5w.

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