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M.E.G.A.L.O.S.: Multimission European geostationary Ariane launched orbital station
h c t a h ~ , o r , aatnra
Vol. II. No. 10/ll. pp. 7"25-729, 1904
~q,t-5765,,~l
Pnnted La the U.S.A.
$3.00+00
I~'lmnon I ~ - ~ Lad.
Academy Transactions
Note
M.E.G.A.L.O.S.: MULTIMISSION EUROPEAN GEOSTATIONARY ARIANE LAUNCHED ORBITAL STATIONt M. T. RAVAZZO'rn Aeritalia Space Sector, Corso Marche 41, 10146 Turin, Italy and
A. FESTA ESTEC (TSS), Zwarteweg 62, Noordwijk 2200 AG, The Netherlands (Endorsed by L. G.
NAIK)LffANO:~and J. P. MAREC§; received 16 February 1983; Complements received 19 October 1983)
Abstract--A new configuration of Telecommunication Platform, specifically conceived to meet the requirements of a set of payload packages resulting from a market survey for the next decade European demands, is presented. It is assembled on geostationaryorbit, via rendezvous and docking of modules separately launched by Ariane 4.
In-orbit growth potential and/or refurbishment derive from the rendezvous and docking capability and M.E,G.A.LO.S. can be seen as a module of an even more complex structure. Platforms for T I C Payloads't, at the moment in its phase I1, whose goal is the definition of a detailed technological plan along with the manufacturing and testing of a demonstration article representative of the outstanding thermomechanical aspects. M.E.G.A.L.O.S. ( _Multimission l~,uropean Qeostationary A_riane Launched Qrbital Station) was born to specifically meet the requirements of a range of nine TLC multimissions identified during the first phase of the contract and briefly outlined hereafter, mainly in terms of requirements on the configuration; nevertheless, its features are such to allow for both a-priori and on-orbit growth potential, making it applicable to different payloads/requirements.
I. INTRODUCTION
in the framework of the activities related to the identification of space segments able to meet the requirements of European TLC's for the next decade (1990), high efforts are devoted to the definition of a European tailoring of the concept of Large Space Platforms, in order to cover the gap existing between the Large Satellite class (whose proliferation would raise problems of frequency spectrum and orbital position crowding and would require high costs both in the procurement of the space segment--to guarantee an acceptable reliability for an extended lifetime--and in the management of the ground stations) and the Orbital Antenna Farms under study in U.S. (quite far from both the near future European needs and the technology developments achievable for the foreseen times). ESA is, at present, following a number of contracts devoted to define a candidate mission, able to meet the above mentioned requirements but implying technological developments well inside the European capabilities and making the maximum use of the European facilities. The configuration presented is under study in AERITALIA in the frame of the ESTEC "Advanced Space Technology Program" (ASTP), entitled "Large Space
tCondensed from a paper presented at the 33rd Congress of the International Astronautical Federation, Paris, France, 27 September-2 October 1982. ~Academy Member (Section 2). §Academy Corresponding Member (Section 2).
2. T H E PROPOSED TLC MULTI-MISSIONS
A Multi-Mission has been defined[l] as a modular grouping of payloads, autonomous and independent as far as the service provided is concerned; the candidate payloads, extracted from the market survey generated by ESA, give the following services: --National Intercity TF (Option C&A4) --National DTV Broadcasting mEuropean Regional Trunk Service with the addition of mlnterplatforms Link in order to add flexibility to the system. tESTEC Contract No. 4750/81/NL/AK, ESTEC Study Manager:. Alessio Festa, AEILITALIA Study Manager:. Maria Teresa Ravazzotti.
725
M. T. RAvAzzo'rn
72.6
The selected P/L's have been grouped to provide for: (I) Service Dedicated Missions - - D ' I V broad-casting for 2-6 countries - - T F for 2-3 countries --E.R.T.S. (2) Multi National Services Missions - - T F and DTV broadcasting for 2 countries. Table I defines the 9 multi-missions that were generated during the phase I of the contract and adopted as a reference to be supported ty M.E.G.A.L.O.S. The mission requirements impacting on the configuration are mainly: - - T L C package mass (Me/L) --Power required for day (Po) and night (P,~) TLC operations --Heat dissipation (Po,ss) requirements Furthermore, the following general guidelines drove the overall study: --the platform is modular and assembled in GEO --the modules are launched by ARIANE --the lifetime is 10-15 years --those technological developments that can be reasonably envisaged as achievable for the end of the 1990s must be adoped and clearly identified. 3. M . F . G . A . L O . S . : C O N F I G U R A T I O N
OUTLINE
Having as a baseline the requirements deriving from the reference missions, the configuration proposed is depicted in Fig. h it can be considered as a basic space segment meeting the above requirements but allowing for the satisfaction of even more demanding options.
and
A. FEs'rA
The basic version of M.E.G.A.L.O.S. foresees: (a) a service module, Sun pointing and provided with fold-out solar arrays (B.O.L. powers in the range 15 + 48 kW are required) (b) three payload modules interfaced with the SM via a despun T-deployable truss All the modules have been dimensioned to fit the Ariane (44) fairing. The main advantages of the chosen configuration are: (i) optimal efficiency of the radiating area (heat dissipation capability: ~ 360 W/m 2) (ii) possibility of service growth via additional SM's docking (iii) use of a single B.A.P.T.A. (iv) simplicity in the attitude reference system (v) possibility of covering the Sun pointing face with solar cells to support the waiting phases without need of panels deployment (up to ~ 2200 W available). The payload modules are designed to support the payload packages, that are presented in Table 2 along with the most critical constraints they impose on the module itself, when compared with the ARIANE fairing characteristics. The full solid antennae, when stowed in the launcher fairing, are folded along two parallel lines; when deployed, they need to be distanced both from the neighboring ones (the PM width being only 2.5 m) and from the deployed arrays. A T-deployable truss has been adopted [2], formed by telescopic shear members and folding iongerons, mounting rotary docking
Table i. Reference multimissions: scenario and inlerfac¢ requirements MISSION ID. N. I
2
SERVICE PROVIDED S . D . M . - T F FOR 2 COUNTRIES ( A d ) * ERTS S.D.M.-TF
FOR
3
b
P/L M PDb
PNb
PDISS
(Kg) a
(Kw
( K w ) (Kw)
966
6.98
6.98
5.5]6
1020
7.21
7.21
5.759
4.82
9.498
COUNTRIES(A4) 3
N.S.M.-TF(Ad)& DTV FOR 2 COUNTR
]140
12.48
4
S.D.M.-TF(C)FOR
]542
I]2.72 I
2.2
10.256
9 COUNTRIES ERTS
÷
5
S.D.M.-TF(C)FOR 3 COUNTRIES
]884
!]5.82
]5.82
]3.043
6
S . D . M . - D T V FOR 4 COUNTRIES ÷ ERTS
1206 ~
!]7.52
2.2
]3.006
7
N.S.M.-TF(C) & D T V FOR 2 COUNTR.
]716
I]8.22 ]0.62
S.D.M.-DTV
]433
2].35
2.2
15.83]
]380
]9.02
O.
]6.988
8
FOR
5
]4.238
COUNTRIES + ERTS 9
aI.L.
S.D.M.-DTV COUNTRIES
Is
alwais
bincluding
I.L.
FOR 6
included and
APM
M.E.G.A.L.O.S.
Fig.
I.
M.E.G.A.L.O.S.: Basic space segment artistic view.
ports; it works also as a functional interfacing bus between service and payload modules. 4. M A T i I E M A T I C A L
727
MODEIA~ A N D CONCEPT
PEILSPECIrIVF,S Mathematical models have been set up, based on the preliminary results of the subsystem studies, devoted to assess the concept capabilities in terms of telecommunication performances, based on the requirements of the nine reference missions. Nevertheless the concept can be adopted to satisfy even more demanding payloads, via growth of the basic configuration by successive addition of payload/ service modules, either foreseeing it before the launch and once in orbit.
The concept of modularity brings to a variety of different options, ranging from (a) a SM carrying all the supporting functions, the PM's being only in charge of the TLC package, to (b) a standard SM, providing only for power generation/control and attitude reference/control, the auxiliary propulsion along with energy storage and distribution equipment being physically carried by the PM's. Table 3 shows the relationships adopted between the TLC power dependent equipment masses and the output TLC power. In the case of option a above, the mathematical model for the SM mass can be written as
MSM ----I.l(Minv + Meca + MaDR + Me^rr + Mpcu
)
Table 2. Payload packages: main interface requirements P/L
learning factor
+ Ms^ + Mrc + Mr.: + M^cs + Ms-ra
E
A
+ MDOCK)+ Macs = 61.40 Po + 66.64 PN %ntennae ~uantlty %ntennae Imenslons
4
2
2
2
3
].3m @ 4m 0.08m~
4m
lX2.7m
1X2.7 m
10.6
2
~equtred -adlattng zrea(m 2 )
3.75
5.8
13.1
446
334
622
?otal m a s s [repeater antenna)
454
15.9
681
A - ERTS * I L = =
European European European European
The masses non-dependent on power are shown in Table 4, where the case of ion bombardment auxiliary propulsion has been considered for the RCS. The PM mass is calculated as
MpM= 1.1 (MsrR + MTC + MDOCK+ MBAYr)+ Mp/L. ) learning factor
gg)
B C D E
+ 932.62 + (199 + 293)t
National Natlonal National National
Intercity - O p t | o n A4 Interclty - Option C DTV - 2 C o u n t r l e s DTV - 3 C o u n t r i e s
where M . = 130 kg. Mrc = (26. I i 3 + 9.473 Pc) kg[ I ], MB^rr = 20 kg (mass of batteries needed for the waiting tit is the RCS mass dependent on the PM mass.
728
M. T. RAw~zztyr'n and A. Fm'rx Table 3. Power dependent equipment mass models EQUIPMENT
MASS
7 . 3 7 PD
INV BATT a
(Kg)
45.588 PN + 43 308b
BDR
7.756 PN + 7"368b
BCR
1.606 PN + 1"525b
PCU SA
11.82
(PD + Ib) 31.03 PD
aNickel Hydrogen batterles[3l. b Con.ribution due to the Services Power, assumed
to be I000 w.
phases), and Mt~:x = 112 kg (comprehensive of RV sensors).
The above mathematical models have been applied to • solid-storable-cryogenic propulsion for GTO circularization • the Ariane 4 family launchers lift-off mass capabilities[4, 5l to evaluate the mission satisfaction capacity of the concept. As an example Table 5 shows the results for storable and cryogenic propulsion with ARlANE 44L, in terms of available night power for the P/ L against the required one. Option a requires then eithcr • the launch of two SM, or • a reduction in the lifetime of the platform (10 years against the envisaged ! 5 give a gain of 2-3 kW in the available PM) or • the development of a new cryogenic stage (storable propulsion being presently retained as the baseline subsystem solution), or • a reduction in the night operations, and • the adoption of electrical auxiliary propulsion.
Table 4. Mass breakdown o f the SM items non-dependent on power (option a) ITEM
TC TTC+DH
MASS (Kg)
35 70
ACS
150
STR
250
DOCK
RCS a
200 369+568
aMRc s - 0 . 1 0 2 5 MEOL - O.1025(MSM+ MpM)EO L Ill
Option b, on the other hand, brings to different mathematical models, where: MsM = 1. I (Mpcu + Ms^ + MTC + Myrc ÷ D, + M^cs + MSTR+ MDOCK)MAX = 47 PaM,x + 846 = 1928 kg MpM ---- I. I (MsTn + Mtc + M~cK + Me^yr +
MeDR
+ MncR + MINV)+ Me/L + MRcs where M~cs is a standard quantity, evaluated on the basis of the mass available on Ariane for the heaviest payload module. Table 6 shows the platform lifetime, mission by mission, if storable propellant is used for RC$, for Ariane 44 LP and Ariane 44L. The most appealing features of such an option (to be confirmed by the subsystem studies) are • low cost in the procurement of the standard SM • standardization in the primary and secondary propulsion subsystem for the PM's • optimization of the A R I A N E (44L) lift-off mass capabilities • adoption of state of the art bipropellant thrusters for the RCS • a minor decrease in lifetime of the unserviced platform with respect to the goal of 15 years. 5. CONCLUSIONS
The Platform described, M.E.G.A.L.O.S., which has been proposed to satisfy some well defined telecommunication requirements, can be considered as a promising "brick" for more ambitious missions, both in terms of power demands and of antennae dimensions (provided compatibility with the A R I A N E fairing dimensions is verified). The technology developments required, whose plans shall be detailed as an output of the overall study, could be achieved with medium term programs, being on the other hand well aligned with the current European activities.
729
M.E.G.A.L.O.S. Table 5. Option a: TLC power available during night (single SM, Aflame~4L. 15 years lifetime) P (gw) MISSION ID. N REQUIRED
P. AVAIL. (Kw) (~TORABLE ABM)
P AVAIL. (Kw) (C~YOGEN. ABM)
6.98
>6.98
>6.98
7.2]
>7.21
>7.21
4.82
4.8
>4.82
12.72
1.5
10.78
15.82
0.94
7.4
2" SM REQ.
2.2
>2.2 5.45
10.56 2.2
>2.2
O.
>0.
table 6. Obtion b: Unserviced platform lifetime (storable ABM and RCS) MISSION ID. N
LIFETIME (Y)
LIFETIME (Y)
(ARIANE 44LP)
(ARIANE 44L)
:,15
>15
14.1
1,1.67
12.2
>15
10.87 13.96 II.5 12.82
13.04
The result could be a space segment highly flexible, able to support different mission requirements with only minor changes in the basic configuration, and making the maximum use of European know-how, technologies and facilities. APPENDIX
Nomenclature ACS Attitude Control System ABM Apogee Boost Motor APM Antenna Pointing Mechanism BA'Fr Batteries BCR Battery Charge Regulator BDR Battery Discharge Regulator BOL Beginning of Life DH Data Handling DOCK Docking DTV Direct Television d V Velocity increment EOL End of Life ERTS European Regional Trunk Service GEO Geostationary Orbit GTO Gcostationary Transfer Orbit IL lntcrplatform Link INV Inverter (or DC/DC converter) M Mass NSM (Multi) national Service Mission Pc Conductive dissipation Po Payload power required for day operation PD,ss Power to be dissipated
Ps PCU P/L PM RCS RV SA SDM SM STR TC TF TLC
Payload power required for night operation Power Control Unit Payload Payload Module Reaction Control System Rendez-Vous Solar Array(s) Service Dedicated Mission Service Module Structure Thermal Control Telephony Telecommunication REFERENCES
I. Shuttle dedicated large platforms for TLC payloads. AERITALIA, ESTEC Contract 3940/79/NL/AK. Final Report (Dec. 1981l. 2. Conceptual design study. ,gASP. Final briefing. McDonn¢l Douglas (Oct. 1981). 3. Prediction of thermal behaviour of metal hydrogen battery cells. Elcktronic Centralen. ESTEC Contract 3346/NL/77/HP(SC). Final Report. 4. Internal Review. Ariane Programme. ESA AR/94 (Nov. 1981). 5. ARIANE 4. ARIANESPACE (Oct. 1981). 6. A. W. Preukschat Cost assessment of communication satellite systems as function of satellite reliability. STM218 (ESTEC) (June 1980). 7. Continued studies of the future European TLC satellite programs. Final Report. £SA £X£C (79)3 (July 1979).
Vol. II. No. 10/ll. pp. 7"25-729, 1904
~q,t-5765,,~l
Pnnted La the U.S.A.
$3.00+00
I~'lmnon I ~ - ~ Lad.
Academy Transactions
Note
M.E.G.A.L.O.S.: MULTIMISSION EUROPEAN GEOSTATIONARY ARIANE LAUNCHED ORBITAL STATIONt M. T. RAVAZZO'rn Aeritalia Space Sector, Corso Marche 41, 10146 Turin, Italy and
A. FESTA ESTEC (TSS), Zwarteweg 62, Noordwijk 2200 AG, The Netherlands (Endorsed by L. G.
NAIK)LffANO:~and J. P. MAREC§; received 16 February 1983; Complements received 19 October 1983)
Abstract--A new configuration of Telecommunication Platform, specifically conceived to meet the requirements of a set of payload packages resulting from a market survey for the next decade European demands, is presented. It is assembled on geostationaryorbit, via rendezvous and docking of modules separately launched by Ariane 4.
In-orbit growth potential and/or refurbishment derive from the rendezvous and docking capability and M.E,G.A.LO.S. can be seen as a module of an even more complex structure. Platforms for T I C Payloads't, at the moment in its phase I1, whose goal is the definition of a detailed technological plan along with the manufacturing and testing of a demonstration article representative of the outstanding thermomechanical aspects. M.E.G.A.L.O.S. ( _Multimission l~,uropean Qeostationary A_riane Launched Qrbital Station) was born to specifically meet the requirements of a range of nine TLC multimissions identified during the first phase of the contract and briefly outlined hereafter, mainly in terms of requirements on the configuration; nevertheless, its features are such to allow for both a-priori and on-orbit growth potential, making it applicable to different payloads/requirements.
I. INTRODUCTION
in the framework of the activities related to the identification of space segments able to meet the requirements of European TLC's for the next decade (1990), high efforts are devoted to the definition of a European tailoring of the concept of Large Space Platforms, in order to cover the gap existing between the Large Satellite class (whose proliferation would raise problems of frequency spectrum and orbital position crowding and would require high costs both in the procurement of the space segment--to guarantee an acceptable reliability for an extended lifetime--and in the management of the ground stations) and the Orbital Antenna Farms under study in U.S. (quite far from both the near future European needs and the technology developments achievable for the foreseen times). ESA is, at present, following a number of contracts devoted to define a candidate mission, able to meet the above mentioned requirements but implying technological developments well inside the European capabilities and making the maximum use of the European facilities. The configuration presented is under study in AERITALIA in the frame of the ESTEC "Advanced Space Technology Program" (ASTP), entitled "Large Space
tCondensed from a paper presented at the 33rd Congress of the International Astronautical Federation, Paris, France, 27 September-2 October 1982. ~Academy Member (Section 2). §Academy Corresponding Member (Section 2).
2. T H E PROPOSED TLC MULTI-MISSIONS
A Multi-Mission has been defined[l] as a modular grouping of payloads, autonomous and independent as far as the service provided is concerned; the candidate payloads, extracted from the market survey generated by ESA, give the following services: --National Intercity TF (Option C&A4) --National DTV Broadcasting mEuropean Regional Trunk Service with the addition of mlnterplatforms Link in order to add flexibility to the system. tESTEC Contract No. 4750/81/NL/AK, ESTEC Study Manager:. Alessio Festa, AEILITALIA Study Manager:. Maria Teresa Ravazzotti.
725
M. T. RAvAzzo'rn
72.6
The selected P/L's have been grouped to provide for: (I) Service Dedicated Missions - - D ' I V broad-casting for 2-6 countries - - T F for 2-3 countries --E.R.T.S. (2) Multi National Services Missions - - T F and DTV broadcasting for 2 countries. Table I defines the 9 multi-missions that were generated during the phase I of the contract and adopted as a reference to be supported ty M.E.G.A.L.O.S. The mission requirements impacting on the configuration are mainly: - - T L C package mass (Me/L) --Power required for day (Po) and night (P,~) TLC operations --Heat dissipation (Po,ss) requirements Furthermore, the following general guidelines drove the overall study: --the platform is modular and assembled in GEO --the modules are launched by ARIANE --the lifetime is 10-15 years --those technological developments that can be reasonably envisaged as achievable for the end of the 1990s must be adoped and clearly identified. 3. M . F . G . A . L O . S . : C O N F I G U R A T I O N
OUTLINE
Having as a baseline the requirements deriving from the reference missions, the configuration proposed is depicted in Fig. h it can be considered as a basic space segment meeting the above requirements but allowing for the satisfaction of even more demanding options.
and
A. FEs'rA
The basic version of M.E.G.A.L.O.S. foresees: (a) a service module, Sun pointing and provided with fold-out solar arrays (B.O.L. powers in the range 15 + 48 kW are required) (b) three payload modules interfaced with the SM via a despun T-deployable truss All the modules have been dimensioned to fit the Ariane (44) fairing. The main advantages of the chosen configuration are: (i) optimal efficiency of the radiating area (heat dissipation capability: ~ 360 W/m 2) (ii) possibility of service growth via additional SM's docking (iii) use of a single B.A.P.T.A. (iv) simplicity in the attitude reference system (v) possibility of covering the Sun pointing face with solar cells to support the waiting phases without need of panels deployment (up to ~ 2200 W available). The payload modules are designed to support the payload packages, that are presented in Table 2 along with the most critical constraints they impose on the module itself, when compared with the ARIANE fairing characteristics. The full solid antennae, when stowed in the launcher fairing, are folded along two parallel lines; when deployed, they need to be distanced both from the neighboring ones (the PM width being only 2.5 m) and from the deployed arrays. A T-deployable truss has been adopted [2], formed by telescopic shear members and folding iongerons, mounting rotary docking
Table i. Reference multimissions: scenario and inlerfac¢ requirements MISSION ID. N. I
2
SERVICE PROVIDED S . D . M . - T F FOR 2 COUNTRIES ( A d ) * ERTS S.D.M.-TF
FOR
3
b
P/L M PDb
PNb
PDISS
(Kg) a
(Kw
( K w ) (Kw)
966
6.98
6.98
5.5]6
1020
7.21
7.21
5.759
4.82
9.498
COUNTRIES(A4) 3
N.S.M.-TF(Ad)& DTV FOR 2 COUNTR
]140
12.48
4
S.D.M.-TF(C)FOR
]542
I]2.72 I
2.2
10.256
9 COUNTRIES ERTS
÷
5
S.D.M.-TF(C)FOR 3 COUNTRIES
]884
!]5.82
]5.82
]3.043
6
S . D . M . - D T V FOR 4 COUNTRIES ÷ ERTS
1206 ~
!]7.52
2.2
]3.006
7
N.S.M.-TF(C) & D T V FOR 2 COUNTR.
]716
I]8.22 ]0.62
S.D.M.-DTV
]433
2].35
2.2
15.83]
]380
]9.02
O.
]6.988
8
FOR
5
]4.238
COUNTRIES + ERTS 9
aI.L.
S.D.M.-DTV COUNTRIES
Is
alwais
bincluding
I.L.
FOR 6
included and
APM
M.E.G.A.L.O.S.
Fig.
I.
M.E.G.A.L.O.S.: Basic space segment artistic view.
ports; it works also as a functional interfacing bus between service and payload modules. 4. M A T i I E M A T I C A L
727
MODEIA~ A N D CONCEPT
PEILSPECIrIVF,S Mathematical models have been set up, based on the preliminary results of the subsystem studies, devoted to assess the concept capabilities in terms of telecommunication performances, based on the requirements of the nine reference missions. Nevertheless the concept can be adopted to satisfy even more demanding payloads, via growth of the basic configuration by successive addition of payload/ service modules, either foreseeing it before the launch and once in orbit.
The concept of modularity brings to a variety of different options, ranging from (a) a SM carrying all the supporting functions, the PM's being only in charge of the TLC package, to (b) a standard SM, providing only for power generation/control and attitude reference/control, the auxiliary propulsion along with energy storage and distribution equipment being physically carried by the PM's. Table 3 shows the relationships adopted between the TLC power dependent equipment masses and the output TLC power. In the case of option a above, the mathematical model for the SM mass can be written as
MSM ----I.l(Minv + Meca + MaDR + Me^rr + Mpcu
)
Table 2. Payload packages: main interface requirements P/L
learning factor
+ Ms^ + Mrc + Mr.: + M^cs + Ms-ra
E
A
+ MDOCK)+ Macs = 61.40 Po + 66.64 PN %ntennae ~uantlty %ntennae Imenslons
4
2
2
2
3
].3m @ 4m 0.08m~
4m
lX2.7m
1X2.7 m
10.6
2
~equtred -adlattng zrea(m 2 )
3.75
5.8
13.1
446
334
622
?otal m a s s [repeater antenna)
454
15.9
681
A - ERTS * I L = =
European European European European
The masses non-dependent on power are shown in Table 4, where the case of ion bombardment auxiliary propulsion has been considered for the RCS. The PM mass is calculated as
MpM= 1.1 (MsrR + MTC + MDOCK+ MBAYr)+ Mp/L. ) learning factor
gg)
B C D E
+ 932.62 + (199 + 293)t
National Natlonal National National
Intercity - O p t | o n A4 Interclty - Option C DTV - 2 C o u n t r l e s DTV - 3 C o u n t r i e s
where M . = 130 kg. Mrc = (26. I i 3 + 9.473 Pc) kg[ I ], MB^rr = 20 kg (mass of batteries needed for the waiting tit is the RCS mass dependent on the PM mass.
728
M. T. RAw~zztyr'n and A. Fm'rx Table 3. Power dependent equipment mass models EQUIPMENT
MASS
7 . 3 7 PD
INV BATT a
(Kg)
45.588 PN + 43 308b
BDR
7.756 PN + 7"368b
BCR
1.606 PN + 1"525b
PCU SA
11.82
(PD + Ib) 31.03 PD
aNickel Hydrogen batterles[3l. b Con.ribution due to the Services Power, assumed
to be I000 w.
phases), and Mt~:x = 112 kg (comprehensive of RV sensors).
The above mathematical models have been applied to • solid-storable-cryogenic propulsion for GTO circularization • the Ariane 4 family launchers lift-off mass capabilities[4, 5l to evaluate the mission satisfaction capacity of the concept. As an example Table 5 shows the results for storable and cryogenic propulsion with ARlANE 44L, in terms of available night power for the P/ L against the required one. Option a requires then eithcr • the launch of two SM, or • a reduction in the lifetime of the platform (10 years against the envisaged ! 5 give a gain of 2-3 kW in the available PM) or • the development of a new cryogenic stage (storable propulsion being presently retained as the baseline subsystem solution), or • a reduction in the night operations, and • the adoption of electrical auxiliary propulsion.
Table 4. Mass breakdown o f the SM items non-dependent on power (option a) ITEM
TC TTC+DH
MASS (Kg)
35 70
ACS
150
STR
250
DOCK
RCS a
200 369+568
aMRc s - 0 . 1 0 2 5 MEOL - O.1025(MSM+ MpM)EO L Ill
Option b, on the other hand, brings to different mathematical models, where: MsM = 1. I (Mpcu + Ms^ + MTC + Myrc ÷ D, + M^cs + MSTR+ MDOCK)MAX = 47 PaM,x + 846 = 1928 kg MpM ---- I. I (MsTn + Mtc + M~cK + Me^yr +
MeDR
+ MncR + MINV)+ Me/L + MRcs where M~cs is a standard quantity, evaluated on the basis of the mass available on Ariane for the heaviest payload module. Table 6 shows the platform lifetime, mission by mission, if storable propellant is used for RC$, for Ariane 44 LP and Ariane 44L. The most appealing features of such an option (to be confirmed by the subsystem studies) are • low cost in the procurement of the standard SM • standardization in the primary and secondary propulsion subsystem for the PM's • optimization of the A R I A N E (44L) lift-off mass capabilities • adoption of state of the art bipropellant thrusters for the RCS • a minor decrease in lifetime of the unserviced platform with respect to the goal of 15 years. 5. CONCLUSIONS
The Platform described, M.E.G.A.L.O.S., which has been proposed to satisfy some well defined telecommunication requirements, can be considered as a promising "brick" for more ambitious missions, both in terms of power demands and of antennae dimensions (provided compatibility with the A R I A N E fairing dimensions is verified). The technology developments required, whose plans shall be detailed as an output of the overall study, could be achieved with medium term programs, being on the other hand well aligned with the current European activities.
729
M.E.G.A.L.O.S. Table 5. Option a: TLC power available during night (single SM, Aflame~4L. 15 years lifetime) P (gw) MISSION ID. N REQUIRED
P. AVAIL. (Kw) (~TORABLE ABM)
P AVAIL. (Kw) (C~YOGEN. ABM)
6.98
>6.98
>6.98
7.2]
>7.21
>7.21
4.82
4.8
>4.82
12.72
1.5
10.78
15.82
0.94
7.4
2" SM REQ.
2.2
>2.2 5.45
10.56 2.2
>2.2
O.
>0.
table 6. Obtion b: Unserviced platform lifetime (storable ABM and RCS) MISSION ID. N
LIFETIME (Y)
LIFETIME (Y)
(ARIANE 44LP)
(ARIANE 44L)
:,15
>15
14.1
1,1.67
12.2
>15
10.87 13.96 II.5 12.82
13.04
The result could be a space segment highly flexible, able to support different mission requirements with only minor changes in the basic configuration, and making the maximum use of European know-how, technologies and facilities. APPENDIX
Nomenclature ACS Attitude Control System ABM Apogee Boost Motor APM Antenna Pointing Mechanism BA'Fr Batteries BCR Battery Charge Regulator BDR Battery Discharge Regulator BOL Beginning of Life DH Data Handling DOCK Docking DTV Direct Television d V Velocity increment EOL End of Life ERTS European Regional Trunk Service GEO Geostationary Orbit GTO Gcostationary Transfer Orbit IL lntcrplatform Link INV Inverter (or DC/DC converter) M Mass NSM (Multi) national Service Mission Pc Conductive dissipation Po Payload power required for day operation PD,ss Power to be dissipated
Ps PCU P/L PM RCS RV SA SDM SM STR TC TF TLC
Payload power required for night operation Power Control Unit Payload Payload Module Reaction Control System Rendez-Vous Solar Array(s) Service Dedicated Mission Service Module Structure Thermal Control Telephony Telecommunication REFERENCES
I. Shuttle dedicated large platforms for TLC payloads. AERITALIA, ESTEC Contract 3940/79/NL/AK. Final Report (Dec. 1981l. 2. Conceptual design study. ,gASP. Final briefing. McDonn¢l Douglas (Oct. 1981). 3. Prediction of thermal behaviour of metal hydrogen battery cells. Elcktronic Centralen. ESTEC Contract 3346/NL/77/HP(SC). Final Report. 4. Internal Review. Ariane Programme. ESA AR/94 (Nov. 1981). 5. ARIANE 4. ARIANESPACE (Oct. 1981). 6. A. W. Preukschat Cost assessment of communication satellite systems as function of satellite reliability. STM218 (ESTEC) (June 1980). 7. Continued studies of the future European TLC satellite programs. Final Report. £SA £X£C (79)3 (July 1979).