low thrust transfer to sun-earth l 1 and l 2 points with a constraint on the thrust direction...

Low Thrust Transfer to Sun-Earth Low Thrust Transfer to Sun-Earth LL11 and and LL22 Points Points

with a Constraint on the Thrust Directionwith a Constraint on the Thrust Direction

LIBRATION POINT ORBITS AND APPLICATIONSParador d'Aiguablava, Girona, Spain

10 – 14 June, 2002

Alexander A. Sukhanov Alexander A. Sukhanov Natan A. EismontNatan A. Eismont Space Research Institute (IKI) Space Research Institute (IKI) of Russian Academy of Sciencesof Russian Academy of SciencesMoscow, RussiaMoscow, Russia

An experimental low-thrust mission to the Sun-Earth L1 and L2 points is considered (Module-M mission)

MISSION GOALS• Solar wind exploration• Magnetic storm prediction• Testing new technologies

MISSION STEPS• Delivery of the spacecraft component to the International Space

Station (ISS) by Progress cargo spaceship• Assembling the spacecraft at ISS• Launch from ISS and transfer to L1 using Solar Electric Propulsion• Transfer to the L1 point and insertion into a halo orbit• Launch from the halo orbit, transfer to L2 point, and insertion into a

halo orbit


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SPACECRAFT CONCEPT• Spacecraft is spin-stabilized with spin axis orthogonal to the Sun• Solar arrays form a cylindrical surface coaxial to the spin axis• Thrusters are directed along the spin axis in both directions


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THRUSTER PARAMETERSName D-38Type TALPower 750 WSpecific impulse 2200 sEfficiency (including loss in PPU) 0.5Thrust force 0.035 NMass flow rate 1.6 10-6 kg/sResource 3000 hoursPropellant xenon


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SPACECRAFT PARAMETERSWet initial mass 290 kgXenon mass 85 kgCharacteristic velocity 7.5 km/sSolar panel area 110 m2

Effective solar array area 30 m2

Electric power 3 kWNumber of thrusters 8Number of simultaneously running thrusters 2Maximum time of the low thrust run 7340 hr


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SPIRAL TRANSFER


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ORBIT SHADOWING• Launch in June-July or December-January minimizes the orbit

shadowing down to 7.5 percent of the spiral transfer time• These optimal launch dates lead to a high (> 50°) inclination to the

ecliptic plane• Launch in May or November was selected for the further analysis:

the shadowing is 8.5 percent, inclination to the ecliptic plane is 35°


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PARAMETERS OF THE SPIRAL TRANSFERTime of flight 280 daysNumber of orbits 1330Consumed characteristic velocity 6850 m/sPropellant consumption 78.9 kgSpacecraft mass 211.1 kg


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TRANSFER TO L1 AND INSERTION INTO A HALO ORBITTime of flight (after the spiral) 140 daysCharacteristic velocity of the insertion into halo 290 m/sPropellant consumption 2.8 kgSpacecraft mass in halo 208.3 kg

Amplitude Ay of the halo orbit 62,000 km


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L1 TO L2 TRANSFER WITH ZERO COMPLETE ORBITS

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10 – 14 June, 2002

L1 TO L2 TRANSFER WITH ZERO COMPLETE ORBITS

Consumed characteristic velocity 306 m/s

v1 50 m/s

v2 196 m/s

v3 60 m/s

Time between v1 and v2 70 daysThe transfer duration 181 daysPropellant consumption 2.9 kgFinal spacecraft mass 205.4 kg

Ay amplitude of the L2 halo 800,000 km


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L1 TO L2 TRANSFER WITH ONE COMPLETE ORBIT

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10 – 14 June, 2002


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L1 TO L2 TRANSFER WITH ONE COMPLETE ORBIT


v1 65 m/s

v2 18 m/s

v3 141 m/s



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L1 TO L2 TRANSFER WITH TWO COMPLETE ORBITS


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L1 TO L2 TRANSFER WITH TWO COMPLETE ORBITS


v1 35 m/s

v2 2 m/s

v3 33 m/s




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SYMMETRIC TWO-IMPULSE L1 TO L2 TRANSFER


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SYMMETRIC TWO-IMPULSE L1 TO L2 TRANSFER


v1 43 m/s

v2 43 m/sThe transfer duration 307 daysPropellant consumption 0.8 kgFinal spacecraft mass 207.5 kg



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SUMMARY OF THE TRANSFERS

Operation

Flight time, months

Total v, km/s

Total xenon consumption,

kg

S/C mass, kg

Launch 0 0 0 290

Acceleration in the spiral orbit 9.3 6.85 78.9 211.1

Transfer to and insertion in L1 halo 14.0 7.14 81.7 208.3

Transfer to and insertion in L2 halo 20 – 24.5 7.21 – 7.45 82.4 – 84.6 205.4 – 207.6

Rest for the correction maneuvers – 0.05 – 0.29 0.4 – 2.6 –


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CONCLUSIONS

• The low thrust orthogonal to the Sun allows performing: – transfer to L1 or L2 Sun-Earth point;– insertion into a halo orbit;– halo-to-halo transfer.This makes it possible to simplify the spacecraft design and control

• Duration of both the Earth-to-halo and halo-to-halo transfers can be shortened by means of a higher propellant consumption

• Propellant consumption can be reduced by means of the duration increase for both the Earth-to-halo and halo-to-halo transfers


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low thrust transfer to sun-earth l 1 and l 2 points with a constraint on the thrust direction...

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