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Space Propulsion - IAP/TU Wien

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Repositioning, cont‘d<br />

<strong>Space</strong> <strong>Propulsion</strong><br />

The elements of a geosynchronous orbit are<br />

r =<br />

42,164.17 km (circular)<br />

P =<br />

86,164.09 s<br />

V =<br />

3.07466 km/s<br />

ΔP is equal to the time required for 2 deg<br />

of motion on a geosynchronous orbit<br />

0<br />

Δϕ<br />

2 *86,164.09<br />

ΔP = P =<br />

=<br />

360 360<br />

478.689<br />

[ s]<br />

The period for the spacecraft on the<br />

elliptical reposition orbit is<br />

semimajor axis of the reposition orbit<br />

P = 86,164.09 + 478.689 = 86,642.78 [s]<br />

2<br />

2<br />

P μ (86,642.78) (398,600)<br />

a = 3 = 3<br />

= 42,320<br />

2<br />

2<br />

4π<br />

4π<br />

[ km]<br />

velocity at periapsis of an elliptical orbit<br />

with semimajor axis a<br />

V 2μ<br />

μ 2(398,600) 398,600<br />

= − =<br />

− 3.08032<br />

r a 42164 42320<br />

=<br />

[ km / s]<br />

velocity change to place the spacecraft<br />

on the reposition ellipse<br />

3.08032km/s - 3.07466km/s = 5.66 m/s<br />

The same velocity change (in the opposite direction<br />

is necessary for recirculation of repositioning orbit<br />

Propellant consumption under<br />

assumption of negligible mass change<br />

⎡ ⎛ V ⎞ ⎤ ⎧ ⎡11.32⎤<br />

⎫<br />

m<br />

p<br />

m<br />

f ⎢exp⎜<br />

Δ<br />

=<br />

⎟ −1⎥<br />

= 1000⎨exp<br />

−1⎬<br />

= 3.66<br />

I<br />

⎢<br />

sp<br />

⎩ ⎣ 3100 ⎥<br />

⎢<br />

⎣ ⎝ ⎠ ⎥⎦<br />

⎦ ⎭<br />

[ kg]

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