Effect of specific impulse limitations on NEP and SEP missions

Paper number

IAC-16,A5,2,3,x31983

Author

Mrs. porzia federica Maffione, Politecnico di Torino, Italy

Coauthor

Prof. Giancarlo Genta, Politecnico di Torino, Italy

Year

2016

Abstract

The trajectory and the thrust profile for solar electric propulsion and nuclear electric propulsion spacecraft are optimized assuming that the specific impulse is variable.
This is realistic when using variable specifc impulse thrusters like VASIMR.
In previous works a simple approach to optimize Earth Mars cruise for SEP and NEP spacecraft was applied assuming that no limitation is present for the range of variation for the specific impulse. This assumption is however not realistic because present electric propulsion devices have a limited range of specific impulse, for instance between 1000 and 5000 seconds.
In this paper low thrust missions from Earth to Mars are studied considering that the thruster has a limited specific impulse range, by decreasing the generator power when the optimization would lead a specific impulse in excess to realistic values, so that the thrust is maintained at the same level computed for the optimized thrust profile.
As a result, an increase of the fuel consumption with respect to the ideal case is obtained. Such an increase is more limited in the case of fast mission with a high specific mass of the generator, while it is larger in the case of slower (cargo) missions, particulary when performed with an advanced generator. This means that the higher is the performance of the generator, the higher must also be the performance of the thruster.
Some examples applied to human Mars missions conclude the paper.

Abstract document

IAC-16,A5,2,3,x31983.brief.pdf

Manuscript document

IAC-16,A5,2,3,x31983.pdf (🔒 authorized access only).

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