darianvp
commented
6 years ago The equatorial orbit configuration considered is inspired by the Brandhorst Lunar SPS system proposal studied in the earlier issues. An equatorial sps orbit is chosen to target a rover at 45N latitude. The altitudes of the orbits considered are limited to the range of the south pole study (10-5000 km), based on the application of the pointing error and minimum power requirement constraints to the WPT link.
The processed results of this parametric scan are:
MeanMaxRange_Equatorial_IncrementedRes.txt MeanMinRange_Equatorial_IncrementedRes.txt MeanRange_Equatorial_IncrementedRes.txt MeanStoredPowerEvent_Equatorial_IncrementedRes.txt TotalActive_Equatorial_IncrementedRes.txt TotalBlackout_Equatorial_IncrementedRes.txt TotalStoredPowerEvent_Equatorial_IncrementedRes.txt MaxActive_Equatorial_IncrementedRes.txt MaxBlackout_Equatorial_IncrementedRes.txt MaxStoredPowerEvent_Equatorial_IncrementedRes.txt MeanActive_Equatorial_IncrementedRes.txt MeanBlackout_Equatorial_IncrementedRes.txt
The unconstrained design space generated from this data:
Due to the mismatch between the orbital inclination and the target location, some low altitude orbits cannot access the target. As a result these orbits are removed from the total access time and total power delivered design spaces. The blackout duration at the target for these orbits are assumed to be the same as the eclipse events.
Overall this design configuration has a much lower active time than the south pole target / polar sps orbit. This is a combination of the target/orbit inclination mismatch and the fact that the equatorial SPS spends significantly more time eclipsed than the polar sps, especially when within range of the target.
The maximum blackout duration has a strange behaviour, however the total blackout duration takes a smooth predictable shape (total blackout decreasing as altitude increases):
When applying the constraint for maximum allowable blackout duration, the gradient is revealed which shows that the maximum blackout duration is increasing with orbit altitude. My hypothesis here is that the lower altitude orbits, with shorter orbital periods, revisit the target faster and thus break up potential long blackout periods faster.
The plot shows that the lowest altitude (shortest period) above a certain threshold (approximately 1000 km) is the highest performing with respect to minimizing maximum blackout duration. My hypothesis is that this is because the revisit rate of the SPS is highest at this orbit (short period) while the the altitude of the orbit is still high enough to guarantee that the SPS will be properly sunlit while overhead the eclipsed target. I will investigate further in STK
MatthewGrim
This issue is concerning the updates made to the constrained SPS design tool in order to accommodate the STK data report results of the equatorial SPS configuration.