Nebula Public Library

The interest in HAPS is increasing in many areas, from military and security to commercial services. On the telecommunications side, HAPS are seen as relays to provide internet services worldwide, and as a possible complement to satellites. On the Earth observation side, the near-space location of the HAPS enables new services or could improve the existing satellite ones. From the satellite or from the HAPS market sides, it is important to understand how both systems can offer complementary services, and what the possible synergies between them are.

Propulsion passivation is most of the time feasible for running missions, using thrusters and existing AOCS modes, whatever the number of tanks and for both monopropellant and bipropellant systems.
For monopropellant systems the propulsion passivation may be:
-Partial for tank(s) with membrane. All the hydrazine under the membrane may be depleted but the pressurant gas above the membrane cannot be depleted. The final tank pressure is close to typically 5 bars at the end of mission.

All spacecraft in Earth orbit are exposed to the risk of impact with Micrometeoroids and Orbital Debris (M/OD). Because of the large collision velocities, Hypervelocity Impacts (HVI) with M/OD may cause significant damage to various subsystems and components up to mission failure.