Team Leader: Josué Zabeau (Mechanical Engineering, 1st cycle)
This payload intends to host in its 3U CubeSat is an autonomous, miniaturized greenhouse in which to grow a small plant. The scientific objective of this module is to study the lifecycle of the plant in an environment characterized by both microgravity and harsh light and temperature conditions.
For this experiment, we chose the Arabidopsis Thaliana, as it is a small, flowering, and edible plant that has often been used as a model organism by biologists.
Seeds of the plant will be placed in the module together with the necessary nutrients (enriched water and air) before lunch and updates on the status of its growth will be periodically sent to our ground stations for the entire duration of the mission.
Similarly to the other payload of Hathor (the ionic propulsion module) the plant-growth module also occupies approximately half of a CubeSat unit (i.e. 94 by 94 by 40 millimetres with an internal volume reserved for the plant of 65cm) while, at 400 grams, it is 25% heavier.
The module will include sensors to measure temperature, pressure, humidity, and the levels of oxygen and CO2 in the greenhouse.
Providing sufficient lighting, heat, and pressure under the constraint of a limited power budget;
Being able to correctly assess the status of the plant with the given array of sensors;
Making the growth and monitoring process entirely automated without the use of moving parts. This payload also give new possibilities for all universities by allowing them, after having validated the incubator in real conditions, to conduct their own microgravity research programs for studies for biology applications at a reduced cost.
This seccond payload developed by PolyOrbite for Hathor, its 3U CubeSat, is an electric propulsion system.
The design consists of four identical electrospray thrusters with a diameter of 35mm.
All the thrusters points in the same direction and are placed on one of the satellite’s two extremities.
Despite providing very high efficiency, electrospray thrusters are usually plagued by very low total thrust.
Electrospray thrusters, just like other ion thrusters, generate thrust from the acceleration of ions—an ionic liquid in this case (22 grams of fuel are sufficient to obtain a final speed of 150 m/s with a 4 kilograms satellite).
Coupled with the attitude determination and control systems, this electric propulsion system will allow the CubeSat to perform complex maneuvers for a longer period of time and without the risks entailed by conventional thrusters.
With regard to its technical specifications, the propulsion module is designed to occupy half of a CubeSat unit (i.e. 94 by 94 by 40 millimetres) and weight approximately 300 grams.
Our design is based on the one proposed by the MIT and the EPFL and it aims at providing a total thrust ranging from 7 to 40 micronewton with a specific impulse of 3030-3150 seconds.
The design shall also work with power budget that could range between 0.2 and 1.1 watts and it will grant three years of operations (with a 6 months error)
The stringent power budget provided by a small nanosatellite;
Ensuring the reliability necessary to operate for multiple years;
Its integration and coordination with the attitude determination and control systems.
Once implemented and integrate in Hathor, the propulsion module will be used for multiple goals:
As a technology demonstrator for electrospray thrusters;
To make a case for the use of nanosatellites in the context of interplanetary and deep space travel;
More concretely, to reduce the orbit lifetime of Hathor and validate ionic propulsion as a deorbiting technology for CubeSats.