2018.P.1.5. Composite Stucture for Deep Space CubeSats

Author(s)

Fernando Hübner (1)
Jean-Michel Klein (1)
Gilles Bailet (2)
Christophe O. Laux (2)

CentraleSupélec, Université Paris Saclay, France
Laboratoire EM2C, CNRS, Université Paris-Saclay, France

Session

P.1

Keywords

structure, radiation, light weight, Moon

Abstract

Introduction: The development of a CubeSat’s structure is challenging due to the harsh space environment and the limited mass/volume available to withstand launch loads and cosmic radiation.
The work presented in this poster has followed the objectives and requirements of the SIRONA mission, a lunar orbiter lead by the student space center of CentraleSupélec (CS^3). This CubeSat is a 12U, hence 22.4×22.4×34 cm^3 and will travel from Earth to the Moon during a maximum of 6 months and perform its scientific mission around the Moon for at least 6 additional months.
The strict mission requirements impose structural optimization in order to respond to two reasons:
1. The high costs of launch opportunities constrain the economic viability of the entire mission according to the total mass of the vehicle.
2. All CubeSat missions have an associated scientific of technological goal, thus the volume minimization will enable an increased available volume for additional payloads.
Structural loads: the structure of a CubeSat has to withstand launch and deployment loads: the spacecraft has to endure great accelerations that will reach values over 10g as well as a series of shock loads along each one of the three axes, with accelerations that vary between 5g and 2000g and a wide range of frequencies. Moreover, a modal analysis must be performed to determine the natural frequencies of the structure: the first resonance frequency must be superior to 90 Hz.
Radiation shielding design: due to weak lunar magnetic field, the nanosatellite will be submitted to extremely high doses of radiation, which could easily damage its electronics (limited to a dose of 15 krad).
Composite structure proposed: the strategy uses a composite structure made of aluminum 7075 frame for sturdiness and a sandwich of Mylar with high density polyethylene for light weight radiation shielding panels.
Validation of the proposed design: The proposed structure passed the following tests:
1. Cosmic galactic rays’ conditions have been used in conjunction of the GRAS Monte Carlo method in SPENVIS code for the radiation tolerance assessment.
2. The structural simulations performed used the code CATIA for each of the requirements described previously. An optimization was conducted by choosing the set of geometrical parameters of the structure, in order to reduce the mass.
Conclusion: This design allows to propose a 2kg structure in 12U format able to fulfill mission requirements of the SIRONA lunar orbiter as opposed to heavy designs using full aluminum panels.