Deployment requirements for deorbiting electrodynamic tether technology

Abstract

In the last decades, green deorbiting technologies have begun to be investigated and have raised a great interest in the space community. Among the others, electrodynamic tethers appear to be a promising option. By interacting with the surrounding ionosphere, electrodynamic tethers generate a drag Lorentz force to decrease the orbit altitude of the satellite, causing its re-entry in the atmosphere without using propellant. In this work, the requirements that drive the design of the deployment mechanism proposed for the H2020 Project E.T.PACK—Electrodynamic Tether Technology for Passive Consumable-less Deorbit Kit—are presented and discussed. Additionally, this work presents the synthesis of the reference profiles used by the motor of the deployer to make the tethered system reach the desired final conditions. The result is a strategy for deploying electrodynamic tape-shaped tethers used for deorbiting satellites at the end of their operational life.

Validation of enabling technologies for deorbiting devices based on electrodynamic tethers

“…The reference profiles for the deployment maneuver were first obtained using the BOCOP © software [64], and then fine-tuned in the code DEPLOY, developed in MATLAB © , to smooth out the tether tension profile mainly at the end of deployment [65]. The equations of the deployment dynamics implemented in the software tool DEPLOY can be found in [65].…”

“…The reference profiles for the deployment maneuver were first obtained using the BOCOP © software [64], and then fine-tuned in the code DEPLOY, developed in MATLAB © , to smooth out the tether tension profile mainly at the end of deployment [65]. The equations of the deployment dynamics implemented in the software tool DEPLOY can be found in [65]. The three main steps followed to obtain the deployment reference profiles are shown in Figure 3, where the block "'Nonlinear boundary value problem" implements the differential equations describing the deployment dynamics for tethers and uses the BOCOP © software to find a reference trajectory for deployment that satisfies the following boundary conditions: initial conditions on ,   ,  and   , final conditions on  and   , minimizing the final libration angle and libration rate   and    , respectively.…”

Experimental Validation of a Deployment Mechanism for Tape-tethered Satellites

“…They can be classified in three main categories: rotating reels, stationary spools, and folded "origami" tethers; the latter solution is usually preferred for short tethers. In the framework of the E.T.PACK project, a deployer kit prototype is currently under development to deploy up to a three-kilometer long tape tether [19]. The kit is designed to act as tip mass and to provide the initial momentum thanks to a small propulsive unit (cold gas actuator).…”

“…The reference profiles for the deployment maneuver were obtained using the BOCOP software [24] to solve a boundary value problem: to find the time profiles of the control tether tension T p (t), the tether length l(t) and the libration angle θ(t) that satisfy the deployment dynamics equations and the following boundary conditions: l 0 = 0.5 m, l0 = 0 m/s, θ 0 = 3.4 rad, θ0 = 0 rad/s, l f = 3000 m, lf = 0 m/s, θ f = π rad, θf = 0 rad/s. For additional details see [19]. The resulting reference deployment trajectory is shown in Fig.…”

Space tethers: parameters reconstructions and tests

“…Consequently, benefits in using Tether Systems are manifolds and its value lies in the fact that they are able to generate clean propulsion in total autonomy by exploiting physical principles: angular moment conservation, pairing between energy generation and thrust or vice versa between a decrease in orbital energy and production of electrodynamic drag. By releasing satellites from sensitive space environment as the ISS employing inert tethers, the external contamination around that platform is greatly reduced [1,2]; equipping Satellites with an electrodynamic tether [3,4] ensures independence from the storage and use of propellant in orbit. Consequently, the tasks of deorbiting, re-entry and reboost and, in general, passive propulsion can be addressed by a technology that is increasingly mass-efficient as the time in orbit increases when compared to chemical systems.…”