Nanosatellites have established their importance in low-Earth orbit (LEO), and it is common for student teams to build them for educational and technology demonstration purposes. The next challenge is the technology maturity for deep-space missions. The LEO serves as a relevant environment for maturing the spacecraft design. Here we present the ESTCube-2 mission, which will be launched onboard VEGA-C VV23. The satellite was developed as a technology demonstrator for the future deep-space mission by the Estonian Student Satellite Program. The ultimate vision of the program is to use the electric solar wind sail (E-sail) technology in an interplanetary environment to traverse the solar system using lightweight propulsion means. Additional experiments were added to demonstrate all necessary technologies to use the E-sail payload onboard ESTCube-3, the next nanospacecraft targeting the lunar orbit. The E-sail demonstration requires a high-angular velocity spin-up to deploy a tether, resulting in a need for a custom satellite bus. In addition, the satellite includes deep-space prototypes: deployable structures; compact avionics stack electronics (including side panels); star tracker; reaction wheels; and cold–gas propulsion. During the development, two additional payloads were added to the design of ESTCube-2, one for Earth observation of the Normalized Difference Vegetation Index and the other for corrosion testing in the space of thin-film materials. The ESTCube-2 satellite has been finished and tested in time for delivery to the launcher. Eventually, the project proved highly complex, making the team lower its ambitions and optimize the development of electronics, software, and mechanical structure. The ESTCube-2 team dealt with budgetary constraints, student management problems during a pandemic, and issues in the documentation approach. Beyond management techniques, the project required leadership that kept the team aware of the big picture and willing to finish a complex satellite platform. The paper discusses the ESTCube-2 design and its development, highlights the team’s main technical, management, and leadership issues, and presents suggestions for nanosatellite and nanospacecraft developers.

The electric solar wind sail, or E-sail, is a novel deep space propulsion concept which has not been demonstrated in space yet. While the solar wind is the authentic operational environment of the electric sail, its fundamentals can be demonstrated in the ionosphere where the E-sail can be used as a plasma brake for deorbiting. Two missions to be launched in 2023, Foresail-1p and ESTCube-2, will attempt to demonstrate Coulomb drag propulsion (an umbrella term for the E-sail and plasma brake) in low Earth orbit. This paper presents the next step of bringing the E-sail to deep space—we provide the initial modelling and trajectory analysis of demonstrating the E-sail in solar wind. The preliminary analysis assumes a six-unit cubesat being inserted in the lunar orbit where it deploys several hundred meters of the E-sail tether and charges the tether at 10–20 kV. The spacecraft will experience acceleration due to the solar wind particles being deflected by the electrostatic sheath around the charged tether. The paper includes two new concepts: the software architecture of a new mission design tool, the Electric Sail Mission Expeditor (ESME), and the initial E-sail experiment design for the lunar orbit. Our solar-wind simulation places the Electric Sail Test Cube (ESTCube) lunar cubesat with the E-sail tether in average solar wind conditions and we estimate a force of $1.51\times {10}^{-4}$ N produced by the Coulomb drag on a 2 km tether charged to 20 kV. Our trajectory analysis takes the 15 kg cubesat from the lunar back to the Earth orbit in under three years assuming a 2 km long tether and 20 kV. The results of this paper are used to set scientific requirements for the conceptional ESTCube lunar nanospacecraft mission design to be published subsequently in the Special Issue “Advances in CubeSat Sails and Tethers”.

The electric solar wind sail, or E-sail, is a propellantless interplanetary propulsion system concept. By deflecting solar wind particles off their original course, it can generate a propulsive effect with nothing more than an electric charge. The high-voltage charge is applied to one or multiple centrifugally deployed hair-thin tethers, around which an electrostatic sheath is created. Electron emitters are required to compensate for the electron current gathered by the tether. The electric sail can also be utilised in low Earth orbit, or LEO, when passing through the ionosphere, where it serves as a plasma brake for deorbiting—several missions have been dedicated to LEO demonstration. In this article, we propose the ESTCube-LuNa mission concept and the preliminary cubesat design to be launched into the Moon’s orbit, where the solar wind is uninterrupted, except for the lunar wake and when the Moon is in the Earth’s magnetosphere. This article introduces E-sail demonstration experiments and the preliminary payload design, along with E-sail thrust validation and environment characterisation methods, a cis-lunar cubesat platform solution and an early concept of operations. The proposed lunar nanospacecraft concept is designed without a deep space network, typically used for lunar and deep space operations. Instead, radio telescopes are being repurposed for communications and radio frequency ranging, and celestial optical navigation is developed for on-board orbit determination.