I4iS May 2024 Newsletter

First European Interstellar Symposium

The University of Luxembourg’s First European Interstellar Symposium will take place in December 2024, with the IRG’s input and guidance.

The Symposium and an Interstellar Art Show will be held at the European Convention Center in Luxembourg City, Luxembourg. This symposium will feature many of the leading voices in space exploration, culture, and more. The theme for the event is Building Our Home Among the Stars. Thus, there will be a particular focus on potential near-term demonstrations and missions that align with the technologies and systems required for future interstellar travel.

This European Interstellar Symposium aims to bring together a multi-disciplinary community dedicated to interstellar travel, and all interested parties are welcome to submit abstracts of their papers related to interstellar travel.

More information, as well as the link to submit papers, can be found on the IRG website: https://irg.space/first-european-interstellar-symposium/

Strategies for Interstellar Exploration

On 16 April 2024, Elsevier’s journal Advances in Space Research published an article by Johannes Lebert, Andreas M. Hein, and Martin Dziura titled “Optimal strategies for the exploration of nearby stars.”

Despite various proposals for interstellar probe concepts and relevant technologies, there is a lack of extensive literature on viable exploration strategies for journeys beyond just one-star systems. This article presents optimal strategies for the exploration of a large number of nearby stars.

After extensively discussing and defining variables and parameters, the paper uses computer simulations to determine the optimal route. The article provides a detailed breakdown of the algorithm used and how it works, as well as an analysis of the optimization results.

As one would expect from intuition, the mission return for a given mission duration increases with the probe number. For a certain range (number of probes smaller than 256) and given mission duration one finds that the number of explored stars J 1 scales with mission duration J 2 and probe number m according to J1 ~ J2 m0.66, which provides an initial guidance for future interstellar mission design. Furthermore, the routes and selection of stars vary depending on the number of probes used: When conducting missions with a large number of probes, stars close to the Solar System are given more focus. On the other hand, missions with a small number of probes include more distant stars to facilitate shorter transfers along the route.

The full paper can be found here: https://www.sciencedirect.com/science/article/pii/S0273117724003351

LED Sails

On 29 April 2024, engrxiv released a preprint by Chang Shen titled “Travel In Deep Dark Space with Giant LED Sail.”

The paper discusses the scientific feasibility of sending spacecraft to a neighboring star beyond our solar system using a giant LED sail. It first explains the LED sail concept, which is very similar to a light sail, except with an attached LED light source. The paper compares the efficiency of this propulsion mechanism to nuclear propulsion and traditional chemical propulsion, noting its promising nature. The paper then creates a model LED sail probe for a mission to Proxima Centauri.

Based on this design, the paper estimates the travel time, velocity, acceleration, and other parameters of the probe. It derives equations for calculating the amount of light and thus power needed for the sail, and also discusses the potential issues with such a probe.

The full paper can be found here: https://engrxiv.org/preprint/view/3692/6566

Making Independent Spacecraft

Open-access scientific journal MDPI published a paper by Junwei Zhang Liangqing Lyu on 27 April 2024 titled “A Spacecraft Onboard Autonomous Task Scheduling Method Based on Hierarchical Task Network-Timeline.”

To address the inherent challenges of deep space exploration – such as communication delays and the unpredictability of spacecraft environments – this study focuses on enhancing spacecraft adaptability and autonomy, which are essential for Autonomous Space Scientific Exploration. A pivotal aspect of this undertaking is the advancement of spacecraft task scheduling, which is integral to increasing spacecraft autonomy.

Current research in this domain predominantly revolves around mission timing planning and is primarily executed from ground stations. However, these plans often lack the granularity required for direct implementation by spacecraft. In response, this study proposes an innovative approach to augment spacecraft autonomy, introducing a method that articulately describes mission objectives and resource information. The paper designs a novel hierarchical task network-timeline (HTN-T) algorithm that addresses time constraints through horizontal and vertical expansions, building upon the resolution of logical constraints found in conventional planning methods. Furthermore, it introduces a priority-based strategy for resolving resource conflicts in spacecraft tasks. This algorithm is substantiated through validations in the paper.

The full article can be found here: https://www.mdpi.com/2226-4310/11/5/350

Thermal Conversion Technology

On April 28th, NASA published a paper titled “Comparative Analysis of Thermal Conversion Technologies for Deep Space Missions” by Sabah K. Bux et al.

The paper analyzes recent innovations and improvements to thermal energy technologies showing potential increases in radioisotope system efficiencies from current measurements of ~5-7% to efficiencies upwards of 20%. Radioisotope power systems (RPS) utilizing Plutonium-238 as a heat source for thermal-to-electric energy conversion are well established and have been used as a reliable power source for NASA’s deep space missions for sixty years.

This report surveys and ranks recent, innovative thermal-to-electric energy conversion research technologies. Technologies being developed at universities and industry are compared with respect to thermal conversion methods and relevant key performance parameters. It identifies key performance parameters such as system-specific power per kg, efficiency, power output, technology readiness level, and system mass and then utilizes an Analytical Hierarchy Process (AHP) to create weighted values for each evaluation criterion. The AHP tables combined with decision matrices create table scores for past, present, and potential future propulsion systems.

The full paper can be found here: https://ntrs.nasa.gov/api/citations/20220002940/downloads/2022%20NETS%20paper%20v4%20-%20Copy.pdf

Estimations for NASA’s ACS3 Solar Sail

On 8 May 2024, Livio Carzana et al. published a preprint on ResearchGate titled “----”

This mission will be the first Earth-bound solar-sail mission to fly so-called calibration steering laws. These steering laws are designed to expose the spacecraft to a variety of dynamical conditions to isolate the effects of different parameters on the mission dynamics, thereby facilitating the estimation of these parameters. This paper presents the set of candidate calibration steering laws of ACS3, highlighting their operational challenges and impact on the estimation of the sail’s reflectivity and specularity.

The results show that, for a conservative GPS position accuracy of 10 m, accurate estimation can be achieved by flying any of the proposed calibration laws. However, ACS3’s calibration steering laws were also found to introduce operational challenges that may hinder their implementation for extended periods of time such as decreased power generation capability of solar arrays.

The full paper can be found here: https://www.researchgate.net/profile/Livio-Carzana/publication/380376220_Calibration_Steering_Laws_to_Estimate_the_Optical_Properties_of_NASA's_ACS3_Solar_Sail/links/663a12bb7091b94e93f680e2/Calibration-Steering-Laws-to-Estimate-the-Optical-Properties-of-NASAs-ACS3-Solar-Sail.pdf

Project Hephaistos

The scientific search for intelligent life in outer space represents one of the most compelling quests that humanity has ever undertaken. With SETI, astronomers have scanned the skies for any hints of extraterrestrial life. Unfortunately, this has been largely unsuccessful. Alternative strategies should be considered, and that is where Project Hephaistos comes in.

Led by Erik Zackrisson of Uppsala University, Sweden, it focuses on the search for signatures of extraterrestrial technology rather than looking for signals deliberately sent our way. The project is explained in three papers. The first outlines the search for extraterrestrial supercivilizations and interesting outlier galaxies. The second discusses Dyson spheres - a hypothetical megastructure that encompasses a star and captures a large percentage of its solar power output - and Dysonian technology, noting potential signs of their existence. The final paper explores how Dyson spheres could be detected by the project and explores the likelihood of success compared to SETI.

All the papers and more information can be found here: https://www.astro.uu.se/~ez/hephaistos/hephaistos.html#home.

I4is Science Fiction Anthology

You will have seen from earlier Newsletters that we are still looking for broadly interstellar-themed short stories for the upcoming “The i4is Science Fiction Anthology.”

Further information is available – from the editors [email protected] and [email protected]