Happy New Year!
The i4is team wishes you a happy and prosperous New Year. Here’s to hoping 2024 brings us more interstellar innovations and breakthroughs than ever before.
I4is Science Fiction Book Club – Next meeting 11th January
For the next meeting, the i4is SF Book Club members are considering again ‘The Road to Science Fiction Volume 3: From Heinlein to Here’ edited by James Gunn, a collection of selected short stories from the ‘Heinlein to Here’ era.
We will be reading and discussing stories 18, Harrison Bergeron by Kurt Vonnegut, Jr. and 19, The Streets of Ashkelon by Harry Harrison but also open for more discussion/debate.
The meeting will be on Zoom, Thursday 9th November at 1900 UK time. Mark the date in your calendar! Please email bookclub@i4is.org for the meeting link.
I4is Science Fiction Anthology
You will have seen from earlier Newsletters that we are still looking for short stories for the upcoming “The i4is Science Fiction Anthology.” To ensure a level playing field, submissions must be in Shunn’s Modern Manuscript format, the widespread standard for fiction submissions. https://www.shunn.net/format/story/ (Make sure you click the Modern tab.)
Further information is available – or just send submissions as email attachments – to the editors sarah.margree@i4is.org and jean.asselin@i4is.org
Calculating the Reflectivity of Lightsails
On December 21st, the Astronomical Journal published a paper by Refath Bari titled “Reflection from Inclined, Relativistic Light Sails.” Lightsails have emerged as one of the most promising alternative propulsion technologies for interstellar exploration. Of particular interest have been sail systems, which leverage blackbody radiation from stars or infrared emissions from planets to propel spacecraft to relativistic velocities. Despite their appealing simplicity, light sails pose several engineering problems, such as structural stability. This paper aims to address the need for a formula of relativistic reflection generalized to inclined sails.
The paper presents an overview of the basic mechanics governing light reflection from mirrors, connecting lightsails to the moving mirror problem. It thus builds off previous work to solve this problem to craft a set of equations explaining the relativistic reflection of solar radiation from a light sail moving at a velocity v, inclined at an arbitrary angle θ. After deriving this equation, the paper explores possible further derivations and uses for it, such as calculating redshift. The full paper can be found here: https://iopscience.iop.org/article/10.3847/1538-3881/ad10b0/pdf
Broadband Reflectors for Lightsails
Cornell’s preprint server ARXIV published a paper by Jin Chang et al on December 7th titled “Broadband, High-Reflectivity Dielectric Mirrors at Wafer Scale: Combining Photonic Crystal and Metasurface Architectures for Advanced Lightsails.” The paper addresses one of the main material challenges of lightsail technology: constructing a broad-band reflector capable of covering the Doppler-shifted laser wavelength spectrum during the spacecraft’s high-velocity acceleration phase. While there have been efforts to develop such a reflector through the addition of a Fano resonator and 2D photonic crystals, such solutions are no longer feasible due to recent research demonstrating the need for a SiO2 layer on the lightsail.
This paper offers a novel solution by pioneering a bilayer membrane structure using a silicon nitride photonic crystal atop a flat silicon layer. This approach encompasses the incorporation of a high refractive index layer beneath the photonic crystal membrane, resulting in a significant expansion of the reflectance spectrum. The bilayer configuration accomplishes broadband reflectivity (exceeding 70%) spanning from 1300 to nearly 1550 nm, whereas a conventional single-layer photonic crystal only allows a reflectivity within the range of a few tens of nanometers. While this reflectivity is still a bit low, it is a vast improvement from previous designs. The paper provides a detailed overview of the design and simulations involving this solution, demonstrating its strong performance and outlining how it could be manufactured. It notes possible areas of improvement and suggests potential solutions such as using a gold mirror to minimize losses of the laser. The full paper can be found here: https://arxiv.org/abs/2312.04471
Communication Challenges with Relativistic Travel
On November 23rd, Cornell’s preprint server ARXIV published a paper by David Messerschmitt titled “Timing relationships and resulting communications challenges in relativistic travel.” It is no secret that communications between a spacecraft undertaking interstellar travel at near light speed to and from its launch site (the origin) and a landing site (the destination) face significant challenges. While this is not currently feasible, even communications at speeds of 3-4% of the speed of light face problems. This paper explores this issue, analyzing and illustrating the timing differences through a mathematical model, taking into account time dilation, propagation delay, and other factors. It also provides in-depth explanations of what each of these effects are and their fundamental principles.
The paper then explores how this communication problem may be addressed and subverted, such as using multiple clocks with different calibrations and the use of a continuous stream-based communication system. Such solutions are also modelled and explained, with their limitations discussed as well. The paper also touched upon idealizing mission trajectories for smoother communication. The full paper can be found here: https://arxiv.org/abs/2311.14039
Technology Demonstrations for Deep Space missions
On December 1st, the Japanese electronic journal J-STAGE published a paper titled “Deep Space Exploration Technology Demonstrator DESTINY+” by Hiroyuki Toyota et al. DESTINY+ is a small-class science program led by ISAS of JAXA and is under development for launch sometime between 2024 and 2026 with both engineering and science goals. The engineering goal is to develop technologies that will enable future exploration of the far reaches of our solar system and beyond. Ion engine operation technology in planetary orbit and high-speed flyby technology of small bodies will be demonstrated with this mission. The scientific goal is to elucidate the characteristics of dust that may have transported organic matter to the primordial earth.
This paper provides a complete overview of the mission, including an overall timeline and an in-depth explanation of the spacecraft design. Various subsystems of the spacecraft are discussed, and key design choices are explained – such as the use of X-band communication. The paper even includes detailed CAD models of various spacecraft components. The full paper can be found here: https://www.jstage.jst.go.jp/article/jesa/1/0/1_90/_pdf/-char/ja
Antimatter Propulsion
On December 3rd, the International Journal for Research in Applied Science & Engineering Technology published a paper by Ruichen Zhang titled “Antimatter Propulsion and its Application for Interstellar Travel: A Review.” Although highly theoretical, antimatter propulsion is by far the most powerful alternative propulsion technology for interstellar exploration. This paper provides a brief introduction to the concept of antimatter and how it may be used as a fuel. It discusses the various issues with producing and storing antimatter and presents possible solutions.
The paper also presents multiple sample designs of antimatter propulsion systems with detailed schematic diagrams. It provides a comparison of these different options, noting their strengths and weaknesses as well as further areas for research. The full paper can be found here: https://www.ijraset.com/best-journal/antimatter-propulsion-and-its-application-in-interstellar-travel-a-review
Gliding on Solar Winds
Cornell’s preprint server ARXIV published a paper by Mathias N. Larrouturou on November 29th titled “Dynamic Soaring as a Means to Exceed the Solar Wind Speed.” Inspired by the dynamic soaring maneuvers performed by sea birds and gliders in which differences in wind speed are exploited to gain velocity, the paper proposes a technique involving lift-generating spacecraft circles between regions of the heliosphere that have different wind speeds, gaining energy in the process without the use of propellant and only modest onboard power requirements. This allows for the spacecraft to be accelerated to velocities greater than the flow velocity of ionized gasses in space.
The paper presents multiple models for this technique – the simplest being a series of elastic collisions. It formulates a conceptual mission in which dynamic soaring is performed on the termination shock of the heliosphere, enabling a spacecraft to reach speeds approaching 2% of c within two and a half years of launch without the expenditure of propellant. The technique may comprise the first stage for a multistage mission to achieve true interstellar flight to other solar systems. The full paper can be found here: https://arxiv.org/abs/2211.14643