I4iS October 2024 Newsletter

NASA Turns Off One of Voyager 2's Science Instruments

The two Voyager spacecrafts have been speeding through space since 1977, powered by decaying chunks of plutonium that produce less and less energy every year.

With less electricity available, NASA has decided to shut down one experiment on Voyager 2, the plasma science instrument, on 2 October 2024. This device measures the quantity and direction of ionized particles passing the spacecraft. While Voyager 2 still has enough electricity to support its four other operational instruments, it will likely be down to just one by the 2030s. NASA said that over the past several years, engineers for the mission have taken steps to avoid turning off any science instruments for as long as possible since the science data collected by the two Voyager probes is unique.

As the first spacecraft to reach interstellar space — the region outside the heliosphere – this is currently our only chance to study this region. However, this particular instrument has been collecting limited data in recent years due to its orientation relative to the direction that plasma is flowing in interstellar space.

More information can be found here: https://www.universetoday.com/168782/nasa-turns-off-one-of-voyager-2s-science-instruments.

Science Fiction vs. Technology

Giancarlo Genta published a paper in Acta Astronautica’s September issue titled “Interstellar exploration: From science fiction to actual technology.”

This paper explores the transition of interstellar exploration from science fiction to potential reality. It explains how technologies necessary for advanced solar system missions, such as nuclear fusion propulsion, are already being developed, but interstellar travel remains a distant challenge. The paper distinguishes between robotic missions that could be feasible within our current understanding of science, like nanoprobes traveling at a fraction of the speed of light, and human missions, which require significant advances in areas such as propulsion, life support, and artificial intelligence.

Genta categorizes various interstellar mission types, from robotic flybys to human space arks and hibernation missions, emphasizing that slow human missions may be achievable with future technological progress. However, faster-than-light (FTL) travel, which is popular in science fiction but requires breakthroughs in fundamental physics, remains an aspirational concept. The paper concludes that while slow interstellar travel may one day be possible, the feasibility of FTL travel and concepts like warp drives or wormholes is highly speculative and rooted more in fiction than current scientific reality.

The full paper can be found here: https://www.sciencedirect.com/science/article/pii/S0094576524003655

Developing Fission Rockets

Sandeep Puri et al released a preprint on 23 September 2024 titled “Progress in Fission Fragment Rocket Engine Development and Alpha Particle Detection in High Magnetic Fields” on Cornell’s preprint server ARXIV.

The authors detail their recent experiments on fission fragment rocket propulsion and an innovative new design for an alpha particle detection system inspired by these rocketry results. Their test platform, operating within strong magnetic fields of 3 T across a large cross-section (approximately 40 cm in diameter), has been used as a test bed to evaluate both containment and thrust in a future fission-fragment rocket engine (FFRE). This FFRE design, first proposed in the 1980s, was intended to significantly reduce transit times for long-duration space travel by providing a much more efficient nuclear rocket propulsion system.

The authors aim to enhance the operational efficiency of this nuclear propulsion concept while gaining deeper experimental insights into the behavior of fuel particles and fission-fragment ejecta within high magnetic fields. Through a combination of simulations and experimental work, they developed a method to produce and detect alpha particles, serving as surrogates for fission fragments. To accomplish this, Americium-241 sources were placed within a cylindrical vacuum chamber located inside a 3-T Siemens MRI superconducting magnet. By simulating, measuring, and analyzing the emitted alpha particle flux, they have obtained crucial data on the distribution and potential escape of fission fragments in future FFRE designs. This approach has the potential to achieve both high specific impulse and power density in advanced nuclear propulsion systems like the FFRE. More broadly, this work offers a robust new method for analyzing ion flux and nuclear reaction fragments across various experimental designs.

The full paper can be found here: https://arxiv.org/abs/2409.15206

Spacecraft designed for interstellar travel

On October 9, 2024, Leyan Ouyang published a paper titled “Spacecraft Design for Interstellar Travel,” which delves into the challenges and potential mechanisms required to develop a sustainable spacecraft capable of interstellar travel to the Andromeda galaxy. The paper’s central objective is to investigate the feasibility of scouting for habitable exoplanets suitable for human colonization, highlighting the urgency of identifying planets outside our solar system that could sustain human life. Ouyang’s design framework incorporates a comprehensive examination of critical technologies necessary for long-term space missions, including advanced propulsion systems like nuclear fusion or antimatter engines, attitude control mechanisms to stabilize the spacecraft across vast distances, and cutting-edge navigation systems designed to maintain precise trajectories over light-years of travel.

In addition to the engineering aspects, Ouyang explores astrobiological criteria for identifying potential homes for humanity. Special emphasis is placed on the search for habitable or Goldilocks zones, regions around stars where the conditions—such as the presence of liquid water—are optimal for supporting life. The paper underscores that liquid water is a fundamental prerequisite for life as we know it, with the ideal planetary temperature range playing a crucial role in determining whether a planet can maintain this critical resource. Ouyang’s final analysis reflects a broader vision, suggesting that space migration is not merely a distant possibility but an inevitable step in the survival of humanity.

The full paper can be found here: https://doi.org/10.54254/2753-8818/41/20240518

Updating the Frank Drake Equation

Elio Quiroga Rodríguez published a paper in the Journal of the British Interplanetary Society in October 2024 titled “Frank Drake is alive! (Rethinking the Drake equation for the search for biological life).”

Frank Drake's original Drake Equation has long been a cornerstone for scientific discussions on estimating the number of communicative extraterrestrial civilizations in the Milky Way. Often referred to as the "Classic Drake Equation," it identifies factors like the rate of star formation, the fraction of stars with planetary systems, and the probability that those systems contain planets capable of hosting intelligent life.

In his paper, Rodríguez proposes a streamlined version of the equation, focusing instead on the search for extraterrestrial non-intelligent life. He reexamines critical variables like the fraction of stars with planets, the number of planets that could support biological life, and the likelihood of life forming on such planets. Rodríguez also revisits less-discussed factors such as the survivability of biological signatures. He presents various scenarios that integrate our advancing technologies, specifically highlighting how future biosignature detection on exoplanets could transform our understanding of life beyond Earth, shifting the focus from intelligence to the potential for any form of life.

The preprint can be found here: https://www.researchgate.net/publication/384328976

Traversable Wormholes

On September 24, 2024, Peter K.F. Kuhfittig published a preprint titled “Macroscopic Traversable Wormholes: Minimum Requirements.”

Although wormholes are as valid a prediction of Einstein's theory of general relativity as black holes, they face significant limitations imposed by quantum field theory. For a macroscopic wormhole to enable interstellar travel, it must maintain low radial tidal forces to avoid the dangerous effect of "spaghettification," in which objects are stretched to extreme lengths. In his paper, Kuhfittig argues that assuming zero tidal forces—an idealized limiting case—could potentially circumvent these quantum restrictions.

He begins by reviewing the fundamental structure of Morris-Thorne wormholes, often discussed in theoretical physics as potential traversable wormholes. Kuhfittig then explores the additional conditions necessary to keep radial tidal forces sufficiently low, proposing that viewing traversable wormholes as emergent phenomena may increase the plausibility of their existence. Furthermore, he delves into the behavior of the redshift and shape functions, two crucial aspects of wormhole geometry, as they play a significant role in determining the wormhole's stability and traversability.

The full paper can be found here: https://arxiv.org/abs/2409.16184.

Propulsion 101

In October 2024, Samarth Mankan et al. published a preprint titled “Review on Past, Present, and Future Rocket Propulsion Technologies.”

As indicated by the title, the paper provides an extensive overview of rocket propulsion technologies, covering their historical development, current advancements, and future potential. The authors begin by charting the evolution of propulsion systems, from early innovations to the advanced technologies that power today’s aerospace achievements. Through a detailed examination of historical propulsion designs and the challenges faced by early rocket scientists, the paper sheds light on the pioneering technologies that have laid the groundwork for modern propulsion systems. This historical context emphasizes key lessons that remain relevant for driving future advancements.

Next, the review explores the propulsion technologies currently in use, providing an in-depth analysis of their design, applications, and limitations. Building on this foundation, the authors shift focus to emerging and future technologies that hold promise for revolutionizing space travel. Among these are innovative approaches like using atmospheric gases as reaction mass to address the mass constraints in traditional propulsion, as well as green oxidizers such as nitroform and FOX-7 to minimize environmental impact.

The paper also discusses more ambitious concepts, including antimatter annihilation rocket engines and faster-than-light travel via warp drives grounded in quantum field theory. Additionally, the authors explore the potential and challenges of Nuclear Thermal Propulsion (NTP) systems, gel propellants, pulse laser propulsion, and the formidable pursuit of gravity-controlled propulsion.

The full paper can be found here: https://www.researchgate.net/publication/384019582