Achieving interstellar travel has been the dream of countless generations, but the challenges remain monumental. Aside from the vast distances involved, there are also the prohibitive energy requirements and the sheer cost of assembling spacecraft that could survive the trip. Right now, the best bet for achieving an interstellar mission within a reasonable timeframe (i.e., a single person’s lifetime) is to build gram-scale spacecraft paired with lightsails. Using high-power laser arrays, these spacecraft could be accelerated to a fraction of the speed of light (relativistic speeds) and reach nearby stars in a few decades.
There are a handful of major projects, like Breakthrough Starshot, that hope to leverage this technology to create spacecraft that could reach Alpha Centauri in a few decades (instead of centuries). This technology also presents other opportunities, like facilitating communications across interstellar distances. This is the idea recently by a team of researchers led by the Initiative for Interstellar Studies (i4is). In a recent paper, they recommended that a swarm of gram-scale spacecraft could rely on their launch laser to maintain optical communications with Earth.
Between the exponential growth of the commercial space industry (aka. NewSpace) and missions planned for the Moon in this decade, it’s generally agreed that we are living in the “Space Age 2.0.” Even more ambitious are the proposals to send crewed missions to Mars in the next decade, which would see astronauts traveling beyond the Earth-Moon system for the first time. The challenge this represents has inspired many innovative new ideas for spacecraft, life-support systems, and propulsion.
In particular, missions planners and engineers are investigating Directed Energy (DE) propulsion, where laser arrays are used to accelerate light sails to relativistic speeds (a fraction of the speed of light). In a recent study, a team from UCLA explained how a fleet of tiny probes with light sails could be used to explore the Solar System. These probes would rely on a low-power laser array, thereby being more cost-effective than similar concepts but would be much faster than conventional rockets.
In the 1960s, American physicist Robert W. Bussard proposed a radical idea for interstellar travel: a spacecraft that relied on powerful magnetic fields to harvest hydrogen directly from the interstellar medium. The high speed of this “ramjet” forces the hydrogen into a progressively constricted magnetic field until fusion occurs. The magnetic field then directs the resulting energy towards the rear of the spacecraft to generate propulsion.
As it’s come to be known, the Bussard Ramjet has since been popularized by hard science fiction writers like Poul Anderson, Larry Niven, Vernor Vinge, and science communicators like Carl Sagan. Unfortunately, a team of physicists recently analyzed the concept in more detail and concluded that Bussard’s idea is not practical. At a time when interstellar travel looks destined to become a real possibility, this analysis might seem like a wet blanket but is more of a reality check.
In just a few years, astronauts will walk on the surface of the Moon for the first time since the Apollo Era. In addition to the Artemis Program, NASA’s fabled return to the Moon, there are also a number of planned missions involving the European Space Agency (ESA), JAXA, China, and Russia. By the 2030s, NASA and China hope to send crewed missions to Mars, which will culminate in the creation of a permanent base on the surface.
When it comes to interstellar missions, however, there are no plans for crewed missions on the table. While there are proposals for sending robotic missions, sending astronauts to nearby stars and exoplanets simply isn’t feasible yet. However, according to new research led by the University of California, interstellar missions could be conducted in the near future that would have tardigrades (aka. “Water Bears”) as their crew.
In October 19th, 2017, the first interstellar object ever detected flew past Earth on its way out of the Solar System. Less than two years later, a second object was detected, an easily-identified interstellar comet designated as 2I/Borisov. The appearance of these two objects verified earlier theoretical work that concluded that interstellar objects (ISOs) regularly enter our Solar System.
The question of how often this happens has been the subject of considerable research since then. According to a new study led by researchers from the Initiative for Interstellar Studies (i4is), roughly 7 ISOs enter our Solar System every year and follow predictable orbits while they are here. This research could allow us to send a spacecraft to rendezvous with one of these objects in the near future.
On July 14th, 2015, theNew Horizons mission made history when it became the first robotic spacecraft to conduct a flyby of Pluto. On December 31st, 2018, it made history again by being the first spacecraft to rendezvous with a Kuiper Belt Object (KBO) – Ultima Thule (2014 MU69). In addition, the Voyager 2probe recently joined its sister probe (Voyager 1) in interstellar space.
Given these accomplishments, it is understandable that proposals for interstellar missions are once again being considered. But what would such a mission entail, and is it even worth it? Kelvin F. Long, the co-founder of the Initiative for Interstellar Studies (i4iS) and a major proponent of interstellar flight, recently published a paper that supports the idea of sending robotic missions to nearby star systems to conduct in-situ reconnaissance.
The dream of traveling to another star system, and maybe even finding populated worlds there, is one that has preoccupied humanity for many generations. But it was not until the era of space exploration that scientists have been able to investigate various methods for making an interstellar journey. While many theoretical designs have been proposed over the years, a lot of attention lately has been focused on laser-propelled interstellar probes.
The first conceptual design study, known as Project Dragonfly was hosted by the Initiative for Interstellar Studies (i4iS) in 2013. The concept called for the use of lasers to accelerate a light sail and spacecraft to 5% the speed of light, thus reaching Alpha Centauri in about a century. In a recent paper, one of the teams that took part in the design competition assessed the feasibility of their proposal for a lightsail and magnetic sail.