Introduction to Article

A new study from researchers at EPFL argues that asteroid mining could become a practical way to support future colonies on Mars. Rather than launching every beam, tool, and replacement part from Earth at enormous cost, metallic asteroids rich in iron, nickel, and other useful materials could supply construction metals directly in space. Since transporting cargo from Earth to Mars is slow and expensive, developing off-world supply chains may be essential if any Martian settlement is to grow beyond a small outpost into a durable colony.

The study’s key insight is that some carbonaceous asteroids contain water and carbon compounds that could be processed into rocket propellant, allowing spacecraft to refuel in space rather than hauling all their fuel from Earth. By modeling thousands of route combinations, the researchers identified certain asteroids reachable with current or near-current technology where the energy costs are low enough to make missions plausible. The importance of the study is less that asteroid mining is imminent, and more that it shows the concept is technically solvable: a self-sustaining network where space resources help build infrastructure on Mars and reduce dependence on Earth.

Text From Original Article

I watched Armageddon again fairly recently with Bruce Willis, oil drillers in space and an asteroid the size of Texas bearing down on Earth. Buried beneath the Hollywood chaos is a genuinely interesting question, what exactly could we do with an asteroid if we got our hands on one? As it turns out, the answer has nothing to do with blowing it up, sorry Bruce but everything to do with building a new world.

Building a colony on Mars is not just an engineering problem, it’s a logistics one too. The logistics, unglamorous as it sound, may ultimately determine whether humanity becomes a multi planetary species or stays firmly rooted on Earth.

Think about what a Mars colony actually needs. Not just food and oxygen, but metal. Structural steel for habitats, aluminium for equipment, iron for tools and many of the components will wear out, break, and need replacing. Shipping all of that from Earth every time is not a serious long term strategy. A rocket launch costs tens of millions of pounds per tonne of cargo, and the journey to Mars takes between six and nine months depending on where the two planets happen to sit in their orbits. You cannot run a hardware store on that kind of supply chain.

A new study from researchers at EPFL in Switzerland has now done the hard maths on mining asteroids and delivering the metals directly to Mars. The Solar System contains millions of asteroids, and the metallic ones, known as M-type asteroids, are essentially giant lumps of iron, nickel, and other valuable materials floating through space. The question is whether we can actually reach them, extract what we need, and get it to Mars efficiently enough to make it worthwhile.

The answer, it turns out, is a careful yes but with conditions.

The team ran a computer program that tests thousands of different combinations to find the best possible answer across multiple supply chains. They took into account the energy required to travel between different asteroids and Mars, the mass of metals that could realistically be extracted, and crucially, the fuel needed for the return journey.

That last point is where a clever twist enters the picture. Some asteroids are carbonaceous, they are rich in carbon and water ice. Process those materials correctly and you can manufacture rocket propellant right there in space, eliminating the need to carry return fuel from Earth. The study builds this possibility directly into the supply chain calculations.

The results identify specific asteroids that sit within reach of current spacecraft technology, where the energy cost of getting there and back is low enough to make the mission viable. The team soon learned that selecting the right targets is everything. A poorly chosen asteroid could consume more fuel than the value of the metals it delivers.

What makes this study significant is not that it solves the problem because we are still a long way from the first asteroid mining operation. Instead it’s that it demonstrates the problem is 100% solvable. A supply chain delivering metals from space to Mars, fuelled by propellant manufactured on the asteroids themselves. The colony on Mars will need builders. It will also need someone to sort out the deliveries and this study shows it can be done.

Source : Asteroid Mining to Sustain a Mars Colony: A Logistics Point of View

Mining the Solar System to Build a New World
By Mark Thompson - April 26, 2026 09:56 PM UTC | Space Exploration
https://www.universetoday.com/articles/mining-the-solar-system-to-build-a-new-world

Summary of Research Paper Article is Based on

Mining the Solar System to Build a Mars Colony

The paper *Asteroid Mining to Sustain a Mars Colony: A Logistics Point of View* examines asteroid mining not as science fiction, but as a supply-chain problem. A permanent Mars colony would need more than air, water, food, and energy. It would also need metals for construction, repairs, tools, rovers, spare parts, and eventually habitats. Shipping all of that from Earth would make Mars permanently dependent on a slow and expensive supply line. The authors argue that if Mars is ever to become a lasting settlement rather than a fragile outpost, it will need access to industrial materials beyond what Earth can regularly send.

The study focuses on metallic asteroids as sources of iron, nickel, and other useful materials, while also considering carbonaceous asteroids as sources of water and carbon compounds that could be turned into rocket propellant. This is the clever part of the plan: the spacecraft would leave Low Mars Orbit, visit a metal-rich asteroid, mine useful material, then travel to a carbonaceous asteroid to refuel before returning to Mars. Without this refueling step, the round-trip energy cost is too high for spacecraft modeled on current technology. The researchers found 122 metallic asteroids that could be reached within the spacecraft’s velocity limits, but only 22 usable metallic-carbonaceous asteroid pairs once the full return-trip logistics were included.

The paper’s strength is that it treats asteroid mining as a practical routing and scheduling problem. The authors use multi-objective optimization to balance several competing goals: minimizing total velocity change, maximizing mined metal, and producing enough propellant for return trips. In the most realistic asteroid-only case, one spacecraft could visit two metallic-carbonaceous asteroid pairs over 20 years and deliver about 111 to 203 tons of metal, depending on mining rate. With many spacecraft, the amount grows dramatically, enough in their model to support construction of habitats, rovers, and repairs for a larger colony.

The conclusion is cautiously optimistic. From a logistics point of view, the plan is feasible, but only if mining and in-situ propellant production improve. Current propellant production rates are far too low; the study notes that hundreds of kilograms per day may be needed, while existing Mars-related estimates are closer to 2 kilograms per day. So the paper does not claim asteroid mining is ready now. Instead, it shows that the architecture is conceptually workable: Mars could be supplied by a space-based industrial network, with metal mined from asteroids and fuel made along the way. In that sense, the real story is not simply “mining asteroids,” but the beginning of an interplanetary economy where colonies survive by learning to use the Solar System itself as their supply chain.

—ChatGPT

Sections From the Original Paper

Abstract

Asteroid mining can become an enabling technology to establish a sustainable manned colony on Mars, which requires metallic materials more often than they are readily available in shipments from Earth. This paper describes a feasibility study of a supply chain that delivers metals extracted from metallic asteroids to Mars. The asteroids are selected to respect the Δ​V limits imposed by up-to-date spacecraft. The study is conducted with reference to the state of the art in space transportation technologies and in-situ resource utilization. A possibility for mining on carbonaceous asteroids to produce the propellant required for return trips is also taken into account. Different supply chains are computed through a multi-objective optimization routine that considers the mission Δ​V, the mass of extracted metals and the mass of propellant produced on the asteroids. Schedules to visit the asteroids within reach are obtained and the total mass of the delivered material is evaluated for various mining rates. Finally, the use of the metallic material to build habitats and rovers on the Martian soil through additive manufacturing is discussed.

1 Introduction

Since the 1960s, dozens of unmanned space missions, including orbiters, landers, and rovers have been sent to Mars to collect data and answer questions about the red planet. Nowadays leading space agencies are discussing designs of a manned mission. The Mars Exploration Program Analysis Group (MEPAG) [1] of the National Aeronautics and Space Administration (NASA) has established the scientific goals for Mars exploration for the coming years, one of such goals being preparation for human exploration. Systems engineering and design of a Mars Research Base is investigated by groups of researchers [2, 3]. Possibilities of either building an orbital station in Low Mars Orbit (LMO) as in M³ project [4], or sending humans to the Mars surface as in Mars Direct proposal [5] are seriously studied. The sustainable stepwise approach in preparation for human presence on Mars is presented in [6], starting from a crewed mission to Phobos in the mid-2030’s, proceeding towards short-term missions on Mars, and consummating with regular missions at a permanent Martian base in the 2040’s.

Sending a crew to the Martian soil has several important advantages. The human presence would allow rapid visual identification of the geological context, determination of the similarities and differences between the rocks, identification of samples of exceptional scientific value and adaptation of the analysis procedures of the samples collected with the use of the analysis results for the subsequent collection [7]. It is also possible to avoid the issues for the remote control of Mars rovers from Earth such as delays between the command order and its execution.

Given the travel time from Earth, a colonial settlement should be nearly self-sufficient for extended periods, especially for primary needs such as air, water, energy, and food. The long-term colony should also be able to replicate industrial activities on Earth. Most of the consumable resources must be produced and recycled. In addition to basic necessities, the colony must be able to make industrial products for construction and repair. In particular, the ability to manufacture metals is fundamental to any technological civilization. By far the most accessible industrial metal present on Mars is iron [8]. Some of the metals used on Earth for alloys, such as Molybdenum, are present in a smaller percentage on Mars and for others as Boron the percentage is unknown. Since the plan is to settle Mars, once the colony is established, an additional source of metals is needed to satisfy the demand. Metals are of extreme importance making it possible to construct or repair objects and rovers. Longer mission duration increases the probability of component failures, therefore, the spare parts required for confidence in system maintenance capability will occupy a significant portion of the overall system mass. In-situ manufacturing of spare parts has been proposed as a means to reduce this spares logistics mass [9, 10]. Additive manufacturing techniques are also discussed in this regard [10, 11].

We propose to consider asteroid mining as a supplementary source of resources required for the sustainable development of the Mars colony. In recent years, asteroid mining was much discussed, and asteroid mining has been proposed to complement Earth-based supplies of rare Earth metals and to supply resources in space, such as rare earth metals or water [12, 13]. Asteroid mining campaigns have been conceived and their logistics analyzed [14, 15, 16]. Availability of water-based propellants and metals for construction materials was discussed in [17, 18]. However. the economical practicality of asteroid mining ventures appeared to be debatable when considering end-users on Earth [19].

A preliminary study on supplying a base on Mars with resources extracted from Near Earth Asteroids (NEA) has been proposed by [20]. We shall take its point further and examine the possibility of designing a supply chain for sending spaceships out from Mars to mine on Near Earth or Main Belt Asteroids (MBA) and bring the extracted metals to Mars. Mars crossing asteroids are also included into the selection scheme. In addition to metal extraction from the so-called metallic asteroids, our study highlights the need to also visit carbonaceous asteroids and produce extra propellant needed for return trips.

Meteorites exploration indicates that small celestial bodies can be metal-rich [21]. General point of view to the origin of metal-rich asteroids is the formation of differentiated small planets with a metal-rich core, and following strip out of silicate crust/mantle by collisions with other small bodies [22]. However, new data collected in preparation of a mission to the largest M-asteroid (16) Psyche show a possibility of a complex mixed metal and silicate structure [23]. Hence caution is needed while one estimates metal content astronomical spectral data only [24, 25]. Metallic asteroids can be considered as a source of metallic iron-nickel alloys, ferrous sulphide minerals and olivine. Trace amounts of rare metals, such as Platinum group metals (PGM -ruthenium, rhodium, palladium, osmium, iridium, and platinum) can also be found. Carbonaceous asteroids can provide materials for in-situ propellant production (ISPP) due to their water content and potential for hydrocarbon production [26].

The aim of the research presented here is to design and optimize a single-product supply chain to sustain a Mars colony by mining asteroids for metals. The structure of the article is as follows. Section 2 describes the constituents of the proposed supply chain design such as spacecraft, chain-nodes and considered transfers. Section 3 outlines the asteroid selection routine which takes into account the required metallic asteroids and associates to them carbonaceous asteroids for multi-stage transfers. Section 4 analyzes different objective functions for the optimization problem and outlines the schedule optimization procedure. Section 5 presents the results for the optimized supply chain design and discusses how the materials brought to Mars can be put to use and lists key technologies required for the supply chain to operate. Finally, the last section concludes the paper.

2 Problem statement

The purpose of this article is to design and optimize a supply chain that delivers the metals extracted from metallic asteroids to Low Mars Orbit. This involves introduction of a fleet of cargo spacecraft, identification of the asteroids to travel to, and evaluation of a schedule for each cargo spacecraft, such that the delta-V is minimized and the mass of metals and propellant available are maximized. Such optimization problem formulation led us to use a multi-objective genetic algorithm [27]. Application of this algorithm to our problem as well as several objective functions we introduce and analyze are described in the following sections. Overview of the concept of operations is shown in Fig. 1, which introduces the following key points: Low Mars Orbit, where materials are delivered from asteroids; Transfer 1 trajectory is for mining an X-type asteroid; Transfer 2 trajectory is to approach and mine C-type asteroid and Transfer 3 trajectory is go back to LMO; Depot at Earth-Sun L2 point along with its natural use is also a benchmark to compare the obtained routs to the direct delivery from Earth.

Let us now introduce all the elements that comprise the tentative supply chain. It turns out that the key element in the logistics network is the cargo spacecraft, because it is the spacecraft’s characteristics that drive the architecture of the network nodes (inclusion of carbonaceous asteroids along with the metallic ones), and impose additional requirements to the transfers during one trip (multiple hops instead of simple Mars-asteroid-Mars transfer). Thus, we shall start from describing the spacecraft…

Full paper here;
https://arxiv.org/html/2604.18664v1

Possible Influences on Science & Technology

Mining the Solar System and the Future of Science

The article “Mining the Solar System to Build a New World” explores an idea that may become one of the defining technological shifts of the next century: using asteroids as industrial resources to support human expansion into space. Based on a recent study, the article argues that asteroid mining could supply metals to future colonies on Mars while carbon-rich asteroids could provide materials for rocket fuel. Rather than treating Mars as a distant outpost dependent on expensive shipments from Earth, the concept imagines a self-sustaining network of supply routes operating across the inner Solar System. If this becomes reality, it would change science and technology as profoundly as the steam engine changed Earth’s industrial age.

A New Era of Space Engineering

One of the most immediate influences would be the rise of advanced space engineering. Mining in microgravity would require robotics far beyond today’s industrial machines. Autonomous drilling systems, self-repairing equipment, AI-guided navigation, and remote manufacturing tools would all need rapid improvement. Machines operating on asteroids would have to function with minimal human supervision, long communication delays, and harsh radiation environments. Those same technologies would likely flow back to Earth, improving mining safety, disaster robotics, and automated construction.

The article also highlights the importance of additive manufacturing, or 3D printing, using asteroid metals on Mars. If engineers can turn raw extraterrestrial material into habitat walls, rover parts, or structural beams, it would revolutionize manufacturing. Instead of shipping finished goods, humanity would ship designs and software while producing materials locally. This shift from transport-heavy industry to knowledge-heavy industry could reshape economics both in space and on Earth.

A Scientific Explosion Across the Solar System

Asteroid mining would also accelerate pure science. To mine asteroids efficiently, researchers must understand their composition, internal structure, orbit dynamics, and history. That means more telescopes, more probe missions, and more sample-return missions. Every mining prospecting mission could double as a scientific expedition, expanding planetary geology and our understanding of how the Solar System formed.

Many asteroids are ancient remnants from the early Solar System, preserving materials older than Earth itself. Studying them could reveal how planets formed, how water and organic molecules were distributed, and perhaps how the ingredients for life reached Earth. In this sense, mining operations could fund discoveries that traditional science budgets alone might never support. Commercial motives and scientific curiosity may become partners rather than rivals.

Economic Independence Beyond Earth

The greatest long-term effect may be strategic independence for human settlements. Colonies on Mars cannot thrive if every broken machine, spare bolt, or metal beam must come from Earth months later. The article emphasizes that logistics, not just rockets, determine whether humanity becomes multi-planetary. If Mars can obtain metals from nearby space resources, then colonies become less fragile and more capable of growth.

This principle could later apply to lunar bases, orbital stations, and deep-space missions. Water mined from asteroids might become propellant depots. Metals might become space habitats. Entire supply chains could emerge beyond Earth’s gravity well, lowering the cost of exploration. The Solar System would begin to resemble an economic frontier rather than an empty void.

The Civilization-Level Meaning

Historically, civilizations expanded when transportation and resource access improved: rivers, oceans, railroads, and aviation each opened new eras. Asteroid mining could be the next version of that story. It would merge astronomy, engineering, robotics, materials science, AI, and economics into one grand project. Even if progress is slow, the direction matters.

The deeper meaning of the article is that humanity may be approaching the moment when space stops being merely a place to visit and starts becoming a place to build. If that transition happens, science and technology will no longer be confined to Earth. They will become Solar System sciences and Solar System industries.

—ChatGPT

Relevant Glossary of Areas Involved

1. In-Situ Resource Utilization (ISRU)

In-Situ Resource Utilization refers to using materials found at the destination rather than transporting everything from Earth. In space exploration, this can include extracting water ice, refining metals, making oxygen, or producing fuel from local resources. ISRU is considered one of the key strategies for reducing launch mass, cutting mission costs, and enabling long-duration human presence beyond Earth.

Asteroid mining depends heavily on ISRU. Metallic asteroids could provide iron and nickel for construction, while carbonaceous asteroids may supply water and carbon compounds for fuel production. On Mars, those same imported metals could be turned into habitats, tools, and replacement parts. Without ISRU, every kilogram would need to be launched from Earth, making large-scale settlement far less practical.

2. Additive Manufacturing

Additive manufacturing, often called 3D printing, creates objects layer by layer from raw material rather than cutting them from a larger block. It allows efficient use of resources, custom designs, rapid prototyping, and on-demand production. In remote or hostile environments, additive manufacturing is especially valuable because it reduces the need for large inventories of spare parts.

This technology is central to asteroid mining logistics. Instead of shipping finished machines from Earth, raw metal mined from asteroids could be refined and printed into rover parts, structural supports, tools, or habitat components on Mars. That turns mined material into immediate utility and greatly expands the value of every delivered ton.

3. Delta-v

Delta-v is the total change in velocity a spacecraft must achieve to complete a mission. It is one of the most important measures in astrodynamics because it determines fuel requirements and mission feasibility. Lower delta-v routes are generally cheaper and easier, while high delta-v missions require more propellant and more advanced vehicles.

The asteroid mining study is fundamentally a delta-v optimization problem. Researchers searched for asteroid targets reachable within current spacecraft limits and identified routes where mining, refueling, and returning to Mars were energetically realistic. Choosing the wrong asteroid could cost more fuel than the value of the cargo returned.

4. Carbonaceous Asteroids

Carbonaceous asteroids are dark, primitive bodies rich in carbon compounds, hydrated minerals, and in some cases water-bearing material. They are scientifically valuable because they preserve early Solar System chemistry and may resemble the building blocks that helped seed planets with organics and water.

In the Mars supply-chain concept, carbonaceous asteroids are not primarily mined for metals but for propellant ingredients. Water can be split into hydrogen and oxygen, while carbon compounds may support fuel synthesis. These asteroids function as space refueling stations that make round-trip mining missions possible.

5. Metallic Asteroids

Metallic asteroids are thought to contain large amounts of iron, nickel, and other metals, sometimes remnants of ancient protoplanet cores shattered by collisions. They are among the most attractive long-term mining targets because of their dense industrial materials.

These asteroids are the ore bodies of the proposed interplanetary economy. Their metals could be used to build habitats, machinery, radiation shielding, tools, and vehicles on Mars. Rather than hauling steel from Earth, future settlers might import raw asteroid metal from nearby space.

6. Autonomous Robotics

Autonomous robotics involves machines capable of sensing, navigating, and performing tasks with minimal direct human control. In dangerous or distant settings, autonomy becomes essential because human supervision is limited by time delays, risk, or cost.

Asteroid mining will require highly autonomous robots. Mining crews cannot constantly teleoperate machines across millions of miles with communication lag. Robots would need to drill, excavate, refine material, maintain equipment, and load cargo largely on their own, making robotics one of the enabling technologies of space industry.

7. Space Logistics

Space logistics is the planning and management of transporting people, fuel, cargo, and equipment through space. It includes launch windows, orbital transfers, storage depots, maintenance cycles, and supply reliability. As missions grow larger, logistics becomes as important as propulsion.

The article emphasizes that Mars colonization is not only an engineering challenge but a logistics challenge. A colony needs steady flows of material over years and decades. Asteroid mining transforms logistics by moving supply sources closer to Mars and reducing dependence on Earth-based shipments.

8. Radiation Shielding

Radiation shielding protects people and equipment from cosmic rays, solar particles, and other harmful space radiation. Outside Earth’s magnetic field and atmosphere, long-term exposure can damage electronics and increase health risks for astronauts.

Asteroid metals could help solve this problem. Dense materials are useful in shielding walls, underground structures, or layered habitat shells on Mars. Mining local or nearby metals may allow safer colonies without the enormous expense of launching heavy shielding materials from Earth.

9. Closed-Loop Sustainability

Closed-loop sustainability means recycling resources so that waste outputs become new inputs. In isolated environments, such as spacecraft or remote bases, systems must reuse water, air, materials, and energy efficiently to survive.

A Mars colony supplied partly by asteroid mining moves toward a broader closed-loop system. Earth would provide specialized goods, while metals and some fuel come from space resources, and Martian systems recycle water and materials internally. The result is a more resilient settlement less vulnerable to supply interruptions.

10. Interplanetary Economy

An interplanetary economy is a network of production, transport, trade, and infrastructure extending beyond Earth. Instead of a single planet exporting everything, multiple worlds and orbital locations would specialize in different resources and industries.

Asteroid mining is one of the first realistic foundations for such an economy. Asteroids hold raw materials, Mars offers settlement opportunities, and orbital space offers manufacturing advantages. Once resources can move profitably between locations, the Solar System begins shifting from exploration mode to economic development mode.

Ethical Questions in the Age of Asteroid Mining

If asteroid mining becomes practical, it will mark a turning point in human history. For the first time, industrial civilization would begin extracting large-scale resources beyond Earth. Supporters see abundance, cheaper space exploration, and the possibility of self-sustaining colonies on Mars or elsewhere. Yet every major technological expansion has also produced new moral problems. Just as the industrial revolution brought both prosperity and exploitation, asteroid mining could generate serious ethical challenges that must be considered before the first large-scale extraction begins.

One major issue is ownership and fairness. Who owns an asteroid? Is it the first company to arrive, the nation that licensed the mission, or humanity as a whole? Space treaties have generally treated outer space as a shared domain, but commercial laws in some countries already allow private claims over extracted resources. If a handful of wealthy corporations or powerful states gain control over the richest asteroids, the benefits of space resources may flow to a small elite while inequality on Earth deepens. The ethical question is whether space wealth should enrich a few pioneers or be structured to benefit all people.

Another concern is environmental responsibility beyond Earth. Asteroids may seem like lifeless rocks, but altering or moving them could create risks. Poorly managed operations might generate dangerous debris, destabilize orbits, or interfere with scientific missions. Some asteroids preserve ancient material from the birth of the Solar System and may hold enormous research value. Mining them recklessly could destroy irreplaceable natural archives before science fully studies them. Humanity already has a record of exploiting ecosystems before understanding them; repeating that pattern in space would be a moral failure.

Labor ethics may also emerge in unexpected ways. Early asteroid mining would rely heavily on automation, but human workers may still be involved in mission control, hazardous maintenance, or long-duration off-world labor. If workers are isolated in extreme environments with limited legal protections, abuses could develop. History shows that frontier industries often begin with weak oversight and harsh conditions. Ethical planning requires that space workers, whether on Mars, the Moon, or orbital stations, retain rights, medical care, fair compensation, and meaningful consent.

There is also the question of militarization and conflict. Valuable resources have often attracted rivalry on Earth. If strategic metals, fuel depots, or transport routes become economically critical, nations may compete aggressively to control them. Even if open warfare is avoided, political coercion or monopolistic behavior could emerge. Without clear international rules, asteroid mining could turn space into an arena of power struggles rather than cooperation.

A deeper philosophical issue concerns priorities. Should humanity invest vast sums in mining asteroids while poverty, disease, and environmental stress continue on Earth? Advocates argue that new technologies often create spillover benefits and long-term abundance. Critics may see off-world expansion as an escape project for the wealthy. The ethical challenge is not choosing Earth or space, but ensuring that progress in one realm supports justice in the other.

Asteroid mining may one day help build habitats, fuel missions, and expand civilization. But technological ability does not automatically create moral legitimacy. The future of space industry will depend not only on engineering success, but on whether humanity can carry fairness, restraint, and wisdom with it beyond Earth.

Conversations Elsewhere

Colonizing Mars Without an Orbital Economy Is Reckless
by u/Neat-Supermarket7504 in Futurology

Could light-Powered Spacecraft be Humanity’s Saviour?

Introduction

Iain Todd
https://www.skyatnightmagazine.com/news/light-powered-spaceflight

Published: April 25, 2026 at 9:00 pm

In about 5 billion years, the Sun will begin to die. As it does so, it will expand and likely swallow the inner planets of the Solar System, including Earth.

While that may not seem like an imminent problem, it does suggest that, should humanity still exist at that point, we probably don’t want to be anywhere near Earth.

More on interstellar spaceflight

• The science of faster-than-light travel

• Do wormholes really exist?

• Could a spinning spacecraft generate artifical gravity?

All of which adds a certain weight to the argument – made by some – that humanity must eventually become a space-faring species in order to survive.

But that means leaving our Solar System behind, travelling to a nearby star system with an Earth-like planet where we would be able survive.

Our nearest Earth-like planet is Proxima b.

However, in the field of exoplanet study – exoplanets being planets beyond our Solar System – the term ‘Earth-like’ is a very loose definition, and does not mean it’s confirmed as being suitable for humans to live on.

But even if we did want to travel at least to the Alpha Centauri star system, where Proxima b resides, the journey would take hundreds of thousands of years using current technology.

That would mean generations upon generations of human lifetimes, all lived out on board a rocket ship travelling across space, in the hope of a comfortable utopia waiting for us when we arrive.

Now, a team of researchers say they’ve demonstrated a form of light-driven propulsion that could one day get us to Alpha Centauri in 20 years.

Exploring light and laser travel

A team of researchers at the J. Mike Walker ’66 Department of Mechanical Engineering at Texas A&M University say they’ve demonstrated lasers can be used to lift and steer objects without physical contact.

Dr. Shoufeng Lan is an assistant professor and director of the Lab for Advanced Nanophotonics.

His team have published a paper called Optical propulsion and levitation of metajets, ‘metajets’ being micron-scale devices that generate motion when hit by laser light.

Patrick Moore’s Top 10 Winter Sky Wonders

0 of 58 seconds

The metajets, the team say, are made of ultrathin materials that are manufactured to have small patterns and can be used by scientists to control how light behaves.

They say that, by designing these structures in a certain way, they’ve been able to control how light transferred momentum to the object, making it move.

In other words, when light reflects, it transfers momentum, creating a small but measurable force that can push an object.

They team say the metajets can move objects in three dimensions and, according to them, it’s the first known demonstration of 3D-manoeuvring using this technique.

The study says the specific technique used here builds control directly into the material, allowing for more flexible generation of force and, according to the team, enabling the concept to eventually scale-up – potentially into a full spacecraft – more easily.

Currently the devices are smaller than the width of human hair but, say the team, the physics is sound.

The team tested the devices in a fluid environment to offset gravity and observe the motion more easily, potentially more closely mimicking how it could work beyond Earth’s gravity.

Following this intial study, the team say they’re attempting to acquire funding to extend testing into microgravity environments.

Looking further into the future, they say this technology could eventually lead to propulsion techniques that would use light to move and control objects as large as spacecraft, without the need for physical contact or fuel.

Read the full paper via Newton

Iain Todd is BBC Sky at Night Magazine’s Content Editor who has been writing about astronomy and space science for over a decade. He has covered major stargazing events, space launches and the latest news in cosmology, astrophysics, planetary and space science

Article Based on This Paper

Accessible overview

Metasurfaces are ultrathin and artificial materials that have revolutionized many fields, including optics and photonics, by engineering constituent structures. This structural engineering has been widely studied to tailor all aspects of light, such as amplitude, phase, frequency, and polarization. In a reverse manner, their mechanical responses due to the control of light, particularly in momentum change associated with anomalous deflection, are less explored. From Newton’s law of motion, any momentum change between the input and output light at an interface can generate a compensating mechanical reaction force on the interface itself. Despite its fundamental nature, a general relationship between anomalous deflection and the resulting optical force has been missing. Building on generalized Snell’s law and momentum conservation, we develop a theoretical framework that connects the momentum change induced by metasurfaces with force generation. The generated forces are not only lateral but also vertical, enabling full three-dimensional (3D) optical control. We term these controllable forces metaphotonic forces, since they arise directly from engineered momentum transfer from the metasurface. To experimentally demonstrate this concept, we fabricate micron-scale metajets composed of silicon nanopillar arrays designed to impose a distributed phase gradient. When illuminated by a normally incident beam, these free-standing devices simultaneously translate laterally and lift vertically, enabling 3D motion not accessible with conventional optical manipulation methods. Our experimental measurements confirm the predicted dependence of propulsion and levitation on metasurface design parameters, including refraction efficiency, refraction angle, and phase gradient ratio. Importantly, the metaphotonic forces scale with optical power and are not fundamentally constrained by device size, suggesting opportunities to extend this approach from microscale applications, such as microrobots, to large settings, including interstellar light sails for space travel.

Highlights

• Shaping light’s wavevector for precise control over the force exerted on metajets

• Theoretical framework of force generation in metasurfaces validated by experiments

• Both anomalous refraction and reflection can generate 3D force for manipulation

• Force is scalable with increased light power for applications like light sails

Summary

The quintessential hallmark distinguishing metasurfaces from traditional optical components is engineering materials and structures to manipulate light at will. Enabling this engineering freedom, in a reverse manner, to control the motion of objects constituted by metasurfaces could extend our capability of optical manipulation at different scales. Here, we introduce generalized optical manipulation by recapitulating metasurfaces as engineered interfaces with anomalous reflection and refraction. Upon combining Newton’s law of motion and generalized Snell’s law, we find that three-dimensional motions would be possible by inducing an extra wavevector component. As an example, we achieve this condition through a spatially distributed phase gradient using purposely arranged silicon nanopillars. Our experiments and simulations simultaneously reveal an in-plane propulsion and out-of-plane levitation of metasurfaces not seen in other optical manipulations. The optical force scales with incident power and is not fundamentally dependent on the size of the metajet, suggesting opportunities to scale this concept toward large-area applications such as interstellar light sails.

Graphical abstract

Keywords

1. metasurfaces

2. optical manipulation

3. metaphotonic forces

4. optical propulsion

5. optical levitation

Introduction

Optical forces generated from electromagnetic wave manipulation offer a versatile and contactless means of moving objects, crucial for applications in biology, physics, and chemistry.^1,2,3,4,5 Optical manipulation became possible with the development of laser technology that facilitates photon-to-matter momentum transfer to induce optical forces.⁶ Historically, the optical forces comprise gradient and scattering forces, with each type contributing uniquely to manipulating microscopic and sub-microscopic objects in various optical fields.^7,8,9,10,11 While gradient forces arise from light-intensity gradients, drawing objects toward regions of high intensity, scattering forces propel objects along the direction of light, which results from the scattering of objects.^12,13 Recent investigations have markedly advanced the field of optical force by controlling metasurfaces to mainly induce anomalous refraction in dimerized and asymmetric nanoantenna arrays,¹⁴ rotating nano-bar metasurfaces with spin-torque interactions,¹⁵ and spatially arranged plasmonic nanostructures.^16,17,18 These fascinating works focused on the output refraction, demonstrating in-plane motions of metasurfaces that rely on the fact that metasurfaces can introduce an in-plane optical momentum. Tightly focused Gaussian beams are known to produce self-stabilizing behavior through intensity-gradient forces, though this mechanism is constrained by its strong dependence on the beam’s spatial profile.¹⁹ A separate out-of-plane levitation of metasurfaces is also possible but only through optical reflection, again, mainly focusing on the output light.^20,21,22

In a broader perspective, metasurfaces are engineered interfaces that require consideration of both input and output light.^{23,24,25,26,27,28} As an example, we utilize a standard metasurface with a phase gradient (dϕ/dx) along the interface to refract and reflect light in a specific direction.^29,30 The wave’s refraction and reflection manifest in the generalized Snell’s law that elegantly traces optical wavevectors.³¹Because the wavevectors represent momentum in geometric optics, we can understand the generalized Snell’s law in terms of momentum. According to Newton’s law of motion, only the change of momentum between input and output light at the metasurface can generate an optical force, termed the metaphotonic force. Under this framework, we can develop (see methods section) an in-plane metaphotonic force, 𝐹x=−𝜂⁢𝑝⁢𝜆02⁢𝜋⁢𝑐⁢𝑑⁢𝜙𝑑⁢𝑥, where η represents the output efficiency, p the incident power, and the negative sign follows our sign convention for output light, indicating that the in-plane force acts in a direction opposite to the increasing phase gradient. Besides this in-plane force that applies to anomalous refraction and reflection, we find an out-of-plane force (F_z) that differs between them. We obtain 𝐹z=𝑛⁢𝑝𝑐⁢(1∓𝜂⁢cos⁡𝜃), in which, 𝜃=arcsin⁡(𝜆02⁢𝑛⁢𝜋⁢𝑑⁢𝜙𝑑⁢𝑥), while – and + are for anomalous refraction and reflection, respectively.

Results (see paper)

Discussion

In this work, we observed simultaneously an in-plane propulsion and out-of-plane levitation of structured metajets constituted by a standard metasurface with a spatially distributed phase gradient. Both propulsion and levitation are controllable through varying the phase gradient. Our circular-pillar metasurfaces generate only propagation-phase gradient delays and therefore avoid the angular dependence and optical torque associated with anisotropic or rotated meta-atoms. Combined with linearly polarized illumination and careful beam centering, the phase-gradient force acts through the center of mass, and we observe no measurable rotational motion in our recordings. More importantly, we leverage metasurfaces to a general structured interface and develop a basic model for generating metaphotonic forces with reflection and refraction by combining Newton’s law of motion and Snell’s law. This generalized model can not only apply to the exemplified standard metasurfaces with phase gradients but also to other sophisticated structures, such as Huygens metasurfaces and dimerized particle arrays. Meanwhile, our model shows that the metaphotonic force augments with increased optical power while having no limitations on the overall size of structured objects. Therefore, metaphotonic forces may extend optical manipulation from the predominant microscopic and sub-microscopic scales to large settings, such as interstellar light sails in space travel and exploration.^{32,33,34,35,36}

Methods (see paper)

How a Billionaire’s Plan to Reach Another Star Fell Apart

An abandoned plan to visit another star highlights the perils of billionaire-funded science

BY SARAH SCOLES EDITED BY CLARA MOSKOWITZ

Eddie Guy

In 2016 billionaire Yuri Milner hosted a press conference at One World Observatory, the atrium topping the slick skyscraper at the center of the rebuilt World Trade Center complex. Milner had grown rich investing in tech start-ups, and now he wanted to spend some of that money on sending a spaceship to the stars.

He called the plan Breakthrough Starshot: a project that would eventually take human technology to another solar system. The idea was that high-powered lasers would propel tiny probes to 20 percent of the speed of light, impelling them with enough inertia to launch them toward the nearest star system, Alpha Centauri, within 20 years. Milner and his Breakthrough Initiatives, a group of space science research projects related to life in the universe, were pledging $100 million toward a proof of concept. At the event, Milner was joined by, among others, Mae Jemison, a former astronaut and head of 100 Year Starship, an interstellar research program funded by the Defense Advanced Research Projects Agency; Pete Worden, former director of NASA’s Ames Research Center; and Stephen Hawking, world-famous physicist.

Zachary Manchester, currently an associate professor of robotics at Carnegie Mellon University, signed on for the project’s early stages. He remembers it seeming incredible that he, then a wide-eyed 20-something, was at the top of a metropolis, hanging out with people he considered legends—people such as Freeman Dyson, a physicist best known for positing that advanced civilizations could eventually cloak their stars in megastructures that siphoned their power. Dyson was one of several scientific luminaries who were joining the project, including Nobel Prize winner Saul Perlmutter and Martin Rees, then the U.K.’s Astronomer Royal.

In short, the Starshot launch event was flashy. A video preview narrated by actor Seth MacFarlane was also flashy. The text that went along with the announcement? Flashy. “With current rocket propulsion technology, it would take tens or hundreds of millennia to reach our neighboring star system, Alpha Centauri,” it read. “The stars, it seems, have set strict bounds on human destiny. Until now.”

Milner’s money wasn’t quite an Apollo-project investment, but it was more than anyone had ever dedicated to interstellar travel, a field with a history of relatively little funding and a trail of projects that never reached the stars. In the 2010s DARPA and NASA founded the 100 Year Starship research program to figure out how to send humans light-years away in the next 100 years. Private research groups such as the Tau Zero Foundation and Project Icarus also launched initiatives. None of them have come to much. Maybe this time the goal was within reach. After all, besides the money itself, the big names attached to Breakthrough Starshot gave legitimacy to an endeavor that might otherwise have seemed fringe. The announcement made a splash in the press, including a cover story in this magazine.

But almost a decade later Breakthrough Starshot is conspicuously quiet. After the initial big bang the project seemed to whimper out. Now there are no more big announcements, no multi-institution meetings and no more funding. What remains is confusion among even scientists working on Breakthrough Starshot about the project’s status. According to an e-mail from Worden, Starshot’s executive director, who declined an interview for this article, “We have put the program on hold and are working to transition portions to others.”

The Breakthrough Starshot announcement even in April 2016 included, from left, documentary writer and producer Ann Druyan, Zachary Manchester, Yuri Milner, Stephen Hawking, Freeman Dyson, Mae Jemison, Pete Worden, Avi Loeb and Philip Lubin.

Between 2016 and today scientists and engineers on the project did make progress toward the stars—or at least toward understanding what it would take to make progress toward the stars. But engineering an interstellar journey is almost ludicrously difficult. With today’s rocket technology, it would take thousands of years to get to the nearest star. Processes and components need to be invented, iterated on and vetted, at great expense, most likely over decades. Sure, “$100 million sounds like a lot of money,” says Edwin Turner, an emeritus astrophysicist at Princeton University and one of the first people to be involved in Breakthrough Starshot. “It’s certainly more than pocket change for most of us, but it’s not really very much for huge technological programs.”

The total doled out, according to one insider, was far below $100 million anyway. The fact that most of the money never seems to have materialized means the case of Breakthrough Starshot isn’t necessarily one of waste. But it’s a study in the perils of relying on the ultrarich to fund science: when the guy with the billions is ready to move on, the whole project is off.

Breakthrough Starshot is based on a simple but technologically audacious concept: build a powerful set of lasers on Earth, and use them to propel “lightsails” on tiny spacecraft weighing about as much as a paperclip. A traditional rocket would carry the craft to space; once it was some 37,000 miles from Earth, the lasers would light up, shooting 100 gigawatts of power at the lightsails. Their combined photons would slam into the sails, powering them forward like wind on a sailboat. Ten minutes later the spacecraft would be zooming at 20 percent of light speed and already halfway to Mars—a journey that takes months with current technology. At that rate it would hit Alpha Centauri—specifically, Proxima Centauri, the closest star in the system—in a couple of decades. During its flyby Starshot would glimpse both the star and the Earth-size exoplanet known to exist in the star system. The craft would send a signal back to Earth before sailing on toward the rest of the Milky Way.

The basic idea of using light for propulsion dates to the 1920s, when Russian scientists Friedrich Zander and Konstantin Tsiolkovsky, pioneers of rocketry, proposed using the pressure of sunlight to push a vehicle through space. Some details of Breakthrough’s specific plans, however, came from the work of a University of California, Santa Barbara, physicist named Philip Lubin. Back in 2009, seven years before Breakthrough Starshot began, Lubin attended a conference at the Naval Postgraduate School in Monterey, Calif. There researchers were discussing focused energy in the form of lasers, microwaves, particle beams, and more, known as directed energy, “mostly for purposes of taking down threats,” Lubin says, meaning incoming missiles.

But as Lubin sat at the conference, he began to dream about other uses for the technology, especially if it were scaled up. Could it be used to protect Earth from asteroids rather than from intercontinental ballistic missiles? Or, he thought later, to propel a spacecraft far, far away? At home Lubin started crunching numbers. “I always want to figure out why it won’t work, why you cannot do this,” he says.

Despite his best efforts to defeat himself, it seemed the idea would work: You could direct energy at an incoming space rock, heat a portion of it up, vaporize that spot and shift the asteroid’s orbit just enough to curve it away from Earth. And you could probably also send a spaceship on a significant journey. Lubin eventually applied for and received NASA funds to research both plans.

After the explosion of a meteor over the Russian city of Chelyabinsk in 2013, Lubin’s planetary-protection work—under the project name DE-STAR—got more attention. Lubin, perhaps a future savior of the planet, was invited to give talks to other scientists, including one at the SETI (Search for Extraterrestrial Intelligence) Institute. There he mentioned that this same technology could also enable interstellar flight. A colleague told him he should talk to a guy named Pete Worden.

Lubin didn’t, but he did keep working on his interstellar laser ideas with continued money from NASA. In 2015 he spoke at a conference hosted by the 100 Year Starship project. There he finally met Worden, who suggested Lubin send over a written version of his ideas. Lubin responded with a roadmap for interstellar flight, later published in the Journal of the British Interplanetary Society.

Worden wrote Lubin back quickly. “I have a friend,” Lubin recalls him saying. “You mind if I send it to my friend?” Lubin told him sure, send it to whomever you want. The friend, of course, was Milner, and by January 2016 Lubin was meeting with Milner at his Bay Area mansion. In front of Milner was Lubin’s interstellar roadmap, bedazzled with yellow Post-it notes. “Yuri says to me, ‘You know, I’ve always dreamed, since I was a child, of going to the stars,’” Lubin recalls. “‘And now you’ve shown me the path.’”

Milner wanted to send the paper to experts who could evaluate its strengths and flaws. “If the reviews come back positive, then I’m willing to put in a fair amount of money,” Lubin recalls Milner saying. He mentioned $100 million. “Unfortunately that, by the way, never came true,” Lubin says. “There was no $100 million.” The top two scientists affiliated with the project declined to be interviewed for this story.

Before officially announcing Starshot, Breakthrough officials had quietly recruited other thinkers in the field. In addition to Turner, who already knew Milner through a separate project called Breakthrough Listen, which searches for signals from alien civilizations, there was Mason Peck, an engineering professor at Cornell University and previously NASA’s chief technologist. “That kind of opportunity does not come along every day, and I was all in from the very beginning,” Peck says. Kelvin Long, a physicist and aerospace engineer who co-founded Project Icarus, also hopped onboard early. He sent Worden a design study, which he had written in three days while stuck in travel, for a hypothetical space probe that could move at 10 percent of the speed of light.

At Starshot’s founding, the group identified around 30 problems to be solved before anyone could send an interstellar probe anywhere. Worden and James Schalkwyk of the Breakthrough Prize Foundation, working with three researchers from the Australian National University, wrote a chapter providing an overview of the project’s initial phases for physicist and editor Claude Phipps’s 2024 book Laser Propulsion in Space: Fundamentals, Technology, and Future Missions. Thirty-seven research groups, according to that summary, convened to understand and reduce the technology risks in those major areas. “Then the whole project came down to trying to figure out how to spend $100 million productively,” Turner says.

Sometimes members of the crew got a bit of money to support their research, sometimes not. Starshot did bring people together, though—in person and virtually—to talk about their personal research on those problems. “Breakthrough is essentially a set of meetings,” Lubin says. Other sources also cited meetings as a primary way scientists participated in the project.

Beginning in 2016, the Breakthrough Initiatives sponsored Breakthrough Discuss meetings “focused on life in the Universe and novel ideas for space exploration.” The meetings, which were never specific to Starshot but did frequently cover topics related to the interstellar mission, have continued through 2025, with a gap in 2020 and a virtual meeting in 2021. Smaller satellite meetings also convened over the years to discuss specific technological and scientific aspects of the problem.

The Breakthrough Starshot spacecraft would probably be a small computer chip called a nanocraft. The prototype shown here is about 15 millimeters wide.

Stan Musilek

While they lasted, the meetings brought scientists and engineers together to investigate where the technology stood, what problems they didn’t have solutions to, how feasible it was to overcome those problems and build something launchable, and what timelines and costs doing so would entail. There was palpable excitement in the early years—scientists felt they were part of a team embarking on an ambitious but tractable undertaking. They knew their biggest challenges were in certain areas: the design of the sail, the functionality of the laser system, the makeup of the spacecraft, and the construction of a communications apparatus that could signal back to Earth from light-years away. So, essentially, the whole system.

It’s hardly worth sending a ship to another star if you won’t be able to prove you’ve done it. Starshot would need to not just reach Proxima Centauri but also find a way to send back a signal strong enough to be detectable on Earth. It’s a considerable challenge, however, to point a signal in the right direction from light-years away when both the probe and Earth are moving. Plus, both those feats must be accomplished with diminutive instruments on a spacecraft the mass of a pen cap or two.

According to Peck, Milner might have had unrealistic ideas—or at least ideas that conflicted with some of the scientists’ suggestions—about what those signals should be like. “I do think Yuri Milner is very intelligent,” Peck says. “I do think he has an adequate technical background” for the project. But he wanted things like video or 4K images from Alpha Centauri. And that, in Peck’s view, was putting the cart before the horse, to make an ancient analogy for a 21st-century endeavor.

To Peck, getting just one computer bit of information from another solar system would be valuable. Perhaps the probe could send a yes-or-no answer to a single question—is there a certain percentage of oxygen in the planet’s atmosphere, for instance, or does the radiation environment seem suitable for life? “It’s only incrementally better to get a gigabit from Proxima Centauri,” he says.

According to the 2024 book chapter, the team found several ways to make comms somewhat feasible. The scientists could build a huge array of smaller receivers on the Earth end to catch weak transmissions. They also could enlarge the spacecrafts’ transmitting antenna and send communications in optical instead of radio wavelengths, which can transfer more data faster. The team decided to use the sun as a beacon to point the homebound transmission toward, helping the information reach the right part of the vast universe. Still, Long calls the communications problem the “elephant in the room” in that it didn’t get as much attention in initial research as other topics did—an assessment Carnegie Mellon’s Manchester agrees with.

Propelling the probes far enough and fast enough that they have something to communicate requires solving another problem: the lasers. Or, as the Starshot team called them, “the photon engine.”

The first issue, the team found, was that a single laser would need to be impractically powerful—incomparable to anything that exists today. The researchers could create an array of smaller lasers whose beams would combine into one with 100 gigawatts of power, but then they’d need to ensure the light waves lined up with one another, like sound waves that are in tune. “People made serious progress on that,” Manchester says. “They were able to do it with tens of lasers in the lab, which is a breakthrough.”

There was palpable excitement in the early years—scientists felt they were part of a team embarking on an ambitious but tractable undertaking.

But not quite enough of a breakthrough for Breakthrough. The project would need even more lasers, and those lasers would have to work outside the lab to reach deep into space—which poses another problem. “How do you get that out of the atmosphere without getting messed up?” Manchester asks. Turbulence in the upper air will cause the beam to twinkle.

They would need to adjust for that twinkling in real time. One laser, called a guide star, could shoot through the atmosphere constantly, and the scientists could use data about how it got distorted to correct the other lasers. But that correction would require millions of adjustments every second. In the 2024 book chapter, Worden and his co-authors pegged it as potentially the largest technical hurdle for the entire program.

The lasers pose a financial hurdle, too. To make Starshot feasible, the cost of powering them must come down from the current price of $100 per watt to around $0.01 to $0.05 per watt, according to Long. Peck is optimistic because, theoretically, the cost of laser power should decrease over time, similar to how Moore’s law predicted that transistors in computer chips should get steadily smaller as the years passed. Still, that discount isn’t instantaneous. “We were likely looking at a launch date not in the next 20 years, as the sponsor had hoped, but perhaps in 30 or 40 years,” Long says.

Regardless of how much the laser costs, what form it takes or when any of this finally happens, policy is an issue. A laser that blasts out the equivalent of four power stations’ worth of energy is, as the conference that spurred Lubin’s original research interest demonstrates, a weapon. The only solutions for that problem are international cooperation and trust, which aren’t at all-time highs right now.

Once the photon engine is up and working, that laser energy has to hit the lightsail of a given spacecraft and propel it forward with a power of about 100 gigawatts. The sail must hold up to the onslaught while withstanding acceleration at a g-force of 40,000—that is, 40,000 times the pull of gravity you would feel if you fell off a cliff.

Substances that can withstand both the rigors of warp speed and the shock of a laser-cannon blast and remain reflective tend to be heavy. Starshot envisioned a lightsail material that can stretch four meters wide but weigh only a gram. The initial Breakthrough phase aimed to identify potential materials and designs, a process led by Harry Atwater of the California Institute of Technology, who did not respond to a request for an interview. The leading candidate substance his team found, according to the 2024 summary, is silicon nitride. Atwater and his colleagues published that result in 2022. Engineers have been able to fabricate it at submicron thicknesses—less than one-tenth the thickness of Saran Wrap.

Ultrathin wafers of the material can be puzzle-pieced together into a larger structure that is mostly reflective and doesn’t absorb much light. Breakthrough engineers have done this assembly on the millimeter scale but not the meter scale. Atwater and his team also coded a computer simulation that could figure out how various lightsail designs would perform during interstellar flight.

Another group, based at the University of Sydney, worked on ways to keep the hypothetical lightsail stable. The researchers joined meetings in 2021 and 2022 and shared their findings, but they never received any money from Breakthrough. “The whole thing always was outrageous,” University of Sydney physicist Michael Wheatland says of the project’s ambition. “I never believed it. But I think my perspective on things like this is that if you do fundamental research to try to solve a problem in the context of some outrageous scheme like that, then you can do really useful research.”

And that’s what the Sydney team did. They knew the sail would constantly be pushed around by the laser beam as it accelerated, so the team had to find some way to push it back to center. “But that then gives you oscillations,” Wheatland says. Moving the laser could account for that, but like with the correction to untwinkle the lasers, the movement may be too much to ask of a bunch of lasers.

When the project started, people thought interstellar travel was crazy—or they didn’t think about it at all.

The sails are a separate problem from the spacecraft itself, which must be as small and lightweight as possible. Breakthrough calls the tiny spaceships “nanocraft.” The leading candidate is the brainchild of Manchester, that wide-eyed graduate student when the program began. Manchester’s early creations weren’t meant for voyaging beyond the solar system—or even beyond Earth’s orbit. As a graduate student at Cornell, working under Peck, he started designing postage-stamp-sized satellites around 2009. He called them, variously, Sprites and ChipSats. In 2011 he crowdfunded the project, and in 2014 he launched around 100 ChipSats to space. A glitch prevented them from deploying, though, and they burned up on the way back through the atmosphere.

After that disappointment, Manchester became involved with Breakthrough. His tiny satellites seemed like just what the team was looking for. “The notional idea was that some version of my ChipSat would end up being attached to that lightsail,” he says. Manchester went on to do his postdoc at Harvard University, working officially on non-ChipSat projects. But with Breakthrough’s help he was able to keep the ChipSat project on life support. “They were super nice to me during all of that,” he says. “They would help me out, and they gave me little bits of funding.”

In 2019 Manchester was able to go for launch again, successfully deploying 105 ChipSats at once. He showed they could communicate with one another in space, acting as a swarm. The federal government let him fly them only once. “Then the [Federal Communications Commission] decided that we were going to destroy the world with space debris,” he says—which wouldn’t be a problem if they were headed way beyond low Earth orbit, to infinity and beyond.

Breakthrough hasn’t gone beyond anywhere, of course. Still, in all four problem areas, the teams found that nothing was technically wrong with the basic plan. They also did enough research to find out what they didn’t know and what kinds of technical development (and money) would be required to make the concept reality.

Progress was almost certainly slowed by the fact that the $100 million never materialized. Although the Starshot grants weren’t made public, Lubin’s experience might illustrate the scale of the spending. His group got two grants, one for $116,000 and another for about $80,000. Some of his colleagues in Australia also got $80,000. “We got less than $200,000 spread out over eight years,” Lubin says. That was much less than NASA put toward Lubin’s directed-energy interstellar work, although Breakthrough’s press-centric approach meant its name was better associated with the project. “Breakthrough contributed less than 5 percent of the funding in our program in the end,” Lubin says. “So it was always a little blip along the way. But in the public mind the entire program was a Breakthrough program, and that is simply not true at all.”

The closest star system to the sun, Alpha Centauri, includes three stars. Two of them are a binary pair, seen in this close-up from NASA’s Chandra X-ray Observatory (inset). A third star, Proxima Centauri, orbits the central two.

Zdenek Bardon (optical); NASA/CXC/University of Colorado/T. Ayres et al. (x-ray)

Lubin calculates that overall, Breakthrough spent roughly $4.5 million on about 30 contracts. In late January 2025, after I contacted Worden and Avi Loeb of Harvard, also a Breakthrough scientist, a spokesperson for the Breakthrough Prize Foundation reached out. Worden and Loeb had declined interviews, but the spokesperson said, “I have a potential way to move your story significantly forward.” She later referred to a report on the project that would be finished around spring 2025 and made available to Scientific American, but that report had not appeared by the time this issue went to print.

At this stage the future of the program is murky. Starshot appears to be on indefinite hold, if not over, although there was no final announcement and no fanfare to match its beginnings. Peck is not sure where things stand. “As far as I can tell, they’ve put it on pause, at least,” he says. “And I think it’s probably not going to continue for the near future.”

Physicist Martijn de Sterke, part of the Sydney group, and his colleague Boris Kuhlmey, a Sydney physicist who’s helping with Starship-related research, heard only informally that Breakthrough Starshot was done. “It appears that this project has kind of disappeared,” de Sterke says. “We have not heard from them for probably two years.”

Some sources have interpreted the program’s end as a realization that an actual starship, though technically possible, is still distant. “I think it’s going to take 30 to 50 years of very hard work by a large number of very dedicated people, much like a Manhattan Project on steroids,” Lubin says. Maybe that timeline wasn’t appealing to Milner, some sources speculate, and neither was spending a Manhattan Project amount of money. Turner has a different perspective on how things turned out. To explain, he turns to the familiar example of medieval cathedrals, which took centuries to build—a length of time that humans rarely dedicate to any single project these days. “That [comparison] is often made as a kind of snide criticism of the short-sightedness of modern civilizations or people or profit motives,” Turner says. “But I think it’s actually a result of how fast technology is moving.”

The innovations behind a cathedral’s arches and finials didn’t change much over the 200-year course of its construction. But the technology undergirding our world is unrecognizable compared with that of just a couple of decades ago. “It’s very hard trying to imagine a major technological thing we’re working on now for which they could have done anything at all useful 200 years ago,” Turner says. “Nothing they could have done would make the slightest difference to us.” Maybe that’s what Breakthrough leadership decided about Starshot: it’s best left to the people of tomorrow.

Despite the project’s nebulous end and uncertain future, many participants spoke about Breakthrough positively. Manchester, for instance, sees it as at least a psychological success. When the project started, people thought interstellar travel was crazy—or they didn’t think about it at all. “Breakthrough changed society’s conception of this kind of stuff as a legitimate area of scientific inquiry,” he says.

Serious people worked on the project, did serious things, made serious progress—even if not directly on a path toward Alpha Centauri. “It’s still a long way off, but it’s a lot closer than it was five or six years ago,” Manchester concludes. The program also inspired people such as de Sterke and Kuhlmey to work on fundamental physics and engineering problems that might not have gotten attention otherwise. And maybe, at the end of the day, that will be Starshot’s legacy. “If there was a one-sentence summary of what Breakthrough was and did,” Lubin says, “it was to bring attention to the dream.”

https://www.popularmechanics.com/space/rockets/a63374262/electron-beam-rocket/