If you imagined that capturing a cosmic speedster was as easy as aiming a rocket and blasting, forget it intercepting 3I/ATLAS, which is careening through the solar system at 58 kilometers per second, is a logistical and engineering nightmare of intergalactic proportions.
The arrival of 3I/ATLAS, the third interstellar object known after 1I/ʻOumuamua and 2I/Borisov, has set a whirl of calculations in the minds of mission planners and propulsion specialists. Found on 1 July 2025, by the Asteroid Terrestrial-Impact Last Alert Survey, this cometary visitor provides a brief window for in-situ investigation if only the orbital mechanics laws and the limitations of available technology allowed themselves to be warped a little more.
A recent Michigan State University study, “The Feasibility of a Spacecraft Flyby with the Third Interstellar Object 3I/ATLAS from Earth or Mars,” exposes the challenge. “A close flyby enables measurements that are not achievable from Earth-based telescopes,” study lead author Atsuhiro Yaginuma said. For example, we could obtain direct compositional and isotopic analysis of ices, dust, and organics in situ. We could also obtain high-resolution imaging of the nucleus and get key information regarding its shape, size, spin state, and active jets. All of these could yield critical insights into planetary formation and evolution and the delivery of volatiles and organics to potentially habitable planets in an alien system.
The delta-V challenge is the delta-V requirement major engineering challenge the velocity change to meet or intercept 3I/ATLAS’s hyperbolic trajectory. To leave Earth in the best window (January 2025 to March 2026), the delta-V needed is an astonishing 24 km/s.24 km/s. For perspective, the Dawn spacecraft, the most agile deep-space mission to date, mustered a post-launch delta-V of almost 23 km/s. Mars provides a unique respite, however. A launch from Mars early in October 2025, when 3I/ATLAS comes just 0.2 AU (29 million kilometers) away from the Red Planet, would cost only 5 km/s delta-V. The contrast is not negligible waiting even several months post-discovery greatly raises the energy budget, highlighting the value placed on discovery at an early date and swift mission turnaround.
Reusing available spacecraft has been at the center of the topical feasibility studies. Mars orbiters like NASA’s MAVEN, Odyssey, Mars Reconnaissance Orbiter, and ESA’s Trace Gas Orbiter and Mars Express are all on the job and, in theory, could employ their residual fuel to attempt a flyby trajectory. “A Mars-based intercept requiring a delta-V of 10 kilometers per second may be within current propulsion limits. In principle, these orbiters could use their remaining fuel to shift into a 3I/ATLAS flyby trajectory, turning their end-of-life maneuvers into a rare scientific opportunity,” Yaginuma explained.
The research also points out the Janus spacecraft, a duo of 36-kilogram SIMPLEx-class missions initially targeted for binary asteroid flybys but postponed following delays to their lead launches. “JANUS is one of the ready-to-launch spacecraft that was going to visit binary asteroids but recently was shelved. JANUS is also a small spacecraft and relatively light, so we might be able to get it to 3I/ATLAS if we went sooner rather than later,” Yaginuma clarified. Concurrently, OSIRIS-APEX, a reused asteroid sample return mission, might perform long-distance observations of 3I/ATLAS during its flyby gravity assist in late 2025 using its MapCam and PolyCam cameras.
Even if a spacecraft were to be repurposed, however, the technical hurdle of imaging something at speeds of more than 60 km/s during a flyby is significant. To put this into context, New Horizons’ groundbreaking Pluto flyby was at only 14 km/s. At such speeds, exposure times reduce to milliseconds, requiring sophisticated autonomous navigation and high-speed imaging technology. Research highlighted the necessity for onboard image processing and neural network guidance to ensure targeting accuracy in such high-speed encounter evaluations of optical and autonomous navigation performance.
Trajectory optimization is another essential aspect. Whereas the Oberth maneuver performing a propulsive burn at perihelion to maximize energy gain has been a theoretical favorite for decades, actual use is still beyond the reach of available materials and propulsion technology. After a very careful look and relying on the same people, including the mission system engineer, who worked the thermal protection system for Parker Solar Probe, we have concluded (1) the SOM offers no advantage over prograde gravity assists in rapid escape from the solar system for a ‘technology horizon’ in the 2030’s and (2) there is no obvious ‘path’ to changing this conclusion for the foreseeable future, wrote Ralph McNutt, project principal investigator of the Interstellar Probe project on Oberth maneuver limitations. Instead, gravity assists especially at Jupiter continue to be the most promising way of gaining outbound velocity, though even these are limited by planet alignments and mission schedules.
Propulsion technology stands at a juncture. Nuclear thermal propulsion, which some years ago was viewed as a game-changer for missions requiring high delta-V, has been recently derailed, with NASA and DARPA’s DRACO project being shelved over cost and risk issues. “As the launch costs came down, the efficiency gained from nuclear thermal propulsion relative to the massive R&D costs necessary to achieve that technology started to look like less and less of a positive ROI,” explained DARPA deputy director Rob McHenry on the death of DRACO. Nuclear electric propulsion, on the other hand, provides greater specific impulse but lesser thrust, perhaps better for missions where the need is for a prolonged acceleration over rapid, impulsive burning.
In the future, the Vera C. Rubin Observatory will make detecting interstellar objects a game-changer. Its 3.2-gigapixel LSST camera will survey the southern sky every few nights, with the potential to detect fast, faint objects such as 3I/ATLAS earlier and more often than ever Rubin’s contribution to ISO detection. Rubin will be looking constantly and broadly, giving astronomers the best chance yet to catch these fleeting visitors, while also being able to detect objects fainter than nearly any ground-based survey before it, says a recent analysis. Earlier detection directly means lower delta-V requirements and more viable mission architectures, turning the difference between a hypothetical exercise and a genuine mission.
Missions such as ESA’s Comet Interceptor, which will lie in wait at the Sun-Earth L2 point and pounce on the next interstellar passer-by, are in the future. “Once a suitable target is found, it (Comet Interceptor) will rendezvous and release two small probes to surround and study the comet from different angles at the same time,” Yaginuma said. But as the present study highlights, the race is not only against the stars, but against the clock and the boundaries of engineering.
