When you buy through links on our articles, Future and its syndication partners may earn a commission.Observations of Comet 3I/ATLAS taken using the Gemini South Observatory. | Credit: International Gemini Observatory/NOIRLab/NSF/AURA/Shadow the ScientistImage Processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab)Scientists think it’s possible for a spacecraft to gain enough velocity to catch up with iconic interstellar comet 3I/ATLAS, which is currently speeding away from us, by firing its booster rockets during a very close approach to the sun.If this mission could launch in 2035, the researchers say, it could at minimum catch up with 3I/ATLAS by 2085 at a distance of 732 astronomical units (AU) from the sun. In other words, that’s 732 times farther from the sun than Earth is, which is 68 billion miles (109 billion kilometers). For comparison, our most distant active space probe, Voyager 1, is currently only 170 AU from the sun after almost the same flight-time as the proposed mission to 3I/ATLAS.AdvertisementAdvertisementTo cross such huge distances so quickly, the mission would take advantage of something called the Oberth effect, named after the Austro–Hungarian rocket scientist Hermann Oberth (who later became a nationalized German and worked for the Nazis). Oberth first proposed the concept in 1929 in his book “Wege zur Raumschiffahrt” (meaning “Ways to Space Travel”).The idea is that as an orbiting spacecraft falls into a gravitational field produced by a planet or, in this case, the sun, the spacecraft accelerates. At periapsis – the spacecraft’s closest point to the gravitating body — it fires its engines to gain even greater velocity. The Oberth effect describes how doing this when at higher velocities produces a greater change in velocity — what rocket scientists refer to as “delta-V” – and the highest velocities attainable are at periapsis.”Pretty much every launch uses the Oberth effect,” T. Marshall Eubanks, a former NASA scientist who is now chief scientist at Space Initiatives Inc. and an author of a new paper describing this mission to 3I/ATLAS, told Space.com. “It’s why for example missions such as Artemis 2 do their translunar injection burns at perigee, not apogee. That’s an Oberth maneuver. However, I cannot find a record of a straight-out Oberth maneuver of the type we propose, which is a major rocket burn at closest approach in a flyby.”As the most massive body in the solar system, the sun is the best place to take advantage of the Oberth effect. But that means getting close — really close.AdvertisementAdvertisementTo achieve a delta-V of at least 5.1 miles (8.4 kilometers) per second, which you can think of as the work required to accelerate a spacecraft onto a new trajectory, the mission would have to perform a solar Oberth maneuver (SOM) at a distance of 3.2 solar radii from the center of the sun. The radius of the sun is 432,450 miles (696,000 kilometers).Three solar radii equals about 0.015 AU.Getting this close to the sun, which would be deep inside the solar corona, is not impossible. When NASA’s Parker Solar Probe made its closest approach to the sun in 2023, it came within 0.04AU (3.7 million miles/6.1 million km). Even though this isn’t quite as close to the sun as the proposed 3I/ATLAS interceptor would get, it gives an indication of what would be in store: Park …
