In October 2017, the interstellar object ‘Oumuamua passed through our Solar System, leaving a lot of questions in its wake. Not only was it the first object of its kind ever to be observed, but the limited data astronomers obtained as it shot out of our Solar System left them all scratching their heads. Even today, almost five years after this interstellar visitor made its flyby, scientists are still uncertain about its true nature and origins. In the end, the only way to get some real answers from ‘Oumuamua is to catch up with it.

Interestingly enough, there are many proposals on the table for missions that could do just that. Consider Project Lyra, a proposal by the Institute for Interstellar Studies (i4is) that would rely on advanced propulsions technology to rendezvous with interstellar objects (ISOs) and study them. According to their latest study, if their mission concept launched in 2028 and performed a complex Jupiter Oberth Manoeuvre (JOM), it would be able to catch up to ‘Oumuamua in 26 years.

On October 30th, 2017, less than two weeks after ‘Oumuamua was detected, the Initiative for Interstellar Studies (i4is) inaugurated Project Lyra. The purpose of this concept study was to determine if a mission to rendezvous with ‘Oumuamua was feasible using current or near-term technologies. Since then, the i4is team has conducted studies that considered catching up with the ISO using nuclear-thermal propulsion (NTP) and a laser sailcraft, similar to Breakthrough Starshot – an interstellar mission concept for reaching Alpha Centauri in 20 years.

As they describe in their study, most of the previously proposed methods for reaching 1I/’Oumuamua using near-term technologies call for a Solar Oberth Manoeuvre (SOM). A perfect example is the “Sundiver,” a proposal made by researcher Coryn Bailer-Jones of the Max Planck Institute for Astronomy (MPIA). As he described to Universe Today in a previous article, this concept relies on the Sun’s radiation pressure to obtain a very high velocity with a light sail.

“The principle of the Oberth effect is to apply your boost when you are moving fastest relative to the body you are orbiting, which is the Sun in the case of the Sundiver,” he said. “The closer you are to the Sun in your orbit, the faster you will be. So to take advantage of the Oberth effect, you need to get as close to the Sun as possible.”

At the heart of the SOM and other Oberth maneuvers is a technique known as a Gravity Assist, which has been used to explore the Solar System since the early 1970s. This technique involves using the gravitational force of three bodies, including the spacecraft, a second body that provides the “assist” (typically a large planet), and the central body about which the spacecraft’s path is being controlled.

Adam Hibberd, a researcher with the i4is, was the lead author of this latest Lyra study (titled “Project Lyra: A Mission to 1I/’Oumuamua without Solar Oberth Manoeuvre.”) Before joining i4is, Hibberd was an aerospace engineer who developed the Optimum Interplanetary Trajectory Software (OITS). When ‘Oumuamua was detected, he decided to use OITS with this ISO as the intended destination. After finding out about Project Lyra, he joined them and their research efforts shortly afterward.

Artist’s impression of the Project Lyra lightsail probe rendezvousing with an interstellar object (ISO). Credit: i4is

As he explained to Universe Today via email, the Solar Oberth Maneuver (SOM) relies on three discrete changes in velocity (aka. impulses) to exit the Solar System. These include:

At Earth, to increase the spacecraft’s fathest distance from the Sun (aphelion), At aphelion, to slow down and fall in close to the Sun,At the closest point to the Sun (perihelion) when the spacecraft is travelling at it fastest to get an extra boost

“This 3-impulse scenario was discovered by Theodore Edelbaum in 1959, although the term SOM seems to have stuck. It is fuel-optimal for generating high speeds out of the solar system. This is precisely what is needed to catch an ISO when the ISO has passed perihelion and is receding quickly from the sun.”

“However, this theoretical setup disregards Jupiter. Thus as a
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