97 — Project Lyra: Sending a Spacecraft to 1I/’Oumuamua (former A/2017 U1), the Interstellar Asteroid

Note [June 27, 2018]: Recent evidence suggests that ‘Oumumamua is actually a comet and not an asteroid as previously thought.

Asteroid ‘Oumuamua is the first interstellar object to be seen passing through our Solar System, and it was spotted this past October. It is traveling fast enough to exceed the sun’s escape velocity, and so while it recently described a partial orbit around the sun, it will never again come this close, leaving the solar system in about 20,000 years.

This type of object is what astronomers usually call “pretty awesome,” and there are an abundance of reasons why we humans would want to interrogate this asteroid more. What is its chemical makeup? Where did it come from? What is its favorite color?

The authors of this “Project Lyra” paper explain that it is feasible to both reach as well as intercept these types of fast-moving interstellar objects — if indeed we ever spot another — and it is possible, but very difficult, to reach ‘Oumuamua itself.

Project Lyra, so named because ‘Oumuamua was first seen near the Lyra constellation, aims to intercept and learn about the asteroid using a high-speed unmanned spacecraft.

The project, the authors explain, would stretch the limits of space exploration technology due to the high speeds required to reach the asteroid: Voyager 1, our fastest-traveling space probe, moved just over ~16km/s. ‘Oumuamua’s intercept probe would need to move at ~26km/s.

The figure I found hardest to follow in this paper also wound up being my favorite (I did some searching and realized this type of figure is common in space-launch literature, so… Good job everyone!) — Figure 2 on page 3 shows the a 3D plot of launch date (x) against mission duration (y), with a colorbar of $C_3$, the characteristic energy — a measure of the launch energy required to perform that mission. The vertical stripes indicate that there is an annual, periodic “easy mode” launch, and an annual window of extreme high difficulty; the launch energy naturally increases with the passing of time.

This paper demonstrates that it would be possible to reach ‘Oumuamua if we devoted immense resources to the operation — but for now, we may have to satisfy ourselves with a more remote inspection of 1I/’Oumuamua.