Can We Fly to Planet 9?

TL;DR

This paper explores various space mission architectures to reach Planet 9, comparing chemical propulsion, nuclear thermal propulsion, and laser sails, highlighting the potential for significantly reduced travel times with advanced propulsion methods.

Contribution

It presents detailed mission designs and performance estimates for reaching Planet 9 using both conventional and advanced propulsion technologies.

Findings

Chemical propulsion takes 45-75 years to reach Planet 9.

Nuclear thermal propulsion reduces travel time to about 40 years.

Laser sails could potentially reach Planet 9 in as little as 7 years.

Abstract

Planet 9 is an hypothetical object in the outer Solar system, which is as yet undiscovered. It has been speculated that it may be a terrestrial planet or gas/ice giant, or perhaps even a primordial black hole (or dark matter condensate). State-of-the-art models indicate that the semimajor axis of Planet 9 is $\sim 400$ AU. If the location of Planet 9 were to be confirmed and pinpointed in the future, this object constitutes an interesting target for a future space mission to characterize it further. In this paper, we describe various mission architectures for reaching Planet 9 based on a combination of chemical propulsion and flyby maneuvers, as well as more advanced options (with a $\sim 100$ kg spacecraft payload) such as nuclear thermal propulsion (NTP) and laser sails. The ensuing mission duration for solid chemical propellant ranges from 45 years to 75 years, depending on the distance from the Sun for the Solar Oberth maneuver. NTP can achieve flight times of about 40 years with only a Jupiter Oberth maneuver whereas, in contrast, laser sails might engender timescales as little as 7 years. We conclude that Planet 9 is close to the transition point where chemical propulsion approaches its performance limits, and alternative advanced propulsion systems (e.g., NTP and laser sails) apparently become more attractive.