Currently, NASA is studying the concept of a Uranus orbiter and atmospheric probe as its next, big multibillion-dollar flagship mission. A SpaceX Falcon Heavy rocket would launch the mission in 2032 or 2033. It would use an Earth flyby and a Jupiter flyby gravity assist maneuver for an arrival in 2044 or 2045. While one part of the robotic probe would orbit the great ice giant planet, examining it and its moons and rings for several years, another would plunge into Uranus’ atmosphere to study its secrets. The Uranus Orbiter and Probe would do for the ice giant what Galileo did for Jupiter and Cassini did for Saturn.
NASA intends to start planning for a Uranus mission in 2023 or 2024, getting a handle on complexity and cost so that it can go to Congress for funding. While the space agency busies itself planning for the first visit to Uranus since the brief flyby conducted by Voyager 2, it should consider adding nuclear propulsion to hasten the voyage.
NASA has been working on nuclear propulsion technology for several years to use it to send humans to Mars as part of the Artemis program. Recently, the Defense Advanced Research Projects Agency (DARPA) started its own nuclear propulsion development project, planning a space-based test in 2026. Thus, if everything goes well, the technology should be ready for the Uranus mission six or so years later.
The main advantage of nuclear propulsion, whether the technology is nuclear thermal or nuclear electric, is that a spacecraft equipped with it would fly much faster to its destination.
A NASA study conducted in 1973 suggested that a robotic probe with a nuclear propulsion system would arrive at Uranus in seven to nine and a half years. Both launcher and nuclear propulsion technology have advanced in the past 50 years, so the trip time might take even less time.
As it is, a scientist participating in the Uranus Orbiter and Probe would likely spend his or her entire career supporting it, from the initial planning to the orbiting phase of the mission. If nuclear propulsion can cut a number of years from that time, even better. A shorter cruise to Uranus would save costs on a mission that is estimated to cost over $4 billion. Nuclear propulsion may be the future of exploration for the outer planets.
According to Space.com, one of the reasons for funding the Uranus Orbiter and Probe is that ice giants seem to be common in the galaxy. The mission would examine how such worlds are formed and evolve, relating Uranus to similar exo-planets.
Uranus is also unique for planets in the Solar System in that its equator is at a right angle to its orbit, possibly because it collided with another object eons ago. The tilt causes some of the most extreme seasons observed on a planetary body, with the sun shining over each pole for 21 years at a time while the other pole resides in darkness.
The 27 known moons of Uranus are the subject of much scientific curiosity. Some of them — such as Miranda, Ariel, Umbriel, Titania and Oberon — may be water worlds similar to Jupiter’s Europa and Saturn’s Enceladus. These moons might contain life in warm water oceans sealed under a layer of ice and rock. They don’t have impact craters, suggesting that their surfaces are geologically active, perhaps as a result of ice volcanoes.
Uranus also has two systems of rings, likely comprised of ice, dust and debris like Saturn’s rings. The Uranus Orbiter and Probe might be able to discover how they were formed.
In short, the study of Uranus and its system of moons and rings would occupy scientists for many years. The Uranus Orbiter and Probe will help to alter and deepen our understanding of the Solar System.
More broadly, a mission to Uranus, especially if it uses nuclear propulsion, will advance the technology of planetary exploration to the next level. Exploration of the outer planets requires crossing immense distances. Nuclear propulsion technology will enable future planetary probes to bridge the interplanetary gulfs faster than ever before and greatly benefit space exploration.
Mark R. Whittington is the author of space exploration studies “Why is It So Hard to Go Back to the Moon?” as well as “The Moon, Mars and Beyond,” and “Why is America Going Back to the Moon?” He blogs at Curmudgeons Corner.