The ice giants remain some of the most interesting places to explore in the solar system. Uranus in particular has drawn a lot of interest lately, especially after the 2022 Decadal Survey from the National Academies named it as the highest priority destination. But as of now, we still don’t have a fully fleshed out and planned mission ready to go for the multiple launch windows in the 2030s. That might actually be an advantage, though, as a new system coming online might change the overall mission design fundamentally. Starship recently continued its recent string of successful tests, and a new paper presented at the IEEE Aerospace Conference by researchers at MIT looked at how this new, much more capable launch system, could impact the development of the Uranus Orbiter and Probe (UOP) that the Decadal Survey suggested.
Uranus is one of the least explored planets – the last probe to visit it was Voyager 2 during a flyby 40 years ago. Neither it, nor its ice giant cousin Neptune, have ever had an orbiter visit it, nor any consistent mission presence in their system, marking them out as the only two planets that haven’t been studied in detail up close so far.
That’s not for lack of interest. Uranus has a lot of strange things about it that closer study could help explain. It’s lying on its side, has a rather wonky magnetic field, and has a bunch of moons that could potentially hide oceans under their icy surfaces. What’s more, planets like Uranus are some of the most common exoplanets that we’ve found so far in the solar system, so studying the system up close would also improve our understanding of those other worlds as well.
Fraser discusses the difficulties in planning a mission to Uranus.
The problem is that Uranus is far away. It’s 19 times farther from the Sun than Earth is, and it took Voyager more than nine and a half years to reach the system, and that probe didn’t even attempt to slow down to stay in it. Previous calculations done during the decadal survey used a Falcon Heavy booster and several gravitational assists from other planets, but ultimately took over 13 years to reach Uranus. That’s time the mission has to be maintained, both operationally and financially, and also time that critical personnel might move on, or, if recent NASA history is any guide, furloughed. So getting UOP to its final destination faster is inarguably better.
Enter Starship. Despite a series of testing mishaps earlier in the year, SpaceX’s game-changing rocket system is finally coming into its own with a successful test earlier this week. Assuming it continues its positive trajectory, it could be ready for regular use by the end of the decade, making it a viable option for use as UOP’s launch vehicle.
In addition to its increased lifting capability, two other aspects of Starship’s capabilities make it interesting for a UOP mission. First is its ability to refuel in orbit. SpaceX has made sure to design the system so that it can store and take fuel in orbit, allowing it to reach destinations much faster than other systems, whose fuels has to be lifted exclusively from the ground. While this capability hasn’t been demonstrated yet, further tests of Starship will undoubtedly begin to do so, unlocking whole new speed possibilities for probes to the furthest reaches of the solar system.
Fraser discusses the Decadal Survey suggestions, including UOP.
The other capability is to use Starship itself as an aerobraking shield. In the paper, the researchers examined the idea of using Starship, which itself is already designed to deal with the heat of reentry on both Earth and Mars, as a shield against the heat caused by aerobraking in Uranus’ atmosphere. They found that, with a little modification, the basic principle could work. Instead of separating from the probe once its boost was provided, in this case the Starship would accompany UOP to the Uranus system, using its thermal protective system as an air brake to slow the probe down from its interplanetary speed and remain in the system.
From calculations in the paper, the combination of being refueled in space and also using Starship as an aerobrake could cut the time to the Uranus system in half, to six and a half years. It also wouldn’t require any gravitational assists from any other planets on the way. Even with the added cost of taking a Starship along for the ride, this would dramatically decrease the operational cost of the mission by literally halving its travel time.
With all that being said, UOP is still a far way from reality, nor is Starship ready for aerobraking a probe into an ice giant’s atmosphere yet. Despite being the highest priority to come out of the decadal survey, it’s unclear whether UOP will even get a funding green light at this point, and given the current turmoil and NASA it will likely remain unclear for some time. If we miss the launch windows in the 2030s, the next opportune launch window would be the mid-2040s, meaning it would be almost 70 years between missions to this most interesting of worlds. All planetary science and space exploration enthusiasts should hope that the organizations that would potentially support such a mission get their act together and support a trip back there, whether it uses Starship or not.
Learn More:
MIT – 3 Questions: How a new mission to Uranus could be just around the corner
D. Gochenaur, C. Gentgen, O. de Weck – Starship as an Enabling Option for a Uranus Flagship Mission
UT – How To Aerobrake a Mission To Uranus On the Cheap
UT – A Mission to Uranus Could Also be a Gravitational Wave Detector