There is currently no clear launch date for the Europa Clipper mission, which will explore the intriguing moon orbiting Jupiter and ranks alongside the Cassini probe to Saturn as NASA’s most expensive and ambitious planetary science mission.
The $4.25 billion spacecraft was scheduled to launch in October on a Falcon Heavy rocket from the Kennedy Space Center in Florida, but NASA has revealed that the transistors on board the spacecraft may not be as radiation-resistant as previously thought.
“The transistor problem became apparent in May when the mission team received reports that a similar component was failing at lower than expected radiation levels,” the space agency wrote. In a blog post Thursday afternoon. “An industry alert was sent out in June 2024 to inform users of this issue. The manufacturer is working with the mission team to support ongoing radiation testing and analysis efforts to better understand the risks of using these parts on the Europa Clipper spacecraft.”
The moons orbiting the gas giant Jupiter reside in one of the most hostile radiation environments in the solar system. Initial NASA tests found that some of the transistors that control the flow of energy in the spacecraft could fail in this environment. NASA is currently evaluating possibilities for maximizing the transistors’ lifespan at Jupiter and expects to complete a preliminary analysis in late July.
To delay or not to delay
NASA’s latest update did not say whether Clipper would be able to make the roughly three-week launch window this year to reach the Jupiter system in 2030.
Ars contacted several experts on the Clipper mission to gauge their chances of meeting the October launch date, and opinions were divided: the consensus was that there’s a 40 to 60 percent chance of it making it for launch this fall. If NASA engineers aren’t confident in the existing setup, the transistors will need to be replaced.
The Clipper mission has launch opportunities in 2025 and 2026, which could cause further delays. This is because multiple gravity assists will be required. The 2024 launch will follow a “MEGA” orbit that includes a Mars flyby in 2025 and an Earth flyby (Mars-Earth gravity assist) later in 2026. A one-year delay to the Clipper launch would require a second Earth flyby. The 2026 launch would return to the MEGA orbit. Ars has asked NASA for the timeline for the 2025 and 2026 launches and will update as more information becomes available.
Another negative consequence of the delay is cost: keeping the mission on the ground for another year could cost NASA hundreds of millions of dollars more, blowing a hole in the planetary science budget.
This week’s blog post isn’t the first time NASA has publicly mentioned these issues with metal-oxide-semiconductor field-effect transistors (MOSFETs): At a Space Studies Board meeting in early June, Jordan Evans, project manager for the Europa Clipper mission, said it was their biggest concern ahead of launch.
“Why can’t I sleep at night?”
“The toughest problem we’re working on right now is one that has to do with transistors, MOSFETs, that are used as switches on spacecraft,” he said. “Five weeks ago today, I got an email saying that a customer outside of NASA had tested these radiation-hardened parts and found that they were operating ahead of specification, at radiation levels significantly lower than the radiation levels we certified them for when we sourced them, and others in the industry have done the same.”
At the time, Evans said that “things were moving in the right direction” when it came to NASA’s analysis of the issue. If the problem was still steadily moving toward resolution, NASA would not have posted the blog post five weeks later.
“What worries me right now is the uncertainty associated with the MOSFET and the residual risks that come with it,” Evans said in June. “It’s difficult to do low-dose-rate testing in the time frame we have until launch, so we’re trying to gather as much data as we can, including data from missions like Juno, to get a better understanding of what residual risks we might have at launch.”
These are exactly the kinds of problems scientists and engineers don’t want to find out in the final months before the launch of such a crucial mission. The risks are incredibly high: Imagine deciding to launch Clipper, only to have the spacecraft fail six years later when it reaches Jupiter.
