Interstellar space exploration has long been the stuff of science fiction, a technological challenge that many engineers believe humans just aren’t up to yet. But an ongoing study by a group of NASA-affiliated researchers is challenging this assumption. The researchers have a vision for a mission that could be built with existing technology. Indeed, the group says that if their mission is selected by NASA it could fly as soon as 2030.
“This is humanity’s first explicit step into interstellar space,” says Pontus Brandt, a physicist at the Johns Hopkins Applied Physics Laboratory who is working on the interstellar probe study.
The lab kicked off its Interstellar Probe study last summer at the behest of NASA’s Heliophysics division. A year in, they are now hashing out the nitty-gritty engineering details of such a mission. At the end of 2021, Brandt and his colleagues will submit it for inclusion in the National Academies of Sciences, Engineering, and Medicine’s Heliophysics decadal survey, which determines sun-related mission priorities for the next 10 years.
The basic idea for the interstellar mission is to launch a spacecraft weighing less than 1,700 pounds on NASA’s massive Space Launch System rocket, which is expected to be ready by 2021. That will get it traveling across our solar system like any other probe. To give it another boost, it will then use a gravity assist to sling the craft to speeds well over 100,000 miles per hour. The team at the Applied Physics Lab is currently considering two types of gravity assists—a “plain vanilla” assist that swings the probe around Jupiter and another that swings it around the sun.
Using the sun is advantageous, because the spacecraft can reach far higher speeds than it can from a Jupiter assist. But the spacecraft would have to pass several times closer to the sun than the Parker Solar Probe, which recently became the closest human-made object to pass by the star. This requires some serious heat shielding, but at a certain point the heat shield becomes so bulky that it reduces the spacecraft’s speed the closer it gets to the sun. The task for Brandt and his colleagues will be to find the sweet spot that takes the craft to interstellar space as fast as possible.
“It’s time we have a vision we can actually execute,” says Ralph McNutt, a physicist at the Applied Physics Laboratory. “Up to now, people haven’t thought about this as an engineering problem. They kick the can down the road, saying, ‘Well, we just need a little bit more new technology.’”
NASA’s interstellar probe has a more modest goal compared to other interstellar mission proposals, like Breakthrough Starshot, which aims to send a thumbnail-sized craft to another star. Instead, NASA wants to launch a probe that will last for 50 years and travel 92 billion miles—about 1,000 times the distance from Earth to the sun. To put this in perspective, Voyager 1 and Voyager 2, the only spacecraft to make it to interstellar space, are currently around 13 billion miles away from Earth. It took those spacecraft nearly four decades to cover this distance, but NASA’s new interstellar probe could make it there in less than 15 years.
Voyager 1 entered interstellar space in 2012 and Voyager 2 left the solar system last year. They were designed to be planetary explorers, which meant they weren’t outfitted with many of the instruments physicists would need to get a deep understanding of interstellar space. While the two spacecraft have returned a wealth of data, their journey to the stars has raised far more questions than answers.
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