In the 1980 film Star Wars: The Empire Strikes Back, Han Solo and friends try to escape pursuing imperial forces by flying through an asteroid field. Droid C-3PO remarks, “the odds of successfully navigating an asteroid field is approximately 3,720 to 1”.
The scene depicts a chaotic, dense field of rocks swirling and spinning through space. This scenario has been played out many times in the cinema.
But the reality is very different, at least for the asteroid belt in our Solar System. Based on our knowledge of the volume of the asteroid belt, and an estimate of the number (and size) of asteroids, astronomers think that the average distance between asteroids is almost 1 million kilometres.
So, the gaps between asteroids are vast enough that it’s an easy task to navigate between them.
In fact, a number of space probes have already done it. NASA’s Pioneer 10 was the first. On 15 July 1972, the car-sized probe first encountered the asteroid belt, beginning a seven-month, 434-million-km (267-million-mile) curve through the main belt.
Although, at the time, mission planners didn’t know the density of the asteroid belt very accurately, their hunch proved correct, and the probe passed through unscathed.
Since then, eight other probes have been shot through the asteroid belt; Pioneer 11, Voyager 1, Voyager 2, Ulysses, Galileo, Cassini, New Horizons and Juno. None of them flew a course deliberately to avoid asteroids and none of them had any unwelcome encounters.
In other star systems things could be different; asteroids could be more tightly packed. Such asteroid systems wouldn’t survive very long after forming, however, as their components would be constantly colliding and breaking apart.
So, the typical sci-fi scenario of a dense swarm of fast-moving rocks is almost certainly not found in nature.
This article is an answer to the question (asked by Suzanne Baxter, Cornwall) 'How difficult would it be to fly through the asteroid belt?'
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