Between the orbits of the planets Mars and Jupiter lies the asteroid belt; a huge region of asteroids and minor planets presenting its own dangers to our star mission.
So not only do we have to set a collision course for Jupiter [previous post] but we have to navigate the equivalent of a solar minefield of objects ranging in size from 400 – 900 km diameter down to billions of dust sized objects. The largest object is Ceres, a dwarf planet at 950 km diameter, followed by Vesta, Pallas and Hygiea which are all in excess of 400 km.
But avoiding these is relatively simple due to their large size. It is the millions of smaller objects that pose the highest danger to our spacecraft. There are estimated to be around 1 million asteroids in the belt of diameter greater than 1 km. There are billions of smaller objects.
Furthermore the asteroid belt is the ‘birthplace’ of the many rogue asteroids which get flung out onto collision courses with other planets in the solar system including Earth.
Some we know about – eg the asteroid that passed between Earth and Moon [last post] and others take us completely by surprise as in Russia recently [last post]. The latter could be disastrous to a spacecraft travelling at 100,000 km/hour so we will have to develop very advanced detection systems by the end of this century to get us safely out of the solar system.
However, the asteroid belt is so thinly distributed that collisions would be highly unlikely. In fact many unmanned spacecraft have passed through it without incident. But it is a very different matter for a manned mission – we would have to be 100% certain of avoiding a collision as we travel 100 million km through the minefield. Further, collisions between asteroids occur frequently within the belt seeding rogue asteroids which could suddenly be on a course to damage our starship and terminate our mission before it leaves the solar system. Or worse, deflect our ship and crew directly into the gas giant Jupiter.
Even when we exit the asteroid belt there are further areas of asteroids called the Greeks, Trojans and Hildas to navigate but these are a much lesser threat to our mission.
So space is a dangerous place to travel through and we haven’t even left our solar system. To get beyond Jupiter is about 1 billion km and our star is 10 light years away – each light year is 10 trillion km so we have to travel 100 trillion km! We’ve barely covered 0.001% of the distance to our star. What else could go wrong?