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?                                         

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Let us assume that our artificial intelligence [AI] computer has completed building our starship in Mars orbit in 2150. It is capable of half-light speed and housing a crew of seven astronauts in cryo-hibernation for at least 20 years.

Its journey to a star 10 light years away will be full of dangers but most will occur whilst it is traversing our solar system at relatively low speeds. Space is not as empty as it seems. We have already filled the upper atmosphere of Earth with tens of thousands of pieces of space junk and any one of these could cause disaster to Earth based missions.

Our solar system is crammed with objects, many of which we know about but even we can be taken completely by surprise – witness the events in Russia recently when a small meteor exploded above ground. In February an asteroid the size of an Olympic swimming pool passed between Earth and the Moon’s orbit and even inside the thousands of communications satellites in space. But we knew this was coming and that it posed no danger.

So we have to be prepared for every eventuality when we finally leave Mars orbit. But our biggest threat is about to happen. We have to set a collision course for Jupiter! – the largest planet in our solar system.


Jupiter is the fifth planet from the sun and is a gas giant with a mass two and half times the mass of all the other planets in the solar system combined. It is nearly 320 times the mass of Earth and that is why our starship is hurtling towards it a velocity of 100,000 km/hour [estimate of future capability].

But Jupiter’s orbital velocity is about 50,000 km/hour and it is charging directly towards our starship – the combined relative velocity is 150,000 km/hour. But this is deliberate as we are about to perform a common manoeuvre in space called the slingshot. We’ve been doing this since the early 70’s eg the Voyager missions and it is done to accelerate and redirect our craft onto its desired trajectory in space.

In essence we use the huge gravitational force of Jupiter to capture our spaceship and send it around the planet and sling it in the opposite direction of travel. In so doing its velocity increases significantly according to a simple equation [Wikipedia]. Our starship would double its velocity to 200,000 km/hour but we are going to fire advanced rockets at a critical point as we pass around Jupiter and this will accelerate us to 1 million km/hour.

It sounds simple but there are huge dangers if we miscalculate our speed and trajectory as we approach Jupiter – get it fractionally out and we will bounce off the gravitational field of the planet onto the wrong course or worse we will be dragged inexorably towards the surface of Jupiter. Further the timing of the firing of the rockets is equally critical to achieving the optimum boost to the slingshot. Finally we must remember that our starship will weigh about 200,000 tonnes. That’s an awful lot of momentum if we get anything wrong.

And, of course, a crew of astronauts who will be totally reliant on the AI computer systems getting everything perfectly right as we swing around Jupiter in the first critical stage of accelerating towards half-light speed. But this slingshot is only the first of the dangers – more in the next post.

Meanwhile perhaps you would like to join the crew of Lifeseeker-1 as she is flung around Jupiter in 2150 at the start of a 20 year journey to the star Seren.                                                


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