Size and Scale in Space

Rescue missions in space are very different to Earth. Knowing how size and scale in space is like can help you design for this successfully.

by Neelesh Ravichandran, UKSDC Design & Publications Committee Chair

Where is everything?

Space is a vast expanse filled, mostly, with nothing at all. The diagram on the right of this article shows to scale: the Earth, the Moon and the distance between them.  Unlike in the movies where astronauts travel between planets in minutes, real space travel is a little bit slower than that.

The Apollo 11 mission to land on the Moon took three days to travel from its launch pad here on earth, to touch down on the surface of our moon. For those three days, the brave astronauts had to rely on their spaceship for all their needs. This ranged from food to sanitation, and really pushed the limits of 1960s technology.

How far are things from each other?

As we can already see, the moon is very far away from the Earth (384 thousand kilometres away to be exact). However, the distances to other planets are truly astronomical. In fact, the average distance between Earth and Mars is 362 million kilometres, which is a thousand times further than the Moon.

Everything in between Earth and Mars is just empty space, with the occasional asteroid floating through. Our Apollo crew would take a whole year to get from Earth to Mars, and that’s if they get lucky with the time of year that they launch from.

How long does space travel take?

Well it really depends on where you need to get to. If you’re designing a rescue craft that is meant to save people all across the solar system, you are going to need to design it to be lived in for years on end.

Some journeys can be made faster with advanced thruster technologies, that can make the spacecraft reach their destinations faster. Be careful though, the more powerful your thrusters the larger your fuel tanks need to be. This means to reach far away destinations quickly, your rescue craft will have to be equipped with powerful thrusters and large fuel tanks.

How do you design a spacecraft to keep working for years?

Spacecraft are very precise and powerful machines, but they can be fragile in space. Here, even a simple fleck of paint can punch a hole in a spaceship. So, to journey to the edges of the solar system and rescue stranded crews, your spaceship must be built robustly, with protections against small impacts from debris floating in space.

Food and water

If we want to keep our rescue crew alive for these long missions, we need to keep them fed and hydrated. Food can be dehydrated and kept very compact; this means that if you’d like you can pack enough food into your rescue ship for the whole journey.

Water is a more difficult resource to manage. You’ll have to carefully recycle all the water that your astronauts consume so that you don’t run out on your journey to the rescue site. It would be terrible if your rescue crew needed rescuing because they ran out of water!

Think of ways astronauts can reduce the water that they use, and how to recycle any water that might otherwise be wasted.


Keeping your spacecraft pointed in the right direction is a difficult task. Unlike on Earth where we can use a compass to tell where north is, in space there are fewer ways to really work out where you are.

You will need to design a way so that your spacecraft can work out where it is. It could use the stars to work out its location in the solar system, or it could even try contacting ground stations you have already installed on planets.

Rescue tool

When you are performing rescue missions in space, you might need some special tools to help you get to the stricken crew. This process might require your rescuers to perform spacewalks or cut into a broken spacecraft.

Make sure your spaceship is well equipped with the latest technologies and tools that can aid its operators to save the people who are in danger.

Let’s bring them home

We look forward to seeing how you are going design spacecraft that can travel through the vast expanses of space. We want to see how you’ve solved the challenges brought by long distance space exploration, and hope that your designs can help bring our crew home!