Space travel: Rob Coppinger answers your questions
Rob Coppinger is a postgraduate engineer and has written widely about space flight. Here he answers your questions about space travel - from space suit technology to mining the moon and making contact with alien life.
What benefits has space travel given us?
Without satellites your satellite TV wouldn't work too well and you wouldn't have weather predictions, environmental monitoring, telecommunications and GPS. Also, the European Space Agency has an entire department dedicated to spin off technologies to benefit the wider society.
Will we travel to nearby star systems within the next 20 years?
No, the technology doesn't exist and it's likely it won't exist in the next 20 years. It might in the next 1,000 years. If we started seriously funding a Mars exploration programme now we could get to Mars in the next 20 years.
How long will it be until we build a space elevator?
We're still decades away from building a space elevator because we don't have the technology for a cable to reach the necessary 36,000 km and withstand being struck by space debris.
Do space suits have to be so big?
The size of space suits reflects a limitation of our current material technology. In the future, with better material science, we could have skin tight space suits like the ones you see in 1950s science fiction films.
How much shielding is needed to protect against harmful radiation in space?
This is currently one of the biggest dangers for space travellers who spend long periods of time in space. Water is a fantastic defence against radiation. A two metre column of water would provide excellent protection and this could actually be viable for space craft in the future but would add greatly to the mass of the spacecraft. To protect against solar flares you would also need a safe zone in the space craft that has thick metal walls.
How long can an astronaut stay in space without adverse effects?
Without a space suit, not long! But after that it gets complicated - in zero gravity human muscles and bone deteriorate.
How far into space have radio waves gone since the advent of radio? Would any aliens have heard them yet?
Radio signals travel at the speed of light. If the BBC's radio signals have been strong enough for the last 90 years then they have reached 90 light years. Aliens might have detected them if they live within a 90 light year distance - but that's quite unlikely.
Are ion-propulsion engines the best way to get to Mars?
Yes and no. No for our current technology; yes for proposed nuclear powered ion engines.
Where does space start?
It starts at 100 km, or 62 miles, above sea level. This boundary is generally agreed because in order to orbit the Earth you would need to be able to reach this altitude, at least.
If we had to leave Earth, how long would it take to plan and build an escape strategy?
We wouldn't have enough time to save everyone, assuming the threat was an asteroid. The problem is there isn't anywhere for us to go - you would need to terraform Mars and that would take a long time.
Could we grow trees on Mars to increase the amount of oxygen?
No, not without a greenhouse because it's too cold. You'd also need fertiliser. Otherwise it's great - there's more carbon dioxide than you'll ever need.
Is there scope for mining the moon for resources?
Yes, but it's very expensive. There's a company who wants to mine asteroids for platinum. It's so valuable that they think they'll still make a profit despite the expense.