Rockets are really insanely expensive. For the best part of the space race a single NASA launch has cost just over $1bn. That works out at $200,000 per Kg. To put that into perspective, if you want to take one small bottle of water that'll be an extra $30,000. Considering how heavy scientific, communication and mining equipment can be, it becomes obvious that rockets are unlikely to open up access to this vast resource.
The potential for more commercially viable space travel has caught the attention of several tech-billionaires over the last 10 years: Elon Musk is working on SpaceX which takes a reusable approach to rockets by landing them vertically back on earth. This aims to get the cost down to around $1.6bn for 12 launches (roughly an order of magnitude cheaper). Virgin Galactic has taken the approach of putting a shuttle on top of a plane for a large part of the distance before engaging the rockets. So far they've only reached 71,000 ft (13 miles). Another really interesting approach is that being taken by our friends at UK company Reaction Engines
. They have created an engine that works both with and without atmosphere, meaning that you can use the same engine to both take off and move into space, an incredible achievement.
Overall, the use of rockets, and therefore enormous amounts of fuel, is always going to be a hugely expensive method of reaching space. It is a brute force approach. Meanwhile, the non rocket based approaches (covered below) which have been proposed so far have failed to obtain financial backing due to enormous upfront cost that is unlikely to pay back within a financially sensible window. What's needed is a completely new approach.