The recent successes of SpaceX's Dragon spacecraft and the Falcon 9 rocket that lifted it to the International Space Station have been hailed in many quarters as a leap forward for modern space exploration.

This was the first non-governmental mission to dock with the space station and the first real step in the US Government's plan to contract out space services to private companies. In a few years the Dragon should be carrying astronauts to the station as well.

So if the Dragon is the next step forward in space travel, why does it look like such a big step back? It's a far cry from the futuristic black and white space plane that preceded it. The Dragon is a blunt-ended metal capsule with a couple of solar panels attached, that bears a striking resemblance to the venerable Soyuz spacecraft that the Russians first designed in the 1960s and which still operate today as ferries to and from the space station.

The reason the Dragon looks like it does, and why the Russians are still flying updated Soyuz capsules today (instead of their own little-known space shuttle, the Buran, which they developed and tested in the 1980s) is that capsule systems just work. They are simple and reliable - as simple and reliable as space technology can be, that is - and the shuttle wasn't.

It does seem terribly wasteful to throw away most of your spacecraft each time you launch one, as happens with capsule systems. And perhaps if NASA stuck with its original shuttle plans it would have been the reliable, cheap and reusable vehicle it intended. But as its budget dwindled the compromises began and the shuttle ended up missing all of those lofty goals.

The shuttle was a technical marvel, but it was just too complicated to be practical. For example, once it left orbit it had no engines to control its descent and therefore went from orbiting at a speed of almost 8 kilometres a second to a gentle landing on a 5km runway by unpowered gliding. If something didn't work, there were no second tries - everything from the heat-resistant tiles on the shuttle's belly to the weather on the flight path had to be right first time or everyone on board would die.

The landing needed such precision that it was entirely under computer control. All the crew did was press a button to lower the landing gear.

The capsule approach, by comparison, permits a landing anywhere in a large area - and provides alternatives if it doesn't. Putting people into space in a capsule is hardly a cakewalk but it allows more flexibility and fault tolerance that in turn leads to better safety and lower costs.

The figures speak for themselves. The shuttle costs something like ten to fifteen times as much to launch as a Soyuz and has a worse safety record. We may see something like the shuttle again but for now, capsule systems like Soyuz and Dragon are likely to be the main way to put people into orbit.

- © Fairfax NZ News

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