Wednesday, 12 August 2009
Space for all coming soon (Part II)?
So what's the issue?
Well encombant space vehicles can be broadly divided into two categories: (1) those inspired by winged aircraft and (2) those inspired by ballistic rockets (the difference between wizz and the bang).
In the early days of the space race both winged and ballistic craft were considered viable options for reaching orbit. Yet they represent vastly different ideas about space travel in terms of both the engineering challenges and economic viability.
Ballistic spacecraft basically pile in the fuel and use brute force to push their way into space, shedding engines and fuel tanks on their way up to lighten the load.
Winged spacecraft are the more elegant option. Launching from the ground or from the back or belly of another aircraft, they use the Earth's atmosphere for lift as long as possible. On the way back, they glide down to Earth to be used again and again. Their potential reusability has led to the tantalising idea that winged spacecraft could, in time, be much cheaper to operate than ballistic throwaways. They might even use the same facilities as commercial airliners, opening up space travel to commerce and tourism.
In plain reality, winged spacecraft like SS1 and NASA's X-15 - which reached an altitude of 107 kilometres - have never really made it past the lower reaches of space. Their on-board rocket engines lacked the oomph to propel them the extra 60 kilometres (to 167k) needed to reach orbit.
The conspicuous exception to this rule is the space shuttle, a vehicle that was part winged spacecraft and part ballistic vehicle. The shuttle isn't completely reusable, however, on each flight the expensive external fuel tanks are dumped in the ocean. Yet it showcases the most important technologies for low-cost, reliable access to space. The key is Reusability, combined with Flying Often. Where the shuttle falls down is the 'Flying Often' part.
Originally designed to fly hundreds of times a year and reduce costs of each flight, the shuttle fleet has never managed more than 9 flights in a year.
However, NASA's so-called 'Constellation Programme' - a mega-project set to replace the current shuttle - has a amjor goal of sending people to the moon on a regular basis. But while some elements of Constellation's spacecraft are designed to be reusable, the design - I think - is a step back towards the Apollo era. It can probably be made reliable enough, but it will never be low-cost because it will never be flown enough.
And so? The true space era - based on these encumbant technologies - seems, well, some way-away.
But that's not the end of the story. There are alturnative space access technologies now being experimented with that are so radical, so revolutionary, and so compelling that, I think, may shock even the most hardend Hyperinnovator (see part III below).