A trip to the moon is all very well and it was a fantastic achievement in 1969, however we have clearly taken a step backwards in the last 20 years or so . The 'new' space shuttle has a maximum orbit of around 260 miles and even the nearest planet, Mars, is tens of millions of miles away.
It has been over thirty years since we landed on the Moon but still the dreams of travel to Mars, Pluto and the Oort Cloud remain as far away as ever, nevermind the dream of interstellar travel and exploring new solar systems.
If you have not already been there you can find out more about this step backwards in After Apollo.The Problem - Technology
The problem we have is that our current technology is simply
insufficient to achieve these dreams. Take our best chemical
rockets, even with these the trip time to our nearest planetary
neighbour is somewhere between one and two years!
This is not to berate chemical rocket engines, which work well
for operations in the near Earth environment, including the Moon.
For operations beyond this scope, however, they quickly lose
feasibility.
The reason for this is their inability to reach high velocities due to the low energy density of the chemical propellant. In other words chemical propellant produces relatively low amounts of energy per pound of fuel, hence why it needs those massive fuel tanks on liftoff (about 95% of the shuttle's take-off mass is fuel).
To summerise, while the
thrust of the chemical rockets is
impressive, its
specific impulse is poor. This is technical
jargon that means although there is much thrust available it is
impossible to use it for any significant length of time before
the fuel runs out.
So why not carry more fuel? Well if you wanted to take enough
fuel to make a 900 year trip(!) to the nearest star there would
be a real problem, there isn't enough mass in the universe! Even
for planetary missions the fuel requirements would be so extreme
it is simply not possible to carry the fuel needed. The energy
density of chemical propellant is just too low.
Another major obstacle that must also be considered is the
cost of space travel. At present to put a single kg into orbit
will cost you between $10000 and $20000. This is clearly
prohibitively high and a major objective for the coming years is
to drop the cost to a fraction of today's value.
Despite the fact that the space shuttle has regularly gone into
orbit over the last two decades there is still no tourist
business. This is due to the fact that to build an orbital hotel
under present conditions will cost 100's of billions of dollars
(at least). It is clear why there has been so little progress in
orbital developments.
Of course there is a final consideration, the safety factor.
We have been tragically reminded of this recently with the
Columbia disaster.
Our current technology is unable to make space travel
comfortable, convenient and above all safe enough for regular
travel. The pioneers will have to continue the space program
though to enable us to develop the technologies that will bring
space travel into the 21st century.
Throughout this section we will look at possible future technologies that will allow us to achieve the goals of improving performance, costs and safety. These technologies may allow us to finally realise the dreams of interplanetary and perhaps even interstellar travel.
Go on to Why
should We go and Explore Space Anyway?
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