It's just passed the thirtieth anniversary of the last man even to visit the moon and in an attempt to get a flagging space travel sector going the Ansari X PRIZE has been awarded to SpaceShipOne for matching and then slightly exceed the performance of the old X-15 spaceplane of nearly fifty years ago.
Is this then end? Will space travel taper off into a few high altitude fun rides to give pleasure to the rich and slightly famous? Maybe not - here looks at a different way that brings us back to the expectations of the 1930s not the let downs of the 1980s.
The popular media and fantasy fiction surround us with a lot of talk about exotic spaceship propulsion systems - talking about them gives the impression of progress - they sound cool and impressive without having to run the risk of anyone ever being expected to deliver on them. Let's look at what we are going to discount here. There's Anti-matter, Catapult Launchers, Laser Propulsion, Microwaves Propulsion (actually first postulated in the 1930's by E.E.Doc Smith), Magnetic Sails, Space Sails, Nuclear Fusion, Space elevators, Zero-point energy. The problem is we don't have the technology to hand for any of these- so they are all pretty much pie-in-the sky - certainly no-one reading this article now is going to be using them personally in their own lifetime.
So what is the answer? Is there a technology that would allow cheap, reliable reusable spaceships today? Surprisingly the answer is YES! Are we going to get them? Very possibility.
So what are they? Well its called the Nuclear thermal rocket, the prototypes were made thirty years ago and work just fine - and the time to get them might be just in the next ten years.
So how do they work?
In a nuclear thermal rocket a working fluid, which can be plain ordinary water, is heated in a high temperature nuclear reactor, and then expands through a rocket nozzle to create thrust. The nuclear reactor's energy replaces the chemical energy of the reactive chemicals in a traditional rocket engine. Due to the high energy of the nuclear reactions compared to chemical ones, over 100 times, the resulting efficiency of the engine is at least twice as good as chemical engines even considering the weight of the reactor. The ship doesn't have to very anything fancy - all the super lightweight materials and astronomical costs, and the need for multiple stage rockets - having to throw most of your spaceship away every time - all comes from the low thrust of chemical rockets. So the bottom line is that a a nuclear thermal rocket like the Timberwind 75 put into a tried and tested load carrier like the old German A4 (over three thousand were made as V2s - and back again in the Ansari X PRIZE entrant - Canadian Arrow) would make a simple reusable vehicle that could with refuelling travel anywhere in the solar system with an effective payload and capacity about the same as a VW Combi van or Landrover.
The Timberwind 75 is a design that uses a conventional (albeit light-weight) nuclear reactor running at high temperatures to heat the working fluid that is moving through the reactor core. This is known as the solid-core design, is simple to construct and are the only nuclear thermal rocket ever built. Development of such engines started under the aegis of the Atomic Energy Commission in 1956 as Project Rover, with work on a suitable reactor starting at LANL. Two basic designs came from this project, Kiwi and NRX in the late '50s.
More recently an advanced engine design was studied under Project Timberwind, under the aegis of the Strategic Defence Initiative ("Star Wars"), which was later expanded into a larger design in the Space Thermal Nuclear Propulsion (STNP) program. Advances in high-temperature metals, computer modelling and nuclear engineering in general resulted in dramatically improved performance. It used to be thought that solid-core engines would only really be useful for upper-stage uses where the vehicle is already in orbit, or close to it, or launching from a lower gravity planet, moon or minor planet where the required thrust is lower, and that to be a useful Earth launch engine, the system would have to be either much lighter, or provide even higher specific impulse. However using 1990s technology instead of 1950s technology means that Timberwind 75 would be a great "drop-in" powerplant for an A4 with a virtually identical mass and size. Although the thrust is reduced to just 13 tonnes (165347 lbf or 735.5 kN) the increased burn time allows for achieving not just low earth orbit but actually escape velocity making this a true reusable space vehicle. With orbital refueling the range and capability would be greatly enhanced and of course by coming down tail first under power the thermal risks that destroyed the shuttle Columbia.
And what of the risks? With modern fear of technological failure - where enough stress is caused seeing something going wrong on a screen rather than real life - is this something that anyone can bear to face! Well, atmospheric or orbital rocket failure could result in fallout. However given that oxide reactor elements are designed to withstand high temperatures (up to 3500 K) and high pressures (up to 200 atm normal operating pressures) it's highly unlikely a reactor's fuel elements would be reduced to powder and spread over a wide-area. More likely highly radioactive fuel elements would be dispersed intact over a much smaller area, and the overall hazard from the elements would be confined and much lower than the many open-air nuclear weapons tests that have been carried out.