The idea of reusing stages or all of a space launch vehicle has been around since before Buck Rogers first appeared in 1928. In fact, Jules Verne wrote about such a vehicle in 1865, when he published "From the Earth to the Moon."

Verne was one of the first science fiction authors, but he would be surprised to learn that we have only been able to build a partially reusable vehicle, the Space Shuttle. Why are we still struggling to create such a machine?

First, let's distinguish a space launcher from a suborbital vehicle. Space launchers are capable of achieving at least orbital flight about the Earth. Suborbital vehicles are able only to fly vertically to heights that exceed the sensible atmosphere, but they lack the speed to achieve orbit.

Thus, the several tourism vehicles that are being developed, such as that being built by Virgin Galactic, cannot achieve orbit. All of the world's current space launch vehicles, except the Shuttle, are completely expendable. In other words, none of the hardware is used more then once. Even the Shuttle is only partially reused.

As you might expect, this is an expensive way to get to orbit. Imagine if you could only drive your car to work once and then discard it. Every trip that you tool would require a new car. In stead of costing a few dollars each time you went to work, it would cost thousands.

The mere fact that a car is reusable makes each trip very inexpensive. So, why does the space program have to pay tens to hundreds of millions of dollars for each launch?

The simple truth is that we do not know how to make reusables and we cannot make a good business case for them. Many have tried, but all have failed. Most recently NASA spent over one billion dollars trying to build a scaled down technology demonstrator, the X-33.

This was to be the forerunner for a single-stage-to-orbit vehicle, VentureStar. In 2000, after several years of trying to build the demonstrator, the program was shut down. The needed technology was simply not ready.

Walter Kistler started a reusable launch vehicle company around 1993 to pursue a two-stage-to-orbit, fully reusable vehicle. Kistler Aerospace raised over $500 million in private funds and proceeded to construct the first prototype, the K-1.

But, the vehicle got too expensive and the perceived market disappeared when Iridium filed for bankruptcy at the turn of the century. Kistler Aerospace was liquidated before completing that first vehicle.

Here we are. It is 2009 and there are no fully reusable space launchers. The Shuttle is scheduled to be retired next year, and be replaced with an expendable Ares I. There are no near-term prospects for a truly reusable launch vehicle.

SpaceX has announced that Falcon stages may be retrieved and partially reused, but that has yet to happen. To summarize, we are spending an average of roughly $70 million per launch, when we could be spending about one-tenth of this amount, if only we had reusables. Why?

The answer has several parts. There is not enough launch vehicle demand to justify the multi-billion-dollar expense of developing a true reusable. In order to cut the per-launch cost by a factor of 10, there would have to be an extremely high launch frequency.

Today, the world wide annual launch rate is about 68. This will have to increase by an order of magnitude or more to make the reusable financially viable. To further complicate the picture, reusables are limited to low orbits about the Earth. The requirement of returning the vehicle limits the distance from Earth because the propellant needed to return is very limited.

The Shuttle is limited and cannot go beyond the International Space Station. This eliminates one of the most important launch customers, the geostationary satellite operators.

Finally, there are several challenging technology issues that must be resolved before we can build a reliable, high-performing reusable vehicle. Sadly, is does not appear that reusables are in our near-term future.