The U.S. space shuttle is the only operating exception that re-uses a large part of its structure. The command module returns to earth after each flight and is re-used.
But for launching commercial satellites, the shuttle turned out to be more expensive than the throw-aways. And the Challenger explosion in 1986, killing seven astronauts, led the U.S. government to abandon its shuttle fleet for use on commercial missions.
Western Europe's Ariane rocket, U.S. Atlas and Delta rockets and Russia's Proton all launch satellites to Geostationary Transfer Orbit (GTO) for about $25,000 a kilogram. This is the orbit used for most large communications satellites.
"In an expendable launch vehicle about three-quarters of the cost goes into things that eventually end up in the Atlantic," Bob Parkinson a rocket designer for Matra Marconi Space told a space conference in Paris.
The U.S, Russia, Europe and Japan are all studying designs for Reusable Launch Vehicles (RLV) that aim to be more cost effective and reliable than expendables.
"With expendables an engine failure is a mission failure. With an RLV, if an engine fails and something begins to go wrong we can shut-down an abort mission. The possibility to abort is critical to getting the economics of RLVs right," Parkinson said.
COST EFFECTIVENESS CRITICAL
Rocket designers are mixed over the best design for RLVs, but they all agree that if they are to be cost effective they must be used often.
If RLVs are developed there will be a cross-over period when they are in competition with expendables.
"Expendables are existing systems. Someone has already paid for the development a long time ago, they have been cost-optimized. With a reusable system, someone has to pay a lot of money for development, tens of billions of euros or dollars.
"There is a cross-over point, that even if they are cheaper to operate, it is not until you have launched a hundred or two hundred times that your actual costs are cheaper," said Parkinson.
Europe's Ariane-5 rocket plans its first commercial flight this summer. That program aims to shave 10 percent off current launch costs
New generation expendables under development in the United States such as Boeing's Delta-4 or Lockheed Martin's Atlas-5 aim to reduce launch costs to up to 50 percent. They will not be in service for several years.
"All these evolutions are driven by financial considerations," said Eric Dautriat of France's Space Agency (CNES).
"The trend to lower and lower costs per kilo to orbit should be significant. This consensus must be taken into account when one tries to justify the economics of the reusable. (Prices) of future resusables must be compared not to the present expendables, but to where the expendables will be in ten years. In such a time frame it is not easy to make a decision, but we have to," he said.
Dautriat said that CNES' perceived hesitance to commit itself to RLVs was justified. "We want to avoid too quick and superficial statements which at times have been supported mostly by engineering wishful thinking and by some who search for governmental funds."
NASA STUDYING RLVS
The U.S. space agency NASA has been studying RLVs for years, but an American entry is still far away.
A new NASA assessment of the future of space transportation warns that the RLV revolution predicted by the U.S. launch industry is still at least a decade away.
The Space Transportation Architecture Study completed in February concluded that replacing the current space shuttle could reduce cost and risk of travelling to space and save $1 billion to $2 billion in launch costs per year.
"The only problem with the shuttle is that it isn't cost effective," said NASA's Steve Creech.
"We are looking to get the cost of space transportation down by an order of magnitude in ten years and that order of magnitude for us is $10,000 a pound. We want to get down to $1,000 a pound. We also have a further goal in the next 25 years to get the cost down by another order of magnitude," he said.
Creech said that lessons learned on the shuttle would serve for future designs. One costly component is the outer thermal tiles on the shuttle that has plagued its operation since it was put into service in the 1980s. The tiles protect the shuttle from extreme heat when it re-enters the atmosphere.
"We really learned a lesson on the shuttle. You spend a lot of money, a lot of operations manpower and a lot of time turning the vehicle around if you don't have an operable thermal protection system," Creech said.
ORBITAL SLOTS STILL AT A PREMIUM
While low earth and medium earth orbit satellite constellations may be headed for heavy growth, they have yet to prove themselves in the market. Specialists said geostationary satellites will continue to occupy a large place in the manifest of rocket launch companies.
With launch costs projected to go down, there will be greater economic incentive to launch more satellites to this orbit.
But the geostationary arc is already congested. This orbit, at 36,000 km above the equator, permits satellites to move at the speed of the earth and appears from the ground not to move. It is ideal for communications satellites. With one, an entire continent is covered. With three you reach the entire planet.
Companies and countries vie for lucrative slots in this orbit. There must be separation between the slots to avoid interference. Though a few operators have developed technologies to avoid interference and put several satellites in their allotted slot, most keep only one satellite. An equatorial slot that can cover a populous continent is a coveted piece of real estate.
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