Yet according to Spaceref.com this is the goal of NASA's recently revived "Assured Access to Station" program, formerly known as "Alternate Access to Station".

This subtle name change in fact indicates a major and unheralded change in NASA's plans: it no longer intends to operate the aging Space Shuttle as a cargo-only Space Station supply vehicle after the crew exchange task is taken over by the Orbital Space Plane in 2010.

That plan has been subject to intense criticism from many quarters, including some key Congressmen. It seems very unlikely that they will agree to fund the complete requalification of the entire Shuttle system that the CAIB has mandated if Shuttle operations are to continue beyond 2010.

This poses a severe problem for the International Space Station, which is predicted to require about 70 metric tonnes of supplies per year when and if it is fully assembled.

Only a small amount of this can be lifted by the planned unmanned supply launches by the European, Russian, and Japanese space agencies. The Design Reference Mission recently supplied to the AAS contractors calls for 48 tonnes/yr to be delivered by the new vehicle.

However, the Reference Mission also includes a requirement to return 34 tonnes/yr of material from the ISS. This is an extremely onerous requirement. Even if this were done with a minimum ballistic water-landing RV with no safety systems, the total mass needed to be lifted to orbit would have to increase substantially over a throw-away system like Europe's ATV.

What is this material that needs to be returned from space at a cost of many thousands of dollars per pound? Exotic crystals and wonder drugs manufactured in zero-g? Samples and data from Nobel-prize-wining science experiments?

Surprisingly, most of the down-cargo from ISS will be junk -- broken components from the numerous support subsystems on ISS, which fail at an alarming rate. In the early days of ISS, it was planned that such failed equipment would be replaced by new hardware.

But many of the original ISS contractors are out of business -- and the ones that are left have little interest in making tiny numbers of complex products that are now obsolete and unsalable in the free market.

Instead of developing modern replacement systems or just building copies of the old systems in-house, NASA is choosing to repair a lot of broken or worn-out ISS hardware with its civil-service workforce -- after it has been carried down to Earth in the Shuttle's huge cargo bay.

This only makes sense if one treats the down-cargo lift as a free bonus, which it is in the case of the Shuttle. And in NASA's twisted cost accounting system, the repair workers' high salaries are also "free".

After all, they are becoming underemployed due to the run-down in ISS development, and they can't be let go because of the US government's arcane civil-service regulations. So it actually makes sense to use the Shuttle as a junk truck -- just like it made sense during the California gold rush to use clipper ships to carry dirty clothes to Hawaii for laundering.

But both these absurd situations are examples of distorted economics due to short-term special situations. The Shuttle's oversized cargo bay and high landing weight limit are inherited from other long-forgotten requirements. And NASA's staff should be employed on new projects, not fixing obsolete hardware.

If NASA intends to develop a completely new ISS supply vehicle, it should not be burdened with this huge and unnecessary down-cargo requirement, blindly carried over from the Shuttle program.

It would certainly be cheaper to buy or build brand-new ISS components than to design and operate a new Earth-return spacecraft to return broken ones from orbit. And anyone who owns a TV set knows that it is cheaper to buy new electronic devices than to diagnose and repair broken ones, if one has to pay the repairman's wages.

If NASA were to abandon its current make-work ISS maintenance policy, the true down-cargo requirement for science samples could be met by making the OSP capsule a little bigger. Then this new ASS vehicle could be a cheap one-way truck, or just a spam-can added on to the back of the OSP.

And "cheap" is the operative word here. The weakest point of the ASS program is that there is no money for the actual development of such a vehicle anywhere in the NASA budget plan.

And if NASA is to spend ~$15B between 2004 and 2010 on the development of the Orbital Space Plane, and continue to operate the Shuttle, and make the improvements in Shuttle mandated by the CAIB, it is not clear where the money to design this other Shuttle replacement vehicle will come from.

But in terms of the big picture, this project, which seems so stupid at first glance is actually a positive sign. Even if it were implemented as planned, it could only be a waste of money. NASA's previous plan to continue use of the Shuttle as a junk truck to 2020 would have wasted more astronaut lives as well. It appears that NASA is gradually and tortuously evolving a sensible plan to phase out the Shuttle and still keep the ISS operating. Perhaps those seven astronauts on Columbia didn't die for nothing after all.

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