I've already expressed my belief that the construction of the Station could be completed entirely with unmanned Shuttle flights, in which the Shuttle is launched and rendezvouses with the Station in unmanned mode and is docked with the Station by the Station's crew using the Station's big mechanical arm -- after which that crew could board the Shuttle and carry out the needed unloading and installation of the new Station modules themselves.

The Shuttle could then reenter and make an automatic runway landing in unmanned form, with virtually no more risk of going off course and crashing than in its current manned landings -- and no risk at any time of losing a crew through its unquestionably serious danger of malfunction during launch, reentry or landing, which will remain high no matter what corrective measures NASA takes because of the Shuttle's basic design as a winged craft that has no launch escape system and is unstable during reentry.

But there's another serious problem resulting from the Shuttle's current travails: what to do about its last two scheduled missions to the Hubble Space Telescope?

It was scheduled to fly a final servicing mission to Hubble in 2004, in which the crew would install two new replacement science instruments, replace the Hubble's attitude-control gyroscopes (its most unreliable parts, with two of the latest set of six already having failed since their installation), and do other lesser repairs.

Then, years later (somewhere around 2010), when the Hubble has finally suffered enough new malfunctions to make it unusable for science, the Shuttle would have made one last flight to it and loaded it into its cargo bay to return it to the Smithsonian Air and Space Museum, since Hubble is big enough that the uncontrolled reentry it would make a few years later would have a small but definite chance of raining dangerously large debris (especially its mirror) down onto Earthlings.

After that, NASA would officially focus on making observations instead with the new James Webb Space Telescope, which will have a far bigger mirror but be much lighter and cheaper than Hubble, will focus much more on the infrared, and will be hung in solar orbit 1.5 million km from Earth so that no repair visits to it are possible.

The monkey wrench thrown into this plan by the Columbia disaster is even bigger than that which that accident has thrown into the plans for the Station -- for Hubble cannot be repaired by any unmanned space mission, by the Shuttle or any other craft.

And if it isn't repaired, its remaining useful lifetime is seriously short -- it currently requires at least three working gyroscopes to point itself for science observations, and the Hubble project's "Reliability Model" estimates a 50-50 chance that two of its four remaining gyroscopes will fail by the end of 2005 and a 85% chance that this will happen by the end of 2006.

Its controllers are now devising an emergency mode that would enable it to continue carrying a lot of its science observations with only two working gyros, but this would extend its working lifetime by only another 12 to 15 months.

It can almost certainly be at least kept alive, with its solar panels pointed stably toward the Sun, with no working gyros at all -- the SOHO and FUSE astronomy satellites have already been reprogrammed to actually continue their science observations in such a case -- but Hubble requires much more precise pointing, probably impossible with only one or no gyros.

It seems insanely wasteful to throw away such a vaulable (and publicly beloved) scientific instrument so soon, if there is any acceptably safe and cheap way to refurbish it again -- especially since the replacement Webb Telescope's scheduled 2011 launch is likely to be delayed a year or so, and in any case it can't make Hubble's observations in visible and ultraviolet wavelengths.

But future Shuttle launches to Hubble are even more dangerous than Shuttle flights to the Station. It's a vicious twist of fate that Columbia suffered its accident on one of the very few remaining Shuttle missions not scheduled to visit the Station -- had the fatal wing damage happened on such a flight, it would almost certainly have been discovered after the Shuttle docked with the Station (or even earlier, using the Shuttle's camera-equipped arm), three of the ten people on the Shuttle-Station complex could have immediately returned to Earth on the Station's Soyuz "lifeboat", and an emergency speedup of launches of Russia's Progress and Soyuz missions (along with the extra supplies on the Shuttle itself) could probably have kept the remaining seven alive until three could return to Earth on the next Soyuz launched in April and the remaining four could return on later Soyuz flights. The Shutle itself would have been lost, since there was no way to reliably repair it in orbit, but there would have been no deaths.

With this in mind, NASA is seriously leaning toward a new rule making it mandatory that all future Shuttle missions (unlike Columbia) should at least be launched into an orbit with the same 51-degree inclination as the Station, so that if damage preventing a safe return to Earth is discovered in orbit, they can make an emergency rendezvous with the Station for such a rescue. But Hubble's orbit is inclined only 28.5 degrees to the equator, and there is no way for a Shuttle visiting it to carry out an emergency rendezvous with the Station.

So: what to do? NASA appointed a "Hubble Transition Panel" consisting of six of the world's most famous astronomers to try to come up with the best possible courses of action, and with surprising speed -- after only one public meeting -- they reached agreement on three possible courses, depending on how many more Shuttle missions NASA finally thinks it safe to launch to Hubble.

If NASA still thinks it safe to launch two more Shuttle flights to Hubble, the first one should still be the planned "SM-4" servicing mission, delayed to 2005-06, and with the unavoidable launch delay perhaps being used to further improve the set of new replacement gyros.

As for the second visit around 2010, NASA had already decided to dump any plans to return Hubble intact to Earth -- its added weight in the cargo bay would make the Shuttle's landing more dangerous, and in any case it would really be seriously scientifically wasteful when compared to flying one additional servicing mission ("SM-5"), in which Hubble's lifetime could be extended for still another few years and perhaps one or two new replacement science instruments installed on it.

The danger from an ultimate uncontrolled Hubble reentry in that case can be eliminated by building a relatively cheap "deorbit module" with solid-or-liquid-fueled retrorockets, which the final servicing mission would attach to its base so that -- when Hubble finally exhausted its useful science life once again -- the retromodule could be fired to bring it down to a safe reeentry over the ocean.

What if NASA only dares to fly one Shuttle mission to Hubble? In that case, the panel recommended delaying the SM-4 servicing mission until the time when Hubble is about to lose its two-gyro capability -- and, if possible, completing the retromodule by then so that the Shuttle could attach it on that mission.

But what if NASA finally decides that it doesn't dare fly even one more Shuttle servicing mission? How can Hubble be brought down in a safe and controlled manner? The panel suggested that, in that case, it may well be possible to design the retromodule as a complete robotic spacecraft capable of automatically rendezvousing with Hubble and attaching itself to the telescope's base (using a copy of the same "attachment cradle" which anchors Hubble upright in the Shuttle's cargo bay during repair missions).

It added that not only did such a robotic mission seem feasible, but that it might actually turn out to be cheaper than a Shuttle mission for that purpose.

And what about the science loss from failure to fly the SM-4 mission that would prolong Hubble's life and add two greatly improved and already-constructed science instruments (the "Cosmic Origins Spectrograph" and the improved third version of Hubble's "Wide-Field Planetary Camera")? Here we face a tremendously important -- and scandalous -- fact.

As many impartial observers have pointed out, NASA's entire argument that the Shuttle is necessary and worthwhile to repair Hubble has actually been (like so many of its other arguments for the Shuttle and the Station) a flat-out shill from the start, a deliberate and dishonest attempt to further trick Congress into providing the massive funds needed to develop the Shuttle.

The Shuttle is so expensive to fly -- each of its Hubble servicing missions costs between $700 million and $1 billion -- that, for the cost of only two such missions (and perhaps less), a complete new duplicate Hubble could be constructed comparatively cheaply from the blueprints for the original (with whatever improved equipment and new experiments seemed appropriate) and launched on a Titan booster without any need to risk human lives.

Many of the scientists advocating Hubble at its beginnings uneasily suspected that this might be the case, and that it might actually be a mistake not to have it launched into a much higher-altitude orbit where repairs would be impossible but its observations would be far less seriously blocked by the underlying Earth -- but NASA hitned strongly that in that case it would not support Hubble at all, and so they made what some of them in retrospect tend to regard as a "deal with the Devil".

NASA is still attempting to conceal this fact -- NASA's technologically challenged new Administrator Sean O'Keefe, in addition to making whole series of other major misstatements of fact during his testimony before Congress (possibly because his more experienced NASA underlings are deliberately feeding him misinformation), continues to insist that the Shuttle is worthwhile even if the International Space Station is cancelled because it can repair Hubble -- but the Hubble Transitition Panel made it clear in its final report that it was aware of it.

While the Panel did not think it scientifically worthwhile to actually propose launching a full-scale replacement Hubble until late in the 2010s -- by which time new technology will allow the next big space telescope working in the visible and UV wavelengths to be vastly improved -- it did suggest that, if no more Shuttle servicing missions were flown, NASA should seriously consider "a dedicated new mission featuring a fast-track 2-meter class telescope [smaller than Hubble's 2.4-meter mirror] with COS and/or WFPC-3 in the focal plane, instruments that are built and could be adapted at minimum cost to a stand-alone mission.

Such a mission [being lighter-weight than a full-scale Hubble clone] could conceivably be launched into a geosynchronous orbit [36,000 km above Earth] by 2010", especially because by then the new heavy-lift Delta 4 and Atlas 5 boosters will be available to launch it for far less than a Titan would cost.

But it appears to this reporter that there may be yet another alternative, cheaper and far less risky than a Shuttle servicing mission, but much more scientifically productive and cost-effective than simply letting Hubble fail within three years and replacing it with a far less powerful replacement satellite. It may be possible to fly one or more manned servicing missions to Hubble WITHOUT having to use the Shuttle.

NASA has recently announced that it now intends to make its next manned orbiting vehicle, the "Orbital Space Plane", a much smaller manned vehicle launched on the Delta 4 or Atlas 5 -- available by 2008 rather than 2010, both as a new emergency "escape lifeboat" for the Station and as a way to send replacement crews to the Station much more cheaply than the Shuttle (and more safely, since it will be equipped with a launch emergency escape rocket).

It has also recently hinted strongly that it may follow the advice of many engineers and actually make the "Plane" a wingless capsule, a sort of improved Apollo spacecraft with a crew capacity as large as six, that would make a simple parachute landing on either water or dry land -- thus greatly increasing the craft's payload capacity and also making it, on balance, a much safer reentry and landing vehicle than any kind of winged spaceplane.

The OSP, winged or not, will be capable of routinely rendezvousing and docking with the Station -- or with other satellites. It could also, like Apollo, dock nose-to-nose with a separate, relatively lightweight and low-cost "Hubble Workbench" -- either carried as additional payload on the same booster as the OSP, or separately launched as an independent satellite, probably solar-powered -- which would be equipped with a Hubble attachment cradle; the necessary Hubble replacement parts, instruments and repair tools; and a modified version of the Shuttle's arm. (If the OSP's booster had sufficient spare capacity to carry the Workbench as well, it might even be attached to the OSP from the beginning.)

The resulting complex could then easily rendezvous with Hubble and use its arm to link Hubble to its cradle, after which part of the OSP's crew could carry out the same sort of repairs that would be carried out on a Shuttle-based servicing mission.

It's possible that such a mission could be flown for no more than the cost of the Transition Panel's proposed scaled-down Hubble replacement satellite, while allowing years of continued observations with all four of Hubble's instruments rather than just the two that would be carried on the Hubble Replacement.

This may be particularly true since -- if the Hubble Workbench, weighing only a few thousand kilograms, was initially launched as a separate satellite -- it might be able to carry, as part of ts payload, the Hubble "Deorbit Engine", thus removing the need to mount that on an entire unmanned spacecraft sophisticated (and expensive) enough to carry out a totally automatic rendezvous and docking with Hubble to attach the Deorbit Module.

But the OSP won't be available until 2008, and it's extremely likely that Hubble will have lost enough gyros to remove its ability to make science observations by 2006 or 2007 -- although it could probably be kept alive long enough to wait until the OSP repair mission is ready. Is there any way to fill in this serious gap in its science observations? Perhaps, for there is yet another manned vehicle already available that might be adaptable to the purpose -- the Soyuz.

Right now Soyuzes, being launched from the high-latitude Russian base in Kazakhstan, can match orbital planes with the Station, but cannot rendezvous with the Hubble. However, the European Space Agency has just signed an official agreement with Russia to allow launches of the Soyuz booster from its equatorial launch pad in French Guiana starting in 2006 -- and this could allow manned Soyuzes to be thus launched and rendezvous with Hubble.

If design and development of the Hubble Workbench as an independent satellite was begun quickly, it might well be ready for launch by 2006 -- allowing a separately launched Soyuz to rendezvous and dock with it and then carry it to Hubble for the servicing mission.

While Soyuz can carry only a three-man crew and has less ability to maneuver in orbit than the OSP will have, the cost of launching and carrying out Soyuz missions is so low that it might very well be possible to split the SM-4 servicing mission into two separate Soyuz-Workbench missions for less than the cost of a single Shuttle-based servicing mission.

It might even be possible to design the first Workbench so that it could remain attached to Hubble while the telescope resumed its science observations -- after all, the Hubble Deorbit Module will probably be so designed -- and this would allow the second repair Soyuz to simply dock directly with the still-attached Workbench, carrying only a lighter load of Hubble repair parts and instruments in its forward "payload module", rather than NASA having to build and launch a whole second Workbench.

The last Hubble servicing mission (SM-5) would occur after 2008, allowing it to be done with a single visit by the OSP rather than another two visits by Soyuz -- and, if SM-5 isn't flown as a full-fledged servicing mission, the Deorbit Engine could be attached to Hubble by either a single OSP or a single Soyuz, eliminating the need to design and build an entire automatic rendezvous and docking spacecraft just for that one purpose.

(If SM-5 is a full-fledged servicing mission, the Deorbit Engine would be mounted on the Workbench for that mission, with Hubble's attachment cradle fastened to the engine's top. If SM-5 is cancelled, the Deorbit Engine would be carried into orbit along with the OSP -- or, if Soyuz was used for this mission, the Engine would be orbited separately by a small rocket and attached to a small, cheap attitude-stabilization package and docking fixture so that Soyuz could pick it up in orbit and then carry it to Hubble.

Since a Soyuz launch from equatorial French Guiana gives the Soyuz booster a good deal of additional payload capacity, it might even be possible to launch the Deorbit Engine on the same booster that carried the Soyuz spacecraft.)

This reporter is no engineer, and it may well be that the details of mission design, cost, weight or risk would make Hubble servicing missions with Soyuz -- or even with the OSP -- impractical. But, especially given NASA's continuing self-interested attempts to make it appear that the Shuttle is necessary for such missions, and the speed with which the Hubble Transition Panel wrote its report, I wonder whether the Panel was given enough information to adequately consider these alternative possibilities.

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