Star Points for May, 2005; by Curtis Roelle Can the Hubble Space Telescope be Saved? - Part 2 In March we looked at the rationale behind NASA's decision to cancel a previously scheduled space shuttle mission for servicing the Hubble Space Telescope (HST) currently in earth orbit. Thus, when the on-board systems eventually fail, HST's useful life will come to an end and so will its dramatic images of the cosmos. In response, many astronomers, including one Carroll County amateur astronomer, have been racking their brains trying to come up with compromises or alternatives that might save HST. Woodbine resident and previous Star Points guest columnist Ray Sterner is an amateur astronomer. Ray has been closer to HST than most amateur astronomers. Ray was one of the first and only amateur astronomers to be granted observing time using HST. Like professional astronomers, Ray submitted a proposal -- his was for observing a distant yet interesting cluster of galaxies -- that was accepted by the committee responsible for doling out telescope time. The cancellation of HST repair missions using the space shuttle got Ray thinking of possible ways to save it. Since NASA is considering outfitting HST with a retro rocket to be used to steer it into the ocean at the end of its life he wondered why a larger motor couldn't be installed instead. With a more powerful rocket HST could be maneuvered into an orbit similar to the International Space Station (ISS). Then astronauts would have a "safe haven" to go if a space shuttle became seriously damaged at launch on an HST servicing mission. Ray thought that since the solution to the problem seemed so simple surely someone else must have thought of it before. He began searching the web and soon discovered a paper published by the Association of Universities for Research in Astronomy (AURA) that examined the possibilities and pitfalls associated with the idea of kicking HST into a different orbit. HST weighs only about a tenth of what a shuttle weighs when landing so the fuel required for changing orbits is much less with HST. Still, a chemically fueled rocket would require a large amount of fuel for nudging HST to its new orbit. Are such rockets available today? Fortunately, they are. But the problem with them is the acceleration they produce would create stresses beyond the tolerances HST is designed to bear and it could be damaged. Smaller gentler rocket motors are also available. However none have the fuel capacity need for the HST maneuver. It might be possible to modify an existing one but that would take additional time. An alternative to chemical rockets are those that are powered by electric propulsion. These are low thrust rockets powered by electricity which in turn is collected by solar panels. A satellite like HST in low earth orbit spends about half its time in the shadow of the earth. Thus, the rocket can only use solar power half of the time. It is estimated that it would take up to three years to move HST using electric propulsion! In the meantime HST would have to be in a so-called "safe" mode where it is essentially switched off. In the mean time its internal systems may atrophy and continue to wear. Would a three year hiatus be acceptable to astronomers? The down time could be reduced by using multiple rockets but then the electrical requirements would be increased. The power requirements for electric propulsion would mean that enormous solar panels would be required. Another suggestion is to use a hybrid of chemical and electrical propulsion. A constant thrust could be achieved using the electrical propulsion in sunlight and the chemical propulsion while in earth shadow. Another idea that has been all but ruled out by NASA is the development of a robot that could be launched to fix HST. Such an unmanned mission would not risk the lives of shuttle astronauts. However, the technology still has some growing up to do. The ultimate decision of what to do with HST will be based on budget considerations and NASA's own goals. The next generation space telescope is being developed and NASA is also looking forward to expanding human exploration by returning to the moon and pressing onward to Mars. One of the casualties may be HST. The bottom line is that given NASA's new guidelines for shuttle safety, physics and engineering are all that stands in the way of salvaging it. AURA's report can be read online at http://www.aura- astronomy.org/nv/hubble.pdf .