re hst servicing mission scheduled for days in article apr stsci edu hathaway stsci edu writes in article rq os i access digex net prb access digex net pat writes in article t nhg rpi edu strider clotho acm rpi edu greg moore writes as herny pointed out you have to develop the thruster also while much lighter you still have to lift the mass of the thruster to orbit and then the thruster lifts its own weight into a higher orbit and you take up room in the payload bay a yes but the improvement in boost orbit to the hst is significant i do not understand what you are saying here what is improved what is significant and what does this have to do with carrying more equipment on a servicing mission also as implied by other posters why do you need to boost the orbit on this mission anyway maybe you have something here but could you please clarify it for us on the net right now the hst sevicing mission is listed as days before it was listed as days they just kicked up the number of spacewalks to after simulations indicated that it was not do able in after all the space walking they are going to re boost the hst s orbit i think right now it s sitting at miles up they would like i don t know the exact orbit numbers i know when hst was first flown it was placed in the highest possible shuttle orbit now the shuttle can cary a thing called the edo pallet or extended duration orbiter pallet it s mostly lox lh for the fuel cells and rcs gear plus more o and canisters for the life support re breathers maybe more nitrogen too the limit on space walking is a function of suit supplies mass and orbiter duration in order to perform the re boost of the hst the oms engines will be fired for a long period now the shuttle is a heavy thing the hst isn t light either the amount of oms fuel needed to fly both up is substantial a small booster carried up and used to boost hst on it s own will weigh significantly less then the oms fuel required to boost both hst and shuttle for a given orbital change from what i understand the mass margins on the hst missions are tight enough they can t even carry extra suits or mmu s now if they used a small tug i would bet just a wild guess that the savings on amss margin would allow carrying the edo pallet extra suits more consumables parts for the flaky fgs sensor parts for the balky solar electronics and still enough for a double magnum of champagne or the hst could even get placed into some sort of medium orbit the reason they want a high orbit is less antenna pointing and longer drag life and that means you can then carry edo packs and enough consumables so the shuttle mission can go on long enough to also fix the array tilt motors and god knows what else is going to wear out from what i ve heard the motors are fine it is one of the two sets of electronics that control the motors that needs a fix the motors and electronics are separate pieces of hardware i expect to be corrected if i m wrong on this a whatever it is the problem in the tilt array is a big constraint on hst ops pat
