>From: paul <astro@pgog.net> >Sent: Dec 20, 2004 12:59 PM >To: SeeSat-L@satobs.org >Subject: shuttle, please explain >haven't I also read that NASA is not sending shuttle to HST >for maintenance update because that is not safe. it is safe >to repair ISS but not safe to repair HST. what am I not >understanding? Its all about safety. If the Shuttle is damaged during launch, it can hang out in a pressurized location (ISS) until it is fixed or there can be an emergency return of crew using the Soyuz vehicles on ISS. Also, the cameras on ISS will be used to inspect the external surfaces on the Shuttle. No such inspection would be possible at the HST site. Since inspection of the entire Shuttle surface is required for a safe return, this rules out going to HST. Why not go to HST from ISS or visa versa? HST (500km/35 deg) is at a different altitude /inclination than ISS (400km/51 deg). Because of the large inclination difference, the amount of fuel needed to move from one inclination to another is large. It is unlikely to be able to go from HST to ISS (or visa versa) unless some kind of thrusters are used on the Shuttle that are not planned. Note it is easy to launch a shuttle to the HST inclination (28 degrees inclination is typical for Shuttle launches) and more fuel is used to launch to ISS, but the ISS inclination was chosen as a compromise to have Russian participation. ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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