haw30@duts.ccc.amdahl.com (Henry A Worth) (02/11/91)
In article <1991Feb10.022414.2365@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: > >Because we'd be lucky to see HST2 in orbit before 2010, given the rate at >which such large projects get funded and done these days. Frustrating...,But should we just give up? Now, as H.S. surely knows :-) , much of the cost and delay of recent projects has been due to their relience upon the Shuttle. This may have been a resonable decision back in the 70's when the shuttle was expected to provide frequent, low-cost (compared to ELV's) access to LEO. Unfortunately, the shuttle has been somewhat of a disapointment... So, are we better off repairing the HST, or would the HST's lifetime servicing costs significantly offset (or even cover) the costs of a follow-on (or even a series) designed with today's realities in mind? Besides, the HST is hardly useless, it would still be up there doing its thing while the follow-on is under developement. For example: by not servicing the HST and using an ELV to launch a follow-on/supplement to the HST we would: > Save the cost of several shuttle flights (big $$$'s). Freeing up those shuttle flights for other purposes would also be of significant value. > By using an ELV we would also save the cost and complexity associated with man-rating a satellite for shuttle launch and on-orbit servicing. > Giving up on-orbit servicing opens up the possiblity of a geo-sync orbit with reduced operating (communications) costs and reduced solar array/battery capacity requirements. > With no on-orbit servicing the project lifetime may be reduced. But, some of that may be made up with a simpler, more-reliable design and a more stable orbit. Then again, the shuttle is hardly as dependable a repair service as the auto club, so there may not be that much gained from on-orbit servicing anyway; perhaps even a loss as there are more things to break... Using a commercial ELV also opens up the possibility of having NASA's role reduced to that of a minor sub-contractor providing launch facilities (and possibly, communications support if geo-sync is not used). For example: funding could be provided through the NSF to a university consortium with the appropriate demographic pork-factors. -- Henry Worth -- haw30@duts.ccc.amdahl.com No, I don't speak for Amdahl -- I'm not even sure I speak for myself.
mboone@hpuxa.ircc.ohio-state.edu (Michael B. Boone) (02/12/91)
In article <32iu02bN05Of01@JUTS.ccc.amdahl.com> haw30@DUTS.ccc.amdahl.com (Henry Worth) writes: > For example: by not servicing the HST and using an ELV to launch >a follow-on/supplement to the HST we would: ^^^^^^^^^^^^^^^^^^^ Like what?? > > Giving up on-orbit servicing opens up the possiblity of > a geo-sync orbit with reduced operating (communications) > costs and reduced solar array/battery capacity requirements. If you could get it there without breaking something, what would you do if something breaks early on in the "fixed" project? > > With no on-orbit servicing the project lifetime may be reduced. ^^^^^^^^^^^^^^^^^^^^^^^^ No kidding! A week or two? > But, some of that may be made up with a simpler, more-reliable > design and a more stable orbit. Then again, the shuttle is hardly > as dependable a repair service as the auto club, so there may > not be that much gained from on-orbit servicing anyway; perhaps > even a loss as there are more things to break... If there are more things to break, putting it in a geosynchronous orbit surely can't help matters! And while the shuttle is no "Auto Club", a human up there to fix things is much better than a radio. >Henry Worth -- haw30@duts.ccc.amdahl.com Mike Boone -- mboone@hpuxa.ircc.ohio-state.edu
henry@zoo.toronto.edu (Henry Spencer) (02/12/91)
In article <32iu02bN05Of01@JUTS.ccc.amdahl.com> haw30@DUTS.ccc.amdahl.com (Henry Worth) writes: > Now, as H.S. surely knows :-) , much of the cost and delay >of recent projects has been due to their relience upon the Shuttle. While this is somewhat true, the extent of it is much exaggerated. When you look hard at the scheduling for HST, in particular, you find that although its launch nominally slipped several times due to pre-Challenger shuttle delays, in fact the thing was only barely ready to launch in spring 1986, and some useful upgrades ended up being done during the post- Challenger hiatus. At least until Challenger, the shuttle delays and resulting cost increases were only just keeping ahead of HST's own delays and resulting cost increases. :-) >... So, are we better off repairing the HST, or >would the HST's lifetime servicing costs significantly offset >(or even cover) the costs of a follow-on (or even a series) designed >with today's realities in mind? As has been pointed out repeatedly in other connections, just because you save money in one area doesn't mean you get to spend it somewhere else. HST has already had too much spent on it to just write it off; that would almost certainly kill any hope of a successor. Bear in mind that much of the servicing planned for HST is *not* the result of the mirror screwup or the solar-array problems. If you write off all servicing, you probably write off the telescope after only a few years. You cannot possibly get a replacement up there that quickly. It would take until after the first servicing visit just to get such a project approved as a major new start. > For example: by not servicing the HST and using an ELV to launch >a follow-on/supplement to the HST we would: > > Save the cost of several shuttle flights (big $$$'s). Freeing > up those shuttle flights for other purposes would also > be of significant value. Freeing up the shuttle flights would certainly be useful. However, you are kidding yourself if you think that big expendables (the HST is *not* a small payload!) are lots cheaper. Titan IV, the probable choice, in its maximum-lift configuration costs $250M+ per flight. > > By using an ELV we would also save the cost and complexity > associated with man-rating a satellite for shuttle launch and > on-orbit servicing. Using an expendable and abandoning on-orbit servicing are quite separate issues, please note. An expendable launch means no chance of bringing the thing back down or making quick fixes in the event of a startup problem, but doesn't affect the possibility of servicing later. > > Giving up on-orbit servicing opens up the possiblity of > a geo-sync orbit with reduced operating (communications) > costs and reduced solar array/battery capacity requirements. Although it will require better radiation-hardening, since Clarke orbit is in the fringes of the outer Van Allen belt. This could be a problem for the more sensitive detectors in particular. A still higher orbit might be desirable. On the whole not a bad idea, but please note that this is going to require scaling down the telescope significantly. Not even a Titan IV could get an HST lookalike that high. > Using a commercial ELV also opens up the possibility of having NASA's >role reduced to that of a minor sub-contractor providing launch >facilities ... Um, what are you thinking of? NASA has no expendables and is not involved in launch facilities for them. On the whole, getting NASA out of the telescope business is probably a good idea. But one should not underestimate the hassle and time involved in that rearrangement of funding. NSF is not used to funding space projects, especially big ones. In retrospect, a series of smaller telescopes funded by NSF and launched by expendables to high orbit is probably a better way to go than HST, other things being equal. But other things are *not* equal. It would be quite reasonable to start on such a program now, as HST's replacement, because it's going to take much of HST's working life to get such a program off the ground. It's not a good reason for abandoning HST repairs. Sure, a determined and well-run program could get results much more quickly. But nobody is going to fund one. -- "Read the OSI protocol specifications? | Henry Spencer @ U of Toronto Zoology I can't even *lift* them!" | henry@zoo.toronto.edu utzoo!henry
mario@cs.man.ac.uk (Mario Wolczko) (02/12/91)
If there is no possibility of the HST ever being brought back for service/repair, why was a second main mirror made? Are there any plans to use it? Are there backups for any other major components? Mario Wolczko ______ Dept. of Computer Science Internet: mario@cs.man.ac.uk /~ ~\ The University uucp: mcsun!ukc!man.cs!mario ( __ ) Manchester M13 9PL JANET: mario@uk.ac.man.cs `-': :`-' U.K. Tel: +44-61-275 6146 (FAX: 6280) ____; ;_____________the mushroom project___________________________________
p515dfi@mpirbn.mpifr-bonn.mpg.de (Daniel Fischer) (02/14/91)
In article <2138@m1.cs.man.ac.uk> mario@cs.man.ac.uk (Mario Wolczko) writes: >If there is no possibility of the HST ever being brought back for >service/repair, why was a second main mirror made? Are there any >plans to use it? Are there backups for any other major components? The back-up mirror was made by another company (Kodak) - NASA's management insisted on that (actually Perkin-Elmer was ordered to have Kodak make it) because it considered the main mirror a very critical part (they were right, weren't they...). Then they looked on the test data for both mirrors and decided (as rumors go, against the advice of many knowledgable astronomers) to take P-E's. *Why* that happend it told in part in the Allen report, but the full story is still shrouded in mystery. Anyone knowing more? Plans to use it? Well, some astrophysicists called for its use some years ago: they wanted to build and HST-2 and send it right to GSO. Unfortunately their statement (published in NATURE) didn't say who should pay... :-( Question No.3: yes, there are - about 90% of the HST components are designed for in-orbit replacement, esp. the solar arrays, batteries and moving parts. E.g. a failed attitude control gyro will be replaced during the first H.S.T. Revisit mission in late 1993.