 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| HomeDiscussion GroupsSpace ScienceAstronomyAmateur AstronomySpace FlightSpace StationShuttleSpace HistorySpace PolicySETI SpaceKB.com Contact UsLink To UsSearch & Site Map |
Space Forum / Shuttle / February 2005NYT: Death Sentence for the Hubble?
http://www.nytimes.com/2005/02/13/opinion/13sun2.html? Death Sentence for the Hubble? Published: February 13, 2005 Sean O'Keefe, the departing administrator of the National Aeronautics and Space Administration, has yanked the agency's most important scientific instrument off life support. His refusal to budget any funds to service and upgrade the Hubble Space Telescope looks like the petulant final act of an administrator who made a foolish decision and then refused to back down in the face of withering criticism from experts. The only uncertainty is whether the decision to let the Hubble die prematurely was solely Mr. O'Keefe's or reflects the judgment of higher-ups in the administration that servicing the Hubble would be a diversion from the president's long-range program of space exploration. -end excerpt-  Signaturerk, Just an OldEngineer "Engineers abhor extrapolation" -- Ken Iliff, from _Runway to Orbit_, 2004 >Sean O'Keefe, the departing administrator of the National Aeronautics and >Space Administration, has yanked the agency's most important scientific [quoted text clipped - 3 lines] >face of withering criticism from experts. > If the repair mission costs as much as building a new telescope, then we should build a new telescope using updated technology. This time with a mirror that's ground correctly. Improved ground based telescope resolution has taken away a lot of Hubble's necessity. Pat Well... If one want a regular serviceable telescop, one might as well stuck a telescope at the I.S.S., just like Skylab. It should be noted that a 600 km orbit is not the best orbit for a space telescope. That's why some space telescopes are put in the Sun-Earth L1 (for observing the sun) and L2 (for observing outerspace). As for Hubble. The problem lies in Hubble's re-entry back to Earth. There are several ways on what could happen: - Uncontrolled re-entry back to Earth. A good way to ruin N.A.S.A.'s reputation. And I'm affraid that this is what might happen, since that in recent times, there are people that out there to ruin N.A.S.A.'s reputation and also the reputation of the government of the U.S.A., either doing it from the outside or from the inside. - Controlled re-entry back to Earth. Might not be so dark as the first option, but would be good enough to ruin a reputation. Just like what 'they' did to Mir. - Bring it back to Earth and then put it in a museum. A nice retirement for Hubble. I prefer it this way. - Service the Hubble. A waste a money, since it's much better to build a newer and much improved space telescope. > Well... If one want a regular serviceable telescop, one might as well > stuck a telescope at the I.S.S., just like Skylab. Doesn't work, too many vibrations due to crew movement. What might work, however, is to have it attached via tether using the gravitational gradient to keep it in place. Maybe. > Doesn't work, too many vibrations due to crew movement. What might work, > however, is to have it attached via tether using the gravitational gradient > to keep it in place. Maybe. Assuming a Hubble-class instrument: Nope. First: The vibrations will travel down the cable from ISS to the telescope. There's nothing about tidal effects to damp down transient vibrations from crew movement... at least in a time frame that would do the 'scope any good. Second: ISS is a dirty place to hang around outside for for long, if you're high-quality optics, and is definitely in a low-rent neiborhood orbit-wise SignatureChuck Stewart "Anime-style catgirls: Threat? Menace? Or just studying algebra?" >Doesn't work, too many vibrations due to crew movement. What might work, >however, is to have it attached via tether using the gravitational gradient >to keep it in place. Maybe. Assuming the tether was taut, vibrations might propagate down it also; to get it completely vibration free, it will probably have to be free-flying. The Russians had that failed remote operator freeflyer go into orbit around Mir due to Mir's microgravity field... could some sort of an ISS/Earth Lagrange point exist? Pat >could some sort of an > ISS/Earth Lagrange point exist? The third body has to be of insignificant mass as compared to the other two- the freeflyer represented a substantial mass compared to Mir, when Mir is compared to Earth. >The third body has to be of insignificant mass as compared to the other two- >the freeflyer represented a substantial mass compared to Mir, when Mir is >compared to Earth. > I still think the slightly out of phase orbits at the same inclination that intersect at long intervals (say a year or so) is a good idea. When the station and telescope are close together, a maintenance mission with low delta V can be accomplished, while still keeping the station and shuttle (or whatever replaces it) from interfering with the telescope most of the time. Pat > I still think the slightly out of phase orbits at the same inclination > that intersect at long intervals (say a year or so) is a good idea. > When the station and telescope are close together, a maintenance mission > with low delta V can be accomplished, while still keeping the station > and shuttle (or whatever replaces it) from interfering with the > telescope most of the time. Wouldn't work. ISS, at least, and telescopes are fundamentally incompatable. ISS has to have a low orbit due to the limitations of Soyuz / Progress, and launch systems in general. Frequent reboosts aren't much of a problem because supply and ferry ships dock frequently. However, a telescope in an orbit with such a low lifetime would also need frequent reboosts, which would require a lot of onboard propellant and frequent usage of some sort of thruster. Things which are not terribly compatable with high precision optical astronomy equipment, though it's not completely out of the question. >...However, a telescope in an orbit with such a >low lifetime would also need frequent reboosts, which would >require a lot of onboard propellant and frequent usage of some >sort of thruster. Things which are not terribly compatable >with high precision optical astronomy equipment... No, it just means you have to choose propulsion systems carefully, avoiding orthodox hypergolics and other systems which spew out condensible garbage that can easily contaminate optics. Xenon Hall-effect thrusters or an ammonia arcjet would be good choices. Signature"Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | henry@spsystems.net >>...However, a telescope in an orbit with such a >>low lifetime would also need frequent reboosts, which would [quoted text clipped - 6 lines] > garbage that can easily contaminate optics. Xenon Hall-effect thrusters > or an ammonia arcjet would be good choices. True, which is why I did not *completely* rule out the option. Of especial note is that such efforts come with rather sizeable down sides (and price tags). Low thrust propulsion requires nearly continual operation to maintain a low orbit. This comes at a cost in either sophisticated scan platforms, inconvenient pointing constraints, degraded duty cycles or all of the above (plus additional mass and complexity in power generation and processing, e.g. solar arrays and PPUs et al). Somehow, NRO manages to keep Hubble class optical surveillance satellites in pretty low orbits for a substantial period of time, so there might be a few tricks to getting away with that. Though the constraints for spysats are much different than those for space science observatories, so the experience may not be applicable (spysats never create long exposures like the Hubble deep field, for example). Of course, none of this comes for free, no matter how well it works. If manned spaceflight were significantly more routine and robust than it is today, it might be a worthwhile tradeoff. However, if it were then it would likely have the capabilities needed to service more remote installations, so the concept has something of a catch-22 built into it. >> ...just means you have to choose propulsion systems carefully, >> avoiding orthodox hypergolics and other systems which spew out condensible [quoted text clipped - 5 lines] >rather sizeable down sides (and price tags). Low thrust >propulsion requires nearly continual operation... That's why I mentioned arcjets, which are still low-thrust by chemical standards but have *much* higher thrust than Hall-effect thrusters. With them, it should be possible to do occasional corrections rather than continuous thrusting. Even resistojets would be worth considering. You don't actually *need* terribly high Isp for this; the point of the electric thrusters is more that they can run on storable non-contaminating fluids. For that matter, you ought to be able to do non-contaminating storable chemical fuels, if you picked carefully. I would guess that ClF5/NH3 would be non-contaminating. (Don't know if anyone's tried that particular combination; ammonia is notorious for being difficult to burn well because it's so stable, but ClF5 is notorious for being so ferociously active that it gives smooth combustion with anything it gets its hands on.) Signature"Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | henry@spsystems.net > For that matter, you ought to be able to do non-contaminating storable > chemical fuels, if you picked carefully. I would guess that ClF5/NH3 > would be non-contaminating. (Don't know if anyone's tried that particular > combination; ammonia is notorious for being difficult to burn well because > it's so stable, but ClF5 is notorious for being so ferociously active that > it gives smooth combustion with anything it gets its hands on.) Including the telescope? :) SignatureChuck Stewart "Anime-style catgirls: Threat? Menace? Or just studying algebra?" >> chemical fuels, if you picked carefully. I would guess that ClF5/NH3 >> would be non-contaminating. (Don't know if anyone's tried that particular [quoted text clipped - 3 lines] > >Including the telescope? :) That's definitely a combination you want to run fuel-rich. :-) Handling ClF5 is, shall we say, a "zero defects" kind of operation. Never mind fuels; the stuff is hypergolic with all normal fire-extinguishing agents... (The recommended firefighting procedure for a ClF5 fire is to take cover at a safe distance. Quickly.) Signature"Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | henry@spsystems.net >>> chemical fuels, if you picked carefully. I would guess that ClF5/NH3 >>> would be non-contaminating. (Don't know if anyone's tried that particular [quoted text clipped - 9 lines] > mind fuels; the stuff is hypergolic with all normal fire-extinguishing > agents... And all normal Fire Fighters. > (The recommended firefighting procedure for a ClF5 fire is to take cover > at a safe distance. Quickly.) AS it said on the back of my Duracell Abuse Testing T-Shirt: "If you see me running, try to keep up" SignaturePete Stickney p-stickney@nospam.adelphia.net Without data, all you have are opinions > > (The recommended firefighting procedure for a ClF5 fire is to take cover > > at a safe distance. Quickly.) > > AS it said on the back of my Duracell Abuse Testing T-Shirt: > "If you see me running, try to keep up" In the outdoors people often ask me how fast they have to run to be safe from a bear attack. I simply point out they have to only outrun me. >> > (The recommended firefighting procedure for a ClF5 fire is to take cover >> > at a safe distance. Quickly.) [quoted text clipped - 4 lines] > In the outdoors people often ask me how fast they have to run to be safe > from a bear attack. I simply point out they have to only outrun me. That's why I always keep a pair of sneakers (ObCommonwealth: Trainers, ObRAF: Rubber-soled Brothel Creepers) in my pack. SignaturePete Stickney p-stickney@nospam.adelphia.net Without data, all you have are opinions > That's why I mentioned arcjets, which are still low-thrust by chemical > standards but have *much* higher thrust than Hall-effect thrusters. > With them, it should be possible to do occasional corrections rather > than continuous thrusting. Are there arcjets large enough for this task? I was under the impression that there were none large enough for main propulsion tasks. Although for simple orbital maintenance, something that large might not be needed. > Even resistojets would be worth considering. You don't actually *need* > terribly high Isp for this; the point of the electric thrusters is more > that they can run on storable non-contaminating fluids. Agreed (or solids, of course). And perhaps solar sails or electrodynamic tethers, though those are much less easily compatible with telescope operation than even ion engines. >> That's why I mentioned arcjets... > >Are there arcjets large enough for this task? I was >under the impression that there were none large enough >for main propulsion tasks. Although for simple orbital >maintenance, something that large might not be needed. Some quite large ones have been tested, although not recently. The off-the-shelf ones *are* small, but you could use a cluster of them. >> Even resistojets would be worth considering. You don't actually *need* >> terribly high Isp for this; the point of the electric thrusters is more [quoted text clipped - 3 lines] >electrodynamic tethers, though those are much less easily >compatible with telescope operation than even ion engines. Solar sails almost certainly can't be made to work for this because of air drag. Except in very favorable circumstances, it's difficult to get an excess of thrust over drag with a solar sail below 1000km or so. Electrodynamic tethers are a possibility, although as you say, making them compatible with telescope operations would be tricky. Signature"Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | henry@spsystems.net > Wouldn't work. ISS, at least, and telescopes are fundamentally > incompatable. ISS has to have a low orbit due to the limitations [quoted text clipped - 6 lines] > with high precision optical astronomy equipment, though it's > not completely out of the question. I was always surprised they didn't put an ion thruster array on ISS to give it an intregal anti-orbital decay capability. The station is supposed to test out new technologies and methods, and unlike Deep Space One, you could go out and retrieve expermental ion motor arrays for examination to see how well they performed after long use. If the station ever does get to its finished form with the eight huge solar arrays in place, one would think that there would be power enough to do it. Pat > If the > station ever does get to its finished form with the eight huge solar > arrays in place, one would think that there would be power enough to do it. You'd be surprised how much power the station requires for infrastructure equipment, let alone experiments. Power was one of the three biggest design drivers of the U.S. segments (the other two being mass and volume, but power was probably number 2 on that list behind mass). Optimistic early SSF plans called for resistojets for such a purpose, using waste water and/or urine as reactant mass. Cool concept, too power-hungry for practicality in addition to being far too "messy" in terms of external contamination concerns. Heck, I had to fight nearly tooth and nail with external contamination requirements people about carbon dioxide venting. I once rhetorically asked them what they'd like the crew to do in lieu of venting - hold their breath for 90 days? Of course, with a proper CO2 reduction system, you end up with granular carbon and water, or at least methane which you can burn through those resistojets (which also don't exist). But then you add to the mass-balance surplus of water which already exists and you end up venting that, too, even if you split some of it to provide O2 replenishment. Ah, the joys of closed-loop ECLSS, where nothing ever quite works out in practice . . . SignatureHerb Schaltegger, B.S., J.D., GPG Key ID: BBF6FC1C "The loss of the American system of checks and balances is more of a security danger than any terrorist risk." -- Bruce Schneier <http://dischordia.blogspot.com> <http://www.angryherb.net> >I was always surprised they didn't put an ion thruster array on ISS to >give it an intregal anti-orbital decay capability. Unfortunately, I think you'd need a pile of thrusters, and some big new solar arrays to power them. There *were* once serious plans to fit it with resistojets, to use waste fluids as reboost propellant. That died of a combination of budget squeezes and technical difficulties. >...If the >station ever does get to its finished form with the eight huge solar >arrays in place, one would think that there would be power enough to do it. Unfortunately, most of that power is spoken for already. Signature"Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | henry@spsystems.net > I was always surprised they didn't put an ion thruster array on ISS to > give it an intregal anti-orbital decay capability. The station is [quoted text clipped - 3 lines] > station ever does get to its finished form with the eight huge solar > arrays in place, one would think that there would be power enough to do it. And if you do it right, you get better microgravity because you can cancel out the air drag with an equal and opposite amount of continuous thrust. This would completely eliminate the transient forces on the structure caused by the firing of thrusters for reboost. Jeff SignatureRemove icky phrase from email address to get a valid address. > > I was always surprised they didn't put an ion thruster array on ISS to > > give it an intregal anti-orbital decay capability. The station is [quoted text clipped - 11 lines] > > Jeff Except that atmospheric drag isn't constant. Not only does the density of the tenuous atmosphere vary, the angle (alpha and beta) of the arrays varies as well, which varies the coefficient of drag tremendously. SignatureHerb Schaltegger, B.S., J.D., GPG Key ID: BBF6FC1C "The loss of the American system of checks and balances is more of a security danger than any terrorist risk." -- Bruce Schneier <http://dischordia.blogspot.com> <http://www.angryherb.net> > > And if you do it right, you get better microgravity because you can cancel > > out the air drag with an equal and opposite amount of continuous thrust. [quoted text clipped - 7 lines] > the arrays varies as well, which varies the coefficient of drag > tremendously. So it comes down to how good can we sense very small accelerations and how fast a hall effect or ion thruster can be throttled and gimbaled. It's certainly an interesting active control system problem. Jeff SignatureRemove icky phrase from email address to get a valid address. >> Except that atmospheric drag isn't constant. Not only does the >> density of the tenuous atmosphere vary, the angle (alpha and beta) of [quoted text clipped - 3 lines] >So it comes down to how good can we sense very small accelerations and how >fast a hall effect or ion thruster can be throttled and gimbaled. The sensing is easy; perfect drag compensation was done decades ago, for the Transit navigation satellites in particular. You put a small chamber, vented to vacuum, inside your spacecraft, with a ball bearing (or whatever is convenient) floating inside it. The ball bearing is shielded from air drag by being inside your spacecraft; *it* is in perfect free fall. You maneuver the spacecraft around it to keep it centered in the chamber. Signature"Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | henry@spsystems.net >The Russians had that failed remote operator freeflyer go into orbit >around Mir due to Mir's microgravity field... could some sort of an >ISS/Earth Lagrange point exist? Not a useful one. But if the free-flyer has a little bit of maneuvering capability for small corrections, it's easy enough to set up formation flying, either both spacecraft in the same orbit (e.g. free-flyer 10km ahead of ISS) or synchronized orbits (free-flyer "orbiting" ISS, in the same plane as ISS's orbit, in an ellipse with horizontal dimension double the vertical dimension). Signature"Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | henry@spsystems.net > Not a useful one. But if the free-flyer has a little bit of maneuvering > capability for small corrections, it's easy enough to set up formation > flying, either both spacecraft in the same orbit (e.g. free-flyer 10km > ahead of ISS) or synchronized orbits (free-flyer "orbiting" ISS, in the > same plane as ISS's orbit, in an ellipse with horizontal dimension double > the vertical dimension). Of course, the MTFF (Man-tended Free Flyer) was one of the first major pieces of SSF to bite the dust due to budget cuts, lo those many years ago. SignatureHerb Schaltegger, B.S., J.D., GPG Key ID: BBF6FC1C "The loss of the American system of checks and balances is more of a security danger than any terrorist risk." -- Bruce Schneier <http://dischordia.blogspot.com> <http://www.angryherb.net> JRS: In article <1114l01c37lju5d@corp.supernews.com>, dated Tue, 15 Feb 2005 13:56:48, seen in news:sci.space.shuttle, Pat Flannery <flanner@daktel.com> posted : >The Russians had that failed remote operator freeflyer go into orbit >around Mir due to Mir's microgravity field... could some sort of an >ISS/Earth Lagrange point exist? In principle, yes. But for it to be stable I suspect that one would need to remove the Moon, very probably the Sun, probably much of the rest of the Solar System, and perhaps other nearby parts of the Universe, Or to ballast ISS up to the Teraton range or higher. Both of those seem rather drastic procedures, though there would be some economy in partially combining them. Actually, I rather doubt whether anything can orbit around a likely LEO man-made object; consider the Roche Limit. The flyer may have remained near Mir due to having a similar orbit around the Earth - but I don't recall the facts, if any. Signature© John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 MIME. © Web <URL:http://www.merlyn.demon.co.uk/> - FAQqish topics, acronyms & links; some Astro stuff via astro.htm, gravity0.htm ; quotings.htm, pascal.htm, etc. No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News. >JRS: In article <1114l01c37lju5d@corp.supernews.com>, dated Tue, 15 Feb >2005 13:56:48, seen in news:sci.space.shuttle, Pat Flannery [quoted text clipped - 13 lines] >System, and perhaps other nearby parts of the Universe, > Yes, I thought the moon and sun would be a problem. >Actually, I rather doubt whether anything can orbit around a likely LEO >man-made object; consider the Roche Limit. The flyer may have remained >near Mir due to having a similar orbit around the Earth - but I don't >recall the facts, if any. > I'm trying to dig up more info on what they did after it failed; it was called "X-Mir-Inspector". There's info on it here: http://www.ik1sld.org/inspector.htm I remember at the time they were concerned about it colliding with the station. It left the vicinity of the station according to this: http://satobs.org/seesat/Dec-1997/0204.html Pat > Yes, I thought the moon and sun would be a problem. If the sun disappeared, skin cancer would too. Bring it on! > > [quoted text clipped - 3 lines] >If the sun disappeared, skin cancer would too. Bring it on! > Spoken like a true vampire. If we got rid of the Moon also, there'd be none of those pesky werewolves to contend with. Pat :>>Yes, I thought the moon and sun would be a problem. :>> [quoted text clipped - 4 lines] :If we got rid of the Moon also, there'd be none of those pesky :werewolves to contend with. Actually, getting rid of the sun takes care of that, too. No sun, no sunlight to reflect at earth and hence no full moons. Voila. Problem solved. Actually, getting rid of the sun takes care of that, too. No sun, no > sunlight to reflect at earth and hence no full moons. Voila. Problem > solved. Ah, but is it really the moonlight or the orbital position of the full Moon? I mean why not a partial werewolf on a waxing or waning Moon? I guess the question is, do werewolves come out during lunar eclipses? Werewolf? There wolf, there castle. > http://www.nytimes.com/2005/02/13/opinion/13sun2.html? > > Death Sentence for the Hubble? > > Sean O'Keefe, the departing administrator... Could someone remind me of what the S in NASA stands for? Is it Shuttle? Station?? something else??? SignatureKevin Willoughby kevinwilloughby@acm.org.invalid The loss of the American system of checks and balances is more of a security danger than any terrorist risk. -- Bruce Schneier >> http://www.nytimes.com/2005/02/13/opinion/13sun2.html? >> [quoted text clipped - 4 lines] > Could someone remind me of what the S in NASA stands for? Is it Shuttle? > Station?? something else??? Space. SignatureJRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. >>Could someone remind me of what the S in NASA stands for? Is it Shuttle? >>Station?? something else??? >> > >Space. > Considering how it's been run since Goldin's tenure, I was going to suggest "Stupid". "National Aeronautics and Stupid Administration" has a nice ring to it. ;-) Oh well, at least the unmanned stuff seems to be working fairly well of recent. Pat >> http://www.nytimes.com/2005/02/13/opinion/13sun2.html? >> [quoted text clipped - 4 lines] > Could someone remind me of what the S in NASA stands for? Is it Shuttle? > Station?? something else??? Sean. Signaturerk, Just an OldEngineer "Engineers abhor extrapolation" -- Ken Iliff, from _Runway to Orbit_, 2004 Stupidity, I imagine. :-) Brian SignatureBrian Gaff....Note, this account does not accept Bcc: email. graphics are great, but the blind can't hear them Email: briang1@blueyonder.co.uk ______________________________________________________________________________________________________________ >> http://www.nytimes.com/2005/02/13/opinion/13sun2.html? >> [quoted text clipped - 4 lines] > Could someone remind me of what the S in NASA stands for? Is it Shuttle? > Station?? something else??? Anybody remember when the last time the NY Times editorial page was on the right side of a space policy debate? Has it EVER been? These guys are not now, and never have been, friends of space exploration and its proponents. > http://www.nytimes.com/2005/02/13/opinion/13sun2.html? > [quoted text clipped - 19 lines] > "Engineers abhor extrapolation" > -- Ken Iliff, from _Runway to Orbit_, 2004 > Anybody remember when the last time the NY Times > editorial page was on the right side of a space policy debate? > > Has it EVER been? Well, they did publish their "Oh. Yes. Um. Actually, it looks like a rocket *can* work in vacuum. Sorry about that one." retraction editorial back in 1969, so... Signature-Andrew Gray andrew.gray@dunelm.org.uk > Anybody remember when the last time the NY Times > editorial page was on the right side of a space policy debate? > > Has it EVER been? Jim, they're just trying to save us all from that foolishness of rockets in a vacuum, since we know after all there's nothing for them to push against! > These guys are not now, and never have been, friends > of space exploration and its proponents. > Jim, they're just trying to save us all from that foolishness of rockets > in > a vacuum, since we know after all there's nothing for them to push > against! Except Congress :) > "Jim Oberg" <jameseoberg@houston.rr.com> wrote in message >>These guys are not now, and never have been, friends >>of space exploration and its proponents. John Noble Wilford ("We reach the moon") was a staffer for NYT, one of the best space writers of all time, imho. SignatureTerrell Miller millerto@bellsouth.net "Every gardener knows nature's random cruelty" -Paul Simon RE: George Harrison > Anybody remember when the last time the NY Times > editorial page was on the right side of a space policy debate? [quoted text clipped - 3 lines] > These guys are not now, and never have been, friends > of space exploration and its proponents. If so, how would you explain it? |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.