I wanted to bring up this topic. Nasa is getting set to announce the next servicing mission to Hubble. This got me thinking that the shuttle is a great platform for servicing missions. How would something like that be done after the shuttle is retired once we are in the CEV era? <br /><br />My own thoughts were Nasa could develop a servicing payload. It would be a structure that would include an attachment base, tools, parts and anything needed for that particular servicing mission. It would be launched on a expendable rocket such as Delta 4. Then the CEV, launched seperately, would dock with it and use it's propulsion system to rendevous and capture the target satellite. After the mission is over, the service structure would be discarded. Or perhaps it could be reused but I would think that would be difficult.<br /><br />Does anyone want to speculate here?<br />
- Status
About the only spacecraft left that has been serviced was the Hubble telescope. As Hubble nears the end of its service life, there will probably be only one or two servicing missions although I don't recall the status of any servicing missions. They were going to cancel them last I remember. Servicing other satellites had already been abandoned once shuttle missions were strictly limited to building ISS and maybe servicing Hubble.<br /><br />The expense of servicing missions is another problem. Its generally cheaper to build satellites with high reliability that require virtually no servicing over there life times than it is to design and build serviceable satellites.<br /><br />The service structure you mentioned in your scenario could not be brought back to earth for reuse, therefore it would be more expensive because you'd have to throw them away after each use. I could see maybe taking a limited amount of items, perhaps a black box, to install or R & R using just the CEVs capability. The CEV will be much less capable than shuttle was for this role but a limited repair mission is possible in an emergency. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>
<font color="yellow">Its generally cheaper to build satellites with high reliability that require virtually no servicing over there life times than it is to design and build serviceable satellites. </font><br /><br />Well -- it's actually worse than that. The satellites that are the most expensive and for which servicing missions would conceivably be useful happen to be those satellites that get placed into GEO. The shuttle as an LEO craft could never have gotten to them, and even for future craft (at least for the forseeable future), getting there would raise the expense of servicing to the point that replacing the satellite is cheaper.<br /><br />Even the Hubble's orbit was deliberately made low enough for the shuttle to service (at the expense of degrading its performance). The shuttle as a satellite servicing platform was NASA PR that never really stood up to close scrutiny.
I've explored this issue somewhat in a story I'm writing, the conclusion I came to was that a berthed "toolbox" would be most useful. This would dock to a capsule (soyuz clone) and contain a forward hatch, side airlock, human tools, a small robot arm, etc. The toolbox travels with the capsule, performs it's function then returns to a station via capsule or tug. It really only makes sense if it's fully reusable, or a very high-value satellite to fix. In the story, this is part of the kit of a station-outfitting company. While potentially usable for satellite repair, these sorts of custom add-ons would really shine for enabling humans-in-space. <br /><br />On Hubble, I support the soonest servicing mission possible, I hope they move to Dec 2007. However, it is past time to build and fly a true Hubble 2 incorporating lessons learned. I'm not talking about the Webb Telescope or others planned, but a true successor to Hubble, specialized in the same spectra, modular, upgradable etc. If we could fly 5-10 Hubble2 telescopes in solar orbit, we'd have a serious interferometer.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>
An orbital service module could be launched on an ELV, then CEV could dock with it and proceed to the satelite to service. After the mission the service module would be left attached to the satelite or station keep nearby so that it could be used in future servicing missions.<br /><br />Here's an interesting article about servicing hubble via ISS. http://www.aura-astronomy.org/nv/hubble.pdf#search="hubble%20inclination"<br /><br />Future satelites intended for service could also orbit at the ISS' inclination so they can be brought down to the ISS for service.
My understanding is that the current Hubble servicing mission plans include the shuttle leaving a LIDS docking adapter on the Hubble to allow future docking with the CEV.
<font color="yellow">"...the next servicing missio leaves a de-orbit motor..."</font><br /><br />I seldom argue with you about shuttleish things... but I'm pretty sure you're wrong on that one. My understanding was that the DO booster is completely separate from the servicing mission. I know that *originally* it was intended to be a robotic mission (one which predates and is unrelated to the robotic servicing mission). A DO booster is not mentioned in the SM4 documentation:<br /><br />
Here's something that DARPA's been cooking up called Orbital Express<br /><br />Basically DARPA is experimenting with orbital servicing of it's spy satellites, and since Hubble is a sort of reverse engineered KH-11, this might be applicable. <div class="Discussion_UserSignature"> <p> </p><p><em>So, again we are defeated. This victory belongs to the farmers, not us.</em></p><p><strong>-Kambei Shimada from the movie Seven Samurai</strong></p> </div>
<font color="yellow">"we will see who is right ..."</font><br /><br />Deja vu. We had this conversation before. You indicated at one point that the shuttle was low on dv to bring the DO module up on the SM4 flight. I referenced your statement about that in a later thread. You denied making the statement, at which point I found it and added a link to it. Link to the thread with said link pointing to dv statement here. <br /><br />Of course in the linked thread there was considerable discussion afterward indicating that the shuttle *should* have the dv, and no ideas came out on why the DO module wasn't listed as part of SM4. <b>Originally</b>, it was supposed to have been added as part of a closeout mission in 2010.<br /><br /><br />I can't remember to take out the garbage two days in three, but dangit, my memory for technical trivia is phenomenal. Mind you -- my wife would much prefer that I devoted more neurons to the garbage... <img src="/images/icons/smile.gif" />
mrmorris:<br />Well -- it's actually worse than that. The satellites that are the most expensive and for which servicing missions would conceivably be useful happen to be those satellites that get placed into GEO.<br /><br />Me:<br />Thats correct, forgot to mention that. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>
Is the deorbit engine big enough to boost the orbit instead? There are a lot of people here that favor putting Hubble into some sort of high parking orbit where it could be left for decades so it could be retrieved. If not, how big of an engine would be required? <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>
I would think a lot bigger. All it takes is a nudge to start down and gravity does the rest. To go up you have to counteract gravity, add more DV then needed to begin with to arrive at a given point after everything is done, which requires less DV than it took to get there. <div class="Discussion_UserSignature"> </div>
To transfer an object from a 185 km x 185 km to a 593 km x 593 km orbit requires two engine burns. The deltaV for each burn is 0.1158 km/s. This orbit provides approx 200 years before it burns up.<br /><br />So a dV capability of 232 m/s is needed to put it into that mothball orbit.<br /><br />Starting from that same 185 km circular orbit, a single burn of dV=46.4 m/s would put your new perigee at 31 km, my best guess at a fiery re-entry trajectory.<br /><br />So for lack of our generation's ability to invest an additional 185 m/s of dV to avoid trashing perhaps the most significant scientific instrument of all time, future generations will have no opportunity to go fetch the thing and put it in a museum. I'm still hoping that Dr. Griffin's NASA won't make that selfish decision. <br /><br />Perhaps the de-orbit module is the prudent approach, as pieces of space telescope coming down randomly cannot be permitted. And maybe the module is already too far along to add the dV capability. But at least provide some capability for a future craft - perhaps even the CEV - to grapple the HST/deorbit module stack and save the Hubble for future generations! Don't decide to trash it until you have to! <div class="Discussion_UserSignature"> </div>
abadger,<br /><br />We naturally assume that, as our mastery of space improves, we will begin to repair satellites, instead of replacing them. However, until the cost of launching people comes down substantially, it is cheaper to replace the satellite than it is to send someone up to fix it. Especially when the satellite is in the Clarke (geosychronus) Orbit, because it is so much higher than Low Earth Orbit. We have to learn how to get into space cheaply, and safely, which means a lot of changes from how we do things now. Then, we have to learn how to use off-planet resources to create propellant, so that we will not have to keep lifting it out of this gravity well. But at some point in time, I believe that we will have vehicles which are capable of moving from orbit to orbit carrying a payload, and when that time comes, we will start making our satellites servicable. Considering that the most common reason for taking satellites out of service is loss of station keeping ability, due to propellant for the Reaction Control System running out.<br /><br />But we have a long way to go before it will be affordable to send a service team after a satellite. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>
Well stated halman, I would only add that there have been proposals for three decades or more regarding satellite repair capability that have never been developed. The space tug proposal of 1973. The OMV from about 1990 to name two that come to mind. The OMV was a scaled down version of the 1980s OTV proposal. OTV was manned IIRC and OMB was unmanned. The reason these proposals were never developed beyond the study stage are pretty much the ones you already mentioned. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>
<font color="yellow">"To transfer an object from a 185 km x 185 km to a 593 km x 593 km orbit requires two engine burns. The deltaV for each burn is 0.1158 km/s. This orbit provides approx 200 years before it burns up. "</font><br /><br />Dunno if these are just dv calcs you had handy or what... Hubble is already in a ~569 km orbit. S'why the shuttle can just barely reach it. <img src="/images/icons/smile.gif" />
For a really big servicing mission (if one were actually needed in the CEV era) I suppose you could launch one crewed Orion and one of the unmanned cargo versions fitted out for the particular job.
Probably not a feasible idea, but I'd like to see us develop some sort of craft that would attach to the ISS for storage, but allow our astronauts to "travel around" a bit. They could do servicing missions on satelights/etc, as needed, then dock back with the station. Might even be able to be a source of income, servicing satelights already in orbit. It would save the companies money, by prolonging the lifespan of the systems already in space, allowing upgrades/repairs to be made, instead of having to launch whole new systems. Current crews probably wouldn't have time to do all that in addition to their normal tasks, but might be a future possiblity. Perhaps one of the new Bigelow modules would allow this type of enterprise.<br /><br />Rae
Hmm all these posts are very good. So I can draw two conclusions from this.<br /><br />1. As cost to orbit per pound get cheaper (spacex, etc...), and satellites get smaller (microsats) it is more economical to make satellites expendable than to service them.<br /><br />2. The space shuttle is really about 50 years ahead of its time. <img src="/images/icons/smile.gif" /><br /><br />I can still see a need to reach high orbit in order to clear out satellites that are no longer useful or functional. For that however I am pretty sure an unmanned system would work nicely.<br /><br />
<font color="yellow">Dunno if these are just dv calcs you had handy or what... </font><br /><br />Ah geez, that's what I get for multi-tasking with orbital mechanics as one of the tasks. Ooops. And all I was doing was lifting previous material. <img src="/images/icons/rolleyes.gif" /> <img src="/images/icons/blush.gif" /><br /><br />That back-of-napkin calc is offered solely as a demonstation that a mothballing orbit is well within current capabilities. It is not a mission proposal.<br /><br />The idea was to point out that we can put X lbs into LEO with a current launcher, and that payload would have plenty of mass margin to transfer up to Hubble, grapple it, then transfer itself and HST up to a ~1113 km orbit. There is still ample mass margin for this rather inefficient and brute force method of getting the job done. <div class="Discussion_UserSignature"> </div>
I was trying to put it more in perspective as simply as possible. <br /><br />I have always agreeded bringing Hubble back for display would be an ideal situation. What I would really like to see is the last Shuttle mission taking up Hubble 2 and bringing back Hubble. I would think another copy could be built in 5-6 years and improved with the latest technology . I'd even pay a few dollars for every Hubble image I have in my computer to fund a replacement. <div class="Discussion_UserSignature"> </div>
Also, I'm not sure that, weight wise, the shuttle could land with the Hubble Telescope on board. It already flies with the handling characteristics of a brick.<br /><br />Instead why not have a shuttle attach a rocket pack to boost the telescope into a higher and safer orbit until a better final solution can be found. Like taking it to the moon and mounting it on the far side as a permanent observatory. <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>
I don't think that Hubble can operate in a gravity field. In fact the original problem with the optics stemmed from the fact that Earth based telescope mirrors are designed to account for distortion caused by gravity making the mirror sag. These compensation factors were accidently left in the calculations for the Hubble's main mirror. Then again Hubble was fixed by adding a set of corrective lenses, maybe they could be swapped out for a set that could compensate for lunar gravity. Probably more trouble than it is worth though.
Among the multitude of additional reasons why this is unworkable:<br /><br />-- There's no way to point it if it were on the lunar surface.<br />-- It can't survive the 300+ hour day/300+ hour night cycle of the moon.<br />-- If it *could* survive that -- the times when it would actually be getting sunlight on its solar panels would be the times when it's facing the sun... making observations dicey. The 'night' would be best for observation but it would have only battery power to work with.<br />-- It's *old* and we've already seen parts start dying outside of the ones SM4 will *hopefully* replace.<br />-- Soft-landing it on the moon is just a <b>wee</b> bit hard.
All, FYI, the mothball proposal assumes that we have a dead telescope. At some point, the cooling fails, and some of/most of/all of (??) the instruments fry, and it will not be performing full science operations again. The question is what you do with it at that point.<br /><br />Apparently the cold scientific minds involved so far see no alternative to destroying the artifact which remains.<br /><br />My point is that the artifact has value. Preserving that value for future generations is an obligation on our generation. (I scarcely believe that I have to make the case.)<br /><br />In fact, my ultimate goal is to put the most significant scientific instrument of all time on the lunar surface, in an indoor facility for all there to admire. Not even this wild-eyed optimist supposes that's going to happen any time soon: a heckuva lot of capability and determination is required to make that happen. YET . . . if we make that the goal . . . think about the power of the concept of 'The Future of Hubble': it's sitting up there in a mothball orbit just waiting for our technology to advance to the point where it can be rescued.<br /><br />Or, we can burn the thing up and settle for the cheapest possible responsible solution.<br /><br />Or, some plan in between. But let's keep our options open!<br />***<br />[I apologize for any perceived thread hijacking; the issue merits it and the title question seems to be asked and answered. Plus, at least in my mind it is in fact OT. 
]<br /> <div class="Discussion_UserSignature"> </div>
]<br /> <div class="Discussion_UserSignature"> </div>- Status
Similar threads
TRENDING THREADS
-
-
Does a cosmic 'glitch' in gravity challenge Albert Einstein's greatest theory?- Started by Admin
- Replies: 73
-
Goodbye infinity and all that infinite singularity and infinite density descriptions
- Started by Catastrophe
- Replies: 32
-
-
Warp drives' may actually be possible someday, new study suggests
- Started by Admin
- Replies: 33
-
In the Milky Way, 3 intruder stars are 'on the run' — in the wrong direction
- Started by Admin
- Replies: 4
-
Facebook
Twitter
Instagram