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#160
by
Sparky
on 31 Jan, 2010 02:18
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Also what purpose would a Pirs-return mission serve? What use would it provide on the ground? How about you take a progress in 2011 dock it to Pirs before MLM arrives, and take Pirs a few hundred miles out, and re-dock it to MLM. Only problem with that is that a Progress might not have enough fuel to rendezvous and re-dock.
Orbiter
Questions:
Would it be easier (or possible) to temporarily move Pirs from Zvezda nadir to Zvezda aft until Nauka arrives? I don't know if the interfaces are much different, but, assuming that there is no Progress or ATV during that period, would it be doable?
If so, would you even need a Progress to move it, or could you use assets already on station to do it?
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#161
by
Danderman
on 31 Jan, 2010 06:00
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A quick no. Pirs' active docking port is hybrid, whereas Zvezda aft is probe and cone. They don't fit together.
In theory, the Pirs passive port, which is probe and cone, could be converted to an active port, via IVA, but then a Progress could no longer dock with Pirs. Since only a Progress could even in theory move Pirs around where the ISS RMS cannot reach. the whole concept falls apart.
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#162
by
Sparky
on 01 Feb, 2010 04:55
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A quick no. Pirs' active docking port is hybrid, whereas Zvezda aft is probe and cone. They don't fit together.
In theory, the Pirs passive port, which is probe and cone, could be converted to an active port, via IVA, but then a Progress could no longer dock with Pirs. Since only a Progress could even in theory move Pirs around where the ISS RMS cannot reach. the whole concept falls apart.
So I take it that even in order to dock to the MLM, Pirs would have to be modified considerably, am I right?
Are there really no other ways to move Pirs, even without docking with a Progress? Understood, there aren't many grapples on Pirs or the Russian Segment for that matter, but hypothetically, could Pirs be "grabbed" by Dextre, which would be grappled by the OBSS, which would be grappled by Canadarm2 from the US segment? Or, barring that, Could the Strella cranes be a) moved to either Zarya or Zvezda, and used to "pluck" Pirs off until MLM arrives, or b) left on Pirs, but used remotely to "walk" Pirs across the station.
It just seems like a waste to me, to deorbit a perfectly good pressurized module, storage compartment, as well as an auxiliary airlock, after so much was spent getting it up there.
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#163
by
Jim
on 01 Feb, 2010 11:09
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but hypothetically, could Pirs be "grabbed" by Dextre, which would be grappled by the OBSS, which would be grappled by Canadarm2 from the US segment?
There is nothing for Dextre to grab on to. It does not have generic grapples. Everything, it is to grab has special fixtures. Also, the OBSS has no electrical interface for Dextre nor end effectors. There is nothing for Dextre to grab on to.
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#164
by
Danderman
on 01 Feb, 2010 14:52
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So I take it that even in order to dock to the MLM, Pirs would have to be modified considerably, am I right?
Are there really no other ways to move Pirs, even without docking with a Progress? Understood, there aren't many grapples on Pirs or the Russian Segment for that matter, but hypothetically, could Pirs be "grabbed" by Dextre, which would be grappled by the OBSS, which would be grappled by Canadarm2 from the US segment? Or, barring that, Could the Strella cranes be a) moved to either Zarya or Zvezda, and used to "pluck" Pirs off until MLM arrives, or b) left on Pirs, but used remotely to "walk" Pirs across the station.
It just seems like a waste to me, to deorbit a perfectly good pressurized module, storage compartment, as well as an auxiliary airlock, after so much was spent getting it up there.
I can't remember if the 3 ton mass of Pirs is over Dextre load limits, so I cannot answer that question.
Also, your original question dealt with moving Pirs to Service Module aft, which is out of the question.
Last point: could the ISS RMS access and move Pirs. The answer is: probably, especially if the PGDF is installed on FGB (I believe this is a requirement for some MRM-1 operations). There are hard points on Pirs that could be fitted with grapple fixtures via EVA, or the Strela base points could be used.
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#165
by
Sparky
on 02 Feb, 2010 20:18
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Also, your original question dealt with moving Pirs to Service Module aft, which is out of the question.
I was just trying to think of a place to put it until MRM arrives, and only for a few days. For all it matters, you could strap it to the side of the FGB. Once it arrives with the ERA, that could be used to rettach Pirs.
Last point: could the ISS RMS access and move Pirs. The answer is: probably, especially if the PGDF is installed on FGB (I believe this is a requirement for some MRM-1 operations). There are hard points on Pirs that could be fitted with grapple fixtures via EVA, or the Strela base points could be used.
So is using the Strela themselves out of the question?
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#166
by
Jim
on 03 Feb, 2010 00:07
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#167
by
daniela
on 03 Feb, 2010 02:40
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I was just trying to think of a place to put it until MRM arrives, and only for a few days. For all it matters, you could strap it to the side of the FGB. Once it arrives with the ERA, that could be used to rettach Pirs.
Would not want a module potentially loose when a docking is occurring! It seems to me there is no way, short of docking a Progress to Pirs, getting it safely out of the way, and then re-docking it (where? to MRM that just arrived? does it not take some EVA to outfit the port and enable docking?) I am not sure if that is feasible and at what cost. I am also not sure if there are good enough reasons to go through the trouble.
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#168
by
Danderman
on 03 Feb, 2010 22:32
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I was just trying to think of a place to put it until MRM arrives, and only for a few days. For all it matters, you could strap it to the side of the FGB. Once it arrives with the ERA, that could be used to rettach Pirs.
Please don't try that.
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#169
by
Danderman
on 03 Feb, 2010 22:32
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Would not want a module potentially loose when a docking is occurring! It seems to me there is no way, short of docking a Progress to Pirs, getting it safely out of the way, and then re-docking it (where? to MRM that just arrived? does it not take some EVA to outfit the port and enable docking?) I am not sure if that is feasible and at what cost. I am also not sure if there are good enough reasons to go through the trouble.
Let's just agree that when MLM arrives, Pirs needs to be far away from ISS.
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#170
by
Sparky
on 04 Feb, 2010 00:59
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Would not want a module potentially loose when a docking is occurring! It seems to me there is no way, short of docking a Progress to Pirs, getting it safely out of the way, and then re-docking it (where? to MRM that just arrived? does it not take some EVA to outfit the port and enable docking?) I am not sure if that is feasible and at what cost. I am also not sure if there are good enough reasons to go through the trouble.
Let's just agree that when MLM arrives, Pirs needs to be far away from ISS.
Oooo! What if you used the Progress to put Pirs on MLM BEFORE it got to ISS!Agreed.
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#171
by
daniela
on 04 Feb, 2010 15:57
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Not sure why you crossed out your words, perhaps because you think they are not feasible? I think the same. Sure one can rendezvous a Soyuz with Pirs and a Soyuz with the new module; then what? Would you trust docking that "thing" to ISS, with Kurs or even manually? Especially at the speed / impulse that is necessary for Russian docking?
I think one could dock the new module to Pirs, if one really wanted to. Would there be advantages to that? Yes it's some extra space, but carries a risk if Pirs would have problems before EOL of ISS, which it may.
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#172
by
Sparky
on 04 Feb, 2010 17:04
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Not sure why you crossed out your words, perhaps because you think they are not feasible? I think the same. Sure one can rendezvous a Soyuz with Pirs and a Soyuz with the new module; then what? Would you trust docking that "thing" to ISS, with Kurs or even manually? Especially at the speed / impulse that is necessary for Russian docking?
I think one could dock the new module to Pirs, if one really wanted to. Would there be advantages to that? Yes it's some extra space, but carries a risk if Pirs would have problems before EOL of ISS, which it may.
Pretty much, yes.
At first I thought it was worth keeping Pirs at the station, even if as nothing more than a storeroom. This was because I assumed that it was a simple matter of moving it out of the way until it MLM docks. I see now that this is not the case.
I just noticed that to keep Pirs at ISS began requiring progressively more and more elaborate plans, and when I caught myself thinking the whole "Pirs to MLM and then to ISS" line of thought, I realized that I was investing more emotion than logic.
Yes, I do see the values in either keeping Pirs at ISS, or returning it to Earth. Unfortunatly, it would seem that keeping it at ISS is prohibitivly dangerous/difficult, and it does not appear that NASA plans to return it on any of the shuttle missions. Although, I am not yet convinced that if someone wanted it badly enough, NASA couldn't engineer a way to fit it in the payload bay of a returning shuttle. The issue, however, seems to be that nobody (at least to my knowledge) DOES want it that badly. It doesn't matter whether or not we see the value. It only matters if someone who sees that value is willing to pay for it.
As much as it pains me to say so, unless somebody flies a vehicle with COTS-C capability to ISS big enough to carry Pirs before December 2011, the best plan seems to be to deorbit it.
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#173
by
daniela
on 04 Feb, 2010 17:57
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I am unsure why would it be interesting to return it on earth, it seems to me that whatever value and usefulness it has, it is in orbit. We have had ample opportunities to study hardware that was exposed to long periods in space. In regards to talks of deorbiting ISS because of the aging of the Russians segment, the Russian partners say that, if it should come to that, they are prepared to detach their segment and keep it functional; it is the USA partners that are / were considering deorbiting ISS because of operational costs. But, it appears that Obama will not be walking that path and will keep ISS operational to 2020 and likely beyond.
It would probably be possible to design adaptors to mate MLM and Pirs, then again one needs to come up with good reasons to do so and go through the bother and the expense. Yes a storeroom is always useful, but just how much are we prepared to spend for it? Also, we are talking here of permanent docking, it's not that the hybrid ring must allow MLM and Pirs to connect for a few days. It must be certified to last for expected ISS life (or should I say, Russian segment expected life), with very stringent bounds on leak rates and all other parameters. I don't see how this can be done relatively quickly, that is to say, before the MLM is launched.
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#174
by
Danderman
on 06 Mar, 2010 18:14
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#175
by
Sparky
on 07 Mar, 2010 05:35
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Just throwing an idea out there:
Assuming that putting Pirs on the Shuttle can't/doesn't happen, wouldn't this be a wonderful opportunity to test inflatable heat shield technology? Could something like a balute be attached to to Pirs via a modified Progress and deorbited?
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#176
by
arkaska
on 07 Mar, 2010 08:23
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But do you want to test that technology over an populated area? What if it fails? Most likely it will be tested over an ocean and then Pirs will be lost anyway.
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#177
by
hop
on 07 Mar, 2010 20:35
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Assuming that putting Pirs on the Shuttle can't/doesn't happen, wouldn't this be a wonderful opportunity to test inflatable heat shield technology? Could something like a balute be attached to to Pirs via a modified Progress and deorbited?
If you really want it back, you aren't going to want to rely on an untested technology to do the job.
If you just want to do the technology test, it will be much easier and cheaper to do it with a smaller, purpose built test article. Adding everything need to land Pirs intact would be difficult and expensive. For the price of returning Pirs, you could fly many smaller missions (starting with sub-orbital shots, moving up to something like Raduga that acutally returns useful cargo) until you got it right. Then you can think about returning module sized objects, although realistically you'd probably only do it with ones that were designed from the start to be returned this way.
Of course the reality is that Pirs is just 3 tons of trash once it's mission is over, and the idea that anyone would pay the hundreds of millions required to bring it back is completely absurd.
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#178
by
Sparky
on 07 Mar, 2010 20:48
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But do you want to test that technology over an populated area? What if it fails? Most likely it will be tested over an ocean and then Pirs will be lost anyway.
Well, it's not as if Soyuz vehicles don't touch down on land. Not to mention that the space agencies of the world haven't shown a whole lot of concern where or on what their boosters land, anyway. But, let's say that you wanted to be extra careful. I'm guessing that a ballute reentry system might have different flight path than a soyuz, so you might not choose to land it on the steppes of Kazakhstan for fear of miscalculating and putting it in a suburb or Moscow or Tehran. So the Oceans it is.
Why would it be lost? Pirs would be nestled at the center of a large, inflatable balute. A recovery vessel could just pick it up. But, of course, what if it deflates when it hits the surface of the ocean? Well, according to astronautix, Pirs weighs 3600 kilograms, is 4.1 meters long and 2.6 meters wide. It is, of course, an ovoid, so that it is only that wide at its middle. Let's say that that the average width rounds down to about 2m, and the length is 4m.
(πr
2)*L
3.14*1
2 * 4m = 12.57m
3Density = Mass/Volume
3600kg/12.57m
3 = 286.40kg/m
3= The density of Pirs
The density of fresh water is 1000kg/m
3, and sea water is even denser. Pirs should be able to float, so long as it doesn't take on water. Slap a radio beacon onto it, and recovering it should be a cinch.
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#179
by
arkaska
on 07 Mar, 2010 20:54
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I'm not that involved in how the inflatable heat shield work. But as you sad it would be a good way to test the technology which means extra precautions need to be taken that's why I suggested an ocean landing, maybe there are large uninhabited areas on land where it can land. Soyuz is a reliable return vehicle and can't be compared to the test of a new system.
You have to remember the equipment inside Pirs when calculating it's weight. I'm sure there are equipment which they plan to stay in Pirs as they de-orbit it.
