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#60
by
Space Pete
on 29 Sep, 2009 18:06
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If the ISS Program really wanted to bring Pirs back (something I question the need for), then why not design a trunnion & keel cradle, with an integrated Russian Probe assembly at the rear, that can swivel up to project out of the Payload Bay.
Then, attach a grapple fixture to Pirs somewhere (shouldn't be too hard to do), grapple Pirs with the SSRMS, move it to the cradle, and bring it's drogue down over the protruding probe. Then, latch the probe to the drogue, just like any normal Russian docking, and swivel the probe back down into the Payload Bay, and latch it in place.
One possible issue I see is that the SSRMS might not have the reach to grapple Pirs (it may have when Node 3 is in place).
What does everyone think - is this feasible/viable?
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#61
by
Jim
on 29 Sep, 2009 18:09
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If NASA really wanted to bring Pirs back (something I question the need for), then why not design a trunnion & keel cradle, with an integrated Russian Probe assembly at the rear, that can swivel up to project out of the Payload Bay.
Then, attach a grapple fixture to Pirs somewhere (shouldn't be too hard to do), grapple Pirs with the SSRMS, move it to the cradle, and bring it's drogue down over the protruding probe. Then, latch the probe to the drogue, just like any normal Russian docking, and swivel the probe back down into the Payload Bay, and latch it in place.
One possible issue I see is that the SSRMS might not have the reach to grapple Pirs (it may have when Node 3 is in place).
What does everyone think - is this feasible/viable?
nope. Russian docking system needs a high impulse to engage. Attaching a grapple fixture is not a simple thing.
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#62
by
MBK004
on 29 Sep, 2009 18:11
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One possible issue I see is that the SSRMS might not have the reach to grapple Pirs (it may have when Node 3 is in place).
A PDGF on Zarya would do the trick, I know that there was talk of taking the extra one on P6 and relocating it to Zarya.
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#63
by
Jim
on 29 Sep, 2009 18:12
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2) The analogies were meant to point out things that were non viable thought experiments at one point, and then suddenly became very real problems that needed to be solved.
LM lifeboat was never non viable.
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#64
by
seanpg71
on 29 Sep, 2009 18:15
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2) The analogies were meant to point out things that were non viable thought experiments at one point, and then suddenly became very real problems that needed to be solved.
LM lifeboat was never non viable.
I would argue that returning PIRS was also never non viable. We just don't have a pressing reason to do it at the moment.
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#65
by
Jim
on 29 Sep, 2009 18:16
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2) The analogies were meant to point out things that were non viable thought experiments at one point, and then suddenly became very real problems that needed to be solved.
LM lifeboat was never non viable.
I would argue that returning PIRS was also never non viable. We just don't have a pressing reason to do it at the moment.
There will never be one, hence it is non viable.
There isn't reason to overcome the billion plus dollar cost of a shuttle mission to do it.
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#66
by
Space Pete
on 29 Sep, 2009 18:20
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nope. Russian docking system needs a high impulse to engage.
Maybe the Shuttle could fire it's RCS (although doing so probably wouldn't create much relative velocity while the Shuttle was docked to ISS).
Or else, maybe a new type of latching system for the probe could be developed.
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#67
by
hektor
on 29 Sep, 2009 18:27
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Russian docking system needs a high impulse to engage.
And how is MRM-1 engaged ? what will provide the impulse ?
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#68
by
Danderman
on 29 Sep, 2009 18:34
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If there is a technical reason why Pirs cannot be return in the Shuttle, so be it. But so far, I haven't seen one.
Anything can happen with time and money. There isn't any of that available for PIRS.
The issue is the "dedicated" shuttle flight with a cradle and the associated EVA crew time.
I completely agree that if a dedicated Shuttle flight were required for return of Pirs, based on the assumption that a cradle would take up much or most of the payload bay, then this would be a non-starter.
Could someone explain why the HST cradle, which is very large, also allows many, many tons of other payload to be carried by the Shuttle to 600 km altitude?
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#69
by
Danderman
on 29 Sep, 2009 18:37
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One possible issue I see is that the SSRMS might not have the reach to grapple Pirs (it may have when Node 3 is in place).
What does everyone think - is this feasible/viable?
Bingo, you are the first to address a major issue, how to get Pirs into the Shuttle payload bay. If a PDGF were fitted onto FGB, this would be a difficult, but possible RMS maneuver.
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#70
by
Jim
on 29 Sep, 2009 18:40
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Could someone explain why the HST cradle, which is very large, also allows many, many tons of other payload to be carried by the Shuttle to 600 km altitude?
There isn't an HST cradle. HST has the trunnions and keel on it. When HST was first deployed by the shuttle there was nothing else in the payload bay
What was used for the repair missions was servicing cradle which attached to the aft of HST. It only held HST while on orbit. There other cradles that held the instruments and other hardware. HST could not have returned on a repair mission. A dedicated mission would be required.
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#71
by
Danderman
on 29 Sep, 2009 18:46
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Russian docking system needs a high impulse to engage.
And how is MRM-1 engaged ? what will provide the impulse ?
AFAIK, the ISS RMS would provide the "impulse", but I could be wrong. One option not feasible is to have the RMS provide soft dock, and then to have a Progress or Soyuz dock with MRM-1 to then provide hard dock to ISS.
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#72
by
Danderman
on 29 Sep, 2009 18:48
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Could someone explain why the HST cradle, which is very large, also allows many, many tons of other payload to be carried by the Shuttle to 600 km altitude?
There isn't an HST cradle. HST has the trunnions and keel on it. When HST was first deployed by the shuttle there was nothing else in the payload bay
What was used for the repair missions was servicing cradle which attached to the aft of HST. It only held HST while on orbit. There other cradles that held the instruments and other hardware. HST could not have returned on a repair mission. A dedicated mission would be required.
I was suggesting that the HST "Servicing cradle" was probably larger in volume and mass than any Pirs cradle, yet STS-125 was able to manifest both the HST Servicing Cradle plus many tons of extra equipment.
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#73
by
Danderman
on 29 Sep, 2009 18:49
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One possible issue I see is that the SSRMS might not have the reach to grapple Pirs (it may have when Node 3 is in place).
A PDGF on Zarya would do the trick, I know that there was talk of taking the extra one on P6 and relocating it to Zarya.
My understanding is that placement of this PGDF on FGB is a requirement for the MRM-1 airlock to be transferred to MLM. However, given the slippage of MLM launch, the requirement to move the PGDF from P6 to FGB is not pressing.
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#74
by
Space Pete
on 29 Sep, 2009 18:50
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One possible issue I see is that the SSRMS might not have the reach to grapple Pirs (it may have when Node 3 is in place).
What does everyone think - is this feasible/viable?
Bingo, you are the first to address a major issue, how to get Pirs into the Shuttle payload bay. If a PDGF were fitted onto FGB, this would be a difficult, but possible RMS maneuver.
But, if the SSRMS were based from Zarya, then it probably wouldn't be able to reach the Shuttle's Payload Bay.
So, Pirs would probably have to be handed-off to the SRMS (but then you'd need two FRGF's on Pirs).
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#75
by
Danderman
on 29 Sep, 2009 18:50
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Other than the PLM, there are no other missions with an empty payload bay
Is this actually true? If so, are there missions that will return with a partially empty payload bay?
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#76
by
Danderman
on 29 Sep, 2009 18:52
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And if they launch the PLM as planned on STS-133 even with a shuttle extension MLM will not have been launched get.
I don't understand this assertion. What if the Administration chooses to stretch out the Shuttle program until November 6, 2012? Would the statement above still be true?
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#77
by
Danderman
on 29 Sep, 2009 18:59
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Pirs will be undocked right before MLM is launched, the port will just not be used for a little while.
Note that Pirs can be removed long before MLM is launched; its simply a matter of fitting a hybrid docking adapter on any visiting vehicle programmed to dock with Zvezda nadir. Soyuzes have already docked with space stations using a similar adapter, its just a matter of accepting the additional 100 kg or so mass hit, and in the next few years, we will see Soyuzes and Progresses launched on Soyuz 2, which will provide the additional mass margin.
One concern that would arise from an early departure of Pirs from ISS is the possibility that MLM would have a bad day between its launch and docking with ISS (I do not believe that Pirs would be removed if it appeared that MLM launch was not perceived to be really happening in the relatively near future). In that even, if Pirs were returned to Earth by Shuttle, Pirs itself could serve as the MLM backup, if the MLM were to fail, as a refurbished Pirs could be launched on a Progress bus back to ISS.
Which gives us another rationale for returning Pirs on Shuttle, since the current baseline is to remove and destroy Pirs, and then hope that MLM works, and if not, Zvedza nadir port remains hybrid forever.
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#78
by
Space Pete
on 29 Sep, 2009 19:01
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Other than the PLM, there are no other missions with an empty payload bay
Is this actually true? If not, are there missions that will return with a partially empty payload bay?
I'm under the impression that 129 will land with an emptly PLB, so will 130, 134, 133
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#79
by
Jim
on 29 Sep, 2009 19:02
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Other than the PLM, there are no other missions with an empty payload bay
Is this actually true? If not, are there missions that will return with a partially empty payload bay?
There are no more assembly missions, no more items to be left at the ISS. The "additional" missions will just be resupply, MPLMs and ELC's