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#900
by
Antares
on 28 Jan, 2010 20:05
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Coooool.
Actually I was talking about the post-MECO cycles. There are 10 cycles in about 3.3 seconds. No wonder Judy Resnik was freaked out on that one abort. And more props for Steve "I thought we'd be a lot higher at MECO" Hawley.
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#901
by
engineerjl
on 04 Feb, 2010 14:26
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I am looking for the subsystem mass properties breakdown for the space shuttle. I formally had a digital copy of an old book that compared the mass of several space craft including the orbiter but cannot remember the name. This would be fine or even better a spreadsheet of the orbiter subsystem mass and cg.
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#902
by
Danderman
on 05 Feb, 2010 00:47
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When the Shuttle docks with ISS, is does any power transfer occur via the APAS docking port? I vaguely recall some limited amount of power, plus data and commands can be sent via the docking system, but I don't know how or if any of this is actually implemented.
If power cannot be transferred from ISS to Shuttle, why not?
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#903
by
Lee Jay
on 05 Feb, 2010 00:50
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#904
by
DaveS
on 05 Feb, 2010 00:52
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When the Shuttle docks with ISS, is does any power transfer occur via the APAS docking port? I vaguely recall some limited amount of power, plus data and commands can be sent via the docking system, but I don't know how or if any of this is actually implemented.
If power cannot be transferred from ISS to Shuttle, why not?
That's the job of the Station to Shuttle Power Transfer System(SSPTS). However, only Discovery and Endeavour is equipped with SSPTS
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#905
by
Danderman
on 05 Feb, 2010 00:53
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#906
by
DaveS
on 05 Feb, 2010 01:11
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#907
by
Danderman
on 05 Feb, 2010 01:20
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Okay, so the 8 Kw passes through the APAS X connector, and then somehow passes via the ODU into the PTU for use by Shuttle, if necessary. Any idea how and where the power gets from APAS into the Shuttle? Does the ODU have some capability of shunting that much power from APAS?
Just curious.
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#908
by
DaveS
on 05 Feb, 2010 01:26
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Okay, so the 8 Kw passes through the APAS X connector, and then somehow passes via the ODU into the PTU for use by Shuttle, if necessary. Any idea how and where the power gets from APAS into the Shuttle? Does the ODU have some capability of shunting that much power from APAS?
Just curious.
That is taken care of by the PTU which is a direct replacement for the earlier APCU which was only capable of transferring power
to the station. The new PTU and it's associated wiring on the orbiter is capable of transfers both to
and from the station, IE it can transfer power both ways.
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#909
by
Danderman
on 05 Feb, 2010 01:27
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That is taken care of by the PTU which is a direct replacement for the earlier APCU which was only capable of transferring power to the station. The new PTU and it's associated wiring on the orbiter is capable of transfers both to and from the station, IE it can transfer power both ways.
I guess I should have asked if the PTU sits in the ODU, or whether there is a honking big extension cord from APAS through the ODU into the nether regions of Shuttle.
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#910
by
Fequalsma
on 05 Feb, 2010 01:30
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Is this the droid you're looking for?
F=ma
I am looking for the subsystem mass properties breakdown for the space shuttle. I formally had a digital copy of an old book that compared the mass of several space craft including the orbiter but cannot remember the name. This would be fine or even better a spreadsheet of the orbiter subsystem mass and cg.
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#911
by
DaveS
on 05 Feb, 2010 01:45
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That is taken care of by the PTU which is a direct replacement for the earlier APCU which was only capable of transferring power to the station. The new PTU and it's associated wiring on the orbiter is capable of transfers both to and from the station, IE it can transfer power both ways.
I guess I should have asked if the PTU sits in the ODU, or whether there is a honking big extension cord from APAS through the ODU into the nether regions of Shuttle.
No cable. The PTU is all integrated with the ODS and the orbiter EPS.
This is from the SCOM
OV-103 and OV-105 previously carried the
standalone version of the APCU described above, but
have been upgraded to the newer Station/Shuttle
Power Transfer System (SSPTS). Operated via
switches on panel A15 that were formerly used by the
EDO Cryo Pallet System (which is no longer used),
SSPTS consists of two power transfer units (PTUs),
each of which has a single APCU voltage step-up
converter similar to the ones discussed above, and two
voltage step-down orbiter power converter unit
(OPCU) converters. The OPCU allows 120 volt DC
power from the ISS solar arrays to be transferred to
the shuttle’s main buses A and B at 28 volts. The
OPCU portion of SSPTS offloads some electrical load
from the orbiter’s FCs onto the ISS solar arrays; the
reduction in load on the FCs reduces the cryo usage,
which is then used for mission extension days. The
APCU portion of SSPTS is usable at any point in the
mission, while the OPCU portion is only usable after
docking to the ISS. Data is visible to the crew on SM
SPEC 179 POWER TRANSFER.
Before any power can be converted either by an APCU
or OPCU, the PTUs must be connected to the
shuttle’s main buses. PTU 1 is associated with main
A, and PTU 2 is associated with main B. To connect
the PTU to the main bus, the CNTL PWR circuit
breakers on A15 row B must be pushed in first. These
breakers power the PTU/MAIN BUS switches and
talkbacks. Upon successful connection between a PTU
and main bus, the associated talkback will turn from
OFF to ON. At this point, an APCU may be
activated to convert orbiter DC power for payload
requirements, and, after docking, the OPCU can be
activated to convert ISS DC power for shuttle main
bus requirements.
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#912
by
Zpoxy
on 06 Feb, 2010 23:30
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No cable. The PTU is all integrated with the ODS and the orbiter EPS.
Sorry DaveS, that's not quite right. This is from memory, I don't have any schematics here. Power comes down from the X connector through two 8 gage cables routed externally along the ODS truss and support beams mounted on the payload bay side wall. They make their way to the PTUs which are located in the left side of bay 5.
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#913
by
AnalogMan
on 07 Feb, 2010 00:20
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This diagram does not resolve the issue of how the connection between the APAS X-connectors and the orbiter PTUs is physically implemented (I don't know myself), but might help others visualise how the rest of the various sub-systems are connected.
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#914
by
mjp25
on 08 Feb, 2010 13:47
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After MECO and ET jettison, I breathe a little easier. I know, nothing for sure until wheels stop, but you see where I'm headed. But, as I was turning off my television at 4:24am this morning, the following question came to mind. What if there is an OMS failure when the OMS 2 burn is supposed to occur? I understand this is probably very unlikely. My guesses are the following, but obviously I'm posting here because I don't know.
If it is a single OMS engine failure, use the good one, get in a cirular orbit and work it out from there. Is the rendevous off if the second OMS engine can not be recovered?
If both engines fail (I know, REALLY unlikely) but the RCS is still functioning, can it be used to circularze the orbit? My guess is yes, but now you would need it to deorbit too. So would they get stable and work the problem, or just reenter and treat it as and AOA? My thought is that a stable orbit is the safest place to be even if that means you're on a back up system to deorbit.
Ok, so a lot of questions and I'm probably missing something, but I would be interested if anyone knows the procedures for such an event. Thanks.
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#915
by
MikeMi.
on 08 Feb, 2010 22:25
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If both engines fail (I know, REALLY unlikely) but the RCS is still functioning, can it be used to circularze the orbit?
I think it is impossible to make such manouvers with RCS. OMS are required to change parameters of the shuttle orbit. Fail of two OMS engines would mean a LOM probably but im not sure (better wait for someone with good knowledge
and in this situation it would end with re-enter and land in KSC. Dunno if it is possible but I remember tha I read here some post about such a operation with using only RCS to back from LEO.
And wanna ask about some shuttle first minutes of flight. Look at this graphic, it has a polish words but take a look on shape of this trajectory in function of time.
This graph is based on some today seen on Fox News graphic which showed similiar graph (on line Y there was altitude in km, on X line time of flight). So time for question - there is a conclusion in my mind after looking at this graph that shuttle is climbing to initial orbit to fifth minute, after that she doesn't get much km of altitude more. What's most interesting it seems to loose some altitude after fifth minute of flight (and before meco) - can You explain my why that happen? What is energetic sense of loosing this few kms on da begining?
Thanks for answers,
greetz,
Mike
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#916
by
Jorge
on 08 Feb, 2010 22:40
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After MECO and ET jettison, I breathe a little easier. I know, nothing for sure until wheels stop, but you see where I'm headed. But, as I was turning off my television at 4:24am this morning, the following question came to mind. What if there is an OMS failure when the OMS 2 burn is supposed to occur? I understand this is probably very unlikely. My guesses are the following, but obviously I'm posting here because I don't know.
If it is a single OMS engine failure, use the good one, get in a cirular orbit and work it out from there. Is the rendevous off if the second OMS engine can not be recovered?
If both engines fail (I know, REALLY unlikely) but the RCS is still functioning, can it be used to circularze the orbit? My guess is yes, but now you would need it to deorbit too. So would they get stable and work the problem, or just reenter and treat it as and AOA? My thought is that a stable orbit is the safest place to be even if that means you're on a back up system to deorbit.
Ok, so a lot of questions and I'm probably missing something, but I would be interested if anyone knows the procedures for such an event. Thanks.
RCS is considered a deorbit method. Although it could also be used for circularization, flight rules forbid it for this case. Loss of two deorbit methods (e.g. both OMS engines) means coming home immediately.
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#917
by
Jorge
on 08 Feb, 2010 22:41
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If both engines fail (I know, REALLY unlikely) but the RCS is still functioning, can it be used to circularze the orbit?
I think it is impossible to make such manouvers with RCS. OMS are required to change parameters of the shuttle orbit. Fail of two OMS engines would mean a LOM probably but im not sure (better wait for someone with good knowledge and in this situation it would end with re-enter and land in KSC. Dunno if it is possible but I remember tha I read here some post about such a operation with using only RCS to back from LEO.
And wanna ask about some shuttle first minutes of flight. Look at this graphic, it has a polish words but take a look on shape of this trajectory in function of time.
This graph is based on some today seen on Fox News graphic which showed similiar graph (on line Y there was altitude in km, on X line time of flight). So time for question - there is a conclusion in my mind after looking at this graph that shuttle is climbing to initial orbit to fifth minute, after that she doesn't get much km of altitude more. What's most interesting it seems to loose some altitude after fifth minute of flight (and before meco) - can You explain my why that happen? What is energetic sense of loosing this few kms on da begining?
Thanks for answers,
greetz,
Mike
It's trading some potential energy (altitude) for kinetic energy (speed). The idea is to get above the atmosphere as quickly as possible without overstressing the structure, then performing a long shallow dive to get more speed.
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#918
by
MikeMi.
on 09 Feb, 2010 00:19
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It's trading some potential energy (altitude) for kinetic energy (speed). The idea is to get above the atmosphere as quickly as possible without overstressing the structure, then performing a long shallow dive to get more speed.
It seems logical. In this long shallow dive we get so much speed? How its possible if it is only few km of altitude?
What do u mean with 'overstressing the structure' - pressure which came from changing of acceleration? (Cause there are no aerodynamic stressing above - lets say 80 km of altitude).
edit: Second question - theoritically could the shuttle climb higher without going to this shallow dive? I mean climb further to point where she would get a required speed. I can imagine that it would cost a lot of fuel but wanna just ensure myself..
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#919
by
engineerjl
on 09 Feb, 2010 06:13
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what is the OMS propellent budget?
assent, circulation, orbit, deorbit, reserve, residual...
and in this situation it would end with re-enter and land in KSC. Dunno if it is possible but I remember tha I read here some post about such a operation with using only RCS to back from LEO.