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#1160
by
Jorge
on 15 May, 2010 17:13
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I have a question regarding the ET SEP event. As I watched it today during the 132 launch, I was wondering about the forces involved during this key event.
As the orbiter initiates ET SEP, does the tank have a downward force component that naturally pulls it away from the orbiter? In other words, if the orbiter did not perform any RCS firings, what are the tank dynamics at the moment of separation? Would the tank automatically drift downward relative to the orbiter? Or are the orbiter RCS firings required to achieve separation?
Obviously the orbiter is using RCS firings to increase the separation, but are these required (tank will not separate without the RCS firings), or desired (easier to achieve photography)?
Thanks,
David
The RCS firings do help to create safe relative motion. They are required in the RTLS case, because ET SEP occurs at a lower altitude and the combination of propellant slosh and aerodynamic forces can result in recontact.
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#1161
by
Alpha Control
on 15 May, 2010 21:48
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I have a question regarding the ET SEP event. As I watched it today during the 132 launch, I was wondering about the forces involved during this key event.
As the orbiter initiates ET SEP, does the tank have a downward force component that naturally pulls it away from the orbiter? In other words, if the orbiter did not perform any RCS firings, what are the tank dynamics at the moment of separation? Would the tank automatically drift downward relative to the orbiter? Or are the orbiter RCS firings required to achieve separation?
Obviously the orbiter is using RCS firings to increase the separation, but are these required (tank will not separate without the RCS firings), or desired (easier to achieve photography)?
Thanks,
David
The RCS firings do help to create safe relative motion. They are required in the RTLS case, because ET SEP occurs at a lower altitude and the combination of propellant slosh and aerodynamic forces can result in recontact.
Thanks Jorge. I appreciate the info.
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#1162
by
DiggyCoxwell
on 15 May, 2010 21:52
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The Space Shuttle's LOX/LH2 rocket motors, the
LOX/LH2 tank, and the strap-on solids have for decades
inspired engineers to design an unmanned HLV using those components.
i.e., 4 strap-ons + the modified propellant with shuttle rocket motors
fitted to its base capable of lofting more than 200 tons into LEO.
My question is?
Have any bean-counters published an estimate recently of how much it would cost to modify an external shuttle propellant-tank to fit a cluster of shuttle rocket motors at its base; to fit four attachment points instead of two for the SRB's; and to fit a payload carrying platform on top of the propellant tank to lift a 200 ton payload into orbit?
How much would it cost today to do that?
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#1163
by
Jim
on 15 May, 2010 22:02
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Have any bean-counters published an estimate recently of how much it would cost to modify an external shuttle propellant-tank to fit a cluster of shuttle rocket motors at its base; to fit four attachment points instead of two for the SRB's; and to fit a payload carrying platform on top of the propellant tank to lift a 200 ton payload into orbit?
No, because it isn't a viable configuration.
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#1164
by
sdsds
on 16 May, 2010 01:14
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fit four attachment points instead of two for the SRB's;
If we ever see the day when a vehicle is built up in the VAB with two five-segment solids, we're all going to hold our breath as that vehicle is transported out to a pad. Ten segments will be massive!
A vehicle with sixteen segments (four SRBs of four segments each) would not successfully complete the trip.
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#1165
by
wally
on 16 May, 2010 08:01
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In
this picture, the third panel, the one at the right, with the shuttle simulation/visualization, what is the software they use on MCR during shuttle missions? Looks like something available for WindowsXP, is it available for public use?
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#1166
by
Jorge
on 16 May, 2010 12:04
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In this picture, the third panel, the one at the right, with the shuttle simulation/visualization, what is the software they use on MCR during shuttle missions?
Birds Eye View (BEV)
Looks like something available for WindowsXP,
Yes.
is it available for public use?
Not as far as I know.
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#1167
by
kkattula
on 16 May, 2010 12:09
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fit four attachment points instead of two for the SRB's;
If we ever see the day when a vehicle is built up in the VAB with two five-segment solids, we're all going to hold our breath as that vehicle is transported out to a pad. Ten segments will be massive!
A vehicle with sixteen segments (four SRBs of four segments each) would not successfully complete the trip.
i.e. KSC is built on a swamp. The causeway is not engineered to support that mass, it would sink. Unevenly probably, thus tipping over.
NB: Saturn V was moved to the pad unfueled.
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#1168
by
iskyfly
on 16 May, 2010 23:17
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#1169
by
TJL
on 16 May, 2010 23:40
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The woman seen in the STS 132 crew walkout is Janet Kavandi...
DEPUTY DIRECTOR, FLIGHT CREW OPERATIONS, JOHNSON SPACE CENTER.
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#1170
by
GoForTLI
on 16 May, 2010 23:46
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Some questions regarding calls (as it sounds to me) made on the flight loop for the STS-132 ascent;
http://www.space-multimedia.nl.eu.org/index.php?option=com_content&view=article&id=5954
"OMS PDO" or "ON PDO" (8:45)
"trend of minus 6" (9:35)
"fine count" (12:44)
Thanks!
On PDL (the Ponce De Leon Tracking Station). The SRB plumes prevent a good line of sight to MILA for a time during first stage.
I believe the trend of minus 6 is FIDO giving a performance call.
Fine count: Close to MECO, guidance is still computing time left (TGO) and small changes in position error could produce large changes in the thrust turning rate vector, and cause overcontrolling as the closed-loop guidance goes through its NAV cycles (each cycle taking a finite amount of time to compute). Fine count terminates closed-loop guidance (stops trying to go to a target position vs. current position feedback), and the time to go (TGO) is computed solely on VGO (desired velocity change). Guidance is then waiting to see the correct inertial velocity to shut down the SSMEs (taking into account tailoff impulse as the engines shut down). Throttles are going to 67% for fine count.
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#1171
by
Lee Jay
on 16 May, 2010 23:51
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Some questions regarding calls (as it sounds to me) made on the flight loop for the STS-132 ascent;
http://www.space-multimedia.nl.eu.org/index.php?option=com_content&view=article&id=5954
"OMS PDO" or "ON PDO" (8:45)
"trend of minus 6" (9:35)
"fine count" (12:44)
I'm sure someone will correct me if I'm wrong, but I think the trend is the difference between a model and the vehicle performance, the model being used to determine boundaries such as abort this way or abort that way if something were to happen at a particular time. Fine count is, I believe, the mode just before MECO where the system is calculating the precise MECO time including throttle down and tail off thrust to hit the desired point in space and the correct velocity. Don't know what ON PDO means.
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#1172
by
aurora899
on 17 May, 2010 10:23
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The woman seen in the STS 132 crew walkout is Janet Kavandi...
DEPUTY DIRECTOR, FLIGHT CREW OPERATIONS, JOHNSON SPACE CENTER.
Thanks. That would make sense but I must admit that I didn't recognise her. I think she's changed her hair colour!
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#1173
by
iskyfly
on 17 May, 2010 16:01
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Has a GPC ever been outvoted / failed during a mission?
Would that necessitate an immediate return?
Also, what is the story behind the GPC failure during the first Enterprise entry / landing test;
"GPC light." "Big X on computer #2"
?
Thanks!
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#1174
by
Jorge
on 17 May, 2010 16:22
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Has a GPC ever been outvoted / failed during a mission?
Yes, multiple times, but more frequently with the old GPCs than the current ones.
Would that necessitate an immediate return?
No, not for first-fail. Two GPC failures requires a shortened mission.
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#1175
by
Robotbeat
on 17 May, 2010 16:29
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#1176
by
Jorge
on 17 May, 2010 16:39
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#1177
by
iskyfly
on 17 May, 2010 16:51
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Yes, multiple times, but more frequently with the old GPCs than the current ones.
Old GPCs has me curious. I remember reading multiple posts on here about why dont they upgrade the computer hardware on the orbiters since they date back to a 1960/70 design. The response was understandably that the computers have proved themselves, and that to update them would be too costly. So, when were the GPC's replaced, and how are they better?
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#1178
by
Jorge
on 17 May, 2010 18:09
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Yes, multiple times, but more frequently with the old GPCs than the current ones.
Old GPCs has me curious. I remember reading multiple posts on here about why dont they upgrade the computer hardware on the orbiters since they date back to a 1960/70 design. The response was understandably that the computers have proved themselves, and that to update them would be too costly. So, when were the GPC's replaced, and how are they better?
Early 1990s, went from the AP-101B to the AP-101S, binary-compatible with the old GPC, has the I/O Processor (IOP) integrated into the GPC case, twice as much memory (enables the entry software to be stored in an upper-memory archive for quick recall in case of emergency deorbit), solid state memory instead of core.
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#1179
by
mkirk
on 17 May, 2010 22:17
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Has a GPC ever been outvoted / failed during a mission?
Would that necessitate an immediate return?
Also, what is the story behind the GPC failure during the first Enterprise entry / landing test;
"GPC light." "Big X on computer #2"
?
Thanks!
There was a "Fail to sync" of GPC @ on the first free flight of Enterprise, it occured right at separation from the SCA (747).
If you look on this site (NSF) you should be able to find the ALT Program Flight Test results document (I don't know the exact title) and it should go into a lot of detail on what happend. If it is not here you might try the NASA Tech Reports server.
Mark Kirkman