-
#2560
by
alk3997
on 17 Mar, 2012 12:54
-
Hi all.
Another question for the rendezvous expert guys.
After Ti burn, how were the MCs burns computed? If I’ve understood well the MCs burns were targeted by the crew since they had more accurate data available during the last part of the approach.
What I’d like to understand is how each MC burn was computed. Because using Lambert to compute the burn, they had to feed the computers with data regarding the point of arrival, along the trajectory. So, for example, which kind of data they provided for executing MC-1 burn to get to the point for MC-2?
Were always all MCs burns done or sometimes they could skip some burn?
Thanks very much
Davide
Davide, after the TI burn and the first MC (MC4), the crew would be in "manual" mode. For the manual part of the burns, the computations were performed on the ground and onboard in RPOP on the ThinkPads (for the later half of the Shuttle flights). RPOP used rendezvous radar, handheld lidar and the TCS payload bay laser as inputs. The rendezvous radar was of limited use as the target got bigger, which is why it could be transitioned back to TV/data mode during later prox ops.
Onboard, I believe a COAS fix on the target was also used to manually compute a solution - particularly in the "old days" (before RPOP).
-
#2561
by
Jorge
on 17 Mar, 2012 22:10
-
After Ti burn, how were the MCs burns computed? If I’ve understood well the MCs burns were targeted by the crew since they had more accurate data available during the last part of the approach.
Correct.
What I’d like to understand is how each MC burn was computed. Because using Lambert to compute the burn, they had to feed the computers with data regarding the point of arrival, along the trajectory. So, for example, which kind of data they provided for executing MC-1 burn to get to the point for MC-2?
Refer to the STS-135 rendezvous procedures on the NASA public site:
http://www.nasa.gov/centers/johnson/pdf/567076main_RNDZ_135_F.pdfThe MC targeting procedures are in blocks 17A, 17B, 18A, 18B, 19B, and 20A (pages 67-70 of the PDF). I've attached the MC1 targeting block (17A) as an example. The procedures were basically the same as for the previous onboard targeted burns (NCC and Ti). Navigation state vectors went to the targeting software automatically, so the crew only had to check that the correct orbiter state vector was selected prior to targeting. The crew performed one keyboard entry to recall the targeting data for the desired burn, checked the targeting data, performed another keyboard entry to compute the solution, then recorded the solution in the PAD in the book. MC1, 2, and 3 targeted the MC4 point. MC4 targeted the Rbar.
Were always all MCs burns done or sometimes they could skip some burn?
The RCS burn cue card (page 209 of the PDF) directed the crew to trim the VGOs to less than 0.2 fps. So if the final solution was less than 0.2, the crew would skip the burn unless MCC directed otherwise.
-
#2562
by
sivodave
on 20 Mar, 2012 21:51
-
Guys, thanks very much for your answers, they are really helpful. I’ve started to give a better look to the Rendezvous Flight Data File for STS-135 (just as an example since Jorge used the same).
Taking for example page 67, I see that at the beginning of the timeline, the crew has to target the burn for MC-1 (preliminary) then MC-1 (intermediate) and finally MC-1 (final). What do they mean? Why are the three different MC-1 burn targets? I also see that in the document there is the target condition for only one MC-1 and not for MC-1 preliminary, or intermediate or final.
Reasoning about it, my guess is that the solution for a given MC was computed three times so to refine it up to when the burn had to be executed. Probably because from when the MC burn preliminary was computed up to when the MC burn final was executed the trajectory could be somehow perturbed. Is my guess correct?
Always at the same page, at minute PET 00:17 is written to perform TARGET MC-1 (final) and then to perform RCS BURN (cue card). I don’t understand if this RCS burn had to be carried out by the crew (PLT is shown in the timeline) or if it was automatic. Or, based on what Jorge has written, the RCS burn had to perform only if the solution computed for the given MC had a Delta-V more than 0.2 ft/s?
Also I see from the same page that for computing the burn solution ORBIT TGT was used. Why was used this display and not MNVR display?
Also I don’t understand if the RPOP was used before MC-4 or after? If I am right RPOP did not communicate with GNC so my guess is that RPOP was used only after MC-4 or to better say for departure from the +R Bar for the final approach. Could you please confirm this?
Thanks very much for your help
Davide
-
#2563
by
Jorge
on 21 Mar, 2012 02:53
-
Taking for example page 67, I see that at the beginning of the timeline, the crew has to target the burn for MC-1 (preliminary) then MC-1 (intermediate) and finally MC-1 (final). What do they mean? Why are the three different MC-1 burn targets? I also see that in the document there is the target condition for only one MC-1 and not for MC-1 preliminary, or intermediate or final.
Reasoning about it, my guess is that the solution for a given MC was computed three times so to refine it up to when the burn had to be executed. Probably because from when the MC burn preliminary was computed up to when the MC burn final was executed the trajectory could be somehow perturbed. Is my guess correct?
Yes. The software only kept the most recent solution so only the final solution mattered when it came to actually performing the burn. The other two solutions were computed for trend monitoring.
Always at the same page, at minute PET 00:17 is written to perform TARGET MC-1 (final) and then to perform RCS BURN (cue card). I don’t understand if this RCS burn had to be carried out by the crew (PLT is shown in the timeline) or if it was automatic. Or, based on what Jorge has written, the RCS burn had to perform only if the solution computed for the given MC had a Delta-V more than 0.2 ft/s?
It had to be performed by the crew.
Also I see from the same page that for computing the burn solution ORBIT TGT was used. Why was used this display and not MNVR display?
The crew keyboard entries for performing various actions were tied to the items on the displays. ORBIT TGT contained the display items for recalling the targeting data and computing the solution. ORBIT MNVR EXEC contained the display items for loading and executing the burn after the solution was computed.
Also I don’t understand if the RPOP was used before MC-4 or after? If I am right RPOP did not communicate with GNC so my guess is that RPOP was used only after MC-4 or to better say for departure from the +R Bar for the final approach. Could you please confirm this?
RPOP received data from GNC but could not talk to it. It was used purely for situational awareness by the crew. The procedures called for the crew to run RPOP on p. 57 of the PDF. So the RPOP display was available well before MC4 but the crews typically did not use it for much until after MC4.
-
#2564
by
JayP
on 21 Mar, 2012 14:53
-
Does anyone know if there is a technical reason why the LO2 connections are on the starboard side and the LH2 connections are on the port? I’m talking about the ET feed lines, umbilical wells and T-0 panels.
I can’t find a reason why they would be that way, but I can find a reason why they shouldn’t. The LH2 and LO2 dewars at the pads are in the north east and north west corners of the pad respectively and they were there long before the shuttle was designed. That means that the LH2 lines run down side 4 of the MLP which is the starboard side of the shuttle and the LO2 lines run down side 2 which is to port. That in turn means that the lines have to cross over each other on side 1 to get to their respective TSMs. The LH2 lines go up and run under the blast shield and then turn into the tunnel while the LO2 lines run along the face of the MLP before turning up to enter their tunnel. If the connections on the shuttle were reversed the lines could be kept separate and provided with physical barriers to limit gas mixing if there were leaks.
If there isn’t a specific reason for this, is it possible that Marshall just missed it back in the early 70’s? That sound impossible to me, but you never know.
-
#2565
by
wolfpack
on 21 Mar, 2012 15:37
-
Does anyone know if there is a technical reason why the LO2 connections are on the starboard side and the LH2 connections are on the port? I’m talking about the ET feed lines, umbilical wells and T-0 panels.
I can’t find a reason why they would be that way, but I can find a reason why they shouldn’t. The LH2 and LO2 dewars at the pads are in the north east and north west corners of the pad respectively and they were there long before the shuttle was designed. That means that the LH2 lines run down side 4 of the MLP which is the starboard side of the shuttle and the LO2 lines run down side 2 which is to port. That in turn means that the lines have to cross over each other on side 1 to get to their respective TSMs. The LH2 lines go up and run under the blast shield and then turn into the tunnel while the LO2 lines run along the face of the MLP before turning up to enter their tunnel. If the connections on the shuttle were reversed the lines could be kept separate and provided with physical barriers to limit gas mixing if there were leaks.
If there isn’t a specific reason for this, is it possible that Marshall just missed it back in the early 70’s? That sound impossible to me, but you never know.
I'll SWAG it...
The need for GH2 venting and the fact that the umbilical for that has to be on the FSS, which is to port?
I doubt they "forgot" about the locations of the LC-39 tanks. LC-39 was not necessarily going to be the STS launch site early on.
-
#2566
by
JayP
on 21 Mar, 2012 16:16
-
I'll SWAG it...
The need for GH2 venting and the fact that the umbilical for that has to be on the FSS, which is to port?
Possible, but I kind of doubt it. The LH2 vent line in the interstage is "behind" the SRB beam while the LO2 J-leg is in front of it. Moving the J-leg to the port side shouldn't have affected the LH2 vent any.
I doubt they "forgot" about the locations of the LC-39 tanks. LC-39 was not necessarily going to be the STS launch site early on.
I thought of that, but no. By the time they reached the phase B studies in the 1970 time frame (which is when the ET concept firmed up) they were already commited to LC-39 (based on cost, if nothing else). The decision of what side to run the line on probably didn't get made until the phase C/D work in 71 or 72 if not later.
I'm not suggesting that they just "forgot" where the tanks were. Originaly, activities at the cape fell under Marshall's "Launch Opperations Directorate". That included design of the launch pads and equipment. There were some notorious problems with the project management of the swing arms for the SaturnV LUT. Whether or not that had anything to do with what happened subsequently is open to debate, but the fact is that KSC was formed as it's own center and assumed the responsability for launch equipment design and fabrication. By the time the Shuttle came along, the launch pad wasn't really Marshall's problem anymore and so this issue might not have come up on their radar.
-
#2567
by
wolfpack
on 21 Mar, 2012 17:58
-
I'll SWAG it...
The need for GH2 venting and the fact that the umbilical for that has to be on the FSS, which is to port?
Possible, but I kind of doubt it. The LH2 vent line in the interstage is "behind" the SRB beam while the LO2 J-leg is in front of it. Moving the J-leg to the port side shouldn't have affected the LH2 vent any.
I doubt they "forgot" about the locations of the LC-39 tanks. LC-39 was not necessarily going to be the STS launch site early on.
I thought of that, but no. By the time they reached the phase B studies in the 1970 time frame (which is when the ET concept firmed up) they were already commited to LC-39 (based on cost, if nothing else). The decision of what side to run the line on probably didn't get made until the phase C/D work in 71 or 72 if not later.
I'm not suggesting that they just "forgot" where the tanks were. Originaly, activities at the cape fell under Marshall's "Launch Opperations Directorate". That included design of the launch pads and equipment. There were some notorious problems with the project management of the swing arms for the SaturnV LUT. Whether or not that had anything to do with what happened subsequently is open to debate, but the fact is that KSC was formed as it's own center and assumed the responsability for launch equipment design and fabrication. By the time the Shuttle came along, the launch pad wasn't really Marshall's problem anymore and so this issue might not have come up on their radar.
Maybe fire suppression, then? That's on the FSS, and it would be harder to extinguish an H2 fire on the starboard side of the stack.
-
#2568
by
JayP
on 21 Mar, 2012 19:10
-
Maybe fire suppression, then? That's on the FSS, and it would be harder to extinguish an H2 fire on the starboard side of the stack.
Actually, the fire suppresion of a fire involving the vehicle is done by nozzles on the deck of the MLP and on top of the TSMs and is pretty symetrical. The FireX system on the FSS is mostly to cool and protect the FSS itself.
I'm not trying to shoot down every idea you have. Keep em comming and we may find the answer.
-
#2569
by
wolfpack
on 22 Mar, 2012 11:42
-
Maybe fire suppression, then? That's on the FSS, and it would be harder to extinguish an H2 fire on the starboard side of the stack.
Actually, the fire suppresion of a fire involving the vehicle is done by nozzles on the deck of the MLP and on top of the TSMs and is pretty symetrical. The FireX system on the FSS is mostly to cool and protect the FSS itself.
I'm not trying to shoot down every idea you have. Keep em comming and we may find the answer.
Probably has to with how they decided to plumb the MPS in the boattail, then. Unless some of the NASA folks here know, you're going to have to dig through some archives at MSFC and JSC. I'll bet those decisions date back to 1974 or '75.
-
#2570
by
Jim
on 22 Mar, 2012 11:56
-
I'll SWAG it...
The need for GH2 venting and the fact that the umbilical for that has to be on the FSS, which is to port?
Possible, but I kind of doubt it. The LH2 vent line in the interstage is "behind" the SRB beam while the LO2 J-leg is in front of it. Moving the J-leg to the port side shouldn't have affected the LH2 vent any.
I would say that is the best answer. That means that all H2 lines are on the west side of the flame trench
-
#2571
by
JayP
on 22 Mar, 2012 13:14
-
I'll SWAG it...
The need for GH2 venting and the fact that the umbilical for that has to be on the FSS, which is to port?
Possible, but I kind of doubt it. The LH2 vent line in the interstage is "behind" the SRB beam while the LO2 J-leg is in front of it. Moving the J-leg to the port side shouldn't have affected the LH2 vent any.
I would say that is the best answer. That means that all H2 lines are on the west side of the flame trench
Actually, the LH2 lines are mostly on the east side. The lines run from the storage dewar and flare off stack to the tower on the north east corner of the MLP. From there, the fill and drain line and the TSM vent line run down the east and south sides of the MLP itself to the valve skid on AP-3. The vent line from the GUP on the ET interstage runs thru the t-0 umbilicle to the FSS and then down to about 35 ft above the hard stand. It then runs to the north and then along the bridge across the north end of the flame trench to the tower at the north east corner of the MLP were it joins the other lines.
From the point of view of the launch pad and facilities, it wouuld make sense to have all the LH2 stuf to the east and LO2 to the west. That is why I'm assumming there is some driving reason on the vehicle itself why the ET and MPS lines are where they are.
-
#2572
by
sivodave
on 23 Mar, 2012 09:23
-
Hi Jorge.
Thanks for you answers…they are very clear and I’m seeing the light now!
Just two last things regarding this subject:
Always at the same page, at minute PET 00:17 is written to perform TARGET MC-1 (final) and then to perform RCS BURN (cue card). I don’t understand if this RCS burn had to be carried out by the crew (PLT is shown in the timeline) or if it was automatic. Or, based on what Jorge has written, the RCS burn had to perform only if the solution computed for the given MC had a Delta-V more than 0.2 ft/s?
It had to be performed by the crew.
When you say that the burn had to be performed by the crew, does this mean that the pilot (or CDR) had to impart commands on the THC for performing the burn, stopping to provide input when the computed Delta-Vs were reached?
Also I see from the same page that for computing the burn solution ORBIT TGT was used. Why was used this display and not MNVR display?
The crew keyboard entries for performing various actions were tied to the items on the displays. ORBIT TGT contained the display items for recalling the targeting data and computing the solution. ORBIT MNVR EXEC contained the display items for loading and executing the burn after the solution was computed.
Again just a clarification. Did ORBIT TGT communicate the burn solution to ORBIT MNVR EXEC? Thinking about how the single displays worked and to the fact that there was a PAD for each burn, my guess is that the two displays did not communicate with each other, but that the astronauts had to write the burn solution into the PAD so to know what to insert into the MNVR EXEC display.
One last question. In [link=http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110023479_2011024697.pdf] this [/link] document, at page 81 at the bottom of left column, is written the +R approaches became viable with the addition of proximity operations sensors and for this reason STS-66 was the first mission flying this approach. However STS-32 for retrieving LDEF flew a –R approach. So what was the problem in doing a +R bar approach? –R Bar and +R bar are no practically each other’s mirror copy?
Thanks very much
Davide
-
#2573
by
NavySpaceFan
on 29 Mar, 2012 15:05
-
Question re: STS-88. According to the post-mission report, Endeavour conducted a Dual Engine OMS Assist maneuver (102 seconds in duration) at 00:02:14 MET, just after SRB speration. Why was that maneuver performed? Unity's mass? Rendezvous considerations? Something else? Thanks!
-
#2574
by
Jorge
on 29 Mar, 2012 15:21
-
Question re: STS-88. According to the post-mission report, Endeavour conducted a Dual Engine OMS Assist maneuver (102 seconds in duration) at 00:02:14 MET, just after SRB speration. Why was that maneuver performed? Unity's mass? Rendezvous considerations? Something else? Thanks!
Performance enhancement. Wasn't just STS-88. Almost all shuttle missions to ISS performed OMS Assist.
-
#2575
by
Jorge
on 29 Mar, 2012 15:26
-
Hi Jorge.
Thanks for you answers…they are very clear and I’m seeing the light now!
Just two last things regarding this subject:
Always at the same page, at minute PET 00:17 is written to perform TARGET MC-1 (final) and then to perform RCS BURN (cue card). I don’t understand if this RCS burn had to be carried out by the crew (PLT is shown in the timeline) or if it was automatic. Or, based on what Jorge has written, the RCS burn had to perform only if the solution computed for the given MC had a Delta-V more than 0.2 ft/s?
It had to be performed by the crew.
When you say that the burn had to be performed by the crew, does this mean that the pilot (or CDR) had to impart commands on the THC for performing the burn, stopping to provide input when the computed Delta-Vs were reached?
Yes.
Also I see from the same page that for computing the burn solution ORBIT TGT was used. Why was used this display and not MNVR display?
The crew keyboard entries for performing various actions were tied to the items on the displays. ORBIT TGT contained the display items for recalling the targeting data and computing the solution. ORBIT MNVR EXEC contained the display items for loading and executing the burn after the solution was computed.
Again just a clarification. Did ORBIT TGT communicate the burn solution to ORBIT MNVR EXEC?
Yes.
One last question. In [link=http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110023479_2011024697.pdf] this [/link] document, at page 81 at the bottom of left column, is written the +R approaches became viable with the addition of proximity operations sensors and for this reason STS-66 was the first mission flying this approach. However STS-32 for retrieving LDEF flew a –R approach. So what was the problem in doing a +R bar approach? –R Bar and +R bar are no practically each other’s mirror copy?
The +Rbar approach involved performing a retrograde burn at the initial +Rbar crossing in order to stay on the +Rbar and not continue to the +Vbar. This reduced orbital energy. Without accurate sensors the approach rate could not be maintained due to lack of energy.
The STS-32 LDEF -Rbar approach involved continuing to fly up to the +Vbar and around to the -Rbar so sufficient energy to reach the -Rbar was assured. The Rbar approach was only for the last 250 ft or so, so the crew could confirm and maintain approach rate visually if no sensors were available.
-
#2576
by
NavySpaceFan
on 29 Mar, 2012 15:49
-
Question re: STS-88. According to the post-mission report, Endeavour conducted a Dual Engine OMS Assist maneuver (102 seconds in duration) at 00:02:14 MET, just after SRB speration. Why was that maneuver performed? Unity's mass? Rendezvous considerations? Something else? Thanks!
Performance enhancement. Wasn't just STS-88. Almost all shuttle missions to ISS performed OMS Assist.
Thanks Jorge!
-
#2577
by
DaveS
on 31 Mar, 2012 13:27
-
Just checking so I have gotten it right: The KU ANTENNA DIRECT STOW switch on R13L, it rotates the DA to the stowed position regardless of the gimbal positions?
If the DIRECT STOW has to be used and the normal way of moving the gimbals to the stowed positions have failed, a EVA is required to manually position the gimbals before a DIRECT STOW is attempted?
-
#2578
by
alk3997
on 31 Mar, 2012 16:01
-
Question re: STS-88. According to the post-mission report, Endeavour conducted a Dual Engine OMS Assist maneuver (102 seconds in duration) at 00:02:14 MET, just after SRB speration. Why was that maneuver performed? Unity's mass? Rendezvous considerations? Something else? Thanks!
As Jorge said, added as part of performance enhancements and included as part of OI-26 FSW. Very similar to what we would have done to dump OMS prop in the event of a single-engine-out abort. Since the OMS were hypergolic, the difference between a dump and a burn is symantics.
In my simple way of looking at it, the OMS assist burn was closer to perigee (on the ground) and so was more efficient than an OMS-1 burn. Also you didn't want to carry the prop weight any further than you needed to. The other constraint is that the OMS could not be burned below a certain altitude.
I believe we always left the burn enabled, but if we didn't want it, the uplinked time could be set to 0. The OMS assist burn time would be adjusted on launch day.
-
#2579
by
e of pi
on 02 Apr, 2012 01:20
-
What was the official name for the suit worn by Shuttle crews between the phaseout of the ejection suit after STS-4 and the introduction of the LES for STS-26? I'm trying to find out about its capabilities and reasons it was used, but a quick search isn't bringing up much about it.