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#180
by
yg1968
on 24 May, 2022 00:17
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How is this going to affect the Starliner test program? I was hoping for better performance was the Starliner.
I imagine not a lot and that they will still move forward to the crewed test. While 2 thruster failures is not exactly a great look for Boeing, ultimately there is a lot of redundancy here for a reason, NASA just needs to needs to stay on Boeing's butt and insure these issues are being worked on. Of course, this assumes the rest of the flight goes well.
There is also the coolant issue that Steve Stich mentioned in the press conference. Stich said that they fixed that issue by bypassing the radiator for docking. I would imagine that that is another problem to look at after the mission.
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#181
by
Vettedrmr
on 24 May, 2022 00:22
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Two thrusters firing for 62 seconds is the same as three firing for 41sec and 4 thrusters firing for 31 sec.
It is more than triple redundancy (3 thrusters in each doghouse.)
Question: if a thruster fails during the de-orbit burn that requires the burn duration to be extended, the total delta-v is the same. BUT, because the burn start was calculated with a nominal acceleration, does the reduced acceleration change the touchdown point?
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#182
by
baldusi
on 24 May, 2022 01:03
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Two thrusters firing for 62 seconds is the same as three firing for 41sec and 4 thrusters firing for 31 sec.
It is more than triple redundancy (3 thrusters in each doghouse.)
Question: if a thruster fails during the de-orbit burn that requires the burn duration to be extended, the total delta-v is the same. BUT, because the burn start was calculated with a nominal acceleration, does the reduced acceleration change the touchdown point?
If you have propellant margin, you can apply more propulsion to lower the orbital velocity to compensate. It would also reduce the stress on the heat shield.
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#183
by
AstroWare
on 24 May, 2022 01:22
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So how much redundancy is built into Starliner with these thrusters.
So they have 4 groups of 3 thrusters on the top, bottom, let and right. If the third thruster had failed could Starliner have shut off the thrusters on the opposite side and still continued the mission. Basically if the thrusters on the left and right were not in use would the thrusters on the top and bottom be enough to do the job?
Two thrusters firing for 62 seconds is the same as three firing for 41sec and 4 thrusters firing for 31 sec.
It is more than triple redundancy (3 thrusters in each doghouse.)
Burning fewer thrusters longer is of course an option but the software was obviously written to FIRST try and use alternate thrusters.
Agree with the greater than 3 redundancy - iin fact t's even greater than triple redundant BEFORE having to resort to a reduced engine quantity burn.
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#184
by
arachnitect
on 24 May, 2022 01:29
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Two thrusters firing for 62 seconds is the same as three firing for 41sec and 4 thrusters firing for 31 sec.
It is more than triple redundancy (3 thrusters in each doghouse.)
Question: if a thruster fails during the de-orbit burn that requires the burn duration to be extended, the total delta-v is the same. BUT, because the burn start was calculated with a nominal acceleration, does the reduced acceleration change the touchdown point?
If you have propellant margin, you can apply more propulsion to lower the orbital velocity to compensate. It would also reduce the stress on the heat shield.
Capsule can also change its trajectory to a certain extent in the atmosphere using lift vector
I assume a nominal deorbit burn wouldn't call for max available thrust, so impact of switching thrusters would be limited?
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#185
by
omelet1978
on 24 May, 2022 03:48
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So any word on how the leadership at NASA and Boeing are viewing this test so far?
I ask that with the caveat that it was a while after Starliner’s last test flight that NASA identified around 80 points of concern about the spacecraft, so let’s just hope that those issues were fixed this time around. From what i can see so far there has been the thruster issue, the environmental issue, and then some sort of issue that caused a delay in docking with the ISS. Assuming Starliner avoids almost hitting it’s service module again and lands safely it does appear to be a step in the right direction.
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#186
by
Vahe231991
on 24 May, 2022 15:58
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So any word on how the leadership at NASA and Boeing are viewing this test so far?
I ask that with the caveat that it was a while after Starliner’s last test flight that NASA identified around 80 points of concern about the spacecraft, so let’s just hope that those issues were fixed this time around. From what i can see so far there has been the thruster issue, the environmental issue, and then some sort of issue that caused a delay in docking with the ISS. Assuming Starliner avoids almost hitting it’s service module again and lands safely it does appear to be a step in the right direction.
It remains to be seen if Boeing is in the process of incorporating redesigned valves for the Starliner into the Starliner capsule earmarked for the CFT mission due to launch in the second half of this year.
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#187
by
butters
on 24 May, 2022 16:23
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How is this going to affect the Starliner test program? I was hoping for better performance was the Starliner.
I imagine not a lot and that they will still move forward to the crewed test. While 2 thruster failures is not exactly a great look for Boeing, ultimately there is a lot of redundancy here for a reason, NASA just needs to needs to stay on Boeing's butt and insure these issues are being worked on. Of course, this assumes the rest of the flight goes well.
There is also the coolant issue that Steve Stich mentioned in the press conference. Stich said that they fixed that issue by bypassing the radiator for docking. I would imagine that that is another problem to look at after the mission.
The thing that's odd about Boeing/NASA pointing to the lack of metabolic heat from a human crew as a contributing factor for the coolant loop issue is that this wasn't raised as an issue on OFT-1, which also lacked a crew. I think we can prune the "Jebediah Kerman has negative metabolic rate" theory from the fault tree. So the difference would seem to be that OFT-2 had some water in the coolant loop for some reason, and OFT-1 didn't. Another "water intrusion into places where it shouldn't be" kind of issue for Boeing to investigate.
Clearly, a cooling system that fails when the heat load is reduced a couple hundred watts below nominal is unacceptable. For example, spacecraft have plenty of systems redundancy for good reason, and it's essential that multiple inoperative systems that are powered down and no longer emitting heat doesn't have the knock-on effect of causing the cooling system to fail.
Maybe the water in the coolant wouldn't have frozen if there were exothermic meatbags onboard, but that's beside the point and doesn't necessarily speak to the safety of having crew onboard. Calling out the lack of crew as a reasonable-sounding excuse is preying on the relative ignorance of the mass media audience who won't ask "but what about OFT-1?" or whether a cooling system so sensitive to heat load is suitable for a human-rated spacecraft.
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#188
by
edzieba
on 24 May, 2022 16:46
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There's also the different flight profile of OFT-1. First the overexited thruster dance (to the extent of triggering thermal alarms for the thrusters) and unintentional angles-and-dangles may have both resulted in a higher thermal load on the capsule environment, from both contact heating (hot thrusters), radiant heating (capsule windows pointed at sun for more time), and lack of cooling (radiators not pointed at optimal orientation for heatsinking). Second, after initial recover OFT-1 flew at a lower altitude to OFT-2 so may have received slightly more heating from the Earth. Finally, the cargo loading is different, which affects both them thermal mass to be heated/cooled inside the capsule, and some items may make a direct contribution to heating (e.g. passively insulated refrigerated items will be sinking heat, whereas actively cooled refrigerated items will be producing heat).
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#189
by
arachnitect
on 24 May, 2022 17:01
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How is this going to affect the Starliner test program? I was hoping for better performance was the Starliner.
I imagine not a lot and that they will still move forward to the crewed test. While 2 thruster failures is not exactly a great look for Boeing, ultimately there is a lot of redundancy here for a reason, NASA just needs to needs to stay on Boeing's butt and insure these issues are being worked on. Of course, this assumes the rest of the flight goes well.
There is also the coolant issue that Steve Stich mentioned in the press conference. Stich said that they fixed that issue by bypassing the radiator for docking. I would imagine that that is another problem to look at after the mission.
The thing that's odd about Boeing/NASA pointing to the lack of metabolic heat from a human crew as a contributing factor for the coolant loop issue is that this wasn't raised as an issue on OFT-1, which also lacked a crew. I think we can prune the "Jebediah Kerman has negative metabolic rate" theory from the fault tree. So the difference would seem to be that OFT-2 had some water in the coolant loop for some reason, and OFT-1 didn't. Another "water intrusion into places where it shouldn't be" kind of issue for Boeing to investigate.
Clearly, a cooling system that fails when the heat load is reduced a couple hundred watts below nominal is unacceptable. For example, spacecraft have plenty of systems redundancy for good reason, and it's essential that multiple inoperative systems that are powered down and no longer emitting heat doesn't have the knock-on effect of causing the cooling system to fail.
Maybe the water in the coolant wouldn't have frozen if there were exothermic meatbags onboard, but that's beside the point and doesn't necessarily speak to the safety of having crew onboard. Calling out the lack of crew as a reasonable-sounding excuse is preying on the relative ignorance of the mass media audience who won't ask "but what about OFT-1?" or whether a cooling system so sensitive to heat load is suitable for a human-rated spacecraft.
The context of that reply was reporters asking if a crew would have exacerbated problem and/or been safe. Boeing gave the correct answer.
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#190
by
TrevorMonty
on 24 May, 2022 19:30
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This is test flight designed to show minor faults. So far no show stoppers.
Sent from my SM-T733 using Tapatalk
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#191
by
Robotbeat
on 24 May, 2022 19:32
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This is test flight designed to show minor faults. So far no show stoppers.
Sent from my SM-T733 using Tapatalk
I wouldn’t say designed to, but I agree, no showstopper.
If the capsule safely returns without any more major problems, I’d expect the next one to be crewed. For all the faults of the first mission, technically it DID land intact and wouldn’t have hurt the crew.
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#192
by
Joffan
on 24 May, 2022 22:28
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Tricky little bit of hatch juggling to get all the catches lined up for closure - zero-g is indeed a different place that can't be simulated easily on Earth. I guess this little re-fitting challenge was a trade-off for the benefit of having a hatch that they can get completely out of the way of the access tunnel.
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#193
by
ulm_atms
on 24 May, 2022 23:07
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Does anyone here know what cooling loop gas/liquid? is made of? I'm wondering if its hydrophobic or hydrophilic? I've seen liquids that can literately pull water out of the air. Ethanol being an example. It's why ethanol and marine environments don't play nice and why most don't use ethanol blended gasoline. Boat motors don't run on water....and yes I made that pun
Just been thinking of all the places water could of gotten in at.
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#194
by
SoftwareDude
on 24 May, 2022 23:34
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On an OFT flight or similar test flight, is the flight strictly performed by operations without the direct involvement of development and test engineers except as standby?
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#195
by
Jim
on 25 May, 2022 00:42
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On an OFT flight or similar test flight, is the flight strictly performed by operations without the direct involvement of development and test engineers except as standby?
the engineers are in a different control center. No different than any other launch of a spacecraft.
Again, trying to find fault.
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#196
by
SoftwareDude
on 25 May, 2022 01:11
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On an OFT flight or similar test flight, is the flight strictly performed by operations without the direct involvement of development and test engineers except as standby?
the engineers are in a different control center. No different than any other launch of a spacecraft.
Again, trying to find fault.
Not trying to find fault, This is not just about Boeing, do the engineers participate in the operations or are they only watching and waiting to be called on in the event of a problem?
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#197
by
king1999
on 25 May, 2022 02:03
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Tricky little bit of hatch juggling to get all the catches lined up for closure - zero-g is indeed a different place that can't be simulated easily on Earth. I guess this little re-fitting challenge was a trade-off for the benefit of having a hatch that they can get completely out of the way of the access tunnel.
Yes I was a bit surprised that they took the hatch completely off which could cause a lot of potential problems during keeping and installation. Probably due to the fact that Starliner is shorter and doesn't have space for a folding mechanism.
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#198
by
AstroWare
on 25 May, 2022 04:55
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Tricky little bit of hatch juggling to get all the catches lined up for closure - zero-g is indeed a different place that can't be simulated easily on Earth. I guess this little re-fitting challenge was a trade-off for the benefit of having a hatch that they can get completely out of the way of the access tunnel.
Yes I was a bit surprised that they took the hatch completely off which could cause a lot of potential problems during keeping and installation. Probably due to the fact that Starliner is shorter and doesn't have space for a folding mechanism.
Are there any minimum time requirements on commercial crew vehicles for emergency ingress and hatch closure?
I think having astronauts inside starliner would have made the process much easier - so not really concerned. Just curious.
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#199
by
spacenut
on 25 May, 2022 13:03
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Is the Capsule coming back today, and if so what time?
