Quote from: LouScheffer on 04/30/2017 02:12 pmFrom the update thread:Quote from: Chris Bergin on 04/30/2017 12:35 pmPer L2 naughty "out of family" sensor that scrubbed the SpaceX Falcon 9 NROL-76 launch was a TOTO (Temperature Ox Tank Outlet) sensor. They had redundancy, but didn't want to risk losing another one, so the "abundance of caution" was as presented. It's not obvious to me why they are worried about losing another such TOTO sensor. If they have a redundant sensor, they know the temperature pre-launch. And once it's in flight, it should not matter if the sensor fails, since there is nothing they can do about it anyway.The only way I can see this being useful at all during flight is if they use it to optimize fuel usage or mixture adjustment. But as far as I know, this is normally done by volume remaining in the tank. They would want both tanks to run out at the same time, independent of the exact temperature of the LOX.I don't agree. My rebreather has three oxygen sensors monitored by one computer and a fourth (identical) one monitored by a fully independent second computer. All monitoring the exact same thing - O2 partial pressure. If one of the three read out of range the computer votes it out of the system. However - what if two read the same and are both wrong? Then the good sensor gets voted out and basically you die. It's a common occurrence. O2 cells from the same batch, mechanical shock, moisture contamination, etc. Point being, they may not know which sensor is giving bad readings. It's not worth betting the company on. (By the way, in rebreathers you have to assume the rig is always trying to kill you and you have to use the computer in your head to make the right decisions. I'm very keyed into the danger of assumption)
From the update thread:Quote from: Chris Bergin on 04/30/2017 12:35 pmPer L2 naughty "out of family" sensor that scrubbed the SpaceX Falcon 9 NROL-76 launch was a TOTO (Temperature Ox Tank Outlet) sensor. They had redundancy, but didn't want to risk losing another one, so the "abundance of caution" was as presented. It's not obvious to me why they are worried about losing another such TOTO sensor. If they have a redundant sensor, they know the temperature pre-launch. And once it's in flight, it should not matter if the sensor fails, since there is nothing they can do about it anyway.The only way I can see this being useful at all during flight is if they use it to optimize fuel usage or mixture adjustment. But as far as I know, this is normally done by volume remaining in the tank. They would want both tanks to run out at the same time, independent of the exact temperature of the LOX.
Per L2 naughty "out of family" sensor that scrubbed the SpaceX Falcon 9 NROL-76 launch was a TOTO (Temperature Ox Tank Outlet) sensor. They had redundancy, but didn't want to risk losing another one, so the "abundance of caution" was as presented.
Quote from: Skyrocket on 04/30/2017 12:17 pmQuote from: Galactic Penguin SST on 04/30/2017 10:37 amQuote from: FutureSpaceTourist on 04/30/2017 10:33 amQuote from: ChrisGebhardt on 04/30/2017 10:09 amNRO PAO. NRO did not directly contract with SpaceX. They contracted with a private company who secured the contract to launch NROL-76 on a Falcon 9.QuoteThe SpaceX NROL-76 launch was not contracted to SpaceX directly by the NRO but through Ball Aerospace.https://twitter.com/nova_road/status/858629314341896192This really sounds like Ball is the spacecraft contractor - and given what they does, points at the payload more likely to be LEO optical reconnaissance, no?Given the ~51° orbit, which is not so well suited for optical payloads, perhaps it is a SAR satellite, perhaps something along the lines of the Ball built Radarsat-1 (http://space.skyrocket.de/doc_sdat/radarsat-1.htm)But it makes a HEO satellite unlikely though, no? I can't recall any Ball bus going to HEO (or GEO for that matter).
Quote from: Galactic Penguin SST on 04/30/2017 10:37 amQuote from: FutureSpaceTourist on 04/30/2017 10:33 amQuote from: ChrisGebhardt on 04/30/2017 10:09 amNRO PAO. NRO did not directly contract with SpaceX. They contracted with a private company who secured the contract to launch NROL-76 on a Falcon 9.QuoteThe SpaceX NROL-76 launch was not contracted to SpaceX directly by the NRO but through Ball Aerospace.https://twitter.com/nova_road/status/858629314341896192This really sounds like Ball is the spacecraft contractor - and given what they does, points at the payload more likely to be LEO optical reconnaissance, no?Given the ~51° orbit, which is not so well suited for optical payloads, perhaps it is a SAR satellite, perhaps something along the lines of the Ball built Radarsat-1 (http://space.skyrocket.de/doc_sdat/radarsat-1.htm)
Quote from: FutureSpaceTourist on 04/30/2017 10:33 amQuote from: ChrisGebhardt on 04/30/2017 10:09 amNRO PAO. NRO did not directly contract with SpaceX. They contracted with a private company who secured the contract to launch NROL-76 on a Falcon 9.QuoteThe SpaceX NROL-76 launch was not contracted to SpaceX directly by the NRO but through Ball Aerospace.https://twitter.com/nova_road/status/858629314341896192This really sounds like Ball is the spacecraft contractor - and given what they does, points at the payload more likely to be LEO optical reconnaissance, no?
Quote from: ChrisGebhardt on 04/30/2017 10:09 amNRO PAO. NRO did not directly contract with SpaceX. They contracted with a private company who secured the contract to launch NROL-76 on a Falcon 9.QuoteThe SpaceX NROL-76 launch was not contracted to SpaceX directly by the NRO but through Ball Aerospace.https://twitter.com/nova_road/status/858629314341896192
NRO PAO. NRO did not directly contract with SpaceX. They contracted with a private company who secured the contract to launch NROL-76 on a Falcon 9.
The SpaceX NROL-76 launch was not contracted to SpaceX directly by the NRO but through Ball Aerospace.
But as far as I know, this is normally done by volume remaining in the tank.
SpaceX has lost two stages to O2 tank overpressure events in the last couple years ... do we *REALLY* think any of us kibitzing on the sidelines has insight into the nuts and bolts of the today's sensor-related scrub and whether it was necessary?I mean, are we seriously discussing this?
"They had redundancy, but didn't want to risk losing another one"
Unless they blow the rocket up on the launch pad again, or in flight, due to the bad sensor. Take no chances. Absolutely unforgiving business. Bad sensor = scrub.
Atlas LOX pump sensor not working properly. Anomaly team being convened.
F9 still vertical on the launch pad as of 21:27L.
Nobody was second guessing anything.We are just trying to understand this sentence Quote"They had redundancy, but didn't want to risk losing another one" On the face of it based on the little information we have that sentence doesn't seem to add up. that's it.
Quote from: mn on 04/30/2017 11:24 pmNobody was second guessing anything.We are just trying to understand this sentence Quote"They had redundancy, but didn't want to risk losing another one" On the face of it based on the little information we have that sentence doesn't seem to add up. that's it. Sure it does. "another one" is the sensor... In aviation for some systems, if you have a triply redundant system you can go if you lose one, as long as you still have two. For other systems, no. For rockets, losing a sensor is an almost automatic stop the process.
Quote from: Lar on 05/01/2017 03:49 amQuote from: mn on 04/30/2017 11:24 pmNobody was second guessing anything.We are just trying to understand this sentence Quote"They had redundancy, but didn't want to risk losing another one" On the face of it based on the little information we have that sentence doesn't seem to add up. that's it. Sure it does. "another one" is the sensor... In aviation for some systems, if you have a triply redundant system you can go if you lose one, as long as you still have two. For other systems, no. For rockets, losing a sensor is an almost automatic stop the process.You are 100% correct, provided the system is needed during flight and a failure of that system during flight would cause a LOMIs that the case here? I hope by the time I log in again this will be irrelevant.
... air flights, where people's lives are at risk, often take off with broken sensors. There is a "minimum equipment list" of stuff that has to be working at takeoff. If it's not on that list you can go with it inoperative.
NROL-76 is going to LEO according to SpaceX's launch license:http://www.space.com/36668-spy-satellite-orbit-spacex-launch-license.htmlI can't yet see the license on the FAA's active license page for commerical launches.
New license docs show #NROL76 is targeting a Low Earth Orbit, ruling out the option of a Molniya Orbit (also in agreement w/ flight profile)
This suggests #NROL76 will complete a demonstration of a new type of radar or optical sensor for future reconnaissance missions.
Quote from: Galactic Penguin SST on 04/30/2017 10:37 amQuote from: FutureSpaceTourist on 04/30/2017 10:33 amQuote from: ChrisGebhardt on 04/30/2017 10:09 amNRO PAO. NRO did not directly contract with SpaceX. They contracted with a private company who secured the contract to launch NROL-76 on a Falcon 9.QuoteThe SpaceX NROL-76 launch was not contracted to SpaceX directly by the NRO but through Ball Aerospace.https://twitter.com/nova_road/status/858629314341896192This really sounds like Ball is the spacecraft contractor - and given what they does, points at the payload more likely to be LEO optical reconnaissance, no?Seems unusual for the NRO to reveal the spacecraft contractor.
Vapors at the Falcon 9. Fueling is UNDERWAY!