Author Topic: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION  (Read 219210 times)

Offline Johnnyhinbos

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #320 on: 04/30/2017 11:34 AM »
So much for the two launch a month cadence...
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Offline old_sellsword

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #321 on: 04/30/2017 11:35 AM »
Hey Chris, what exactly did you mean by this post?

Also, webcast would confirm if this is the first flight of the new Block upgrade Falcon 9.

That the webcast telemetry would should a thrust increase? Or that the host(s) would tell us about an upgrade? Something else?

Online ChrisGebhardt

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #322 on: 04/30/2017 11:37 AM »
Hey Chris, what exactly did you mean by this post?

Also, webcast would confirm if this is the first flight of the new Block upgrade Falcon 9.

That the webcast telemetry would should a thrust increase? Or that the host(s) would tell us about an upgrade? Something else?

The webcast would/will confirm if this is the first flight of the new Falcon 9 1st stage with higher thrust engines.

Offline Lar

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #323 on: 04/30/2017 11:40 AM »
So much for the two launch a month cadence...

That's not really fair, NRO caused the majority of the slip. I think we have to let SpaceX slide on a one day. (if it grows... ok, phasers on whinge!!!! )... because if they go a nominal 12 or even 14 days between launches (planned) a one day slip still is 2 launches a month...
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Online ChrisGebhardt

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #324 on: 04/30/2017 11:53 AM »
So much for the two launch a month cadence...

That's not really fair, NRO caused the majority of the slip. I think we have to let SpaceX slide on a one day. (if it grows... ok, phasers on whinge!!!! )... because if they go a nominal 12 or even 14 days between launches (planned) a one day slip still is 2 launches a month...

And if they go 1 May (or even 2 May) for NROL-76, that still preserves 15 May for Inmarsat and 31 May for CRS-11... which would be three in one month.

Offline southshore26

Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #325 on: 04/30/2017 11:57 AM »
SpaceX never seems to launch and RTLS when the weather is this pretty.

Sent from my LG-H850 using Tapatalk

Clarify pretty... it was pouring rain at Jetty Park at launch time.

Offline Skyrocket

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #326 on: 04/30/2017 12:17 PM »
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.

Quote
The SpaceX NROL-76 launch was not contracted to SpaceX directly by the NRO but through Ball Aerospace.

https://twitter.com/nova_road/status/858629314341896192

This 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)

Offline Jcc

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #327 on: 04/30/2017 01:07 PM »
So much for the two launch a month cadence...
May could have 3.

Offline M.E.T.

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #328 on: 04/30/2017 01:11 PM »
So much for the two launch a month cadence...
May could have 3.

Well, to also be fair, 3 in one month doesn't meet their stated goal if there were zero in the previous month. But agreed, most of the NROL delay was out of their control.


Offline Jim

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #329 on: 04/30/2017 01:33 PM »
Payload issues are part of the launch cadence. 

Offline M.E.T.

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #330 on: 04/30/2017 01:49 PM »
Payload issues are part of the launch cadence.

Yep. And I guess that's why a sustained high launch cadence cannot really be maintained while they are largely reliant on a single launch facility for the majority of their launches.

Once LC40 is up and running I imagine that a planned two week turnaround time per launch pad might, after catering for payload delays, technical scrubs and other unplanned range issues, result in a combined launch cadence of about 2 launches per month. Excluding any bonus launches from Vandenberg.


Offline Norm38

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #331 on: 04/30/2017 02:07 PM »
Given this was a new first stage, I'm interested what the sensor failure root cause could be. Infant mortality, installation error, completely random failure?
Is this an instance where a "flight proven" first stage could be more reliable?

If these sensors do just fail, then maybe they need 3 for redundancy instead of two.

Online LouScheffer

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #332 on: 04/30/2017 02:12 PM »
From the update thread:
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.
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.


Offline Johnnyhinbos

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #333 on: 04/30/2017 02:26 PM »
From the update thread:
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.
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)
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Offline SpacedX

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #334 on: 04/30/2017 02:27 PM »
From the update thread:
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.
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.

Proper characterization of the failure will impact future launches' reliability.

Online gosnold

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #335 on: 04/30/2017 02:31 PM »
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.

Quote
The SpaceX NROL-76 launch was not contracted to SpaceX directly by the NRO but through Ball Aerospace.

https://twitter.com/nova_road/status/858629314341896192

This 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).

Online LouScheffer

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #336 on: 04/30/2017 02:54 PM »
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.
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.
Proper characterization of the failure will impact future launches' reliability.
Traditionally, this would have made sense.  But now it's old, expendable rocket thinking.  They can characterize the failure after the booster returns.

Online edkyle99

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #337 on: 04/30/2017 03:06 PM »
Traditionally, this would have made sense.  But now it's old, expendable rocket thinking.  They can characterize the failure after the booster returns.
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. 

 - Ed Kyle
« Last Edit: 04/30/2017 03:06 PM by edkyle99 »

Online edkyle99

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #338 on: 04/30/2017 03:09 PM »
Ball makes small sats. Its only moderately heavy payloads have been Worldview 2 and 3, with a mass of 2600 kg.
They've never made a 5000 kg sat, for example, unlike the major sat builders.

So I am speculating NROL-76 is quite small, under 3000 kg.
A lightweight payload might allow SpaceX to do some Stage 2 R&D work.  We've noticed that this second stage looks a bit different than previous v1.2 second stages.  Maybe it will do something post spacecraft separation, part of an effort leading toward direct MEO or GEO insertions for EELV someday or somesuch.  GPS inclinations are, what, 55 degrees?  Second stage restarts are 3+ hours after launch.

 - Ed Kyle
« Last Edit: 04/30/2017 03:19 PM by edkyle99 »

Online yokem55

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Re: SpaceX Falcon 9 - NROL-76 - May 1, 2017 - DISCUSSION
« Reply #339 on: 04/30/2017 03:27 PM »
From the update thread:
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.
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.
Speculation: This is an outlet temperature sensor, so as the sub cooled lox is leaving the tank, that temperature might be used to inform the turbopumps exactly how hard they have to run to get a certain amount of mass flow of LOX into the chamber to get the desired thrust.

If the same problem that caused the first sensor to fail causes the backup sensor to fail, then the TP's have no good way to tell how warm the lox has gotten during the flight and could end up pumping too much or too little lox into the chambers.

Bottom line, backups are great to have when you have no other choice than to use them. But if the count can still be stopped, then make the choice to figure out why the primary has failed.

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