The decision not to static fire the booster for its third reuse on Starlink 9 (v1.0 launch would seem to indicate that the static fires are finding less issues making the static fire unnecessary.

Quote from: rockets4life97 on 06/13/2020 12:23 pmThe decision not to static fire the booster for its third reuse on Starlink 9 (v1.0 launch would seem to indicate that the static fires are finding less issues making the static fire unnecessary. Maybe not so much that as finding all of the possible issues, so a computer can make the decision in 1/4 second that people were making in a day. I never really could figure out why the same standards carbon based lifeforms used couldn't be considered by software in the time between ignition and liftoff.

With the lastest GPS Scrub, we have now had 4 technical scrubs due to boosters, in 44 launches. 16 launches were new boosters, and 28 old. 3 scrubs were on new boosters. What are the odds of that?launches= 44 scrubs= 4 new boosters= 16 Used boosters= 28 total of 135751 possible casesAssuming a scrub is equally likely, new or used, what are the odds of seeing N scrubs in new boosters?Odds of 0 in new boosters: 1 * 20475 = 20475 cases, odds= 0.150828Odds of 1 in new boosters: 16 * 3276 = 52416 cases, odds= 0.386119Odds of 2 in new boosters: 120 * 378 = 45360 cases, odds= 0.334141Odds of 3 in new boosters: 560 * 28 = 15680 cases, odds= 0.115506Odds of 4 in new boosters: 1820 * 1 = 1820 cases, odds= 0.0134069So if new and used boosters were equally reliable, there is only a 13% chance the scrubs are as skewed as they are towards new boosters. So reasonable evidence that used boosters are less finicky, but hardly conclusive.Note: Only scrubs caused by boosters are counted. Weather, range, second stage, GSE, etc. are not.Booster scrubs mission1046.1 1 Bangabandhu1047.1 0 Telstar 191048.1 0 Iridium/Grace1046.2 0 Merah Putih1049.1 0 Telstar 181048.2 0 SAOCOM1047.2 0 Es'hail1046.3 0 SSO-A1050.1 0 CRS-161054.1 1 GPS-III--- 2019 ---1049.2 0 Iridium1048.2 0 Nusantara Satu1051.1 0 SpX-Dm11052.1 0 FH1053.1 0 FH1055.1 0 FH1056.1 0 CRS-171049.3 0 Starlink1051.2 0 RADARSAT1057.1 0 STP-21052.2 0 STP-21053.2 0 STP-21056.2 0 CRS-181047.3 1 AMOS-17 (extra static fire needed)1048.4 0 Starlink1059.1 0 CRS-191056.3 0 JCSat-18--- 2020 ---1049.4 0 Starlink1046.4 0 Inflight abort1051.3 0 Starlink1056.4 0 Starlink1059.2 0 CRS-201048.5 0 Starlink1051.4 0 Starlink1058.1 0 Crew Dragon1049.5 0 Starlink (?)1059.3 0 Starlink1060.1 0 GPS-III-031058.2 0 Anasis-II1051.5 0 Starlink1049.6 0 Starlink1059.4 0 SAOCOM 1B1060.2 0 Starlink1062.1 1 GPS-III

The correct statistic to use here is the hypergeometric (black and white balls in urn, remember from your stats class?):N=44k=16n=3x=3

I'm having some difficulty understanding the value "44" in the above calculation. Shouldn't this value represent the number of times that there was an opportunity for a technical scrub to occur? So for a mission that scrubbed once and then flew, shouldn't that count as two opportunities for a technical scrub?

Quote from: LouScheffer on 10/03/2020 06:12 pmWith the lastest GPS Scrub, we have now had 4 technical scrubs due to boosters, in 44 launches. 16 launches were new boosters, and 28 old. 3 scrubs were on new boosters. What are the odds of that?launches= 44 scrubs= 4 new boosters= 16 Used boosters= 28 total of 135751 possible casesAssuming a scrub is equally likely, new or used, what are the odds of seeing N scrubs in new boosters?Odds of 0 in new boosters: 1 * 20475 = 20475 cases, odds= 0.150828Odds of 1 in new boosters: 16 * 3276 = 52416 cases, odds= 0.386119Odds of 2 in new boosters: 120 * 378 = 45360 cases, odds= 0.334141Odds of 3 in new boosters: 560 * 28 = 15680 cases, odds= 0.115506Odds of 4 in new boosters: 1820 * 1 = 1820 cases, odds= 0.0134069So if new and used boosters were equally reliable, there is only a 13% chance the scrubs are as skewed as they are towards new boosters. So reasonable evidence that used boosters are less finicky, but hardly conclusive.The correct statistic to use here is the hypergeometric (black and white balls in urn, remember from your stats class?):N=44k=16n=3x=3Cumulative probability of less than three new boosters having been randomly "picked" in such a sample is 0.9577, or in other words:The odds of this happening "by chance" are 4.23%.While this is a small sample size, it's just about statistically significant. If the next two booster scrubs are used boosters, it becomes 5.09%, just outside statistical significance.

With the lastest GPS Scrub, we have now had 4 technical scrubs due to boosters, in 44 launches. 16 launches were new boosters, and 28 old. 3 scrubs were on new boosters. What are the odds of that?launches= 44 scrubs= 4 new boosters= 16 Used boosters= 28 total of 135751 possible casesAssuming a scrub is equally likely, new or used, what are the odds of seeing N scrubs in new boosters?Odds of 0 in new boosters: 1 * 20475 = 20475 cases, odds= 0.150828Odds of 1 in new boosters: 16 * 3276 = 52416 cases, odds= 0.386119Odds of 2 in new boosters: 120 * 378 = 45360 cases, odds= 0.334141Odds of 3 in new boosters: 560 * 28 = 15680 cases, odds= 0.115506Odds of 4 in new boosters: 1820 * 1 = 1820 cases, odds= 0.0134069So if new and used boosters were equally reliable, there is only a 13% chance the scrubs are as skewed as they are towards new boosters. So reasonable evidence that used boosters are less finicky, but hardly conclusive.

Abort on the GPS III launch was caused by an early start on two of the nine first-stage engines.[...] Engines were sent to McGregor, Texas for testing and they were able to reproduce the issue. The problem was traced to a blocked relief valve in the gas generator. There was leftover masking material from the production process.[...]Problematic substance was sort of like nail polish. Only some of the recently produced engines have this problem.