Quote from: Brovane on 12/18/2018 03:29 pmHasn't it been a while since SpaceX has had a hold like this in the final 10-mins of countdown? Bangabandhu had a scrub at T-58But you're right. Nothing else like that in a while. SpaceX has been in a pretty smooth run.
Hasn't it been a while since SpaceX has had a hold like this in the final 10-mins of countdown?
these new boosters are always so finicky on their first launch...- grid fins on CRS-16- sensors on GPSIIII think we might begin to witness the positive effect of "flight proven" being turned around against all these "untested" boosters there's ever only so much you can test in component tests, dress rehearsal or even a hold down hot fire.
How are the upper level winds looking for tomorrow?
Quote from: CorvusCorax on 12/18/2018 05:14 pmthese new boosters are always so finicky on their first launch...- grid fins on CRS-16- sensors on GPSIIII think we might begin to witness the positive effect of "flight proven" being turned around against all these "untested" boosters there's ever only so much you can test in component tests, dress rehearsal or even a hold down hot fire.Not true. a. We don't know if it is a bad temp sensor on GPS IIIb. There isn't a difference between on time and flight time.c. Can't say that the grid fin failure was due to infant mortality, poor workmanship (which still applies to a refurb booster), effects from second stage engine.
Not true. a. We don't know if it is a bad temp sensor on GPS IIIb. There isn't a difference between on time and flight time.c. Can't say that the grid fin failure was due to infant mortality, poor workmanship (which still applies to a refurb booster), effects from second stage engine.
“For this first launch for GPS, we’re given particular parameters in terms of where we have to put them into orbit, as well as what we have in terms of how much weight does the spacecraft have,” said Walter Lauderdale, the GPS 3 SV01 mission director from the Air Force’s Space and Missile Systems Center Launch Enterprise Systems Directorate. “And in doing that mission design to include a re-entry to dispose of the second stage, all those taken together levy performance requirements on the Falcon 9 launch vehicle, (and) as it went through mission design, there simply was not enough performance reserve to meet our requirements and allow them — for this mission — to bring the first stage back, as they’ve been doing quite successfully.”The first GPS 3-series satellite also weighs more than initially planned after managers opted to load extra fuel into the spacecraft, a move that will give the mission added “resiliency,” said Col. Steve Whitney, director of the Global Positioning Systems Directorate at the Air Force’s Space and Missile Systems Center.The additional fuel load gives the GPS 3 SV01 spacecraft a launch weight of around 9,700 pounds, or 4,400 kilograms, according to Whitney. That’s more than a half-ton above the satellite’s originally expected weight.“We added some additional fuel for some mission capabilities to make sure that the system is going to perform,” Whitney said.
It seems they are still unsure what caused the scrub yesterday
Quote from: Jim on 12/19/2018 01:14 amNot true. a. We don't know if it is a bad temp sensor on GPS IIIb. There isn't a difference between on time and flight time.c. Can't say that the grid fin failure was due to infant mortality, poor workmanship (which still applies to a refurb booster), effects from second stage engine.Jim, are you working this mission? If so, good luck! If not, how do you interprete the scrub notice on countdown net?
A: No, indeed we don`t, but some of the other speculated explanations ( insulation issue, LOX leak, ... ) don`t make it any better. Only thing we know for a fact is, SpaceX had to hold the countdown for a technical reason, which they haven't in a long time, flying lots of reused boosters.
B: Except vibration, G-loads, Thermal stress, Pressure difference, interactions between systems, etc, pp, ..., ..., ...
C: You forgot hydraulic fluid contamination. If a pump fails, that`d be a prime suspect
Quote from: CorvusCorax on 12/19/2018 07:38 amA: No, indeed we don`t, but some of the other speculated explanations ( insulation issue, LOX leak, ... ) don`t make it any better. Only thing we know for a fact is, SpaceX had to hold the countdown for a technical reason, which they haven't in a long time, flying lots of reused boosters.There are a lot of facts we know that can be used to support many wrong conclusions.Also, there were many times that Spacex wasn't able to enter a countdown due to technical reasons and just pushed off the launch attempt to the next day.
Quote from: CorvusCorax on 12/19/2018 07:38 amB: Except vibration, G-loads, Thermal stress, Pressure difference, interactions between systems, etc, pp, ..., ..., ...No. We are not talking about a sensor that operates during flight. This was during preflight and this sensor is not needed for flight."vibration, G-loads, ........, Pressure difference, .... etc, pp, ..., ..., ..." only affect reuse and not first use of this sensor. The sensor has already seen "Thermal stress, Pressure difference, interactions between systems," during tests at McGegor and static fire. So you point about reflight vetted this sensor holds no water.
Quote from: CorvusCorax on 12/19/2018 07:38 amC: You forgot hydraulic fluid contamination. If a pump fails, that`d be a prime suspect More likely to occur the more times the system is serviced.
Quote from: Jim on 12/19/2018 01:25 pmQuote from: CorvusCorax on 12/19/2018 07:38 amC: You forgot hydraulic fluid contamination. If a pump fails, that`d be a prime suspect More likely to occur the more times the system is serviced.Bath tub curve! Reliability of a system over time can be modelled as an overlay of individual component and failure cases. Theres 3 classes of failures.1. Random occuring flaws. These have a constant propability over time/cycles. That includes operational/handling flaws such as a mechanic droppung a part, screwing it in too tight, putting it the wrong way around. Or bird strikes in flight.Statistically that kinda stuff is just as likely on the very first flight as on the 100th and just gives the bathtub curce a static offset above zero.2. Inherent design or production flaws. Something isn't designed the way it should be or has a manufacturing flaw. These have the highest chance to appear on the very first cycle, but every cycle weeds them out. The chance of such a flaw surfacing drops to a fraction with each further cycle, so it starts from a constant and drops exponentially.3. Accumulating flaws. Aka wear and tear. The longer a system is used, the worse it becomes until it no longer meets design specs and fails. This probability starts at close to zero and has a sigmoid jump to almost one after a fail-cycle design time. In an ideal world, each cycle would put the exact same wear on each item and all items would be identical, so it would be a step function after that many cycles. In the real world, quality of items and wear each cycle follow a gaussian curve, which leads to a sigmoid, flattened curve shape.Overlay all 3 curves of all subsystems and all possuble failure cases and you get the bathtub curve.Your servicing issues could lead to either of the 3. But the bathtub curces shape as a whole is in favor of reuse.
East coast fairing boat Go Pursuit was prepared on Tuesday's launch attempt in intended hazard area for fairing water landing attempt. Yesterday traveled back to nearest port of Morehead City to wait for next attempt. To return to this area needs approximately 18 hours. Despite of today's next planned attempt, this fairing carrier is still waiting in this port - indicates, that apparently due to the weather is today's launch clearly not on his schedule.
