Quote from: jpo234 on 08/15/2018 09:42 pmQuote from: vt_hokie on 08/15/2018 05:29 pmI hope there's a safeguard for the cut mains beyond just the "use only after landing" warning next to the button!They would still have the Super Dracos. Could they be used for a powered landing in an emergency (like originally planned)? I wouldn't bet on it.
Quote from: vt_hokie on 08/15/2018 05:29 pmI hope there's a safeguard for the cut mains beyond just the "use only after landing" warning next to the button!They would still have the Super Dracos. Could they be used for a powered landing in an emergency (like originally planned)?
I hope there's a safeguard for the cut mains beyond just the "use only after landing" warning next to the button!
Quote from: woods170 on 08/16/2018 06:30 amQuote from: jpo234 on 08/15/2018 09:42 pmQuote from: vt_hokie on 08/15/2018 05:29 pmI hope there's a safeguard for the cut mains beyond just the "use only after landing" warning next to the button!They would still have the Super Dracos. Could they be used for a powered landing in an emergency (like originally planned)? I wouldn't bet on it.Perhaps, the Super Dracos could be used (in an emergency) for a land-landing (similar to Soyuz)?
Quote from: yg1968 on 08/17/2018 03:36 pmQuote from: woods170 on 08/16/2018 06:30 amQuote from: jpo234 on 08/15/2018 09:42 pmQuote from: vt_hokie on 08/15/2018 05:29 pmI hope there's a safeguard for the cut mains beyond just the "use only after landing" warning next to the button!They would still have the Super Dracos. Could they be used for a powered landing in an emergency (like originally planned)? I wouldn't bet on it.Perhaps, the Super Dracos could be used (in an emergency) for a land-landing (similar to Soyuz)?I highly doubt it. I don't know what the land landing g-loads would be, but I doubt that the super dracos are necessary to keep them below contingency limits. Since they're hypergolic thrusters (as opposed to Soyuz's solid motors), firing them so close to the ground would require decontamination and safing of the area before crew could be extracted -- exactly what you don't want to have to deal with in an emergency situation.
Quote from: yg1968 on 08/17/2018 03:36 pmPerhaps, the Super Dracos could be used (in an emergency) for a land-landing (similar to Soyuz)?I highly doubt it. I don't know what the land landing g-loads would be, but I doubt that the super dracos are necessary to keep them below contingency limits. Since they're hypergolic thrusters (as opposed to Soyuz's solid motors), firing them so close to the ground would require decontamination and safing of the area before crew could be extracted -- exactly what you don't want to have to deal with in an emergency situation.
Perhaps, the Super Dracos could be used (in an emergency) for a land-landing (similar to Soyuz)?
Quote from: SWGlassPit on 08/17/2018 03:56 pmQuote from: yg1968 on 08/17/2018 03:36 pmPerhaps, the Super Dracos could be used (in an emergency) for a land-landing (similar to Soyuz)?I highly doubt it. I don't know what the land landing g-loads would be, but I doubt that the super dracos are necessary to keep them below contingency limits. Since they're hypergolic thrusters (as opposed to Soyuz's solid motors), firing them so close to the ground would require decontamination and safing of the area before crew could be extracted -- exactly what you don't want to have to deal with in an emergency situation.I would prefer that over slamming into the ground at terminal velocity.
Quote from: SWGlassPit on 08/17/2018 03:56 pmQuote from: yg1968 on 08/17/2018 03:36 pmQuote from: woods170 on 08/16/2018 06:30 amQuote from: jpo234 on 08/15/2018 09:42 pmQuote from: vt_hokie on 08/15/2018 05:29 pmI hope there's a safeguard for the cut mains beyond just the "use only after landing" warning next to the button!They would still have the Super Dracos. Could they be used for a powered landing in an emergency (like originally planned)? I wouldn't bet on it.Perhaps, the Super Dracos could be used (in an emergency) for a land-landing (similar to Soyuz)?I highly doubt it. I don't know what the land landing g-loads would be, but I doubt that the super dracos are necessary to keep them below contingency limits. Since they're hypergolic thrusters (as opposed to Soyuz's solid motors), firing them so close to the ground would require decontamination and safing of the area before crew could be extracted -- exactly what you don't want to have to deal with in an emergency situation.could fire in the event of a chute loss to lessen the vehicle mass.
Can anyone confirm or deny that even though there are no plans to use the super dracos for landing that the capability to do so does still exist.
Quote from: clongton on 08/17/2018 05:02 pmCan anyone confirm or deny that even though there are no plans to use the super dracos for landing that the capability to do so does still exist.The software for it was in early stages of develpment, with prototype versions of it being active on the Crew Dragon hover tests that were witnessed at McGregor.I highly doubt that an operational version of it, if only for emergency use, exists in the DM-1 and DM-2 flight software.A definitive answer to your question can be given by inside SpaceX personnel only, either in public of via the usual leaks.But consider this: why do you think a fourth chute was added? Why do you think the parachute system for Crew Dragon is going thru an extremely rigorous qualification program, despite the fact that the same basic parachute system (minus one chute) has been successfully used on over a dozen Cargo Dragon missions?It is to make sure that the parachute sequence will ALWAYS work when commanded to do so. Much the same for Starliner and Orion.
NASA’s Commercial Crew Program and SpaceX are finalizing plans for launch day operations as they prepare for the company’s first flight test with astronauts on board. The teams are working toward a crew test flight to the International Space Station, known as Demo-2, with NASA astronauts Bob Behnken and Doug Hurley in April 2019. A key question the program and the company have been assessing is whether the astronauts will climb aboard the Crew Dragon spacecraft before or after SpaceX fuels the Falcon 9 rocket. NASA has made the decision to move forward with SpaceX’s plan to fuel the rocket after the astronauts are in place. While the agreement makes this plan the baseline for operations, it is contingent upon NASA’s final certification of the operation.“To make this decision, our teams conducted an extensive review of the SpaceX ground operations, launch vehicle design, escape systems and operational history,” said Kathy Lueders, manager of NASA’s Commercial Crew Program. “Safety for our personnel was the driver for this analysis, and the team’s assessment was that this plan presents the least risk.”Additional verification and demonstration activities, which include five crew loading demonstrations of the Falcon 9 Block 5, will be critical to final certification of this plan. These loading demonstrations will verify the flight crew configuration and crew loading timeline prior to Demo-2. After these conditions have been met, NASA will assess any remaining risk before determining that the system is certified to fly with crew.If all goes according to plan, on launch day, the Falcon 9 composite overwrap pressure vessels, known as COPVs, will be loaded with helium and verified to be in a stable configuration prior to astronaut arrival at the launch pad. The astronauts then will board the spacecraft about two hours before launch, when the launch system is in a quiescent state. After the ground crews depart the launch pad, the launch escape systems will be activated approximately 38 minutes before liftoff, just before fueling begins. SpaceX launch controllers then will begin loading rocket grade kerosene and densified liquid oxygen approximately 35 minutes before launch. The countdown and launch preparations can be stopped automatically up to the last moment before launch. In the unlikely event of an emergency at any point up to and after launch, the launch escape systems will allow the astronauts to evacuate safely.This timeline is consistent with the fueling procedures SpaceX uses for its commercial resupply missions and satellite launches.The crew launches of NASA’s Commercial Crew partners SpaceX and Boeing will return the nation’s ability to launch our astronauts from the United States to and from the International Space Station on American spacecraft.
Parachutes are pretty reliable, so it would almost certainly never be used. But the only reason I can think of to not load that software for an emergency is if they are planning to burn or vent the hypergols before popping the chutes. Otherwise it's always better to have the option, and not need it, than to need it and not have it.
NASA, SpaceX Agree on Plans for Crew Launch Day OperationsQuoteNASA’s Commercial Crew Program and SpaceX are finalizing plans for launch day operations as they prepare for the company’s first flight test with astronauts on board. The teams are working toward a crew test flight to the International Space Station, known as Demo-2, with NASA astronauts Bob Behnken and Doug Hurley in April 2019. A key question the program and the company have been assessing is whether the astronauts will climb aboard the Crew Dragon spacecraft before or after SpaceX fuels the Falcon 9 rocket. NASA has made the decision to move forward with SpaceX’s plan to fuel the rocket after the astronauts are in place. While the agreement makes this plan the baseline for operations, it is contingent upon NASA’s final certification of the operation.“To make this decision, our teams conducted an extensive review of the SpaceX ground operations, launch vehicle design, escape systems and operational history,” said Kathy Lueders, manager of NASA’s Commercial Crew Program. “Safety for our personnel was the driver for this analysis, and the team’s assessment was that this plan presents the least risk.”Additional verification and demonstration activities, which include five crew loading demonstrations of the Falcon 9 Block 5, will be critical to final certification of this plan. These loading demonstrations will verify the flight crew configuration and crew loading timeline prior to Demo-2. After these conditions have been met, NASA will assess any remaining risk before determining that the system is certified to fly with crew.If all goes according to plan, on launch day, the Falcon 9 composite overwrap pressure vessels, known as COPVs, will be loaded with helium and verified to be in a stable configuration prior to astronaut arrival at the launch pad. The astronauts then will board the spacecraft about two hours before launch, when the launch system is in a quiescent state. After the ground crews depart the launch pad, the launch escape systems will be activated approximately 38 minutes before liftoff, just before fueling begins. SpaceX launch controllers then will begin loading rocket grade kerosene and densified liquid oxygen approximately 35 minutes before launch. The countdown and launch preparations can be stopped automatically up to the last moment before launch. In the unlikely event of an emergency at any point up to and after launch, the launch escape systems will allow the astronauts to evacuate safely.This timeline is consistent with the fueling procedures SpaceX uses for its commercial resupply missions and satellite launches.The crew launches of NASA’s Commercial Crew partners SpaceX and Boeing will return the nation’s ability to launch our astronauts from the United States to and from the International Space Station on American spacecraft.
COPVs, will be loaded with helium and verified to be in a stable configuration prior to astronaut arrival at the launch pad. The astronauts then will board the spacecraft about two hours before launch
This timeline is consistent with the fueling procedures SpaceX uses for its commercial resupply missions and satellite launches.
COPVs being loaded with helium more than 2 hours before launch is new isn't it?
NASA, SpaceX Agree on Plans for Crew Launch Day Operations...If all goes according to plan, on launch day, the Falcon 9 composite overwrap pressure vessels, known as COPVs, will be loaded with helium and verified to be in a stable configuration prior to astronaut arrival at the launch pad. The astronauts then will board the spacecraft about two hours before launch, when the launch system is in a quiescent state. After the ground crews depart the launch pad, the launch escape systems will be activated approximately 38 minutes before liftoff, just before fueling begins. SpaceX launch controllers then will begin loading rocket grade kerosene and densified liquid oxygen approximately 35 minutes before launch. The countdown and launch preparations can be stopped automatically up to the last moment before launch. In the unlikely event of an emergency at any point up to and after launch, the launch escape systems will allow the astronauts to evacuate safely....
Quote from: Rondaz on 08/18/2018 06:40 amNASA, SpaceX Agree on Plans for Crew Launch Day Operations...If all goes according to plan, on launch day, the Falcon 9 composite overwrap pressure vessels, known as COPVs, will be loaded with helium and verified to be in a stable configuration prior to astronaut arrival at the launch pad. The astronauts then will board the spacecraft about two hours before launch, when the launch system is in a quiescent state. After the ground crews depart the launch pad, the launch escape systems will be activated approximately 38 minutes before liftoff, just before fueling begins. SpaceX launch controllers then will begin loading rocket grade kerosene and densified liquid oxygen approximately 35 minutes before launch. The countdown and launch preparations can be stopped automatically up to the last moment before launch. In the unlikely event of an emergency at any point up to and after launch, the launch escape systems will allow the astronauts to evacuate safely....OK, if helium is loaded PRIOR to LOX, it means helium is at ambient T. Sincep*V = n*R*Tthenn1 * T1 = n2 * T2where indexes 1 and 2 stand for ambient temperature ("1") and temperature of over-chilled LOX ("2") and "n" - total amount of He (in mols).Let's take T1 = 300 K (27°C) and T2 = 70 K (-203°C)thenn1 = 0.23 n2or, in other wordsat ambient T (27°C) you can load COPV to only about 23% of what it can hold (to the same pressure limit) at temperature of over-chilled LOX...
"Quiescent state" means nothing is changing. The temperature of the helium is not necessarily at 27C. If it is being topped off constantly, the temperature could be much lower but steady.