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JF Mezei wrote on Thu, 23 Aug 2018
14:18:13 -0400: On 2018-08-23 06:40, Jeff Findley wrote: During crew ingress, the launch vehicle isn't at all fueled. If this is a recent concession by NASA, it would explain why they still needed those ziplines etc to be installed at a time where they thought pad crews and flight crews would be present at a time the stack was loaded with fuel and LOX. Well, no. I thought they were a silly idea when they did them for the Shuttle. They're sillier now. I believe one of the goals of the ziplines is to get people away from a burning rocket, something which an elevator doesn't do. *unless elevator shaft is fire/bomb proof). Rockets don't 'burn'. They detonate. You're never going to have time to unbutton the capsule, jump in a basket, and zip line to safety. Capsule, basket, and all will be in a big ball of fire. In a new scenario where fueling is done after pad crew has left, the odds or catastropy may be lower but not nill (consider structural failure, premature start of loading of fuel in a sequencce that causes explosion etc etc. The zip line deal was never for 'pad crew'. It was and is for vehicle crew. NASA and SPaceX have measures in place to prevent known problems. The issue is problems that have not been preducted. (look at the explosion because of loading superxooled fuel in the wrong sequence with Helium) Yes, look at that explosion and imagine trying to evacuate the capsule and zip line to safety in the midst of all that. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
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JF Mezei wrote on Thu, 23 Aug 2018
23:21:38 -0400: On 2018-08-23 20:52, Fred J. McCall wrote: Rockets don't 'burn'. They detonate. You're never going to have time to unbutton the capsule, jump in a basket, and zip line to safety. Capsule, basket, and all will be in a big ball of fire. It all depends on how far from the rocket the tower is and when something happens whether the explosion is circumscribed mostly within a certain diametre around the rocket (with "thust" going up instead of the sides). And I would assume that the ET on shuttle would explode differently than kerosene/LOX rockets. If the tower is that far away, there's no need for ground crew to escape and you just blew up most of your own argument. One of the goals of those ziplines was to get people away from the rocket, not just down. (and at bottom were either bunkers or tanks that acted as bunkers) Both, actually. The whole zipline thing assumes people have some warning of thing before they go kablooey. (or perhaps some fueling lines breaking so they evac asap in case this catches on fire without necessarily involving whole stack blowing up). They might as well plan against meteor strike, as it's probably at least as likely as that scenario. The zip line deal was never for 'pad crew'. It was and is for vehicle crew. Sorry, but there was capacity for pad crew. Why would they be expandable with no exit plan when astronauts had zipline ? Sorry, but you need to provide a cite for that. Every description I've seen very specifically says 'astronaut'. In the case of Shuttle, since there was no capsule eject/jesttison, the only means of emergency egress was via hatch and back to tower (assuming bridge"/white room was still there) Yeah. In the name of "we can't do anything that will matter so let's do some theater". With Dragon, having a capsule jettison capability changes things as this becomes the safer means to quickly exit the area in case things go kablooey. But that still leaves pad crews with need for quick exit. Which this system is not intended to provide. Yes, look at that explosion and imagine trying to evacuate the capsule and zip line to safety in the midst of all that. If crews are strapped into capsule, and the problem is just some broken O2 or kerosene pipe with no explosion yet, an evac for safety reason would be different than an explosion where the only way out is to eject capsule. Why evac at all? Turn off the flow and shelter in place. Also, if there is fuel leak without fire, you may not want to activate elevator motors as potential sources of ignition. (not sure is seriosu an issue this would be, but I ccould see a pedantic NASA insisting this is a serious problem) If there is a 'fuel leak without fire' (something I've NEVER heard of happening with ANY rocket) you probably shouldn't be carrying people (or expensive satellites) in the first place. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
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JF Mezei wrote on Sat, 25 Aug 2018
10:54:14 -0400: jettisoning the capsule at best destacks the rocket, at worse destroys stage 2. Hogwash. It removes the CARGO and destroys nothing. The capsule can be replaced in less than a day. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
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JF Mezei wrote on Sun, 26 Aug 2018
11:39:51 -0400: On 2018-08-26 08:59, Jeff Findley wrote: Hogwash. It removes the CARGO and destroys nothing. The capsule can be replaced in less than a day. The way that the SuperDraco engines are canted, I suspect this is true. They're angled *away* from the Falcon 9's upper stage. Surely the initial boost would be straight up, which would protect the launch vehicle from the exhaust. So you agree with McCall that following emergency capsule jettison, the stacks than be put back and launched in less than a day ? Since they intend to be able to build a full stack and relaunch a booster in a day, why would you think it would take any appreciable time to mount a new capsule? When jettisoning from launch pad, is there guidannce to bring capsule down in salt water? or just blind "up, deploy parachutes and land wherever" ? It goes east (when launched on the east coast). Do you never bother to learn ANYTHING before you ask stupid questions? -- "Ignorance is preferable to error, and he is less remote from the truth who believes nothing than he who believes what is wrong." -- Thomas Jefferson |
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JF Mezei wrote on Sun, 26 Aug 2018
23:00:57 -0400: On 2018-08-26 18:04, Fred J. McCall wrote: It goes east (when launched on the east coast). Do you never bother to learn ANYTHING before you ask stupid questions? On the launch pad, it is pointing straight up. So a capsule being jettisoned would go straight up, woudln't it? So payloads get to orbit by going straight up? Uh, no. So what sort of steering would it have (either with the rockets or with parachutes) to direct it to water landing? or would it do a ground landing for such an event ? Again, do you never bother to learn ANYTHING before you ask stupid questions? Super Dracos are throttleable, which means you can shape the trajectory with them. Emergency escapes go for a parachute landing in water. Everyone but you seems to know this. "In August 2014, it was announced that the pad abort test would occur in Florida, at SpaceX's leased pad at SLC-40, and the test was conducted successfully on 6 May 2015. Dragon landed safely in the ocean to the east of the launchpad 99 seconds later." https://en.wikipedia.org/wiki/Dragon_2#Pad_abort_test -- "Ignorance is preferable to error, and he is less remote from the truth who believes nothing than he who believes what is wrong." -- Thomas Jefferson |
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