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SpaceX Dragon 2 In Flight Abort Test
Currently the SpaceX Dragon 2 In Flight Abort Test is scheduled for this
Saturday at 8:00 a.m. There is a four hour window for the test. The reason there is a four hour window is that since it's not going into orbit, it's not critical they launch "on time". I'm sure this will be live-streamed by people like @EverydayAstronaut https://everydayastronaut.com/ https://www.youtube.com/channel/UC6u...J1R2HMTY3LIx5Q Hopefully it will be on NASA TV and possibly a live stream from SpaceX as well. Cites: SpaceNews.com SpaceX ready for Crew Dragon in-flight abort test by Jeff Foust https://spacenews.com/spacex-ready-f...ht-abort-test/ SpaceX on final lap in the commercial crew space race Rachael Joy, Florida Today https://www.floridatoday.com/story/t.../01/14/spacexs -flight-abort-test-final-milestone-before-crewed-flight/2835391001/ Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
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SpaceX Dragon 2 In Flight Abort Test
"JF Mezei" wrote in message ...
On 2020-01-14 07:04, Jeff Findley wrote: I'm sure this will be live-streamed by people like @EverydayAstronaut Wouldn't SpaceX live stream it? I would expect nothing less than views from many on-board cameras. A good disaster movie :-) I assume SpaceX will have a feed. But as I recall @EverydayAstronaut often has better commentary. I take it the ejection will happen at MaxQ? At that altitude, can aircraft assets film the event? Yes, it will happen at MaxQ. Will Stage1 come back to land? Only if any pieces wash up on shore. What is the impact on Stage1 upon Dragon2 popping out? Is it a survivable event where Stage1 could cut off engines, start falling and then aim for the drone ship? No, this is expected to be a "rapid scheduled disassembly event". If "firing in the whole" (not really) doesn't break it up, atmospheric disturbances will. And if it survives that, hitting the water will ensure an RSDE. Or does separation happening in "thick" atmosphere result in Stage1 hitting atmosphere in the wrong angle and causing breakup and fireworks? Or are they actually going to detonate Stage1 prior to the abort and also test the software/sensors that will automatically trigger the Dragon abort? No. We've been over this. -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net IT Disaster Response - https://www.amazon.com/Disaster-Resp...dp/1484221834/ |
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SpaceX Dragon 2 In Flight Abort Test
In article ,
says... On 2020-01-14 07:04, Jeff Findley wrote: I'm sure this will be live-streamed by people like @EverydayAstronaut Wouldn't SpaceX live stream it? I would expect nothing less than views from many on-board cameras. A good disaster movie :-) I take it the ejection will happen at MaxQ? At that altitude, can aircraft assets film the event? I understand that the abort will actually happen at the time of maximum drag, which isn't exactly maximum aerodynamic pressure. But, the two are "close enough" that people just keep saying MaxQ. Will Stage1 come back to land? Absolutely not. It will be destroyed by the test. The first stage has no grid fins or landing legs. The Falcon 9 first stage will be simulating an abort, which means that its engines will all shut down. So it will have little control authority when Dragon 2 aborts. This will expose the (blunt) top of the 2nd stage directly to airflow, including exhaust from the Super Dracos. This will no doubt cause the booster to tumble. It will therefore break up quite quickly due to aerodynamic forces because launch vehicles that are very tall and thin (fineness ratio) are simply not designed to fly sideways through the air near the portion of the flight where it experiences maximum aerodynamic pressure. What is the impact on Stage1 upon Dragon2 popping out? Is it a survivable event where Stage1 could cut off engines, start falling and then aim for the drone ship? See above. Or if you like here's a cite: SpaceX test-fires rocket ahead of Crew Dragon in-flight abort test January 11, 2020 Stephen Clark https://spaceflightnow.com/2020/01/1...cket-ahead-of- crew-dragon-in-flight-abort-test/ Or does separation happening in "thick" atmosphere result in Stage1 hitting atmosphere in the wrong angle and causing breakup and fireworks? Again, the top of the 2nd stage will be directly exposed to airflow. It is simply not designed for this. Or are they actually going to detonate Stage1 prior to the abort and also test the software/sensors that will automatically trigger the Dragon abort? I don't believe they're going to "detonate" stage 1 because it won't have a chance to do so. On a crewed flight, the detonation would not be commanded until after the Dragon 2 has time enough to escape. Falcon will quite likely be torn apart by aerodynamic forces long before it has a chance to self destruct. Falcon 9 does have destruct devices. It also has an automated destruct system that has been used on uncrewd flights. This article describes that system: https://www.floridatoday.com/story/t.../03/11/spacex- autonomous-flight-safety-system-afss-kennedy-space-center-florida- falcon9-rocket-air-force-military/98539952/ At the time this article was written, NASA had not yet decided if it would use the aforementioned automated system on crewed flights. From the article above: NASA's Commercial Crew Program is reviewing the system and has not yet accepted it. "If done correctly, an automated system is actually safer, more reliable than having a human in the loop," said Kennedy Space Center Director Bob Cabana. "We've still got some work to do before Commercial Crew is going to certify that this is the way to go, but this is the future." Cabana, a four-time shuttle astronaut, remembered how shuttle crews before launches would meet with the Range safety personnel who could decide their fate. "We used to go visit the guys that sat on console that would push the button and show them pictures of our kids and get to know them," he said. So, it's not clear to me whether or not crewed Dragon 2 flights will use the automated system, or whether an actual range safety officer will have to "push the button". Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
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SpaceX Dragon 2 In Flight Abort Test
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SpaceX Dragon 2 In Flight Abort Test
In article ,
says... On 2020-01-16 07:55, Jeff Findley wrote: No. In the case of any abort during first stage burn, the Falcon 9 simultaneously shuts down the engines and sends the "GTFO" signal to Dragon 2 to initiate its abort. Pedantic question: You had mentioned shutdown of engines and GTFO happen simultaneously. Is that absolutely at same time, or is there a short pause between sending command to engines and sending command to Dragon? (to give engines time to initiate shutdown). If not, wouldn't Drago essentiall launch off Falcon9 with Falcon9 engines still at full thrust? NASA knows the details of this for sure. But I believe that the Super Draco engines are sized to pull Dragon 2 away from Falcon 9 at the same time the engines are shutting down. Cite: SpaceX delays dramatic Crew Dragon abort test due to high winds and rough seas. BY WILLIAM HARWOOD, JANUARY 18, 2020 / 7:05 AM / CBS NEWS https://www.cbsnews.com/news/spacex-...nch-in-flight- abort-test-to-prove-crew-ship-safe-delay-2020-01-18/ From the article: The Falcon's engines will shut down as the Crew Dragon's eight Super Draco abort engines ignite, pushing the capsule away from the now-powerless booster with an acceleration a race car driver would envy. Within just a few seconds, the spacecraft will reach a relative velocity of some 430 mph, subjecting two heavily instrumented astronaut test dummies to more than four times the normal force of gravity. Sounds simultaneous to me. Also, shutting down the liquid fueled engines should only take a fraction of a second anyway. Also note the acceleration of more than 4 Gs that Dragon 2 will experience while the Super Dracos are firing at full thrust. This is much more acceleration than would normally be experienced during that part of the flight, so that would no doubt be sufficient acceleration to pull away from a Falcon 9 that's still firing (even though that won't ever happen). Also, in cases where the rocket veers off course, is range safety totally eparate from abort and only triggered from ground? or can the stage 1 initiate it by itself? I posted another article on Falcon 9's automatic abort system. This system eliminates the need for anyone on the ground to do anything as it will terminate thrust and destruct the vehicle. This article also said NASA was still evaluating its use on crewed flights. So you'd have to ask NASA. And theoretically, can ground initiate range safety with the crewed capsule still attached? or would range safety command, ujpon reception by the Falcon 9, initiate the abort if it wasn't fonr already and then light up the fireworks? No one in their right mind would destruct a vehicle with a crewed capsule still attached (automated or manual). But to verify, you'd have to ask NASA. or is range safety such that once triggered, Falcon9 will detect anomaly, initiate the abort and Dragon 2 will be out before the fireworks have reached the top of the stack? Thrust termination and destruction are two separate events. No doubt on a crewed flight thrust termination would come first (simultaneous with telling Dragon 2 to abort). Destruction of Falcon 9 would happen later. But destruction of Falcon 9 will likely be moot since aerodynamic forces will rip it apart before the deliberate destruct happens. Remember Challenger. It was ripped apart *very* quickly by aerodynamic forces. Falcon 9 will face the exact same fate. Out of curiosity, how do they measure how much thrust is produced by each engine? A sensor that measures pressure against the wall of the engine bell? An electronic scale measuring "weight" of engine against the mounting brackets of the stage? Or is thrust assumed from speed of turbopumps (fuel flow)? You'd have to ask SpaceX. But suffice it to say that there are enough sensors such that there are many ways you'd verify the engine is working properly. When something goes wrong with a first stage engine, the Falcon 9 computers will know this and shut down that one engine, compensate for loss of thrust with the other engines, and the flight will continue. An upper stage engine failure is different since there is only one Vacuum Merlin on the upper stage. Abort for Dragon 2 during first stage burn (which is what this abort simulates) will only happen for some sort of massive failure. I assume that thrust from each engine is a huge component for the "abort scenario" software in terms of not only detecting non-nominal engine, but also deciding if flight can continue? ex: loss of 2 engines on same side vs loss of 2 engines opposite each other). You'd have to ask SpaceX. Since there has only been loss of thrust on one Merlin engine in flight on all of the flights of Falcon 9, I'd say the demonstrated reliability of the engine (and the armor between them) makes failure of more than one engine on the first stage *very* unlikely. Still, the Dragon 2 abort system is there in case of such an unlikely event. That's one advantage of having a liquid fueled stage rather than SRBs (which are harder to shut down reliably without a lot of transient forces being sent through the stack). I take it the SLS SRBs have "zipper" explosives similar to shuttle? For range safety, one would hope so. Once SLS is put out of its misery, is it safe to bet that we won't see SRBs used for manned flight anymore, or would NASA still be open to the idea? Note that Atlas V will use solids on the crewed configuration used for Starliner launches. They're much smaller solids, but they are still there. Again, the 2nd stage isn't designed to handle the loads of being in the atmosphere without *something* on top of it to handle the aerodynamic forces. It will likely shred. I hadn't realised there was a 2nd stage. Thansk for clarification. I though it was Dragon, its service module and Falcon 9 first stage. Test as you fly; fly as you test. Not having an upper stage on this flight would violate that principle. The mass and aerodynamics of the launch vehicle would be all wrong and would have to be compensated for. Because of this, it's just easier to stick a real upper stage on the stack and fully fuel it, just like a real commercial crew launch. From the animatiosn I have seen, Dragon ejects with its service module still attached (apparently for aerodynamic purposes), and only at apogee does it detach, capsule uses thrusters to set descent attitude , deploys parachutes Yes. The fins on the trunk aren't there to look pretty. They keep the capsule stable during the abort, up to max altitude (essentially zero velocity). If there is a second stage, would this be a dummy one just for mass equivalence, or would they have a real McCoy that is destroyed without having done anything ? It's a real, fully fueled, Falcon 9 upper stage. Only the Vacuum Merlin is a "dummy" mass simulator on this abort test since the upper stage won't need to be fired on this flight. Again, test as you fly; fly as you test. Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
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SpaceX Dragon 2 In Flight Abort Test
On 2020-01-18 17:17, Jeff Findley wrote:
In article , says... ... Out of curiosity, how do they measure how much thrust is produced by each engine? A sensor that measures pressure against the wall of the engine bell? An electronic scale measuring "weight" of engine against the mounting brackets of the stage? Or is thrust assumed from speed of turbopumps (fuel flow)? You'd have to ask SpaceX. Indeed, but I would (naively, perhaps) assume that the pressure inside the combustion chamber can be directly (mathematically) translated into thrust, as long as the shape of the throat and bell remain as designed. The thrust is determined by the exhaust flow, which is determined by the chamber pressure (and the ambient pressure) Perhaps there are some subtle thermodynamic effects in the compression-expansion process that depend also on the temperature and molecular composition of the gases, and on possible last-chance combustion after the chamber, but I would assume that those are secondary to the effect of chamber pressure. -- Niklas Holsti Tidorum Ltd niklas holsti tidorum fi . @ . |
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SpaceX Dragon 2 In Flight Abort Test
On 2020-01-19 0:11, JF Mezei wrote:
On 2020-01-18 10:17, Jeff Findley wrote: NASA knows the details of this for sure. But I believe that the Super Draco engines are sized to pull Dragon 2 away from Falcon 9 at the same time the engines are shutting down. Media articles tend to "Readers Digest" what is given to them by authorities which are already a Reders Digest version of reality. Say an abort happens for causes other then engines. If engines are already giving astronauts a 3G acceleration, and you fire the Super Dracos that give 4G, the crew would go from 3G to 7G No. If the Dragon is still attached to the launcher when the Dracos fire, the acceleration would only increase a little, as the Draco thrust is added to the Merlin thrust to accelerate the launcher+Dragon assembly. If the Dragon is not attached to the launcher when the Dracos fire, the Dragon will simply pull ahead of the launcher, at 4G, losing contact with the launcher which will fall behind, the distance increasing at 1G. In theory, the launcher's acceleration might increase a little when the Dragon pulls away, because the launcher no longer has to accelerate the Dragon's mass, but I believe that the control SW keeps the launcher's acceleration at its programmed value, and the Dragon's mass is anyway only a fraction of the mass of the launcher and its fuel. Also, I believe that typically Falcon-9 will accelerate at much less than 3G around Max-Q. In an earlier discussion, numbers in the range 0.5G - 1G (on top of gravity) were used, taken from some time-velocity diagrams of actual launches. -- Niklas Holsti Tidorum Ltd niklas holsti tidorum fi . @ . |
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SpaceX Dragon 2 In Flight Abort Test
On Jan/18/2020 at 17:53, Niklas Holsti wrote :
On 2020-01-19 0:11, JF Mezei wrote: On 2020-01-18 10:17, Jeff Findley wrote: NASA knows the details of this for sure.Â* But I believe that the Super Draco engines are sized to pull Dragon 2 away from Falcon 9 at the same time the engines are shutting down. Media articles tend to "Readers Digest" what is given to them by authorities which are already a Reders Digest version of reality. Say an abort happens for causes other then engines. If engines are already giving astronauts a 3G acceleration, and you fire the Super Dracos that give 4G, the crew would go from 3G to 7G No. If the Dragon is still attached to the launcher when the Dracos fire, the acceleration would only increase a little, as the Draco thrust is added to the Merlin thrust to accelerate the launcher+Dragon assembly. If the Dragon is not attached to the launcher when the Dracos fire, the Dragon will simply pull ahead of the launcher, at 4G, losing contact with the launcher which will fall behind, the distance increasing at 1G. In theory, the launcher's acceleration might increase a little when the Dragon pulls away, because the launcher no longer has to accelerate the Dragon's mass, but I believe that the control SW keeps the launcher's acceleration at its programmed value, and the Dragon's mass is anyway only a fraction of the mass of the launcher and its fuel. Yes. Note also that even if the Dragon capsule did experience 7g for a few seconds, that wouldn't be a problem. Such an acceleration is a problem if it is sustained but for a few seconds 7g is uncomfortable but not really dangerous. Alain Fournier |
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SpaceX Dragon 2 In Flight Abort Test
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SpaceX Dragon 2 In Flight Abort Test
The launch abort test was just completed. I watched it live on the
SpaceX live stream. Everything appeared to have happened as predicted. Thrust termination on Falcon 9 and Dragon 2 separation happened very close to each other (I couldn't see any delay). Everything went very smoothly. Four good main parachutes fully deployed before splashdown. The SpaceX engineer who was one of the commentators for the live stream said this is the Mark 3 design for the parachutes. They looked really good. There was an awesome live camera view from the parachute compartment on Dragon 2 looking up at the parachutes. You could see all of the deployment steps (they don't just open all the way right away). Congrats to SpaceX and NASA. Here's hoping that the reviews being conducted by NASA go smoothly so that we can see a crewed demo flight to ISS within the upcoming months. Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
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