sevenperforce Posted January 24, 2018 Share Posted January 24, 2018 KABLOOIE!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
Brotoro Posted January 24, 2018 Share Posted January 24, 2018 Kablooie? Please...no kablooie. Quote Link to comment Share on other sites More sharing options...
tater Posted January 25, 2018 Share Posted January 25, 2018 Quote Link to comment Share on other sites More sharing options...
HebaruSan Posted January 25, 2018 Share Posted January 25, 2018 "SpaceX Discussion Thread" Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted January 25, 2018 Share Posted January 25, 2018 (edited) 5 minutes ago, HebaruSan said: "SpaceX Discussion Thread" SQUERL! Edited January 25, 2018 by CatastrophicFailure Well in all fairness, space nerds are usually dinosaur nerds too... Quote Link to comment Share on other sites More sharing options...
Streetwind Posted January 25, 2018 Share Posted January 25, 2018 ^--- best description of the SpaceX thread's attention span I've ever seen Here's a video discussing the way SpaceX does static fire tests in general, for those curious: Quote Link to comment Share on other sites More sharing options...
YNM Posted January 25, 2018 Share Posted January 25, 2018 Yay ! Now to see 28 (primary) rocket engines in flight... Quote Link to comment Share on other sites More sharing options...
Green Baron Posted January 25, 2018 Share Posted January 25, 2018 If you guys are interested in discussing large lizard's lifestyle further: Falcon Heavy: looked nice and impressive. Quote Link to comment Share on other sites More sharing options...
softweir Posted January 25, 2018 Share Posted January 25, 2018 Temporarily locked while off-topic posts get moved elsewhere. OK guys, unlocked. T.rex posts moved to above-linked thread PLEASE keep it on-topic - that was too much work to go to! Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 25, 2018 Share Posted January 25, 2018 (edited) That 27-engine ignition sure looked simultaneous from where I was standing. Of course, I wasn't standing very close. Mostly because it would have killed me. Question: this is still not as much thrust as the Saturn V or the STS, but it stayed on the pad for longer (ten seconds after ignition, both the STS and the Saturn V were 0.2-0.3 km above the pad). For an extended hold-down fire, what kind of acoustic power flux are we looking at? More than the S-V or STS? Off topic... Spoiler 6 hours ago, tater said: <snip> 29 minutes ago, softweir said: Temporarily locked while off-topic posts get moved elsewhere. OK guys, unlocked. T.rex posts moved to above-linked thread PLEASE keep it on-topic - that was too much work to go to! Oops, I was typing this while you were doing the lock-unlock. Will edit and move. Edited January 25, 2018 by sevenperforce Quote Link to comment Share on other sites More sharing options...
RCgothic Posted January 25, 2018 Share Posted January 25, 2018 It takes about 6-10 seconds for a Saturn V to clear the tower, so it's probably reasonable to say that a 12 second Falcon Heavy hold down burn is probably comparable in terms of energy delivered to the flame trench. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 25, 2018 Share Posted January 25, 2018 33 minutes ago, RCgothic said: It takes about 6-10 seconds for a Saturn V to clear the tower, so it's probably reasonable to say that a 12 second Falcon Heavy hold down burn is probably comparable in terms of energy delivered to the flame trench. Let's see, the Saturn V had liftoff thrust of 35.1 MN at a SL isp of 263 seconds, so that comes to something like 13.6 tonnes of propellant per second. Doing the math.... The Saturn V rose 147.8 meters (three football fields) in the first ten seconds. Cleared its own height in 8.5 seconds. Quote Link to comment Share on other sites More sharing options...
Thor Wotansen Posted January 25, 2018 Share Posted January 25, 2018 Actually that depends on TWR. I don't know the TWR numbers for both but I'm sure someone does. I would suspect the Falcon Heavy to have higher TWR than the Saturn V though. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 25, 2018 Share Posted January 25, 2018 9 minutes ago, Thor Wotansen said: Actually that depends on TWR. I don't know the TWR numbers for both but I'm sure someone does. I would suspect the Falcon Heavy to have higher TWR than the Saturn V though. I calculated TWR at one-second intervals and determined displacement iteratively based on kinematic equations. 147.8 meters in ten seconds. Quote Link to comment Share on other sites More sharing options...
RCgothic Posted January 25, 2018 Share Posted January 25, 2018 48 minutes ago, sevenperforce said: Let's see, the Saturn V had liftoff thrust of 35.1 MN at a SL isp of 263 seconds, so that comes to something like 13.6 tonnes of propellant per second. Doing the math.... The Saturn V rose 147.8 meters (three football fields) in the first ten seconds. Cleared its own height in 8.5 seconds. Falcon Heavy is something like 8.2 tonnes per second. Assuming Saturn V dumps negligible propellant into the flame trench after it clears the tower (exhaust slowed by distance, "aim" of exhaust wanders) then with a linear reduction it would need to take longer than 14.5s to exceed the Falcon Heavy's static fire. It doesn't take that long, so Falcon Heavy probably wins. But it's moving slowly to begin with. Assuming again zero as Saturn clears the tower and, 10s to clear the tower, and reduction proportional to distance ascended.... I'll do the maths later if nobody else beats me to it. I think it's close. Quote Link to comment Share on other sites More sharing options...
PB666 Posted January 25, 2018 Share Posted January 25, 2018 (edited) 2 hours ago, Thor Wotansen said: Actually that depends on TWR. I don't know the TWR numbers for both but I'm sure someone does. I would suspect the Falcon Heavy to have higher TWR than the Saturn V though. I plotted these, F9 comes off the launch pad at 1.25 m/s or so, there is a bit of a bounch after they release the clamps but it settles down and then runs up to about 1.25 within a couple of seconds. So that when the engines reach a thrust required to lift that launch clamps come up it rises at minimal lift for about 3 seconds and then goes to full throttle. As a general statement about what it is and what it does. Consider that if you launch with a TWR at 2, you could rise up to M0.8 but then you would end up throttling down to 0.6 power until past Max Q and then back up to 80% power at some later point. There is a logic in doing that, but if there is lag between thrust requirement and actual application it might not be a good choice. Clarification: They could use full thrust on FH liftoff but I doubt they will, they probably will lift of similarly, sparing the forces on the launch clamps and boost power a few meters over the pad. I have to repeat this, they don not know how bad Q-side forces will be, So I don't believe they will hit at full velocity quickly and instead use a more constant acceleration to max Q, sparing power on the core in order to avoid placing to much stress on the boosters. And if I was in there shoes I would have a ton of sensors on the nosecones of the boosters to measure those forces. I know that most of you know this but just a little reminder, the slower the climb, the more wasteful in fuel, but the higher the altitude in which you encounter max Q and the lower the pressure is at max Q. Edited January 25, 2018 by PB666 Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted January 25, 2018 Share Posted January 25, 2018 40 minutes ago, PB666 said: They could use full thrust on FH liftoff but I doubt they will, they probably will lift of similarly, sparing the forces on the launch clamps and boost power a few meters over the pad. I can’t find the source ATM (since I’m mostly half asleep still), but I recall seeing they won’t run the engines at more than 92% for this flight. Also keep in mind the payload, lacking some still undisclosed mass simulator, this Falcon Heavy will be flying pretty, um, light... Quote Link to comment Share on other sites More sharing options...
Just Jim Posted January 25, 2018 Share Posted January 25, 2018 I've been watching the test-fire video, and big as that is, I'm hoping we'll be able to see it from here, even if it's a day launch!!! Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 25, 2018 Share Posted January 25, 2018 17 minutes ago, CatastrophicFailure said: I can’t find the source ATM (since I’m mostly half asleep still), but I recall seeing they won’t run the engines at more than 92% for this flight. Also keep in mind the payload, lacking some still undisclosed mass simulator, this Falcon Heavy will be flying pretty, um, light... As I showed earlier, the difference between a completely empty Falcon Heavy and a Falcon Heavy flying with maximum expendable LEO payload is something like 3-4% difference in TWR. So there's not really going to be any detectable difference here. Quote Link to comment Share on other sites More sharing options...
tater Posted January 25, 2018 Share Posted January 25, 2018 32 minutes ago, Just Jim said: I've been watching the test-fire video, and big as that is, I'm hoping we'll be able to see it from here, even if it's a day launch!!! If I lived any closer to the Cape than TX, I'd drive there to watch it. How far is it for you, a couple hours? Quote Link to comment Share on other sites More sharing options...
Just Jim Posted January 25, 2018 Share Posted January 25, 2018 9 minutes ago, tater said: If I lived any closer to the Cape than TX, I'd drive there to watch it. How far is it for you, a couple hours? Between 3 and 4 hours, depending on traffic. The fastest way is blazing straight through Orlando on I-4... which can be fast and insane and 90 mph all the way through, and I can make great time. But one good wreck can bring it all to a screeching halt just as fast.... and 6 lanes of bumper to bumper is not something you want to experience... The even bigger problem with driving over for launches is getting all the way over there, only to have it scrubbed at the last second and pushed back a day or three. Truth is, the only time I was really close for a shuttle launch I was visiting my brother in Daytona, which is just up the coast, and we didn't know there was one until the last minute, when the local news switched over, and we had just enough time to get out back before lift off.... It was unbelievable, like the whole sky had caught fire, and I'm still ecstatic I got to see just one. But like I said, it was totally unplanned, and I just got super lucky. Quote Link to comment Share on other sites More sharing options...
tater Posted January 25, 2018 Share Posted January 25, 2018 I'd try and make some luck for FH, honestly. Hard from Albuquerque, though, even though there is actually a direct flight to Orlando, at short notice it's too expensive, and ABQ to anywhere is already kind of expensive. Quote Link to comment Share on other sites More sharing options...
tater Posted January 25, 2018 Share Posted January 25, 2018 They have to expend it because there will not be time for OCISLY to make it back to port, then out again for the FH core. besides, it's an old core anyway I think. Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted January 25, 2018 Share Posted January 25, 2018 Or maybe just a second one. Or possibly a third, if they have any plans to ever to barge recovery on the side boosters... Quote Link to comment Share on other sites More sharing options...
tater Posted January 25, 2018 Share Posted January 25, 2018 Quote Link to comment Share on other sites More sharing options...
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