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#31
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Falcon 1 Staging Recontact - Engine Burp
Jeff Findley wrote:
"richard schumacher" wrote in message ... A potential problem with single-impulse separation methods such as springs arises if the first stage continues to generate thrust, because it can then catch up with the second stage. This is exactly what happened with the 3rd Falcon 1 flight. On another discussion forum, Henry Spencer said this is almost exactly what nearly happened during Apollo 15's S-IC separation, so naturally I went digging for details. http://history.nasa.gov/alsj/a15/a15mrp6.pdf Quote from above: Four of the eight S-IC retromotors and all of the S-II stage ullage motors were removed for this flight; therefore, the S-IC/S-II separation sequence was revised. This sequence change extended the coast period between S-IC outboard engine cutoff and S-II engine start command by one second. The S-IC/S-II separation sequence and S-II engine thrust buildup performance was satisfactory. From what I understand, the above deleted motors were added back for subsequent flights, but I can't find a PDF online to confirm this. Apollo 16 press kit: http://history.nasa.gov/alsj/a16/A16_PressKit.pdf p. 140 (144 of the PDF): Significant Vehicle Changes Saturn vehicle SA-511 is similar in configuration to the Apollo 15 launch vehicle. The first stage (S-1C) has eight retrorocket motors, double the number on the SA-510 vehicle, because flight evaluation of the Apollo 15 mission revealed that the separation distance between the first and second stages was less than predicted. Eight retrorockets will give a greater safety margin should one motor fail during separation. Apollo 17 press kit: http://history.nasa.gov/alsj/a17/A17_PressKit.pdf p. 94 (146 of the PDF): The first stage has eight solid-fuel retro-rockets that fire to separate the first and second stages. Each rocket produces a thrust of 337,000 newtons (75,800 pounds) for 0.54 seconds. |
#32
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Falcon 1 Staging Recontact - Engine Burp
richard schumacher wrote:
Barring some assembly error the odds of success for the 4th Falcon 1 flight should be pretty good. That's what everyone said after the first. And the second too. D. -- Touch-twice life. Eat. Drink. Laugh. http://derekl1963.livejournal.com/ -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
#33
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Falcon 1 Staging Recontact - Engine Burp
Pat Flannery wrote:
Jeff Findley wrote: On another list Henry Spencer pointed out that, when they developed the Saturns, Von Braun's team was pretty much the only team on the planet who had real experience designing large rockets. No, Korolev had some good sized ones, like the R-7 (built with some German input), and Chelomei was working on the UR-500 "Proton" super ICBM of the Saturn 1 class, a entirely home-grown Soviet design. Henry has always been able to generate a good spin when he wants to, but this is a bit much even for him. Von Braun's team's only real experience was in drawing big rockets, not building them prior to Saturn I. Up till that point the largest thing they had actually built was Jupiter, which wasn't even a ICBM. Their multistage experience consisted of clustered solids atop the Juno 1 and 2 boosters, based on the Redstone and Jupiter respectively. I don't know how much input they had on the V-2/WAC Corporal tests. Ayup. Not to mention the Titan -II and -III that were getting going about the same time as the Saturn program was. If anything, vB and team were held back for years because they belonged to the Army who worked mostly on smaller missiles/launchers. D. -- Touch-twice life. Eat. Drink. Laugh. http://derekl1963.livejournal.com/ -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
#34
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Falcon 1 Staging Recontact - Engine Burp
richard schumacher wrote:
:In article , : Fred J. McCall wrote: : : :Those are methods for cutting the stages apart. Then you need something : :to ensure that they continue moving away from each other: thrusters on : :the first stage to slow it, or firing the second stage just before : :separation. : : : : Or maybe just some strong springs compressed between the stages and : some pop-out drag brakes on the first stage. Not much air up there, : but you're already moving pretty fast so maybe just a little drag is : enough... : :A potential problem with single-impulse separation methods such as :springs arises if the first stage continues to generate thrust, because :it can then catch up with the second stage. This is exactly what :happened with the 3rd Falcon 1 flight. : That's sort of the point of the drag brakes I mentioned... -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#35
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Falcon 1 Staging Recontact - Engine Burp
On Aug 7, 11:59*pm, Fred J. McCall wrote:
That's sort of the point of the drag brakes I mentioned... They wouldn't work due to low air density. Also would add extra weight and unnecessary complexity. The best and easiest solution is to add a delay. Delta-IV is a larger vehicle and it only has springs. No ullage or retro motors, no drag flaps, etc |
#36
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Falcon 1 Staging Recontact - Engine Burp
Jeff Findley wrote: On another discussion forum, Henry Spencer said this is almost exactly what nearly happened during Apollo 15's S-IC separation, so naturally I went digging for details. http://history.nasa.gov/alsj/a15/a15mrp6.pdf Quote from above: Four of the eight S-IC retromotors and all of the S-II stage ullage motors were removed for this flight; therefore, the S-IC/S-II separation sequence was revised. This sequence change extended the coast period between S-IC outboard engine cutoff and S-II engine start command by one second. The S-IC/S-II separation sequence and S-II engine thrust buildup performance was satisfactory. From what I understand, the above deleted motors were added back for subsequent flights, but I can't find a PDF online to confirm this. No, they stayed off on all Apollo J-series flights IIRC (15, 16, 17). Pat |
#37
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Falcon 1 Staging Recontact - Engine Burp
"Pat Flannery" wrote in message telephone... Jeff Findley wrote: On another discussion forum, Henry Spencer said this is almost exactly what nearly happened during Apollo 15's S-IC separation, so naturally I went digging for details. http://history.nasa.gov/alsj/a15/a15mrp6.pdf Quote from above: Four of the eight S-IC retromotors and all of the S-II stage ullage motors were removed for this flight; therefore, the S-IC/S-II separation sequence was revised. This sequence change extended the coast period between S-IC outboard engine cutoff and S-II engine start command by one second. The S-IC/S-II separation sequence and S-II engine thrust buildup performance was satisfactory. From what I understand, the above deleted motors were added back for subsequent flights, but I can't find a PDF online to confirm this. No, they stayed off on all Apollo J-series flights IIRC (15, 16, 17). Actually, the PDF's that Jorge found (see his recent post in this thread) clearly state that they went back to eight retromotors for the S-1C stage on Apollo 16 and Apollo 17 (twice the number on Apollo 15). Perhaps the ullage motors on the S-II stage weren't added back for 16 and 17? Still, it's clear there was a bit of tweaking going on with the Saturn V to eek out a bit more performance on later flights. The other point I wanted to make was that even von Braun's team cut back too far at times, as was the case with the S-1C retromotors. Jeff -- A clever person solves a problem. A wise person avoids it. -- Einstein |
#38
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Falcon 1 Staging Recontact - Engine Burp
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#39
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Falcon 1 Staging Recontact - Engine Burp
Derek Lyons wrote: Ayup. Not to mention the Titan -II and -III that were getting going about the same time as the Saturn program was. If anything, vB and team were held back for years because they belonged to the Army who worked mostly on smaller missiles/launchers. In fact, the Atlas was a lot more sophisticated concept than Jupiter, despite dating from the same time period*. His Army team also never seemed to realize the advantages of solid or hypergolic liquid fuels for military missiles, despite the fact that the Germans were planning to switch to to hypergolics for improved versions of the V-2, as transporting the LOX around was a pain in the rear due to evaporation. Neither Redstone or Jupiter really had the portability of the V-2 either, so in some ways his team was moving backwards in regards to missile technology from what was done in WW II. * Convair did have Krafft Ehricke working for them though, and he had some very advanced ideas in regards to rockets. Pity we didn't build this thing: http://website.lineone.net/~geowood/convair2.jpg http://website.lineone.net/~geowood/convair1.jpg Pat |
#40
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Falcon 1 Staging Recontact - Engine Burp
Fred J. McCall wrote: :A potential problem with single-impulse separation methods such as :springs arises if the first stage continues to generate thrust, because :it can then catch up with the second stage. This is exactly what :happened with the 3rd Falcon 1 flight. : That's sort of the point of the drag brakes I mentioned... At that staging altitude they are going to have to be fairly large to have much effect. Pat |
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