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Saturn V fins?
Acknowledged this is an old debate, but fresh insight may surface,
opinions invited. First let me say I have the highest respect for von Braun and his team, so I think there is a rational reason, but even rocket scientist's ask that question. 1) During the 1st stage boost an F-1 gimbal failure http://en.wikipedia.org/wiki/F-1_(rocket_engine) The fins would maintain enough stability to give time for the escape tower rockets to be a activated. 2) During 2nd stage separation, when the explosive bolts fire, the 1st stage will have a positively predictable orientation. If a bolt malfunctioned or was delayed, once again the escape tower needs a decision if it is to be activated. I think Braun et al thought alot about a manned rated booster from the start, while the previously Atlas and Titan were nuke throwers. Regards Ken S. Tucker |
#2
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Saturn V fins?
On Apr 8, 9:38 am, "Ken S. Tucker" wrote:
Acknowledged this is an old debate, but fresh insight may surface, opinions invited. First let me say I have the highest respect for von Braun and his team, so I think there is a rational reason, but even rocket scientist's ask that question. 1) During the 1st stage boost an F-1 gimbal failurehttp://en.wikipedia.or g/wiki/F-1_(rocket_engine) The fins would maintain enough stability to give time for the escape tower rockets to be a activated. 2) During 2nd stage separation, when the explosive bolts fire, the 1st stage will have a positively predictable orientation. If a bolt malfunctioned or was delayed, once again the escape tower needs a decision if it is to be activated. I think Braun et al thought alot about a manned rated booster from the start, while the previously Atlas and Titan were nuke throwers. Regards Ken S. Tucker Neither are true #1 The fins would have no effect (velocity was too slow) during the time the vehicle was vulnerable (near the LUT) to engine hard over. Additionally, the EDS would activate based on attitude rates regardless if the fins were there or not #2, the staging occurred at too high of an attitude for the small fins to have any effect on the stability of the first stage man rating is not a big deal, mostly smoke and mirrors for the uninformed. After all, Atlas and Titan were "man rated" after the fact |
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Saturn V fins?
On Apr 8, 3:50 pm, (Derek Lyons) wrote:
wrote: This guy "behlin" did not provide any information, about why, that's my posted question. #1 The fins would have no effect (velocity was too slow) during the time the vehicle was vulnerable (near the LUT) to engine hard over. The fins resistance to attitude change is dependent of the rate of attitude change, not vehicle velocity. The fins effect on attitude stability changes with vehicle velocity. Two subtly different things, don't confuse them. Additionally, the EDS would activate based on attitude rates regardless if the fins were there or not Of course the EDS activates on attitude rates regardless of fin presence, because the EDS was designed to activate on attitude rates. man rating is not a big deal, mostly smoke and mirrors for the uninformed. After all, Atlas and Titan were "man rated" after the fact Yeah, the hundreds of thousands of engineering man hours invested in man rating the Atlas and Titan, not to mention the extensive system changes, and also not to mention the increased QA during production... all smoke and mirrors. D. A famous astronaut informed me he did NOT know why the Saturn V had wings, and went on to humorously suggest von Braun liked putting wings on all his rockets. You can see in this diagram, http://en.wikipedia.org/wiki/Jupiter...specifications the Jupiter didn't have fins, but it was monkey rated. The Redstone did and was used successfully in the Mercury program. I read (perhaps rumor), when John Glenn was on top of an Atlas, he recalled 1 out of 4 exploded. Also read the next batch of Saturn V's (never ordered) were to lose the wings because the 1st batch proved to work so well, suggesting they were a safety. Ken |
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Saturn V fins?
On Apr 8, 6:50 pm, (Derek Lyons) wrote:
wrote: #1 The fins would have no effect (velocity was too slow) during the time the vehicle was vulnerable (near the LUT) to engine hard over. The fins resistance to attitude change is dependent of the rate of attitude change, not vehicle velocity. Incorrect. Attitude rate has no bearing on the fins effectiveness, which is dependent on the angle of attack (not the attitude rate) and the velocity. The vehicle could have a large attitude rate, but with a zero angle of attack, the fin is not doing anything additionally your comment has no bearing on my statement. While the vehicle is near the tower, the fins are not effective. |
#6
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Saturn V fins?
"Ken S. Tucker" wrote:
A famous astronaut informed me he did NOT know why the Saturn V had wings, and went on to humorously suggest von Braun liked putting wings on all his rockets. The Saturn V had fins, not wings. But famous or not, that doesn't mean the astronaut was an expert on booster design. You can see in this diagram, http://en.wikipedia.org/wiki/Jupiter...specifications the Jupiter didn't have fins, but it was monkey rated. The Redstone did and was used successfully in the Mercury program. Different design generations - the earlier Redstone was essentially an A4, while the Jupiter builds on the experience gained in the MX-774 tests. Also read the next batch of Saturn V's (never ordered) were to lose the wings because the 1st batch proved to work so well, suggesting they were a safety. The Saturn V future developments shown at the Encyclpedia Astronuatica (http://www.astronautix.com/lvs/saturnv.htm) show the fins as being retained. D. -- Touch-twice life. Eat. Drink. Laugh. http://derekl1963.livejournal.com/ -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
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Saturn V fins?
wrote:
On Apr 8, 6:50 pm, (Derek Lyons) wrote: wrote: #1 The fins would have no effect (velocity was too slow) during the time the vehicle was vulnerable (near the LUT) to engine hard over. The fins resistance to attitude change is dependent of the rate of attitude change, not vehicle velocity. Incorrect. Attitude rate has no bearing on the fins effectiveness, which is dependent on the angle of attack (not the attitude rate) and the velocity. Wrong. Try holding a piece of cardboard vertically while you spin about - and note that despite having zero vertical velocity and zero angle of attack, the cardboard generates drag. As I said, you are confusing two subtly different effects. The vehicle could have a large attitude rate, but with a zero angle of attack, the fin is not doing anything As shown above, this is demonstrably wrong. D. -- Touch-twice life. Eat. Drink. Laugh. http://derekl1963.livejournal.com/ -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL |
#8
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Saturn V fins?
On Apr 9, 7:54 am, (Derek Lyons) wrote:
Wrong. Try holding a piece of cardboard vertically while you spin about - and note that despite having zero vertical velocity and zero angle of attack, the cardboard generates drag. you are wrong on very many levels You are describing a roll. The "drag" you are describing would require either substantial roll rates or large surfaces, neither are present on the Saturn V. Fins on vehicle don't prevent roll by creating drag like a paddle, they do it by creating lift to oppose the motion. Lift is normal to the surface and requires airflow along the surface. Even for an engine hard over which creates a pitch or yaw movement, the correcting force is from the fin due to lift created by an angle of attack and not the fin platform moving thru the air as you describe. This is basic aerodynamics .The fins would have be huge in your case. Due to the slow speed at liftoff, the fins are not able to provide enough correcting force to counter a engine hard over PS. Also you are wrong about the angle of attack, it is not zero, it is 90 degrees in your case |
#9
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Saturn V fins?
On Apr 9, 4:54 am, (Derek Lyons) wrote:
"Ken S. Tucker" wrote: A famous astronaut informed me he did NOT know why the Saturn V had wings, and went on to humorously suggest von Braun liked putting wings on all his rockets. The Saturn V had fins, not wings. But famous or not, that doesn't mean the astronaut was an expert on booster design. You can see in this diagram, http://en.wikipedia.org/wiki/Jupiter...RBM_specificat... the Jupiter didn't have fins, but it was monkey rated. The Redstone did and was used successfully in the Mercury program. Different design generations - the earlier Redstone was essentially an A4, while the Jupiter builds on the experience gained in the MX-774 tests. Also read the next batch of Saturn V's (never ordered) were to lose the wings because the 1st batch proved to work so well, suggesting they were a safety. The Saturn V future developments shown at the Encyclpedia Astronuatica (http://www.astronautix.com/lvs/saturnv.htm) show the fins as being retained. Thanks that's a neat link, though I'm not sure I'd call Von Braun the "Manufacturer" of the Saturn V. See the first sentence here, about the fins, http://en.wikipedia.org/wiki/Saturn_...o_developments (you might know the fella who wrote the article, I'll leave it to you experts to decide if it's ok). D. Touch-twice life. Eat. Drink. Laugh. http://derekl1963.livejournal.com/ -Resolved: To be more temperate in my postings. Oct 5th, 2004 JDL Cheers Ken |
#10
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Saturn V fins?
Hi behlin, I studied your post.
On Apr 8, 2:04 pm, wrote: On Apr 8, 9:38 am, "Ken S. Tucker" wrote: Acknowledged this is an old debate, but fresh insight may surface, opinions invited. First let me say I have the highest respect for von Braun and his team, so I think there is a rational reason, but even rocket scientist's ask that question. 1) During the 1st stage boost an F-1 gimbal failurehttp://en.wikipedia.or g/wiki/F-1_(rocket_engine) The fins would maintain enough stability to give time for the escape tower rockets to be a activated. 2) During 2nd stage separation, when the explosive bolts fire, the 1st stage will have a positively predictable orientation. If a bolt malfunctioned or was delayed, once again the escape tower needs a decision if it is to be activated. I think Braun et al thought alot about a manned rated booster from the start, while the previously Atlas and Titan were nuke throwers. Regards Ken S. Tucker Neither are true Then what is the reason for the fins? #1 The fins would have no effect (velocity was too slow) during the time the vehicle was vulnerable (near the LUT) to engine hard over. Check this post, " Astro/Space Frequently Seen Acronyms" didn't see LUT, but I think I know what you're talking about. Fin effectiveness is proportional to velocity^2, so yes there are a few seconds where they aren't effective, however they rapidly effective. Additionally, the EDS would activate based on attitude rates regardless if the fins were there or not The purpose of the fins is to reduce the attitude excursion rate (in the event of a malfunction thrust vector control), to one that will postpone the disassembly of the rocket, especially where the joints between stages are. #2, the staging occurred at too high of an attitude for the small fins to have any effect on the stability of the first stage Fin effectiveness is ~proportional to density*(velocity)^2. A given Yaw or Pitch excursion also stresses the entire frame in that proportion, so the fins should be designed to be of sufficient area to provide a safe delay prior to disassembly. man rating is not a big deal, mostly smoke and mirrors for the uninformed. After all, Atlas and Titan were "man rated" after the fact I'm certain we've all aware of launches where the Range Officer destructs, do you think the fins buy some time? Ken |
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