|
|
Thread Tools | Display Modes |
#61
|
|||
|
|||
"Flight proven" is the new "Certified Pre-Owned"
JF Mezei wrote:
On 2016-09-06 22:58, Fred J. McCall wrote: The performance penalty would be HUGE. Remember, it is the velocity vector parallel to the surface of the Earth that you care about. 'Bending' that velocity vector after it has some appreciable size (which is what you're suggesting) is stupidly expensive with regards to fuel. Yet, they do that for every geostationary launch. (albeit, much of the correction is done at higher altitudes than at launch). You should also note that this is done by adding something like a PAM to the payload. You should also note that they lose something like 60% of their payload capability getting to GTO. Still though, would be interesting to know if technically possible to launch from Vandenburg and adjust orbital inclination as early as possible (and when that time would happen from "allowed to fly over Mexico".) If you're willing to give up over 60% of your payload capability you can do 25 degree orbital plane changes. To do a larger change you're going to have to give up more payload. You also need to note that launching down the coast is how they get to POLAR orbits. To do what you're talking about would require flying across all of Mexico from northwest to southeast. And there is NO safe corridor along that path because you won't make orbit until you've already crossed most of Mexico. See the following: http://www.planetary.org/blogs/guest...avis/3450.html You can't do what you suggest unless you're willing to drop rockets on people if something goes wrong. (consider case where station is in dire need of something, and SpaceX has a rocket/dragon ready but no east coast launch pad ready). Launch a Progress from Baikonur Cosmodrome. Only way to do it at that point. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#62
|
|||
|
|||
"Flight proven" is the new "Certified Pre-Owned"
"Fred J. McCall" wrote in message
... JF Mezei wrote: On 2016-09-06 22:58, Fred J. McCall wrote: The performance penalty would be HUGE. Remember, it is the velocity vector parallel to the surface of the Earth that you care about. 'Bending' that velocity vector after it has some appreciable size (which is what you're suggesting) is stupidly expensive with regards to fuel. Yet, they do that for every geostationary launch. (albeit, much of the correction is done at higher altitudes than at launch). You should also note that this is done by adding something like a PAM to the payload. You should also note that they lose something like 60% of their payload capability getting to GTO. Still though, would be interesting to know if technically possible to launch from Vandenburg and adjust orbital inclination as early as possible (and when that time would happen from "allowed to fly over Mexico".) If you're willing to give up over 60% of your payload capability you can do 25 degree orbital plane changes. To do a larger change you're going to have to give up more payload. You also need to note that launching down the coast is how they get to POLAR orbits. To do what you're talking about would require flying across all of Mexico from northwest to southeast. And there is NO safe corridor along that path because you won't make orbit until you've already crossed most of Mexico. See the following: http://www.planetary.org/blogs/guest...avis/3450.html You can't do what you suggest unless you're willing to drop rockets on people if something goes wrong. (consider case where station is in dire need of something, and SpaceX has a rocket/dragon ready but no east coast launch pad ready). Launch a Progress from Baikonur Cosmodrome. Only way to do it at that point. Or launch a Cygnus from MARS. One thing that NASA has done right with the ISS is ensured that they're not reliant on just ONE method of resupply. -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net |
#63
|
|||
|
|||
"Flight proven" is the new "Certified Pre-Owned"
On Monday, September 5, 2016 at 9:13:46 PM UTC+12, Fred J. McCall wrote:
William Mook wrote: On Saturday, September 3, 2016 at 7:44:26 AM UTC+12, Fred J. McCall wrote: William Mook wrote: On Friday, September 2, 2016 at 2:19:19 AM UTC+12, Fred J. McCall wrote: Rick Jones wrote: Jeff Findley wrote: The "violence" of a launch is largely a myth for liquid fueled launch vehicles. Myth or "history"? eg pogo/whatnot. Pogo means the rocket has a problem. It's not a 'normal' liquid rocket effect. The vibe environment from a solid is much, MUCH worse than from a liquid. Pogo oscillation is a self-excited vibration in liquid propellant rocket engines caused by combustion instability. The unstable combustion results in variations of engine thrust, causing variations of acceleration on the vehicle's flexible structure, which in turn cause variations in propellant pressure and flow rate, closing the self-excitation cycle. The name is a metaphor comparing the longitudinal vibration to the bouncing of a pogo stick. Pogo oscillation places stress on the frame of the vehicle which, in severe cases can be potentially dangerous. We all know what it is, Mookie. We don't need you plagiarizing Wiki so you can try to sound like you know what you're talking about. How I sound to others is of overweening importance to you emotionally isn't it? lol. What I reproduced here is accurate appropriate and informative. That is what you're saying, even though you constitutionally cannot bring yourself to say it in a way that isn't denigrating to me personally. Which says far more about you than it does about me. No. The fact that you plagiarize sources fairly disgusting. The nature of the pintle fed engine is such that Pogo oscillation does not occur. Nobody anywhere promises that but you. Promise? That's an interestingly inappropriate word choice. Facts are not promises. You obviously have not read and understood the pintle engine patents Grumman sued SpaceX over did you? I urge anyone to go and look at those, or this one; You've made a statement you cannot support. No, you've made a mistake and are blaming others instead of correcting your mistake. https://www.google.ch/patents/US7827781 Note the use of the word "reduce" and not the word "eliminate". Context friend. Context. The patent says in part, "improve rocket engine combustion stability and reduce harmonic disturbance within the engine chamber" So, what is being reduced? Harmoinc disturbance. Now, WHY is that important? to quote the patent yet again, "The longitudinal resonance is often multiplied by the effect of the variable backpressure created at the injector, and thus causes a varying flow rate through the injector. This leads to varying thrust from the engine known as the “pogo” effect." which finally concludes with the word, "phased damping methods to eliminate multiple orders of combustion instability." Got it? So go **** yourself you blowhard knowitall. snip MookMuck -- "You take the lies out of him, and he'll shrink to the size of your hat; you take the malice out of him, and he'll disappear." -- Mark Twain |
#64
|
|||
|
|||
"Flight proven" is the new "Certified Pre-Owned"
"William Mook" wrote in message
... On Monday, September 5, 2016 at 9:13:46 PM UTC+12, Fred J. McCall wrote: Note the use of the word "reduce" and not the word "eliminate". Context friend. Context. The patent says in part, "improve rocket engine combustion stability and reduce harmonic disturbance within the engine chamber" So, what is being reduced? Harmoinc disturbance. Now, WHY is that important? to quote the patent yet again, "The longitudinal resonance is often multiplied by the effect of the variable backpressure created at the injector, and thus causes a varying flow rate through the injector. This leads to varying thrust from the engine known as the “pogo” effect." which finally concludes with the word, "phased damping methods to eliminate multiple orders of combustion instability." Got it? So go **** yourself you blowhard knowitall. You know, it amazes me a times when someone goes out of their way to prove their opponent's point. -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net |
#65
|
|||
|
|||
"Flight proven" is the new "Certified Pre-Owned"
Fred is blissfully unaware of the importance of specific impulse.
The PAM (Payload Assist Module) on the Delta II uses a Star 48 solid motor with a 286 second specific impulse. 2.8 km/sec exhaust speed. A TR-201 engine using hypergolics has a 3.8 km/sec exhaust speed. A LOX/RP-1 engine has a 2.7 km/sec exhaust speed. Boeing offers a Xenon Electrostatic ion thruster System (XIPS) option for the 702 satellite system with a 34.3 km/sec exhaust speed. The XIPS equipped 702 satellite is equipped with four 25 cm (9.8 in) thrusters. An XIPS-equipped satellite can stay on station longer with a given fuel supply and be used for final orbit insertion as well conserving payload mass, as compared to using a traditional on-board liquid apogee engine. Now, once we're in LEO we can use the Vis Viva equation to calculate the delta vee required to go from LEO to GEO. We can also use that delta vee with the specific performance figures above, to determine percentage of total stage weight that must be propellant. We want to go from low earth orbit (LEO) to Geosynchronous Equatorial Orbit (GEO). So, we go from a radius of Earth's surface plus some nominal altitude, say 300 km, to 35,786 km altitude above the equator. Which is a radius equal to that distance plus the equatorial radius of the Earth. When the satellite reaches that altitude along the transfer orbit (GTO) you must add more speed at altitude to circularise the orbit at that altitude. Now, we define a kilometer at 10,000 kilometers between the equator and the pole. So, it takes 40,000 km to describe the circumference of the Earth. This is a rough measure, but dividing by 2*pi we obtain 6,366.2 km as the Earth's radius. So, a satellite orbiting 300 km above the earth has an orbital radius of 6,666.2 km. Similarly an orbit that is 35,786 km above the equator is 42,152.2 km from the centre of the Earth - that being the radius at that altitude. GM = 3.986*10^14 cubic meters per second squared. v^2 = GM(2/r - 1/a) A circular orbit a = r so; v^2 = GM/a So, a circular orbit at 300 km altitude is; v^2 = GM/6,666,200 = 6.249 * 10^7 m^2/s^2 -- 7.905 km/sec A circular orbit at 42,152.2 km is; v^2 = GM/42,152,200 = 3.075 km/sec. Now an elliptical orbit with a perigee at 300 km and an apogee at 35,786 km has a semi-major axis length of; a = (6,666,200 + 42,152,200) / 2 = 25,909,200 So, the speed of an object in this orbit, at 300 km altitude is; v = (GM * (2/r - 1/a))^.5 = (3.986*10^14 * (2/6,666,200 - 1/25,909,200))^.5= 10.197 km/sec and, the speed of an object in this orbit, at 35,786 km altitude is; v = (GM * (2/r - 1/a))^.5 = (3.986*10^14 * (2/42,152,200 - 1/25,909,200))^.5 = 1.878 km/sec. So, to speed up from 7.905 km/sec to 10.197 km/sec at 300 km altitude requires a change in speed of 2.292 km/sec. To speed up again from 1.878 km/sec to 3.075 km/sec at 35,786 km altitude requires 1.197 km/sec. So, any stage we put on the vehicle, requires that it boost the stage through a total change in speed of 1.197 + 2.292 = 3.489 km/sec. Now, in this example we're ignoring plane changes, which is best achieved at altitude, but this calculation gives us the idea of what's needed. So, we have a delta vee requirement of 3.5 km/sec. Now its time to use the Tsiolkovsky equation; Vf = Ve* LN(1/(1-u)) rearranging u = 1 - 1 / EXP( Vf/ Ve ) Now, recall Ve for each type of rocket; XIPS - 34.3 km/sec Hypergolic - 3.7 km/sec PAM - solid - 2.8 km/sec LOX/RP1 - 2.7 km/sec And Vf = 3.5 km/sec. So, we can calculate the following propellant fractions; XIPS - 34.3 km/sec ------- 9.7% Hypergolic - 3.7 km/sec--- 61.1% PAM - solid - 2.8 km/sec-- 71.3% LOX/RP1 - 2.7 km/sec ---- 72.6% So, the 60% quoted in the previous post is low but in the right range - for legacy hardware. MODERN hardware on the other hand, has a minor cost - less than 10% of the payload is dedicated to propellant to raise the orbit and keep the payload on that orbit. On Thursday, September 8, 2016 at 4:28:55 AM UTC+12, Fred J. McCall wrote: JF Mezei wrote: On 2016-09-06 22:58, Fred J. McCall wrote: The performance penalty would be HUGE. Remember, it is the velocity vector parallel to the surface of the Earth that you care about. 'Bending' that velocity vector after it has some appreciable size (which is what you're suggesting) is stupidly expensive with regards to fuel. Yet, they do that for every geostationary launch. (albeit, much of the correction is done at higher altitudes than at launch). You should also note that this is done by adding something like a PAM to the payload. You should also note that they lose something like 60% of their payload capability getting to GTO. Still though, would be interesting to know if technically possible to launch from Vandenburg and adjust orbital inclination as early as possible (and when that time would happen from "allowed to fly over Mexico".) If you're willing to give up over 60% of your payload capability you can do 25 degree orbital plane changes. To do a larger change you're going to have to give up more payload. You also need to note that launching down the coast is how they get to POLAR orbits. To do what you're talking about would require flying across all of Mexico from northwest to southeast. And there is NO safe corridor along that path because you won't make orbit until you've already crossed most of Mexico. See the following: http://www.planetary.org/blogs/guest...avis/3450.html You can't do what you suggest unless you're willing to drop rockets on people if something goes wrong. (consider case where station is in dire need of something, and SpaceX has a rocket/dragon ready but no east coast launch pad ready). Launch a Progress from Baikonur Cosmodrome. Only way to do it at that point. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#66
|
|||
|
|||
"Flight proven" is the new "Certified Pre-Owned"
William Mook wrote:
On Monday, September 5, 2016 at 9:13:46 PM UTC+12, Fred J. McCall wrote: William Mook wrote: On Saturday, September 3, 2016 at 7:44:26 AM UTC+12, Fred J. McCall wrote: William Mook wrote: On Friday, September 2, 2016 at 2:19:19 AM UTC+12, Fred J. McCall wrote: Rick Jones wrote: Jeff Findley wrote: The "violence" of a launch is largely a myth for liquid fueled launch vehicles. Myth or "history"? eg pogo/whatnot. Pogo means the rocket has a problem. It's not a 'normal' liquid rocket effect. The vibe environment from a solid is much, MUCH worse than from a liquid. Pogo oscillation is a self-excited vibration in liquid propellant rocket engines caused by combustion instability. The unstable combustion results in variations of engine thrust, causing variations of acceleration on the vehicle's flexible structure, which in turn cause variations in propellant pressure and flow rate, closing the self-excitation cycle. The name is a metaphor comparing the longitudinal vibration to the bouncing of a pogo stick. Pogo oscillation places stress on the frame of the vehicle which, in severe cases can be potentially dangerous. We all know what it is, Mookie. We don't need you plagiarizing Wiki so you can try to sound like you know what you're talking about. How I sound to others is of overweening importance to you emotionally isn't it? lol. What I reproduced here is accurate appropriate and informative. That is what you're saying, even though you constitutionally cannot bring yourself to say it in a way that isn't denigrating to me personally. Which says far more about you than it does about me. No. The fact that you plagiarize sources fairly disgusting. The nature of the pintle fed engine is such that Pogo oscillation does not occur. Nobody anywhere promises that but you. Promise? That's an interestingly inappropriate word choice. Facts are not promises. You obviously have not read and understood the pintle engine patents Grumman sued SpaceX over did you? I urge anyone to go and look at those, or this one; You've made a statement you cannot support. No, you've made a mistake and are blaming others instead of correcting your mistake. ? Well, no, I haven't made a mistake and you're an ignorant fool. https://www.google.ch/patents/US7827781 Note the use of the word "reduce" and not the word "eliminate". Context friend. Context. The patent says in part, "improve rocket engine combustion stability and reduce harmonic disturbance within the engine chamber" Note "improve" and "reduce", not "perfect" and "eliminate". snip Mookie Maundering So go **** yourself you blowhard knowitall. Kiss my rosy red arse, you ignorant bloviating ****. Your problem is that it must seem, from the hole of your ignorance, that I DO know it all. But that's just when compared to an ignorant ****e like you. -- "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 |
#67
|
|||
|
|||
"Flight proven" is the new "Certified Pre-Owned"
William Mook wrote:
Fred is blissfully unaware of the importance of specific impulse. Mookie is blissfully unaware of, well, pretty much everything. snip Mook****e -- "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 |
#68
|
|||
|
|||
"Flight proven" is the new "Certified Pre-Owned"
In sci.space.policy message PNKdncn3GZP5_lLKnZ2dnUU7-QXNnZ2d@earthlink.
com, Tue, 6 Sep 2016 20:46:28, "Greg (Strider) Moore" mooregr@deleteth isgreenms.com posted: "JF Mezei" wrote in message news:57cf445c$0$15716$c3e8da3$9deca2c3@new s.astraweb.com... I can understand that they don't want rockets flying over populated areas in case they blow up. However, at what altitude does this restriction end ? Basically... at the point if your payload and rocket becomes purely ballistic it won't crash on someone. That cannot always have been the case - I recall seeing a Shuttle and its Tank passing independently over North London. Premature MECO could have resulted in the Tank landing there, and the Shuttle ending up at Heathrow. -- (c) John Stockton, Surrey, UK. Turnpike v6.05 MIME. Merlyn Web Site - FAQish topics, acronyms, & links. |
#69
|
|||
|
|||
"Flight proven" is the new "Certified Pre-Owned"
Dr J R Stockton wrote:
In sci.space.policy message PNKdncn3GZP5_lLKnZ2dnUU7-QXNnZ2d@earthlink. com, Tue, 6 Sep 2016 20:46:28, "Greg (Strider) Moore" mooregr@deleteth isgreenms.com posted: "JF Mezei" wrote in message news:57cf445c$0$15716$c3e8da3$9deca2c3@new s.astraweb.com... I can understand that they don't want rockets flying over populated areas in case they blow up. However, at what altitude does this restriction end ? Basically... at the point if your payload and rocket becomes purely ballistic it won't crash on someone. That cannot always have been the case - I recall seeing a Shuttle and its Tank passing independently over North London. Premature MECO could have resulted in the Tank landing there, and the Shuttle ending up at Heathrow. No, I don't think it could. The external tank is a big, low density, draggy thing. I think they came to the conclusion that it would break up and burn regardless, which is probably why the FTS was removed from the tank on later flights. -- "Insisting on perfect safety is for people who don't have the balls to live in the real world." -- Mary Shafer, NASA Dryden |
#70
|
|||
|
|||
"Flight proven" is the new "Certified Pre-Owned"
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
might Odissey-Moon be the Google's expected, preferred, designed,"chosen" and (maybe) "funded" GLXP team to WIN the prize? with ALL otherteams that just play the "sparring partners" role? | gaetanomarano | Policy | 3 | September 27th 08 06:47 PM |
just THREE YEARS AFTER my "CREWLESS Space Shuttle" article, theNSF """experts""" discover the idea of an unmanned Shuttle to fill the2010-2016 cargo-to-ISS (six+ years) GAP | gaetanomarano | Policy | 3 | September 15th 08 04:47 PM |
and now, Ladies and Gentlemen, the NSF "slow motion experts" have(finally) "invented" MY "Multipurpose Orbital Rescue Vehicle"... just 20 | gaetanomarano | Policy | 9 | August 30th 08 12:05 AM |