Time it takes to get to the Moon
The recent NASA lunar probes took three months to reach the Moon from the Earth. I understand escape velocity to be 7 miles per second, and it took the Apollo astronauts three days to get to the Moon. If the NASA probes used the same escape velocity as the Apollo Moon Missions; why did it take three months for the NASA probes to get there, and only three days for the Apollo spacecraft to get there? ----- Original Message ----- From: utah-astronomy-request@mailman.xmission.com To: utah-astronomy@mailman.xmission.com Sent: Sun, 01 Jan 2012 16:24:51 -0500 (EST) Subject: Utah-Astronomy Digest, Vol 107, Issue 1 Send Utah-Astronomy mailing list submissions to utah-astronomy@mailman.xmission.com To subscribe or unsubscribe via the World Wide Web, visit http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy or, via email, send a message with subject or body 'help' to utah-astronomy-request@mailman.xmission.com You can reach the person managing the list at utah-astronomy-owner@mailman.xmission.com When replying, please edit your Subject line so it is more specific than "Re: Contents of Utah-Astronomy digest..." Today's Topics: 1. Re: club growth (Joe Bauman) 2. Re: Club growth (Brent Watson) 3. Re: Club growth (Joe Bauman) ---------------------------------------------------------------------- Message: 1 Date: Sun, 1 Jan 2012 00:20:24 -0800 (PST) From: Joe Bauman <josephmbauman@yahoo.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Subject: Re: [Utah-astronomy] club growth Message-ID: <1325406024.17605.YahooMailNeo@web38905.mail.mud.yahoo.com> Content-Type: text/plain; charset=us-ascii Thanks for the explanation, Patrick.Now I understand Daniel's comment. Sorry for my response, Daniel -- I thought you were dissing my guru! In fact, we're on the same side here, I'm very happy to say. -- Joe ------------------------------ Message: 2 Date: Sun, 1 Jan 2012 12:04:00 -0800 (PST) From: Brent Watson <brentjwatson@yahoo.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Subject: Re: [Utah-astronomy] Club growth Message-ID: <1325448240.62191.YahooMailNeo@web39402.mail.mud.yahoo.com> Content-Type: text/plain; charset=iso-8859-1 I believe that SLAS, or OAS, is first, a social organization and second, a layman's science organization. ?If people don't return I would postulate it is because they don't find SLAS or OAS socialization to their liking - they don't find a friend. ?If there is friendship, there will be continuing attendance at club meetings and functions. I learned long ago that clubs, organizations, societies, etc. exist to fulfill the basic need of human beings to associate with one another. ?It is written in the preamble to the club's constitution. ?Here it is. ? "We the undersigned, desiring to secure the pleasures and benefits of an association of? persons interested in astronomy; to promote the science of astronomy and its associated? sciences; to encourage and coordinate activities with professional research, do hereby? organize and constitute ourselves as the Salt Lake Astronomical Society, a non-profit? organization." The purpose is first to "...secure the pleasures and benefits of an association of persons...", and then second ?to do the science stuff. ?Anyone who has been an officer of the club will probably acknowledge that it is much harder to get the membership to engage in science than it is to get the members to socialize. ?Outreach, by the way, is a form of socialization. ?Star parties are socialization. ?How many postings do we see here about an observing session - come along. ?They are parties after all. So, my response is the following. ?If you want the club to grow, smile, introduce yourself to the new folks (NOT newbies. ?I believe there are many less offensive monikers.), and take a genuine interest in them. ?Make them your friend. ?Include them in your activities - your private star parties. ?Give them a ride. ?They are people looking for the pleasures and benefits of association who also have an interest in astronomy. ?That commonality will launch club growth. ?People make time for whatever satiates their basic needs. These are rules that are generally true. ?They follow Pareto's rule, i.e., 80 percent of the new folks will want socializing, and 20 percent will want the science. ?So, give them both, but realize where the priority is. $.02 ------------------------------ Message: 3 Date: Sun, 1 Jan 2012 13:24:37 -0800 (PST) From: Joe Bauman <josephmbauman@yahoo.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Subject: Re: [Utah-astronomy] Club growth Message-ID: <1325453077.86952.YahooMailNeo@web38905.mail.mud.yahoo.com> Content-Type: text/plain; charset=iso-8859-1 A wise comment, Brent. And that's why I think a little verbal horseplay is OK sometimes on the UtahAstronomy list. We are not professional astronomers and we don't need to restrict our notes to only scientific matters. -- Thanks, Joe ________________________________ From: Brent Watson <brentjwatson@yahoo.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Sunday, January 1, 2012 1:04 PM Subject: Re: [Utah-astronomy] Club growth I believe that SLAS, or OAS, is first, a social organization and second, a layman's science organization. ?If people don't return I would postulate it is because they don't find SLAS or OAS socialization to their liking - they don't find a friend. ?If there is friendship, there will be continuing attendance at club meetings and functions. I learned long ago that clubs, organizations, societies, etc. exist to fulfill the basic need of human beings to associate with one another. ?It is written in the preamble to the club's constitution. ?Here it is. ? "We the undersigned, desiring to secure the pleasures and benefits of an association of? persons interested in astronomy; to promote the science of astronomy and its associated? sciences; to encourage and coordinate activities with professional research, do hereby? organize and constitute ourselves as the Salt Lake Astronomical Society, a non-profit? organization." The purpose is first to "...secure the pleasures and benefits of an association of persons...", and then second ?to do the science stuff. ?Anyone who has been an officer of the club will probably acknowledge that it is much harder to get the membership to engage in science than it is to get the members to socialize. ?Outreach, by the way, is a form of socialization. ?Star parties are socialization. ?How many postings do we see here about an observing session - come along. ?They are parties after all. So, my response is the following. ?If you want the club to grow, smile, introduce yourself to the new folks (NOT newbies. ?I believe there are many less offensive monikers.), and take a genuine interest in them. ?Make them your friend. ?Include them in your activities - your private star parties. ?Give them a ride. ?They are people looking for the pleasures and benefits of association who also have an interest in astronomy. ?That commonality will launch club growth. ?People make time for whatever satiates their basic needs. These are rules that are generally true. ?They follow Pareto's rule, i.e., 80 percent of the new folks will want socializing, and 20 percent will want the science. ?So, give them both, but realize where the priority is. $.02 _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php ------------------------------ _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php End of Utah-Astronomy Digest, Vol 107, Issue 1 **********************************************
The GRAIL trajectory to the moon has been an interesting one. As Chuck mentioned, the object of this trajectory was reduced fuel requirements, plus it gave them lots of time to make sure everything was on track. The trajectory used an Earth - Sun Lagrange point (EL1) to perform a bit of a bank shot or boomerang maneuver back to the moon. It was launched toward the sun at about escape velocity - as slowly as one can go to get to the Lagrange point, which is about 4 times FURTHER than the moon. The probes came to a very slow (Earth relative) crawl at this point where the gravity of the sun and Earth roughly balance, then a minor maneuver and the combined gravity of the sun, Earth, and moon slowly pulled them back toward Earth on a trajectory to encounter the moon this weekend. A nice graphic is available at http://www.universetoday.com/wp-content/uploads/2011/12/613150main_Lehman-3-... They approached the moon at only ~1200 km/hour, as compared to the blistering ~40000 km/hour for the Apollo missions. This weekend's 40 minute "braking" burns only reduced the speed of the aircraft by about 680km/hour (they reached this speed just a couple seconds after liftoff). So, the probe actually used MORE fuel during launch than was required to get it to the moon, but it required very little fuel to enter lunar orbit. To put into perspective how incredibly long it's taken these probes to get to the moon, if you had jumped in your car on launch day and started driving only 90 miles/hour toward the moon, you'd have arrived just before the spacecraft. Jared On Sun, Jan 1, 2012 at 4:17 PM, <baxman2@q.com> wrote:
The recent NASA lunar probes took three months to reach the Moon from the Earth. I understand escape velocity to be 7 miles per second, and it took the Apollo astronauts three days to get to the Moon. If the NASA probes used the same escape velocity as the Apollo Moon Missions; why did it take three months for the NASA probes to get there, and only three days for the Apollo spacecraft to get there?
Thanks for the info, Jared. But I'm still having trouble understanding the reason why this approach is preferable, since they went farther and used more fuel than they otherwise would have. -- Joe ________________________________ From: Jared Smith <jared@smithplanet.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Sunday, January 1, 2012 6:09 PM Subject: Re: [Utah-astronomy] Time it takes to get to the Moon The GRAIL trajectory to the moon has been an interesting one. As Chuck mentioned, the object of this trajectory was reduced fuel requirements, plus it gave them lots of time to make sure everything was on track. The trajectory used an Earth - Sun Lagrange point (EL1) to perform a bit of a bank shot or boomerang maneuver back to the moon. It was launched toward the sun at about escape velocity - as slowly as one can go to get to the Lagrange point, which is about 4 times FURTHER than the moon. The probes came to a very slow (Earth relative) crawl at this point where the gravity of the sun and Earth roughly balance, then a minor maneuver and the combined gravity of the sun, Earth, and moon slowly pulled them back toward Earth on a trajectory to encounter the moon this weekend. A nice graphic is available at http://www.universetoday.com/wp-content/uploads/2011/12/613150main_Lehman-3-... They approached the moon at only ~1200 km/hour, as compared to the blistering ~40000 km/hour for the Apollo missions. This weekend's 40 minute "braking" burns only reduced the speed of the aircraft by about 680km/hour (they reached this speed just a couple seconds after liftoff). So, the probe actually used MORE fuel during launch than was required to get it to the moon, but it required very little fuel to enter lunar orbit. To put into perspective how incredibly long it's taken these probes to get to the moon, if you had jumped in your car on launch day and started driving only 90 miles/hour toward the moon, you'd have arrived just before the spacecraft. Jared On Sun, Jan 1, 2012 at 4:17 PM, <baxman2@q.com> wrote:
The recent NASA lunar probes took three months to reach the Moon from the Earth. I understand escape velocity to be 7 miles per second, and it took the Apollo astronauts three days to get to the Moon. If the NASA probes used the same escape velocity as the Apollo Moon Missions; why did it take three months for the NASA probes to get there, and only three days for the Apollo spacecraft to get there?
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
On 1/2/12, Joe Bauman <josephmbauman@yahoo.com> wrote:
Thanks for the info, Jared. But I'm still having trouble understanding the reason why this approach is preferable, since they went farther and used more fuel than they otherwise would have. -- Joe
Because they didn't have to carry a lot of fuel on-board the probes for braking into lunar orbit, as Jared pointed-out.
On Mon, Jan 2, 2012 at 12:27 AM, Joe Bauman <josephmbauman@yahoo.com> wrote:
Thanks for the info, Jared. But I'm still having trouble understanding the reason why this approach is preferable, since they went farther and used more fuel than they otherwise would have. -- Joe
They used a bit more fuel than would have been necessary to simply get the probe to the moon (as in slam into it or fly past it). But it would have required substantially more fuel for both launch and for braking to also stop at the moon via a direct Hohmann transfer. By using the Lagrange point and the very slow approach, the overall fuel requirements were decreased, and payload mass could thus be increased. The tradeoffs are that it takes a long time to get there and it requires much planning, computing power, and adjustments on-the-fly due to the instability of the Lagrange point. If we were willing to wait years or centuries to get there, we could use various Lagrange points to send probes to almost any place in the solar system with barely more fuel than is required for escape velocity. We can even park probes at a Lagrange point and then nudge them on to some other interesting place (most any planet, the sun, a comet or asteroid such as was done with ISEE-3 - http://en.wikipedia.org/wiki/ISEE-3, etc.) or back to Earth at will. See http://en.wikipedia.org/wiki/Interplanetary_Transport_Network Jared
Thank you, Jared. I understand now. Best wishes, Joe ________________________________ From: Jared Smith <jared@smithplanet.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Monday, January 2, 2012 9:43 AM Subject: Re: [Utah-astronomy] Time it takes to get to the Moon On Mon, Jan 2, 2012 at 12:27 AM, Joe Bauman <josephmbauman@yahoo.com> wrote:
Thanks for the info, Jared. But I'm still having trouble understanding the reason why this approach is preferable, since they went farther and used more fuel than they otherwise would have. -- Joe
They used a bit more fuel than would have been necessary to simply get the probe to the moon (as in slam into it or fly past it). But it would have required substantially more fuel for both launch and for braking to also stop at the moon via a direct Hohmann transfer. By using the Lagrange point and the very slow approach, the overall fuel requirements were decreased, and payload mass could thus be increased. The tradeoffs are that it takes a long time to get there and it requires much planning, computing power, and adjustments on-the-fly due to the instability of the Lagrange point. If we were willing to wait years or centuries to get there, we could use various Lagrange points to send probes to almost any place in the solar system with barely more fuel than is required for escape velocity. We can even park probes at a Lagrange point and then nudge them on to some other interesting place (most any planet, the sun, a comet or asteroid such as was done with ISEE-3 - http://en.wikipedia.org/wiki/ISEE-3, etc.) or back to Earth at will. See http://en.wikipedia.org/wiki/Interplanetary_Transport_Network Jared _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
How well does this technique work for altering trajectory to achieve a polar orbit, either around the Moon or the Sun? Seems that with such a low relative velocity at a/the Lagrange point it would be easier to alter the trajectory to do just that. Gotta go - I'll look for answers tomorrow. Kim -----Original Message----- From: utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com [mailto:utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com] On Behalf Of Jared Smith Sent: Sunday, January 01, 2012 6:09 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Time it takes to get to the Moon The GRAIL trajectory to the moon has been an interesting one. As Chuck mentioned, the object of this trajectory was reduced fuel requirements, plus it gave them lots of time to make sure everything was on track. The trajectory used an Earth - Sun Lagrange point (EL1) to perform a bit of a bank shot or boomerang maneuver back to the moon. It was launched toward the sun at about escape velocity - as slowly as one can go to get to the Lagrange point, which is about 4 times FURTHER than the moon. The probes came to a very slow (Earth relative) crawl at this point where the gravity of the sun and Earth roughly balance, then a minor maneuver and the combined gravity of the sun, Earth, and moon slowly pulled them back toward Earth on a trajectory to encounter the moon this weekend. A nice graphic is available at http://www.universetoday.com/wp-content/uploads/2011/12/613150main_Lehman-3- 673.jpg They approached the moon at only ~1200 km/hour, as compared to the blistering ~40000 km/hour for the Apollo missions. This weekend's 40 minute "braking" burns only reduced the speed of the aircraft by about 680km/hour (they reached this speed just a couple seconds after liftoff). So, the probe actually used MORE fuel during launch than was required to get it to the moon, but it required very little fuel to enter lunar orbit. To put into perspective how incredibly long it's taken these probes to get to the moon, if you had jumped in your car on launch day and started driving only 90 miles/hour toward the moon, you'd have arrived just before the spacecraft. Jared
Escape velocity is the same for all objects. I would bet that the recent probes did not exceed escape velocity by as much as the Apollo missions did. As Chuck said, this would require a smaller booster. They still need to achieve escape velocity though. ________________________________ From: "baxman2@q.com" <baxman2@q.com> To: utah-astronomy@mailman.xmission.com Sent: Sunday, January 1, 2012 4:17 PM Subject: [Utah-astronomy] Time it takes to get to the Moon The recent NASA lunar probes took three months to reach the Moon from the Earth. I understand escape velocity to be 7 miles per second, and it took the Apollo astronauts three days to get to the Moon. If the NASA probes used the same escape velocity as the Apollo Moon Missions; why did it take three months for the NASA probes to get there, and only three days for the Apollo spacecraft to get there? ----- Original Message ----- From: utah-astronomy-request@mailman.xmission.com To: utah-astronomy@mailman.xmission.com Sent: Sun, 01 Jan 2012 16:24:51 -0500 (EST) Subject: Utah-Astronomy Digest, Vol 107, Issue 1 Send Utah-Astronomy mailing list submissions to utah-astronomy@mailman.xmission.com To subscribe or unsubscribe via the World Wide Web, visit http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy or, via email, send a message with subject or body 'help' to utah-astronomy-request@mailman.xmission.com You can reach the person managing the list at utah-astronomy-owner@mailman.xmission.com When replying, please edit your Subject line so it is more specific than "Re: Contents of Utah-Astronomy digest..." Today's Topics: 1. Re: club growth (Joe Bauman) 2. Re: Club growth (Brent Watson) 3. Re: Club growth (Joe Bauman) ---------------------------------------------------------------------- Message: 1 Date: Sun, 1 Jan 2012 00:20:24 -0800 (PST) From: Joe Bauman <josephmbauman@yahoo.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Subject: Re: [Utah-astronomy] club growth Message-ID: <1325406024.17605.YahooMailNeo@web38905.mail.mud.yahoo.com> Content-Type: text/plain; charset=us-ascii Thanks for the explanation, Patrick.Now I understand Daniel's comment. Sorry for my response, Daniel -- I thought you were dissing my guru! In fact, we're on the same side here, I'm very happy to say. -- Joe ------------------------------ Message: 2 Date: Sun, 1 Jan 2012 12:04:00 -0800 (PST) From: Brent Watson <brentjwatson@yahoo.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Subject: Re: [Utah-astronomy] Club growth Message-ID: <1325448240.62191.YahooMailNeo@web39402.mail.mud.yahoo.com> Content-Type: text/plain; charset=iso-8859-1 I believe that SLAS, or OAS, is first, a social organization and second, a layman's science organization. ?If people don't return I would postulate it is because they don't find SLAS or OAS socialization to their liking - they don't find a friend. ?If there is friendship, there will be continuing attendance at club meetings and functions. I learned long ago that clubs, organizations, societies, etc. exist to fulfill the basic need of human beings to associate with one another. ?It is written in the preamble to the club's constitution. ?Here it is. ? "We the undersigned, desiring to secure the pleasures and benefits of an association of? persons interested in astronomy; to promote the science of astronomy and its associated? sciences; to encourage and coordinate activities with professional research, do hereby? organize and constitute ourselves as the Salt Lake Astronomical Society, a non-profit? organization." The purpose is first to "...secure the pleasures and benefits of an association of persons...", and then second ?to do the science stuff. ?Anyone who has been an officer of the club will probably acknowledge that it is much harder to get the membership to engage in science than it is to get the members to socialize. ?Outreach, by the way, is a form of socialization. ?Star parties are socialization. ?How many postings do we see here about an observing session - come along. ?They are parties after all. So, my response is the following. ?If you want the club to grow, smile, introduce yourself to the new folks (NOT newbies. ?I believe there are many less offensive monikers.), and take a genuine interest in them. ?Make them your friend. ?Include them in your activities - your private star parties. ?Give them a ride. ?They are people looking for the pleasures and benefits of association who also have an interest in astronomy. ?That commonality will launch club growth. ?People make time for whatever satiates their basic needs. These are rules that are generally true. ?They follow Pareto's rule, i.e., 80 percent of the new folks will want socializing, and 20 percent will want the science. ?So, give them both, but realize where the priority is. $.02 ------------------------------ Message: 3 Date: Sun, 1 Jan 2012 13:24:37 -0800 (PST) From: Joe Bauman <josephmbauman@yahoo.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Subject: Re: [Utah-astronomy] Club growth Message-ID: <1325453077.86952.YahooMailNeo@web38905.mail.mud.yahoo.com> Content-Type: text/plain; charset=iso-8859-1 A wise comment, Brent. And that's why I think a little verbal horseplay is OK sometimes on the UtahAstronomy list. We are not professional astronomers and we don't need to restrict our notes to only scientific matters. -- Thanks, Joe ________________________________ From: Brent Watson <brentjwatson@yahoo.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Sunday, January 1, 2012 1:04 PM Subject: Re: [Utah-astronomy] Club growth I believe that SLAS, or OAS, is first, a social organization and second, a layman's science organization. ?If people don't return I would postulate it is because they don't find SLAS or OAS socialization to their liking - they don't find a friend. ?If there is friendship, there will be continuing attendance at club meetings and functions. I learned long ago that clubs, organizations, societies, etc. exist to fulfill the basic need of human beings to associate with one another. ?It is written in the preamble to the club's constitution. ?Here it is. ? "We the undersigned, desiring to secure the pleasures and benefits of an association of? persons interested in astronomy; to promote the science of astronomy and its associated? sciences; to encourage and coordinate activities with professional research, do hereby? organize and constitute ourselves as the Salt Lake Astronomical Society, a non-profit? organization." The purpose is first to "...secure the pleasures and benefits of an association of persons...", and then second ?to do the science stuff. ?Anyone who has been an officer of the club will probably acknowledge that it is much harder to get the membership to engage in science than it is to get the members to socialize. ?Outreach, by the way, is a form of socialization. ?Star parties are socialization. ?How many postings do we see here about an observing session - come along. ?They are parties after all. So, my response is the following. ?If you want the club to grow, smile, introduce yourself to the new folks (NOT newbies. ?I believe there are many less offensive monikers.), and take a genuine interest in them. ?Make them your friend. ?Include them in your activities - your private star parties. ?Give them a ride. ?They are people looking for the pleasures and benefits of association who also have an interest in astronomy. ?That commonality will launch club growth. ?People make time for whatever satiates their basic needs. These are rules that are generally true. ?They follow Pareto's rule, i.e., 80 percent of the new folks will want socializing, and 20 percent will want the science. ?So, give them both, but realize where the priority is. $.02 _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php ------------------------------ _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php End of Utah-Astronomy Digest, Vol 107, Issue 1 ********************************************** _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
participants (6)
-
baxman2＠q.com -
Brent Watson -
Chuck Hards -
Jared Smith -
Joe Bauman -
Kim