Talk:Gravitational parameter - Revision history

Rfc: Undo revision 8503 by 18.7.125.24 (Talk)

2013-03-11T21:05:57Z

Undo revision 8503 by 18.7.125.24 (Talk)

18.7.125.24: /* SGPXgcUOwGHMnqSse */ new section

2013-03-11T17:14:49Z

SGPXgcUOwGHMnqSse: new section

ChristiaanK: /* Alternate value of mu */

2013-02-22T08:16:22Z

Alternate value of mu

Farred: talk

2013-02-20T18:38:40Z

talk

ChristiaanK: /* Alternate value of mu */

2013-02-20T17:01:02Z

Alternate value of mu

Farred: Alternate value of mu

2013-02-19T04:35:24Z

Alternate value of mu

New page

==Alternate value of mu==
I would like to point out that mu also equals g*r^2. Gravity, g, = G * m1/r^2. So G = g * r^2 /m1. Substituting that into mu = GM, we get mu = g*r^2, QED. This is the form of mu that I have been in the habit of using since gravity and radius are usually more available to me than G and m1. I have done paper missions with less accurate values but they were sufficient for my purposes. See [[People from Earth to Mars in 30 days]] - [[User:Farred|Farred]] 04:35, 19 February 2013 (UTC)

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	::However g is calculated, it is the value that I find in some references. If I do not have mu but have g and r from a reference naturally that is what I would use. Actually I have seldom found mu tabulated in the references that I have used. Where it was tabulated, it was referred to as g*r<sup>2</sup>. I just do not have the sort of references that are available to you. - [[User:Farred\|Farred]] 18:38, 20 February 2013 (UTC)		::However g is calculated, it is the value that I find in some references. If I do not have mu but have g and r from a reference naturally that is what I would use. Actually I have seldom found mu tabulated in the references that I have used. Where it was tabulated, it was referred to as g*r<sup>2</sup>. I just do not have the sort of references that are available to you. - [[User:Farred\|Farred]] 18:38, 20 February 2013 (UTC)
	:::Of course you should use the available values if that is all you have. That's why I tabulated mu values in the first place -- so everyone can see them. Perhaps we should nevertheless add a "relation to gravity" section showing how g = mu*r^-2 at distance r. If you have money to burn and want to expand your technical book collection, I can recommend [http://astrobooks.com Microcosm's bookstore]. Perhaps we should add a section for spaceflight related bookstores to [[Links and Resources]]. [[User:ChristiaanK\|ChristiaanK]] 08:16, 22 February 2013 (UTC)		:::Of course you should use the available values if that is all you have. That's why I tabulated mu values in the first place -- so everyone can see them. Perhaps we should nevertheless add a "relation to gravity" section showing how g = mu*r^-2 at distance r. If you have money to burn and want to expand your technical book collection, I can recommend [http://astrobooks.com Microcosm's bookstore]. Perhaps we should add a section for spaceflight related bookstores to [[Links and Resources]]. [[User:ChristiaanK\|ChristiaanK]] 08:16, 22 February 2013 (UTC)
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−	~~== SGPXgcUOwGHMnqSse ==~~
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−	Beth - Wow, so handsome Lailah! You're going to have a line of girls outsdie your house pretty soon! Erin is going to be first in line. =) It was so cute how sweet he was with her when you guys visited!

← Older revision		Revision as of 17:14, 11 March 2013
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	::However g is calculated, it is the value that I find in some references. If I do not have mu but have g and r from a reference naturally that is what I would use. Actually I have seldom found mu tabulated in the references that I have used. Where it was tabulated, it was referred to as g*r<sup>2</sup>. I just do not have the sort of references that are available to you. - [[User:Farred\|Farred]] 18:38, 20 February 2013 (UTC)		::However g is calculated, it is the value that I find in some references. If I do not have mu but have g and r from a reference naturally that is what I would use. Actually I have seldom found mu tabulated in the references that I have used. Where it was tabulated, it was referred to as g*r<sup>2</sup>. I just do not have the sort of references that are available to you. - [[User:Farred\|Farred]] 18:38, 20 February 2013 (UTC)
	:::Of course you should use the available values if that is all you have. That's why I tabulated mu values in the first place -- so everyone can see them. Perhaps we should nevertheless add a "relation to gravity" section showing how g = mu*r^-2 at distance r. If you have money to burn and want to expand your technical book collection, I can recommend [http://astrobooks.com Microcosm's bookstore]. Perhaps we should add a section for spaceflight related bookstores to [[Links and Resources]]. [[User:ChristiaanK\|ChristiaanK]] 08:16, 22 February 2013 (UTC)		:::Of course you should use the available values if that is all you have. That's why I tabulated mu values in the first place -- so everyone can see them. Perhaps we should nevertheless add a "relation to gravity" section showing how g = mu*r^-2 at distance r. If you have money to burn and want to expand your technical book collection, I can recommend [http://astrobooks.com Microcosm's bookstore]. Perhaps we should add a section for spaceflight related bookstores to [[Links and Resources]]. [[User:ChristiaanK\|ChristiaanK]] 08:16, 22 February 2013 (UTC)
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		+	== SGPXgcUOwGHMnqSse ==
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		+	Beth - Wow, so handsome Lailah! You're going to have a line of girls outsdie your house pretty soon! Erin is going to be first in line. =) It was so cute how sweet he was with her when you guys visited!

← Older revision		Revision as of 08:16, 22 February 2013
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	:I'm not sure why you would want to do that. For heavenly bodies, the average surface gravity g is calculated from mu using the very formula that you just gave (mu and r being determined from astronomical observation). Why would you want to work backwards from this to get mu? I agree that inaccurate values are fine for most ballpark feasibility studies, but finding accurate values takes little time and offers several advantages. A small force over an Earth-Mars transit orbit makes a big difference and inaccurate values are compounded when you work backwards from the fuel needed for the last leg of a mission to determine the fuel needed at the beginning. [[User:ChristiaanK\|ChristiaanK]] 17:01, 20 February 2013 (UTC)		:I'm not sure why you would want to do that. For heavenly bodies, the average surface gravity g is calculated from mu using the very formula that you just gave (mu and r being determined from astronomical observation). Why would you want to work backwards from this to get mu? I agree that inaccurate values are fine for most ballpark feasibility studies, but finding accurate values takes little time and offers several advantages. A small force over an Earth-Mars transit orbit makes a big difference and inaccurate values are compounded when you work backwards from the fuel needed for the last leg of a mission to determine the fuel needed at the beginning. [[User:ChristiaanK\|ChristiaanK]] 17:01, 20 February 2013 (UTC)
	::However g is calculated, it is the value that I find in some references. If I do not have mu but have g and r from a reference naturally that is what I would use. Actually I have seldom found mu tabulated in the references that I have used. Where it was tabulated, it was referred to as g*r<sup>2</sup>. I just do not have the sort of references that are available to you. - [[User:Farred\|Farred]] 18:38, 20 February 2013 (UTC)		::However g is calculated, it is the value that I find in some references. If I do not have mu but have g and r from a reference naturally that is what I would use. Actually I have seldom found mu tabulated in the references that I have used. Where it was tabulated, it was referred to as g*r<sup>2</sup>. I just do not have the sort of references that are available to you. - [[User:Farred\|Farred]] 18:38, 20 February 2013 (UTC)
		+	:::Of course you should use the available values if that is all you have. That's why I tabulated mu values in the first place -- so everyone can see them. Perhaps we should nevertheless add a "relation to gravity" section showing how g = mu*r^-2 at distance r. If you have money to burn and want to expand your technical book collection, I can recommend [http://astrobooks.com Microcosm's bookstore]. Perhaps we should add a section for spaceflight related bookstores to [[Links and Resources]]. [[User:ChristiaanK\|ChristiaanK]] 08:16, 22 February 2013 (UTC)

← Older revision		Revision as of 18:38, 20 February 2013
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	I would like to point out that mu also equals gr^2. Gravity, g, = G m<sub>1</sub>/r^2. So G = g * r^2 /m<sub>1</sub>. Substituting that into mu = GM, we get mu = g*r^2, QED. This is the form of mu that I have been in the habit of using since gravity and radius are usually more available to me than G and m<sub>1</sub>. I have done paper missions with less accurate values but they were sufficient for my purposes. See [[People from Earth to Mars in 30 days]] - [[User:Farred\|Farred]] 04:35, 19 February 2013 (UTC)		I would like to point out that mu also equals gr^2. Gravity, g, = G m<sub>1</sub>/r^2. So G = g * r^2 /m<sub>1</sub>. Substituting that into mu = GM, we get mu = g*r^2, QED. This is the form of mu that I have been in the habit of using since gravity and radius are usually more available to me than G and m<sub>1</sub>. I have done paper missions with less accurate values but they were sufficient for my purposes. See [[People from Earth to Mars in 30 days]] - [[User:Farred\|Farred]] 04:35, 19 February 2013 (UTC)
	:I'm not sure why you would want to do that. For heavenly bodies, the average surface gravity g is calculated from mu using the very formula that you just gave (mu and r being determined from astronomical observation). Why would you want to work backwards from this to get mu? I agree that inaccurate values are fine for most ballpark feasibility studies, but finding accurate values takes little time and offers several advantages. A small force over an Earth-Mars transit orbit makes a big difference and inaccurate values are compounded when you work backwards from the fuel needed for the last leg of a mission to determine the fuel needed at the beginning. [[User:ChristiaanK\|ChristiaanK]] 17:01, 20 February 2013 (UTC)		:I'm not sure why you would want to do that. For heavenly bodies, the average surface gravity g is calculated from mu using the very formula that you just gave (mu and r being determined from astronomical observation). Why would you want to work backwards from this to get mu? I agree that inaccurate values are fine for most ballpark feasibility studies, but finding accurate values takes little time and offers several advantages. A small force over an Earth-Mars transit orbit makes a big difference and inaccurate values are compounded when you work backwards from the fuel needed for the last leg of a mission to determine the fuel needed at the beginning. [[User:ChristiaanK\|ChristiaanK]] 17:01, 20 February 2013 (UTC)
		+	::However g is calculated, it is the value that I find in some references. If I do not have mu but have g and r from a reference naturally that is what I would use. Actually I have seldom found mu tabulated in the references that I have used. Where it was tabulated, it was referred to as g*r<sup>2</sup>. I just do not have the sort of references that are available to you. - [[User:Farred\|Farred]] 18:38, 20 February 2013 (UTC)

← Older revision		Revision as of 17:01, 20 February 2013
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	==Alternate value of mu==		==Alternate value of mu==
	I would like to point out that mu also equals gr^2. Gravity, g, = G m<sub>1</sub>/r^2. So G = g * r^2 /m<sub>1</sub>. Substituting that into mu = GM, we get mu = g*r^2, QED. This is the form of mu that I have been in the habit of using since gravity and radius are usually more available to me than G and m<sub>1</sub>. I have done paper missions with less accurate values but they were sufficient for my purposes. See [[People from Earth to Mars in 30 days]] - [[User:Farred\|Farred]] 04:35, 19 February 2013 (UTC)		I would like to point out that mu also equals gr^2. Gravity, g, = G m<sub>1</sub>/r^2. So G = g * r^2 /m<sub>1</sub>. Substituting that into mu = GM, we get mu = g*r^2, QED. This is the form of mu that I have been in the habit of using since gravity and radius are usually more available to me than G and m<sub>1</sub>. I have done paper missions with less accurate values but they were sufficient for my purposes. See [[People from Earth to Mars in 30 days]] - [[User:Farred\|Farred]] 04:35, 19 February 2013 (UTC)
		+	:I'm not sure why you would want to do that. For heavenly bodies, the average surface gravity g is calculated from mu using the very formula that you just gave (mu and r being determined from astronomical observation). Why would you want to work backwards from this to get mu? I agree that inaccurate values are fine for most ballpark feasibility studies, but finding accurate values takes little time and offers several advantages. A small force over an Earth-Mars transit orbit makes a big difference and inaccurate values are compounded when you work backwards from the fuel needed for the last leg of a mission to determine the fuel needed at the beginning. [[User:ChristiaanK\|ChristiaanK]] 17:01, 20 February 2013 (UTC)