# Optimal time for satellite rocket launch considering moon gravity [closed]

As per this The Gravitational Force of the Earth and Moon on Each Other Moon is pulling us with a force equal to 1/300,000th of our weight. I have read this Is the fuel burn for a satellite launch affected by the position of the moon relative to the launch site? NASA do no wait for moon to come overhead of rocket.(why?)

Considering this heavy rocket http://www.spacex.com/falcon-heavy have mass of 1394000 kg .

If the rocket is launched when moon is overhead it can save upto 13661200/300000 = 4.64 kg of load or might be more? (as we go above in space the gravity of moon increases and earth gravity decrease.)

Update : removed W = 1394000 * 9.8 = 13661200 kg as it was in 1g environment.

How to calculate pulling force to rocket when below planets are in line?(diagram just for reference)

• Consider, for a moment the fluctuation in the total atmospheric drag at launch due to differing weather conditions. Are these larger or small than the concerns you ask about? By what factor? Jan 31, 2016 at 15:53
• i understand the weather condition. i guess small concern. pulling gravity on rocket by moon, venus, mercury and sun. Jan 31, 2016 at 16:38

The gravitational attraction between any two bodies of masses m and M, separated by a distance R, is $$F=\frac{GmM}{R^2}$$ and in the case of the moon and a body on the surface of the earth this amounts to $$F = \frac{6.67\times 10^{-11}\times 7.34\times 10^{22}\times m}{{(3.8\times10^8)}^2} = m\times({3.4\times{10^{-5})}}$$ and your second calculation, although generally correct, provides a force in newtons, as well. To compare this to the weight of the rocket, you need to divide by 9.8, so the gravitational attraction of the moon on the rocket is the equivalent of about 4.5 kg mass attraction to the earth. Since the Falcon weighs (as you have noted, $1.4\times 10^6$ kg, this amounts to a mass reduction of .0003%.