Might be worth noting that mass and weight are not the same item. a mass of 1kg is always 1kg (upto relatavisitc limits).
It has been some time since I did orbital mechanics but I think the main first order factors are the simple gravitational laws. I think a little can be gained by geographic positioning and launch direction depending on mission, but I do not think it is significant in the overall energy calculations.
EuroFlyer wrote:
Airborne_Again wrote: A toroid is the shape of a doughnut. I think the word you want is “spheroid”.You’re right.. corrected… thanks.
Looks more like lunch time comment than scientific truth 
I still don’t see how much 1000mph benefit you get from earth rotation compared to 16000mph on orbit, unless you include the wall of friction from air density at low altitudes?
For sure, you should not launch from equator if you are looking for polar orbits or if you want the thing to land back on your land
Airborne_Again wrote:
A toroid is the shape of a doughnut. I think the word you want is “spheroid”.
You’re right.. corrected… thanks.
EuroFlyer wrote:
Earth is a toroid
A toroid is the shape of a doughnut. I think the word you want is “spheroid”.
OK; the bit I missed is that the “weight reduction” is proportional to the square of the velocity. So the 1/16 is really 1/256 which is below the noise caused by mass concentrations in the earth.
Earth is a spheroid, where distance between surface and center is bigger at the equator than that it is at the poles.
Therefore there is more mass between an object and the center at the equator than at the poles, creating a slightly larger gravitational force than at the poles. This compensates for rotational speed and centrifugal force. Rockets aren’t launched at / near the equator because of “less gravity”, but because of the 1000mp/h speed they “already” have when launched, in relation to space – i.e. the moon, venus, or planetary system.
My understanding is that equatorial launches are a great benefit for equatorial orbits (the most common being geostationary), as you do not have to spend fuel changing the plane of your orbit ot match the equator.
Centrifugal force on the equator is about 0.03224m2/s (https://www.omnicalculator.com/physics/centrifugal-force), which is as already mentioned about 1/280th of the normal earth gravity.
You would formulate the question as why take the hassle to orbit from the equator?
It does not seem you have much gain from earth rotation/gravity at equator? Anything to do with upper winds or just convenience?
If you are looking for low-cost energy launch it needs to be like Nasa/Virgin/Tesla ones, sent to low space orbits using TurboProps/Jets that rely on air density to get you higher
I don’t think you need old platforms/rockets, probably if you are going to the moon/mars?
The answer is already there in https://www.euroga.org/forums/hangar-talk/10207-gravity-puzzle#post_198537
The centrifugal acceleration is a quadratic function of speed.
1000mph is cca 1/16 of orbital speed, hence the reduction of gravity at equator due to centrifugal effect is cca 1/250 of the surface gravity.
(I did not check the numbers … )
My original Q still stands. A 1kg weight travelling along the equator at 16000mph will weigh nothing because the angular acceleration balances the earth’s gravity. Go up a little (the atmosphere is really quite thin relative to the earth’s diameter) and you are in low earth orbit.
I am sure the answer is simple, however
