Evidence from the early space probes that Lunar gravitational gradient calculations were possibly flawed:
The United States and the Soviet Union started to send probes to the Moon in the late fifties. Most of these initial probes met with miserable failure. It is posited here that the reason for these early failures were due to a miscalculation of the lunar gravitational gradient.
While is would appear that the calculated mass of the moon was accurate enough to determine the surface gravity (1/6 of Earth’s gravity) this is not sufficient data required to properly calculate landing or impact velocities if the moon were assumed to be a hollow spheroid instead of a homogenous mass of rock throughout it’s volume.
This is because in the case of a hollow spheroid the center of mass is much closer to the surface of the moon if in fact the moon is hollow than if it really were a homogenous mass of rock. The location of the center of mass of any celestial object is critical in determining it’s gravitational gradient, hence the final velocity of any object required to soft-land or otherwise come in contact with the moon would not be known unless the location of the center of mass is somehow determined.
The first of three early successful probes, Luna 1, was launched by the Russians on January 2, 1959, was not required to land, but rather “Flyby” the moon at a distance of about 4600 miles. This is a sufficient distance from the surface where exact knowledge of the location of the center of mass is not critical to success.
Luna 2 became the first manmade object to hit the moon. Here though, the probe was allegedly not designed to withstand impact, so no conclusions were drawn about the fact that it ceased to function thereafter.
Luna 3 circled the far side of the moon, took some pictures, and sent them back to the earth. Strangely, Russian moon exploration came to a four year stop after these initial successes. The Russians were characteristically secretive about the data they collected.
The American efforts were almost laughable at first. The Ranger space probes were designed to hard land on the moon. Ranger 3, launched on January 26, 1962 , missed it’s target completely and went into solar orbit, Ranger 4 hit the moon but did not send back any useful information. Ranger 5 missed the moon by 450 miles and the whole program was put on hold for two years.
Ranger 6 allegedly had it’s electrical system burn out in flight and no pictures were sent.
The Russians re-activated their space program, but their Luna 5, launched on May 9, 1964, crashed at full speed on the moon, when it was intended to make a soft landing. Luna 6 utterly missed the moon.
Luna 7 crashed on the moon when it’s retro rockets fired too soon, which is a significant detail in relation to where one assumes the moon’s center of gravity to be located in relation to the surface.
This is because of the fact that if the moon were assumed to be a homogenous rock, the braking required to make a soft landing could begin taking place at an earlier time than if the moon were a hollow spheroid of the same mass.
The reason for this is that the accleration that gravity imparts to a landing spacecraft is lower if the center of mass is further away from the landing surface, therefore a slower burn rate of fuel is allowable to soften the landing. Hence an earlier ignition starting time may be allowed.
Ignition start time is also one of the easiest flight parameters to control, much moreso than burn rates on any rocket motor.
Miscalculation of the moon’s gravitational gradient cannot therefore be ruled out as a reason for the too early start time of Luna 7′s landing rocket motor.
Luna 8 also crashed on the moon , but luna 9 was successful, and became the first spacecraft to soft land on the moon.
Lunar probes from both the United States and the Soviet Union were more succesful after this. This cannot most likely be attributed to some sudden advance in the quality of the hardware or telemetry methods of both space programs, whereas it is much more likely to be a result of recalculation of the lunar gravitational gradient.
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