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A Pair Of Short Posts on Gravitation and Atmospheric Dynamic Pressure

  1. May 19, 2012 #1
    Here's an explanation I posted elsewhere concerning the Project Apollo missions to the Moon, which I wrote in an attempt to convert certain doubters:

    The vastly greatest input of energy into the Apollo system was clearly required to get the spacecraft, first, above Earth's atmosphere and in orbit around Earth (the job of the S-IC stage, the S-II stage, and the initial burn of the S-IVB stage), then to escape Earth's gravity from a point above the vast bulk of Earth's atmosphere and resulting dynamic resistance (i.e., aerodynamic drag) via the second burn of the S-IVB stage.

    With that initial impetus, all the spacecraft has to do is coast (i.e., no fuel needed, except for the mid-course correction at the point at which the CSM/LM complex transited from Earth's gravitational influence to the Moon's gravitational influence, at which point the gravitational forces of the two bodies cancel one another out, and only minimal thrust is needed to point the spacecraft in the proper direction. Once in Lunar orbit, the Moon's gravitational pull. which is 1/6 that of Earth's (actually less than that at Lunar orbital altitude, as gravitational attraction upon an attracted body decreases over the distance from the center of mass of the attracting body as the square of the distance between them), requires only a short burn from the SM main engine to slow it down enough to enter into Lunar orbit. The descent of the LM to the surface, under the influence of 1/6g, is a gentle approach requiring only a bit of contrary vector from the LM descent stage to allow a soft, controlled landing. Once finished upon the Lunar surface, the tiny LM ascent stage engine, working against 1/6g and no atmospheric dynamic pressure whatsoever, is quite sufficient to lift the LM ascent stage back up to the CSM complex still in orbit around the Moon, continually manned, in the case of Apollo 11, by Michael Collins. The two spacecraft mated once again, and the astronauts and Moon rocks (and/or cheese!) transferred from the LM to the CSM, it requires only a short burst from the SM main engine to escape Lunar orbit (once again, 1/6g and still under the massive inertial influence of the S-!C, S-II, and S-IVB stages of the Saturn V launch vehicle), and transit back to Earth's gravitational influence, with another mid-course correction on the way back in just as was done on the way out. Nearing Earth's atmosphere, one more brief burn from the SM main engine serves to decelerate the CM for reentry, after which all the CM needs to do is pass back into Earth's atmosphere (which decelerates it further), and, then to glide gently back down to Earth's surface under three huge parachutes.

    The whole thing is done by INERTIA and GRAVITATIONAL ATTRACTION! A huge input of energy is imparted to the system by the combustion of the fuel of the three enormous stages of the Saturn V launch vehicle, and this input of energy is used by the spacecraft as she coasts through space in the total absence of aerodynamic drag and having already gained velocity sufficient to escape from Earth's gravitational attraction, as inertial power sufficient to bring the spacecraft to the Moon and back to Earth again.

    Your objection is akin to saying that a bomb dropped from a Japanese Betty bomber onto the port of Darwin must need rocket assistance to reach the port facilities, as no other explanation exists for how the bomb is able to fall several thousand feet to Earth's surface several thousand feet forward of the dropping point.

    Learn about inertia and gravitation, man. INERTA AND GRAVITATION!!!!!

    ***

    And here's a piece I posted describing the shape of the outer layer of the Solar System:

    It'll take a few months or years, according to the Jet Propulsion Laboratory, for the Voyager 1 spacecraft to pass through the heliopause (the limit of the influence of solar wind and magnetism in space, and, thus, the formal edge of the solar system) and enter interstellar space.

    I can't wait to find out what's out there!

    In particular, I would love to know the characteristics of the "Bow Shock", which is the pile-up of interstellar gasses at the leading edge of the solar system which constitutes the dynamic pressure of interstellar gasses providing aerodynamic drag to the elongated (actually teardrop-shaped) bubble of solar influence which constitutes the solar system. You see, when NASA launched Voyager 1 and Voyager 2, they launched them in the direction of the leading edge of the solar system bubble as it passes through interstellar space, so as to reach the outer limit of the solar system as quickly as possible. It's been 35 years since Voyager 1 was launched, and it's just now closing on the heliopause.

    I can't wait to find out what's out there beyond!!
     
  2. jcsd
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