kallis@pen.DEC (05/14/85)
three things have occupied this netfile for the past few days: 1) trying to explain a seeming (Newtonian) paradox concerning two space- craft approaching each other at near-luminal speeds, 2) getting "unstuck" from the middle of a spacecraft/space station in 0 g, and 3) explaining the "slingshot effect." Throwing in my $0.02 worth --- 1) Tachyon theory indicates that things either can go slower than or faster than c, but never achieve c. If this is correct (and there is no theoretical reason it might not be), it leads to all sorts of interesting speculation as how on may nbe able to transfer from one state to the other; relatively meaningless now, but perhaps of interest to our grandchildren. 2) On getting "unstuck": one first has to get stuck. It would be fairly difficult for anyone in a low-Earth orbit to _get_ stuck. Even if such a person were boundand gagged and put in still air in the midst of a spacecraft chamber, the gravity gradient between the far side and the near side of the spacecraft/station would eventually result in a reposi- tioning of the victim (unless you managed to place him or her _exactly_ at the center of mass -- and then, it would be his or her centers of mass that would have to be at that point). Of course, any slight maneuver of the spacecraft also would remove the difficulty. 3) As explained in some of the previous communications, there is a transfer of energy from the planet to the spacecraft using the slingshot effect. This slows the planet down minutely -- There Ain't No Such Thing As A Free Lunch, as has been said. From a practical standpoint, the planet is affected minimally, therefore, the presumed "free ride" for the probe. It's very important to understand the elements of energy transform- ation and transfer, or it's easy to fall into traps. A book of the late 1940s, _Rockets and Jets_ by Herbert Zim, once tried to explain orbital decay by strength-of-gravitational-field at different gradient points (in a **far** more popular way than the foregoing) without factoring in atmospheric drag. To a layman, this would imply that things lose momentum in high-gravity environments: I don't know if the author was careless or confused. Steve Kallis, Jr.