Hi Raoul - and welcome to the forum. I will take your questions as an exercise towards perfecting / clarifying my argumentation against the possibility of rockets being propelled in the vacuum of space.RaoulMarz wrote:Coming back to the rocket - the propulsion is due to the pressure differential in this glob in which the rocket resides. So that it implies the high density gas would be in the area surrounding the rocket nozzle, and the lower density gas more or less above rocket nozzle in the direction of the nose cone.
I think that what you're saying is similar to what this self-professed 'rocket scientist' is saying :
The thing is, what Karen refers to is the recoil effect / or recoil force that occurs in nature when, for instance, you fire a gun: the bullet ( object A ) will exit at high speed from the gun's nozzle - and might even pierce an armor plate - while you ( object B ) will just feel a slight backward jolt in your wrist. The force of that jolt is given by the amount of air displaced by the gunpowder's explosion inside the gun's muzzle - while its energy is obviously proportionate to the bullet's weight / size / mass - AND SO ARE THE RELATIVE SPEEDS of the objects ( A & B ) involved: the bullet (object A ) will travel at maybe 1000km/h - while your wrist ( object B ) will be nudged backwards at, well... perhaps 10 km/h at the most?KAREN (self-professed rocket scientist of the Straightdope website) - says:
"The truth is that the rocket does have something to push against: namely, its own fuel."
http://www.straightdope.com/columns/rea ... m-of-space
Just for once - I'm going to trust Wickedpedia on this matter...
Similarly, if you sit in a wheelchair holding a basketball - and throw it with all your strength in front of you (at a speed of, say, 40km/h), this will not propel your wheelchair backwards at 40km/h. Yes, It will make you and your wheelchair slowly roll a bit backwards - but not much.Misconceptions about recoil
Although energy must be conserved, this does not mean that the kinetic energy of the bullet must be equal to the recoil energy of the gun: in fact, it is many times greater. For example, a bullet fired from an M16 rifle has approximately 1763 Joules of kinetic energy as it leaves the muzzle, but the recoil energy of the gun is less than 7 Joules.
This is to say that I do not deny the existence of the recoil effect / or recoil force. However, I do not think that - as NASA claims - this effect is sufficient to propel, say, a 100.000kg rocket (still bound by Earth's gravity) at hypersonic speeds - just by ejecting a certain amount of fuel-per-second out of its nozzle. You may argue: "but NASA says the fuel is ejected at the hypersonic speed of 4,4 km/s!". Well, here we have another big problem with NASA's claims - because they also tell us that their rockets need to attain almost twice that speed (the famous "8km/s escape velocity") in order to exit our planet's atmosphere & gravitational pull. So, even if a given, constant mass of fuel is being ejected at 4,4km/s - it couldn't possibly propel the 100.000kg rocket mass at 8km/s !
Here is a diagram to illustrate my points, once again. Hopefully, it isn't too cluttered / unreadable (sorry for the vertical text!) :
(In the right-hand diagram, the puff seen below "A" symbolizes the free expansion of the rocket exhausts in the vacuum of space.
Any gases expelled in vacuum - as of the laws of thermodynamics - will not do any work whatsoever. Even Newton would agree!).
I dearly hope Karen-the-rocket-scientist (of the Straightdope website) will come by and defend her theories - and their website's slogan : "Fighting ignorance since 1973". http://www.straightdope.com/columns/rea ... m-of-space
We (the human species - or any of our gravity-bound objects) have no means to propel our weights beyond the boundaries of the fluids of air, much as dolphins have no means to propel their weights beyond the boundaries of the fluids of water. Squibs (calamari) propel themselves very fast indeed by ejecting water out of their bodies (much like rockets eject hot air from their nozzles), and sometimes, squibs will even jump out of the sea and crash-land upon ship decks. But so far, we don't know of any high-flying, cosmic space-squibs.