Quick Questions, Short Answers - No Debate

In my model you are strapped to one of the propeller blades. --Percy

I spent about two minutes trying to figure out how that was analogous to space travel before I realized you were burning me. It's a slow brain day.

Oh wow! The Bootstrap Drive!

Almost. Change the "nothing" to "everything" and you've got it This is a classic case of taking the debunking of a fallacy too far. The original fallacy is thinking that the exhaust gases push against the ground at take off, generating the upward thrust. But in dismissing this erroneous idea, the correct situation of the exhaust gases interacting with the walls of the combustion chamber seems to have been dismissed as well.The obvious picture to visualise is a small rocket sat in zero-g inside the combustion chamber of a much larger rocket. The small rocket fires. Observed from a distance, the large rocket will seen to be expelling exhaust gases, yet will not move. It will only accelerate once the small rocket impacts on the larger combustion chamber.

If I designed a rocket engine that had no combustion chamber at all - let's say a pair of hollow tubes delivered propellant and oxidizer to a location well aft of the rocket where it was ignited - would it be able to move? Or would it move simply as a function of the fuel and oxidizer it was spraying out, with the energy of combustion lost?Thanks for the correction, though. I was hoping you'd arrive to explain how wrong I was.

I think I've sussed this one out ...

Essentially, yes. There will also be some propulsion from the impact of the combustion gases on the rear of the ship. Think of the Orion spacecraft design, which ejects H-bombs out the rear, detonates them, and rides the shock-wave.

I think that was my favorite part of Larry Niven and Jerry Pournelle's "Footfall."But now that I think of it - since you asked - why is there a shock-wave at all in the vacuum of space? It's easy to imagine a longitudinal wave through an atmospheric medium or the hot gases of chemical combustion, but how does the mechanical energy from the nuclear detonation actually reach the blast plate of an Orion-type spacecraft?

Is it time to move the propulsion to its own thread?

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Anyone so limited that they can only spell a word one way is severely handicapped!

This was on myth-busters last nite, they used an air boat with the engine on backwards, it actually moved forward. Blow your own sail

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"I hate to advocate the use of drugs, alcohol, violence, or insanity to anyone, but they always worked for me." - Hunter S. ThompsonAd astra per aspera

It's not a shock-wave but a "shock-wave" The interplanetary gases are too tenuous to be of interest here, so we are merely looking at the constituents of the bomb flying apart and imparting their kinetic energy to the back of the Orion blast plate. So I guess it makes sense to surround each bomb with a decent amount of "working fluid" that can transmit the explosion energy to the space-craft.We do get real shock-waves in space: the termination shock in the heliosphere being an obvious one, where the solar wind is impacting the interstellar medium.

I watched march of the penguins. Remember the part where they try to transfer the egg and fail? The egg freezes and remains there for all of eternity.There's a limited number of organic molecules on Earth. Almost everything gets recycled. But no, the penguins have to spend energy to produce the eggs and then dump them where it's always cold all the time so that the material is never recycled.(1) How long will it take for the penguins to take out enough organic material from the echosphere to start impacting the rest of us?(2) Are they anti-life?(3) Should we exterminate them to prevent a future disaster?

According to my calculations, if the earth really was billions of years old then we'd all be knee-deep in discarded pinguin eggs. Since we're not, then the earth is young, evolution is false, creationism is true and there is a god. QED.

They're just sequestering carbon. That's the latest fad. Give them a break.

The dry biomass of the earth is ~ 3 quadrillion kilogrammes.An emperor penguin's egg weighs ~ 500g.An egg is ~ 75% water.Hence it would take ~ 24 quadrillion eggs to sequester the Earth's biomass.The world population of emperor penguins is something under half a million, and they lay one egg a year. Only half of them are female, so let's call it a quarter of a million eggs per year.Obviously they need to maintain their numbers in order to carry out what would necessarily be a very long-term plan. However, even if we were to neglect this factor, it would still take them 96 billion years to convert all life on Earth into penguin eggs. Yes. They're just not very good at it. While the threat from their egg-laying activities is minimal, there is always the possibility that they'll think of some more efficient way to destroy life as we know it. It would therefore be prudent to take some pre-emptive measure such as the annihilation of all penguins.There will be the usual protests from animal rights activists, so I suggest that we kill them too. You can't be too careful.Edited by Dr Adequate, : No reason given.