[truthseeker67]

the reason why thrust cant work is simple
thrust equals = weight in order to have weight we need gravity.
see its like this in space everything weighs nothing so i would say a rocket weighs 0
or put like this rocket =0
                       thrust=0 because without gravity there is no weight behind the thrust
to cause a reaction so no movement would take place.
on earth if you sit in a chair that has wheels on it and throw a heavy ball you would
move back, and guess why of course because of gravity.....see gravity makes the ball weigh something but if you did the same thing in space you wouldnt move because you and the ball weigh nothing at all .

[Pmb]

the reason why thrust cant work is simple
thrust equals = weight in order to have weight we need gravity.

You're quite wrong. Space vehicles use thrust in space all the time so you're wrong merely by observation.

Anyway, that is not what thrust is. Thrust is the force exerted when mass is ejected which then has momentum. Since momentum is conserved there must be a back reaction on the rocket expelling the mass. That's Newton's third law. See http://en.wikipedia.org/wiki/Thrust

Thrust has absolutely nothing to do with gravity other than a rocket which has thrust can overcome the force of gravity and escape the gravitational pull of a gravitating body.

[truthseeker67]

look when water comes out of a hosepipe with high pressure it is simply chucking out
weight, and thrust is weight why do you think rocket engines are said to create pounds of thrust, so then what are pounds.....see pounds are weight. the explosive gasses of a rocket engine on earth are chucking more weight out than what the rocket  weighs thats why it goes up. In space the water and the hosepipe wouldnt have any weight so  no recation would take place . Look have you ever asked yourself why all the satalites and space station included are all only in orbit, there is not one item of any sort further than orbit because they cant get there. they call something a space station but in fact it is not in true space it is still in the earths boundarys which we call orbit and guess what thrust works there and guess why?

[CliffordK]

Keep in mind that there is no true "zero-gravity", at least with respect to the space where we've sent rockets and space ships.  See the wikipedia page on microgravity.  The gravity in low earth orbit (where the Hubble and International Space Station are) is just about the same as it is on Earth.

The effect of weightlessness is that of constant freefall, either with an object in orbit such as the satellites around Earth, or coasting in a non-orbital trajectory like the Voyager probes.

In fact, one way to provide artificial gravity in space would be to provide constant thrust, except that we don't have the technology to provide significant amounts of thrust for long periods.

I'm, not quite sure why rockets in the USA are rated with pounds of thrust.  Perhaps Newton's of thrust would be a better measurement which would indicate a force applied to a mass through a distance for a period of time.

[truthseeker67]

i live in the UK and i relate to thrust being in pounds but Newton’s are in the metric system. Since it seems to be the USA that makes a lot of rockets going everywhere or nowhere i think pounds fits the bill here. its just model jet and rocket, pulse jet engines are often in pounds of thrust, Oh yes as long as we are within the earths atmosphere the rocket engine  which is chucking out thrust, weight, pounds more than it weighs to get up there is acting with two important things Gravity is needed to give the thrust weight, imagine seeing a flame out the back of a rocket with no weight no substance behind it just like a blow torch a flame without any force behind it that's not going to move much is it .then we come to the next important thing its called air or atmospheric gasses. the thrust of a rocket engine has to have something to push against it cant push against its self. That would be like bolting an engine with a prop on it to a boat and pointing it at the sail do you think the boat would move? Of course it wouldn't we have created a sealed circuit where no reaction can take place. so in orbit the elements needed for trust to produce momentum still exist, but in true space or outside higher orbit there is a vacuum no air no gasses no gravity not much of anything for thrust to push against and i simply don't believe a rocket can push a against its self using Newton’s third law. In space there is no third law and if i believed there was i wouldn't of started this topic. Not even the rocket plane that was built the x 15 could get free of orbit and into true space when it should of been more than worthy to get there, self contained oxidizer plenty of fuel, plenty of thrust but what happened when they tried to break through the thrust died back and they were forced back to orbit like everything else that's why there's so much space trash round the earth they cant put the satellites further out because they know its impossible

[CliffordK]

Consider two blocks with a spring under compression between them, but not attached to the blocks.

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In a frictionless environment (on ice, in space, on an air table, whatever), release the spring, and one block goes right, the other goes left.  BOTH blocks move in opposite directions.

That is essentially how a rocket engine works, except the exhaust of the rocket engine (mass) is expelled at high velocity.  While only a little is released at a time, for a large rocket, more mass is lost through the burning rocket fuel and forcing it out at high velocity behind the rocket than the mass of the remaining rocket structure.

Space Junk is around Earth because most of our satellites and space missions have been launched to the area around Earth because that is where they are needed, and it is easier to access.  There have, of course, been a couple of missions to the moon (still technically within Earth's gravity), but probes have also been sent to all of the planets, a couple of comets, and even to dwarf planets, as well as being put into orbit around the sun.  The Voyager probes are now leaving the solar system, and while still under the influence of the sun's gravity for the next thousand years or so, eventually they will eventually pass beyond the sun's gravity, and head towards the next star.

[truthseeker67]

hi cliff nice illustration the coiled spring under tension would work almost anywhere no doubt about it even in deep space i expect. But the spring under tension has two surfaces to act on and push against, pushing on both sides at the same time now you have a reaction. but going back to the thrust coming out of the engine in my mind space being a vacuum and void of anything to push on means that the blast energy  would just be absorbed out into space thrust would have to fire up against something.I see a vacuum as wanting to suck the guts out of something including the thrust leaving the rocket trying to push against its self again. And if we took one block and could compress the spring against one side of the one block in space and release the spring what would happen to the block do you think? would the block leave the spring or would they leave each other or would the block stay and the spring whiz off . Thing is i don't know if we can compare a block and spring to thrust because of the way the energy is released like for example if i was in space and i was holding a cannon ball and flung it away from me very fast do you think i would go in the opposite direction. So lets say that i am the block of wood and the cannon ball is the spring also noting in space me and the ball are not going to weigh much if anything at all and me pushing against the ball as fast as possible really my hands are acting as the spring part,  when this is done on earth you get recoil so i get pushed back but in space things have mass but no weight to act on each other so where is the reaction going to come from to push me back. Momentum in space is a strange thing take a petrol engine the way the crankshaft is weighted and balanced to stop at a certain point. In space that weighted crankshaft wouldn't know where to stop if it could run because it wouldn't weigh anything. So the weight that is produced in pounds of thrust by a rocket engine has got to have something to exert force against to get its forward motion. orbit provides that because it is still earths atmosphere, i mean there's all sorts of elements and various gasses the thrust can act against.

[Pmb]

look when water comes out of a hosepipe with high pressure it is simply chucking out
weight, and thrust is weight ..

You're confusing force with gravitational force. In Newtonian physics they are different things. Force and weight are different things. Please learn the difference.

[truthseeker67]

yes the forces are different  but lets get back to the thrust in space issue . could a water rocket under high pressure when forcing out its charge into space move forward, would it be said that the rocket would push itself away from its own charge rather than pushing against the void of space in order to move because on earth the charge of water would have weight behind it but would the charge of water in space have weight too!. like on earth a hosepipe will take off under thrust if not held down because its chucking out weight in the form of pounds of thrust .  The more weight it chucks out the faster it wants to go up. Can this weight ratio apply in space where weightlessness dominates . 

[CliffordK]

I think the point is that while you may not have weight when in freefall in space, you still maintain the mass which opposes change.

Is a Hydrogen/Oxygen engine a special type of high temperature/pressure water engine?

In a sense, the combustion of the hydrogen/oxygen does occur outside of the rocket.  However, perhaps the idea is that the expanding gas doesn't "disappear" immediately, but presses against the rocket engine bell.

[dlorde]

yes the forces are different  but lets get back to the thrust in space issue . could a water rocket under high pressure when forcing out its charge into space move forward, would it be said that the rocket would push itself away from its own charge rather than pushing against the void of space in order to move because on earth the charge of water would have weight behind it but would the charge of water in space have weight too!. like on earth a hosepipe will take off under thrust if not held down because its chucking out weight in the form of pounds of thrust .  The more weight it chucks out the faster it wants to go up. Can this weight ratio apply in space where weightlessness dominates . 

You seem to be confusing mass with weight. Weight is the effect of gravity acting on the mass of an object. The mass is constant independent of gravity, but weight depends on gravity. On the moon, an astronaut has the same mass as on Earth, but weighs less because there's less gravity acting on his mass. In space, objects have no weight but still have the same mass. You can tell how massive an object is even in space, where it has no weight, by how hard it is to get it moving or slow it down; this is due to its inertia.

You've already had thrust explained to you - Newton's 3rd Law, 'for every action there is an equal and opposite reaction'. A rocket in space throws out exhaust and gets an equal reaction in the other direction. There's no requirement to push against space - it's the same principle as pushing someone away from you on ice, they will slide in one direction, you will slide in the opposite direction.

[Kryptid]

The fact that spacecraft have been sent to and landed on Venus, Mars and Titan proves that your reasoning is incorrect. That alone should tell you that there is a flaw in your argument (unless one were to propose some kind of inane conspiracy theory about how all of the space agencies of the world have faked these missions...).

[CliffordK]

Even in the vacuum of space, no doubt igniting tons of propellant in the exhaust bell creates transient pressure.

[Lmnre]

In space, objects have no weight but still have the same mass.

...and so they develop equipment and methods to measure mass, such as people's masses as part of monitoring their health. Quite the high-tech "bathroom scale". What you don't notice is that, according to Newton's Third Law of Motion, as the person moves "up" and "down", the ISS is moving (ever so slightly) "down" and "up".

[truthseeker67]

thing is man never went to the moon in the first place alone other planets. For a start when you enter into space the radiation is so strong nothing could survive the trip and live to tell the tale. Watch this folks even if you think its not true its still good from a science fiction point of view enjoy.

[dlorde]

thing is man never went to the moon in the first place alone other planets. For a start when you enter into space the radiation is so strong nothing could survive the trip and live to tell the tale.

Of course, that's complete nonsense. Funny though.

[alancalverd]

thrust equals = weight

Not true. Never mind space flight, just look at an aeroplane. Thrust acts forward (assuming the propellor is in the usual place, doing its normal job), weight acts downward. Orthogonal vectors cannot be equal.

[Kryptid]

thing is man never went to the moon in the first place alone other planets. For a start when you enter into space the radiation is so strong nothing could survive the trip and live to tell the tale. Watch this folks even if you think its not true its still good from a science fiction point of view enjoy.

Even if your radiation claim was true, it ignores the fact that such radiation would not be an issue with the unmanned probes that have been sent to other places in the Solar System. What about the Venera probes that landed on Venus? The Pathfinder, Phoenix, Vikings 1 and 2 and other landers on Mars? Huygens on Titan? The Luna landers on the Moon? Those machines had to get there somehow, and they didn't do it by teleportation.

[dlorde]

The radiation dose for the Apollo moonshot astronauts was less than the allowable yearly dose for nuclear workers. Full details are in this NASA report.

[truthseeker67]

could you imagine all the heat the vessels would absorb in space even with the protection they claim they have, keeping them cool just on batteries or whatever i know they use materials to reflect heat but even a mirror in the sun can get very hot.The outer shell of a spacecraft is acting a bit like a flask but sooner or later that heat is coming through. Read about the damage and problems the sun and radiation causes the satellites in orbit.