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Escape Velocity is not essential for....

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posted on Jan, 14 2007 @ 07:43 AM
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.....SPACE TRAVEL


you will be shocked to hear you dont actually need to travel at 11.2 km/sec to reach orbit..

this is a gross misconception foisted on the public by nasa and other people with an agenda...


the fact you can actually travel to any planet at any spped as long as that acceleration
is only slightly greater then the downward pull of gravity.

thuis you can actually go into space travelling at only a mile an hour
or 2 miles an hour
or even an inch an hour...!!!!!

as i said any speed as long as its upwards and is just sufficent to overcome the downward pull of earthd gravity...

remember F=MA

THUS WE DONT NEED GIANT MONSTER ENGINES.

WHAT WE REQUIRE IS AN ENGINE THAT CAN PROVIDE SUSTAINED THRUST FOR LONG TIME PERIODS.



ROCKETS ARE USELESS.all the fuel being spend in a few minutes...



what is required is an engine which can supply the thrust and be sustained and exceeds the weight of the vehicle.


the vessal will travel into space eventually
...

thus we should concentrate on propulsion systems which can provide this SUSTAINED THRUST..


also we need to increase the exhaust speed of the propellant

remember m1v1=m2v2

we can throw a kilogram out of the nozzle at at 1 kilometre/hour or we can throw 0.001 kilogram at 1000km/hour....the thrust obtained is the same...

in the second case we can reduce the mass of fuel carried with us and reduce the size of the vehicle...

thus once again we must concentrate on high exhust velocities and sustained thrust...


this is the key to space travel....

..






[edit on 14-1-2007 by esecallum]

[edit: All Caps title]
Mod Edit: All Caps – Please Review This Link.

[edit on 1/14/2007 by 12m8keall2c]




posted on Jan, 14 2007 @ 06:42 PM
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yeah i always wondered why you couldnt go 1cm higher forever.


jra

posted on Jan, 14 2007 @ 07:27 PM
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Originally posted by tomcat ha
yeah i always wondered why you couldnt go 1cm higher forever.


Besides the fact that you'd need to have huge amounts of fuel and engines that can work in thin air/no air. In order to achieve a minimum low Earth orbit, you need to be traveling at a speed of 7800 m/s to maintain that orbit.



posted on Jan, 16 2007 @ 04:01 AM
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He is right, though. As long as you can maintain sufficient thrust, you do not need to accelerate to 11.2 km/s. You just need to have enough fuel so that you can reach a distance at which your velocity exceeds the escape velocity of Earth at that distance.

Of course, "having enough fuel" is the crux of the problem. The Saturn V third stage needed to reach a velocity of 11.2 km/s when boosting the Apollo astronauts to the Moon, simply because the fuel was exhausted at a distance that was rather close to Earth's surface (relatively speaking). If you had sufficient amounts of fuel to keep thrusting all the way to the orbit of the Moon, then you would only need to reach a velocity of 1.6 km/s to escape Earth's gravity (at that point).

In fact, you could move away from Earth at a constant 10 km per hour if you wanted to (and you had an almost unlimited amount of fuel), but this wouldn't be particularly sensible !


[edit on 16-1-2007 by Mogget]

[edit on 16-1-2007 by Mogget]

[edit on 16-1-2007 by Mogget]



posted on Jan, 28 2007 @ 07:56 AM
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Originally posted by Mogget
He is right, though. As long as you can maintain sufficient thrust, you do not need to accelerate to 11.2 km/s. You just need to have enough fuel so that you can reach a distance at which your velocity exceeds the escape velocity of Earth at that distance.

Of course, "having enough fuel" is the crux of the problem. The Saturn V third stage needed to reach a velocity of 11.2 km/s when boosting the Apollo astronauts to the Moon, simply because the fuel was exhausted at a distance that was rather close to Earth's surface (relatively speaking). If you had sufficient amounts of fuel to keep thrusting all the way to the orbit of the Moon, then you would only need to reach a velocity of 1.6 km/s to escape Earth's gravity (at that point).

In fact, you could move away from Earth at a constant 10 km per hour if you wanted to (and you had an almost unlimited amount of fuel), but this wouldn't be particularly sensible !


[edit on 16-1-2007 by Mogget]

[edit on 16-1-2007 by Mogget]

[edit on 16-1-2007 by Mogget]


When scientist say escape velocity, they actually mean escaping the gavity under constant speed. It's escape velocity not escape acceleration


x08

posted on Jan, 28 2007 @ 10:45 AM
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And the most obvious and clear thing~

1 mile an hour??? Do you know how long it would take to reach LEO?
I suggest from now on, you just walk when you go to work or go shopping instead of driving. Because you don't need it~



posted on Jan, 28 2007 @ 07:03 PM
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Originally posted by NegativeBeef

Originally posted by Mogget
He is right, though. As long as you can maintain sufficient thrust, you do not need to accelerate to 11.2 km/s. You just need to have enough fuel so that you can reach a distance at which your velocity exceeds the escape velocity of Earth at that distance.

Of course, "having enough fuel" is the crux of the problem. The Saturn V third stage needed to reach a velocity of 11.2 km/s when boosting the Apollo astronauts to the Moon, simply because the fuel was exhausted at a distance that was rather close to Earth's surface (relatively speaking). If you had sufficient amounts of fuel to keep thrusting all the way to the orbit of the Moon, then you would only need to reach a velocity of 1.6 km/s to escape Earth's gravity (at that point).

In fact, you could move away from Earth at a constant 10 km per hour if you wanted to (and you had an almost unlimited amount of fuel), but this wouldn't be particularly sensible !


[edit on 16-1-2007 by Mogget]

[edit on 16-1-2007 by Mogget]

[edit on 16-1-2007 by Mogget]


When scientist say escape velocity, they actually mean escaping the gavity under constant speed. It's escape velocity not escape acceleration


Not really. Escape velocity (more like escape speed, actually, since it's independent of direction) is the speed that an object on Earth's surface must obtain to escape Earth's gravitational field without any forces other than gravity acting on it, and without taking the atmosphere into consideration. It's actually not required for getting into space, but as mentioned before, going at 1 mph would be very impractical. Besides, to get int orbit (which is usually the goal for space travel) high speeds are needed. Not quite escape velocity (since an object in orbit has not escaped Earth's gravity) but pretty close. Around 7800 m/s for low Earth orbit.



posted on Jan, 29 2007 @ 12:58 AM
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you better get to NASA with that information



posted on Jan, 30 2007 @ 03:48 AM
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Originally posted by x08
And the most obvious and clear thing~

1 mile an hour??? Do you know how long it would take to reach LEO?
I suggest from now on, you just walk when you go to work or go shopping instead of driving. Because you don't need it~



the point is we need to develop high exhaust velocity engines which can SUSTAIN thrust for a long ,long time...

1 mile an hour is simpley to get the point across...

the space shuttle blows all its fuel in under 10 minutes...after which it is helpless..a lot of fuel is thrown out at very low speed whixch means you have to carry a lot of fuel..which weighs a lot...which means you need powerful heavy engines..which means you need more fuel...which means more weight...which means more fuel....and so on and on...

look at the space shuttle...

its 99% fuel...


since m1 x v1 =m2 x v2


what we need is high exhaust velocities...which means we can carry less fuel
which means smaller,llighter vehicle...which means lower thrust..less heavy engines...which means less fuel...

see?

a downward spiral in costs and fuel and size of vehicle...


its all NASA'S fault for sticking with chemical rocket enigines for so long and wasting billions in marginal improvements...

they never committed to other propulsion methods despite researching them...



posted on Jan, 30 2007 @ 04:18 AM
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O.K in simple terms the amount of thrust to move away from gravity well has to be greater than the total gravitational force x the total mass (rest energy) of the object you want to move...

To create a positive movement you need to add more energy in the equation at one side...

However...

What if we were able to reduce the effects gravity has on an object??

Boeing tries to defy gravity



Try not to get hung up on the movie you see on TV.. The news that is... It's all there to make you believe whatever they want you to believe.

All the best,

NeoN HaZe.



posted on Jan, 30 2007 @ 01:01 PM
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Originally posted by esecallum

And the most obvious and clear thing~

the point is we need to develop high exhaust velocity engines which can SUSTAIN thrust for a long ,long time...

1 mile an hour is simpley to get the point across...

the space shuttle blows all its fuel in under 10 minutes...after which it is helpless..a lot of fuel is thrown out at very low speed whixch means you have to carry a lot of fuel..which weighs a lot...which means you need powerful heavy engines..which means you need more fuel...which means more weight...which means more fuel....and so on and on...

look at the space shuttle...

its 99% fuel...


since m1 x v1 =m2 x v2


what we need is high exhaust velocities...which means we can carry less fuel
which means smaller,llighter vehicle...which means lower thrust..less heavy engines...which means less fuel...

see?

a downward spiral in costs and fuel and size of vehicle...


its all NASA'S fault for sticking with chemical rocket enigines for so long and wasting billions in marginal improvements...

they never committed to other propulsion methods despite researching them...


Not quite; going into orbit as fast as possible is actually the most efficient way to use up energy from the fuel. Once you're in orbit, you can take your sweet time. However, using thrust to directly oppose gravity in opposite directions isn't very efficient. Think about the extreme case of your argument: let's say you have just enough thrust to lift a 1000kg ship at a constant velocity of, let's say, 1 m/s. Getting to 100km (not even to orbit, which is where most of the energy is required) would require you to provide 1000kg of thrust for 27 hours! It's not like a magical engine will be developed that can sustain thrust. All rocket engines (the only thing capable of actually propelling an object in spaces) operate the same way: mass expelled to increase the vehicle's momentum. The longer you do a burn, the more mass is expelled and the more fuel is required. You can keep on extending the burn time to infinity, but you can't keep on lowering the thrust to zero, since you will need at least 1000kg of thrust to merely raise the ship.

You're right about higher exhaust velocity being more efficient. That's why some satellites use ion propulsion once they're in orbit. Contrary to your claims, high-thrust technology such as VASIMR is being studied. However, it's not exactly easy to pull off and the thrust is much too low to actually get into orbit.

[edit on 30-1-2007 by cdrn]

[edit on 30-1-2007 by cdrn]



posted on Jan, 30 2007 @ 04:43 PM
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Originally posted by esecallum
ROCKETS ARE USELESS.

also we need to increase the exhaust speed of the propellant


Aww - not again



Look brains - if it was an easy thing to make the nozzle velocity higher, we'd have done it a long time ago. Unfortunately it is not so we're stuck with what we have for the time being.


*If anyone is wondering why I'm slightly pissed, check the ATS aircraft forum - many pages were wasted on this poster explaining 1+1 does not equal 3.




While ion based engines produce thrust for a long time frame, they do not produce enough thrust to offset the earths gravity at low altitudes = useless. All other similar concepts have the same problem.



posted on Jan, 30 2007 @ 08:48 PM
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I think I read somewhere that exhaust acceleration can be less than the acceleration of the rocket, don't quote me on it.



posted on Jan, 31 2007 @ 11:26 AM
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Originally posted by Soitenly
I think I read somewhere that exhaust acceleration can be less than the acceleration of the rocket, don't quote me on it.



There can be two kinds of forces from rockets.

Change of momentum of propellant and pressure ratio at the nozzle if its underexpanded - which is normal.

So its very possible.


You accelerate 10 kg of propellant in 1 second to 1,000 m/s, producing 10,000N of thrust, and the nozzle has a pressure ratio of 3 with a throat area of 1 m^2, assuming ambient pressure of 100,000Pa gives a nozzle pressure force of 200,000N.


So most of your force is actually coming from the pressure, not the momentum change of the propellant.



[edit on 31/1/07 by kilcoo316]



posted on Feb, 1 2007 @ 03:49 PM
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No.


You are wrong.

it comes from from the reactio mass being flung way...

i mean you can put pressurised kettle in the nozzle but it wont move.



posted on Feb, 1 2007 @ 04:10 PM
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Originally posted by esecallum
No.


You are wrong.

it comes from from the reactio mass being flung way...


Oh right... so I guess my years spent in uni learning about aircraft & rocket propulsion was a waste of time then eh?



As, I said, two forces, pressure at the nozzle exit plane, and mass acceleration - its even the same for underexpanded turbojet/fan engines used in aircraft.



posted on Feb, 1 2007 @ 05:58 PM
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I see this topic has budded from the F14 launch vehicle thread in the Aircraft forum into the space forum. Even a cursory google search of the thrust equation will show the effect of a nozzle exit pressure ratio. Both accelerated massflow and pressure ratio drive thrust.

Now with regards to simply making higher exhaust velocity engines...the primary reason these are not used for terrestrial launch is that they typically make low thrust. Exhaust stream power is .5*m_dot*(V_exit^2). Since the power goes as the square of the exhaust velocity, much more energy (stored chemical fuel energy) must be spent to achieve thrust with higher exhaust velocity instead of higher massflow.



posted on Feb, 2 2007 @ 06:16 AM
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WE ALL KNOW ABOUT K.E. =1/2 MV SQUARED. OK?

you simpley cannot understand that the heat energy from the fuel is not being translated EFFICENTLY into linear velocity of the exited propellant...
its wasted as HEAT.

HEAT.


do u really thinK that every joule of the combustion iS being used in the exit velocity....?

and u keep forgetting huge fuel MASS FLOW has WEIGHT..

why cant you understand this...?

your concerned with air and ...now pressure in enclosed spaces...

we are not interested in pressures at the nozzle....

now the velocity of the ship

v2= v1xm1/m2-m1

m1 is mass of propellent leaving the ship at velocity v1 in unit time.

m2 is the mass of ship minus the m1 mass leaving via propellant...

now u can see by making v1 high we dont need so much m1 which means m2 will be lower as less fuel needs to be carried.
which means v2 will be higher..

you can plot a graph....


IN MY NEXT NEW THREAD I WILL EXPLAIN HOW YOU CAN MAKE AN ENGINE WITH HIGH EXHUAST SPEED.

IT WILL BE CALLED:-

[edit on 2-2-2007 by esecallum]

[edit on 2-2-2007 by esecallum]



posted on Feb, 2 2007 @ 07:15 PM
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For starters, it isn't really an issue, but you are defining kinetic energy and not exhaust jet power (as I was). The purpose of my defining exhaust jet power was to illustrate the fact that the power content of the exhaust stream (and the subsequent power required to make that exhaust stream) goes as the square of the velocity.

I don't know why you bring up the obvious point that the exhaust stream has some delta_T left in it...I never argued that fact...I don't even see where that point comes from. I also fail to see why you argue the basic fact that a pressure ratio across the exit plane of a nozzle will produce thrust. Look at the classically defined thrust equation, and it is right there...it's not up for debate. That being said, it isn't a huge deal you take issue with that point, since the pressure thrust is typically small in comparison to the fluid thrust.

I agree you can thrust-match with m_dot*delta_V all day long, but what is at issue here is how much power is required to make your thrust. This is the second thread now where you have this idea that you just 'make' high-velocity exhaust and then thrust goes up and all is right with the world. It takes POWER to accelerate propellant to those speeds...power provided by your fuel. If you have developed a more efficient way of accelerating a given massflow, then I suggest a trip to your local patent attorney's office.



posted on Feb, 2 2007 @ 08:15 PM
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You need escape velocity or you won't escape gravity. Play Orbiter a bit, do a Google search, it's very educational.




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