Escape Velocity?

[YT2095]

can anyone here explain to me what escape velocity is all about? and why it needs to be so fast?

To me I can`t picture any problem in my head about a vehicle going upwards at any speed slow or fast that would eventualy get into orbit, even if it were just at 1 mile an hour (ignoring fuel problems). and why couldn`t we take a helium ballon up to the edge of space and just launch our satelites from there using smaller rockets just to go that extra bit of distance?

[JaKiri]

Because it costs more.

[YT2095]

Is it though?
Surely it would be more cost effective and safer to get half way there under conventional means?
I think there`s more to it than cost, I just don`t understand this escape velocity thing? and why it`s key?

[Kedas]

Escape velocity is the velocity needed to escape the gravity.
But we are talking about throwing a stone.
an engine that compensates the grafity force during travel has notting to do with escape velocity.

I don't think the helium balloon is giving us enough height gain and you will still have to launch but this time under worse conditions.

[YT2095]

so this escape velocity`s all about initial velocity needed to break Earth gravity perpendicular to it`s pull. so trowing a stone up in the air at this speed and will get into orbit?
but if it`s a powered craft (fuel permitting) you COULD get into orbit at any speed eventualy?
hope I`ve got this right :)

[blike]

YT2095 said in post #1 (http://www.scienceforums.net/forums/showthread.php?s=&postid=20850#post20850):
can anyone here explain to me what escape velocity is all about? and why it needs to be so fast?

To me I can`t picture any problem in my head about a vehicle going upwards at any speed slow or fast that would eventualy get into orbit, even if it were just at 1 mile an hour (ignoring fuel problems).

There isn't a problem with that scene. Theoretically, you could fire a rocket or whatnot that travelled at a constant speed of 1 MPH and eventually it would escape the earths gravity. (note, I say earth, but escape velocity applies to every body with mass)

Escape velocity describes the velocity at which a rockets engines could be SHUT DOWN, and the rocket would still escape earth's gravity.

As regards to your second question; like Mr_L said, I would imagine its much more expensive. Imagine the size of the balloon needed to carry a massive satellite or space telescope. Not only the telescope, but then the rocket it is attached to. Not only that, but they don't have control of the balloon's flight path as much as they do a rocket, that thats not good. Also, a massive balloon would be in the sky a long time and very sensetive materials could be exposed to the elements. Imagine the hubble space telescope being batted about in a thunderstorm cloud :l

It could possible be cheaper I suppose, just not very practical..

[blike]

Yea, what kedas said.

[YT2095]

I think I`m begining to get the picture a bit, any object that effectively hits this speed will continue going until it leaves our gravity pull. but if powered then it`s not a problem at any speed barring fuel costs and practicality.
So these high altitude spy planes that almost skim on the edge of space, if they reached maximun height, then went nose up and fired a missile, could THAT get into orbit?
then it`s simply a case of removing the warhead and putting equiptment in there instead. I should Imagine some of these huge 1000 lb bunker buster or cruise jobs could do it? maybe take up solar panels or food or something usefull? :)
I can see how the ballon idea would be impractical now, the wake from the rocket leaving would also make a mess :(

[JaKiri]

It takes more fuel for a launching mechanism to

a. Travel to that height.

b. Travel ALONG a long way.

The distance is much greater, and the engines that conventional planes have are much less efficient than the ones used in rocketry.

[JaKiri]

Look at it this way.

If there was a substantially cheaper way, that maintains standards, to put stuff in orbit, NASA would probably have been using it.

They don't use rockets just because they're pretty.

[YT2095]

Isn`t that a bit like saying "if there were a substantialy cheaper way to get from A to B we`de all do it" yet not many folks run economical cars?
I think they`re stuck in a rut due to cold war politics and now underfunding to boot, that it`s going to be very difficult and take alot of time to come up with newer methods!
and if they always thought the way you mentioned, we`de still be all lit by gas mantles and oil lanterns.

[JaKiri]

Not a valid comparison, if the car industries offerered more economic cars, and the infrastructure was in place to run them, people more likely would.

In addition, your explanation of 'Cold War politics' and 'underfunding' is also invalid, because ALL THE OTHER GROUPS use rockets as well.

[Giles]

If the main consideration for consumers was efficiency, then the comparison would be valid, but more usually its "whatever is easiest in the short term".

[YT2095]

yup! sounds about right! :)

[YT2095]

OK, I found this, http://www.physlink.com/Education/AskExperts/ae158.cfm
seemed to say to me that if I can shift an object at 7 miles per sec, I`ll get it into orbit :)
now if something has a DV of 9000 meters p/s (easily acheivable) that would be roughly about 7 miles per sec? or am I a bit off here?
because if I`m right!, you could send objects up all day long for pocket money (nothing usefull because the initial velocity would destroy it) but certainly ball bearings and stuff!

[atinymonkey]

If your looking for the alternative to rockets into space, look into the space elevator.

http://flightprojects.msfc.nasa.gov/fd02_elev.html

http://www.space.com/businesstechnology/technology/space_elevator_020327-1.html

Once built (for a hidiously large amount of money) you could get payloads into space for a couple of thousand pounds.

Plus, it looks cool. :-p

[NavajoEverclear]

I was going ask if that was really possible, but i guess the 2nd article says it is. Of coarse then again media are often complete fools. Doesn't seem like it would work, but if it does it'll be radical

[JaKiri]

It could work perfectly well, it's just you need, say, nanotubes.

[fafalone]

This entire discussion is flawed as you can never escape the Earth's gravity.

[Kedas]

fafalone said in post #19 (http://www.scienceforums.net/forums/showthread.php?s=&postid=21009#post21009):
This entire discussion is flawed as you can never escape the Earth's gravity.

That is true we should actually say escape from earth with constantly increasing distance.
but it isn't practical:
because the earth isn't the only gravitational pull it is very likely that that rock will sooner or later be trapped in orbit around another object.

[JaKiri]

fafalone said in post #19 (http://www.scienceforums.net/forums/showthread.php?s=&postid=21009#post21009):
This entire discussion is flawed as you can never escape the Earth's gravity.

No it isn't, all you have to do (assuming there's no other matter in the universe and no resistive forces) is give it the same KE as current GPE and watch it fly away forever.

[YT2095]

Wouldn`t this tethered cable into space for the lift idea just become one huge lightening conductor? and maybe even cause an ionic/electrical casscade that would be almost impossible to stop? certainly if done at a either of the magnetic poles.
because the Earth and Ionosphere works like a huge capacitor constantly being charged by friction and solar particles (a bit like the silk cloth rubber over an amber sphere).
maybe a neat way to generate electricy perhaps though? :)