Rocket science question .

originally posted by: midnightstar
en.wikipedia.org...
Earths escape velocity = 25,000 ( apx )

Theory is you need to reach this speed to escape earths gravity .
BUT here is my kicker Lets start with this a space elevator ( no humans haven't built one nore likely to Because nothing we can make that long that would hold up .)
But if we did then we could send you to space using it .-----NO escape velocity nessery just louse elevator music for two hours .
So here is my question
Take a type of plane - rocket combo say its going 500 mph UP and has enough fuel to do this for weeks .
Now it WILL keep going up ! So it WILL get into space . But then why all the hubub about escape Vol?
Theory is it has not escaped earths gravity ok ??/ so it keeps flying say to the moon then the moons gravity is stronger so wile it hasn't acutely escaped earths Gravity is is still at the moon and now in the moons gravity It never needed to escape earths gravity just get closer to another body in space with Gravity .
So tell me why this isnt possible because its the one thing i never understood about space travel .
And good luck lol better be a link btw . Not that i have ever found anything to explane this .

Escape velocity is a much misused term. Try think of this. A man has a jet pack and up in the air he goes at say 50mph. Nowhere near escape velocity. If his backpack had enough fuel for several months he would be going past the moon before his fuel ran out.....and maybe his air.......but you get the point. As long as you have thrust and fuel and you are moving away from the earth you just keep on going. There will come a point when you can switch off the thrust and you keep moving in a straight line which all depends on gravity, other bodies etc etc

Correct me if I'm wrong, but doesn't constant thrust in space provide constant acceleration, meaning the spacecraft will go faster and faster? As such, it's doesn't really make sense to talk about a spacecraft or space taveller constantly moving at a certain speed. Firing the rocket engines causes acceleration. Turning the engines off is what makes you travel at a steady speed (ignoring any acceleration by celestial bodies).

a reply to: wildespace

A continuous thrust could also allow a craft to maintain a constant speed away from a gravity well against the force of gravity trying to pull it back/slow it down.


So in some cases, a continuous thrust could be applied in order to remain at a constant forward velocity. As I said in a post above, that relative net velocity could be only 1 mph and still be enough to escape the gravity well.

a reply to: midnightstar



the escape velocity, for the purpose of inserting a satellite or spacecraft into Orbit//

Is the most cost effective minimum... required to put a payload into Low-Earth-Orbit... with the chemical fuel, combustion powered, rocket engines we are capable enough to use...

our technology has not advanced enough to carry some Trillion Tonnes of rocket fuel to accelerate all the way to-the-moon

(still another clunker in thinking is exposed---
Here's why --> in between the Earth & Moon is a certain point in space called the ~Lagrange Point... where Earth Gravity and the Moon Gravity are equal-to-each-other
So, a rocket only needs propulsion to the 'Lagrange point" after which it will slowly coast down to the Moons surface

yes a gravity powered space rocket or a Nuclear generated Ion engine would constantly increase speed as the forward thrust was engaged... but the logistics for such a wasteful use of expensive rocket fuel would be in the $5 Billion per MPH increase of speed with the present liquid or solid fuel rocket technology....


the present system of launching stuff into low-earth-orbit, then continuing the next stage of the mission from space is the lowest cost method available...

Kind of surprised at all the responses to this post .
But yes I understand now its a matter this is our only way as of now .
And agin even if we found better fuel the ship still needs to go as fast as it can .
going to mars isn't like walking down the street to the park . 35 million miles on a good day means speed lots and lots of speed .
This was just a why not thing not a we should do thing .
funny voyager are going around 30 k per hour getting no ware fast .
the galaxy is 120,000 light years accross times that by 5 trillion miles .
Even star trek was a joke ( warp theory light speed squared ) warp 1 light warp 2 8 time and so on .
so at warp 7 they were not getting anywhere fast as well .
What were really need is a star gate or hypergate or some otehr sci movies stuff lol