what is the Mechanical energy required to run a Space craft and why it so?
605786
When a spacecraft is in orbit it needs no energy. That's the simple answer. However, you need to get it into orbit in the first place, and this means accelerating the object to the speed it needs to orbit the earth - around 18,000 mph. How much energy you need then depends on the mass of the object or spacecraft - this can be calculated from 1/2 mv^2. \n\nTo escape the earths gravity altogether the spacecraft needs to go faster, about 25,000 mph or 7 miles per second. So if you were going to Mars for example, once you achieve that speed you need no more energy.
105320
It takes a lot of energy to break out of Earth orbit, and thus takes a lot of fuel.  Just to get to the moon, it took a giant, 3 stage, Saturn V rocket.\n\nThe space shuttle was specifically designed to be used in Earth orbit and thus could not carry near enough fuel to escape Earth's gravitational pull.
580216
The first step is to figure out how much Δv it takes to reach the space station's orbit (and make sure you add a decent reserve on top of it just in case the unexpected happens).  For a station in Earth orbit something higher than 9 km/s seems reasonable, less for lower inclination orbits.\n\nOnce you've got that you then need the exhaust velocity of your rocket, it would depend on what you are using but you can get some rough values from the first source.\n\nWith that the mass ratio is the exhaust velocity times the natural log (ln key on scientific calculators) of the Δv.\n\nThe mass ratio is the difference between the starting and ending mass of the rocket so the amount of fuel will be the (mass ratio minus one) times the mass of the rocket structure + payload.\n\nYou'll probably get something absurdly large (it's very hard to exceed 10 in the real world) and if so then you've got to use staging which makes it a lot more complicated.\n\nThe Soyuz FG which launches the Soyuz and Progress spacecraft to the ISS has about 280 tonnes of propellant at launch over all three stages for a spacecraft lighter than 8 tonnes.  Of course the Soyuz FG uses LOX/Kerosene, more efficient propellants like LOX/H2 would need less propellant for the same payload but it isn't going to be an order of magnitude reduction.
315403
You would generate a ship capable of providing a mini-ecosystem capable of sustaining a self-replicating crew.  Astronauts have kids who become astronauts down the ages until the destination is reached.  \n\nAs far as drive mechanism, currently NASA is working on finalizing an ION drive that gets stuff to its destination faster than our current thruster tech by propelling them at an increasing rate of acceleration.
616877
All engines have a cost.  I suggest that the cost of this form of energy may be the slowing of the rotational period of the Earth.  What would we pay in time
487670
None. It takes no power to maintain that speed (on level ground, no friction). The object has kinetic energy (0.5 * m * v^2). Power was required to put it in motion and power can be recovered by decelerating it. If you do the math, the energy is 3551.86 ft-lb, equivalent to 1 horsepower for 6.458 seconds. Answer 1 neglected the fact that weight must be converted to mass by dividing by g, and energy is proportional to v^2.
915957
The energy from the sun that plants use to make their food and to create oxygen..\n\nGravity keeps you from flying off into space.  Come to think of it, keeps the atmosphere from flying off into space.\n\nThe force that keep atomic particles together and not fly into indifidual directions, keeping YOU to gether.
1098506
Well, you can find many web sites on spacecraft design, try that.  But, I can respond to one point.  A good spaceship will be a structure designed to be assembled in high orbit, and will not enter any atmosphere.  All of the structures necessary for high gravity atmospheric travel are useless dead mass when it come to space travel.  We are not quite to this point, but getting closer.  Check out the current Mission to Mars plans at the NASA website.  Three different launch vehicles.  That is the first step, how to get things into space efficiently.  If we get better at that, we will see more ambitious construction projects, like a permanent moon base, or a high orbit space station.
59906
because we have the technology to do it, so why wouldnt't we do it? i am myself a physics major and i know for a fact that it is possible. it is not really as hard as you think. you just design a rocket(which isnt much harder than designing a plane) and it just needs a lot of fuel and energy to surpass the escape velocity put forth by the earth's gravitational field, and it just has to be made of a sturdy material with a high melting point so it doesn't melt. once you're in outer space, it does not require much fuel to navigate, and all you have to do is get it to the moon and land... and as far as people being inside, yeah, just add oxygen and reserves of compressed oxygen to make those levels stable(just like they do in airplanes).\n\nalso, i know plenty of engineering majors. NASA offers internships, NASA recruits a hell of a lot of engineers and rocket designers and has way too many rocket designs for none of them to work... also, you can go to a rocket launching and see any of the rockets take off...\n\nbesides from being a physics major and thus knowing that we are actually capable of the technology- also, what reason would they have for making it up? there is really no benefit to it.. just to say "haha, look, we did it"... obviously we are using too many billions of dollars and such on space equipment and programs and rockets(which anyone can go see on tours at NASA). we wouldnt spend that much money on what? to have a nice big laugh at NASA? "haha, we fooled everyone!" come on now...
70887
they can't.  That would be a perpetual motion machine.  \nConservation of energy says that you can't get something for nothing.  for a terrestrial body to do work continuously it would need to be given a continuous supply of energy.\n\nIn an elliptical orbit, two boddies can take turns doing work on each other and energy is conserved.
768384
because a car turns heat energy into mechanical energy
513866
That importance is incalculable (without the aid of a computer!). Spacecraft and mission design, vehicle navigation, guidance, control and flight simulation need intense mathematical work that can only be performed by computers. There are just too many complex interactions among all aspects of a space mission for any number of unaided humans to keep in mind.
512134
A. First, do a quick magnitude check to see if you can use Newtonian physics or need to use special relativity. Your Newtonian velocity would be \nv = at \n  = 1g x seconds in a year  \n  = 10m/s x 3.15x10^7 seconds \n  = 3.15x10^8 m/s.\nwhich is greater than the speed of light (= 2.99x10^8 m/s), so you do need to use relativity.\n\nThe relativistic equation for velocity after constant acceleration is (source 1):\n v = c tanh(aT/c)\nusing aT from above, \n v = c tanh(3.15x10^8 / 2.99x10^8)\n   = 0.78c\n   = 2.34 x 10^8 m/s\n\nB. Now that you have v, use the special relativity energy equation to calculate your energy (see source 3)\nE = (gamma) x mc^2\n(gamma) = 1/sqrt(1- v^2/c^2)\n(gamma) = 1.61\nE = 1.61mc^2\n\nThis energy includes the rest mass, mc^2, which we don't need to add (it was there before we started), so the kinetic energy is\nKe = 0.61mc^2\n   = 5.48x10^19 Joules\nOf course, no propulsion systems are 100% efficient, so it would take more energy than this.  Rockets, in particular, are very inefficient, and would take many orders of magnitude more energy.\n\nC.  Nothing we have even comes close. For comparison, this is about 100 times the entire world's energy production in 2002.
272490
Structures in space are built the old-fashioned way with cranes, hand tools, portable electric tools, etc.  What you're talking about is so expensive and so far in the future it's only in people's dreams right now, like landing on the moon was a hundred years ago.
174378
It does, and at the same time, it doesnt, it depends on the situation.\n\nIf you were to take a rocket out so far away from any gravitaitonal fields that they were insignificant and remove any of type of friction/forces acting on the space craft, then it wouldnt need a rocket to continue moving due to Newtons 1st law of motion (inertia).\n\nHowever, in any real, practical, situation, a space craft does need a rocket to keep moving, eventually.\nTake this example.  If you had a space craft in space at the edge of the Earth's atmosphere so that air resistance was negliglible and fire the rockets off initially to start moving but then shut them down.....eventually, then rocket would come to a stop.  This would happen because of Earth's gravitational pull on the rocket, just because something is in space doesnt mean there is no gravity. Gravity acts as the unbalanced force to slow/stop/reverse the space craft, if the rockets arent fired to counter act this, the craft will eventually fall back to Earth.\nThere is a special case to this example, however.  If the space craft were to originally lauch at the escape velocity for Earth, it would never fall back down as that is defined as the minimum velocity needed to escape the Earth's gravitaitonal pull forever, bu this still isnt to say that the craft wont slow down as Earth continues to exert a force on it.\n\nIn space, as with everywhere else in the universe, an object will only maintain a constant velocity if the net force acting on the object is zero.  If there is any force acting on the object (be it due to gravity, friction, whatever), there will be some acceleration which will cause a change in velocity with respect to time.
167518
The energy of a satellite orbit is constant, energy defined as the sum of potential energy and kintetic energy (E = PE + KE).\n\nIn a circular orbit, both altitude and velocity are constant.  This means that the potential energy (PE) and the kintetic energy (KE) of the orbit are both constant, so there is no change in either potential energy or kinetic energy.\n\nIn an elliptical orbit, the satellite is constantly changing it's altitude, resulting in a transfer between KE and PE, even though total energy stays constant.  \n\nWork is defined as the difference between PE (or KE) at different points in the orbit.  Since the PE and KE are constantly changing, there is always work being done on a satellite in orbit.
18018
Solar Sails are a very interesting technology that could be used for future space exploration, but currently face serious engineering issues to be able to do this.  \n\nFuture manned and robotic space exploration outside of our solar system could currently be considered a pipe dream.  Solar Sails, along with fusion motors, Bussard ramjets, antimatter drives, and Von Neumann machines are the various technologies being research as possible ways to further our manned and robotic exploration of space outside of our own solar system.\n\nAs far as the speed for a Solar Sail, most Solar Sail proposals would provide thrust for the craft with a very large laser. The actual speed of the craft would depend on the size of the craft and the size of the laser used, and the amount of time the laser would be able to provide thrust for the craft.