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paul Offline OP
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the below notes contain the specs needed.
my answers are as follows.


1) what would be the escape velocity/speed of a vehicle
that is leaving earth and traveling into outer space?

A1: any vertical velocity / speed above zero.

2) how much force would the vehicle first need to accelerate
itself vertically off of the ground?

A2: a force greater than 1 kilogram force.

3) how much extra force above the required lift off
force would the vehicle need to acquire a vertical
acceleration of 1 meter per second per second?

A3: None.

4) as the vehicle achieves vertical acceleration and as the vehicle gets further away from the earth and thus further away from the pull of the earths gravity wouldn't the vehicles vertical velocity and vertical acceleration increase due to the increased distance from the center of the earths mass if
the vehicle is propelling itself with the same amount of
force that it used for lift off?

A4: Yes.

notes:

a) the mass of the vehicle is 1 kilogram.

b) there is no fuel , the vehicle can provide a
constant force for propulsion and so propels itself.

c) the vehicle has stabilization equipment to keep the
vehicle in a vertical posture.

d) and of course taking into consideration that
building such a vehicle is possible. smile

e) the vehicle can only lift off the ground and travel vertically not horizontally.

f) and assuming there is no air or downward wind resistance.

https://en.wikipedia.org/wiki/Escape_velocity



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In general your summary is correct. I have a few comments. Generally the definition of 'escape velocity' is the required unaccelerated initial speed required to escape into space and not return. That would be something like firing a cannon vertically. You use suggests a constant acceleration. In that case any acceleration greater than the force of gravity at the surface of the Earth will allow escape. That is what I think you mean when you say "any vertical velocity / speed above zero".

For your second point you can generalize it to say 'any force greater than the mass of the vehicle'.

For your third point I'm not sure exactly what the value would be.

Your 4th item is a little trickier. My feeling is that you are approximately correct. Again this depends on a constant acceleration drive, which doesn't expend mass from the vehicle. That is the problem with today's space vehicles. We have to expend huge amounts of energy to achieve the acceleration required to get to space. But we have to start with full fuel tanks, and that fuel has to be accelerated too. Most of the fuel used to launch a space vehicle is used just to lift the fuel.

As far as a purely vertical takeoff is concerned we don't do it because the real world doesn't work according to our simplified models and we have to work with what we have.

Bill Gill


C is not the speed of light in a vacuum.
C is the universal speed limit.
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paul Offline OP
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Your mostly correct , but there are issues that need picking.
ie...
Quote:
In general your summary is correct. I have a
few comments. Generally the definition of 'escape velocity' is
the required unaccelerated initial speed required to escape
into space and not return.


escape velocity would send the vehicle away from the earth
and at the same time once the vehicle stopped accelerating
away from the earth the vehicle would then begin to gradually
decelerate due to the gravitational attraction between the
vehicle and the earth until the vehicle comes to a stop
and at that time the vehicle would begin to accelerate towards
the earth or towards the largest gravitation field that it
is attracted to.

Quote:
For your second point you can generalize it to
say 'any force greater than the mass of the vehicle'.


true , because the mass is only 1 kilogram on the earth , so
in generalizing it you are correct as the any force
above 1 kilogram force would not stand correct on a planet
with a stronger or a weaker gravitational field.

Quote:
For your third point I'm not sure exactly
what the value would be.


the constant verticle acceleration of the vehicle
with a force greater than the mass of the vehicle would
give the vehicle constant acceleration , there is no
exact value here as any value of force can always be lowered which
in turn lenghtens the time required to lift off.

Quote:
Your 4th item is a little trickier. My feeling is that
you are approximately correct. Again this depends on a constant
acceleration drive, which doesn't expend mass from the vehicle.
That is the problem with today's space vehicles. We have to expend
huge amounts of energy to achieve the acceleration required to get
to space. But we have to start with full fuel tanks, and that fuel
has to be accelerated too. Most of the fuel used to launch a space
vehicle is used just to lift the fuel.


all true except the approximately correct part because I did
include in the specs that the vehicle supplies its own propulsion
and the vehicle has a mass of 1 kilogram.

but I should have also noted that the vehicle does not throw mass
away from the vehicle in order to achieve propulsion.

and with the common laymans type of rocket propulsion systems
that are still currently used I can understand how it would be
easy to think that my answer might be incorrect even though it
was not.

Quote:
As far as a purely vertical takeoff is concerned we don't do it
because the real world doesn't work according to our simplified models
and we have to work with what we have.


a more correct statement would be that we dont do it because of the tools
that we are allowed to use to accomplish a goal due to economic and political
reasons.


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Originally Posted By: Paul
escape velocity would send the vehicle away from the earth
and at the same time once the vehicle stopped accelerating
away from the earth the vehicle would then begin to gradually
decelerate due to the gravitational attraction between the
vehicle and the earth until the vehicle comes to a stop
and at that time the vehicle would begin to accelerate towards
the earth or towards the largest gravitation field that it
is attracted to.

Escape velocity is defined as the velocity that a mass must have to escape completely from a planet's gravitational field. It is the speed that the mass must have with no further acceleration, other than the gravitational attraction between the planet and mass. It is, as I said above, like being shot out of a cannon. There is one impulse, then it just coasts. Your system would reach escape velocity at some point above the Earths surface. Just how far would depend on the actual acceleration of the vehicle. Once it had reached that velocity then it would keep on gaining velocity as long as the vehicle's propulsion system continued to operate.
Originally Posted By: Paul
all true except the approximately correct part because I did
include in the specs that the vehicle supplies its own propulsion
and the vehicle has a mass of 1 kilogram.

but I should have also noted that the vehicle does not throw mass
away from the vehicle in order to achieve propulsion.

The reason I said approximately is that I didn't stop to do a calculation, so I can't be sure that you are completely correct. You are correct that you said the vehicle was under constant acceleration and I understood that it did not expend any mass in maintaining that acceleration. What changes then is the net acceleration, that is the sum of the acceleration down provided by the Earth's gravitational field and the acceleration upward provided by the vehicles propulsion system. I added the rest about modern rockets because I just wanted to be complete.

Bill Gill


C is not the speed of light in a vacuum.
C is the universal speed limit.
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paul Offline OP
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escape velocity is a term that is a misnomer ie ..
from the escape velocity wiki page I linked to

Quote:
The term escape velocity is actually a misnomer


and here is a quote from the misnomer wiki page.

https://en.wikipedia.org/wiki/Misnomer

Quote:
A misnomer is a word or term that suggests a meaning that is known to be wrong. Misnomers often arise because the thing named received its name long before its true nature was known. A misnomer may also be simply a word that is used incorrectly or misleadingly


the gravity from any body in space/the universe will be felt by all other bodies in space / the universe.

the vehicle will slow to a stop and then accelerate back towards the earth.
unless other gravity fields become involved.

think of it this way.

if the initial force applied to achieve enough
inertia to vertically propel the vehicle were a mere
1.001 kgf then the vehicles vertical acceleration would
be the result of a mere .001 kgf due to the 1 kg downward
force of gravity.

a=F/m

(a) .001 = (F) .001/(m) 1

so its acceleration would be a mere 0.001 mps^2 as it
left the surface of the earth and headed into space.

and the vehicles vertical acceleration would constantly increase
due only to the decreasing force of gravity felt by the vehicle and the constant vertical propulsion
force of 1.001 kgf.

so the vehicle would not be traveling very fast as it
entered into low gravity above the earth.

I haven't calculated the vehicle speed at this point but
at this point the propulsion could be shut down and
the vehicle would slow to a stop due to the attraction of
gravity between the earth and the vehicle and then begin accelerating towards the earth due to the attraction of gravity between the earth and the vehicle.

so its all pretty much like you said below , in fact
this is exactly what I would expect to happen myself.

Quote:
What changes then is the net acceleration, that is the sum of the acceleration down provided by the Earth's gravitational field and the acceleration upward provided by the vehicles propulsion system.


the propulsion goes to zero and the gravity is constant
so the vehicle slows to a stop and then accelerates toward
the earth.

you would pretty much need a computer program to calculate
the different elements involved in slices of time as
would be needed to get much further in the discussion.

I just keep hearing the term "escape velocity" being
misrepresented on tv and movies as if an object needs
only to gain a specific speed in order to leave the earths atmosphere and head into space.

ie .. a set speed which is not correct.


heres an example of a free fall from 128,000 feet above
surface.

notice the acceleration as soon as he leaves the platform.













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Originally Posted By: Paul
escape velocity is a term that is a misnomer ie ..
from the escape velocity wiki page I linked to

That is correct in the sense that the term escape velocity is generally used to refer to what it would take to get completely away from the planets surface. This of course would vary depending on the mass of the 'planet'. They talk sometimes about the escape velocity of a comet. That is low enough that you could get away just by jumping. I think it can be a useful measure, but it does have to be used with care. If you were in a balloon at extreme altitude, like the man in the video, the escape velocity would be slightly lower than from the surface. Not much, because even that height isn't much further, relatively, from the center of the Earth than the surface is.

Escape velocity of course also includes the provision that the projectile's velocity with respect to the Earth would never fall to 0. And of course it is talking about a simplified system that contains only the Earth and the projectile. Other gravity fields will have a large effect on the actual velocity of the projectile.

Originally Posted By: Paul
you would pretty much need a computer program to calculate
the different elements involved in slices of time as
would be needed to get much further in the discussion.

All you need is calculus and it can be done by hand. It isn't always easy, but it can be done.

If you have a long enough acceleration period then you can achieve escape velocity. Your 1.001 kgF would do the job if it kept up long enough. And of course the escape velocity would be getting lower as the vehicle got higher.

And of course escape velocity implies a single impulse like being shot from a cannon. The only proposal that I have ever heard of that approximates that is a mass driver (rail gun) that would throw things into space from a high mountain. Not very practical for anything that is at all delicate, like people.

Bill Gill


C is not the speed of light in a vacuum.
C is the universal speed limit.
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paul Offline OP
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I was talking about using the elements involved in a
computer program to give the precise predictions of
the entire process in slices of time.

you could use calculus to get an approximate prediction
of a single slice but you would need to perform a single
calculation for each slice of time and that could take years
to perform if you wanted the entire process sliced up into
slices that are each 1000th of a second to achieve a precission set of calculations.

I would not use calculus , I would use standard math code
to build the program and fully rely on the preciseness
of classical physics math to deliver a precise prediction
that could be analyzed in depth.

all because the propulsion force vs resistance will
undergo a constant change which will result in a
constant difference in the
acceleration thus the vertical velocity
of the vehicle.

but you could get somewhat of a close proximity guess
using a single calculation using calculus if that is
all you wanted.

and if using a computer program you could adjust the
1.001 kgf down as you get further away from the earths center
as the resistance decreases to achieve a constant velocity
of say .001 mps vertical velocity or lower.

which is why I get upset when I watch a tv show or a movie
that says things like escape velocity must be 40,000 mps
or what ever they use when I know that its wrong.


















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Now lets make you think can you escape the earth with an acceleration of 0.001 mps^2 in all directions and at all times?

Hint: Something happens at a point on your escape that will cause a definite problem with some directions at this speed smile

Problem 2: Does the Earth accelerate/decelerate during its path around the sun? Earth's orbit has an eccentricity of 0.0167.

Last edited by Orac; 12/20/15 04:10 PM.

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paul Offline OP
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I already know the answer !!!

you simply pop a vehicle into existence for each direction
needed , and adjust the speed as needed , and if any unforseen
problems pop up ! you simply invent a new word and blame
it on the new word and then you build a complete volume of bookshelf fillers to accompany the finding ? of the new word.

and form a group of people to believe in the new word.


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I see youve added a new problem.

it doesnt matter , the distance between the earths center
and the vehicle is all that matters.

the earths orbit would not affect the motion of the vehicle.

also: read the notes!!!

Quote:

c) the vehicle has stabilization equipment to keep the
vehicle in a vertical posture.

e) the vehicle can only lift off the ground and travel vertically not horizontally.


the vehicle would inherit all of the momentum from the
earth , this momentum would stay with the vehicle as
it lifts off and travels vertically.

so @ 16.66 minutes into the flight traveling at a
speed of 0.001 mps the vehicle would have reached
an altitude of 1 meter.

since the vehicle is within the earths gravitational field
the vehicle will be pulled along with the earth as the
earth rotates on its axis.

so @ 16.66 minutes into the flight the vehicle will be
directly above the spot where it lifted off from.















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Orac is bringing up some questions that plague actual launches where the aim is to get into a particular orbit. The general idea of escape velocity includes a number of simplifying assumptions. Your idea also contains a number of simplifying assumptions. You have addressed some of them such as only going vertical. In one of your later ones you actually mention some other problems such as air drag. But for the simple solution that you have discussed those are mostly ignorable. Just getting away from the Earth can be done as you say, with a very small acceleration, as long as it is greater than the Earth's gravitational attraction, which of course does vary with height. A small acceleration maintained over a long period of time is just as good as a large acceleration for a short period of time. In a real world situation where somebody is trying to launch something such as a satellite that won't work very well. There is no good way to achieve the very low acceleration over a long period of time.

Bill Gill


C is not the speed of light in a vacuum.
C is the universal speed limit.
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Quote:
In a real world situation where somebody is trying to launch something such as a satellite


this could easily be a real world situation , we have already seen that a balloon can lift a considerable payload to 128,000 feet.

you have mentioned a rail gun.

we know that high velocities are not needed to acquire a
low earth orbit where the majority of satellites are
placed.

connect the dots.

use several balloons to lift a rail gun that accelerates
a satellite payload into the 7.8 km/s LOE.

millions are saved each launch because the balloon / rail gun launch platforms are reuseable which is the main cost involved
in a satellite launch which converts into billions as the
platforms are reused multiple times.

it would basically be a zero fuel cost launch because
the gasses used to inflate the balloons can be pumped into
cylinders and reused in latter launches.

and the rail gun could be solar powered by a solar cell
array placed on the exterior of the balloons and
charge up a capacitance bank to feed electricity to
the rail gun = no heavy batteries!

look at a cell phone , its really tiny , it can perform
the same task as the old multi story computers that filled
several floors of buildings did in the 1950s ...

but were stuck in the 50's with the propulsion systems that we use today.

Quote:
that won't work very well. There is no good way to achieve the very low acceleration over a long period of time.


well maybe not the 0.001 mps but that was just a easily
calculated and easily discussable example without complicating
the issue.

I think it could be done , even to resupply the ISS , among other things such as cleaning up the space junk.

rail gun
https://en.wikipedia.org/wiki/Railgun

Quote:
railguns can potentially exceed Mach 10


10 x the speed of sound , and that is with all the air
resistance on the earths surface.

https://en.wikipedia.org/wiki/Speed_of_sound

Quote:
the speed of sound is 343.2 metres per second (1,126 ft/s). This is 1,236 kilometres per hour (768 mph; 667 kn), or a kilometre in 2.914 s


mach 10 = 3.4 km/s with atmospheric air as the medium

with hardly no resistance to movement at 128,000 ft
from air and only the resistance of gravitational
forces acting on the payload the 7.8 km/s needed for
LOE should or might be obtainable.

if not then a small rocket to assist the railgun perhaps.

still I think it should be doable.


































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Well, a balloon lifted rail gun might have some engineering difficulties to overcome. The first thing that comes to mind is stability. To launch a payload into orbit you have to have very fine control of the trajectory. Launching from a rail gun would mean the trajectory would be primarily ballistic. A ballistic launch really needs to be very precisely positioned to be able to hit the correct orbit. I don't say it couldn't be done, but it would be tricky. The rail guns I have seen discussed would be ground based, so the location would be known exactly.

The next is energy. Rail guns are power hungry. The power requirement for a rail launch might be only 10%* of the power for a rocket launch, but it comes in one big burst. That would mean some kind of high power storage device that could be discharged quickly. Many systems that use power bursts use capacitor storage, but storing that much in capacitors might be problematical. An example of a system that uses capacitor storage for a brief burst in an electronic camera flash. Any way that again might be possible, but it too would be tricky.

And did I mention that a rail gun would be long? I would expect it to be something on the order of a kilometer long. Once again the engineering to get that lifted and stabilized would be tricky.

So it might be possible, but there would definitely be some serious engineering challenges.

And I forgot to mention acceleration. Manned space flights use lower acceleration launches than unmanned flights, because people can't take the acceleration that machines can. Even then unmanned payloads will still have to be able to take the acceleration of a launch system that has all of its acceleration in 1 Km. Current launch systems have main stages that run for at least a couple of minutes, which takes them a lot further than 1 Km. So acceleration for a rail gun would probably be much higher. This could produce problems for payload designers.

* 10% is an approximate value, based on the mass ratios of current launch vehicle to payload weights. I'm certainly not going to stick my neck out and say it would be much lower than that.

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Originally Posted By: Bill
You have addressed some of them such as only going vertical.

Vertical to what?

The Earths axis tilts at 23 degree, I guess you might mean vertical to the earths surface in a Geostationary orbit which give you a rather strange motion to the earth orbit around the sun.



I am not sure what Paul is really trying to work with but if we are talking vertical to earths surface then you may be better googling "Space Elevator" which is a much more exact discussion of a vertical movement to earths surface.

Even with all that if you extend it too far the relativistic time effects may become significant as the higher you go the faster your instantaneous rotational velocity.

I don't get what he was trying to work out and you guys seem to switching between ridiculously small forces and rail guns. Then the rail gun is fired in mid air and it doesn't recoil back towards earth or topple over etc and hence I don't really get where Paul is going with this, which is sort of your comment above.

Last edited by Orac; 12/21/15 08:44 AM.

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I haven't figured out where Paul is coming from with his idea, but I am trying to address just what he is saying. With the simplifying assumption that his vehicle is taking off vertical to the ground from which it is launched and ignoring all the different motions involved it would work pretty much the way he says. Allowing for the Earth's rotation the vehicle would not stay above the point at which it was launched, but it would generally work the way he says. Now there are a lot of complications to actually doing that, but with a the simplifications used in a lot of thought experiments it works pretty good. The real world has a lot of stuff that will throw him completely out, but I am ignoring those, just the way he is.

He mentioned something about the use of escape velocity in TV and movies. Maybe he just doesn't like the way that the entertainment industry messes with reality in their shows. I realize that a lot of them really get a long way from reality in their so called science.

Bill Gill


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a 1 km long rail should not be too long to design.
or too heavy to lift.

in fact the 1 km long rail could be stored in a box
and as lifted the rail would unfold itself and align
itself one section at a time.

made from either titanium , carbon fiber or the new really strong but lightweight metals formed with bubbles inside them to reduce weight as explained on the sagg homepage.
and the rail weight would only be a matter of the number of lifting balloons used.

so proper design of the rail and lifting balloons
should overcome any obstacles as to strength , length or weight.

as for the recoil , an opposing counterbalancing dummy
satellite could be launched simultaneously in the opposite direction , this would remove the recoil.

as far as the rotation of the earth is concerned , small ion thrusters could be used to stabilize the overall launch
platform to counteract not only the earths rotation but
also the winds that are encountered.

the ion thrusters could also be used to align the satellite into its proper orbital insertion angle of attack itself
after it launches vertically from the platform.

Im sure that any obstacles that may arise other than economic or political obstacles could be easily worked out if allowed.

all they need to do is just do it.
everything is in place already , and theres really no reason why satellites need to be so large , and if they do then the
satellites can be made to assemble themselves together in
blocks after launch.

heck , the first satellite can be a programmed worker droid
or an rov that assembles the satellites when they arrive in space.

this can all be done today , we just have to start and we
have to stop being so negative and teaching our children
things that have no value such as the escape velocity we
hear or see on tv or at the movies.



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Paul, you seem to think that engineering the system you have described would be simple. I would like to point out that it would be a major engineering task. Even if we could build it with off the shelf components it would take a large design team several years. As most of it would not be off the shelf it would probably take 10 to 20 years just to design it. You can't just sit down and whip up a design overnight. It has to be done in steps with construction of proof of concept intermediates. We are undoubtedly talking about billions of dollars invested in a questionable enterprise.

And using a 1 Km rail gun does require extremely high G forces on the payloads. No humans could be launched using the system.

Bill Gill


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I dont know the exact amount of electricity required
to accelerate a 1 kilogram payload using a rail gun.
else I would have that part figured out by now.

and to design a rail gun that will launch a large
payload you would need to know how much electricity
would be needed.

I do know that it will require electricity.

(35) 100 Watt solar panels can supply 3.5 kW
of electricity to charge up a capicitor bank
every hour.

4 hours of charging and the capicitor bank will
have a built up charge of 14,000 Watt hours.

according to the rail gun wiki page
the US Navy rail guns require 5-50 MW to
launch.

50 MW = apx 14000 Watt Hours.

50 MW can deliver 1 WAtt for 14000 hours
or
it can last for a few seconds in a rail gun.


so the electricity should be no problem.

way back in the 1940's the united states
developed and tested and deployed nuclear weapons.

there was alot more involved in the research and
development of a nuclear bomb than any balloon
launch system might ever dream of having associated
with it.

the nuclear bombs went from theory to practice in
less than 6 years.

and that was in the 1940's this isnt even the same
century... there should be no problem with the
design process or any other process as there are
no new or unknown processes involved.

and I havent mentioned launching a human being
using a rail gun , I did mention launching satellites
and resupplying the ISS and cleaning up the space junk
but that is all.







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OK , Im going to use the "for comparison" in the quote
below from the wiki rail gun page.

Quote:
Therefore, typical military railgun designs aim
for muzzle velocities in the range of 2000–3500 m/s
with muzzle energies of 5–50 MJ.

For comparison, 50MJ is equivalent to the kinetic energy of a
school bus weighing 5 metric tons, travelling at 509 km/h (316 mph).


1 metric ton = 1000 kg

5 tons @ 509 km/h = 141.38 m/s

1 ton @ 2545 km/h = 706.94 m/s
((509,000 m/h * 5 )/ 3600 seconds)

1 kg @ 295,000 km/h = 706,944.44 m/s
((509,000 m/h * 5000 )/ 3600 seconds)

so the 50 MJ/MW electricity could propel my
1 kg payload to a velocity of over 700 km/second !

LOE is from 91 km to 2000 km ...
looks like the 1 kg payload will need to apply
brakes of some sorts to stay in LOE.

because in 3 seconds it will be at a altitude
of over 2100 km ... plus the 128,000 ft it started with.

I know that would probably vaporise the rails among other
things so lets scale it down a bit...

so lets go with a 1 ton satellite , should hit apx 91 km
in around 128 seconds or 2000 km in apx 47 minutes.

and the satellites can attach themselves to each other
to form larger ones if needed by worker droids or rov
worker satellites.

still havent lost the issue yet I dont think.





3/4 inch of dust build up on the moon in 4.527 billion years,LOL and QM is fantasy science.
Joined: May 2011
Posts: 2,819
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Joined: May 2011
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The projectile in a rail gun at that speed will become a ball of plasma smile

I think what you are more thinking of is a "Mass Driver" google it, which is like a rail gun but a lot friendlier on the payload. Usually it is done by coils which act as a linear accelerator.

Is StarTram (https://en.wikipedia.org/wiki/StarTram) sort of what you are suggesting?

Last edited by Orac; 12/23/15 12:20 AM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
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