Vacuum transport: the key to long distance transport?

[bernardd]

basically I say that because for a project to work, it must be successful with the public. If the public asks for windows there will certainly be ... to be seen. Notice that in a tunnel ...

Given the difficulty of design and manufacturing added by windows, and the lack of interest in my opinion, by the speeds reached that the eye cannot physically follow, it is better to put internal screens, on which one can choose what is projected: you don't see anything on an airplane, but you can drop your film. It will only be necessary to add exterior photos, the juxtaposition of which will give a film, as you had the idea :-)

In any case, system monitoring will be facilitated by visible images from the control centers.

[emlaurent]

Not really understood this case of non iso gravity ?? I can see what you mean in relation to a small sphere but ... it doesn't seem too applicable to me on a planet scale ...

Draw a circle, with a straight line that crosses it between 2 points of the circumference :-) Relative to the center, the line goes down first, then goes up afterwards!

It's clearer said like that Bernard! To follow a line of iso gravity is to move on the surface of the earth by following the surface of the terrestrial sphere.

But we must be able to be very hot: we know very little about the interior of the earth, I prefer to avoid ...

Intercontinental transport is planned:
"high tech systems for continental and intercontinental transport up to 4,000 mph or more. For greater detail see technology section." I read 2h for a NewYork-Beijing ...

Very hot? If the tube is partially evacuated, this limits the transport of heat to the interior of the cabin. There remains the conduction transmission by the rails: there may be insulation between rails and cabin.

If I have a moment, I calculate how many km we sink under the surface for a NewYork Pekin!

[Christophe]

It's clearer said like that Bernard! To follow a line of iso gravity is to move on the surface of the earth by following the surface of the terrestrial sphere.

Certainly it is, but you have to dig how many km deep for the technique to start working?

If I have a moment, I calculate how many km we sink under the surface for a NewYork Pekin!

In a straight line ? Too much !!

[chatelot16]

the use of gravity is interesting for short distances: the tunnel begins with a vertiginous descent stile mountain ruus, to gain speed for free ... and ends with an ascent for an equally free deceleraton: the engine is no longer used that to compensate for friction

for long journeys this system is of no interest because the acceleration and braking phases are relatively less important compared to the whole journey

the path at constant speed is horizontal

there is a simple calculation between depth and speed: it is simply the speed of free fall in a vacuum: the potential energy of loss of altitude and transformed into kinetic energy


do some calculation, it would require a huge depth, and the additional cost of such a deep tunnel does not seem justified to me

you will have to be satisfied with an engine which pushes to accelerate, and brakes while trying to recover the maximum at the other end

[Christophe]

the motor is only used to compensate for friction

Uh, isn't that the case with all vehicles?

[bernardd]

the use of gravity is interesting for short distances: the tunnel begins with a vertiginous descent stile mountain ruus, to gain speed for free ... and ends with an ascent for an equally free deceleraton: the engine is no longer used that to compensate for friction

Yes, but I was thinking the other way around:
- we go up at the start, limiting the number of motors to this area,
- and we end up on the slope ... until the next lift.

It exists: it's called the glider, or the roller coaster :-)

And this could very well be done with a vacuum tube, because without the braking of the air, the momentum must be able to bring very far.

The extreme being the space elevator!

[chatelot16]

since the interest of the vacuum is to reduce friction, the power to advance at constant speed will be low, a slope will be useless

it is acceleration and braking which requires a large engine, and that is why some have thought of this acceleration and braking by slope

but I find it useless: the electric motor is good, and with a catenary which allows a good recovery under braking the blow of the slopes is useless

[bernardd]

Not necessarily useful in all configurations. But the advantage is to have motors in only one place:
- less metal to distribute over the entire length,
- less mass in the vehicle,
- better engine utilization rate
- simpler operation and maintenance.

[chatelot16]

yes but calculate the depth it takes to do 500km / h: in my opinion it's ridiculous to dig so deep to save a few kg of electric motor

[bernardd]

I was not talking about digging, but building a tower :-)

Otherwise, 500km / h is 138m / s and it is reached in 14s of vertical fall in a vacuum, that is to say after a fall of about 966m.

We have just found a second use for electricity production towers by thermal ascent ;-)

By the way, if you dig a vertical tube in the ground, how does the gravity constant evolve? It should normally cancel in the middle, right? And it must decrease like the cube of the radius remaining to the center, at constant earth mass density?