Limits Of Magnetic Acceleration Tubes

[darthgently]

5 minutes ago, kerbiloid said:

We may build a 7.9 km/s vacuum tunnel at 100+ km altitude. It's called orbit.

Known advantages: doesn't need walls, doesn't need magnets.

Stop making sense! 

[CFYL]

On 5/21/2022 at 2:29 AM, kerbiloid said:

We may build a 7.9 km/s vacuum tunnel at 100+ km altitude. It's called orbit.

Known advantages: doesn't need walls, doesn't need magnets.

We may put train station on the ground. It's called space center.

We may effectively accelerate the train with reaction engines fueled by UDMH+NTO or whatever. It's called rocket.

We may effectively deccelerate the train with aero forces. It's called reentry.

We may put the train to a complete stop by making ground contact. It's called landing.

Known DISadvantages: Oh you need something as heavy as an aircraft carrier that FLIES to get the heavy train in orbit.

 

ON THE GROUND a conventional carriage weighs ~20t and carries ~100 passengers.

Effective mass per passenger is 0.06(passenger+luggage)+0.2(carriage average)=0.26t. I don't care about insulation in vacuum. I DON'T CARE.

An SLS gets 70t(manned)/130t(freight) payload to orbit. So the train carries at most 269 passengers. That's way too costly. If you go suborbital and just reenter the atmosphere at the right point, you may get more.

 

A vacuum tube on the ground "may" help you, somehow, get the train to the natural tunnel called orbit. We can replace reaction engines that fly with magnets that lie on the ground for easy maintenance.

[kerbiloid]

23 minutes ago, CFYL said:

A vacuum tube on the ground

There is a reason, why the railways are mostly not subways.

[CFYL]

What about this? I drew these pictures with PaintDotNet.

We build circular vacuum tubes ~1000km in diameter near densly populated cities. We link cities to the large circle with shorter tubes. We put airpumps and power plants near those tubes. We can also cover the tubes with solar panels. Intercity travel can be done through these tubes----There's no need of making a "web" with vacuum tubes because they are fast enough. Just link every city to a "freeway" and make trains run on the freeway. A travel route can be: cityA → train station → freeway → train station → cityB.

The circular vacuum tube can be used as "freeway" as well as ground acceleration tubes. That can be two separate tubes placed close together -- one for suborbital, one for intercity. For the suborbital trains, we guide them to a slope tube. The slope tube is built on a geologically stable mountain to link the ground tube to 3-4km altitude. The "ground tube" in the following graph refers to the circular tube in the prior one. 

With these "two sets of tubes", we can manage distances within a few thousand kilometers, as well as beyond that. Accelerating to 3000m/s at 1g only requires ~5minutes. The suborbital flight can take passengers far away. A travel route can be: cityA on continent A → train station → circular tube → slope tube → suborbital flight → reentry → powered landing → cityB on continent B. (typo: powerede should be powered)

I drew some circles on the map to show a few possible "circular tubes". As long as they don't go through deep, harsh seas, it should be fine. The acceleration tubes can give the train some 3km/s launch speed, so ΔV requirements of the train itself is trivial.

Safety can be a problem though.

[Nightside]

On 5/17/2022 at 4:13 AM, farmerben said:

If we bore directly through the center of the planet, we don't need maglev.  Gravity will accelerate us and slow us down.  It takes about 43 minutes to transit the diameter of the Earth with it's gravity.  If we take some off center chord line it takes the same amount of time, assuming no friction.  

On an internally dead body like the Moon or Mars tunneling through the center is a viable possibility, travel times vary depending on the planet.

Probably still pretty radioactive down there though, no?