0
$\begingroup$

Thinking of a future world with immense buildings and massive cities. Instead of large trains, people travel on "elevators" - pods travelling on a maglev-type system.

Each pod can hold about 15-20 people, and can go sideways as well as up and down.

I know a train can do something like 500kph, but this is a smaller pod, run on electricity supplied by to the elevator.

The pods travel through tubes, and occasionally have to wait at junctions. The entire system is automated.

Once on board, the pod cannot be stopped by the passengers (safety systems do exist - the point is that the passengers aren't in control).

The pod in my story is an express elevator. Start to end, no stopping.

In theory, how far could one of these pods travel in a 2 to 3 hour period?

Edit: Assume that the tubes are similar to city roads. Sometimes they merge, sometimes you have to turn off one & onto another. The system is automated in order to minimise travel time, but other traffic has to be considered.

For acceleration and stopping, in this case the customers do wear seatbelt/harness things (again, automated), but they don't have any Star Trek-type inertial dampers to prevent people being turned into paint if one of these things takes off too fast. (This is actually a bit of a plot point - someone causes a pod to accelerate to like mach 6 in the space of a few seconds, then slams on the brakes, killing everyone in the pod.)

With this question, I'm mostly getting an idea for an average commute.

Improve this question
$\endgroup$
10
  • $\begingroup$ As I understand the question, you are talking about elevator-car-sized "maglev cars" that travel both horizontal and vertical. $\endgroup$
    – o.m.
    Commented Jan 23, 2017 at 6:01
  • $\begingroup$ Are the passengers standing or seated? $\endgroup$
    – Separatrix
    Commented Jan 23, 2017 at 9:20
  • $\begingroup$ If you streamilne your elevator like a maglev train, you may go as fast as the coefficient of friction allows you to: all things being equal, a maglev train will go almost as fast as a maglev pod: they endure almost the same air resistance. The acceleration & deceleration will be a limiting factor for human endurance, so it depends how far you are going: Up a tower, there's no need to reach such speed. $\endgroup$
    – Mikey
    Commented Jan 23, 2017 at 11:41
  • $\begingroup$ What now, Express elevator or stopping at junctions? That'll change the answer by an order of magnitude! $\endgroup$
    – Karl
    Commented Jan 23, 2017 at 19:19
  • 1
    $\begingroup$ Why would there be junctions to stop at? We are talking small things, ever hear of a bridge? One goes over another, the paths should never meet. $\endgroup$
    – Loren Pechtel
    Commented Jan 23, 2017 at 22:22

5 Answers 5

Reset to default
4
$\begingroup$

Warning: This is a wild guess without hard numbers:

As per my comment, I'm assuming that you are talking about elevator-car-sized "maglev cars" that travel both horizontal and vertical.

  • Using external power is normal for maglev designs. This could be induction power rather than contact power.
  • The frontal area of your "little trains" will be almost as large as those of a "big train" -- say 1/2 or 1/3, when the total volume is 1/50 or thereabouts.
  • There will be a cube or square in the power-to-speed formula, so it probably won't be quite as bad the previous bullet point suggests.
  • Maglev has been around for decades, but it hasn't been developed much. Consider how fast aircraft were two decades after the Wright brothers, and how fast they are now.

With all those points in mind, I'd guess a top speed of 500 to 800 kph would be possible if the highest possible speed was a design goal. But there are other issues:

  • Are people standing or are they sitting? How much acceleration can they stand before people spill their coffee or break legs? I'd guess 1-2 m/s^2 are OK. That means the car could take 2-3 minutes and 10 km to reach top speed.
  • What is the possible turning radius at this speed?

With these restrictions in mind, twice as far as a present-day car sounds right. 100 to 200 kph in urban areas, 200 to 400 kph on long straight stretches.

Improve this answer
$\endgroup$
4
  • $\begingroup$ Not even that in urban zones, the tubes might eliminate dogs in the road but you still need to move slowly enough to corner and stop comfortably at every junction. I'd say max 150kph, rarely above 80kph. I say this from a European perspective where I laugh at the concept of a straight line in an urban area and the whole thing is an urban area. $\endgroup$
    – Separatrix
    Commented Jan 23, 2017 at 10:00
  • $\begingroup$ @Separatrix, 150 is right between 100 and 200. I won't quibble over 25%, you might well be right. $\endgroup$
    – o.m.
    Commented Jan 23, 2017 at 16:31
  • $\begingroup$ IMHO you could go 200kph in an urban zone with junctions -- By avoiding junctions. Cloverleaf tubes! $\endgroup$
    – SIGSTACKFAULT
    Commented Jan 23, 2017 at 16:54
  • $\begingroup$ The energy to power ratio could be much greater than a maglev because a la hyperloop, you could reduce or eliminate air resistance by removing air from the tubes. The initial proposed hyperloop line in Bahrain is supposed to go 99 mies in 12 minutes, which is 600 mph (1000 km) and 1200 miles (2000 km) in two hours. Even if stops at junctions and turns slowed that up a great deal, something like 1000 km ought to be feasible with not very much more advanced than current technology. Building structures that big would be far more challenging than building elevators that fast. $\endgroup$
    – ohwilleke
    Commented Jan 24, 2017 at 11:35
3
$\begingroup$

Let me name a few assumptions before attempting an answer:
1. The elevator starts from rest, and comes to rest at its destination.
2. Power source is not an issue - there is as much power needed as required to bring the elevator to whatever speed is desired.
3. The human passengers are expected to reach their destination alive and in good health.
4. The elevator travels in a perfect straight line, with zero air resistance/ friction.

I'd say that the maximum range in 2 hours of this elevator depends on how quickly one can accelerate the elevator without killing off its human occupants. A quick Wikipedia search suggests that 6G for 10 minutes is survivable, but that limit has to decrease if time of exposure is lengthened.

For a 2-hour journey, the elevator should spend the first hour accelerating as much as possible, and the remaining hour decelerating to a complete rest. Let's say that protective technology allows for constant acceleration of 4G for this entire hour.

Applying basic physics, the distance travelled in this hour should be approx. 260,000km. A further 260,000km is travelled in the process of coming to rest, so I'd say the elevator has covered slightly more than half a million kilometers in 2 hours - enough to visit the Moon and be well on its way back!

Improve this answer
$\endgroup$
1
  • $\begingroup$ +1, but you should limit deceleration (during the travel up) to 0.8g. This would let passengers feel 0.2g and keep standing on the floor. Of course, doesn't really matter half way to the moon. $\endgroup$
    – Mołot
    Commented Jan 23, 2017 at 16:58
2
$\begingroup$

Wikipedia entry on the hyperloop (which this question basically is asking about) expects an average speed of 970km/h. https://en.m.wikipedia.org/wiki/Hyperloop So in 3 hours, that's 2910 kilometers.

Improve this answer
$\endgroup$
1
  • $\begingroup$ I did not understand this to be in a vacuum. OP can you address whether your concept is in a vacuum? $\endgroup$
    – Mikey
    Commented Jan 23, 2017 at 11:42
2
$\begingroup$

It really depends on what level of acceleration you're comfortable with.

$$distance = 0.5*acceleration*time^2$$

So assuming you spend half the time accelerating and half decelerating then in 3 hours you could travel a maximum of ~29'000km times acceleration in m/s (or ~gees/10). So 1g (well, +1g for 1.5hrs and -1g for 1.5hrs) will get you around 290'000km (and a peak speed of 53km/sec - enough to leave Earth well and truly behind) while 0.01g will get you 2900km (and a top speed of ~2000kph).

This of course says nothing about comfort, power consumption, (sonic booms, escape velocity) etc.

Improve this answer
$\endgroup$
0
$\begingroup$

The pod would probably have to stay subsonic unless you are using vaccum tubes.

So let s say they can go up to current planes speed, that woudl be at most 2000-3000 km in 2-3hours.

Improve this answer
$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .