How fast would a Martian space elevator travel?
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I am writing a passage about the main character of my book travelling up a space elevator to the spaceport that rests in geostationary orbit above Mars. This means that the elevator would have to travel roughly 17,000 km [previously wrote 20,400 km] from ground to station. I'm trying to figure out how fast to make the elevator car travel in order to determine how long it will take, but my math is concerning me so I thought I would turn to you my fellow worldbuilders for help. I am having trouble finding information on the maximum G-forces a person can stand comfortably. I need this so that I know my maximum acceleration. So first question:
What is the maximum G-forces someone can stand COMFORTABLY?
I use the term "comfortably" loosely, as I mainly mean tolerable for long periods of time.
What I did find is that maglev trains accelerate up to about 0.5 Gs (I am imagining a sort of maglev elevator). This means that if I am remember my kinematic equations correctly, (and not fudging it up because its almost 1 AM here and I'm tired) I should be able to make the trip in about 110 hours with a continuous acceleration to halfway and then deceleration the rest of the way. Meaning I would make the trip in roughly 4.5 days, which isn't ideal. I would appreciate if someone could check my math, although it might be correct since I did find an article stating the same thing on Earth might take around 7.5 days.
Is it reasonable to assume this is the fastest method of space elevator travel?
I'm open to suggestions on design changes, but would like to clarify that there is no artificial gravity tech.
Further background for clarification: This is suppose to take place roughly 400 years from now, however technology has probably only advanced 100-150 years give or take due to the destruction of Earth around 2100 AD, leaving Mars as the new center of human life. Computer science slowed with the end of Moore's law, but jumped up again with early quantum computing. Medical science has advanced to counteract most of the negative affects of living in low G through strict exercise regiments and medication to promote bone and muscle development. Materials science has made a few leaps to allow for the issues with maximum speed or just building a space elevator in the first place.
Edit: Previously had written Mars geostationary orbit as 20,400 km instead of 17,000 km. The reason for confusion is that the previous number was the distance from Mars' center of mass, not the Martian surface. That said, my calculations were definitely wrong since they used the first number.
Edit: My calculations were way off because I forgot to convert 0.5 G back to 4.9 m/s^2, so I just used 0.5 and got way wrong numbers.
This post was sourced from https://worldbuilding.stackexchange.com/q/121430. It is licensed under CC BY-SA 4.0.
1 answer
What is the maximum G-forces someone can stand COMFORTABLY?
I posit that in order for someone to experience comfort that they must remain conscious, so the method by which people are transported having been rendered unconscious is out.
I would suggest a G-Suit.
(More accuratley an Anti-G-Suit)
It is designed to prevent a black-out and g-LOC (g-induced loss of consciousness) caused by the blood pooling in the lower part of the body when under acceleration, thus depriving the brain of blood.
A g-suit does not so much increase the g-threshold, but makes it possible to sustain high g longer without excessive physical fatigue. The resting g-tolerance of a typical person is anywhere from 3-5 g depending on the person. A g-suit will typically add 1 g of tolerance to that limit...
So that's 4g acceleration for the average (non-infirm) adult, but...
Comfort.
High g is not comfortable, even with a g-suit.
So, give everybody happy pills. This, from the marketing perspective would have the benefit of generating lots of repeat customers by it's effects:
(it gives) the user feelings of euphoria, intense relaxation, and decreased perception of pain.
Well that (from a marketing department's perspective) sounds comfortable.
Maximum velocity and time.
Just plug 4g into the equations. I'd say somewhere in the order of 17 minutes either way, and roughly 36Km/s at turnaround.
Issues.
We can assume that the problems of maglev at that sort of speed, such as magnetic hysteresis (the time taken to magnetise and de-magnetise a material) - a suitable technique or material to compensate would have been found.
Compensating for the force of wind at low altitudes and the tendency of atmospheric buffeting to de-stabilise the vehicle will all have been resolved by then. Possibly by enclosing the base of the tether and the first 7 Km or so:
The upper stratosphere model is used for altitudes above 7,000 meters. In the upper atmosphere the temperature decreases linearly and the pressure decreases exponentially.
On your suggestion, the whole thing could be enclosed by the tether as an elevator - that would help.
Quick turnaround, happy customers and another plus - you get to market g-suits with your branding on.
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