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One day, humans will have a permanent presence on the moon. Right? One day it will happen. So, how are we going to live on the moon? And perhaps a more important question – how are we moving there? In preparation for our lunar colony, let me look at three movements we could make on the moon: jump, run and turn.
Let me note that this analysis is inspired by the recent novel by Andy Weir Artemis I will not spoil the plot, except to say that there is a girl moving on the moon. Weir does a very good job in describing what would be different when moving on the moon compared to the Earth.
What is different about the moon compared to the earth? The biggest difference is the gravitational field on the surface. On Earth, the field has a force of 9.8 Newtons per kilogram (we use the symbol g for that). This means that an object falling freely (without air resistance) would have an acceleration down to 9.8 m / s 2 . On the moon, the gravitational field is about 1.6 N / kg, so that the vertical acceleration of a moon-object would be much lower than that of the Earth.
There is another important difference with the moon: it does not have all the air. If you are a jumping human, it may not be a big problem; a human jumping to Earth does not move fast enough for air resistance to play a significant role. However, on the moon, this same human would probably want to wear a spacesuit. This combination would increase both the effective mass and decrease the range of motion for a moving human. Oh, if there is a moon base, there will probably be air inside, so you do not have to wear any spacesuit unless you do not have think it looks cool.
Jumping on the moon
will begin with the easiest movement jump. Let's say that during a normal human jump, a human pushes on the ground with maximum force for a certain distance. This distance is from the lowest position in the pre-jump squat, until the feet are no longer in contact with the ground.
Now for some starting values (you can change them if you want). I will say that this maximum jump force is three times the weight of the person (the weight on Earth) and the jump distance is 15 centimeters – that's just a guess. With these values, I can not model the movement of a human jumping on Earth. I'm just going to calculate the total force either as the pushing up force and gravity while "touching" with the ground or just after gravity. It should be a fairly simple numerical calculation.
For a human jumping on the moon, I'll make some changes. Obviously, the gravitational field will change, but also other things. I will assume that the human wears a space suit, so that will increase the total mass (but not the maximum jump force). In addition, as a diving suit is bulky, the jump distance will also be smaller. OK, let's go. Here are two jumpers (moon and earth). If you want the code for this calculation, go
Here's what it would look like (using spherical humans for simplicity).
Also, here is a plot of the vertical position of the two jumpers. [19659010] Some things to notice. First, the land jumper starts with a faster speed. Why? Because the moon jumper has more mass (space suit and others). Secondly, the lunar jumper goes higher and stays longer because of the weaker vertical acceleration.
But wait! How about a real video of a moon jump? Here is a video of John Young's famous "salute jump" on the Apollo 16 mission.
Quite cool – but without a spacesuit, a human could probably jump even higher. Here is an old NASA movie of a human jumping into the simulated gravity of the moon. NASA's (very creative) method of simulating the gravity of the moon is to have the human suspended mainly horizontally by ropes, then to move on a predominantly vertical surface
Running on the moon
The first scenes of the book Artemis has the main character (Jazz) on the surface of the moon. For some reason (read the book), she starts running fast enough in her spacesuit. So what would it be to run on the moon?
Yes, there are videos of astronauts who are moving in a way that could be considered "running" – but I still want to model this motion. I've already built a current human model and now I can just change a few tricks to adapt to the moon. Here is my previous post on a human model running. Some key points of this model (remember, it's just a model)
- A human is like a ball bouncing off the ground. It consists of two parts: the contact with the ground and the movement in the air.
- The part where the human is not in contact with the ground should last a minimum of time so that the human can pass from front to back.
- During contact with the ground, the human can exercise only a maximum force
- The time of contact with the ground decreases with the speed of linear movement
All this means that when the runner moves faster, A greater component of the pushing force must be applied in the vertical direction to lift the human from the ground, since the contact time decreases. Eventually, the human reaches a maximum speed where all the force is used in the vertical direction. You can check my model operation code here.
But what about running on the moon? The big difference is time. Since the gravitational field is small, the human will be in the air much longer with a smaller vertical push force. This means that more than the maximum force can be used in the horizontal direction to increase the horizontal speed.
OK, but what about a plot? Here is my race model on both the Earth and the Moon. I've increased the mass of the moon-human to simulate a space suit and I've also increased the "stride time" of man on the ground to account for a suit bulky which would require more time of swaying legs.
the speed as a function of time for these two runners
The Earth-Human reaches a speed of nearly 10 m / s, but the human-moon can easily exceed 15 m / s. But wait! It's even better. It's suppose the same kind of racing style for both gravitational fields. However, on the moon, it is very possible that there are more efficient running styles that take advantage of the weak gravitational field.
It is probably not very surprising that people have already explored the idea of running in low gravity. Take a look at this NASA test using the same "horizontal" platform as in the jump video.
Oh, there is also this interesting article on the theoretical and simulated velocities of the moon. the actual lunar gravity, "from the Journal of Experimental Biology.For this study, they put real humans on treadmills in an airplane flying in parabolic paths to create a lower apparent weight.But really, who knows how it will really work until we are serious about the moon.
Running and Turning
Running in a straight line could be fun for a short time, but if you really want to maneuver around you are going to have to turn to at a given moment, would turning on the moon be different from the one on Earth, of course, consider a human running in a circle on the surface of the Earth, here is a view from above and from the side with a diagram of force
The key idea here is that you need a "lateral" force to take a turn.The direction of this rotational force is towards the center of the circle in which you are turning. the amplitude of This force depends on the running speed and the size of the circle in the following manner.
a larger force and a smaller radius (sharper turn) also means greater strength. The force that pushes the human in a circular path is the friction force between the feet and the ground. But, of course, you already know that if you try to make a turn with low friction ice, it does not work as well, is not it?
Here is the last important point: the frictional force is proportional to the force that the soil pushes until on the human. In the case of maximum friction, the amplitude would be:
But what about the moon? What changes? The first thing is the gravitational force. With a lower gravitational force on the moon, there will also be a lower ground force that grows on the human. This of course means that there will be a lower friction force used to turn. Oh, add to that the fact that the human could run faster and you get a big turning problem.
So running on the moon will be different from running on the Earth. I'm a little excited to see what cool stuff we can find to move in this lower gravity environment. Oh, being on the moon would be so cool.
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