Mathcad Community Challenge May 2025 - Spin Gravity!

[DaveMartin]

This month’s challenge is based on spin gravity and emphasizes creativity!

Spin gravity is a method of creating the sense of gravity in a low- or zero- gravity environment using rotational movement. During this circular motion, objects with mass feel a fictitious centrifugal force “pushing” them away from the center. This force can feel like the gravity we experience on Earth.

You can either design your own space station / vehicle or choose one (or more) from science fiction books, television shows, movies, video games, or other media. Then create a Mathcad worksheet to calculate the following:

• Radius of your spinning object.
• Centrifugal acceleration in both distance units per second squared and g’s (acceleration due to gravity at the earth’s surface). Note that your vehicle / station does not need to be 1g. Less than 1g makes it easier to move. More than 1g would help improve your jump shot on your eventual return to Earth.
• Angular velocity in radians, degrees, and revolutions per time unit. Don’t spin too fast, or you will make people feel sick!
• Tangential velocity.

Examples from popular media include:

• Books: Ringworld, Rendezvous with Rama, The Expanse series, The Culture series, The Moon is a Harsh Mistress, and The Forever War.
• Video games: Halo, Prey, and Kerbal Space Program.
• Television shows: Babylon 5, The Expanse, and For All Mankind.
• Film: 2001: A Space Odyssey, Interstellar, The Martian, Elysium, Mission to Mars, and Zeta Gundam.

In “real” science, O’Neill Cylinders were proposed by Professor Gerard K. O’Neill in 1974. Maybe you can design your own or a variation.

Note that if you create your worksheet in Mathcad Prime 11, you can use a custom unit system in your worksheet! This can be extremely helpful depending on how big you want your station or vehicle to be.

Bonus Advanced Input Controls Challenge

Incorporate Combo Boxes, Sliders, Check Boxes, Radio Buttons, or any other input controls to allow users to change a parameter to see how it affects other calculations.

Bonus Graphing Challenge

Use XY Plots, 3D Plots, Contour Plots, or Chart Components to depict the acceleration due to gravity as a function of one or more other parameters for a space station / vehicle.

Have fun with this!

Find the Mathcad Community Challenge Guidelines here!

[Fred_Kohlhepp]

I'm a little surprised that we're eleven days into May and there have been no posts!

Attached (in Express Prime 4) is a simple discussion of the challenges of spin gravity, disguised as a design for a small space station.:

• A reminder of NASA's error in Explorer 1  about stability of spinning objects.
• A calculation of the pressure in a column of fluid and the effects of centrifugal acceleration
• A reminder that things thrown "in a straight line" in a rotating frame of reference do not travel in a straight line.

Enjoy!  Comment!  Expand!

[ttokoro]

Prime 11. Ver. 1a. T.Tokoro.

[DaveMartin]

I decided to get in on the fun. Here is my worksheet in Mathcad Prime 11. This is a work in progress. I still need to throw in an optimization and take advantage of custom unit systems, especially for RPMs.

[DJNewman]

I adore your gravity / radius sliders and the motion sickness conditionally formatted text box!

[DaveMartin]

I've updated my worksheet to take advantage of a couple Prime 11 enhancements:

• I am using a custom unit system so that the default unit for frequency is RPM instead of Hertz.
• I duplicated the text box with conditional formatting to be written in Python in addition to JScript.

[DJNewman]

I think you've made the first example I've seen out "in the wild" of making a different box for a Python scripted control. This is a best practice for a few reasons.

1. For a general audience like "everyone who browses the Mathcad Community", you don't know if they have Python installed; if you only had a Python box, I don't think it'd work if Python wasn't installed. (JScript is installed by default with your Windows system, by comparison.) If you were sharing a worksheet among your own company or a client and you know that having Python installed is standard, this wouldn't be an issue.
2. It needs to be a different box because each control can only "save" the current scripting language it's in. If you took the JScript box, changed the language in the drop-down to Python, and wrote out the Python script and clicked apply and closed it, Mathcad Prime would not save the contents of the JScript box anymore and that'll be lost. So... I hope people don't do that because they'll end up pretty upset...

[Werner_E]

I agree that providing an alternative for a Python scripted component in case the user has not installed Python is a good idea - actually I would call it mandatory!

If Python isn't installed an appropriate error message should be thrown rather than just showing the state of the box when it was saved the lasts time because the current behavior could lead to erroneous conclusions.

Prime not saving all scripts of a scripted component is really bad behaviour.

I would almost call this a bug, or at least a very serious design error.
Instead of warning users, R&D should quickly go over it again and change the behavior of scripted components so that ALL scripts are saved, regardless of which scripting language is currently set as the active one.

In a next step a mechanism could be implemented that Prime autodetects if Python is installed and automatically switches over to the JScript (or even VBScript) code (if available) in case Python is not installed. That way having to create and maintain two separate boxes could be avoided.

[DJNewman]

I agree with everything you wrote, and I think it would be helpful for (convincing) R&D for someone to submit this as a feature request and have people vote it up.

[DaveMartin]

Honestly, duplicating the scripted control was a "happy accident." I was just trying to see if I could do the same text box in Python that I had done in JScript. I hadn't even considered someone not having Python on their computer - despite downloading and installing it on my main computer just last week.

I'm glad to have stumbled upon a "best practice" nonetheless. 🤓

[ttokoro]

Prime 11. Ver. 2a. T.Tokoro.

[DJNewman]

Having the spinning object turn red (even more red than your screenshot) is very fun!

[ttokoro]

Prime 11. Ver. 3a. T.Tokoro.

[ppal]

[DJNewman]

Well, you're late... but your worksheet is cool, so I'll allow it anyway. 😀