Speed, Lift & Gravity on the Moon.

[Swank]

(10 min mark). First I thought I had seen this in Space 1999, then in Joe 90, turns out it's Capt. Scarlet.

What are we looking at? Have we been talking about hopping devices?

I remember a short story about a foot race around the moon. The competitors hopped like kangaroos, traveling 50 yards at a time.

 

[msstice]

What are we looking at? Have we been talking about hopping devices?

We are now. @ckatt 's original post brought up the interesting idea of how we're gonna do high speed car chases on the moon (Brad Pitt already did that in Ad Astra and it wasn't convincing). I especially like the note that all we have to do is hit a small bump and off we go into orbit (well, in a rather slow high arc).

If we wanted to persist in using wheels we'd probably have to have RCS jets on the craft. More likely we'd have something like what NASA is contracting Intuitive machines to do: https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=PRIME-1

Also: https://ntrs.nasa.gov/api/citations/19730007490/downloads/19730007490.pdf

TIL: Also proposed for other missions:

Triton Hopper - Wikipedia

en.wikipedia.org

Mars Geyser Hopper - Wikipedia

en.wikipedia.org

 

[ckatt]

I like this. Seems like it would be efficient. Though, I wonder how exciting it would be to watch these things in a race. Even if they were faster, I think the up and down motion would sap some of the tension out of it. You wouldn't have two cars neck and neck vying for the lead.
It would still be entertaining but kind of niche I think. Not a big round pleaser like F1 which I am trying to imagine a successor to.

 

[msstice]

I like this. Seems like it would be efficient. Though, I wonder how exciting it would be to watch these things in a race. Even if they were faster, I think the up and down motion would sap some of the tension out of it. You wouldn't have two cars neck and neck vying for the lead.
It would still be entertaining but kind of niche I think. Not a big round pleaser like F1 which I am trying to imagine a successor to.

I suppose if the Loonies got bored and needed a racing setup to bet on, Star Wars type pod racing would be an option. The setup would be a race through canyons (Rille - Wikipedia) and caves with the stipulation that no one could rise above a certain height.

 

[msstice]

PS. I thought the lunar rover in Emmerlich's "Moonfall" was well done. It had RCS thrusters.

 

[JimC]

"on a planet where mass & weight are the same".

They aren't the same thing at all.

 

[Swank]

"on a planet where mass & weight are the same".

They aren't the same thing at all.

They are the same units here, which is what the context of that quote was.

 

[Astro Pen]

Daytime temperatures near the lunar equator reach a boiling 250 degrees Fahrenheit (120° C, 400 K), while nighttime temperatures get to a chilly -208 degrees Fahrenheit (-130° C, 140 K). The Moon's poles are even colder.
(source us government)
Average is about minus 23 degrees centigrade though the cycles are long, rendering that a not particularly helpful bit of information.

(I know this because @msstice raised the issue with me elsewhere and I had to do some research )

 

[JimC]

"They are the same units here, which is what the context of that quote was."

From the latitude on the Earth's surface where weight and mass are numerically equal, move either north or south. They will no longer be equal. Two different things.

 

[Swank]

"They are the same units here, which is what the context of that quote was."

From the latitude on the Earth's surface where weight and mass are numerically equal, move either north or south. They will no longer be equal. Two different things.

The full quote is:

All of my experience with vehicles has been on a planet where mass & weight are the same.

Which I read as saying "in my vestibular experience, I have only dealt with operating vehicles that have the usual earth relationship between gravity and inertia."

You seem to be suggesting that he is wrong, because the fraction of a percent variation in earth gravity by location means that the there is variation in that relationship. But you are ignoring the fact that human beings' vestibular systems aren't accurate enough to detect and experience fractions of a percent variation in weight, so his experience is essentially uniform anywhere on earth. We are not able to tell a difference, and I doubt even a difference of several whole percent would be detectable by a person.

So maybe he should have said "essentially the same" to ward off pedants, but his statement was not about physics but what a person can experience.

 

[JimC]

Sure looks like a statement about physics

 

[Cthulhu.Science]

From the latitude on the Earth's surface where weight and mass are numerically equal, move either north or south. They will no longer be equal. Two different things.

Your statement fascinates me. I'm thinking about the show "Ice Road Truckers."

Is the gravitational difference so extreme that if someone learned to drive Tractor-Trailers on ice roads in lower latitudes and then took a job driving trucks on ice roads above the arctic circle, the driver would immediately recognize the difference in gravity?

I chose that example since the mass/weight difference would be greatest for that type of vehicle and the friction (ice roads) would be lowest.

What would that driver's experience be like with a big truck in lower gravity?
That must be true of all vehicles on all roads, not just Ice roads. Every driver that drove at/near the equator for many years moving far north or south. Or Vice-Versa. Do Swedes (or other people) who live far to the north (or south) experience the gravitational difference when driving on vacation close to the equator? Tell us more about that!!!


Now this is going wayyyy back to last February, but for my part, in my original post I was attempting to describe my thoughts on what the human experience would be like rather than provide a mathematical description. Since this is a fiction writers' blog I thought comments on the human experience was an interesting add to the discussion.

 

[JimC]

"Do Swedes (or other people) who live far to the north (or south) experience the gravitational difference when driving on vacation close to the equator?".

Yes, they may not perceive it, but they experience it.

 

[Swank]

"Do Swedes (or other people) who live far to the north (or south) experience the gravitational difference when driving on vacation close to the equator?".

Yes, they may not perceive it, but they experience it.

And the pedantic award goes to:

 

[JimC]

And thank goodness for that