I asked about this low-G terminal velocity stuff before, as I had this
idea of a 'Jackie Chan on the Moon' thing. The idea was that he would
find himself at the inside top of a huge dome on the Moon. He would
simply let go and fall the 1000 metres to the swimming pool. We all
know that Chan can fall 10 metres and more into water and climb out
wet but unharmed. Thus on the Moon he could easily manage 60 metres.
But a thousand? Well, I was going with the idea that terminal
velocity would only be about 20 MPH on the Moon, so it'd be fine. And
it would look cool.

--- In spacesettlers@yahoogroups.com, "Xenophile"
>
> I asked about this low-G terminal velocity stuff before, as I had
this
> idea of a 'Jackie Chan on the Moon' thing. The idea was that he
would
> find himself at the inside top of a huge dome on the Moon. He would
> simply let go and fall the 1000 metres to the swimming pool. We all
> know that Chan can fall 10 metres and more into water and climb out
> wet but unharmed. Thus on the Moon he could easily manage 60
metres.
> But a thousand? Well, I was going with the idea that terminal
> velocity would only be about 20 MPH on the Moon, so it'd be fine.
And
> it would look cool.
>
> I was told it wouldn't work. Told that terminal velocity is
> determined by the thinkness of the air. So Chan would have to fall
> six times as far to get up to 120 MPH, but he would. So he'd splat.
>
> However, a scene from Arthur C. Clarke's "Rendezvous With Rama"
> suggests that terminal velocity *is* less if gravity is lower.
Clarke
> is a pretty sharp guy, and this sort of thing is, well, his sort of
thing.
>
> So I'm going to ask again. I'm even going to post a link to a post
> about this same sort of thing on a group dedicated to the Barsoom
> stories of Edgar Rice Burroughs. If Rick is wrong, it looks like
> Clarke is too. Of course, Clarke can be wrong, I suppose, but...
>
terminal velocity is the speed at which gravity matches the
resistance of the air to something falling though it. therefore Clark
was right, lower gravity would decrease the tvs. something else that
would also effect this (from sky-jumping class) is how much area is
exposed to the moving air. sky jumpers that spread their bodies out
decrease their speed by as much as a third over those that are in a
nose dive or leg first position. also the lunar dome would decrease
the size of the parachute that jackie would need, down to something
the size of large cape. he would still fall but slow enough that the
water would assorb the last of his fall.

From: Xenophile
To: spacesettlers@yahoogroups.com
Sent: Wednesday, May 24, 2006 3:51:23 PM
Subject: [spacesettlers] Falling in low-G.

At 12:22 PM 5/25/2006, you wrote:
>It has been some time since reading Rama, but Clarke did explain why a
>person could fall a couple hundred meters to water and no die on
>impact. Too bad I don't remember what that explanation was...
>
>Perhaps the reason is that Rama had gravity by inertia, not by mass (like
>Earth and Moon). With angular momentum, accelerating during the fall is
>less an issue than differences in velocity. Therefore, relative
>peripheral speeds dominate landing forces.

On 5/25/06, Matt Gallimore wrote:
(...)
> Perhaps the reason is that Rama had gravity by inertia, not by mass (like Earth and Moon). With angular momentum, accelerating during the fall is less an issue than differences in velocity. Therefore, relative peripheral speeds dominate landing forces.
(...)

Thanks, guys. It looks like if the gravity is low enough and the air
is thick enough, you could fall for thousands of kilometres and land
without injury.

Terminal velocity is also a function of density, or rather drag-to-mass
ratio, and therefore subject to the square-cube law. A mouse can fall
farther than me without injury, because its TV is much lower than a
person's. An ant's TV is so low that it can fall from any height and not
get hurt at all. Just a litte fact to add nothing to the discussion. I'm
sick of lurking.