Reactionless (sex) drive

Thought that title might get some attention. ;)

On another group, the subject of sex in zero-G has come
up, as it does from time to time. There were the usual
predictions that the couple would have difficulty
"getting it together" in Space, and that if they did,
that they would bounce off of the walls like popcorn.
It was suggested that only the use of bondage gear
could solve these problems.

I disagree. I suspect that the solution to all of this
perceived difficulty is really quite simple: hold on to
your lover. But this was met with statements that,
with all the wiggling and thrusting and rubbing going
on, they will still set themselves zinging around, no
matter how much they hold on to each other.

I disagree even more strongly. It seems to me that
this objection is based off of a complete
misunderstanding of how action/reaction works. So I
wrote the following to explain things. However, I
thought that, just to make sure I don't end up making a
fool of myself, I'd run it past the more knowledgeable
people here first. Actually, I seem to do quite a bit
of that, and I hope that the more knowledgeable people
don't get sick of it. Let me know if you do.

So here it is:

>> Ah, but you also have the problem of literrally
>> bouncing off the walls, furniture, etc.

> Which is why bondage is going to be the answer to at
> least some of those problems,

One way of dealing with the problem, and probably a
popular one. It would even be possible to zip a couple
of people into a sleeping bag, itself attached to a bed
or padded wall/floor. Unless...

> unless you plan on sex in a padded room.

A perfectly acceptable solution.

> If one of the partners is held down by ropes or other
> restraints to a wall,

Do you mean "If one of the partners is NOT held
down...?"

> ceiling or floor, no matter how well the partners
> cling to each other, they will fly around the room as
> passion takes them. F=Ma, and all that Newtonian
> physics,

There is truth to this. However, keep in mind that if
John is pushing against Mary, then Mary is pushing
against John. Let's assume that they are in a cube-
shaped room, and we will call the six surfaces north,
south, west, east, up, and down. These designations
would be entirely arbitrary, of course (what's "up" and
what's "down" would be a matter of consensus, rather
than of physical reality).

Now, if John and Mary are hovering in the center of
this cube (we'll assume 5*5*5 metres) and John shoves
Mary west, then what happens is that Mary heads west
while John heads east. If John is more massive than
Mary (a statistical likelihood), then Mary moves more
quickly and reaches the west wall before John reaches
the east wall. Each has the same energy, the same
momentum; it's just divided up differently between
speed and mass. And since each has the same momentum
*in the opposite direction,* the total momentum is zero.

Thus, if John shoves Mary west, *and they hold on to
each other,* then more-massive John moving slower in one
direction cancels less-massive Mary moving faster in the
opposite direction. They can't, as a unit, go anywhere.
They can move as far as the length of their arms, or
legs, or long flaxen hair, or whatever it is that they
are holding on to. If they are in a tight embrace, they
don't really go anywhere. To have them remain in
contact and yet start heading off in any direction, or
change direction, or speed up or slow down, would
constitute a reactionless drive. It would be like
replacing a spacecraft's rockets with chunks of lead and
a robotic arm that waves them around. Your spacecraft
will wiggle, but it won't go anywhere.

Now of course, it is possible that John and Mary don't
start their love-making hovering in the middle of this
cube. They might start in contact with, say, the down
wall (floor?). In the course of their passions, they
could well push against this wall and send themselves
drifting across the room. This is not reactionless
because they are pushing off against the much more
massive love nest (which is itself probably part of a
very massive space hotel or even a gargantuanly massive
O'Neill habitat). So in that sense, yes, they can go
bouncing around the (hopefully padded) love nest, or
could use restraints to hold themselves in place (thus
leading to a whole new industry: Space Bondage Porn).

But then, how fast are they likely to set themselves
moving, just bumping against the wall? Slowly drifting
seems much more likely than frantic zinging. My guess
is that to have them bouncing around like a 3-D billiard
game, they'd have to do it on purpose.