Lab Ships in Jumpspace?

[scott]

OK, here's one of those really niggling little questions that you know you just need to drop and forget about, but you can't.

If I understand correctly, the Type L lab ship almost always uses rotation to create "gravity," and has only minimal and/or short term gravitics for when rotation (for some reason) can't happen.

Does this mean that the ship is rotating during jump? Is there any reason that can't happen?

 

[far-trader]

As far as I understand it there's no reason it can't rotate in jumpspace, and the effect would be the same, creating an artificial spun gravity.

The way I've read the design the reason for the occasional (not routine) use of spun gravity (probably more likely micro gravity*) is for experiments where the output of the power plant or the effect of the artificial gravity generators would interfere. The probability of such experiments being often enough that the design was built that way. It costs nothing extra to lay it out that way, something similar to designing a ship as a tail lander. Not that the ship has only minimal or short tern gravitics.

* I had worked it out a few times, even bookmarked a link to the calculator...

Ah! There it is

http://www.artificial-gravity.com/sw/SpinCalc/SpinCalc.htm

Now if I had my corrected Lab Ship size handy I could run the numbers again. At least with the link you can run them yourself

Note the comfort range notes though

 

[scott]

The way I've read the design the reason for the occasional (not routine) use of spun gravity (probably more likely micro gravity*) is for experiments where the output of the power plant or the effect of the artificial gravity generators would interfere. .... Not that the ship has only minimal or short tern gravitics.

Aha--that make a lot more sense. Thanks!

Also, it means that I may draw up a non-ring lab ship for the types of expeditions I have in mind.

http://www.artificial-gravity.com/sw/SpinCalc/SpinCalc.htm

Great--that's math beyond my ability (or desire, given that this is recreational).

Note the comfort range notes though

I am blessed with a tendency to motion sickness , so that had already occurred to me.

 

[far-trader]

For what it's worth, either my corrected measures were very much smaller (still haven't found them) or I was thinking of something else re: micro-gravity limits. The CT lab ship with a stated 35m radius can spin up 1G with a little possible discomfort, nothing serious or even certain. I'd say only motion sickness susceptible individuals might be cautioned, but medication would probably treat it easily.

 

[Carlobrand]

Rotational "gravity" makes for some odd effects, no? Things don't quite behave the way you expect. When you drop something, it doesn't fall with increasing velocity as in normal gravity - nor does it appear to fall in a straight line from your point of view. (It falls in a straight line, but you and everything around you are moving in a circle as it does. From your point of view, it appears to be taking an arcing course downward and lands some small distance from where you expect - and a bit slower than you expect.)

That can be rather disconcerting when you're trying to pour milk in your morning cereal - and perhaps disconcerting again once you've adjusted to it and then try to return to normal gravity. Makes for some fun background when roleplaying. Please be most careful when using the fresher.

 

[Icosahedron]

AFAIK, the rate of change of velocity should be the same as normal gravity. However, there will be tidal effects (a gravity difference between your head and your feet) and Coriolis effects that will affect where an object lands. Whether they are noticeable will depend on the diameter of the wheel, the ratio of the diameter to the fall distance, and the speed of rotation.

I've always assumed a tidal effect would be inherent in 'normal' grav plates too - I see no way to avoid it.

As for whether spin gravity would work in Jump space, that depends on the nature of Jump space and the nature of inertia - Mach's Principle in particular.

Next time you're in Jump space, try stirring a cup of tea. If the surface goes concave when you stir it, your rotational gravity should work.

 

[far-trader]

As for whether spin gravity would work in Jump space, that depends on the nature of Jump space and the nature of inertia - Mach's Principle in particular.

I figure the ship being separated from Jump Space itself, in a pocket of protected normal space, that spin gravity should still work the same as in normal space...

...of course there might be a more... 'mechanical' reason for it not working. Or at least not being advisable. Perhaps hulls in motion cause an undesirable translation of motion to the Jump Space over the hull, pulling it closer or even sucking it into the hull. Or something... :devil:

 

[aramis]

AFAIK, the rate of change of velocity should be the same as normal gravity. However, there will be tidal effects (a gravity difference between your head and your feet) and Coriolis effects that will affect where an object lands. Whether they are noticeable will depend on the diameter of the wheel, the ratio of the diameter to the fall distance, and the speed of rotation.

Your downward speed will be pretty much fixed at release unless either you hit a wall (and are thus accelerated spin, which accelerates you out, which continues to increase speed and outward force) or are dragged along by atmospheric forces. Remember, the straight-line velocity at drop is higher the further you are from the center of rotation.

 

[Carlobrand]

Aramis is right. Think of yourself on the lab ship as standing in the cup of a huge sling, or maybe a bucket on a rope, that some uber-giant floating in space is spinning around his head. Your "up" is towards the giant's head. Your "down" is the floor of the sling. Your "gravity" is caused by centripetal acceleration: you're trying to obey Newton's laws and fly straight away from the giant like any good sling bullet, but the floor of the sling is preventing you from doing that.

At the point where you drop something, it is no longer being influenced by the giant or his sling; it is free of all external influences (putting aside the issue of air resistance, for the moment). It flies straight away from him at a constant speed dictated by the factors in play at the instant of release - and no other force is acting on it to accelerate it further. It is governed solely by Newton's laws. Meanwhile, you are still travelling in a circle with that sling.

Conversely, on a planet, the planet would be pulling on the dropped item to make it go faster even as it fell. That's the key difference between gravity and centripetal acceleration used to simulate gravity: gravity is a greedy beast, hungrily drawing you downward whether you're standing or falling, drawing you faster and faster the farther you fall until you go "splat" on something, but for centripetal acceleration, once you'r falling free of the "sling", it no longer "cares" about you - you fall at whatever speed you had at the instant of release, and never faster unless some other force intervenes.

 

[aramis]

Thinking this through, there is a slight issue Carlos is overlooking...

Given two circles, A and B, radii 10 and 30 respectively, and points c and d on A at 0° and 90°, plus matching c' and d' on B at same... if we spin along B (without moving c, c', d, or d'...

Item released from c does not impact at c', nor at d', but at point e' which is 90° from c.
As it approaches B, the potion of its movement which is "downward" increases. It will appear to accelerate, even tho' it doesn't.

But it won't be a natural looking acceleration, either.

If we release it at c with a velocity of 5 per second, it's downward apparent motion is 1.2 in the first second, 3.0 in the second, 3.9 in the 3rd, 4.3 in the 4th, and 4.6 in the 5th.


Drawing done in cadintosh.

 

[Carlobrand]

I am not ashamed to admit I didn't understand any of that.

 

[aramis]

I am not ashamed to admit I didn't understand any of that.

Sorry, stream of consciousness took over.

When the guy drops the item from 10m from hub with a 5m/s tangential velocity (from ~4.7rpm), it "falls" 5m/s, but it doesn't fall towards the floor, per se. It continues in a straight line. The clipped inner circle on the diagram rotates counterclockwise; it flies straight. So, it appears to accelerate, but not evenly.

S _R_ _AA
1 1.2 2.4
2 3.0 3.6
3 3.9 0.9
4 4.3 0.4
5 4.6 0.3
6 4.7 0.1 (KTHUNK)

Column 1 is second count. Column 2 is distance covered that second. Column 3 is apparent acceleration in m/s/s, remembering the D=1/2AT^2... Until it hits, it will continue to appear to accellerate less and less, as it approaches appearing to fall at its initial tangential velocity; it also appears to accelerate antispin as it approaches, but I've NOT accounted for that; it's moving just a bit over 27m... 5.5 seconds... and the target point under will move 15x5.5=82.5m or so... about 315°...

 

[Icosahedron]

Yep, I'm definitely getting even rustier than I was last time I checked.
Don't use the stuff these days.
And whereas once upon a time I would have avidly checked Aramis's figures just for fun and my own edification, I simply can't be bothered any more.
He's right, at least in principle - I had a 'Doh!' moment when I read his reply, but as for the actual figures, my internal couch potato has won out - I'll just take his word for it.

 

[aramis]

Yep, I'm definitely getting even rustier than I was last time I checked.
Don't use the stuff these days.
And whereas once upon a time I would have avidly checked Aramis's figures just for fun and my own edification, I simply can't be bothered any more.
He's right, at least in principle - I had a 'Doh!' moment when I read his reply, but as for the actual figures, my internal couch potato has won out - I'll just take his word for it.

I didn't do it by abstracted calculation; I did it by drawing it out at scale in a cad program; the angled jags are the "Apparent Up" (and aim for the rotation centerpoint, which is the lower left corner. Then using the measurement tools of the cad program.