Getting the Science Right, Part 2

[Brown]

The "Build the Enterprise" website is wrong, I think, to try to make a real functioning Enterprise look like the one of fiction. A spinning wheel or disc for gravity, sure, but it needs to be perpendicular to the line of thrust.

To make the gravity wheel habitable during linear acceleration is an engineering problem easily solvable with today's' technology. You just need to think in terms of compartments that "float" in relation to an outer shell, with ballast to keep the floor oriented "down". Think of those novelty eyeballs that are sold around Halloween time where an eyeball always looks up from within a ball that's rolling across a table. Similar structures strung together like a necklace, only probably cylinders rather than spheres, make up the circle of your gravity ring. You could even vary the rotational speed of your ring to compensate for the added "gravity" of your thrust.

I like the "eyeball" idea. Hmm, a segmented ring with individual segments that can detach from one another and can be independently oriented; and later may be rejoined into a substantially solid ring. You might have something there.

I'm not seeing how varying the rotational speed is going to work, unless everyone is concentrated at a single locus on the ring or unless you use the segmented ring idea. If people are distributed along the ring, some are going the feel themselves getting heavier and others are going to feel themselves getting lighter, then vice-versa. We know that the sensation of rapidly gaining and losing weight can produce queasiness in elevators and on roller coasters; whether passengers with prolonged exposure would get used to it or would puke out their intestines, I do not know.

 

[Brown]

It may be worth adding that Arthur Clarke, in "2061" (his generally forgettable sequel to "2001" and "2010") mentioned that linear acceleration and deceleration could be used to create artificial gravity. He also thought is was a good idea for passengers to go swimming in the ship's propellant (a big tank of water).

 

[catsmate]

It may be worth adding that Arthur Clarke, in "2061" (his generally forgettable sequel to "2001" and "2010") mentioned that linear acceleration and deceleration could be used to create artificial gravity. He also thought is was a good idea for passengers to go swimming in the ship's propellant (a big tank of water).

Nitpick: technically 2001, 2010 and 2061 take place in different universes.

 

[Mycroft]

I like the "eyeball" idea. Hmm, a segmented ring with individual segments that can detach from one another and can be independently oriented; and later may be rejoined into a substantially solid ring. You might have something there.

I don't think the segments need to detach from one another. They only need a little room to move to reorient as acceleration adds another vector to the sensation of gravity. Imagine the join between different cars on an articulated bus or a public train.

I'm not seeing how varying the rotational speed is going to work, unless everyone is concentrated at a single locus on the ring or unless you use the segmented ring idea. If people are distributed along the ring, some are going the feel themselves getting heavier and others are going to feel themselves getting lighter, then vice-versa. We know that the sensation of rapidly gaining and losing weight can produce queasiness in elevators and on roller coasters; whether passengers with prolonged exposure would get used to it or would puke out their intestines, I do not know.

I think the ring needs to be oriented around the axis of thrust in the same way the ships in 2001 and 2010 are, not as the saucer section of the Enterprise. This solves the problem of things gaining and losing weight.

It's not surprising that Arthur C. Clarks ideas work better, since they're designed with real physics in mind where the physics of Star Trek are made up.

 

[Beelzebuddy]

I'm probably already too late for this, but why on earth would you set most of the station at 1 g? Especially if it's going to be a resort environment, you want a much lower g, as low as you can get in the limits of safety. Imagine your stereotypical fat tourist, crammed into the XXL shiny spandex jumpsuit because that's the largest size they had. He's got a cameraphone in one hand and a leash for his kid in the other. What he could use more than fancy baseball is an environment that lets him bound majestically as he was meant to, feasting on squid and krill while periodically surfacing for air.

0.5 g, maybe? 0.33 g, and have a set of Mars suites? Youll still need some spokes descending to actual 1g acceleration for the purposes of gravity acclimation and other such stuff that can only be handled with earth gravity.

And that gives you the chance to have a local kid chased down into one of the crushingly-heavy "pits" for one reason or another, and run into a grumpy old codger still shaking the dirt off his boots. It's Dennis the Menace IN SPACE!

 

[Brown]

I think the ring needs to be oriented around the axis of thrust in the same way the ships in 2001 and 2010 are, not as the saucer section of the Enterprise. This solves the problem of things gaining and losing weight.

Maybe something that tilts the floor would help, too, angling the passengers slightly in the direction of acceleration. All the way around the ring, one side of the floor may be a meter "higher" than the other side. The effect would be similar to the way that a curved road "banks" to make a turn more manageable. It may be a bit disorienting for the floor to tilt (especially if the walls don't tilt--done properly the passengers would perceive that the walls are tilting rather than the floor, which would seem "level"), but this approach may be less technologically challenging than a compartmentalized or segmented ring.

The vector analysis, feedback systems (which would adjust floor tilt or wheel rotational speed so that passengers would have a substantially consistent feeling of "down"), computer controls and mechanics (e.g., hydraulics and electromotives) are well within the technology of today's engineers.

 

[Brown]

I'm probably already too late for this, but why on earth would you set most of the station at 1 g? Especially if it's going to be a resort environment, you want a much lower g, as low as you can get in the limits of safety. Imagine your stereotypical fat tourist, crammed into the XXL shiny spandex jumpsuit because that's the largest size they had. He's got a cameraphone in one hand and a leash for his kid in the other. What he could use more than fancy baseball is an environment that lets him bound majestically as he was meant to, feasting on squid and krill while periodically surfacing for air.

0.5 g, maybe? 0.33 g, and have a set of Mars suites? Youll still need some spokes descending to actual 1g acceleration for the purposes of gravity acclimation and other such stuff that can only be handled with earth gravity.

And that gives you the chance to have a local kid chased down into one of the crushingly-heavy "pits" for one reason or another, and run into a grumpy old codger still shaking the dirt off his boots. It's Dennis the Menace IN SPACE!

It has been suggested (e.g., by Arthur C. Clarke) that a space station should spin to generate less than one g. For those on their way to or from the Moon, Clarke thought, a less-than-one-g environment might offer opportunity for some acclimatization.

For the arrival at the station, there are special challenges for the passengers, especially if there is to be some ambulation in zero-g. Passengers will have to extract themselves from the seats and maneuver to the hatch, navigate a passageway and seat themselves in an elevator that will transport them to the rim. Each of these maneuvers may offer several challenges. All surfaces would have to be padded, passengers would probably be allowed to proceed only one at a time (with other passengers being held in their seats with restraints until their turn), and there would have to be plenty of ropes and poles and other handholds, along with the personal assistance of attendants.

In another alternative, passengers remain restrained in their seats until docking is completed. The ship may dock at the center hub, then the docked ship as a whole may be transported along one of the spokes to the rim, after which the passengers may exit. The passengers feel zero g, but they don't get an opportunity to move about until there are gravity-like conditions.

 

[wollery]

It has been suggested (e.g., by Arthur C. Clarke) that a space station should spin to generate less than one g. For those on their way to or from the Moon, Clarke thought, a less-than-one-g environment might offer opportunity for some acclimatization.

For the arrival at the station, there are special challenges for the passengers, especially if there is to be some ambulation in zero-g. Passengers will have to extract themselves from the seats and maneuver to the hatch, navigate a passageway and seat themselves in an elevator that will transport them to the rim. Each of these maneuvers may offer several challenges. All surfaces would have to be padded, passengers would probably be allowed to proceed only one at a time (with other passengers being held in their seats with restraints until their turn), and there would have to be plenty of ropes and poles and other handholds, along with the personal assistance of attendants.

In another alternative, passengers remain restrained in their seats until docking is completed. The ship may dock at the center hub, then the docked ship as a whole may be transported along one of the spokes to the rim, after which the passengers may exit. The passengers feel zero g, but they don't get an opportunity to move about until there are gravity-like conditions.

There's no problem getting a ship to match rotation velocity with the rim of a station, so no need to go to all that trouble, just dock at a point on the rim and the passengers will have full station weight straight away.

 

[Brown]

There's no problem getting a ship to match rotation velocity with the rim of a station, so no need to go to all that trouble, just dock at a point on the rim and the passengers will have full station weight straight away.

Yeah, I've added an extra step there, on the assumptions that it is easier to dock at the hub than at the rim, and that the extra apparatus associated with moving the docked ship from the hub to the rim is justified because it supports system compensation for the load in a gradual fashion. Hub docking has been used for, among other things, capture of rotating satellites on shuttle missions; grabbing the rotating rim was deemed too risky by NASA.

Direct rim docking is possible, but there might be several technical challenges to overcome.

 

[Beelzebuddy]

In another alternative, passengers remain restrained in their seats until docking is completed. The ship may dock at the center hub, then the docked ship as a whole may be transported along one of the spokes to the rim, after which the passengers may exit. The passengers feel zero g, but they don't get an opportunity to move about until there are gravity-like conditions.

For pete's sake, never design anything for tourists. The first exposure to space for many of them, and you wanna tie them down? That's ridiculous. Tell them to stay seated for legal reasons, but let 'em float a bit if they want and toss things to each other. That's what they're paying you for. Then taxi the ship down to the rim sowly enough that no one actually falls when g kicks in again.

Browsing the wikipedia, it looks like you'd need at least 0.5 g to give peoples' inner ears a "down" and thus avert spacesickness.

So you'd want at least five levels:

• 1 g level for return to Earth acclimation and accomodations for the easily spacesick.
• 0.66 g (guessing) for the "main" resort structures
• 0.38 g Mars level - recreation and research
• 0.16 g Moon level - acclimation, research and Whalers on the Moon ride.
• microgee - central column, enough g on the rim to make things fall but open in the middle. Then you rent people wings.

 

[SumDood]

This is all WAY over my head, but this is a good resource:

Space Settlements: A Design Study

Its from the 70s, and I really only mention it because my father worked on the project.

A google image search on 'L5 space colony' will provide many of the best pictures from the book.

 

[Brown]

For pete's sake, never design anything for tourists. The first exposure to space for many of them, and you wanna tie them down? That's ridiculous. Tell them to stay seated for legal reasons, but let 'em float a bit if they want and toss things to each other. That's what they're paying you for. Then taxi the ship down to the rim sowly enough that no one actually falls when g kicks in again.

Actually, the restraints (which may be similar to the restraints you'd find on some amusement park rides) would have several purposes. One would be to keep people from trying to push their ways out (as some do on aircraft), another would be to keep egress clear so as to prevent seated passengers from being bonked in the head accidentally by limbs of exiting passengers, another would be to use the restraints to offer a series of handholds, and still another would be to deal with motion sickness.

People who are held in place are, according to some reports, less likely to experience disorientation or vertigo in zero-g, and are less likely to pitch themselves in a way that causes them to become queasy. Even seasoned astronauts got sick in zero-g (Frank Borman being perhaps the most famous, as his puking reportedly made life challenging for the other Apollo 8 astronauts on their way to the Moon in 1968). Anti-motion sickness medicines can help with the queasiness that may be associated with launch, acceleration, free-fall onset, docking and egress.

In any event, a ship shuttling people to a space station would be expected to have far less room than, say, a commercial jet. There wouldn't be a lot of room to move around or throw things to one another. Guests could play around once they're in the station.

 

[Beelzebuddy]

Hm. What time period are we talking about, here? Is this a handful of millionaires, or busloads of retirees doing the tourism?

 

[Brown]

Hm. What time period are we talking about, here? Is this a handful of millionaires, or busloads of retirees doing the tourism?

You mean time period for egress? Probably much shorter than for a heavy commercial aircraft. You might be able to shuttle 20 to 50 in a spaceship, plus some luggage, but as the weight higher, the energy challenges get more demanding as well. Egress one-passenger-at-a-time might take a while, say, a minute per passenger. There would, of course, be those who could pull themselves along in zero-g rather effortlessly and make a quick and graceful exit, making it look easy. But there would also be those clumsy oafs who take extra time because they can't follow instructions and get themselves going bass-ackward or flailing about or stuck, and wind up needing assistance from the attendants.

Passengers exiting in zero-g would have to get themselves out of the space craft and to an elevator to ride to the rim (perhaps a sit-down elevator similar to that shown in "2001"). Each passenger might have to pull himself or herself along a corridor to get to the elevator. Once there, the passenger may have some challenges steering his or her butt into a seat and fastening a seat belt.

 

[Beelzebuddy]

No, I meant setting. Is this the first space tourism resort, open only for the uber-wealthy? Is it established later, an exotic locale for honeymooners and the well-to-do and staffed by disaffected college students on their wanderyaar? Is it one of dozens, just another exciting package you can select from your local travel office, cruises departing weekly, ask about our senior citizens discount?

 

[Brown]

No, I meant setting. Is this the first space tourism resort, open only for the uber-wealthy? Is it established later, an exotic locale for honeymooners and the well-to-do and staffed by disaffected college students on their wanderyaar? Is it one of dozens, just another exciting package you can select from your local travel office, cruises departing weekly, ask about our senior citizens discount?

Good question. I imagined a large facility, larger than that shown in "2001," so it might hold about as much as a tropical resort (say, a few hundred guests plus staff; one of the constraints may be how many folks can be evacuated in the event of an emergency). Like tropical resorts, it would be expensive to go there, but not beyond the means of many who are reasonably well off.

Carl Sagan, as I recall, imagined that the first space vacation spot would be open only to the super-rich, but a different business model might try to fund the venture with new and repeat business, which may mean trips may be more affordable.

This seemed to be the model that Kubrick used in "2001." His station had at least one hotel and impliedly some restaurants and recreational facilities (at which some unfortunate guest may have left a cashmere sweater), and catered to people who came and went, sometimes going to and from the Moon. Visitors were well-heeled but not financially elite.

Getting to the station could be by rocket launch, or by piggyback launch (an orbital vehicle launched from a sub-orbital vehicle, such as a one-hour flight from New York to Sydney) or by way of a space elevator. A space elevator could be very economical and could go quite a long way toward making space tourism cheaper; but so far no one is quite sure how to build one.

 

[Andrew Wiggin]

Just for kicks, how fast would "Ringworld" have to rotate to generate 1 g?

The radius would be, let's say, 150 million kilometers. If my math is right, one Ringworld "year" would be surprisingly short: about 9 days.

When the ship 'Hot Needle of Inquiry' fell onto the surface at a negligable absolute velocity (relative to the star), the surface was moving with enough velocity realtive to the ship that it bounced the ship thousands of miles, denting the scrith and leaving meteor craters at every impact. I don't have the book nearby, but the figure of 700 miles per second surface velocity comes to mind, which would be more than sufficient to hit like a nuclear bomb at each bounce. Thank fnangl for stasis fields.

 

[Brown]

I have recently seen two movies that at least tried to get some of the science right: Mr. Nobody (2009) and Elysium (2013). Both depicted rotating space wheels.

It was difficult to get the scale of the wheels from the movies, though the Elysium wheel was clearly much larger. Both seemed to be rotating at a speed appropriate for their size and the strength of the artificial gravity. (Making some rough estimates, the Elysium wheel could produce one g by rotating once in a little under five minutes.) In Elysium, there was no perceivable deflection of falling or thrown objects, but under the circumstances of the story, any such deflection (or lack thereof) might not be very noticeable. Besides, when Kruger (Sharlto Copley) fell from the platform, there did seem to be a slight deflection in his fall ...

... before he blew up.

The ring in Mr. Nobody was sealed, though it was not really a habitat, as was depicted in 2001 or Elysium, and it seemed to have a lot of wasted room. The Elysium ring had a sky open to space, which poses some technical challenges for atmosphere retention, as has already been observed in this thread.

 

[Delvo]

All of the problems that come from rotating for fake gravity instead of having actual gravity diminish with increased radius. So do the differences in how drastic these problems are between one floor/deck and another. This gives the engineers designing the thing an incentive to increase its radius at least up to the point at which the side effects become irrelevantly tiny. The obvious objection is that you can't just make the thing bigger because that magnifies the amount of materials it needs. But engineers maximize one thing that's important by changing something else that isn't. So the first two tricks up their sleeves, to maximize radius while keeping material requirements constant, will be:

1. Reduction of number of floors/decks, with more horizontal area apiece to spread things out on
2. Not a full ring but two separate enclosures, each extending well under halfway around the circle that they travel in (might look like Viking hammers, might even look like relatively flat square pods), connected only by a couple of elevator shafts or even a cable tether

 

[Lensman]

Would this rough pic be feasible?
(Please excuse my poor MSPaint drawing skills)



The left hand ship is configured for when it's under thrust, not spinning

The right hand ship is configured for when it's coasting or in orbit, spinning on it's longitudinal axis.
The arms that rotate outward could even be tethers that extend outward as mentioned above.

The squares at the end of the arms would be the crews quarters - they'd also rotate.
When the ship is under thrust the floors would be oriented to the rear, therefore down would be towards aft.
When the ship is coasting or in orbit (& spinning on it's longitudinal axis), the floors would be oriented outward, therefore down would be out.