Artificial Gravity: A New Spin on an Old Idea

Space.com ^ | 25 November 2004 | Leonard David

[perfect stranger]

That's what I thought too. LOL

[Oblongata]

You just need one of these:

Food goes in, super dense dark-matter comes out.

[Tealc]

Of course, we could just ask the Minbari...

They already gave Earth that very technology! :)

[jennyp]

But it's another thing entirely to spin a space-suited astronaut on the end of pole in outer-space. That's not complex. It's not heavy. It's not expensive.

It's just not indoors. The astronaut has to be suited, but we can give her 1 G of centrifugal force in outer-space.

Wheeeeeeeeeeeeeee!!!!!!!!

[r9etb]

A super dense material would be super massive. If it were created in orbit somehow, that wouldn't necessarily be a problem. But if it had to be lifted into orbit, enough mass to create useful gravity would be too expensive to put up there.

Not to mention a) the impossibility of getting rockets that could push that mass out of Earth orbit; and b) the unfortunate tidal waves, earthquakes, and volcanoes that would result from a supermassive body moving around in low Earth orbit....

[r9etb]

The non-rotating center of mass between the two could contain navigation and communication equipment.

No way you'd want to have a non-rotating center -- that means all sorts of moving parts, bearings, seals, and so on.

Another major problem would be attitude control. How do you point the little guy when you need to do a burn?

Probably the biggest problem would be mass balancing. You'd have to be extremely careful about that, and it'd be very difficult to manage.

[robertpaulsen]

"No way you'd want to have a non-rotating center -- that means all sorts of moving parts, bearings, seals, and so on."

My bad. I meant a stable center of mass which would rotate. You should be able to do navigation and communication through that.

"Another major problem would be attitude control. How do you point the little guy when you need to do a burn?"

That's why I like cables. Stop the spin, reel in, lock the structure, then burn. Crews could meet, maybe exchange members to mix things up, trade baseball cards, whatever. Then unreel and re-rotate.

"Probably the biggest problem would be mass balancing."

True. Overboard dumps would have to be managed. But with two separate cables (one to each spacecraft), the center hub could "slide" one way or the other to remain a stable axis.

[punster]

It is also helpful when the astronauts go to the restroom. Considering the most practical approach is the centrifuge idea, it is enough to make your head spin.

[derlauerer]

If a propulsion system could be developed that would consistently accelerate at 1g for half the trip and then decelerate at 1g for the other half of the trip, then the problem would be solved. Of course to obtain the velocity you would need, you could accelerate at 3 or 5 g's for short periods of time. They only problem on this would be finding a propulsion system and a fuel to run it.

Actually, at a continuous acceleration of 1G, you can build up some quite amazing speeds really quickly.

For example, accelerating at 1G (9.81 meters/second) for a period of one day (86400 seconds) will give you a velocity of nearly 850 kilometers per second. During this time, you will travel over 36.5 million kilometers.

A two-day trip, therefore, accelerating until halfway, and decelerating thereafter, would take you more than 73 million kilometers from your starting point. A four-day trip would cover nearly 300 million kilometers, or more than the typical length of a trip to Mars.

Basically, using a continuous acceleration/deceleration of 1G will enable you to get to anywhere in the Solar System in less than a month.

[nevergiveup]

Ah, ignoring the engineering obsticals whose solutions are currently inconceivable, I think you forgot something more fundamental called "relativity".

Hint, for the observer, you were much too optimistic but for the passenger, the news is much better than you wrote.

[Moonman62]

One issue that has worked against artificial gravity advocates in the past has been the vision of a huge, rotating spacecraft that gives its inhabitants a one-gravity condition like here on Earth. And movies like 2001: A Space Odyssey helped cement that "G-whiz" image into the space psyche. But large meant expensive, and also gave engineers design worries, Young related.

It's Kubrick's fault. If it isn't Bush or Walmart, it's Kubrick.

In recent years, the idea has started to emerge that a short radius centrifuge contained within a spacecraft may be far more attractive. "You go into it for a workout. You get your G-tolerance buildup for a certain period of time, daily or a few times a week. That started to sound attractive to the engineers," Young said.

But wait a minute. There was a much smaller centrifuge inside the Discovery spaceship in 2001. Maybe it isn't Kubrick's fault after all.

For a movie that started production in 1964, 2001 is an amazing work.

[Poincare]

Sure...but you'd have to have as much as a planet weighs in order to generate one G of gravity from it. Now imagine trying to boost that mass into space...

Not completely. A denser than Earth substance would allow one to get closer to the gravitational center so that less mass would be required to obtain 1 g. As it happens if one could stand on the core of the Earth one would experience 1 g. (The massive core still being to much to launch.)

[Oberon]

A denser than Earth substance would allow one to get closer to the gravitational center so that less mass would be required to obtain 1 g. As it happens if one could stand on the core of the Earth one would experience 1 g. (The massive core still being to much to launch.)

Read the fine print, dude...I didn't write "as much as the Earth weighs," I wrote "as much as a planet weighs." Even accounting for a high-density object permitting closer proximity, you'd still have at least a Mercury's worth of mass to lift off the ground.

[Poincare]

What is your problem? Dude?

The bottom line is that the denser the mass, the less that is needed. BookaT mentioned the idea of a super dense mass. Such things are in our universe, just not on Earth in any quantity. If there were a way to assemble a mass of, say, concentrated neutrons as found in a neutron star, it would merit consideration. If there were a way.

[Oberon]

What is your problem? Dude?

My problem is a fellow who picks nits with others' statements, yet who expects those same others to accept his own technically erroneous statements without criticism.

If you see anyone like that, you let 'em know, okay?

[FreedomCalls]

Before Stanley Kubrick and Arthur C. Clarke conceived of an orbiting rotating space station, Wernher Von Braun, Willy Ley, and Chesley Bonestell had already developed the idea in Colliers Magazine in March of 1954 .

[FreedomCalls]

And here's a sketch that Wernher Von Braun presented to the US Army in 1946:

[Poincare]

but you'd have to have as much as a planet weighs in order to generate one G of gravity from it.

So I was kind to say "not completely". Your statement above (post 7) is beyond "nit-picking", it confounds mass and weight, and g (acceleration at Earth surface) and G (gravitational constant), and it does not address BookaT's proposition.

Get a mirror.

[Oberon]

I see this is the sort of discussion one cannot win. In fact, participating even this far makes me something of a schlemiel.

[sigh]

[U S Army EOD]

Then lets do it.