What Ever Happened to the Cartwheel Space Station?

Could it perhaps have something to do with the fact that the diameter required to produce practical gravity, and the required RPMs, might be unrealistic in scale? If so, you'd thing that the writers would have taken that into consideration. The better SF writers are quite often rather anal about getting their science right.

I'm hoping that Jorrie might be one of the people that throws his two cents in.

When I put 28 meters in as the radius , i got about 16 m/ s needed ?

Did you account for the fact that the velocity is squared? What did you use for the mass?

The Mass cancels out.

The formula ends up as R*a=V^2

for 1 g a is about 9.81 m/s

for R = 28

V is about 16.6

(I had done in in my head to come up with 16)

Am I doing something wrong?

The size of the cartwheel has to be much more than anything we can easily build at this time. If you don't get it rather huge, you get too much gradient between the feet and head. At the least, that means every time you bend over to tie your gravity bootlaces, you fall on your butt. The main reason for wanting gravity is for the health of the astronauts - they lose muscle tone and bone mass in low g environments and have a hard time with blood pressure. Cleveland Clinic and Wyle Labs are doing work with vertical treadmills and short-arm centrifuges to try to deal with this. You might want to read some of this guy's work.

I think it has more to do with inner ear disorientation and mass distribution.

If you turn your head in a centrifuge your vestibular system gets erroneous cues as to your position. This can cause sudden nausea for many people.

In theory if you make the radius of the centrifuge large enough this should be less and less of a problem. I don't know what that critical distance really is.

A second problem is mass distribution. Moving individuals and equipment will disturb the center of mass for the rotating system and if those changes are of enough magnitude it could set the system into an unstable wobble or a spin-quake.

You're correct. You have two organs in there: the semicircular canals sense angular acceleration, whilst the otoliths sense linear acceleration. In small radius spacestations, either turning the head causes you to think you've just rotated or lowering the head causes you to think you've just slammed on the brakes. You can learn to suppress the input from the semicicrcular canals, but I don't think you can from the otoliths (Have to check on that).

From the standpoint of gradients, short-arm centrifuges would be the worst. For a cartwheel of 20-meter radius, the maximum gradient on a 2-meter-tall person on the periphery would be 10%, probably insignificant.

Well nobody said it would be "easy". I recall reading somewhere about an idea to launch the shuttles basically empty, and carry those huge fuel tanks into orbit. How many of those do you need to attach nose to tail to get you cartwheel of sufficient diameter? Then you start launching full shuttles with all the things needed to furnish the empty fuel tanks. (Venting them into the nerar vacuum of space will clean out all the nasty fuel residues)

Is (was) this a viable plan?

I was picturing something in the range of 200' diameter, or so. No science in that estimate. Just a gut feeling. That's smaller, overall, than the current ISS; but given the donut shape, that's considerably more compartment area. Given the fact that every module would be nearly identical, as opposed to the mish mash of shapes currently involved, fabrication might be somewhat simplified. I guess automatic wobble correction would be required to account for slight weight shifts. That sounds to be in the realm of the possible. An appropriate place to mount the solar panels might be a challenge, given their need to be adjustable for constant maximum exposure. I was thinking the solar panel disc could be mounted in the center, in the manner that a carburetor choke plate is mounted. But that might not be fully adjustable at all times for optimum positioning. And come to think of it... a constantly shifting central solar panel may cause more unbalance than can be easily counteracted.

I think, based on back of the envelope calculation, that you need about a 500 m radius. I'd have to recheck my calculation when I'm alert, but that sounds right.

Hmm. Almost exactly one mile of outer corridor. That's rather unrealistic, isn't it.

... oh wait... my bad. Actually, that's almost two miles

Yep, it is unrealistic. That's part of why it's not been built.

Well unless you misplaced a decimal point on that envelope, that may be reason enough.

So... no flying cars AND no cartwheel space stations

Not yet... Our first large space station can't be all we can imagine, we need to know more about building and living out in space. The current station's expected usefull life is not all that great, given the investment. A lunar base may be more realistic, then we build from there.

The station's solar panels need not be attached to the structure proper and probably shouldn't be, because there will be points in the station's orbit where the structure will shadow the panels. Better if they co-orbited with the station and were tethered to it, with the feeds coming in through a rotary coupling in the central hub. The huge, dual-cartwheeled Space Station V in Kubrick's 2001: A Space Odyssey had no solar panels; presumably the station, which was shown in the film as only partially completed, was nuclear-powered, but no provision was evident for dissipating a reactor's waste heat. Come to think of it, I've never seen an artist's conception of a cartwheel structure which featured solar panels. Possibly they would have detracted from the central concept presented, that of spin-induced artificial gravity?

Night Owl

The basic physics, if we want a spoked station with 1G, the size of this is 25 times what we have done so far - although we could make a station with only two masses on the end of a tethering fairly easily - each mass being a cube/sphere 15 feet on a side - still a substantial structure with a central airlock. It can be made smaller = less habitat.

It would need to be kept balanced and station keeping via rockets could be complex.

rings can have zero G sections at the center, with a counter-rotating bearing to get true zero G, but of course the station mass will be an attractor.

Once we get a large enough mass in orbit, wheels can be made. Will we ever?

The, Space Elevator when and if it finally arrives - maybe with the new single sheet graphite cable we have yet to make which reaches the theoretical strength?

I scanned all and read much of the Wikipedia article, and saw no mention of what I think might be another major obstacle. Your carbon cable, assuming it could be produced, would be a conductor of electricity. Wouldn't it act as a short to discharge the ionosphere, destroying the cable in the process? Then there would be the problems associated with the weakening of the ionosphere...

There is already an annual competition for building climbers for the ribbon. At least for several years now. R&D for the space elevator is alive and well. I don't know the answer to the concern you just mentioned, but I'll assume there is some way around it.

NASA did a tether experiment a few years back. As I recall, the induced currents blew it apart less than half-way through it's deployment. Sounds like a nifty power source.

That is my understanding as well, GA

I do believe you are correct NSS. GA

I guess you didn't know..

International Space Station

Cartwheel Space Stations are inherently large to prevent a gravity differential between your head and feet from creating health problems. There are no really big space stations yet.

Join the planetary Society at www.planetary.org to get the latest on everything in space exploration.

Guys,

Surely the major reason for not building the cartwhel first( as the first ISS) is the need to manufacture in sections and assemble in Orbit, an assymetric Cartwheel partially built would tend to pull itself apart, have difficult orbital mrchanics, and be potentially unreliable for the builders.

I have done no calculations, this is just gut feel.

Of course if you built it far enough out then most of the above would be mitigated.

Sleepy.

Yes, Any such wheel must be balanced prior to spin up.

The main question is:- Shall we build such a complex wheel to get one G on the people in it? It is well known that the human body degrades in zero G, even with various exercise methods used astronauts lose muscle mass, bone mass and fitness after months in orbit. A 2 year trip to Mars, with orbit for a time and 2 years back, could be quite the danger.

A simpler barbell station might provide the needed G at the ends and provide a centre point for docking.

design search

Von Braun's 1952 design

A small accident, as while coupling,internal masses movements, makes unpredictable the further motion of this "almost a wheel".Not easy see how put it in order back (even so when you suppose a constant rot.moment "L").-

Why would this be any different to any non rotating space station?

Another problem that nobody mentioned is trying to dock with something that keeps moving in a circle.

So far the only solution I have seen that would be practical would be to have some sort of hangar system located at the point of rotation al la 2001 A Space Odyssey in the image below.

I do remember seeing a proposal back before they started with the ISS that used a number of spent` shuttle fuel tanks linked together in a ring but I don't know how many tanks they intended to use or how fast it was going to rotate but it still had the problem with how do you dock with something that keeps moving.

Something that nobody's mentioned is that aligning the solar panels with the sun isn't as bad as it first sounds because the gyroscopic effect would keep the station aligned with fixed point in the sky. That means that you would only have to correct for about 1° worth of rotation a day due to the Earth's rotation around the Sun. At the moment they need to correct for 180° every 45 minutes that they as they orbit the earth every 90 minutes or so.

By the way, if your ever lucky enough to see the sun reflect of the ISS solar arrays as it goes over head be prepared for a brilliantly bright flash that lasts for about 4 for 5 seconds. It several times brighter than the landing lights of an approaching aircraft and took me by complete surprize when I saw it.

Yes, and as someone mentioned, you can counter-rotate the center whenever the need exists for a departure or entry.

Even simplere is a simple rotating docking tube that extends from the hub much the same way that the Shuttle interfaces with the ISS. The only change required is a rotating collar.

I would assume that the collar would have to be actively rotated, because even the small amount of frictional drag caused by the collar would eventually impart a spin on the docking spacecraft.

Worse, if the docking ring on the spacecraft is not at the spacecraft's center of gravity it would impart a torque on the docking tube that would like cause a catastrophic failure of that tube.

in 2001 this exact scenario was envisaged, when the approaching craft centered on the collar and then matched rotation to dock with the station. In other Science Fiction movies, the rotating collar has been envisaged. All methods involve a degree of mechanical complexity, but this is after all, rocket science...

Rotating the SV (space vehicle) is easy to do. We can use autopilot to land an F/A-18 on a pitching/heaving aircraft carrier...

But, the SV would have to be dead nuts center to do this. If you are off any amount that roll maneuver would have to be a corkscrew maneuver, which would require continuous thrusters to perform.

That would be dangerous and expensive to do. That is why it is simpler to rotate the center hub or do my rotating docking collar idea.

I remember the movie, but I can't remember how Clark envisioned it in his actual book. Was it like the movie or did the hub rotate?

once a fully coaxial attitude has been reached and the same turns per minute, all that is needed is unidirectional thrust to set the mating speed and automatic attitude adjustment. Since it will mate into a form of socket, with shock absorbers and some degree of off-axis tolerance, it should be doable.

<...trying to dock with something that keeps moving in a circle....>

Make it threaded! At least it will tighten itself up as rotational speed increases...

Why would it have to be a complete "wheel" to get the desired effect of gravitation? As long as it's balanced and rotating around an axis, it should work.

For shoping!-

Our Asian friends? What are you talking about? I think your attempt to impart some type of American politics into this question made you forget that what is orbiting out there now is an INTERNATIONAL Space Station. Anything that follows will also be a collaboration. As a matter of fact, thank God for science projects... they often seem to be the only way countries can cooperate. "Space Scientists" don't have nationalities. They have a planet.

This isn't an American problem. It's a human problem.

I agree my Village has to build it for all to benefit, even our less socially active neighbors. A global orbiting station for a global village, a great science project going beyond sharing crap on the Internet.

It would have never been done with out the US as a partner. We have paid 50% or more of the total cost of the system and its maintenance.

So, we are a prime partner, but you are right that it still is a collaboration.

Very true. Actually the US contribution is considerably more than 50%. But still... The combined total of what's left is a huge amount of money. And despite NASA's knowledge of the subject of space travel, there is still much to be gained in the way of brain power from the rest of the world.

I can't remember what movie it was, but I recall a situation where the superpowers went to war on earth, but in space, the stranded "enemies" who shared habitation up there remained dedicated to peace and their common scientific goals... all the while cursing their own generals and politicians. I can imagine that that would be a realistic situation. At least, the idealistic aspects of me imagine that to be the case.

2010 did a spin on that same theme when Americans and Russians were cohabiting a Russian vessel to reach the space ship Discovery.

You guys should definitely check out the Planetary Society www.planetary.org .

Having a large central core that does not rotate would not have gravity and be great for docking. For creature comfort having a rotating outer ring maintained in position by maglev like maglev trains would be great. To get between rotating and non rotating areas an elevator also run on maglev would have to produce simutaneous linear lift and rotational acceleration by travelling a spiral path and exiting onto a platform in the chosen section at equal rotational velocity so there is no relative rotational motion.

All you maglev high speed train engineers get to work designing a space station!!!

First, before any larger space station can be built in orbit, you have to have a proven, reliable and much larger delivery system to get the materials into orbit. With the retirement of the Space Shuttle that will not be possible in the near term. Lack of NASA funds is another. Even the shuttle was woefully lacking in cargo carrying abilities, ie serious limitations regarding available load and space.

The energy intensive lift from the earth to orbit is the problem. Comet/asteroid/lunar mining may well allow for a more efficient sourcing of some building/breathing materials, because they all cost less in energy to fetch to a geosynchronous orbit. They may be some rocks at the Lagrange points which would have lower cost to move - but they would not have free water - baked dry. Cometary bodies would be sources of water, but are often traveling at such high speeds that it would be energetically costly to mine them, but a solar powered ion drive that could gradually bring a few large lumps to an earth orbit - sadly, such tech is decades away

Once we create a 1 G gravity, won't we have to increase it strength?

For the moment, structural members don't need to hold any weight. Only need to keep it together during accelerations or impacts from the shuttle.

Could the space station stay together in a gravity environment?

Why would it have to be 1 G?

I wonder what G is medically needed to maintain bone/muscle/etc?

I doubt the ISS will will serve that function - although it could.

Currently the US is scheduled to cut all funding to the ISS sometime around 2017. I don't know if anyone else will be picking up the load or what the future holds for the ISS.

From the US perspective it is mission accomplished.

Although maintaining the ISS is quite expensive, it doesn't compare to the cost of planning it, engineering it, fabricating it, transporting it into orbit and assembling it. 2017 is still two presidents away. A lot can happen in that time. I wouldn't count it out entirely, just yet. Look how far beyond original schedules the Hubble and Mars Rover projects continued.

You are right. The political winds change directions frequently and without warning. NASA has been blowing (aimlessly) in those winds for some time now.

I'm very curious as to when our first astronaut president will be elected. Shall we start a pool? I sayyyyyyyy..... um, 2044.

Back to the original question, the large cartwheel space-station presents to large a challenge for todays technology to build on earth and put into space.

The international space station is the forerunner of future manufacturing in space. The Cartwheel station will have to be made from materials manufactured in space and avoid transportation issues getting material from earth.

Where will the material come from then...perhaps low gravity neighbor planets and moons.

Well, I read that one of the issues was the curved sections. Unless the thing had a large diameter overall, the curved members making up the structure would be difficult to send up on conventional boosters or on the shuttle. The radii of the modules would prevent fitting on a rocket or in the shuttle as payload, as compared to the "straight" modules used in the ISS.

Hm. Very interesting. Certainly makes some sense.

Although... with this 500m radius that has been mentioned, that may not have been overly relevant.

How about it folks? Are we still at 500m radius, to get 1g with no headache when you bend over? That sounds excessive, but I don't know the math on that one.

Hi OoBE, you wrote: "Are we still at 500m radius, to get 1g with no headache when you bend over? That sounds excessive, but I don't know the math on that one."

The math for the centripetal acceleration at any radius on a rotating structure is quite straightforward: a = rω². To get 1g at 500m, we need ω = √(9.8/500) ~ 0.14 rad/s or ~ 8°/s, about 45 seconds per full revolution. Not too dizzying.

At the radius difference of a human length, say 2m, we get a acceleration difference of Δa = Δr ω² ~ 0.04 m/s², or 4 milli-g, quite negligible when you bend over.

If we can get used to double the rotation rate (0.28 rad/s) and need only Mars gravity (3.7 m/s²), the radius required is: r = a/ω² ~ 47 m. Much cheaper to build. The 'bending over' problem is now Δa ~ 0.016 m/s², or 16 milli-g, still really nothing if my calcs are right. Please check...

-J

My original estimate was about 30 m radius (200' diameter), which seemed within our ability to construct; smaller overall dimension than current ISS, but considerably more living space with a full circle. When it was pointed out that 500 m radius was required (for 1 g), that clearly put it out of the realm of possibility for current technology. But 47 m radius certainly seems possible, even at the reduced gravity.

So part of my original question was, if the cartwheel design still held merit at a later date, or if it is simply never going to be.

With all the input, it appears that the basic idea is still sound, and that some possibility exists that it could potentially be used as a second generation station. Perhaps within a generation?

"With all the input, it appears that the basic idea is still sound, and that some possibility exists that it could potentially be used as a second generation station. Perhaps within a generation?

I think it already possible, but as I hinted in #51: "... taking into account that it takes a lot of energy to get one kg up to Earth orbit and more than twice as much to escape Earth. Hence, the trip to Mars will probably have to be weightless all the way and we must learn how to deal with that."

We need the standard ISS to learn how to deal with zero-g, so there is very little benefit from a cartwheel in Earth orbit, yet huge cost. IMO, the probability is very low for the foreseeable future - maybe in deep space, but much later...

-J

Back in the Apollo days they had to rotate the spacecraft while it was in space to prevent one side from cooking with the heat of the sun while the shaded side was freezing with temperatures of around 5°K.

Mind you, I would expect that they had to cancel the rotation every time they tried to take a stellar fix or do a course correction burn, not to mention lunar orbit injection and exit burns.

So, on a trip to Mars they would definitely have to have some sort of rotation that prevented the temperature differential from wrecking the spacecraft so it's not that much of a stretch to use the rotation to give them some sort of artificial gravity.

Sounds reasonable and appears to answer my question. The cartwheel would work, and we could build it, but we didn't build a cartwheel this time because they didn't particularly want gravity on this particular ISS, because of the zero-g experiments that were an important aspect of having this ISS in the first place.

Thank you everyone. Interesting conversation and some great insight from very many of you.

A polygon could work, as opposed to curved sections.

Yeah, but that would be really bumpy to roll.

Just put curved segments at the corners so that skateboarders don't get bumped too hard....

This is a little off topic but do any of you remember the running track they had on Skylab. It was a section with some sort of shock absorbing material that ran around the perimeter of the inner structure that the astronauts would run around.

I don't know what sort of force they were generating but they were certainly running around in circles pretty well and looked like they had things well under control.

You were calculating the acceleration as good students school.Why don't tell now how to keep that huge mech.energy in a stable energy of the simplest spinning.As an example, somebody here would please calculate the further movement if the SS receives a given "J" impulse at any point of the SS? What devices or even better how must operate the devices designed to keep a fixed axle of the SS? Just fantasy.-

A tangential impulse will speed/slow the wheel. Any other impulse will move the wheel and/or give rise to toppling moments - and give rise to wobble.

That said, a large wheel will have a large moment of inertia, and will tolerate smaller impulses. Other movements, like people running, cargo movements, etc. will also do this.

Thus the station will need to be trimmed with counter impulses to maintain the set standard. An automatic system will deal with this. Large cargo movements, etc, will each have their counter. Weights on the spokes can be moved as needed.

It must not only be tangential, but must be a force couple (equal and opposite forces of equal duration on opposite sides of center) to avoid wobble.

Maybe it just rolled away....

You could do a structure something like The London Eye (only smaller), and instead of a rotating center, just have a landing pad planar with the disc, that you sync with the arriving craft, then once its locked down, let it all catch up with the rotation, then it's just a case of registration of ports to move cargo.

I don't think balance is a difficult problem - you'd have to have a fair bit of water about so use that.

One of the things nobody's really mentioned is vibrations. Vibrations in space are a really big problem because there's no atmosphere to stop them, so one they start they keep going forever.

Even peddling on a stationary bike can be a problem and on the ISS has to be isolated from the main structure with vibration cancelling mounts so that the vibrations aren't transferred to the main structure.

Therefore, I would hazard to guess that vibrations and getting the rotating wheel even slightly out of kilter on a rotating space station would be a total nightmare for engineers as once started could be nigh on impossible to stop.

Hi Masu,

I agree that vibrations are a problem on a large spacecraft, but they cannot last for very long. I think the stresses inside the structure dampen them out rather quickly, unless there is a resonance (bad design).

-J

There is on one side at least.Anyway is an interesting question,first thing, how's the problem in the SS today?.I agree waves becomes a real trouble if balance issues are not considered.-