Author Topic: Realistic, near-term, rotating Space Station  (Read 238903 times)

Offline Roy_H

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Re: Realistic, near-term, rotating Space Station
« Reply #1200 on: 08/29/2018 06:11 PM »
If you read my proposal (attached below, unchanged from last time) you will note that the core does not rotate, but since the axis is north-south there is no precession, makes it easy for visiting spacecraft to dock. No changes in orientation required, no energy expended.
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Offline TripleSeven

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Re: Realistic, near-term, rotating Space Station
« Reply #1201 on: 08/29/2018 06:25 PM »
Arm rotated out
Suggested approach path.  Just sails on if something goes wrong.

A lot of mass is being dedicated to being able to transfer people and cargo in that design.

Something else to consider is what is called here on Earth "underway replenishment". These are situations where two or moving vehicles are not attached to a fixed location, but are moving relative to each other. Which is the same situation as two space vehicles.



Since we're dealing with the harsh environment of space you'd probably still need some sort of pod that would shuttle between the visiting vehicle and the space station, but the mechanical interfaces would be much less complicated since you only have to deal with cargo and not the whole spaceship.

Just a thought...

interesting.  I thought of this a bit the last few days...

it strikes me that a effort like this would be quite easy in space...what one would need is some sort of "modest" connection between the two vehicles to stabilize position but then after that ...it would be easy to do most of the transfers from "hoses" (or more likely lines) and cargo transfer could be done in cargo pallets either pressurized or un pressurized...a neat idea much better in my view than docking

Offline 1

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Re: Realistic, near-term, rotating Space Station
« Reply #1202 on: 08/30/2018 12:30 AM »
If you read my proposal (attached below, unchanged from last time) you will note that the core does not rotate, but since the axis is north-south there is no precession, makes it easy for visiting spacecraft to dock. No changes in orientation required, no energy expended.

Yes, this would be my preferred orientation as well. My discussion with mikelepage stems from a hypothetical need for the station to maintain a sun-facing (radial?) orientation. The validity of that need is accepted for the sake of discussion, but is otherwise worthy of its own analysis.

Online Coastal Ron

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Re: Realistic, near-term, rotating Space Station
« Reply #1203 on: 08/30/2018 12:48 AM »
it strikes me that a effort like this would be quite easy in space...what one would need is some sort of "modest" connection between the two vehicles to stabilize position but then after that...

It requires the least amount of complexity to move mass from a non-rotational orientation to the one the space station has - and the least amount of mass that has to be spun up and spun down.

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it would be easy to do most of the transfers from "hoses" (or more likely lines) and cargo transfer could be done in cargo pallets either pressurized or un pressurized...a neat idea much better in my view than docking

You can still dock "pods" or standardized cargo vehicles, and I think that will actually end up being the more popular method because then you can use the same vehicle size for both cargo, pressurized containers (i.e. water, propellant, etc.) and crew. Sending crew across on a line is not going to be optimal (ala 2010 movie).
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Offline Paul451

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Re: Realistic, near-term, rotating Space Station
« Reply #1204 on: 08/30/2018 08:11 AM »


Ships will stay underway during this manoeuvre so that they can keep constant distance against wind/waves pushing them around. No wind or waves in space (nerd pedantry aside) but you will be moved around by every action: capture of lines, movement of cargo, etc. And you can't just rely on the lines to stop you drifting apart, because you'll bounce back and drift into the station.

To use lines, you'd need to use a lot of station-keeping thrusters. For the ISS, thruster-firing near the station is verboten, but... you know, ISS. Nonetheless, even for a more robust station, I think you'd at least want a simple robotic arm ("docking arm") holding the cargo-ship steady, while another (more complex) moves cargo/etc from its cargo-bay. I don't think you would end up saving much from using lines and then having to work around the issues they cause.

And, thinking about it, you are surely going to have robot-arms to help during construction. So what mass are you really wasting by using them for cargo-ops?

Online Coastal Ron

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Re: Realistic, near-term, rotating Space Station
« Reply #1205 on: 08/30/2018 02:46 PM »
Ships will stay underway during this manoeuvre so that they can keep constant distance against wind/waves pushing them around...

Few analogies are perfect, and it was the concept of just moving the absolute minimum between vessels that I wanted to highlight.

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I think you'd at least want a simple robotic arm ("docking arm") holding the cargo-ship steady, while another (more complex) moves cargo/etc from its cargo-bay. I don't think you would end up saving much from using lines and then having to work around the issues they cause.

And, thinking about it, you are surely going to have robot-arms to help during construction. So what mass are you really wasting by using them for cargo-ops?

The bare minimum you'd need between two independent bodies in space, regardless what combination of spaceships and space stations, is to just "hand off" things between the two. And yes, a robotic arm would be perfect for that, and it would need to have some way to spin/de-spin the payload for rotating space stations - which should be pretty easy (likely the higher mass vessel would do the spin/de-spin maneuvers).

For basic rotating space stations, especially early generation ones, this type of mass transfer would be the least complicated for all concerned.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Online Asteroza

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Re: Realistic, near-term, rotating Space Station
« Reply #1206 on: 08/30/2018 11:09 PM »
It's a shame there isn't some kind of easily controllable/collapsible noodle-like arm thingy that can take both tension and compression forces.

Something like a tensegrity tower structure, where the hard center poles use something like SMA actuators to change length, as well as contain linear actuators to pull on the wires between the poles.

The space equivalent of a boat berthing rope setup, something like a slightly flexible V pole setup with a set of Y wires between the points, with the visiting vehicle located at the center of the Y.

Online Coastal Ron

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Re: Realistic, near-term, rotating Space Station
« Reply #1207 on: 08/30/2018 11:31 PM »
It's a shame there isn't some kind of easily controllable/collapsible noodle-like arm thingy that can take both tension and compression forces.

Something like a tensegrity tower structure, where the hard center poles use something like SMA actuators to change length, as well as contain linear actuators to pull on the wires between the poles.

The space equivalent of a boat berthing rope setup, something like a slightly flexible V pole setup with a set of Y wires between the points, with the visiting vehicle located at the center of the Y.

Seems like it was a couple of decades ago that there was a proposal to capture VTOL aircraft at sea using a robotic arm that could compensate for wave action and ship movement relative to the position of the VTOL aircraft. I think it proved to be more complicated than needed, but since things in space should move in far more predictable ways I'm sure a long robotic arm could be used for moving cargo to/from a rotating stations.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Online Asteroza

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Re: Realistic, near-term, rotating Space Station
« Reply #1208 on: 08/31/2018 02:59 AM »
It's a shame there isn't some kind of easily controllable/collapsible noodle-like arm thingy that can take both tension and compression forces.

Something like a tensegrity tower structure, where the hard center poles use something like SMA actuators to change length, as well as contain linear actuators to pull on the wires between the poles.

The space equivalent of a boat berthing rope setup, something like a slightly flexible V pole setup with a set of Y wires between the points, with the visiting vehicle located at the center of the Y.

Seems like it was a couple of decades ago that there was a proposal to capture VTOL aircraft at sea using a robotic arm that could compensate for wave action and ship movement relative to the position of the VTOL aircraft. I think it proved to be more complicated than needed, but since things in space should move in far more predictable ways I'm sure a long robotic arm could be used for moving cargo to/from a rotating stations.

You're remembering the british Skyhook program for Harrier jumpjet deployment/capture on destroyers without proper flightdecks.

A big hard robot arm is fine and all, but it's a fixed structure with mass and size working against you. Something very lightweight that can maintain standoff distances almost passively is probably the end goal if you want to essentially replicate naval underway replenishment.

Online Coastal Ron

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Re: Realistic, near-term, rotating Space Station
« Reply #1209 on: 08/31/2018 03:24 AM »
You're remembering the british Skyhook program for Harrier jumpjet deployment/capture on destroyers without proper flightdecks.

That could be it. Whatever it was it was intended for small landing areas.

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A big hard robot arm is fine and all, but it's a fixed structure with mass and size working against you. Something very lightweight that can maintain standoff distances almost passively is probably the end goal if you want to essentially replicate naval underway replenishment.

In space it's very easy to maintain relative distance between two objects, especially if the large vehicle is not thrusting - the smaller vehicle just does the small adjustments to distance like what is done with visiting vehicles to the ISS.

The challenge is transferring mass between the two vehicles, which is why having a robotic arm to make the transfer makes sense. The end of the arm can rotate to spin and de-spin payloads as needed.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline mikelepage

Re: Realistic, near-term, rotating Space Station
« Reply #1210 on: 09/06/2018 03:49 AM »
If you read my proposal (attached below, unchanged from last time) you will note that the core does not rotate, but since the axis is north-south there is no precession, makes it easy for visiting spacecraft to dock. No changes in orientation required, no energy expended.

Yes, this would be my preferred orientation as well. My discussion with mikelepage stems from a hypothetical need for the station to maintain a sun-facing (radial?) orientation. The validity of that need is accepted for the sake of discussion, but is otherwise worthy of its own analysis.

I should mention out that maintaining a sun-facing orientation (for solar power requirements) was only one application I had in mind for a spacecraft which can arbitrarily change its orientation with some rapidity (say, degrees per hour).  I imagine any torus habitat will have dual-use as a structural framework for a solar sail, parabolic dish receiver/transmitter or other large array technology.  These are all applications that would be able to make use of an ability to make relatively rapid orientation adjustments without expending propellent.

Once we get to habitats as large as proposed by Roy_H (r>100m), then sure the ability to change orientation rapidly will become a limiting factor, but for the near-term, where angular momentum remains in the same order of magnitudes as existing amusement park rides, I think we'll get more utility from building something with more dynamic pointing ability.


Offline Paul451

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Re: Realistic, near-term, rotating Space Station
« Reply #1211 on: 09/06/2018 09:03 AM »
I should mention out that maintaining a sun-facing orientation (for solar power requirements) was only one application I had in mind for a spacecraft which can arbitrarily change its orientation with some rapidity (say, degrees per hour).

I'm obviously missing something. If the spin-station is sun-facing (meaning that it keeps its plane of rotation at a constant angle to the sun, radial or tangential, depending on where you hang the solar panels), why do you need "degrees per hour" rotation? The axis of rotation will point in a constant direction relative to the deep background, even if it's in orbit around the Earth. So it only needs to rotate fast enough to match its (or Earth's) rotation around the sun. One degree/day. Are you expecting degrees/hour rates of precession due to internal mass movements?

Offline mikelepage

Re: Realistic, near-term, rotating Space Station
« Reply #1212 on: 09/07/2018 08:03 AM »
I'm obviously missing something.

Uh yeah. :) might want to reread my paragraph that you quoted ;)

In any case, I mentioned that a large toroidal spin habitat may also dual purpose as a structural framework for solar sails, parabolic dishes and other array technologies, and these would be able to make use of a pointing ability more rapid than 360 degrees/year. 

I'm imagining data transfer antennas for a solar system wide internet, or perhaps microwave power transfer.  Anything that needs a large circular antenna.  You don't need incredibly fast turn rates, but you do need rates faster than simply tracking the sun. Point being, if you already have that ability, then tracking the sun as a default for power/thermal management is not as big a deal.

Offline Paul451

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Re: Realistic, near-term, rotating Space Station
« Reply #1213 on: 09/07/2018 01:23 PM »
...

Ah. I had it back'ds. "If you can do the hard thing, the easy thing is easy."

But... why are you doing the hard thing?

Offline mikelepage

Re: Realistic, near-term, rotating Space Station
« Reply #1214 on: 09/13/2018 04:42 AM »
Ah. I had it back'ds. "If you can do the hard thing, the easy thing is easy."

But... why are you doing the hard thing?

Because the hard thing about spin gravity isn't actually the spin gravity.  It's finding a way to pay for it.

It seems unlikely at this point that NASA or any other government agency will fund it, so instead, my thinking is that the path to implementing spin gravity has to go through some intermediate step, where we find a way to generate revenue from small spinning array structures with a different purpose, and then dual-purpose that tech for spin gravity applications.

Because most space applications will require a pointing capability, my hunch is that - once developed for this intermediate application - this will naturally scale to larger spin gravity stations, albeit with much smaller turning rates due to the large angular momentum.

Personally, I think it would be more surprising if a large spinning space station didn't have an ability to control orientation in this way.  Every other spacecraft has to be able to orient itself, and the bigger it is, the more important it is that it doesn't use propellent to do so.  Not sure why this would be an exception to the rule.
« Last Edit: 09/13/2018 04:43 AM by mikelepage »

Online Coastal Ron

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Re: Realistic, near-term, rotating Space Station
« Reply #1215 on: 09/13/2018 05:11 AM »
Ah. I had it back'ds. "If you can do the hard thing, the easy thing is easy."

But... why are you doing the hard thing?

Because the hard thing about spin gravity isn't actually the spin gravity.  It's finding a way to pay for it.

This should be an obvious point, but so often all of us love to only concentrate on the technical challenges (i.e. how to accomplish something), not the business ones (i.e. how to fund the effort).

And certainly one of the things to admire about Elon Musk is that he found paying customers to fund his rocket development efforts. Who will be the Elon Musk of artificial gravity space stations?

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It seems unlikely at this point that NASA or any other government agency will fund it, so instead, my thinking is that the path to implementing spin gravity has to go through some intermediate step, where we find a way to generate revenue from small spinning array structures with a different purpose, and then dual-purpose that tech for spin gravity applications.

I agree that the U.S. Government has shown no interest in artificial gravity, and with the focus on the current lunar Gateway it doesn't look like that will change during this administration.

So I think you are right to take a step back and see if there is a smaller version that would solve an important problem, AND have a source of funding.

Not sure what that is and who would fund it, but I think you're asking the right questions. Kudos!
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Offline aceshigh

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Re: Realistic, near-term, rotating Space Station
« Reply #1216 on: 09/14/2018 01:37 AM »
Found this video. Never realized the Shuttle tanks had to be ACTIVELY de-orbited.

And if NASA wanted, they could have built a huge rotating space station out of the hundreds of Shuttle Tanks that reached LEO.

Or was this totally unfeasible


Offline 1

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Re: Realistic, near-term, rotating Space Station
« Reply #1217 on: 09/14/2018 03:12 AM »
Never realized the Shuttle tanks had to be ACTIVELY de-orbited.

The external tanks were never actively deorbited in a "perform a deorbit burn" sense. "Forced" is a rather poor word choice. Technically, the tank reached a low orbit, but the main engines were shut off when perigee was still low enough that the tanks trajectory intersected the atmosphere. This guaranteed that the tank would immediately reenter. All the tank needed to do was maneuver away from the shuttle. The shuttle, once separated, then used an on board orbital manuvering system to finalize/raise its own orbit. Else, it would have immediately reentered as well. Do a search through the shuttle Q&A threads for more details.
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Or was this totally unfeasible
The shuttle could have brought the tank, as payload, to a useful orbit; but ultimately the tanks were never designed to do anything other than serve as tanks. By all means, send up some better designed hardware. But the claim in the video that they can make a much simpler tank while simultaneously adding a bunch of new hardware is the largest of many things that make this entire proposal smell like fresh fertilizer to me.

Offline Alf Fass

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Re: Realistic, near-term, rotating Space Station
« Reply #1218 on: 09/17/2018 07:38 AM »

And if NASA wanted, they could have built a huge rotating space station out of the hundreds of Shuttle Tanks that reached LEO.


Call me pedantic but there were only a total of 135 shuttle flights.
« Last Edit: 09/17/2018 07:39 AM by Alf Fass »
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Offline Paul451

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Re: Realistic, near-term, rotating Space Station
« Reply #1219 on: 09/17/2018 11:22 AM »
And if NASA wanted, they could have built a huge rotating space station out of the hundreds of Shuttle Tanks that reached LEO.
Call me pedantic but there were only a total of 135 shuttle flights.

And more pedantically, very few that went into the same orbit until the ISS construction.

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