Living in Zero G

[Robonoise]

Even though we can all cram into one planet right now, eventually humanity must leave Earth. This now brings up the problem of zero gravity. Zero g sounds like fun and looks like it, but humans were made to withstand gravity. Too long without gravity, the an astronaut couldn’t stand up, at least not without exhausting themself. Some solutions include the Wernher Von Braun artificial gravity wheel, which spins at a speed so that it simulate Earth gravity. Another solution is constantly accelerating to create a gravitational force. One thing is for sure, we must solve these problems before we have to solve them, or who knows if we’ll even get to go to another planet healthy.

[Bill Phil]

24 minutes ago, Robonoise said:

Even though we can all cram into one planet right now, eventually humanity must leave Earth. This now brings up the problem of zero gravity. Zero g sounds like fun and looks like it, but humans were made to withstand gravity. Too long without gravity, the an astronaut couldn’t stand up, at least not without exhausting themself. Some solutions include the Wernher Von Braun artificial gravity wheel, which spins at a speed so that it simulate Earth gravity. Another solution is constantly accelerating to create a gravitational force. One thing is for sure, we must solve these problems before we have to solve them, or who knows if we’ll even get to go to another planet healthy.

Rotation is probably our best bet.

[kerbiloid]

Spoiler

32 minutes ago, Robonoise said:

Zero g sounds like fun and looks like it

especially when you're immune to the sea sickness, while the other crew isn't.

 

[Spacescifi]

1 hour ago, Robonoise said:

Even though we can all cram into one planet right now, eventually humanity must leave Earth. This now brings up the problem of zero gravity. Zero g sounds like fun and looks like it, but humans were made to withstand gravity. Too long without gravity, the an astronaut couldn’t stand up, at least not without exhausting themself. Some solutions include the Wernher Von Braun artificial gravity wheel, which spins at a speed so that it simulate Earth gravity. Another solution is constantly accelerating to create a gravitational force. One thing is for sure, we must solve these problems before we have to solve them, or who knows if we’ll even get to go to another planet healthy.

 

Rotational gravity is a simple concept, but how one implements it matters more. There are two ways I will discuss, radial rotation (rolling) and tumbling rotation (pitch).

Radial Rotation:

This is the what most think of when they think of rotational gravity. Yet it has some challenges. As you know, all the weight in the torus is pulled toward the perimeter, thus the walls must be strong enough to support that weight at 1g if that is the gravity desired. It is arguably cheaper to strengthen the walls with heavy material, but spaceships must be lightweight, so some lightweight but strong and expensive material would likely be used instead. Also, larger radius rings are ideal for gravity, as smaller radius ones just are'nt due to disorientation. Yet larger radius often requires more mass, and once again we are confronted with the long drawn  out process of orbital construction, since lifting something that heavy all at once is not economical.

Tumbling rotation: what I like is that only the rear and front sections of a rocket need to be strengthened, since the middie will be zero g during rotation anyway. So less hull reinforcement is required I believe, leading to cheaper and more readily produced rotational gravity.

Even if built in orbit it not need be a 100 meters radius, only a length of about a 100 meters.

Edited October 18, 2019 by Spacescifi

[KSK]

Just to throw in some real world numbers here.

The London Eye is a 120m diameter Ferris wheel. It consists of a wheel (of course), with 32 capsules attached to its outer rim. Each capsule weighs 10 tonnes, total weight of capsules plus wheel is 2100 tonnes. Therefore the wheel has a mass of 1780 tonnes. It is quite clearly capable of supporting it's own mass at 1g and it can also support the additional mass of those capsules again, under 1g.

Mass of the International Space Station is approximately 420 tonnes. So the London Eye wheel has approximately the same mass as four International Space Stations. Assuming (and this is a big assumption but it'll do as an example of present day technology) that SpaceX get their Starship to work and that it's able to lift its projected 100 tonnes to LEO, it would take 18 Starship flights to lift the necessary payload to construct a 120m diameter wheel in space that would be capable of spinning quickly enough to generate 1g at the circumference. plus additional flights to lift the habitation modules and everything else that goes into a working space station, of course. 

Other rockets (currently at various stages of development) would also be options. I'm picking SpaceX because it's easier to see how much progress they're making and they're explicitly aiming at a fully reusable heavy-lift vehicle, which should make a large scale project like this more economically viable.

Yes, orbital construction will be required. I believe it would be required for a 100m tumbling tube station as well, since I'm not aware of any rocket that would be capable of launching a 100m long single piece of payload. As a point of comparison, the Saturn V was around 120m long. Mass isn't necessarily an issue here, its more the fact that you'll be launching an extremely tall, spindly rocket, or going for a novel design with some serious strap-on boosters and a minimal sustainer stage to get that payload to orbit.

Besides, the International Space Station has shown that building long, multipart structures in space is entirely possible. The ISS main truss is quite the construction.

TL: DR. I believe that building sizeable wheel design space stations is quite possible with current technology and current generation  lift capacity. Why bother? Because a wheel design offers significantly more habitable space than a tumbling tube design, where the available floor space is limited by the diameter of the tube.

Edited October 19, 2019 by KSK

[Spacescifi]

48 minutes ago, KSK said:

Just to throw in some real world numbers here.

The London Eye is a 120m diameter Ferris wheel. It consists of a wheel (of course), with 32 capsules attached to its outer rim. Each capsule weighs 10 tonnes, total weight of capsules plus wheel is 2100 tonnes. Therefore the wheel has a mass of 1780 tonnes. It is quite clearly capable of supporting it's own mass at 1g and it can also support the additional mass of those capsules again, under 1g.

Mass of the International Space Station is approximately 420 tonnes. So the London Eye wheel has approximately the same mass as four International Space Stations. Assuming (and this is a big assumption but it'll do as an example of present day technology) that SpaceX get their Starship to work and that it's able to lift its projected 100 tonnes to LEO, it would take 18 Starship flights to lift the necessary payload to construct a 120m diameter wheel in space that would be capable of spinning quickly enough to generate 1g at the circumference. plus additional flights to lift the habitation modules and everything else that goes into a working space station, of course. 

Other rockets (currently at various stages of development) would also be options. I'm picking SpaceX because it's easier to see how much progress they're making and they're explicitly aiming at a fully reusable heavy-lift vehicle, which should make a large scale project like this more economically viable.

Yes, orbital construction will be required. I believe it would be required for a 100m tumbling tube station as well, since I'm not aware of any rocket that would be capable of launching a 100m long single piece of payload. As a point of comparison, the Saturn V was around 120m long. Mass isn't necessarily an issue here, its more the fact that you'll be launching an extremely tall, spindly rocket, or going for a novel design with some serious strap-on boosters and a minimal sustainer stage to get that payload to orbit.

Besides, the International Space Station has shown that building long, multipart structures in space is entirely possible. The ISS main truss is quite the construction.

TL: DR. I believe that building sizeable wheel design space stations is quite possible with current technology and current generation  lift capacity. Why bother? Because a wheel design offers significantly more habitable space than a tumbling tube design, where the available floor space is limited by the diameter of the tube.

 

I agree that a torus is better for a station, but for a ship I think a long rocket is better. With current technology it would be more reasonable to do orbital construction of it rather than make it an SSTO (otherwise it will be nearly all fuel tank).

The main benefits of a linear tumbling spacecraft spaceship is I think is that it's arguably cheaper than a torus since the mid section need not be as strong as the rest of the ship. Also easier to construct in orbit. The ISS is basically a bunch of long cylinders attached/docked together after all, so it is virtually the same design.

[KSK]

Hmmm, is that right though? The mid section is still under tension after all and I can't immediately see why it doesn't need to be as strong as the end sections. 

And to me, the ISS is more of a cross shape - truss in one direction, chain of cylinders in the other. Not that it's important for this discussion - just means that we've got experience with both truss designs and string-of-cylinder designs. Two lots of construction for the price of one - bonus!  

[Spacescifi]

1 hour ago, KSK said:

Hmmm, is that right though? The mid section is still under tension after all and I can't immediately see why it doesn't need to be as strong as the end sections. 

And to me, the ISS is more of a cross shape - truss in one direction, chain of cylinders in the other. Not that it's important for this discussion - just means that we've got experience with both truss designs and string-of-cylinder designs. Two lots of construction for the price of one - bonus!  

 

What I mean is that it need not be heavy.

For what it's worth, you could even put a few metal rafter beams to connect fore and aft and forget about a mid-hull section altogether if you want maximum affordabilty.

Then it really would be lighter weight than the rest of the ship.

On the other hand, if you want the mid-section to hold cargo (smart place to put cargo by the way), then definitely put it in a hull midsection.

Edited October 19, 2019 by Spacescifi

[KSK]

33 minutes ago, Spacescifi said:

What I mean is that it need not be heavy.

For what it's worth, you could even put a few metal rafter beams to connect fore and aft and forget about a mid-hull section altogether if you want maximum affordabilty.

Then it really would be lighter weight than the rest of the ship.

On the other hand, if you want the mid-section to hold cargo (smart place to put cargo by the way), then definitely put it in a hull midsection.

Okay - that's not what you said though. 

And yes - take that idea to its logical conclusion and you end up with the tether concept - two spacecraft tethered by a cable rotating about their common centre of gravity mass.

Edited.

Edited October 19, 2019 by KSK

[Spacescifi]

4 hours ago, KSK said:

Okay - that's not what you said though. 

And yes - take that idea to its logical conclusion and you end up with the tether concept - two spacecraft tethered by a cable rotating about their common centre of gravity mass.

Edited.

 

Cables is as cheap/lightweight as you can possibly go.

I remember a rotational gravity experiment I read about that occurred in space once. The cable snapped!

Now I am not saying that will always happen, but I would rather do 30 launches for orbital assembly with beam connectors for both ends of the ship, instead of 19 with cables that might snap.