⚫ Take an object and spin it fast enough, and you get artificial gravity. It's possible to get enough to equal Earth's gravity, but it requires a quick spin.

There are all sorts of weird side effects and some massive engineering issues, like making sure whatever you're spinning is strong enough not to break.

You can experience the effects at most fairgrounds. Many games create artificial gravity, and some create enough to at least partially counter normal gravity.

There are two ways we currently have to simulate gravity in a spaceship that we can build differently.

The first and easiest technique is to simply accelerate your ship in the direction of travel at whatever speed gives you the effect you need. This has the advantage of simplicity, as you simply build your ship as if you were always sitting on the launch pad, and only experience zero G at the midpoint of your trip when you rotate it 180 degrees and start an equal deceleration burn for that you arrive at your destination at a good orbital velocity. There's only one small problem with this simple and elegant solution, and that's the fact that we don't have any drive system remotely capable of giving a significant acceleration effect over anything other than extremely short distances. Interplanetary travel using this method is totally out of the question until we come up with something that is orders of magnitude more effective than anything on the drawing boards. (If we had such a drive system available, we could also get speeds up to a serious fraction of the speed of light, which would be amazing.)

That leaves the second option as the only viable solution, where the acceleration effect is not provided by the drive system, but by a rotation vector that allows an equivalent of gravity to be experienced on the outer walls of the vessel. This is also a simple solution, but it has some inherent problems with the concept. When you use centripetal acceleration as a means of simulating normal gravity, you are committing to building a substantial structure to avoid negative effects such as different "G" forces at different distances from the center of rotation and the application of Coriolis forces on the objects within.

Studies have shown that anything with a radius of less than 100 m or a speed of more than 3 rpm produces significant dizziness that debilitates most people. If the ship has a radius greater than 500 m, or a rotation rate of less than 1 rpm, most people are perfectly comfortable, since the adverse variable "G" and Coriolis effects are diffuse enough to then.

This makes your design quite difficult if you want to get somewhere quickly without really great engines, since your ship is now at least 1 km in diameter and weighs thousands of tons. However, it's quite workable if you're not in a rush or just want an orbital habitat that looks like this;

https://qph.cf2.quoracdn.net/main-qimg-7913d5ae5821767fc51d6a8c61d50222-lq

You wouldn't want to build something like this though;

https://qph.cf2.quoracdn.net/main-qimg-f16db03f1baeccca3b2f65160801cfbd-lq

The cleaning bill would be horrible, and your astronauts wouldn't be very useful since they'd spend most of their time with their heads in the bathroom.

A useful equation is the following;

This is the formula used to calculate how big the boat needs to be and how fast it needs to turn to achieve the desired gravity. T = period of time required for one complete revolution, R = radius of the rotating section of the spacecraft and a = the generated acceleration (9.8 m/s2 equals 1G).

There is another way to achieve rotational gravity without building huge structures, and that is to use conventional spacecraft linked together by a truss or cable, and "spin" them to provide the same effect as a huge wheel or cylinder. You end up with something that looks like this;

https://qph.cf2.quoracdn.net/main-qimg-e175dea9c42cdca27b1f5ebff6e55f76-lq

It might not look pretty, but it provides artificial gravity without outrageous amounts of mass. It can be a bit unwieldy in terms of course correction and navigation, but I can see a layout where the control thrusters and navigation sensors are located "center" and use a computer to compensate for rotational speed. .

Until we invent some still mythical impulse that has a specific impulse in millions of seconds instead of just hundreds of seconds, it seems that spinning things is the only practical way to do it.

Every spaceflight mission has been a compromise. They consist of months of trade-offs as mass, cost, and capabilities are reduced to meet not what we want to do, but what can be done with available funds.

It would be a good idea to build a large rotating section of the spacecraft going to Mars, so that parts of the spacecraft can have simulated gravity to help the crew maintain better physical condition. But I'd be surprised if someone who writes the check to go to Mars, whether government or commercial, would be willing to spend the extra money to do such a thing.

If it does, it's probably because the Mars mission was delayed long enough that the technology has been developed for other programs and can be reused with much less research and development cost.

With each increment of the ISS, we learn more about how to ameliorate the negative effects of microgravity on the body. By the time we can go to Mars, we may have learned enough that much less expensive nutrition and exercise protocols can produce the same effects as simulated gravity. Remember that such a spacecraft would have to be extremely large to produce 1 g effects. It's more realistic for us to build one that more closely reflects the gravity of 1/3g of Mars.

⚫ the article claims to use massive asteroids as a home;

One of the dumbest things in science fiction is that all spaceships are built. There's no reason to make spaceships streamlined, no reason to make them at all. It's much better to empty an asteroid

This has numerous benefits:

⚫ You don't have to put all that mass into orbit.

⚫ You have the best camouflage in the galaxy: if you don't want to be seen, one of the best ways is to travel in an almost black ship that looks like a natural object, because it is a natural object.

⚫ Asteroids are mostly metal, that's useful for building things.

⚫ Metals are excellent at absorbing radiation, and space is full of radiation.

⚫ If you need to slow down when you reach a planet, you can glide through the atmosphere. You will lose some metal from the outside, but you probably have more.

⚫ There are minerals and water and other goodies on some asteroids that will come in handy.

⚫ Asteroids are almost comically common. Our asteroid belt has about 1.9 million asteroids larger than 1 kilometer in diameter (that's a big ship) and millions and millions more that are smaller.

⚫ You can use that additional material as a reaction mass. Essentially you can throw it out the back to make your ship go faster. Nice.

⚫ You can spin them and create artificial gravity inside.

⚫ Launching smaller ships from the surface is easy, since the total gravity of the asteroid is practically zero.

All those asteroids you see on Google News… Those could be alien spacecraft. Watch the heads of conspiracy theorists explode over that!

the downside is that they are scattered in billions of cubic kilometers around the solar system. Most of them can't be used for construction, being just a loose collection of small rocks and dust, with a bit of water.

Asteroids are not very strong, even metallic asteroids are very weak with large inclusions of non-metals.

They do not support compression or tension efforts well.

It will look like a large rock (say, a few kilometers in circumference), like the other 150 million asteroids in the system.

Outside, at least. Inside, it will look like this:

https://qph.cf2.quoracdn.net/main-qimg-935dfe842db825142c9430f416350d6c-lq

Or this:

https://qph.cf2.quoracdn.net/main-qimg-c7bf1f8dfe48d4b337b27e0f57867a95-lq

Oh well… many possibilities. The sky will be faked, of course, and light will be generated or reflected. But other than that, it will be a natural ecosystem. The real constraints are that the ecosystem has to be self-sustaining, just like, well, Earth's is. And it's all going to cover only a few square kilometers, so it puts some restrictions on it as well (expect only a few tens of meters of "ocean" on your tropical beach).

Also, the rock itself will be festooned on the surface with robots and sensors, probably a good-sized fusion plant, and most likely a line of rockets, taking up half the circumference.

So it looks more like this...

https://qph.cf2.quoracdn.net/main-qimg-37f23d71419e6b08f0035f3d15c8ba6d-pjlq