Gravity in a spherical spaceship?

Question

If you want gravity on a sphere-shaped spacecraft, then is it possible to place a very small but very massive and dense object in the center somehow so that it would be generating a small gravity field of its own? I'm not a physics major or anything so I'm not sure how feasible this is. Thanks for answering.

Answer 1

I'm not sure, but i've also wondered whether it you could use centripetal force as a substitute for gravity, by spinning a disk-like space craft people could walk around the inner outside rim.

Answer 2

If you wanted a comfortable half earths gravity at the surface of the sphere but to save space wanted to fit that into a ball of say 200m diameter the object would have to weigh 750 billion tonnes.

One problem is the gravity gradient.  If the spherical shell of the space craft had multiple layers, you would feel a definite change in gravity as you climbed the stairs from one floor to another.

Another problem is that it would need to be 16,000 times denser than lead.

A torus say of 100m radius would only have to rotate at just over 2 rpm to provide the same artificial gravity.

Answer 3

Sure, but then that massive object becomes part of your spaceship, and you've got to move all that mass when you move your spaceship.

Answer 4

Every object with mass (including you) generates a gravity field, so your idea is theoretically possible.

However, the force of gravity equals GMm/r^2

where G is the universal gravitational constant (6.67 x 10^-11)

the big M is the mass you're standing on

the little m is the mass of you

r is your distance from the center of mass.

To come close to the Earth's gravity, you'd need a huge mass for your spacecraft or a very small spacecraft.

Silenus gave you an accurate number (in metric tonnes which is different than US tons) for a reasonably sized sphere (100 meter radius).  The sphere would have a surface area of 126,000 square meters, or 31 acres.

It's not feasible to obtain a mass that large, or feasible to get a mass large enough for any usable type spacecraft, so the centrifugal force in a ring would by the most feasible method of simulating gravity.

Answer 5

Uh... you just described SPACESHIP EARTH!

Answer 6

Think of the impracticality. Wouldn't it be better to spin the thing and have centrifugal force act as artificial gravity with no increase in mass?

If you did have the center of gravity at one point, it would be almost impossible to complete any meaningful tasks. Everyone in the ship would bu stuck to the same spot.  

Answer 7

IN theory it could work, but the object would have to be large enough to create it's own gravity field.  You're talking about something several miles in diameter.  Then to build a spacecraft around it?  Not my first choice!

Instead check out the movie 2001 A Space Odessy.  Simply take a round object and spin it to create centrifical fource (gravity pushes everything outwards).  As it spins the centrifical force creates artificial gravirty and if at the right rate of rotation, you could have gravity the same as we have here on earth.  Faster it spins the harder it is to walk.  The slower it spins the lighter you become.  

Answer 8

No.

It would be much more reasonable to spin the sphere around its

axis and then centrifugal force would replace gravity. The floor would

become the outside walls of the sphere at the equivalent equator of the sphere, instead of the floor being

down towards the center of the sphere as you had imagined.The amount of mass required to do it your way would preclude ever being

able to launch the space craft out into space...remember, you have to get all that mass from somewhere...