Scenario

[BlackBolt]

Yet another involving the still mysterious black holes...
I created one with the mass of 100M suns and 59000km diameter. Real time setting (1 second).
The nearby moons accelerated towards it relatively slow, then when they got very close they were blasted away on a deviated course at unbelievable speeds, including a much smaller black hole. I thought they were supposed to "combine"? It even attracts Rigel at 90M km from it with a steady speed of 0.1M km/sec
p.s. I see another more distanced black hole collided with the super main one after I increased it's velocity to 10M km/sec.
p.p.s. it.. engulfed Rigel. It has its size now...

My question is why where the other bodies blasted away?

[Dan Dixon]

That really sounds like the time step was set too high. Also be sure that your collision mode is set to combine. (Right click to open the control panel; Collision Mode is under System Properties)

And you point out an inaccuracy... If a Rigel sized star was swallowed by a black hole it wouldn't dramatically increase in size like it currently does. Something to add to the list of things to fix.

Does that help? Please ask again if my answer was unsatisfying.



The 1st question in the FAQ addresses the time step issue:

Why does Mercury get thrown out of the Solar System when I turn up the time step?
- As you turn up the time step you lower the accuracy of the simulation. If the accuracy is too low bodies will get thrown out of the system.
- The numbers: Mercury takes about 88 days to make a single orbit around the sun. A time step of 22 days would only be calculating a new position for Mercury 4 times in that period. This isn't enough accuracy to maintain a stable orbit. The Earth is further out and takes 365 days to orbit the sun. This same time step of 22 days results in about 16 position calculations for the Earth which is enough to maintain an orbit.

http://universesandbox.com/about/faq.htm

[BlackBolt]

Why aren't the bodies in the program spherical?
And how can I put an object into orbit of another object without tweaking the numbers a long time?
p.s. I can't find a way to open a xml file, for example the SgrA black hole..
Oh, also, a "add texture" feature to a body would be neat

[Dan Dixon]

Why aren't the bodies in the program spherical?

Are you asking why some appear to have flat sides or shaped like stop signs?

All 3D spheres are actually made up of hundreds of flat triangles. In order to improve the apparent smoothness of a sphere you have to increase the number of flat sides which can effect the program's performance. This is on the list of annoyances to correct.

And how can I put an object into orbit of another object without tweaking the numbers a long time?

Here's info on the different ways to create orbits:
http://universesandbox.com/forum/index.php/topic,5.0.html

p.s. I can't find a way to open a xml file, for example the SgrA black hole..

Sorry... That's not clear is it? Put the file here to open it in Universe Sandbox.
My Documents\Universe Sandbox\Systems

Oh, also, a "add texture" feature to a body would be neat

Great idea and on this list.

[BlackBolt]

Sorry... That's not clear is it? Put the file here to open it in Universe Sandbox.
My Documents\Universe Sandbox\Systems

Yeah, thanks for clearing that up. I don't usually use My documents, so it wasn't more intuitive than the program's installation folder.