On number 1, one thought that comes to mind is to iterate through 3D space in blocks, rather than simply randomly generating X, Y and Z values, and deciding whether within each block you will place asteroid or a planet or nothing at all..  Think of dividing the 3D space in the game into 6 blocks along each axis, X, Y and Z.  This ends up with 216 (6x6x6) different blocks or sectors in 3D space.

You could use an approach like this along with random number generation that identifies a specific number of those blocks to place asteroids and planets within.  Or, going the other way, you could simply iterate through ALL of those blocks in a nested loop, and use a random percentage within each one to decide whether to place an asteroid or a planet or nothing at all in that block of space.

The latter would be a lot more unpredictable, and I suspect would end up with sometimes quirky results because it's based on a random percentage at each of many points in space. 

I've attached a program that demonstrates the first approach - I threw it together quickly, but I think it does work to pick 10 random "sectors" or space, and of course from that one could place asteroids or planets in those 10.    

Here's how the code looks:

 

Program PickRandomSectors

 

      Method Main()

 

            Define SelectedSectors As IntegerList

           

            Define DoneGeneratingObjects As Boolean = False

           

            Define RandomSector As Integer

           

            Define Index As Integer

           

            Define SectorCoordinateX As Integer

            Define SectorCoordinateY As Integer

            Define SectorCoordinateZ As Integer

 

            While Not DoneGeneratingObjects

           

                  RandomSector = Random(0, 215)

                 

                  If Not SelectedSectors.Contains(RandomSector) Then

                        SelectedSectors.Add(RandomSector)

                  End If

                       

                  If SelectedSectors.Count = 10 Then             

                        DoneGeneratingObjects = True

                  End If

                 

            End While

 

            For Index = 1 To SelectedSectors.Count

                 

                  // Now we need to turn a value from 0 to 215 into three different values to identify

                  // the particular sector along the X, Y and Z axes

                  SectorCoordinateX = (SelectedSectors.Item(Index) / 36)  // 0 to 5

                  SectorCoordinateY = ((SelectedSectors.Item(Index) - (36 * SectorCoordinateX)) / 6)

                  SectorCoordinateZ = SelectedSectors.Item(Index) Mod 6

                 

                  PrintLine( SelectedSectors.Item(Index) )

                  PrintLine( "   (" + SectorCoordinateX + ", " + SectorCoordinateY + ", " + SectorCoordinateZ + ")")

                 

            Next

           

      End Method

 

End Program