The Deck I'm currently considering is
8x Space Debris - Place 2 Small Asteroids
4x Huge Chunk - Place 1 Large Asteroid
4x Asteroid Field - Place 3 Small Asteroids
3x Mine Fields - Place 2 Mine Fields
1x Gravity Well - The 1st obstacle you place is a Gravity Well, it must be placed at a point on the center line of the board.
3x Gaseous Clouds - Place 4 Gaseous Clouds on the board.
3x Comet - Place 2 Moving Asteroids on the board. Randomize their starting direction.
2x ComSat - Place 1 Relay Satellite
2x Ion Storm - Place 2 Ionized Gas Clouds
1x Solar Flares – Play the game checking for Solar Activity – Draw another terrain card
Just above 50% of the cards are Asteroids. The average number of objects works out around 6, and as half the cards are 2 it means that most of the time you will get around this number, though in a small amount of situation you will get less or more.