In The cold equations why will the stowawy take seven others with him by staying on board?

In the cold equations, the stowaway's presence aboard the spacecraft jeopordises the success of the mission to deliver a vital medical supply to a dwing colony on the planet Woden. He compromises the the critical balance of the ship's inertia and will cause it to burn up in the atmosphere during re-entry. To save seven lives, the protagonist, Manson, must eject the stowaway into the void.