The fuel for Ryland Grace’s starship, the Hail Mary, is Astrophage, a microscopic alien microbe that stores enormous amounts of energy by absorbing it from stars. Grace needed about 2 million units (or doses) of Astrophage because:
- Astrophage is the energy source that powers the ship’s propulsion by releasing stored energy as infrared light.
- The mission requires a huge quantity to generate enough thrust for the long interstellar journey.
- The fuel must be carried in large amounts to sustain the ship’s engine over the entire trip and to have reserves in case of losses (like contamination by Taumoeba).
So, the "2 million" refers to the massive quantity of Astrophage microbes needed as fuel to power the starship across light years.
Sources
Recapy curated
Tap to read source excerpt