### **Assessing the Probability of an Astronaut in Cryosleep Dying from Galactic or Stellar Cosmic Rays During a Flight to Alpha Centauri**
The likelihood of an astronaut in cryosleep dying from galactic cosmic rays (GCR) or solar cosmic rays (SCR) during a trip to Alpha Centauri depends on several factors:
### **1. Duration of the Flight**
Distance to Alpha Centauri: ~4.37 light-years.
With current technology (e.g., Breakthrough Starshot at ~20% light speed), the journey would take **~20-25 years**.
### **2. Radiation Levels in Interstellar Space**
- **Galactic Cosmic Rays (GCR)** – High-energy protons and atomic nuclei (mostly from supernovae).
- Flux: **~4 particles/cm²/s** (on average).
- Energy: Up to 10²⁰ eV (but most are ~1-10 GeV).
- **Solar Cosmic Rays (SCR)** – Less dangerous, but solar flares can cause short-term spikes.
### **3. Spaceship Shielding**
- **No shielding**: Radiation dose over 20 years ~ **10-20 Sv** (1000-2000 rad), which is lethal.
- **Basic aluminum shielding (5-10 cm)**: Reduces dose by 2-3x (~5-10 Sv), still dangerous.
- **Advanced shielding (water/plastic shielding, magnetic field)**: Could lower dose to **~1-2 Sv**, increasing cancer risk but not guaranteeing death.
### **4. Cryosleep (Suspended Animation)**
- If metabolism is slowed, radiation damage may accumulate, but repair mechanisms are also inactive.
- Theoretically, DNA damage could be critical upon awakening.
### **Estimated Probability of Death**
- **No shielding**: ~100% (10+ Sv is fatal within years).
- **Basic shielding**: ~50-70% (5-10 Sv causes radiation sickness and cancer).
- **Advanced shielding**: ~10-30% (1-2 Sv increases cancer risk but is not immediately lethal).
### **Conclusion**
If the spacecraft **lacks strong radiation shielding**, the probability of death from cosmic rays is **very high** (>50%). With good shielding (magnetic fields, water barriers), the risk drops to **10-30%**.
For a safe journey, either of the following is needed:
✔ **Artificial magnetic field** (like Earth’s).
✔ **Thick hydrogen-rich shielding** (water, polyethylene).
✔ **Reduced travel time** (under 10-15 years).
Since such technologies are not yet available, the risk remains significant.