Starcloud

Cooling and Thermal Physics

• Main technical objection: in space there’s no convection or conduction; all waste heat must be radiated, needing enormous radiator area.
• Multiple comments argue the required radiators for multi‑GW loads would be kilometers across, comparable in size to the solar arrays; others show back‑of‑envelope math suggesting radiators can be similar or somewhat smaller than panels if run hot.
• Cooling complexity grows with heat transport from dense compute to lightweight radiators; pumping losses and temperature gradients are non‑trivial.
• Comparisons with ISS/JWST emphasize that existing systems dump only kilowatts–megawatts, not gigawatts, and are designed/operated very differently from cost‑sensitive data centers.

Power, Economics, and Scale

• Many argue equivalent or better economics from desert/Arctic/ocean‑cooled terrestrial data centers plus large solar farms, without launch costs or space hazards.
• Whitepaper numbers (e.g., $5M to launch a 40MW cluster, $30/kg to orbit, 10x cheaper energy) are widely viewed as extremely optimistic and dependent on unproven future launch costs.
• The proposed 4km × 4km, 5GW structure is orders of magnitude larger than anything built in orbit; some call it essentially sci‑fi.

Radiation, Reliability, and Maintenance

• Concerns about cosmic radiation causing bit flips across RAM, caches, registers, and logic; standard ECC helps but doesn’t eliminate issues.
• Space‑rated, hardened hardware tends to be old‑node, low‑density, eroding performance/efficiency benefits.
• Physical maintenance, upgrades, and part replacement in orbit are seen as prohibitively difficult and risky at data‑center scale.

Latency, Orbits, and Debris

• GEO implies ≥200ms RTT, acceptable only for limited workloads; LEO reduces latency but introduces eclipses, changing ground tracks, and more complex networking.
• Huge radiators/arrays greatly increase cross‑section for micrometeoroids and debris, raising Kessler‑syndrome concerns, though some argue overall orbital volume makes risk manageable.

Environment and “Green” Claims

• “Only energy is the launch” and “10x CO₂ savings” are viewed as greenwashing: manufacturing, launches, and eventual obsolescence all have large footprints.
• Water‑use avoidance is questioned; data‑center water issues are seen as local/regulatory, not fundamental physics, and often solvable on Earth.

Hype, Viability, and Alternatives

• Strong sentiment that this is bubble‑era hype or a fundraising vehicle (“AI in space”) rather than a near‑term practical plan.
• Timeline claims like “nearly all new data centers in space within 10 years” are mocked as implausible.
• Some see niche potential (e.g., high‑security or government imaging workloads) long‑term, but most favor investing in better terrestrial cooling, new semiconductor tech, or underwater/Arctic solutions instead.