Is $10/kg to LEO Physically Possible?

A Thermodynamic Energy Floor Analysis

Theoretical Minimum Energy to LEO#

To place 1 kg at 400 km altitude in a circular orbit:

At US grid electricity ($0.08–0.10/kWh):

9.5 kWh × $0.10 = $0.95/kg — the theoretical energy floor

Real-World Efficiency Impact#

No launch system operates at 100% efficiency. The gap between theoretical and actual:

Where Does Falcon 9 Sit?#

Falcon 9 burns ~498,000 kg of propellant with a chemical energy content of ~9.4 MJ/kg (RP-1/LOX combustion), delivering 22,800 kg to orbit at 34.1 MJ/kg of orbital energy:

• Total chemical energy input: ~4,680,000 MJ
• Total orbital energy delivered: ~777,000 MJ
• Overall efficiency: ~5–6% from chemical energy to orbital energy

This is not bad engineering — it's the rocket equation. Chemical rockets are thermodynamically constrained by the need to carry their own propellant mass, which itself requires energy to accelerate.

What $10/kg Actually Requires#

At the energy floor of ~$1/kg, a $10/kg total cost means the entire launch infrastructure — vehicle amortization, labor, insurance, operations, overhead, profit — must fit within ~$9/kg of margin.

This is equivalent to delivering freight for the cost of diesel fuel alone — no truck, no driver, no roads, no insurance, no maintenance.

Not physically impossible (the energy floor is well under $10/kg), but it requires launch infrastructure to effectively cost nothing per flight. This means either:

1. Infinite reuse with negligible per-flight refurbishment (no rocket has demonstrated this)
2. Fundamentally different technology that doesn't carry oxidizer and doesn't destroy itself — rail gun, space elevator, launch loop, or similar ground-based acceleration system

Chemical rockets face an inherent disadvantage: they must carry oxidizer mass (typically 2–3× fuel mass), which means ~75% of propellant mass is "wasted" on the oxidizer rather than the energy-carrying fuel. Ground-based electromagnetic systems eliminate this entirely.

SpaceX's $10/kg Claim Examined#

Musk's Stated Math#

• $1.5M total launch cost for 150 tonnes to LEO
• ~$500K in propellant (~1/3 of total)
• ~$1M for "reusability, refurbishment, recovery, transportation"

The Critical Word: "Marginal"#

This is explicitly the marginal cost — the cost of the next flight once all fixed costs are already paid. This excludes:

• ~$200M vehicle build cost amortization
• Billions in pad infrastructure at Starbase
• Thousands of employees
• Range safety and regulatory compliance
• Insurance (at current failure rates)
• Corporate overhead and profit

It's like quoting the marginal cost of a 747 flight as fuel + crew + landing fees while ignoring the $400M airplane and $2B terminal.

The Markup Problem#

$1.5M launch cost with $500K fuel = 3× markup over propellant cost.

Aviation — the most mature, competitive transport industry — achieves 8.3× in a benign environment. SpaceX claims less than half aviation's markup in an environment where engines operate at twice the temperature and 2.5× the pressure.

The Reuse Assumption#

Citi's analysis makes the dependency explicit: $300/kg at 10 reuses, $30/kg at 100 reuses. The $10/kg figure requires hundreds of reuses at high cadence with minimal refurbishment.

No rocket component has demonstrated anything approaching this. Falcon 9 boosters have reached ~30 flights — impressive, but a first-stage booster that never reaches orbital velocity. Starship's upper stage must survive orbital re-entry at ~7.8 km/s, which is a categorically harder problem.

Conclusion#

$10/kg is not physically impossible — the energy floor is ~$1/kg. But it requires the launch vehicle and all supporting infrastructure to contribute essentially zero cost per flight, which requires either a technological paradigm that doesn't exist (non-rocket ground launch) or a degree of reusability and operational efficiency that no transport system in any domain has ever achieved.

The realistic floor for chemical rocketry, even with full Starship-class reusability, is $150–500/kg based on fuel economics and realistic markup analysis. The $10/kg figure is a marginal-cost aspiration that excludes most real costs.