Alternative Launch Systems: Can Any Reach $10/kg?
A Survey of Proposed and Operational Systems
The Complete Landscape#
| System | Type | Projected $/kg | TRL | Status |
|---|---|---|---|---|
| Orbital airship (JP Aerospace) | Buoyancy + propulsion | $0.31/kg | 1 | Fantasy — quoted to Jerry Pournelle |
| Launch loop (Lofstrom) | Electromagnetic | $3–300/kg | 1–2 | Theoretical paper only (1985) |
| Mass driver (Earth-based) | EM rail | <$1 electricity + massive capital | 2–3 | Small demos only, no full-scale prototype |
| Space elevator | Tether climber | $100–500/kg | 1–2 | Requires non-existent materials (CNT ribbon) |
| StarTram Gen 1 | Maglev launch (cargo only) | $20–50/kg | 2 | Conceptual; estimated $60B+ capital cost |
| Starship (Musk target) | Chemical rocket | $10/kg (aspirational) | 5–6 | Flying, not yet reusable |
| Starship (Citi 2040 bull) | Chemical rocket | $33/kg | — | Best-case investment bank projection |
| Starship (Citi 2040 base) | Chemical rocket | $100/kg | — | Mid-case projection |
| Starship (Citi 2040 bear) | Chemical rocket | $300/kg | — | Conservative projection |
| Starship (realistic near-term) | Chemical rocket | $78–94/kg | — | Partial reusability, 6 flights/vehicle |
| Falcon Heavy (current) | Chemical rocket | $1,410/kg | 9 | Operational, partially reusable |
| Falcon 9 (current) | Chemical rocket | $2,720–2,940/kg | 9 | Operational, first stage reusable |
Key Observations#
Only Fantasy Systems Project Below $10/kg#
The only launch concepts claiming sub-$10/kg costs are:
- Purely theoretical — launch loops, orbital airships, mass drivers with no full-scale prototype
- Require non-existent materials — space elevator requires carbon nanotube ribbon at lengths, strengths, and defect densities never demonstrated
- Require enormous capital — StarTram needs $60B+ and a mountain-top maglev track at 22 km altitude
The Space Elevator Comparison Is Devastating#
The space elevator has fundamentally superior physics compared to chemical rocketry:
- No oxidizer — uses grid electricity, so ~75% of propellant mass is eliminated
- No rocket equation — the climber mass fraction problem is dramatically easier
- Continuous operation — no launch windows, weather constraints, or range safety
- Reusable by design — the climber goes up and comes back down
Despite all these advantages, serious engineering estimates for a space elevator land at $100–500/kg — an order of magnitude above Musk's $10/kg target for a system that carries oxidizer, fights the rocket equation, and operates in the most extreme thermal environment of any machine.
If even a space elevator can't reach $10/kg, it's extraordinary to claim a chemical rocket will.
The Launch Loop#
Keith Lofstrom's launch loop (proposed 1985) is the most optimistic credible non-rocket concept. At the low end, it projects $3/kg — but only at:
- $30B+ capital investment
- 6 million tonnes/year throughput (for context, total global launch mass to orbit in 2024 was ~2,000 tonnes)
- Decades to build and commission
- Demand levels that don't exist and may never exist
At more realistic throughput, launch loop costs rise to $100–300/kg.
What This Tells Us About Starship#
Musk claims a chemical rocket — the thermodynamically worst architecture for reaching orbit (carries oxidizer, fights exponential mass ratio, extreme temperatures and pressures) — will achieve costs that even purpose-built electromagnetic ground infrastructure only theoretically matches.
This is not an engineering argument. It's a marketing claim.
The Credibility Gradient#
Arranged by decreasing credibility of the $/kg claim:
- Falcon 9/Heavy current pricing — verified by actual commercial transactions. High confidence.
- Starship at $300/kg (Citi bear) — requires ~10 reuses, which F9 has demonstrated. Plausible within 5–10 years.
- Starship at $100/kg (Citi base) — requires 30–50 reuses with rapid turnaround. Optimistic but within realm of possibility by 2040.
- Starship at $33/kg (Citi bull) — requires 100 reuses of a vehicle not yet reused once. Speculative.
- Starship at $10/kg (Musk) — requires markup ratio no transport industry has achieved, in the harshest operating environment. Aspirational.
- Space elevator at $100/kg — requires materials that don't exist. Decades away if ever.
- Launch loop at $3/kg — requires infrastructure that doesn't exist and demand that doesn't exist. 50+ years.
- Orbital airship at $0.31/kg — not a serious proposal.
Conclusion for Space Datacenter Economics#
$200–500/kg is the practical floor for the 10–20 year timeframe, even assuming everything goes right for Starship reusability. The $10–50/kg figures are marketing numbers, not engineering estimates.
At $200–500/kg, the total launch cost for a 100 MW space datacenter (2–5 million kg) remains $400M–$2.5B — comparable to or exceeding the total cost of a terrestrial facility that comes with easy maintenance, fiber connectivity, and upgrade paths.
The only way to break below $100/kg with confidence requires either non-rocket technology (decades away, if ever) or a reuse cadence for chemical rockets that would itself be a historical first by an order of magnitude.