---
type: claim
domain: space-development
description: "A magnetically levitated iron pellet stream forming a ground-to-80km arch could launch payloads electromagnetically at operating costs dominated by electricity rather than propellant, though capital costs are estimated at $10-30B and no prototype has been built at any scale"
confidence: speculative
source: "Astra, synthesized from Lofstrom (1985) 'The Launch Loop' AIAA paper, Lofstrom (2009) updated analyses, and subsequent feasibility discussions in the space infrastructure literature"
created: 2026-03-10
---

# Lofstrom loops convert launch economics from a propellant problem to an electricity problem at a theoretical operating cost of roughly 3 dollars per kg

A Lofstrom loop (launch loop) is a proposed megastructure consisting of a continuous stream of iron pellets accelerated to *super*-orbital velocity inside a magnetically levitated sheath. The pellets must travel faster than orbital velocity at the apex to generate the outward centrifugal force that maintains the arch structure against gravity — the excess velocity is what holds the loop up. The stream forms an arch from ground level to approximately 80km altitude (still below the Karman line, within the upper atmosphere). Payloads are accelerated electromagnetically along the stream and released at orbital velocity.

The fundamental economic insight: operating cost is dominated by the electricity needed to accelerate the payload to orbital velocity, not by propellant mass. The orbital kinetic energy of 1 kg at LEO is approximately 32 MJ — at typical industrial electricity rates, this translates to roughly $1-3 per kilogram in energy cost. Lofstrom's original analyses estimate total operating costs around $3/kg when including maintenance, station-keeping, and the continuous power needed to sustain the pellet stream against atmospheric and magnetic drag. These figures are theoretical lower bounds derived primarily from Lofstrom's own analyses (1985 AIAA paper, 2009 updates) — essentially single-source estimates that have not been independently validated or rigorously critiqued in peer-reviewed literature. The $3/kg figure should be treated as an order-of-magnitude indicator, not an engineering target.

**Capital cost:** Lofstrom estimated construction costs in the range of $10-30 billion — an order-of-magnitude estimate, not a precise figure. The system would require massive continuous power input (gigawatt-scale) to maintain the pellet stream. At high throughput (thousands of tonnes per year), the capital investment pays back rapidly against chemical launch alternatives, but the break-even throughput has not been rigorously validated.

**Engineering unknowns:** No Lofstrom loop component has been prototyped at any scale. Key unresolved challenges include: pellet stream stability at the required velocities and lengths, atmospheric drag on the sheath structure at 80km (still within the mesosphere), electromagnetic coupling efficiency at scale, and thermal management of the continuous power dissipation. The apex at 80km is below the Karman line — the sheath must withstand atmospheric conditions that a true space structure would avoid.

**Phase transition significance:** If buildable, a Lofstrom loop represents the transition from propellant-limited to power-limited launch economics. This is a qualitative shift, not an incremental improvement — analogous to how containerization didn't make ships faster but changed the economics of cargo handling entirely. The system could be built with Starship-era launch capacity but requires sustained investment and engineering validation that does not yet exist.

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Relevant Notes:
- [[launch cost reduction is the keystone variable that unlocks every downstream space industry at specific price thresholds]] — a Lofstrom loop would cross every activation threshold simultaneously
- [[power is the binding constraint on all space operations because every capability from ISRU to manufacturing to life support is power-limited]] — Lofstrom loops transfer the binding constraint from propellant to power, making energy infrastructure the new keystone
- [[the space launch cost trajectory is a phase transition not a gradual decline analogous to sail-to-steam in maritime transport]] — the Lofstrom loop represents a further phase transition beyond reusable rockets
- [[orbital propellant depots are the enabling infrastructure for all deep-space operations because they break the tyranny of the rocket equation]] — propellant depots address the rocket equation within the chemical paradigm; Lofstrom loops bypass it entirely, potentially making depots transitional infrastructure for Earth-to-orbit (though still relevant for in-space operations)

Topics:
- [[space exploration and development]]
