CON-1: The horizon: nobody is steering

The pilot's chair is decorative.

Kind: constraint · Family: CON (Control) · Last reviewed: 2026-09-12

The result

A superluminal warp bubble has an event horizon: Hiscock shows a coordinate singularity and horizon form at the wall once the apparent speed exceeds c. Everett and Roman draw the consequence that an observer at the centre of the bubble is causally separated from the outer edge of the wall and can neither create a warp bubble on demand nor control one. Krasnikov shows the leading edge of the bubble matter is spacelike at superluminal speed, so the ship would need tachyons to shape the metric ahead

What it forbids or costs

The pilot's chair is decorative. Control must come from outside, ahead of the bubble

Escape hatches

Subluminal warp drives have no horizon; an external agent along the route (CON-2)

Who it bites

Physics proposals

• VIOLATES: Alcubierre 1994: the warp drive metric. Hiscock finds the horizon at the wall for $v_s > 1$, Everett and Roman draw the consequence that the crew can neither create nor control the bubble, and Krasnikov shows the leading edge of the wall matter is spacelike. All three are results about this metric.
• VIOLATES: Natário 2002: warp drive with zero expansion. Natário derives the horizon at $\|X\| = 1$ and the causal disconnection of the interior from part of the wall for any $X$ with $v_s > 1$, calling it unavoidable; this is CON-1 proved for the class.
• VIOLATES: Van Den Broeck 1999: the pocket geometry. The outer bubble is an Alcubierre bubble with $v_s$ constant and, for $v_s > 1$, the same horizon at the wall; the crew in the pocket are further from the wall in proper distance than in the original, not closer.
• VIOLATES: Warp drives in modified gravity. The horizon at the wall for $v_s > 1$ is a property of the metric; DeBenedictis and Ilijic state that warp drive spacetimes "contain an effective horizon" and that they did not address it. Torsion vanishes outside matter, so nothing in the ship's causal reach changes.
• SATISFIES: Bobrick and Martire 2021: physical warp drives. Its Class III drives carry a Killing horizon by definition and the paper does not claim the interior observer can steer them; its physical class is subluminal and has no horizon, the entry's own escape hatch
• SATISFIES: Everett and Roman 1997: the superluminal subway. The paper is the source of the control argument against the bubble, and the tube is analysed precisely because every modification of the metric "necessarily occurs in the causal future of the launch point of the spaceship". No horizon separates crew from structure.
• SATISFIES: Fell and Heisenberg 2021: positive energy from hidden geometric structure. Concedes that horizons form and "prevent the configurations from transporting an inertial observer from the subluminal regime to the superluminal regime", which is the Everett–Roman conclusion, and leaves open "whether the central vehicle can actually manipulate the energy density"
• SATISFIES: Fuchs et al. 2024: the constant-velocity physical warp shell. Subluminal, so no horizon; the constraint that does apply, $R_{\text{shell}} > 2GM/c^2$, is respected with $2GM/c^2 \approx 6.7$ m inside a 10 m cabin
• SATISFIES: Krasnikov 1998: the tube laid on the way out. The tube was designed so that every change to the metric lies in the causal future of the pilot's decision; there is no horizon between the crew and the structure they build, which is what Everett and Roman mean by saying the tube "does not suffer from the first difficulty".
• SILENT: Lentz 2021: hyper-fast positive-energy solitons. States that at higher speeds "the soliton begins to form horizons" and defers "the horizon problems endemic to this and all other known superluminal solitons" to future computation; the Everett–Roman consequence, that the payload cannot steer, is not engaged
• SILENT: NASA Eagleworks warp field interferometer. Horizons appear once, as a "pseudo-horizon" in the boost plot; control is never discussed
• SILENT: White et al. 2021: the worldline-numerics Casimir pattern. Horizons and control are never discussed

Fictional drives

• SILENT: Campbell's Islands of Space (1931): where the word came from. Everett and Roman's pilot cut off from the wall is Arcot's blind crew aiming before entry, but the novel treats blindness as an optics problem, not a horizon; the constraint is not addressed.
• SILENT: Elite Dangerous: the frame shift drive (Frontier Developments, 2014). The pilot throttles and steers in supercruise at 2001 c; the horizon at the wall of a superluminal bubble is never mentioned.
• SILENT: Futurama: the Planet Express ship's dark matter engines (1999 onward). Leela steers from the pilot's seat in every episode; the horizon that would make the seat decorative is never mentioned.
• SILENT: Star Trek: warp drive (1966 onward). The helm steers at warp in every episode; the horizon at the wall of a superluminal bubble and the loss of control it implies are never mentioned.
• SILENT: Stellaris: warp, hyperlane and wormhole (Paradox Development Studio, 2016). Fleets are steered at warp and through lanes from the map screen; no horizon, no loss of control.
• SILENT: The Orville: quantum drive (2017 onward). The helm steers at quantum speed in every episode; the horizon at the wall of a superluminal bubble is never mentioned.
• ENGAGES: EVE Online: the warp drive (CCP Games, 2003). The lore says a ship at warp can barely see or act, and that navigation had to be solved from outside; this is the control problem stated in the fiction's own terms.
• RULE: Death's End: curvature propulsion (Liu Cixin, 2010). The superluminal horizon does not form because the drive is subluminal, by rule; Wade's ships are piloted from inside without comment.
• RULE: Star Citizen: quantum drive and jump points. The quantum drive is subluminal, so by the entry's own escape hatch no horizon forms and the pilot's chair is not decorative; the game's rule that the pilot must maintain course or the bubble fails is consistent with a bubble the crew can control.

Sources

• Hiscock, Class. Quantum Grav. 14, L183 (1997), arXiv:gr-qc/9707024; Everett and Roman, Phys. Rev. D 56, 2100 (1997), arXiv:gr-qc/9702049; Krasnikov, Phys. Rev. D 57, 4760 (1998), arXiv:gr-qc/9511068 ✓