CON-2: The bootstrap problem

A warp drive cannot be created from the ship on a first flight.

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

The result

The bootstrap problem. Krasnikov: the traveller cannot hasten reaching the destination on a first flight, because the metric ahead cannot be created without tachyonic matter; the same effect can be had without tachyons only by placing devices along the way in advance. Coule: the Alcubierre spacetime is impossible to set up without first distributing matter at tachyonic speed, "you need one to make one"

What it forbids or costs

A warp drive cannot be created from the ship on a first flight. Warp travel is infrastructure, like a railway, laid at sublight speed

Escape hatches

The Krasnikov tube (CON-3), which accepts this and makes the return trip fast. Coule allows that over small distances, where the energy conditions can perhaps be violated, one might open the light cones locally

Who it bites

Physics proposals

• VIOLATES: Alcubierre 1994: the warp drive metric. Krasnikov and Coule show, for this metric, that the disturbance ahead of the ship cannot be created from the ship on a first flight without tachyonic matter; Alcubierre's itinerary has the disturbance "first appear" at the ship, which is the step that fails. The escape is to lay devices along the route in advance.
• VIOLATES: Natário 2002: warp drive with zero expansion. Given the horizon, the field $X$ ahead of a superluminal bubble is outside the crew's future light cone and cannot be created from the ship; Krasnikov's spacelike leading edge argument is about the location of the wall matter, which is the same for any profile.
• VIOLATES: Van Den Broeck 1999: the pocket geometry. The paper acknowledges that part of the energy in the bubble is moving tachyonically (citing Krasnikov and Coule) and explicitly leaves the problem for future work; the pocket must therefore be laid along the route or sourced by tachyons.
• VIOLATES: Warp drives in modified gravity. The wall matter's leading edge is spacelike for $v_s > 1$ regardless of what sources it (Krasnikov's argument is about where the stress-energy is, not what it is), so the drive must be laid along the route in advance in these theories too.
• DODGES: Brane-bulk shortcuts (Chung and Freese 2000, Ishihara 2001, Caldwell and Langlois 2001). In the cosmological case the brane bending is supplied by matter already everywhere, so no route is laid; an engineered shortcut between chosen points would need the brane bent along the way in advance by mass placed at sublight speed, which is the bootstrap CON-2 describes, and Caldwell and Langlois find the local effect negligible.
• SATISFIES: Bobrick and Martire 2021: physical warp drives. The paper's central conclusion is the entry's: a warp drive is an inertially moving shell, "there is no known way of accelerating a warp drive beyond the speed of light"; no self-consistent accelerating solution exists in the literature
• SATISFIES: ER = EPR (Maldacena and Susskind 2013). Bridges cannot be created by local operations and classical communication; a bridged pair must be created together and separated at sublight speed, which is the wormhole form of CON-2's rule that the route is laid in advance.
• SATISFIES: Everett and Roman 1997: the superluminal subway. The one-way trip is limited by "all the usual restrictions of special relativity"; the tube is laid on the outbound leg and used on the return. The bootstrap is accepted as the design.
• SATISFIES: Gao, Jafferis and Wall: traversable wormholes via a double-trace deformation (2017). The two-sided coupling must be set up and switched on before anything can cross, and the traversal arrives after the coupling's own classical signal; the route is infrastructure laid in advance, as CON-2 demands.
• SATISFIES: Krasnikov 1998: the tube laid on the way out. CON-2 is Krasnikov's own theorem: the first flight cannot be hastened without tachyons, and the same effect without tachyons needs devices laid along the way. The proposal respects the constraint by construction.
• SATISFIES: Maldacena, Milekhin and Popov: traversable wormholes in four dimensions (2018), and the humanly traversable sequel (2021). The mouths must be brought together, connected and then separated at sublight speed, and the outside path stays faster; the paper accepts that it offers no way to create the configuration, which is CON-2's demand accepted rather than evaded.
• SATISFIES: Morris, Thorne and Yurtsever: the wormhole time machine (1988). The far mouth is placed and then moved at sublight speed; the paper accepts that the machine is infrastructure assembled in advance, which is CON-2's demand.
• SATISFIES: Morris–Thorne traversable wormhole (1988). The paper accepts that the far mouth is moved into place at sublight speed by the builders; the route is infrastructure laid in advance, which is CON-2's demand.
• SATISFIES: Visser's thin-shell wormholes (1989). The construction identifies two regions and says nothing about how; as a route the far mouth is delivered sublight in advance, which is CON-2's demand accepted.
• SILENT: Fell and Heisenberg 2021: positive energy from hidden geometric structure. Sketches acceleration by redistributing shell energy front to back and never asks who does the redistributing ahead of the bubble or how the shell is laid
• SILENT: Lentz 2021: hyper-fast positive-energy solitons. No creation mechanism; the conference reply lists "the identification of a creation mechanism" as an open challenge and admits every accelerating drive in the literature violates covariant conservation
• SILENT: NASA Eagleworks warp field interferometer. How a bubble is created or laid ahead of a craft is never discussed; the mission-planning section treats the field as a subsystem switched on at will
• SILENT: White et al. 2021: the worldline-numerics Casimir pattern. The bubble is to be fabricated in place, which is the entry's point, but the paper never addresses how a bubble would be made to move or what lies ahead of it

Fictional drives

• SILENT: Asimov's Foundation: the Jump through hyperspace (1942 onward). The Jump needs no route laid in advance: Trevize Jumps into unexplored space in Foundation's Edge, and the series never asks whether a first flight is possible without infrastructure.
• SILENT: Banks's Culture: the energy grid, infraspace and ultraspace (1987 onward). Ships go anywhere with no route laid; the bootstrap is never raised.
• SILENT: Battlestar Galactica: the FTL jump (2004 series). Jumps go to any calculated point with nothing laid in advance, which is the opposite of what CON-2 allows; the series does not raise it. The Red Line is a limit on calculation, not on infrastructure.
• SILENT: Campbell's Islands of Space (1931): where the word came from. The ship's first flight goes anywhere with no route laid; the bootstrap is never raised.
• SILENT: Commonwealth: CST wormholes with trains through them (Hamilton 2004). The fiction's premise is the reverse of what CON-2 allows: wormholes are opened from one end to unvisited destinations, with nothing laid in advance. The problem is never noticed; the only stated limit is range.
• SILENT: Doctor Who: the TARDIS and the time vortex. The ship works from anywhere on its first flight with nothing laid along the route; the bootstrap problem is never raised.
• SILENT: Dune: the Guild navigators and folding space (Herbert 1965). Guild ships go where they are asked without any pre-laid route; the novel never addresses whether the far end must be prepared, and the navigator's foresight is the only stated prerequisite.
• SILENT: Elite Dangerous: the frame shift drive (Frontier Developments, 2014). Supercruise and jumps work on first arrival in unexplored systems, which the game rewards; nothing is laid ahead and the bootstrap problem never arises.
• SILENT: Event Horizon (1997): the gravity drive. The gateway is created from the departure end with nothing placed at Proxima Centauri in advance, which is the bootstrap the entry forbids, and the film gives no route-laying step. The ship's arrival somewhere unintended is consistent with an unaimed gate but is never argued that way.
• SILENT: Futurama: the Planet Express ship's dark matter engines (1999 onward). The ship flies wherever a delivery is needed with nothing laid ahead; the bootstrap problem never arises.
• SILENT: Halo: slipspace and the Shaw-Fujikawa translight engine (2001 onward). The human drive jumps anywhere on a first flight with no route laid; the bootstrap is never raised. Forerunner portals are infrastructure, but they are the L3 secondary and the human drive does not need them.
• SILENT: Niven's Known Space: the Outsider hyperdrive and the blind spot (1966 onward). The drive goes anywhere on a first flight and needs no route laid; the bootstrap is never raised.
• SILENT: Space Battleship Yamato: warp by wave motion engine. Warps are made from a standing start into unsurveyed space with nothing laid along the route; the bootstrap is never raised.
• SILENT: Star Trek: warp drive (1966 onward). Warp works on first flights to unexplored space by definition of the show's premise; nothing is laid along the route and the bootstrap problem never arises.
• SILENT: Starfield (2023): the grav drive. Jumps are aimed at bare coordinates from the departure end with nothing laid at the destination, which is the bootstrap the entry forbids; the chained-jump structure of the Settled Systems is infrastructure in effect but the game never argues it so.
• SILENT: Stargate: the ships' hyperdrives. Ships jump from a standing start to anywhere with nothing laid along the route; the bootstrap is never raised. The gate network is infrastructure of exactly this kind and is scored in its own dossier.
• SILENT: Super Dimension Fortress Macross (1982): the space fold. The fold is fired from the departure end with nothing laid at the destination, which is exactly the bootstrap the entry forbids; the arrival at Pluto instead of the Moon is consistent with an unaimed jump but the series never argues it so.
• SILENT: The Hitchhiker's Guide to the Galaxy: the Infinite Improbability Drive and bistromathics. The drive is built once at Damogran and works from a standing start, with no infrastructure along the route; Krasnikov's and Coule's bootstrap is never raised.
• SILENT: The Orville: quantum drive (2017 onward). Ships jump to quantum on the spot toward unexplored space; nothing is laid ahead and the bootstrap problem never arises.
• SILENT: Vinge's Zones of Thought: FTL only where physics permits it (1992). The ultradrive goes anywhere in the Beyond on a first flight with no route laid; the bootstrap is never raised.
• SILENT: Weber's Honorverse: hyper bands and Warshawski sails (1993 onward). Hyper travel needs no route laid, only a survey of waves; the bootstrap is never raised. Junction termini are infrastructure but are the L3 secondary.
• ENGAGES: Contact: the Machine and the tunnel system (Sagan 1985, Zemeckis 1997). This is the constraint the work answers on purpose: the tunnels are a pre-existing network built by an earlier civilisation and merely used by the senders of the message. Warp travel is infrastructure, and Contact makes it inherited infrastructure.
• ENGAGES: Interstellar: the wormhole near Saturn (2014). The film says the wormhole is not natural and was placed there by "they"; the route was laid in advance by an agent whose reach covers both ends, which is exactly the escape hatch CON-2 names.
• RULE: 2001: A Space Odyssey (1968): the Star Gate. The gate was laid three million years in advance by the makers and signalled from the Moon; the route exists before any human uses it, which is the entry's demand, and the novel makes the waiting explicit.
• RULE: Andromeda: the slipstream. Slipstream is a network of routes that exist independently of the ship, must be found, and improve with use ("The Widening Gyre" follows routes "large and well-traveled"). That is infrastructure rather than a drive built from a standing start, which is the shape Krasnikov's bootstrap requires; the show does not name the row, but the rule answers it.
• RULE: Babylon 5: hyperspace, jump gates and beacons (1993 to 1998). Gates and beacons are the register's railway laid in advance: ships without jump engines cannot enter at all, everyone needs the beacon to arrive and the frontier is opened by explorer ships that build the next gate ("A Distant Star"). The stated rule answers the bootstrap without knowing it.
• RULE: Cordwainer Smith: planoforming, Space² and Space³. Locksheets, "one hundred thousand charts to the inch", prepared in advance for every contingency ("The Burning of the Brain"), are the work's version of a pre-laid route: a ship without the right sheet is lost. The rule answers Krasnikov's bootstrap in spirit, by making planoforming depend on prior survey.
• RULE: Cowboy Bebop (1998): the astral gates. The gates were built by the corporation at sublight speed before anyone used them, and there is no gate anywhere a gate has not been built; the route-laying step the entry demands is the series' whole premise, and the show says so by making the corporation the owner.
• RULE: EVE Online: the warp drive (CCP Games, 2003). Warp only toward a gravity source, natural or artificial, is the CON-2 answer as a rule: the destination must already be there, and stations and gates broadcast fake gravity wells for ships to warp to.
• RULE: Farscape (1999): wormholes, and starburst as a separate thing. Wormholes in Farscape are natural and found, or opened by knowledge nobody can engineer; the Peacekeepers' failure to build one and Crichton's dependence on implanted knowledge are the show's version of "you need one to make one", though the route-laying step is never stated as such.
• RULE: FTL: Faster Than Light, the jump drive as a game mechanic. The stated rule is that jumps go only between linked beacons that exist before the ship arrives, and a ship cannot jump where there is no beacon. That is a pre-laid route network, the shape Krasnikov's bootstrap requires; the game answers the row by making the network a given.
• RULE: Guardians of the Galaxy Vol. 2 (2017): jump points. Access points are fixed and must be reached, 47 clicks through an asteroid field in the opening chase; nobody makes a jump point where they need one, so the route exists before the trip, which is the entry's demand. Who laid the points is never said.
• RULE: Homeworld: hyperspace cores and the Far Jumpers. The sequel's stated rule is that the gate network was built by the Progenitors long ago and can only be reactivated with the three cores; the cores themselves cannot be built, only found. That is Krasnikov's and Coule's bootstrap as a plot: you need one to make one, and nobody living can make one.
• RULE: Hyperion: the farcasters (Simmons 1989). Portals only between portals, installed by the Core in advance on every Web world; off-Web worlds are reached by ship. CON-2's escape hatch, infrastructure laid ahead of the traveller, is the setting's rule, and the Fall is what happens when the infrastructure's owner withdraws it.
• RULE: Mass Effect: element zero and the FTL drive (BioWare, 2007). The drive needs nothing laid ahead, but the setting's long-range travel does: relays only between relays, built by someone else in advance, is a stated rule of the fiction that happens to be the CON-2 answer.
• RULE: Mass Effect: the mass relays (BioWare 2007 onward). Relays only between relays, and the relays were laid by the Reapers; nobody reaches a system without one and nobody builds the far end. CON-2's escape hatch is the game's premise and, in Sovereign's speech, its trap.
• RULE: No Man's Sky: the hyperdrive, warp cells and range. Portals exist before the player arrives and connect only to other portals; black holes are where they are; the hyperdrive alone works from anywhere. The stated rule for the shortcuts is a pre-laid network, which is the bootstrap's shape, and the drive itself is silent. Scored RULE on the portals, the game's own infrastructure.
• RULE: Outer Wilds (2019): Nomai warp cores. A standard core cannot reach a place without a core already there, and the Ash Twin towers were connected by physically delivering a core to each planet from the forge; the entry's demand that the route be laid at ordinary speed in advance is a stated rule of the game.
• RULE: Star Citizen: quantum drive and jump points. Jump points are natural and found, not made, and the lore's history is a history of discovery from Croshaw onward; the route exists before the trip, which is the entry's demand stated as the setting's premise.
• RULE: Star Trek subspace radio. Amplifiers, relay stations and the MIDAS array are laid at sublight along the route before the signal can use them; the shows make communication an infrastructure problem, which is the shape of the bootstrap
• RULE: Star Trek: transwarp, quantum slipstream and the other beyond-warp drives. The Borg conduits are infrastructure laid in advance by someone else, which is the CON-2 answer stated as a rule of the fiction: coils open existing conduits, the hub is a fixed structure, and destroying it closes the network.
• RULE: Star Wars: hyperspace (1977 onward). The films' charted lanes and runs are the register's railway: safe travel is along routes laid down in advance (Solo), and an uncharted jump is the deadly case (1977). The rule answers the constraint without knowing it.
• RULE: Stargate: the gate network (1994 film, SG-1 1997 onward). The stated rule is that gates only connect to gates and the gates were laid by the Ancients; the traveller never creates the far end. This is CON-2's escape hatch (devices placed along the way in advance) as a rule of the fiction.
• RULE: Starman Jones: the congruencies (Heinlein 1953). The anomalies are natural and charted by survey; a ship flies to one at sublight speed and cannot make one. CON-2's escape hatch, pre-existing infrastructure, is the novel's rule.
• RULE: Stellaris: warp, hyperlane and wormhole (Paradox Development Studio, 2016). Wormhole stations, gateways and the L-Gate terminal must exist before they can be used, and the 2.0 gateways are ancient structures built by someone else: the CON-2 answer as a game rule, for those modes. Warp and jump drives ignore it.
• RULE: The Alderson drive (Niven and Pournelle 1974). Tramlines exist between stars by nature and a ship must fly to the Alderson point at sublight speed before jumping; nothing is created on a first flight. CON-2's escape hatch is the drive's premise.
• RULE: The Expanse: the ring gates and the slow zone (Corey 2013 onward). The stated rule is that gates lead only to gates and the whole network was built by the gate builders; humans lay nothing and reach nothing without a ring. CON-2's escape hatch, infrastructure placed in advance, is the fiction's premise.
• RULE: The Forever War: collapsar jumps (Haldeman 1974). The endpoints are natural collapsars, discovered and catalogued, and the ship must physically fly to one at sublight speed; nothing is created on a first flight. The rule answers CON-2 by making the infrastructure pre-existing rather than pre-laid.
• RULE: Thor (2011): the Bifrost. The Bifrost has a fixed home end, an observatory and a keeper, and cannot be created on demand from the far side: Thor banished on Earth cannot return unless Heimdall opens it. The route exists before the trip, which is the entry's demand, though the film does not say how the far ends were laid.
• RULE: Warhammer 40,000: the Warp (1987 onward). The Astronomican is a beacon projected in advance from Terra, and outside its light ships are limited to short jumps (Owlcat 2023); the stated rule is that long-range travel needs infrastructure that was laid first.
• RULE: Wing Commander (1990) and the 1999 film: jump points. Jump points are natural and fixed, found by probes to "uncharted jump-spheres" and marked with buoys; nobody makes a route, so the route exists before the trip, which is the entry's demand stated as the setting's premise.
• RULE: Xenocide: travel through the Outside. The drive needs the ansible network as its substrate: Jane can only hold the pattern while running on every computer the network links, and Children of the Mind turns shutting the network down into the threat. That is a pre-laid infrastructure rule, and it answers the bootstrap row in the work's own terms.

Sources

• Krasnikov, Phys. Rev. D 57, 4760 (1998), arXiv:gr-qc/9511068; Coule, Class. Quantum Grav. 15, 2523 (1998) ✓