Arachne was a spiderweb spinning in space. Her strands were fullerene wire, cylindrical molecules of pure carbon a trillion trillion atoms long. The spin of the highly conductive web spawned a magnetic field megameters wide, which sucked in the hydrogen ions produced when Arachne's vast lasers illuminated the cosmic gas before her in her path. Concentrated by trillions in the silvery engine core at the center of the web, the dense, hot hydrogen was fired to still greater temperature by reaction with minute specks of antimatter, producing a fulminous spear of high-velocity exhaust plasma which drove the vessel on her long, lonely flight through interstellar depths.. -- "Aggravated Vehicular Genocide"
Magnetic sails: A magnetic “sail” is actually a coil
or web of superconductor, accelerated by a charged-particle beam fired from
the system of origin. The particles are placed in a coherent Bose-Einstein
state analogous to the coherent photons in a laser beam, and are thus able
to travel farther without dissipating, and accelerate the sailship rapidly
to high velocities. To withstand the high acceleration, the crewmembers
are immersed in a dense oxygenated fluid. At an acceleration of 20-25g,
reaching a cruising velocity of 0.9c requires approximately two weeks; therefore
the crew is generally in hibernation during this
stage. A network of “space lanes” can be created by building beam projectors
in multiple systems, allowing regular travel between worlds.
Ramjets: The superconductor web can also function as a Bussard ramjet, collecting interstellar hydrogen for fuel to accelerate a ship beyond what particle-beam acceleration can achieve, or to decelerate it toward a system with no extant particle-beam generators. This is a problematical technology, once almost abandoned as impractical. The energy demands were believed to be vast, and to become vaster as velocity increased. The ramjet field collects interstellar hydrogen from a vast conical area ahead of the ship, drawing it inward to be fused at the center. The faster the ship travels, the faster the hydrogen atoms must be drawn in to the axis, requiring more and more energy. Also, ionizing the hydrogen, charging it so the magnetic field can draw it in, requires vastly powerful lasers. In addition, the ramfield creates a drag against the interstellar medium, resisting acceleration.
Late 21st-century Human engineers developed solutions to these problems, however. One solution was to make the ships extremely light. A ramship is essentially a vast web of superconducting fullerene cable, the strongest fiber physically possible. The web is rotated to give it rigidity through tension rather than compression, requiring far less mass (in the same way that it takes far less material to suspend a bridge from cables than to support it with massive pylons). The rotation creates a dynamo effect in the superconducting web, helping generate power for the ramfield and the lasers. The energy demands of the lasers actually decrease with increasing velocity, since their beams are blueshifted to higher energy levels. The beams must in fact be shifted downward in frequency and power in order to remain at the proper ionization frequency in the hydrogen’s frame of reference. The rotating field is also shaped to redirect the drag of the interstellar medium into thrust, somewhat analogously to a propeller.
The collected hydrogen is heated to extreme temperature by annihilation with small amounts of antimatter, and thus attains enormous exhaust velocity, beyond what a fusion reaction could produce. However, the maximum velocity of any rocket is equal to the velocity of its exhaust; at this point, the velocities cancel and the exhaust is merely left stationary in space, imparting no further acceleration. To exceed even this velocity, the reaction mix is shifted to pure proton-antiproton annihilation, producing meson exhaust expelled at over 90 percent of lightspeed.
The journey is not without peril for the crew, due to the extreme velocity of any incoming particles and the extreme blueshift of approaching radiation. When not being used to collect fuel, the ramfield deflects hydrogen around the ship. The ionizing lasers, generally dispersed into wide conic beams, can be focussed to vaporize larger approaching obstacles. There are generally several widely separated crew compartments, so that any disastrous impact which occurs will not kill the entire crew.
Typical ramship velocity is in the vicinity of 90 percent of lightspeed, though higher velocities can be attained for longer journeys. The Arachne expedition launched toward Gamma Leporis V in 2149 reportedly attained a record value of 95.1 percent. However, its haste led to disaster, and such high velocities are generally frowned upon by interstellar civilization.
Radiation shielding: One of the greatest hazards of spaceflight is exposure to ionizing radiation. This danger is even greater in interstellar space, once a vessel leaves the magnetic field of a star, which provides protection from the bulk of cosmic radiation. The problem is that shielding adds mass to the ship, impeding its engine efficiency; and interstellar craft in particular must be as light as possible.
The solution comes from programmable matter, also known as smart matter or wellstone. Smart matter is an intricate semiconductor matrix of “quantum dots,” potential wells which confine single electrons, forcing them to behave like the electrons in atomic orbitals. Since electron orbitals define an atom’s chemical, electrical and other behavior, this quantum matrix can be configured to emulate the behavior of any element, even ones beyond the existing periodic table, while retaining the original mass of the semiconductor. Smart matter has many uses: it can produce versatile energy-collecting surfaces and distribution systems; it serves as a basis for quantum computers and advanced sensor systems; it can produce materials of variable strength and resiliency or variable appearance and texture, adjustable on demand. But one of its first uses was the creation of lightweight radiation shielding simulating the energy-absorptive properties of much denser elements. This shielding has the added advantage of being able to convert this radiation into usable energy for the ship, further increasing its efficiency.
Hibernation: In long journeys, it is necessary to employ hibernation techniques to conserve resources. The old concept of cryogenic suspension, “freezing” live persons and “thawing” them at the destination, is impractical. Biological functions, and particularly sapient brain activity, cannot simply be shut down and restarted.
The hibernation process, sometimes called cryosleep, does involve lowering the body temperature to slow metabolic processes, but not to the point of freezing. Further metabolic suspension is achieved through chemical means, and the body is immersed in a preserving nutrient gel. Tissue damage is minimized through nanomaintenance. Aging is slowed, but not stopped. The technique would be less effective on pre-Molecular Era humans, in whom aging progressed more rapidly.
The brain remains active at a low level, resulting in a dreamlike
state. The monitoring cybersystem can interact with the mind in this
state through stimulation of the sensory inputs, creating a virtual-reality
experience. The cyber can mediate between brains, allowing interaction.
Upon awakening, crewmembers retain little or no memory of their activity in
this state, sparing them the embarrassment of remembering what they did in
their shared dreams when judgment and inhibition were not fully engaged.
Solsys to Gamma Leporis: Arachne expedition (lost)
Dist: 29.3 ly
Launch: Aug. 2149
| Objective | Shipboard | |
| Stage 1: Particle-beam acceleration (20g) to c. 0.9c: | 13 dy | 11 dy |
| Stage 2: Ramjet acceleration (0.75g) to 0.92c: | 9 dy | 4 dy |
| Projected: | ||
| Stage 3: Low-efficiency photon accel. to 0.95c -- avg. 0.94c: | c. 11330 dy | c. 3865 dy |
| Stage 4: Ramjet deceleration (0.75g) to 0.5c (0.128 ly): | 212 dy | 111 dy |
| Stage 5: Particle-beam deceleration (20g) to system insertion: | 9 dy | 8 dy |
| Total: | 31.7 years | 11 years |
Actual:
| Stage 3: Photon accel. to 0.95c -- avg 0.935c; interrupted 24.1 ly: | c. 9415 dy | c. 3340 dy |
| Gravitic deceleration by Chirrn capture field (c. 14,000g): | c. 35 minutes | c. 20 minutes |
| Total: | 25.8 years | 9.2 years |
Solsys to Gamma Leporis: Anansi expedition
Dist: 29.3 ly
Launch: June 2211
| Objective | Shipboard | |
| Stage 1: Particle-beam acceleration (20g) to c. 0.9c: | 13 dy | 11 dy |
| Stage 2: Ramjet acceleration (0.8g) to 0.92c: | 9 dy | 4 dy |
| Stage 3: Improved acceleration to max. 0.95c -- avg. 0.945c: | 11315 dy | 3701 dy |
| Stage 4: Ramjet deceleration (0.8g) to 0.75c (0.024 ly): | 89 dy | 40 dy |
| Stage 5: Particle-beam deceleration (20g) to system insertion: | 9 dy | 8 dy |
| Total: | 31.3 years | 10.3 years |