http://zerraspace.deviantart.com/art/SMAC-Tribute-The-UNS-Unity-Design-585808034SMAC Tribute - The UNS Unity (Design)
by Zerraspace“Earth, 2060: a small group of colonists leaves the ravages of Earth for a distant planet orbiting Alpha Centauri’s primary star. Their ship, the United Nations Starship Unity, carries them on their journey to a new world, and a new hope for humankind. Along the way a reactor malfunction damages the Unity, precipitating a crisis among the ship’s seven most powerful leaders. As they enter the Alpha Centauri system, the crew splits into seven distinct factions, divided not by nationality, but by ideology, and their vision for the new world. After the ship breaks apart, the seven leaders guide their chosen crew down to the surface of Planet, seeking their destiny beneath an alien sky.”
-Sid Meier’s Alpha Centauri, opening cinematic
Sid Meier’s Alpha Centauri is without a question my favourite science fiction game, and I’ve had it in my mind to make a tribute to it for some time, setting my eyes upon the all important ship that started it – the final frontier’s Noah’s Ark, the ship that sailed for 40 years, carrying within it the remnants of human civilization in cryosleep to begin anew – the UNS Unity.
This proved a lot more challenging than I initially suspected. The game itself is masterfully designed, with incredible attention to the setting and detail, but it seems this didn’t extend to the Unity itself. The game manual suggests that an expert was called upon to help in designing it, but I can’t shake the feeling that a lot was lost in communication, as Firaxis can’t seem to make up its mind on just what the ship looks like – during the introductory cinematic, it is shown with a frontal bay during the panoramic turntable that disappears in the very next scene and remains off after, only to reappear alongside a centrifuge that was never before present in the resold game menu. The canonical “Journey to Centauri”, written to promote the game’s release, describes the Unity as relying on a pulsed fusion drive and having a single fusion core (which can be found in the ship wreckage during the course of the game itself), yet all renditions of the ship have three thrusters and hardly match the description. The GURPS campaign further confuses things, claiming the ship utilized an antimatter plasma drive in conjunction with a bussard ramscoop, capable of 0.03 and 0.01 g operation, and had a low mass ratio; while internally consistent, this disagrees with the above, where the Unity is capable of high enough thrust to knock down all its crewmembers and shake itself apart, and to quote Zakharov: “The amount of fuel it took to get us here, is astronomical. Literally!”
These could not all be redeemed, so I decided to take some liberties, drawing upon such sources where possible, generally taking the original over the GURPS where they disagreed, and redesigning where things didn’t really fit (for instance, the four fins were poorly positioned to be radiators as they would intercept all the radiation from the drives and had to go). Personally, I would have fitted the ship with a magnetic sail to slow itself on approach to the Alpha Centauri system, or used the ship’s full thrust for the deceleration phase to slow it down more quickly, either of which would have cut down the mass ratio, but I found a means that’s viable and agreed with the trajectory established in “Journey”. The final ship is as realistic as I could make it: a fusion drive of such scale is probably still beyond us but the technology behind it has all been practiced, this ship could be built today or within the near future. I would have liked to make it run on proton-proton fusion, so that it truly “harnessed the power of the sun”, but decided on deuterium-helium-3 fusion as being more reasonably achievable. This still stretches belief somewhat, given the volumes of helium-3 required, but is essentially aneutronic, and gives far better mass ratio than deuterium-deuterium or proton-boron fusion would.
Now, for all the technical information:
•Dimensions: 100 meter diameter at widest point, 150 meter centrifuge, 800 meter length
•Delta-V: 90,000 km/s (30% c)
•Thrust Power: 1.5 PW
•Propulsion: Z-pinch d-He-3 fusion
•Dry Mass: 62700 tons (1st stage: 35700 tons, 2nd stage: 12000 tons, payload: 15000 tons)
•Wet Mass: 1 million tons
•Mass Ratio: 37
•Mass Flow: 4.25 kg/s
•Specific Impulse: 2,720,000 s
•Exhaust Velocity: 8.9% c
•Thrust: 112 Mega-Newtons
•Initial Thrust/Weight: 0.01145 g
Possibly the greatest human undertaking for centuries to come, the Unity was impressive not just for what it was, but the circumstances of its creation - an interstellar voyager, constructed by a deteriorating degenerate world that had barely reached out into the void, much less grasped its rigors.
The ship is meant to run autonomously, keeping its 50000 passengers in cryosleep for the duration of its 40 year voyage. Onboard supplies are simply not sufficient to sustain such numbers for any reasonable length of time, and as such, even in the event of crew awakening – whether due to an emergency or upon finally reaching the destination – only the most vital administrators and engineers are to be brought out. Their first task upon touching down at Chiron would be to set up farms and basic infrastructure, that they all may eventually be provided for. While active, the cryocells sit next to the cryogenic fuel containers, relying on their thermal mass to maintain cool in case of an emergency; these are later moved into a more thermally equitable 'resuscitation chamber' to prepare them for awakening.
Payload consists of the 50000 passengers in their cryocells, which were repurposed as landing chairs and even sleeping cells, 5000 tons of supplies (largely machinery and hydroponics, the latter within the centrifuge compartments which are kept folded against the ship side for most of the journey to fit behind the impact shield), and a menagerie of probes and landers. The mainstay of this fleet were 8 reusable colony pods, meant to ferry supplies down from the Unity in orbit, each capable of single-stage ascent despite Chiron’s high gravity and dense atmosphere (1.3 g and 1.74 atm relative to Earth, respectively). Said pods relied on aerobraking to land and refuel themselves on the surface before takeoff, leaving long periods where they were unable to operate, hence a set of non-reusable drop pods were brought along for emergency deliveries. Many of these managed to survive the Unity’s crash and are now littered across the surface.
The ship skin is made of titanium-carbide, one centimeter of plating to protect from atmospheric heating during aerobraking maneuvers, ten centimeters of foam to provide thermal insulation and minor protection from dust impacts, with even greater thickness present at the front of the ship. The internal components and spaceframe are composed largely of carbon-fiber reinforced polymers, save near the magnetic nozzle, where they are replaced with rhenium-tungsten alloys for heat tolerance and radiation shielding.
Most of the ship’s dry mass goes to propellant storage, as the deuterium and helium-3 are stored cryogenically in gaseous form and at high pressure to make up for their normally low density (even in liquid state); at 26 K and 100 MPa, mean density is 1.6 g/cm3, better than water. This requires heavy duty containment tanks, and though the propellant cells are made of ultra-high strength carbon fiber, weighing only 38 grams for every kilogram stored, the ship’s high mass ratio translates this into quite cumbersome tankage, and the dry mass of the first stage goes almost entirely to this end. The bulk of the remainder goes to the capacitors that charge the ship drive – some 2000 tons heavy – and the 10 meter radius rhenium/tungsten alloy radiation shield, which operates just a hair under melting point at full power sopping up the 20% X-ray output.