Heavy spacelift
Even in the age of fusion, the old maxim that once you are halfway to orbit, you are halfway to anywhere holds true. A fusion torch engine that will propel a ship from Earth to Mercury in less than a month is next-to-useless on Earth’s surface: the fusion reaction is smothered by interactions with the atmosphere. Counterintuitively, it is actually easier to return from orbit with a fusion torch engine than it is to get there in the first place: a fusion tug can burn retrograde to cancel its orbital velocity, release a raft of cargo containers to make a soft landing on Earth, then return to a stable orbit to repeat the process. Ascending from Earth’s gravity well, however, remains dependent on the same chemical reactions that were first pioneered over two hundred years ago.
Passengers generally use spaceplanes to reach orbit, which offer a gentler ascent compared to rockets. The C428 family, produced by Skybus SE, is the most common passenger spaceplane in service. 90 metres in length, the C428 can carry up to 15 tons of cargo, or between 100 and 150 passengers. Much of the cigar-shaped fuselage is taken up by hydrogen and liquid oxygen tanks, which feed two Roberts-Royston SG-700 dual-mode combined-cycle rocket engines. These engines also propel high-altitude hypersonic airliners: in atmosphere, these engines compress air to a very high pressure, burning it with liquid hydrogen to provide high thrust. When it reaches altitudes where the air is too thin to burn, the engine closes and acts as a chemical rocket engine burning a liquid oxygen-liquid hydrogen mix. Most modern aircraft also use electrohydrodynamic lifter engines, which make use of electrodes to ionise the surrounding air to produce lift and thrust, to improve fuel efficiency and speed.
The largest passenger spaceplane currently in service is the Stieglitz Aerospace Skyraker family. At 94 metres in length, the Skyraker is only slightly longer than the C428, but has a wingspan between 90 and 110 metres depending on model, compared to the C428’s 27 metres. The Skyraker is a tri delta “wet wing” design, with the main body reserved for payload. It can carry up to 91 tons of cargo, or up to 900 passengers. It is propelled by ten Roberts-Royston SG-900 combined-cycle engines.
While convenient for passengers, spaceplanes are generally inefficient for bulk cargo transport, costing between 250 and 350 dey per kilogram. Traditional rockets are the cargo transport of choice. Tundra Rockets is Earth’s leading space launch provider. Founded in 2091 by the Canadian entrepreneur Tanya Johnstone, it operates three models of launch vehicle, the Eagle medium lift rocket, the Nimbus heavy lift rocket, and the Silver Arrow super-heavy lift rocket. All three rocket models make use of methalox (methane-liquid oxygen) engines, and are fully reusable, with their boosters and upper stages designed to return to the launch sight. The two-stage Silver Arrow is the most common super-heavy lift rocket in use, and can launch up to 150 tons into orbit for a cost of 150 dey per kilogram.
The largest rocket in service is the Ortmann Industries Star Kraken, a two-stage, ultra-heavy launch vehicle with a payload capacity of 550 tons. The Star Kraken is so large that it can only be safely launched from the sea, which also affects its launch costs: the rocket has a launch cost of approximately 670 dey per kilogram, making it less efficient that the Silver Arrow and restricting its use to irregular, oversized payloads that cannot easily be modularised for separate launches.
Laser launch is a concept that shows promise for dramatically increasing payloads and reducing launch costs. Laser launch requires a specialised vehicle that is little more than a payload atop a block of propellant, which receives power from an array of ground-based, fusion-powered lasers. Heavy propulsion systems and tanks of oxidiser are effectively transferred from the spacecraft to the ground, massively increasing the amount of cargo or passengers that can be launched into orbit at any one time. Laser launch has the potential to reduce launch costs by 98% compared to the Silver Arrow series. However, while the theory behind laser launch has been well-understood for some time, implementing it will require massive investment in entirely new spaceport infrastructure, as well as new fleets of laser launch-capable rockets. The Swallow Corporation, which has received the World Union contract for the colonisation of Saturn, plans to establish a proof-of-concept laser launch facility on Titan in 2127.
Spaceports are typically located near steppes, deserts, or coasts to minimise the risk to civilians in the event of an accident. Coastal spaceports also have a reliable source of rocket fuel by reacting seawater with atmospheric carbon dioxide in Sabatier reactors. The number of viable sites for spaceports has expanded significantly since the development of the fusion torch engine: previously, range safety and limited manoeuvring options once in space meant that only a handful of sites could give access to useful orbits. Thanks to the power and efficiency of fusion torch engines, this is no longer an issue: ground-based spaceports are served by a “high port”, a space station in an easily-accessible orbit, from which passengers and cargo transfer to fusion-powered spacecraft, which have none of the limitations of chemical rockets and spaceplanes. A single high port may serve a number of spaceports that are relatively close to each other on the surface: the polar-orbiting Boreas Station, for instance, serves Machrihanish Spaceport in Scotland, Cornwall Spaceport, and Brest Bretagne Spaceport in Brittany.