A spaceport is a way to increase the volume of interplanetary or interstellar transport. They can be locate inside space stations but the focus here is on planetary ground stations.
Note that if the booster vehicles are pathetic and weak (like current NASA chemical rockets), the spaceports will have to be located at specific lattitudes.
Often you will find both, with a planetary "LowPort" associated with an orbital space station "HighPort". The HighPort is for passengers/cargo (P&C) for which the planet is just a way-station, not the destination. No sense shipping P&C down then up an expensive gravity well for no reason. One cargo ship drop off P&C at the HighPort, P&C intended for the planet travels to the LowPort in shuttles, P&C in transit wait at the HighPort for their connecting flight to show up.
If the station services starships instead of interplanetary ships, it is often called a "starport".
Like any other living system, the internal operations of a spaceport can be analyzed with Living Systems Theory, to discover sources of interesting plot complications.
Their primary function is to do whatever is necessary to make it easier for spacecraft to bring cargo and/or passengers. They may be located at an economically worthless site which happens to be at a strategic location (cross-roads or junction). Or the site itself could be of economic interest. Please note that increasing the volume of transport does not necessarily mean all transport. A spaceport created by a large corporation might facilitate transport spacecraft belonging to that corporation, but charge large fees and otherwise put roadblocks in the way of ships belonging to rival corporations or to independent ships.
Note that the concept of a "junction" really only works with some kind of handwaving faster-than-light starship. Junctions make no sense in a star system where the various planets orbit at different rates. The arrangement of planets is constantly changing.
As with spacecraft and space stations, in a science fiction story a spaceport can become a character all by themselves. The obvious example is the great hive of scum and villainy which is Mos Eisley spaceport.
A good sourcebook for science fictional spaceports is the worldbook GURPS Traveller: Starports
Spaceports are also likely to have extensive medical facilities with special equipment for treating burn victims (survivors of crashed chemically fueled rockets) or radiation exposure victims (survivors of crashed nuclear fueled rockets), or both. If the spaceport services starships from alien ecosystems, there will be quarantine facilities as well.
If the spaceport is located inside a sovereign nation, the grounds of the port might be legally still territorially part of the nation. But parts of the port could be designated as customs areas and surrounded by a customs border.
In addition, the grounds of the port might be considered "extraterritorial": legally it is not territorially part of the nation. Much like the grounds of a foreign embassy. This is usually seen when the planetary government is part of a larger interstellar Federation or Union. The planetary government might still be self-governing, but the spaceport grounds are legally the territory of the all-powerful Federation. So respect their borders or the planetary government might suddenly find it is no longer self-governing.
If a cargo spacecraft is carrying items that are contraband inside the customs area (not just contraband outside the custom area), the ship will have to use its internal embargo locker. The contraband is placed inside the locker and it is sealed by the spaceport custom authorities (not the planetary custom authorities) for the duration of the ship's stay at the port.
Sometimes, in a effort to encourage economic development, a spaceport can be a free trade zone.
Of course if the planet has an oppressive government and is full of people eager to flee, the spaceport is likely to be surrounded by the futuristic equivalent of the Berlin Wall, complete with barbed-wire, machine gun nests, spotlights, and ferocious guard dogs. The guns will be pointed outward away from the port, instead of pointed inward towards the port.
Spaceports located near an impending war zone could start to resemble Casablanca. Spaceports that are Pirate Haven might resemble the fictitious depictions of the pirate stronghold of Tortuga or Port Royal. The difference is that Tortuga was pro-pirate while Port Royal was officially anti-pirate but unofficially it would look the other way and ask no embarrassing questions in exchange for a cut of the ill-gotten gains.
Also keep in mind that if a planet is invaded, the spaceports are prime targets. If the port can be captured (without being damaged), it will can be used to land large numbers of invading ground troops. It also might be the only way to get the invading troops off the planet. So the invaders will be very careful not to damage the spaceport, otherwise they might be stranded.
The planet knows this as well. If it is worried about invasion the spaceports will also be built up like a minor or major planetary fortresses. Actually, if the spaceport has spacecraft laser launchers or cargo mass drivers, it already is a planetary fortress. A launch laser or mass driver powerful enough to boost huge masses into orbit can smash a combat starship like a sledge-hammer hitting a cockaroach.
If there is a planetary disaster, spaceports will suddenly be thrust into the role of operational center. After all, it will be the source of all off-planet support.
If the planetary spaceport is located on a habitable planet, the port does not have to worry about the Three Generation Rule like space stations do. If the technological civilization falls, people can still breath. Otherwise the planetary spaceport is in the same boat as a space habitat.
Some spaceports are oriented more towards handling cargo, others more for passenger service. In older science fiction Terra's largest starport is always located in New York City, even though it makes more sense to locate a port on the equator for delta V reasons.
When a ship is landed, and still manned, the central control is generally shifted from the control or flight deck to another part of the ship, called a quarterdeck. In a merchant spacecraft, this will probably be somewhere in the cargo hold. The watch officer and their staff will be found in the quarterdeck. It will have repeaters for the critical system monitors, for use by the watch officer.
In "wet navy" ships, the quarterdeck is merely the area just inboard of the crew hatch, where visitors are received aboard.
Spaceport policies are set by the port owner, who could be a variety of people. The port might be a lonely trading post owned by a merchant or merchant corporation. It could be a transport nexus owned by a huge corporation. It could be owned by the government of the planet or nation the spaceport is located in. It could be owned by an interstellar federation that the spaceport planet and planetary government are a part of. There are lots of possibilites.
As previously mentioned, the point of a spaceport is to make it easier for spacecraft to travel to the site. But that does not mean all spacecraft.
If the port is owned by PlanetGobbler Incorporated, the port will be a free trade zone to PlanGobInc company ships and those ships will be given all due assistance. By the same token, any ships belonging to World Exploiters Ltd. or StarTruckCo will find their lives made into a living hell by the spaceport's excessive fees, obstructionism, unfree trade zone status, punitive tariffs, endless safety inspections, and general nastiness. This would also apply to a neutral ship which is carrying a rival corporation's products as cargo.
And may the Great Bird of the Galaxy have mercy on your soul if you are the owner of an independent ship, you might even be denied permission to land! Corporations hate independent free traders.
If the port is owned by the local government, and said government wants to put pressure on Planet Z, magically any ships from or heading to Planet Z will suddenly be plagued by zillions of unofficial obstructions. Being moved to the end of the line, cargo inspections that "accidentally" damage the cargo, crew harassment, that sort of thing.
Spaceports are funded by several revenue streams. Most ports operate at a deficit, rarely making a profit.
Most of the money is a subsidy from the port owner, be it government or corporation.
Spaceports charge berthing fees to spacecraft for the privilege of landing. They also charge rental fees for the landing pad on a daily or monthly basis. Sometimes if a spacecraft owner cannot afford the berthing fee, the spaceport's cargo broker will accept spacecraft's cargo in payment.
Spaceports obtain revenue from any spaceport-owned port services used by visiting spacecraft.
Finally spaceports also obtain revenue by renting spaceport land to "concessions" (private companies offering port services used by visiting spacecraft). The rent can be a flat monthly fee, or a flat fee plus a percentage of the concession's gross income.
If the concession discovers that business is not as good as expected, they will complain to the spaceport that the rent should be lowered. If ship traffic increases, with a corresponding increase in concession income, the greedy spaceport might want to either raise the rent or convert a flat rent into "rent plus percentage.
Naturally any spaceports will become very angry with concessions on "rent plus percentage" contract who cheat by deliberately under-report income. Such concessions might be kicked out on the spot. And spaceports have to worry about concessions who mistreat customers, this will also adversely affect the spaceport's reputation. Concessions can be evicted if it can be shown that they are in violation of their contract.
A spacecraft "augering in" is a disaster ranging from the merely disastrous to the utterly catastrophic.
There are many factors.
Did the ship just bend a landing leg, did it topple over, did it land on its belly but didn't snap its spine, did it hit hard enough to become debris strewn over a wide area, did it hit hard enough to make a smoking crater?
Is the propulsion system or power plant (in rough order of increasing calamity) flammable chemicals, flammable toxic chemicals, flammable toxic chemicals that can melt human flesh, metastable helium, solid core nuclear, liquid core nuclear, gas core nuclear closed-cycle, gas core nuclear open-cycle, nuclear salt water rocket, or pure antimatter?
Did it hit any already grounded spacecraft, perhaps causing a chain reaction? Did it hit the spaceport landing pad, or did it hit a city?
And if the spacecraft is constructed out of titanium or magnesium and it catches on fire, whatever you do don't try to put it out with water!
Some of these hazards can be dealt with. Spaceports will probably be located at a distance from any populated area, with the distance proportional to the energy contained in a given spacecraft (the bigger the boom the farther the distance). Propulsion systems that are too powerful probably will not be allowed to land at all. Instead they will be put into parking orbits and cargo/passengers brought to the spaceport in winged space shuttles and ferries. Landed spacecraft will be separated at distances to minimize chain reactions. Weather patterns will be plotted so that the footprint of any plume of toxic gas or radioactive fallout will only go through barren and uninhabited areas. Spacecraft berths will be surrounded by blast protection berms or bunds, which are blast walls that try to channel the force of the explosion upwards (where there is nothing) instead of allowing it to travel sideways (where it will hit other ships or buildings).
For safety reasons, the landing field might only share its location with the emergency spacecraft services and maybe limited refueling. The other functions would be located at a distance hopefully outside the blast radius.
If the distance between the spaceport and the nearest metropolitan area is large, there will probably be some kind of mass-transit service connecting the two. The Star-town would probably be in between the spaceport and the city (Star-town wants to be far away from the explosion, the city wants the nasty Star-Town red-light district far away from it, the balance point between these two forces is the in between point).
Note that some services are owned by the spaceport authority itself, but similar services can be offered by private companies who rent space on the spaceport grounds. The latter are called "concessions".
Naturally a given spaceport could have several functions. And I'm sure you can think of other functions I've missed. Just think about passenger airports and ocean cargo ports for some ideas.
Obviously an area where spacecraft land and blast off from is the sine qua non of a spaceport. Otherwise it isn't a spaceport at all. It doesn't matter if it is a one-ship landing pad that is a bulldozed square of dirt or a titanic paved area the size of Rhode Island spotted with huge soot chrysanthemum shapes, you gotta have a place to land.
Now it is true that I've ranted about how real rockets are tail-sitters, which land on landing pads. But the two big exceptions are Orbit to Surface ferries which land like an aircraft (e.g., the old NASA Space Shuttle) and cargo spacecraft that do not want to raise or lower their cargo twenty stories. Aircraft-like ferries will need something like an airplane runway to land on. Some belly landing cargo spacecraft will need runways as well (the others have sideways rockets like the Eagle Transporters from Space: 1999).
The landing area must be of ground stabilized enough to remove the danger of shifting ground toppling spacecraft. Not to mention being durable enough to withstand the blowtorch from hell that is the ship's exhaust.
If the spacecraft are strictly orbit-to-orbit craft that never land on a planet the spaceport will only handle surface-to-orbit ferry ships.
One of the major constraints on spaceport design is the danger level of the spacecraft propulsion systems. It isn't so bad if the spacecraft is actually parked in orbit with the cargo being ferried down in winged space shuttles. It becomes more of a concern if the spacecraft are chemically powered tail-landers. And things get very dangerous if the spacecraft are nuclear powered. If the spacecraft is antimatter powered it probably is not going to be allowed anywhere near a planet, much less land on it.
The danger level of the spacecraft using the port will also influence how far away from cities and major populated areas the spaceport is located. Nuclear powered spacecraft will mandate that the potential footprint of the fallout plume goes through only barren and uninhabited areas. An Orion-drive ship can lift-off with little or no fallout if the launch pad is armor plate with a coating of graphite dust. If the spaceport is on a planet with an atmosphere, do not land under Orion-drive power. The nuclear pulse units in an atmosphere will generate horrible nuclear fireballs that the landing ship will fly into, instantly voiding its warranty.
The energy of the ship's exhaust is:
Fp = (F * Ve) / 2
- Fp = thrust power (watts)
- F = thrust (newtons)
- Ve = exhaust velocity (m/s)
From a bare-bones no-frills standpoint, a landing field is pretty much identical to a launch facility. The bare minimum is a stablized patch of ground, as long as it is paved with something durable enough to withstand the launching spacecraft's exhaust. The huge white clouds you see at a NASA rocket launch are not actually the rocket's exhaust. They are created from massive amounts of water poured on the launch pad during launch, to keep the concrete floor from being roasted to ash. Remember that the old Space Shuttle expended power at a rate of 20 gigawatts during the eight minutes of launch thrust.
But the point is if you are launching from a rudimentary spaceport, the spacecraft is responsible for providing the lift-off thrust.
Fancier spaceports can provide some additional launch thrust to the spacecraft. For a fee, of course.
Spaceports could sell strap-on booster rockets suitable for your spacecraft. These may or may not be reusable, but that is the spaceport's problem, not the ship owner. Reusable boosters would be cheaper for the ship owner compared to discardable boosters, but from the spaceport's view the reusable require a bigger up-front cost. This is balanced by the fact that the cost of the reusable can be amortized over many launches. In other words it is yet another example of Commander Vime's "Boots theory of socio-economic unfairness".
There are even more sophisticated (and more expensive) launch-assist installations that a spaceport can use to help launching spacecraft get into orbit and also extract more money from the ship owner.
- Mass Driver: Basically a huge coilgun capable of electromagnetically accelerating payloads or spacecraft.
- * Laser Launcher: large array of lasers capable of energizing a laser thermal booster on the spacecraft
- * MagLifter: type of rocket sled like a magnetic levitation train carrying a spacecraft
- * Bifrost Bridge: a combination of MagLifter and Laser Launcher.
- Lofstrom loop: Like a MagLifter, except the midpoint of the rail is 80 freaking kilometers off the surface
- * Landing Grids: This is unobtainium at best and handwaving at worse. The grid taps into the electrical potential difference between the ground and the ionisphere to access terawatts of power. This powers something like a mass driver
- Space Fountain: This is a clever way to make a tall tower. Tall as in "out to geostationary orbit" tall (about 35,786 km on Terra). This would probably be used to drag payloads to spacecraft in GEO, rather than draging the entire spacecraft into GEO.
- Space Elevator: This is a clever way to make a tal elevator. Further than GEO. Probably will only be used to drag payloads, much like the Space Fountain.
* these systems can be used to make the spaceport into instant impromptu planetary fortress
On heavily populated planets each launch may be overseen by the Launch Guard range safety officer. Who have their finger hovering over button that will vaporize any spacecraft suffering a catastrophic engine failure which is in danger of falling on a city.
The Launch Guard is also in charge of switching laser launchers and such from "launching spacecraft" mode into "impromptu planetary fortress" mode.
Ship docks are for short or long term storage of spacecraft.
If spacecraft have to land on specially constructed landing pads, a spaceport might only have a limited number of them. If the ship is going to be on the planet for a while, the spaceport will want the ship moved off the pad and dragged to a dock for more permanent storage. The docks may each be surrounded by a blast protection berm, so one spacecraft blowing up doesn't start a chain reaction with their neighbors.
If spacecraft can land on a reasonably flat piece of ground or concrete (instead of a specially constructed pad), the spaceport will have virtually unlimited amounts of landing pads. In that case, the spaceport doesn't mind if a ship stays on its landing site for months and months, as long as the captain pays the pad rent.
At a spaceport, moving a tail-landed ship to another site is tricky. The spacecraft's lateral jacks are extended so the tail of the ship is lifted off the landing apron. A crawler is then backed under the spacecraft, and the ship is lowered onto it. The "bottom handler" runs the crawler. The "top handler" rides in the control room of the spacecraft. Under each fin of the spacecraft is a hydraulic mercury capsule. The top handler keeps an unblinking eye on a bubble level gauge, and uses a joystick to control the mercury capsules. If the spacecraft starts to tip, the appropriate mercury capsules are pressurized to counteract the tip.
Belly landed ships are easy to move, just use a tractor to tow the ship on its wheeled landing gear.
The spacecraft area might be arranged into Parkbays. These have a launch/landing pad in the center, surrounded by a series of spacecraft berths. The berths are separated from each other by blast protection berms. When a spacecraft lands on the pad, it is then moved into one of the berths. If the spacecraft explodes, the berms will channel the blast upwards where it does no damage, instead of allowing it to damage the spacecraft in the neighboring berths or the rest of the spaceport.
Actually this is very similar to the way they construct firework factories: thick strong walls and thin flimsy roof. Roofs are relatively inexpensive to replace, so the strong walls will funnel the blast so it eliminates it. If instead you make a strong roof and flimsy walls, you'll end up with roof and the factory walls blown into dust.
A stunning scratch-built plastic model of an atomic rocket by master model-maker Michael 'Woozle' McGuire. This model was one of the winners in the "Space Racer" contest at Starship Modeler. It was inspired by Lester del Rey's short story "Habit".
However, there will spring up a "star-town", i.e., a thick border around the starport composed of ethnic restaurants, bars, tourist traps, casinos and bordellos all meant to rapidly separate newly-arrived starship crew members from their flight pay. Plus a few pawn shops where crew members who have blown all their flight pay can get extra cash by hocking their equipment, personal items, and/or alien curios they acquired during their travels. Not to mention smugglers and black marketeers, who are buying and selling contraband goods and illegal transport services. Smuggling also applies to fugitives attempting to escape off-world. Look, over in the corner, is that Obi-Wan Kenobi negotiating with Han Solo? Star-town will also have "flop-houses" which are cheaper than the capsule hotels but much more disgusting. There are charity soup-kitchens as well.
The darker sections of star-town are dangerous, much like any benighted urban area. Tourists enter at their own peril. There are predators who will rob you at gun-point, pick-pockets, con artists and related criminals.
In his article Happy Landings! Starport Design in Traveller (White Dwarf #43) Thomas M. Price makes a strong case for locating Star-town inside the extrality fence, instead of outside as in the Traveller game. He notes that sale of fuel, repair fees, warehousing fees, and a percentage of cargo sales is not going to be bring in enough money to keep the starport solvent. Putting Star-town inside the extrality fence will not only give the starport license to get a cut of the money, but will also make Star-town much more lucrative.
Inside the fence the local planet's laws do not apply, so Star-town can offer all sorts of (money-making) vices that are immoral and illegal (and in high demand) on the planet. And all tax-free as well, just like an airport Duty-free shop. Since the starport managers are not fools, there will be an inner fence separating Star-town from the starport proper. The managers want their cut of Star-town money, but they won't allow unruly inhabitants or the criminal element to interfere with the operation of the port.
I'm sure the planetary police department will have a checkpoint at Star-town's exit, to make sure people don't try to bring any illegal souvenirs home (e.g., a suitcase full of contraband drugs).
Michael Andre-Driussi points out that the location of Star-town will depend upon how often spacecraft crash and how radioactive their exhaust is. Maybe Star-town will be at some distance from the actual landing site. Or it might be milder: with Star-town encircling the landing site, but with the low-rent district downwind in the footprint of the fallout zone. He also points out that the same factors will determine how far the spaceport itself is from any cities or other populated areas. Lots of crashes or landing pads that glow in the dark mean a spaceport in the middle of the desert or other barren wasteland. In that case, Star-town will be located approximately halfway between the starport and the nearest city, with regular mass-transit service to the port.
Radioactive fallout is typically in a long skinny plume pointing in the wind direction. So, for instance, if the wind generally blows to the south-east, the prime Star-Town locations would be north-west of the launch site, the upscale locations would be north and west, the average locations would be north-east and south-west, the ghetto would be at east and south, and the real bad part of town would be south-east.
So you're a starship crew on leave and prowling the port's Star-town, and you've already blown your flight pay on the bars, brothels, and gambling halls. Need some quick cash? Head for the nearest Pawn Shop and see if you can hock some of your junk to fund more liquor and iniquity.
Pawning your official issued equipment can get you into trouble (especially your sidearm) but a clever crewperson will pick up unusual gems or other exotic trinkets on one planet hoping they can be hocked as expensive off-world curios on another planet.
This can include small alien animals if they can pass the ship doctor's decontamination and quarantine. Good luck getting such live goods onto another planet, most governments are incredibly paranoid about allowing the import of a possibly invasive species. This happens far too often by accident.
Pawnbrokers know that often thieves will approach them with stolen goods, hoping the broker will unwittingly (or wittingly) act as a fence. Pawnbrokers also know that this is common knowledge among the local police, so always have plausible deniability.
While spacecraft can violate the old "what goes up must come down" principle, they do not always. If the spacecraft launches from a planet's surface by using multi-staging, the lower stages typically plumet randomly into the drop zone (though SpaceX is changing all that with their reusable stages that fly back home). And if the spacecraft explodes during launch, all bets are off.
This is why ground based spaceports try to have their launch corridor passes over uninhabited areas. For energy saving reasons the corridor usually points in the direction of the planet's spin (eastward on Terra), also as parallel as possible to the equator, and at a latitude as close as possible to the equator. That is for equatorial orbits used for most crewed missions. There are different restrictions on polar orbits, but those are generally only used by spy satellites or other items that need to pass over all parts of the planet.
The operative word is "try." Russia got short-changed in the launch site department, and had to make do with a bad set of options.
The ESA and CNES have the marvelous Centre Spatial Guyanais located barely 5° from the equator. NASA has Kennedy Space Center Launch Complex 39 which is 28.5° from the equator. Not perfect but not too bad.
Russia looks into its trick-or-treat bag like Charlie Brown on Halloween and says "I got a rock…" The best launch site they could find within their national boarders was Baikonur Cosmodrome which is an abysmal 45.6° from the equator.
It gets worse. If they launch from Baikonur at 45.6° the launch corridor goes straight across Mainland China. Who would take a very dim view of spent Russian rocket stages and flaming rocket aborts raining death from the skies onto their territory. A bit of a casus belli, that is (of course China does the exact same thing to their own citizens, but since when is political hypocrisy anything new?). To avoid all that unpleasantness the Russians launch at an even more miserable angle of 51.6°. Which is why the International Space Station is at that inclination, otherwise Russian rockets could not reach it. The ISS inclination is a good thing since due to NASA mismanagement the Russians currently have the only rocket capable of sending a crew to the space station. But I digress.
The unfortunate part is the first desiderata of a launch corridor: that it passes over uninhabited areas. Guyanais and Kennedy are well positioned with their corridors right across the uninhabited Atlantic Ocean. Baikonur Cosmodrome is not so lucky. Its corridor does not go over heavily populated areas but it certainly isn't uninhabited. The Russian Federal Space Agency designates a narrow strip of land as the supposed launch corridor. Residents within this zone are given 24 hours' notice of a launch. They can only claim compensation for damages for flaming rocket debris that hit something outside the zone. Which happens regularly since the rocket parts do a poor job of staying inside the zone. And that is when the launch goes perfectly, if the rocket explodes in midair debris goes everywhere.
China seems to be almost as bad for reasons opaque to me. Their Wenchang Spacecraft Launch Site is at a reasonable location, only 19° from the equator and with the launch corridor over the uninhabited Pacific Ocean. But the other three launch sites are at random locations within the mainland, and all the little villages located in the launch corridors just have to take their chances.
Over and above the danger of a rocket stage falling on your house or starting a grass fire engulfing your crops the Russian stages have even more terror. Many of the rockets use unsymmetrical dimethylhydrazine ("heptyl") for fuel. Troy Campbell describes this stuff as "explosive cancer". Blows up if you give it a stern look and classified as carcinogens.
The toxic heptyl has contaminated the soil of the area. It regularly kills cattle and horses, and is linked to a rise in birth defects and crop failures.
Finally I am getting to the point. To the desperately poor villagers living in the launch corridor, these falling rocket bits are composed of valuable metal that they can sell to scrap metal dealers for actual money. Aluminum, titanium, and copper fetch top dollar… er, ah, ruble. So the villagers have become amateur shipbreakers. Despite the danger from fire, explosions, and cancer. The rocket debris is often still burning when the shipbreakers arrive, giving off toxic smoke.
Science fiction authors always take heart in the aphorism: "Everything Old Is New Again". So just like Mos Eisley spaceport is a futuristic wretched hive of scum and villainy modeled on the myriad historical port cities that were wretched hives of scum and villainy, it is a safe bet that future spaceport administrators will tend not to give a rat's heinie about the poverty-stricken people inhabiting the low-rent district of the launch corridor.
The spaceport will also offer the services of a "weightmaster". Each fin of the spacecraft rests on a scale (while the exhaust bell points at a splash baffle or thrust diverter). The weightmaster reads the scales, totals the weight, and advises the captain. If the mass is too much over or below the mass the calculations are based on, mass will have to be removed or added.
Shortly after blast-off from a spaceport, the spacecraft can call the tower to request range, bearing and separation rate, and flight plan deviations. This is not only to check if the spacecraft is on track, but also to used to double check the performance of the spacecraft's own instruments against the land based ones. This is usually the co-pilot's job.
Landing sites in the spaceport will probably be labeled with large numbers and letters, much like real-world airport landing strips are. Airports use a special font with no name called "runway designators". The font has no confusing curves so it has good visibility to help the pilot land his vessel, and so that groundskeepers with poor mathematical skills can lay out the designators and keep them in good repair.
William Hostman made this into a truetype font, you can download it here. He used 0-9 and the C, L & R letters from the picture, the rest he had to derive. He used a vertical 60% small caps ratio. If you have feedback about the letters he derived, you can contact him by email hostman.william at gmail.com