Traffic in Space (a traffic controller for low earth orbit)
In a future where space travel is common, how would access to space be regulated?
From what I know, currently the International Telecommunication Union (ITU) assigns slots for geostationary satellites (since the range of geostationary is essentially one-dimensional and otherwise interference would commonly occur). Also, there are strict requirements for spacecraft approaching the International Space Station (ISS). Otherwise, even though some spacecraft coordinate their orbits otherwise there is no control and operators are free to choose whatever orbits are convenient.
This works for now since launches are so (relatively) infrequent that there's little chance of two operators choosing the same orbit and not finding out until they both launch. Also, launches are not a huge deal for airplanes since the Federal Aviation Administration (FAA) will declare a temporary flight restriction (TFR) for the area around the launch.
If spaceflight is common to the point where launches occur once or more per day, then both of these situations would have to change. Spacecraft would have to have some way to coordinate with each other and with aircraft: essentially a Space Traffic Control. How would a space traffic control (STC) compare to modern air traffic control (ATC)?
Here are the three scenarios I am considering:
- Reusable rockets: While everyone was busy trying to figure out how to make spaceplanes work, SpaceX surprised everyone by making the traditional two-stage, liquid-fuel, vertical-stack rocket reusable. Everyone adopts their approach: take off like a modern rocket, but each stage flies right back to the launch pad, ready to refuel. The only consumables are fuel and capsule heatshields. Launch costs drop from thousands to hundreds of dollars per pound. Spacecraft spend little time in the atmosphere on both launch and reentry, so there is little interference with aircraft.
- Spaceplanes: Virgin Galactic eventually made it to orbit with SpaceShipFive, their latest air-launched, rocket-propelled spaceplane. Payloads are small, but launch costs are still quite low. Spacecraft now spend much more time in the atmosphere, but act like modern planes while attached to their motherships, and like gliders during reentry. They take off and land from ordinary runways, whether at ordinary airports or specialty spaceports.
- Airbreathing Single-Stage-to-Orbit (SSTO): The holy grail of space travel. With nanotech-age advancements in materials science, we finally made it"”-albeit still with razor-thin margins. The extremely complex engines required push the limits of what's physically possible and, while they don't need quite as much maintenance as the Shuttle did, that's not saying much. It's barely cheaper than traditional rockets. They spend a good deal of time in the atmosphere at supersonic speeds, making them a hazard to buildings as well as aircraft. However, they are useful for turning 18-hour flights into one-hour flights.
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Note: I'm assuming all relevant space travel is close to earth (that is, there's no need to coordinate e.g. travel to Mars, as soon as it leaves the near-earth range).
One point about space is that it is international. It is simply not possible to keep a spacecraft above a single country. Therefore any space traffic control must be, by its nature, done by a single organisation. This organization can be either an international organisation (like the ITU you mentioned) or a national organization that historically grew into being the global coordinator due to having control over essential infrastructure, like the Internet Corporation for Assigned Names and Numbers (ICANN) which runs the root name servers of the internet.
The reason that space cannot be nationalized is that it cannot be regionalized; every orbit intersects countless other orbits. And there comes the second difference to air traffic control: In air traffic control, there's a tower responsible for a certain area, and when a plane leaves that area, it is handed over to the next tower. I don't think this would be a workable model in space. Whatn would probably work is a sectioning based on height: Essentially you'd have a "tower" for each height range, and when you get to the next height range (which normally only happens during launch and descent, because orbits are usually chosen to be circular), you're handed to the next control center.
Note that all this is for stuff already in space; the method how you get into space doesn't matter for that. For the launch phase before reaching space, I guess the local flight control would still be responsible, since the launch vehicles share the same airspace with planes and thus some coordination would still be needed. This also fits well with height-based space control since the boundary to space is also defined on height.
For reusable rockets, I guess the way to handle it would still be to disallow flights around the space port, and in addition a spaceport tower would handle the coordination between the different launches from the same spaceport (ensuring that leaving rockets don't collide with returning stages, and assigning the time slots when the rockets may start, as well as handling coordination with international space control for entering space).
Space planes, being more maneuverable than rockets, probably would be handled like normal aircrafts which just can reach greater heights, and would be passed on to international space control when reaching space.
I have no idea what flight properties the SSTOs would have (apart from being very fast). However you say that they are expensive (so there won't be too many of them), dangerous, and very fast, so I guess they would we handled mostly like rockets, except that the SSTD space ports would be required to be far from any major city (at that technological level, fast transportation to the space port is probably also a solved problem, so this should not give too much of a disadvantage to those space ports). As technology improves and SSTDs get more safe, the conditions will likely get gradually relaxed.
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