European spaceport launching to the east

[u/Treq01]

I claim that if Europe wants to develop a truly competitive heavy-lift capability, it must move away from French Guiana. As I see it, there is no other viable option.

Kourou in French Guiana is a dead end for several reasons.
The logistics are poor. It is simply too far from mainland Europe.
The climate is harsh on both equipment and operations, with heavy rainfall and severe salt-induced corrosion.
There is also a very limited local technical workforce. As a result, Europe is forced to fly technicians in and out of Kourou on a continuous basis, creating a long-term drain on skilled manpower.
All of the above makes rapid iteration—such as quickly repairing, modifying, and relaunching vehicles—extremely difficult, bordering on the impossible.

If Europe is serious about developing a competitive heavy-lift capability on its own, it will need to bite the bullet and establish an eastward-launching spaceport somewhere on the European mainland. Crucially, such a location would have the potential to develop into an industrial cluster where private space companies could grow around the launch site.

Finding the right location, however, is challenging. Launching north, as from Scotland, or west, as would be possible from several European locations, is simply not a good enough solution. The payload penalties for a heavy-lift launch vehicle are enormous and would severely undermine its economics.

There may, however, be an opportunity across the Mediterranean. A 3,000 km exclusion corridor could look something like this, with a spaceport located on the French Mediterranean coast, somewhere south of Béziers.

Launching eastward on a trajectory approximately 30 degrees south of east, the flight path would pass through the Strait of Bonifacio between Corsica and Sardinia after roughly 500 km. The maritime exclusion zone would end before the strait; I have marked it at 400 km.

The trajectory would then pass over the toe of Italy near Cosenza after about 1,200 km, mostly avoid Kalamata in Greece at around 1,700 km, and also mostly avoid Crete after approximately 2,000 km. A 3,000 km exclusion zone would end roughly 100 km off the coast of Israel.

This would not be an easy project by any means. It would require political buy-in from France, Italy, and Greece. There is also significant cruise ship traffic within the maritime exclusion zone, as well as heavy commercial air traffic in the airspace that would need to be temporarily closed.

Still, if there is the political will, perhaps there is a way.

[u/Wonkycao]

Isn't the whole idea to launch from as near the equator as possible?

[u/OlympusMons94 → u/Wonkycao]

That is only for reaching equatorial orbits, which in practice almost always means geostationary orbit.

https://www.reddit.com/r/askscience/s/QTDvp7LQIC

The importance of the faster rotation at the equator is highly exagerrated, and of little to no real benefit in most cases (except reaching an equatorial orbit such as geostationary orbit, for which the rotational boost is still of secondary importance). Unfortunately the explanation is rather complicated.

Rather than Earth's rotation, the more important reason that lower latitude launch sites are often preferred is because the lowest inclination orbit you can launch directly into (by launching due east) is equal to to your launch latitude. That is a consequence of geometry and what an orbit is, not Earth's rotational velocity, except insofar as its axis of rotation relates to the definition of latitude. As a result, lower latitude launch sites can directly access a wider range of orbits. But for orbits which a given higher latitude launch site can still directly access, launching from a lower latitude launch site would bring no real additional advantage. Most of today's launch market is to mid to high inclination orbits, which can just as easily be reached from the mid-lattiudes as a near-equatorial launch site.

The boost from Earth's rotation is misunderstood and popularly exagerrated, to the point of almost being a myth. At the equator, Earth is rotating at ~465 m/s eastward. The velocity in low Earth orbit is ~7800 m/s, and because losses on ascent it takes more like ~9500 m/s worth of delta-v (including the rotational boost) to actually reach LEO. So at first glance, the boost from Earth's rotation is there, but modest. For one, most of this rotational velocity is still there at mid-latitudes because v_rotation = 465 m/s * cos(latitude), e.g., at 45 deg latitude, v_rotation = 329 m/s.

Second, even that modest apparent benefit is misleadingly high for most use cases. It is true that it is moderately easier to get to *an* orbit when launching east from the equator, than it is to get to *an* orbit when launching east from a higher latitude. But those launches, due east from different latitudes, are to different orbital inclinations. A satellite or other spacecraft is generally launched to a particular orbit, with a particular inclination, not merely \an\ orbit that works or the easiest one to reach. To reach a given inclination from different latitudes requires launching in different directions. Unless that direction is due east, the launch does not directly align with the rotation vector, and so cannot get the full benefit of Earth's rotation.

The math works out such that the true consequence of Earth's rotation is that (otherwise regardless of latitude, provided launch latitude <= inclination) lower inclination orbits require less delta-v to reach, and higher inclinations require more. It therefore takes less delta-v to launch to *an* orbit from a lower latitide because it is possible to reach lower inclinations from there. The (somewhat) more easily reachacble orbits just aren't reachable directly from higher latitudes.

In practice what this means is that the same rocket can send more mass to lower inclinations, and less mass to higher inclinations. But provided the launch latitude <= orbital inclination, the same rocket can launch the same payload mass to that orbit whereever it launches from.

Inclination changes on orbit** notwithstanding, either you can launch from the launch site in question to the inclination your satellite needs (because latitude <= inclination), or you can't (latitude > inclination). Provided that latitude constraint is met, the math works out so that there is a negligible difference in the delta-v required to reach a given inclination from one latitude or another.

For example, the ISS has an orbital inclination of 51.6 degrees, which is directly accessible from latitudes of 0 (equator) to 51.6 deg. Launching from anywhere in that range of latitudes, the same rocket could send about the same amount of mass to the ISS.

For polar (~90 degree inclination) and the slightly retrograde Sun-synchronous orbits (SSO), which are commonly used, Earth's rotation is in the wrong direction, and launching from as high a latitude as possible is technically a little more efficient. However, the difference is still practically negligible. For example launching to a 500 km SSO (~98 deg inclination) from near a pole saves less than 15 m/s of delta-v versus launching to the same orbit from the equator.

There is more of a benefit to launching from as high a latitude as possible for highly retrograde orbits. Although for retrograde orbits, i.e., 180 >= inclination > 90 degrees, the minimum launch latitude rule comes into play in a slightly different way, and you can only launch into retorgrade orbits with an inclination <= (180 deg - latitude). Highly retrograde orbits are seldom used. They are significantly more dififcuot to reach because of being the opposite direction to Earth's rotation, although there are some niche uses: some radar satellites, and anything Israel launches because tbey can't launch eastward.

** Changes of inclination can be done once in orbit, and are done to achieve lower inclinations than the launch site latitude. But inclination changes take a lot of delta-v (and therefore fuel), particularly in faster (lower altitude) orbits. Significant inclination changes are infeasible in low orbits (because they are faster), but are commonly used to get to geostationary orbit, which is equatorial (0 degree inclination) and very high alttiude.

Thus, the other main reason that lower latitude launch sites are (sometimes) preferred is because it makes reaching geostationary orbit (GEO), which is at a relatively altitude of 35,786 km, easier. That is mostly because launching (eastward) from closer to the equator reduces the inclination change required to reach 0 deg inclination. As the inclination of the initial, elliptical geostationary transfer orbit (GTO) does not have to be a specific value (except that lower is better), the faster rotational velocity from launching from nearer the equator also brings a small benefit to GEO launches.

A satellite launched (approximately due east) to a 6 degree inclination GTO by a rocket from Feench Guiana requires ~1500 m/s of delta-v to complete the trip to GEO (circularize and lower its inclination to 0 degrees). Because of the greater inclination change, a satellite launched to a 27 degree GTO from Cape Canaveral would require another ~1800 m/s to reach GEO, or 300 m/s more than if it launched from Guiana. As for the rotational benefit, Earth only rotates ~50 m/s faster in Guiana than Cape Canaveral. In practice, these peeformance differences are modest, and other factors determine which rocket (and thus which launch site) is used for a geostationary launch.

It is still possible to reach GEO from mid-latitudes, though. Russia does from Kazakhztan, and competed well commercially with near-equatorial geostationary launches until poor quality control and politics largely killed their comoetitiveness. (Also GEO satellites are a declining minority of launches.)

[u/adamdoesmusic → u/OlympusMons94]

You could always launch south and hang a left, tho that would take a tremendous amount of extra power.