1. Japan's Two Rocket Launch Sites Are Built on the Coast
Japan has two main rocket launch sites: the Tanegashima Space Center and the Uchinoura Space Center, both in Kagoshima Prefecture. JAXA explains that both locations are close to the equator compared to other places in Japan, and have open space to the east. [1]
Across the world, the pattern continues. America’s Cape Canaveral is on the Florida peninsula, facing the Atlantic Ocean. [6] Europe’s Guiana Space Center is on the Atlantic coast of northern South America, with the sea open to the north and east. [8]
However, being near the sea is not the only rule for building a launch site. This article focuses on the two reasons often cited for coastal sites. [1]
2. How Fast the Ground Moves Because Earth Rotates
The Earth rotates from west to east about once every day. At the equator, the ground moves at about 464 meters per second. Near Tanegashima, the ground moves at about 400 meters per second. [1][2]
If you convert this to kilometers per hour, 400 meters per second is about 1,440 kilometers per hour (about 895 miles per hour). Because the ground moves in the same direction all the time, we do not feel this speed while standing on it. [2]
The speed changes depending on where you are. The closer you are to the equator, the larger the circle the Earth makes in one day, so the ground moves faster. Near the poles, the circle is smaller, so the speed is slower. The Guiana Space Center is closer to the equator than Japanese launch sites. ESA explains that the Earth’s rotation adds about 460 meters per second to the rocket’s speed there. [7]
3. Why Launching Toward the East Gives a Rocket Extra Speed
Imagine throwing a ball forward while riding on a moving train. To someone standing outside, the ball’s speed is the speed of the train plus the speed of your throw. When a rocket launches east, the ground is already moving east. From the center of the Earth, the rocket inherits this speed. [2]
However, the rocket still needs its own engine to go to space. The Earth’s rotation just helps with part of the speed. If you launched west, you would have to subtract the Earth’s speed. JAXA lists this difference as a reason why there are many eastward launches. [1]
Not every launch goes east. Satellites that observe the Earth from above the poles sometimes launch south. JAXA explains this exception. Eastward launches apply to many, but not all, rockets. [2]
4. Why Launch Sites Are Placed Far from Cities
JAXA’s Human Spaceflight Technology Department explains that launch sites are chosen in remote areas, away from cities. This is to consider the danger of explosions, falling debris, and loud noise. Examples include Uchinoura and Tanegashima in Japan, Kennedy Space Center in the USA, and the Guiana Space Center in Europe. [3]
JAXA lists specific conditions for choosing Tanegashima and Uchinoura: there are no regular flight paths or shipping lanes in the launch direction, large areas of land can be secured easily, and there are no houses around the launch site. [1]
If the east side is the sea, these conditions are easier to meet. However, Uchinoura is said to use mountain terrain, so "flat land" is not the only requirement. [9]
Safety Note: Launch sites are placed in remote areas away from cities to manage explosion risks, falling debris, and noise. JAXA lists conditions for Tanegashima and Uchinoura: no regular air or sea routes in the launch direction, enough space for the site, and no homes nearby. [1]
5. How Rockets Are Tracked from the Ground During Flight
At the Tanegashima Space Center, the position and speed of the rocket are sent to the ground during flight. If the rocket goes far off its planned course, there is a system to stop the flight by command to minimize damage. [4]
If the launch direction is over the sea, the place where parts might fall is likely to be empty water. However, safety is not just about the sea. It relies on a combination of tracking and the ability to stop the flight if something goes wrong. [4]
Safety Note: It is not safe just because it is over the sea. Safety comes from launching in a direction where parts fall into the sea, tracking the rocket, and stopping it if it goes off course. [4]
6. How the Sea Near a Launch Site Is Monitored and Kept Clear
According to JAXA’s H3 rocket launch plan, the sea area is monitored. JAXA uses monitoring radars to watch the area and sends out patrol ships to keep watch. [5]
Safety Note: The sea is not "just empty." Safety is maintained through active monitoring and patrol ships during launches. [5]
7. Cape Canaveral and Other Launch Sites Follow the Same Ideas
NASA explains that Cape Canaveral was chosen in 1949 as a place for long-distance tests. The reasons were that the population was low, a former naval base was nearby, and there was a long distance over the Atlantic Ocean. [6]
France needed to move its launch site after Algeria became independent in 1962. They chose Guiana in 1964. [8] It is at latitude 5 degrees 3 minutes north, just north of the equator. ESA notes that the Earth’s rotation adds about 460 meters per second to the rocket there. ESA also says the population is low and 90% of the land is equatorial forest. [7]
In Japan, the Uchinoura Space Center launched the first Japanese artificial satellite, "Osumi," in 1970. Japan is the fourth country in the world to launch a satellite with its own rocket. [9]
8. How to Check Launch Site Locations on a Map or Globe
Try looking at a school atlas or a globe. Find Tanegashima, Uchinoura, Cape Canaveral, and Guiana. Compare what is to the east of each place and how far they are from the equator. You will see the two reasons from this article on the map. [1]
If you want to learn more, read the question pages on JAXA’s "Fun! Fun! JAXA!" website. [1][2] Launch schedules and visit information can be checked on official JAXA announcements.
Safety Note: Safety explanations can be read on JAXA’s Human Spaceflight Technology Department question page and the Tanegashima launch-related pages. [3][4]