Observations on Siting an Accelerator

G. Flanagan

Alna Space Program

June 14, 2011

Introduction

In many articles about rail or gun launch devices, there is an assumption that mountains could be used to achieve a convenient launch angle and to get above the majority of the atmosphere. Using Google Earth, I explored some of the possibilities just to get an idea of the challenges. One assumption in this explorations was that the accelerator was 10 km long, giving an acceleration on the order of 500 g’s. Another assumption was to assume a near-equator site. I am assuming that the majority of the payload mass needs to go into a near equatorial orbit.  At whatever latitude chosen, the accelerator needs to be align along a great-circle path.

An accelerator needs to be perfectly straight, or at least have a very shallow curvature. This presents a problem with siting on a mountain. In order to get a straight line, one must either drill a tunnel through some sections, or build an elevated structure. Both are possible, and the issue become a matter of degree for cost considerations.

Other considerations for siting include: Access to land or air transportation, overflight concerns, and noise. Also, a high mass throughput corresponds to a large power requirement.

In most studies, it is assumed that the gun will require an exit angle of at least 10° in order for the projectile to pass rapidly through the atmosphere. My trajectory studies have shown that as an alternative one can have a horizontal gun by providing the projectile with aerodynamic lift. The lift can change the trajectory path sufficiently to have the same affect of limiting the time in the atmosphere. This approach greatly opens up the possibilities for siting an accelerator.

Mountains near the equator

The mountains of Ecuador would appear to be good locations for a space gun. There are several peaks above 5000 m that are located very close to the equator.

Nevado Cayembe

Nevado Cayembe has a 5790 m peak. The red line below shows a possible 10 km path. The red line follows the ground contour, so the problem is to straighten the path. The profile shows that one could have a reasonable straight 5 km path starting from the peak down, but then one would have to start drilling a tunnel to get the remaining 5 km. The terrain appears to be rough and difficult for any major civil engineering project.

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Carihuairazo, Elevation 5018 m

Carihuairazo was interesting because the approach to the peak did appear to be as irregular. On the downside, the angle of the path is only about 4°. Carihuairazo is a volcanic caldera which may discourage the construction of an expensive civil engineering project.

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Plateau  sites

If the system uses projectile lift instead of a fixed gun angle, then there are several possibilities for siting at high altitude. The problem is that the high plateaus near the equator involve flying over land and possibly populated areas.

There is a high (2500 m) region of Kenya. The image below arbitrarily picks on 10 km path in this region. Zooming in further, the plateau appears to be heavily cultivated.

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Mexico

If we look a bit away from the equator, Mexico has some higher regions around 22N latitude. The path below is near Ojuelos de Jali. It was picked to be away from obvious cultivated land and towns.

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Note that exit is at left side of profile plot.

Similarly, Peru has large expanses of level terrain at over 4000m. The path shown below is at latitude 14S. This site appears to be rather remote, and would require a lot construction to build the necessary transportation and power infrastructure.

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Edge of Ocean Site

If the system can be horizontal, and at sea-level, then the overflight problem can be solved by placing the gun along either level terrain at an eastern coast, or in shallow water. Below is a 50 km path of the coast of French Guiana. Guiana already has a conventional space launch facility (Centre Spatial Guyanais). Supplying the base from the ocean is also appealing. Trajectory studies demonstrate that sea-level, horizontal launch is feasible.

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Deep Water

Quicklaunch proposes to build a 1.1km long gun that operates in the ocean. By sinking one end of the structure, a favorable angle is achieved.  

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Spikey Created with Wolfram Mathematica 8.0