The Buzzard Ramjet

As I pointed out in a previous post, the stars are very far away. Astronomers use light-years as a unit of measurement of the distance between stars. Since light travels at 186,000 miles per second, a light-year is 586, 569, 600, 000 miles. The nearest star is around four light years away, 2, 346, 278, 400, 000 miles. The fastest current spacecraft can travel at 158, 000 mph. It would take over 1600 years for it to reach the nearest star. Does such distances mean that spacecraft human or robotic will never launched to another star system? It does seem daunting. But technologies have been proposed which might make such a trip possible.

In 1960, Robert Bussard, a physicist suggested a spacecraft designed as shown in the illustration. The way that it would work is that the scoop in the front takes in hydrogen which is fed to a nuclear fusion reactor to supply a high-speed exhaust. In this manner the vehicle would avoid having to carry a large amount of fuel which would add to its mass. A typical region of interstellar space contains about one atom per centimeter.

The Buzzard Ramjet as it is called has major problems as far as implementation with our present technology. One is that the scoop would need a frontal collecting area of 10,000 square kilometers. A 10, 000 km² scoop made of the thinnest Mylar would weigh 250, 000 tons. One way around this problem is to ionize the hydrogen ahead of the spacecraft using a powerful laser, allowing a relatively small collector which generates a powerful magnet. In this manner the scoop could be mesh. However, there are additional problems. For additional details, see David Darlings Interstellar Encyclopedia. It also suggests possible solutions.

Another web site with good explanation of the Buzzard ramjet is Nation Master Encyclopedia. In this article is says that spacecraft accelerating at 10 m/sec² could reach 77% of light speed in one year. Once it reached that speed, propulsion would no longer be need until it approached its destination, at which time it would need to decelerate.