A staple of sci-fi space travel may still be a fantasy

in Pol Anderson 1970 novel Zero, a starship crew seeks to travel to Beta Virginis, hoping to colonize a new planet. The ship’s propulsion is “Bassard ramjet,” An actual (albeit hypothetical) way of propulsion proposed by physicists Robert W.Bussard Just ten years ago.Now, physicists have revisited this unusual mechanism of interstellar travel a new paper Published in the journal Acta Astronautica, alas, they found that ramjets were needed. The authors conclude that this is feasible from a purely physical point of view, but the associated engineering challenges are currently insurmountable.

A ramjet is basically a jet engine that “breathes” air. The best simulation of the basic mechanism is that it uses the forward motion of the engine to compress incoming air without the need for a compressor, making ramjets lighter and simpler than turbojets. In 1913, a French inventor named Rene Lorin patented his concept for the ramjet engine (aka flying stovepipe), although he failed to produce a working prototype. Two years later, Albert Fono proposed a ramjet propulsion device to increase the range of artillery projectiles, and was eventually awarded a German patent in 1932.

A basic ramjet engine consists of three components: the air intake, the combustion chamber, and the nozzle. Hot exhaust gas from the combustion of the fuel flows through the nozzles. The pressure of combustion must be higher than the pressure at the nozzle outlet to maintain a steady flow, which ramjets do by “slamming” outside air into the combustion chamber at any vehicle’s forward speed. engine. No need to bring oxygen on board. The downside is that ramjets can only generate thrust when the vehicle is already moving, so they require the use of rocket-assisted takeoff. Therefore, ramjets are most useful as a means of acceleration, for example in ramjet missiles or to increase the range of artillery shells.

Robert Boussard thinks the concept could be modified as a means of interstellar propulsion.The basic premise outlined in His 1960 paper is to use a giant scoop to pick up interstellar protons (ionized hydrogen) magnetic field As a “ram spoon”. The protons will be compressed until they produce thermonuclear fusion, and the magnetic field will then transfer energy into the rocket exhaust to generate thrust. The faster the boat goes, the higher the flow of protons and the greater the thrust.

But then scientists discovered that in regions of space beyond our solar system, hydrogen is much less dense. This is why, In a paper from 1969, John F. Fishback proposed a possible functional magnetic scoop field, taking into account factors such as radiation losses and thermal distribution of the interstellar gas.

In particular, Fishback calculates the cutoff speed.”The faster the spacecraft, the higher the magnetic field lines that focus them into the fusion reactor,” explain the authors of the latest paper. “The stronger the field.[s] cause higher mechanical stress. Fishback concluded that the interstellar ramjet can only continue to accelerate up to a certain threshold speed, at which point it must slow down so that the magnetic source does not reach the breaking point.

Fishback’s solution is studied in this latest paper. “The idea is definitely worth looking into,” Co-author Peter Schattschneider says, One Science fiction Author and physicist at the Vienna University of Technology (TU Wien). “In interstellar space there is highly diluted gas, mostly hydrogen — about one atom per cubic centimeter. If you were to collect hydrogen in front of a spacecraft, like in a magnetic funnel, with the help of a huge magnetic field, you could use it It can run fusion reactors and accelerate spacecraft.”

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